THE NUCLEAR POWER DECEPTION
U.S. Nuclear Mythology from Electricity "Too Cheap to Meter"to "Inherently Safe" Reactors (all web-posted selections -- long file)
by
Arjun Makhijani, Ph.D.
and
Scott Saleska
April, 1996
by
Arjun Makhijani, Ph.D.
and
Scott Saleska
April, 1996
In recent years there has been a debate about the potential and need for developing a second generation of commercial nuclear power plants to generate electricity. Proponents of such development cite a range of reasons for undertaking it, primary among them the growing environmental problems (most notably the threat of global climate change) associated with conventional fossil-based electric power generation and the need to reduce the dependence of the United States on imported oil.
At the same time, a related debate is taking place about U.S. proposals to build one or more reactors for military-related purposes. The stated reasons for building new reactors have varied, ranging from new plutonium and tritium production reactors in the late 1980s and early 1990s to reactors for burning excess military plutonium to a "triple play" reactor that would simultaneously burn excess plutonium, produce tritium (a radioactive gas used in nuclear warheads) and generate electricity. During the 1990s, a new element has been added to these debates -- that of using new reactors to burn Russian excess weapons plutonium.
At times the two debates have converged, but not primarily for technical reasons. When political pressures to spend more money on reactors have been stronger, technical considerations have tended to take a back seat. When fiscal concerns have the upper hand, funds for military enterprises that would subsidize civilian power projects tend to be reduced or eliminated.
Before accepting arguments that nuclear power can alleviate the build up of greenhouse gases or that joining military to civilian nuclear ventures is desirable, we need to learn what history might have to offer by the way of lessons. In particular, the idea of new reactors that would join military and civilian goals parallels the development of the first generation of power reactors in the United States. This study critically examines the history of wildly optimistic public statements that were made about nuclear power in the years and decades immediately following World War II and serves as a partial guide to dealing with critical civilian and military nuclear issues today. So far as we are aware, the technical foundation of those extravagant promises has never been carefully scrutinized until now.
In 1954, Lewis Strauss, Chairman of the U.S. Atomic Energy Commission, proclaimed that the development of nuclear energy would herald a new age. "It is not too much to expect that our children will enjoy in their homes electrical energy too cheap to meter," he declared to a science writers' convention. (1) The speech gave the nuclear power industry a memorable phrase to be identified with, but also it saddled it with a promise that was essentially impossible to fulfill.
In contrast to the rosy propaganda and promises, commercial nuclear power from new nuclear plants has become the most expensive form of commonly used baseload electric power in the United States. In part, this was because utilities canceled 121 reactors in the post-1974 period; the money squandered on these canceled plants alone was about $44.4 billion in 1990 dollars, (2) or about $50 billion in 1995 dollars. Even larger costs were incurred, in the form of higher electricity costs for instance, because of the very high costs of plants completed in the 1980s. Enjoying virtually every conceivable advantage at its birth -- from high public popularity to lavish government funding to virtually unanimous political support -- the commercial nuclear power industry in the United States is a moribund one, with virtually every one of its early advantages reversed.
Part I of this study contains an introduction to the technical issues and then provides an historical analysis of nuclear power in the United States. In particular, it looks closely at the early claims that nuclear electricity would be "too cheap to meter" and whether they were, at the time, actually believed by the nuclear power proponents.
Part II, drawing on the historical analysis, provides a critical appraisal of current plans for a second generation of nuclear plants partially subsidized by military materials production activities for nuclear weapons. It also reviews the persistent dangers in light of the Chernobyl accident and proliferation and environmental issues arising from the huge and growing stockpiles of weapons-usable plutonium in reactor spent fuel. This is followed by a chapter outlining an approach to creating an environmentally sound, reliable electricity system. There are also three appendixes: Appendix A on the basics of nuclear physics and fission, Appendix B on uranium, and Appendix C on plutonium. A summary and recommendations chapter is provided at the start of this report.
A note about sources: We have used original documents and sources for much of the material. Where the book covers ground that has already been covered by others, we have also used published books and materials as cited in these works. We have also used official historical accounts of the development of nuclear energy and of the history of the Atomic Energy Commission. For basic nuclear engineering information, we have used the textbooks, Introduction to Nuclear Engineering by John R. Lamarsh and Nuclear Chemical Engineering by Manson Benedict, Thomas H. Pigford, and Hans Wolfgang Levi. Unless otherwise stated, statistics on electricity costs, energy supply, and energy use are derived from the Historical Statistics of United States from Colonial Times to 1970 and from various issues of the Statistical Abstract of the United States. Units are metric, unless otherwise noted. We have referred to literature produced by the Nuclear Regulatory Commission, generally abbreviated as NRC, as well as the National Research Council of the National Academy of Sciences, also generally abbreviated as NRC. In order to avoid confusion between these acronyms, we used the acronym NRC-NAS for the latter, and the acronym NAS to refer to studies by the NAS committees.
Arjun Makhijani
Takoma Park
April 1996
One likely reason for the failure to pursue the answers even when the questions were asked is that power and money lay in the direction of development of these technologies, while the common good lay in the answers to the questions about damage to the Earth's ecosystems and to global security. But if we do not answer such questions, then it is possible that wide-ranging, potentially irreversible effects will damage the common good now and for uncountable generations into the future, even as individuals derive transient benefits from the technologies. This study examines nuclear power technology with such questions in mind.
A. Main Findings
1. There was no scientific or engineering foundation for the claims made in the 1940s and 1950s that nuclear power would be so cheap that it would lead the way to a world of unprecedented material abundance. On the contrary, official studies of the time were pessimistic about the economic viability of nuclear power, in stark contrast to many official public statements.
Unduly optimistic official public pronouncements regarding the promise of nuclear energy are epitomized by AEC Chairman Lewis Strauss's forecast for an atomic age of peace and plenty in a 1954 speech, in which he also made his well-remembered remark:
It is not too much to expect that our children
will enjoy in their homes electrical energy too cheap to meter....(3)
Our review of technical studies on nuclear power prepared in the 1940s and 1950s by a variety of government and industry sources, including the Atomic Energy Commission, revealed no evaluation of nuclear energy that concluded that nuclear energy would be cheap in the near future. On the contrary, many studies concluded that nuclear power would be more expensive than coal-fired electric generating stations and that it would have to be subsidized by military plutonium production in order to be economically viable. Other studies concluded that nuclear electricity might one day be competitive with coal, especially if coal prices rose and nuclear fuel were cheap.
A 1948 AEC report to Congress cautioned against "unwarranted optimism" about nuclear power because there were many "technical difficulties" facing it that would require time to overcome. (4) The report's authors included many of the leading nuclear scientists of the time, including Enrico Fermi, Glenn Seaborg, and J.R. Oppenheimer. As another example, an industry report done by four industry-utility groups, including Bechtel, Monsanto, Dow Chemical, Pacific Gas and Electric, Detroit Edison, and Commonwealth Edison, concluded in 1953 that "no reactor could be constructed in the very near future which would be economic on the basis of power generation alone." (5) Ward Davidson, a research engineer with Consolidated Edison, one of the country's largest utilities, laid out in 1950 the technical difficulties facing practical nuclear power in considerable detail, including problems such as making durable materials of assured quality that could survive the intense neutron bombardment in nuclear reactors. Insiders even scorned those who might suggest that nuclear energy would usher in an era of plenty, as noted by C.G. Suits, a General Electric Vice-President, in December 1950:
It is safe to say...that atomic power is not the means by which man will for the first time emancipate himself economically....Loud guffaws could be heard from some of the laboratories working on this problem if anyone should in an unfortunate moment refer to the atom as the means for throwing off man's mantle of toil. It is certainly not that!...This is expensive power, not cheap power as the public has been led to believe. (6)
2. Cold War propaganda rather than economic reasoning was a driving force behind the rush to build a commercial nuclear power plant in the United States.
Coal was plentiful in the United States, then as now. Further, there were no serious pressures in the 1950s to reduce its use due to the build-up of greenhouse gases. There was therefore no urgent reason then to press ahead with building large nuclear power plants.
Despite the pessimism of governmental as well as corporate studies about its economics, nuclear electricity was seen by many in government as a key technology to be exploited in the Cold War with the Soviet Union. Atomic Energy Commissioner Thomas Murray said in 1953 that peaceful applications of the power of the atom "increases the propaganda capital" of the U.S. relative to the Soviet Union. (7)
The Chairman of the Congressional Joint Committee on Atomic Energy warned in 1953 that "the relations of the United States with every other country in world could be seriously damaged if Russia were to build an atomic power station for peacetime use ahead of us. The possibility that Russia might demonstrate her 'peaceful' intentions in the field of atomic energy while we are still concentrating on atomic weapons, could be a major blow to our position in the world." (8) President Eisenhower's 1953 "Atoms for Peace" speech was perhaps the centerpiece of the U.S. effort to cast its nuclear program in a peaceful light for the purposes of Cold War propaganda.
The choice of the light water reactor (LWR) as the first commercial reactor was influenced by these Cold War considerations. H.C. Ott of the AEC's division of reactor development objected to the selection of the pressurized water reactor (PWR) in 1953 because the choice had not been justified "as a logical part of the over-all reactor development program and no arguments are advanced to support the thesis that a prototype power plant should be built." (9) But a classified 1954 AEC report concluded that the PWR had the best short-term prospects. However, the design was considered a poor long-term choice because it was (erroneously) thought at the time that the scarcity of uranium would make reactors like PWRs uneconomical because they were net consumers of fissile material. The actual vulnerabilities turned out to be not uranium-235 scarcity, but safety, capital cost, and proliferation.
Solar energy was not pursued seriously despite a 1952 report of a presidential commission (the Paley Commission) that anticipated oil shortages in the 1970s. The report was relatively pessimistic about nuclear energy and called for "aggressive research in the whole field of solar energy -- an effort in which the United States could make an immense contribution to the welfare of the world." (10) This advice was ignored. Solar energy research and development could not provide the Cold War "propaganda capital" that nuclear power gave to the U.S.
3. The AEC overruled some of its own personnel and the official Advisory Committee on Reactor Safeguards (ACRS) in its rush to build large scale power plants that would feed electricity into utility grids.
The dangers of nuclear power plants were well enough understood in the 1950s that there were many voices advising against a rush to build large scale plants. As early as the mid-1950s, the ACRS advised the AEC to proceed more slowly and cautiously with its licensing of a sodium-cooled breeder reactor, Fermi I, near Detroit. Autoworkers' unions went all the way to the Supreme Court to try to block its construction, but they failed. A pilot plant of similar design, the Experimental Breeder Reactor I built in Idaho, had had an accident in 1955 during a safety experiment. The voices of caution did not prevail. The Fermi I reactor was started up in 1963, but had not yet achieved full power when it suffered a partial meltdown due to a partial cooling system blockage in 1966.
The ACRS also had concerns regarding unresolved issues surrounding a potential meltdown of the core of light water reactors (LWRs) in case of a loss-of-coolant accident. Its concerns received heightened attention only after protracted hearings in the early 1970s on the issue in which independent scientists, notably from the Union of Concerned Scientists, and whistleblowers played central roles.
Finally, in 1957, an official study by Brookhaven National Laboratory concluded that up to 3,400 people could die and up to 43,000 people could be injured in case of a severe accident in a 500 megawatt-thermal (100 to 200 megawatt-electrical) nuclear power plant. Property damage alone was estimated at up to $7 billion in 1957 dollars (about $38 billion in 1995 dollars). Many power reactor safety studies and experiments were begun in the 1950s, but they were not completed before commercial reactors started being built in large numbers. Instead the government provided industry with a huge subsidy in the form of the Price-Anderson Act, which limited their liability to $500 million above "private insurance." Self-insurance was permitted as a form of private insurance under the Act. The total compensation was therefore considerably less than 10 percent of the estimate in WASH-740 of property damage alone.
The potentially catastrophic nature of nuclear accidents was made painfully graphic by the Chernobyl accident. The amount of damage from a catastrophic accident on the scale of Chernobyl vastly exceeds the $7 billion insurance provision in the 1988 amendment to the Price-Anderson Act.
4. Every major reactor design that was adopted had and continues to have crucial unresolved safety vulnerabilities as a result of the rush of the nuclear weapons states to deploy nuclear power plants well before the technology had been properly investigated and developed.
The three major reactor designs of the 1950s were:
The basic safety flaws of these designs were identified in the 1950s and 1960s. Yet, nuclear establishments (governmental and private) persisted with these designs because they had already made heavy investments in them. One initial AEC response to safety problems as they were revealed was to try to suppress discussion. But in the United States, where the public's right to know is greater than in any other major nuclear state, many safety issues did become public. The official response in such cases was to try to deal with safety issues in an ad hoc and dilatory manner. When that route became too cumbersome and bred lawsuits, the AEC held a rule-making hearing on the most important kind of accident identified for LWRs -- the loss-of-coolant accident. The hearings revealed serious problems, official attempts to cover them up, and safety issues that had not yet been satisfactorily resolved. All this resulted in a loss of public confidence and higher costs in the long-run due to retroactive safety requirements that were needed.
Basic safety issues have not been resolved in that the potential for catastrophic accidents remains. For instance, then-NRC Commissioner James Asselstine, noted in 1986 that "given the present level of safety being achieved by the operating nuclear powerplants in this country, we can expect to see a core meltdown accident within the next 20 years, and it is possible that such an accident could result in off-site releases of radiation which are as large as, or larger than, the releases estimated to have occurred at Chernobyl." (11)
Newer versions of the light water reactors in the United States and elsewhere have not eliminated the danger arising from a loss-of-coolant accident. Similarly, safety vulnerabilities continue to exist in other reactor designs that are being advertised as "inherently safe," such as a gas-cooled, graphite moderated reactor. This is a public relations phrase that applies to avoiding or minimizing risks from particular types of accidents, notably loss-of-coolant accidents. Other accidents types, also potentially catastrophic, may occur with such designs.
There is an even greater danger of a severe accident in the former Soviet Union, due to relatively less safe designs (including lack of secondary containment) and poorer maintenance due to the economic collapse that has taken place at the end of the 1980s. According to Michael Golay, a professor in the nuclear engineering department of the Massachusetts Institute of Technology, there is "a very high likelihood of a serious reactor accident in the near future" in the former Soviet Union and Eastern Europe due to the relatively unsafe reactor designs, poor reactor system construction materials, and other factors, such as low spending on maintenance. (12)
5. Nuclear power became established in the market place at a low price in the 1960s as a result of government subsidies, lack of adequate attention to safety systems, and an early decision by manufacturers to take heavy losses on initial orders. Costs increased when these advantages were reduced.
Direct government subsidies helped finance reactors until 1962. After that G.E. and Westinghouse decided to market LWR technology at a loss because they feared it would otherwise become obsolete.
A General Electric vice-president later stated that "If we couldn't get orders out of the utility industry, with every tick of the clock it became progressively more likely that some competing technology would be developed that would supersede the economic viability of our own. Our people understood this was a game of massive stakes and that if we didn't force the utility industry to put those stations on line, we'd end up with nothing." (13)
About 45 percent of the entire eventual installed nuclear capacity of about 100,000 MWe in the United States was ordered in the four-year period between 1963 and 1967. There was a rush of reactor orders and nuclear power plant completions. The power plants were built with government-subsidized insurance and without practical assurance that critical safety systems would work.
Several factors led to nuclear power costs increasing rapidly in the 1970s and early 1980s:
As a result of these factors, nuclear power costs rose very rapidly. At the same time electricity growth rates declined. As the 1980s wore on, nuclear power plant operating, maintenance, and fuel costs rose to above those for coal-fired plants, as did estimates for reactor decommissioning. As a result, the loss of public confidence in nuclear power spread from Main Street to Wall Street. The disillusionment was the result of promises on cost that could not be fulfilled, a poor approach to safety that ignored or downplayed early warnings, and attempted cover-ups of safety issues that were later exposed. The Three Mile Island accident was the perhaps the knock-out punch on safety issues. While the releases of radioactivity were not high (relative to other severe nuclear accidents), it showed that core meltdown accidents could happen and that accident probabilities may not be as low as had been supposed. Public disillusionment with nuclear power was reinforced by a corresponding loss of trust on nuclear weapons-related environmental mismanagement and misrepresentations.
6. The non-proliferation issues related to nuclear power, and in particular their relation to the arsenals of the existing nuclear weapons states, have never been satisfactorily resolved.
Nuclear power is vulnerable to forces of social instability and violence, which are becoming more technologically sophisticated while crucial institutional mechanisms for holding them in check remain weak. Examples range from the bombing in Oklahoma City to the gas attack on the Tokyo subway to threats of radioactive warfare made by Chechen rebels.
A second proliferation vulnerability of nuclear power is the vast amount of plutonium created in nuclear power plants. Every four years or so commercial nuclear power reactors create an amount of plutonium equal to that in the global military stockpile. This plutonium is not usable for weapons unless the spent reactor fuel is reprocessed (that is, unless the plutonium is separated from fission products and residual uranium). A large amount of plutonium has already been separated. Commercial reprocessing plants are operating in France, Britain, Japan, Russia, and India. Proposals exist for reproecessing U.S. spent fuel more (see below).
7. Management of spent nuclear fuel has become a central concern regarding nuclear power growth.
The problem of high level nuclear waste has not been resolved anywhere in the world, after four decades of nuclear electricity generation. The early confidence that nuclear scientists would somehow solve the waste problem, just as they had built the atom bomb, has evaporated
In the United States, sound science has been overtaken by political considerations in the rush to relieve utilities of the liabilities deriving from the spent fuel accumulating at reactor sites. The Yucca Mountain site is the only one under investigation. Yet calculations done for this site, including those by Department of Energy contractors, indicate that radiation doses could be hundreds or even thousands of times above presently allowable limits. There is pressure to relax standards and change calculation methods instead of improving the repository program.
8. Reprocessing, which is the separation of plutonium and uranium from used reactor fuel is a costly, dangerous, and proliferation-prone technology. Yet political pressure is building to reprocess spent fuel as a waste management method.
Reprocessing is very costly. The overall costs of this approach to spent fuel management and disposal would range from roughly $130 billion for government-subsidized reprocessing to $250 billion for commercial reprocessing in which the customer pays the full costs. This translates into half-a-cent to one cent per kilowatt hour of nuclear electricity -- five to ten times more than the contribution of 0.1 cent per kilowatt hour (electrical) that nuclear utilities are now required to make by law into a nuclear waste fund. This presumes commercial reprocessing in a new reprocessing plant in the United States.
The safety and environmental consequences of using existing U.S. military reprocessing plants, which are over 40 years old, are incalculable. As a result the costs are also highly uncertain. Reprocessing in existing military plants would greatly exacerbate high-level waste management problems, already beset by risks of fires and explosions.
Commercial reprocessing in France, Britain, Japan, Russia, and India is now the most important contributor by far to the growth of nuclear weapons-usable plutonium in the world. As the only nuclear weapons state not reprocessing for military or commercial reasons, the U.S. is the one country with the political standing to persuade Russia and other countries to stop commercial reprocessing. Reprocessing U.S. commercial spent fuel in the United States (or abroad) would be a grave practical setback to the implementation of the U.S. non-proliferation policy of discouraging reprocessing and the growth of weapons-usable materials stocks.
Yet, the political pressure from the U.S. nuclear power industry is causing proposals for reprocessing this commercial spent fuel to reemerge in a way not seen since the early days of the Reagan administration. One such proposal was put forward by Westinghouse in an August 1995 study done for the DOE. This is a dangerous trend. It is difficult to overemphasize the central importance of U.S. policy against commercial reprocessing.
9. The problem of what to do with the surplus plutonium in U.S. and Russian military stockpiles is exacerbating a growing commercial plutonium surplus.
Proposals have been put forward to convert plutonium into mixed uranium-plutonium oxide fuel (called MOX fuel) in order to use it in existing commercial reactors or in new reactors. Such use would create a new commercial-military link that seems in many ways like a replay of the earlier debates on dual-use reactors. However, this time around, the civilian reactors are proposed to be used to partially destroy (or "burn") rather than create military plutonium. Such a connection would be undesirable for a number of reasons, not least of which are the proliferation implications of establishing a plutonium fuel economy in the United States.
10. Nuclear power plants cannot simultaneously meet stringent safety criteria that would rule out catastrophic Chernobyl-like accidents and also contribute significanty to the reduction of greenhouse gas emissions in a timely manner.
In order to ensure that nuclear reactors are not vulnerable to catastrophic accidents, new designs would need to be developed. These designs would have to be thoroughly checked on paper and in experimental and pilot-scale reactors before relatively large plants were built. Such an effort to ensure reactor safety and regain public confidence would take decades, if it can be accomplished at all. However, carbon dioxide emissions must be reduced in the same period. The next few decades will be crucial in the effort to minimize the threat of disastrous adverse effects due to the build-up of greenhouse gases. As a result, nuclear power plants cannot simultaneously meet stringent safety criteria that would rule out catastrophic Chernobyl-like accidents and also contribute significantly to alleviating the greenhouse gas build up.
11. It is possible to simultaneously phase out nuclear power plants and reduce carbon dioxide emissions from fossil fuel burning.
The low efficiency of primary fuel use even in technologically advanced countries and the even lower efficiencies in the rest of the world means that much or most of the increased energy needs of the world's people can be met by improving efficiency dramatically. Renewable energy sources and judicious use of natural gas technologies can displace both nuclear power plants and help reduce the use of oil and coal in electricity generation. Technologies for greatly increasing energy efficiency as well as for using renewable energy sources are available now. Many others are nearly commercial. Institutional and market failures as well as the lack of proper government procurement policies and regulations are systematically hindering the widespread use of these technologies.
B. Recommendations
The central recommendation of this study is that nuclear power should be phased out. Specifically:
Other Recommendations
The policies needed to restructure the existing waste management program are discussed in our earlier book on nuclear waste, High-Level Dollars, Low-Level Sense. We merely summarize those recommendations and update them here:
"...you had uranium in the rocks, in principle, an inexhaustible source of energy -- enough to keep you going for hundreds of millions of years. I got very, very excited about that, because here was an embodiment of a way to save mankind. I guess I acquired a little bit of the same spirit as the Ayatollah has at the moment."--Alvin Weinberg, former head of the Oak Ridge National Laboratory and nuclear reactor designer, 198115
I am sure we are agreed that the ultimate survival of America is dependent on intellectual vigor and on spiritual deeprooting -- not on specific devices which are always for the moment. The atom has no ethics of its own any more than it has politics. The future of the scientists' America, and yours and mine, lies fundamentally with education -- that which is taught to the young in our schools -- that which is taught throughout life in the media of general communication by the contemporary writers. Fundamental are respect and zeal for scholarship, a lively regard for moral values, and a love of truth. And of these the last is, of course, the greatest.
--Lewis Strauss, AEC Chairman, 195416
All forms of transportation will be freed at once from the limits now put upon them by the weight of present fuels....Instead of filling the gasoline tank of your automobile two or three times a week, you will travel for a year on a pellet of atomic energy the size of a vitamin pill ... The day is gone when nations will fight for oil....
The world will go permanently off the gold standard once the era of Atomic Energy is in full swing ... With the aid of atomic energy the scientists will be able to build a factory to manufacture gold.
No baseball game will be called off on account of rain in the Era of Atomic Energy. No airplane will by-pass an airport because of fog. No city will experience a winter traffic jam because of snow. Summer resorts will be able to guarantee the weather and artificial suns will make it as easy to grow corn and potatoes indoors as on a farm.
--David Dietz, Science writer, 194517
The control of fire was central to the development of cities -- that is, of civilization. Its use on a large scale directly and indirectly, through diverse carriers of energy such as steam, is the foundation of modern industry and commerce. In the eighteenth and nineteenth centuries, steam power enabled the centralization of manufacture by the use of mechanized transport to draw huge quantities of raw materials, such as cotton and jute, as well as food from around the globe into the world's new manufacturing centers in Europe. The first fuel to be used on a large scale for industry and transport was coal; it continues to occupy a large place in the world's energy supplies today. In the late nineteenth century it was joined by petroleum; in the twentieth natural gas was added to the fossil fuel mix.
The potential for the application of energy to transform life for vast numbers of people was demonstrated in the second part of the nineteenth and first half of the twentieth centuries in a number of radical and graphic ways. Electric lights illuminated the night. Rapid travel over large distances became commonplace, first via railroad and steamships and then also via trolleys, buses, and cars. This mechanized mobility was symbolized by Phileas Fogg, Jules Verne's nineteenth century fictional voyager, who went around the world in eighty days and returned home punctually. Farm mechanization reduced the need for farm labor; cities grew; occupations and specializations multiplied.
In the cities, automobiles and street cars rapidly replaced horse drawn carriages. And the domestic scene was transformed, for those who could afford it, by central heating and numerous appliances that reduced the burdens of physical labor. The possibility that life for ordinary people around the world could one day be very comfortable, even luxurious, was no longer theoretical -- it was being practically realized everyday by large numbers of people of European origin and also by a small minority in the colonized countries. The prospect that such a life would be available to all seemed to depend on nothing more than human ingenuity in the application of science and technology and on the availability of sufficient natural resources, chief among which were fuels.
But these historic changes also carried the seeds of misery and destruction. Consolidation of farms threw people off the land. Machines threw people out of work. In many of the countries that were colonies of Europe, the destruction of cottage industries actually reduced the proportion of people working in non-agricultural occupations. At the same time, there was little work to be had on the land. From time to time, as in the 1930s in the United States, there were vast and sudden displacements of people from farms to urban areas, accelerating trends started by industrialization. Indigenous cultures, whose knowledge of the natural environment is, in many ways, still unparalleled by science were destroyed around the world. Unemployment became a permanent feature of the world economy.
Despoilation of the environment was occurring on a scale as grand as the huge industries that were springing up. Air pollution was, in many places, literally breathtaking. For instance, in London the air often got so bad that episodes of smog came to be called "peasoupers" after their resemblance to pea soup: visibility was typically reduced to a few yards. Thousands of people died of respiratory diseases as a result of the London "peasouper" of 1952. The public outcry accompanying the deaths and suffering led to the initiation of unprecedented pollution control regulations in Britain. The general recognition of potential damage to the entire atmosphere due to a build up of carbon dioxide from fossil fuel burning was still about three decades away, however. (18)
As the exploitation of resources and the trade in them became global, so did the wars for their control. To a considerable extent, these global wars had their roots in the dependence of western economies on cheap imported primary commodities and in the competition between them for these resources. After World War I, oil rapidly became the most crucial strategic primary commodity. Much of the prelude to World War II, including the Japanese bombing of Pearl Harbor, many of battles during that war, and much of the wartime strategy of the antagonists revolved around the control of oil resources that had become the lifeblood of the war machine. (19)
By the middle of the twentieth century, with the colonies in Asia and Africa on the verge of political independence, people throughout the world were seeking to achieve the level of material standards of living that had already become a reality for a substantial minority of people in western Europe and the United States and would soon be realized by a majority. But would there be enough resources for all, given the already high and rising levels of consumption in Europe and the United States and the dependence of western economies on imported primary commodities, especially oil?
Einstein's discovery early in the twentieth century that matter and energy were equivalent, expressed by the famous equation E = mc2, came in the middle of this immense and unprecedented technological, political, economic, and military ferment. H.G. Wells, in The War of the Worlds, wrote about bombs that might destroy cities and entire civilizations. But there were also visions of unlimited amounts of energy for everyday life. Einstein's equation showed that a small amount of matter was theoretically equivalent to a huge amount of energy: just one gram of matter, if completely converted to energy, was equivalent to roughly 3,000 metric tons of coal. (20)
If only some way could be found to change matter into energy, the days of deprivation would be over! The Pharaohs needed slaves to do their bidding. Modern life would not need to be cruel to be affluent. Small bits of dead matter could take the place of slaves and everybody could be happy ever after -- at least so far as material matters were concerned. Life would be free of drudgery. Convenience and creativity would flourish in the ample leisure time that everyone would enjoy.
In the late 1930s, the fission of uranium -- that is, the splitting apart of its nucleus into smaller nuclei of light elements -- was discovered and the possibility of converting matter into energy on a large scale started to move from the realm of science fiction and improbable theory to reality
The practical harnessing of fission energy required the splitting of a large number of uranium atoms -- in a controlled sustained way for nuclear power production, or all at once for a bomb. The Hungarian scientist Leo Szilard had realized well before fission was discovered in the laboratory in 1938 that a nuclear chain reaction would be the basis for nuclear energy production, whether commercial or military. In such a reaction, each fission would generate another without any external inputs, so that once initiated, fission reactions would continue until some other factor intervened to stop them.
Uranium appeared capable of sustaining a chain reaction because each fission released more than one neutron, a neutral particle that could penetrate the outer parts of an atom to reach its tiny nucleus. After the experimental demonstration of fission in Germany in late 1938 and its confirmation in the United States in 1939, the main question that remained was: could a nuclear chain reaction be realized in practice? If so, a large sustained release of energy could be achieved. The requirement for achieving a nuclear explosion was even more stringent since each fission would have to generate more than one fission in a very short time. In this way, the number of fissions would multiply very rapidly, resulting in a huge explosive release of energy.
The first chain reaction took place in an "atomic pile," as nuclear reactors were initially called, at the University of Chicago in December 1942. However, a minimum amount of nuclear material, called a critical mass, was necessary to sustain a chain reaction. The most basic physics questions had been answered. The immense engineering job of making nuclear energy a practical reality for explosive or commercial applications remained.
It was thought early on that the widespread use of nuclear energy would be complicated by an important resource limitation. While heavy elements could be fissioned to yield energy, only one element that occurred in nature in substantial quantities could sustain a chain reaction. That element was uranium. There was a further difficulty. It was discovered that only one naturally-occurring isotope of uranium, called uranium-235, could sustain a chain reaction (see box below). However, about 99.3 percent of natural uranium consists of uranium-238, which cannot sustain a chain reaction. Uranium-235 is only about 0.7 percent of natural uranium. Still, just one gram of uranium-235, when completely fissioned, yielded as much energy as 3 metric tons of coal, which is more than annual average household energy requirement for home heating in the United States.
| Elements occur in variants called isotopes. All isotopes of an element have essentially identical chemical properties, which are determined by the number of protons in the nuclei of the element's atoms. Protons have positive electrical charges. The number of protons in a nucleus is normally equal, at ordinary temperatures, to the number of electrons that surround the nucleus in that atom. But the nuclei of elements can also contain varying numbers of neutrons, which are electrically neutral particles slightly heavier than protons, and far heavier than electrons. Changing the numbers of neutrons in the nucleus changes the properties of the nucleus and the overall weight of the atoms of an element. Variants of an element whose nuclei have the same number of protons but different numbers of neutrons are called isotopes of that element.
Some heavy nuclei are rendered highly unstable and split apart after absorbing a slow neutron, having essentially no kinetic energy. Such isotopes are said to be fissile. Other heavy nuclei require incoming neutrons (or other particles) to have a large amount of energy before they will split apart. These isotopes are fissionable, but not fissile. In general, fissile isotopes are required to sustain chain reactions, and hence to build nuclear reactors or nuclear weapons. Uranium-235 is essentially the only naturally-occurring fissile material. (21) Uranium-238 is fissionable but not fissile. |
But uranium-238 was soon found to possess another remarkable property that made it seem at least as important a substance as uranium-235. When uranium-238 absorbs a neutron, it is transmuted, in two steps, to a fissile element that is present in nature only in the minutest quantities: plutonium-239 (see Appendix A). This meant that a nuclear reactor could be used to do two things at once. First, it could generate energy by fissioning uranium-235 in a chain reaction. Second, it could at the same time convert non-fissile uranium-238, which was 140 times more plentiful than uranium-235, into fissile plutonium-239. There is so much uranium-238 in nature that it could, if converted to plutonium-239, far outstrip fossil fuels as an energy source. Limitless energy supply seemed within the reach of mankind, a prospect that gave rise to fervent, almost religious declamations by scientists about the deliverance of mankind.
The first nuclear engineering achievements were made by the U.S. military's crash program to develop the atom bomb during World War II, known as the Manhattan Project. Uranium-235 provided the explosive energy in the bomb that destroyed Hiroshima; plutonium-239 powered the Nagasaki bomb. The Manhattan Project also showed that it was possible to build large nuclear reactors, to produce plutonium in them, and subsequently to chemically separate the plutonium from fission products and the remaining uranium.
As the United States entered the post-war era, millions of Americans believed that their lives or the lives of soldiers personally near and dear to them had been saved because the atom bombings of Japan had ended the war early. U.S. leaders saw in nuclear weapons the potential to move the world in a political direction of their choosing. The immense technological feats that the U.S. had accomplished during World War II were exemplified most dramatically for all (including Stalin) by the Manhattan Project. Now they would be applied to making the United States by far the most militarily powerful country in human history and also to the material salvation of mankind. Nuclear energy was in the center of that military and economic prospect. America's romance with the atom had begun. (22)
But before commercial nuclear energy could save mankind, some problems, seemingly mundane, remained. They would come to dominate the fate of nuclear power. The devil, it turned out, was in the details:
These problems seem clear enough in hindsight. But how many were apparent in the early days? Was the romance with the atom a case so intense that it blinded engineering judgment? Was it propaganda waged for economic or military purposes? Or was it a mixture of both?
Electricity on a large scale is produced by forcibly spinning conducting wires (usually made of copper) through a magnetic field. Such a device is called an electric generator. The energy required to spin the generator and supply the current to the devices that use electricity must come from somewhere. This is the energy source for the electric power station. For instance, falling water is an energy source that is used to spin water turbines, which, in turn, drive electric generators.
The most common energy sources for electricity generation are fossil fuels, which release their energy in the form of heat upon being burned. This heat is converted into mechanical energy in a "heat engine." An internal combustion engine, such as that in a car fueled with gasoline or diesel, is one example of a heat engine. A boiler combined with a steam turbine is another way in which the chemical energy in fuels is converted into mechanical energy.
The electricity from a large-scale generating station is transmitted at high voltage (to minimize transmission losses) to the areas where it will be used. Finally, there are extensive networks of wires and transformers that distribute electricity to consumers at the voltages they require for their applications. This scheme is used in all central-station electricity generation. (23) Figure 1 (sorry, not available in on-line version of report) shows the basic elements of a nuclear power plant. The basic arrangement of a coal-fired power plant is the same, except that the reactor and steam-generator are replaced by a coal-fired boiler.
The cost elements of an electricity generation system based mainly on central station plants such as that diagrammed in Figure 1 are:
The most important thing to note about this list when evaluating the official claims that nuclear energy could one day be too cheap to meter, is that all the cost elements of a nuclear electricity system other than the fuel would be common between an electric power station that used coal (or another fossil fuel) and one that used nuclear fuel (either uranium or plutonium or some combination of the two).
The principal difference between a nuclear power station and, say, a coal-fired power plant, is in the nature of the fuel. In the one case, it is coal, which is burned in a boiler to generate hot gases, which in turn heat up water to produce steam. The boiler for using coal (or oil or natural gas) is designed to burn the fuel chemically. Nuclear energy does not come from chemical reactions, such as burning, but from nuclear reactions. The nuclear reactor merely replaces the boiler in a conventional fossil fuel power station. It generates the steam that drives the turbine. In other words, a nuclear power station differs from a conventional power station only in the fuel and the details by which the fuel is used in the boiler to generate heat. An important detail here is that the nuclear fuel is much more compact because each fission releases about 200 MeV (megaelectron volts) of energy, while burning one atom of carbon and turning it into carbon dioxide releases about 4 electron volts (eV). The higher energy per fission means that the volume of nuclear fuel per unit of power output is far smaller than for fossil fuels.
Let us now look at the actual costs of electricity generation at the time that Lewis Strauss made his famous "too cheap to meter" remark. The price of electricity in 1954 to very large industrial consumers (which is close to the cost of generation, since transmission and distribution costs for these consumers tend to be low) was about 1 cent per kilowatt-hour of electric energy generated (about 5.7 cents in 1995 dollars using the consumer price index). Subtracting the fuel cost for coal of about 0.4 cents per kilowatt hour (average price of coal, plus average coal transportation cost), we get an estimate of all other aspects of the cost of electricity generation in the mid-1950s other than fuel. This amounts to about 0.6 cents per kilowatt hour in the mid-1950s.
Since all other aspects of electricity generation were common between coal-fired and nuclear power station, the minimum conceivable charges for nuclear electricity as calculated for costs prevailing in 1954 would be 0.6 cents per kilowatt-hour. Thus, for the largest industrial consumers with factories near generating stations, the costs of nuclear electricity could be expected to be at least 60 percent of the costs of coal under assumptions so optimistic that they were considered unrealistic.
For small consumers, the cost reduction from this most optimistic assessment of nuclear energy would be far lower. This is because transmission and distribution constituted the lion's share of the cost of electricity for households and small businesses, that is for the overwhelming majority of consumers. The average price of electricity to small consumers in 1954, the year of Strauss's speech, was 2.7 cents per kilowatt hour, of which only about 0.4 cents was the cost of coal (in the case of coal-generated electricity). Thus, even if all fuel costs were eliminated, the average price of electricity to homes and small businesses would still have been 2.3 cents per kilowatt hour or about 85 percent of the full price. That was the best that nuclear energy could be expected to do.
Such cost estimates had, even on the surface, two unrealistic assumptions:
Let us take a look at each of these elements of the cost of nuclear power that were readily apparent in the 1950s. (At that time, radioactive waste disposal issues were not forecast to pose serious economic or political constraints on the development of nuclear energy.)
A. Nuclear Fuel
There are two basic fuels that are used in nuclear power reactors: uranium-235 and plutonium. (24) Natural uranium is the basic raw material for them both. Thorium-232, which occurs in nature, is also potentially a nuclear energy resource. Like uranium-238, thorium-232 is not fissile and cannot sustain a chain reaction. However, neutron absorption by a thorium-232 nuclear converts it into uranium-233 in a manner analogous to the conversion of uranium-238 into plutonium-239. Uranium-233 is fissile and can be used for both nuclear weapons and nuclear power. However, no schemes for using thorium-232 as an energy source have been commercialized. Nor has uranium-233 been used in nuclear weapons, so far as public information indicates.
1. Uranium fuel
Uranium is ubiquitous in very low concentrations. For instance, it is present in surface waters at concentrations of about 0.7 parts per billion (by weight) and in soil typically at concentrations of two or three parts per million. But it is too costly to extract pure uranium for use in nuclear reactors from such sources. Uranium ores typically contain two-tenths of one percent to roughly one-half percent uranium by weight. (25) Therefore, it is necessary to mine two hundred to five hundred metric tons of ore to get one metric ton of pure uranium. Of this, only about 7 kilograms is the fissile isotope uranium-235.
Uranium is present in nature in many different chemical forms. The ores are processed in factories called uranium mills, where the other minerals and materials are separated from uranium. The wastes, containing thorium-230 and radium-226, which are radioactive materials associated with the decay of uranium-238 (see Factsheet on Uranium), are discharged into tailings ponds. These tailings also contain non-radioactive toxic materials such as arsenic, molybdenum, and vanadium. (26) Uranium mills produce uranium in the form of uranium oxide (U3O8), also called yellow-cake. (27) Before it can used in reactors, the uranium must be put into a suitable chemical and physical form and it must have the appropriate content of fissile uranium-235. For most reactors, the proportion of uranium-235 in reactor fuel must be considerably greater than the 0.7 percent concentration found in natural uranium (see table on reactor and fuel types). A large amount of processing is needed to accomplish this. The most expensive step is uranium enrichment, so called because it increases the proportion of uranium-235 in the fuel. This process produces another stream of uranium, called depleted uranium, which has a uranium-235 content far lower than natural uranium (usually about 0.2 to 0.3 percent uranium-235). Figure 2 (not available in on-line version of report) shows the steps in converting uranium into a fuel for light water reactors, the most common kind of nuclear reactor used in power generation today.
As a consequence of the practical necessities of uranium extraction and processing, the reality of the amounts of materials that needed to be handled and processed is far different than the romantic accounts of pellets the size of vitamin pills. While one gram of uranium-235 was equivalent to 3 metric tons of coal, it typically required 200 grams of natural uranium to obtain a gram of uranium-235 in a practical fuel. And it took on the order of 50 kilograms of uranium ore to produce 200 grams of uranium. Roughly an equal amount of low grade material littered the mine sites. In sum, about 100 kilograms of ore and rejects had to be unearthed to produced a single gram of uranium-235 fuel. Coal typically came in far richer seams, so that, for high-grade deposits, such as are commonly found in the western United States and elsewhere, the amount of additional material handled at the mine site was not far greater than the end product.
2. Plutonium Fuel
In the minds of its promoters, the promise of endless nuclear energy depended centrally on the conversion of uranium-238 into plutonium-239. A suitably romantic term was given to uranium-238, which was not a fissile material and hence not suitable as a reactor fuel. Uranium-238 was called a "fertile" material because it gave birth to plutonium-239, a fissile nuclear fuel.
As we have noted, uranium-238 is converted into plutonium-239 by bombardment with neutrons. Since a very large number of atoms of uranium-238 nuclei must be so converted to produce substantial quantities of fuel, uranium-238 must be placed in a situation where a correspondingly great numbers of neutrons are being continually generated. This happens in a nuclear reactor when uranium-235 (or another fissile material) is undergoing fission at a suitable rate.
Some of the plutonium produced in a nuclear reactor also undergoes fission, contributing to energy generation. But the rest cannot be directly used as a nuclear fuel because it is mixed with large quantities of unconverted uranium-238, residual uranium-235 and highly radioactive fission products. In order to use plutonium as a reactor fuel (or as a material for nuclear weapons), it must first be separated from the fission products and remaining uranium in the reactor fuel.
Table 1 shows an example of one possible composition of reactor fuel when it is inserted into a reactor and the final composition when it is discharged from the reactor (when it is called "spent fuel," though irradiated fuel would be a more accurate term).
| Substance | Initial percentage by weight in fuel | Percentage by weight in spent fuel after 3 years |
|---|---|---|
| Uranium-238 | 97 | 95.1 |
| Uranium-235 | 3 | 0.8 |
| Plutonium, fissile isotopes | 0 | 0.7 |
| Other plutonium isotopes | 0 | 0.2 |
| Fission products | 0 | 3.2 |
Adapted from Lamarsh, Fig. 4.25, p. 150. Figures are rounded. Small quantity of uranium-234 present in fresh and spent fuel is not listed because, while it is radiologically important, it is not relevant as an energy source.
The set of steps required to extract plutonium from spent fuel is called "reprocessing" because it involves processing the fuel a second time around (the first time being when the fuel is first fabricated for use in a reactor). Reprocessing is very costly for five reasons:
The dangers of plutonium were discovered and reasonably well-understood during the course of the Manhattan Project. Their practical effect for nuclear power would be that it would be difficult and costly to fashion plutonium into fuel for nuclear reactors due to the protection from radioactivity exposures and the security precautions that would always be needed.
While it was understood that reprocessing would involve substantial costs, the magnitude of these costs was not fully realized until commercial reprocessing was attempted on a large scale from the 1960s onwards and numerous difficulties were encountered in the 1970s. The high cost and unexpected technical difficulties were associated at least partly with the far larger quantities of fission products present in reactor fuel relative to irradiated uranium used for military plutonium production (see below).
At the same time, it was commonly believed until well into the 1970s that uranium was a very scare resource. A corollary belief was that large-scale utilization of nuclear power would necessitate the use of plutonium as a fuel. This view continues to have a large number of adherents in the nuclear establishment despite the high expense of plutonium as a fuel relative to uranium for at least the next few decades.
B. Nuclear Reactors
Nuclear power plants, it should be clear, are complex installations and by their nature, they must be designed with care.--John R. Lamarsh, Introduction to Nuclear Engineering, a textbook28
As we have discussed, energy from nuclear fission comes from the transformation into energy of a small amount of the mass of a heavy nucleus when it is split. When the nucleus of uranium-235 or plutonium-239 is fissioned, the resulting energy takes many forms. Some of the energy is released in the form of high speed neutrons, some appears as electromagnetic radiation (gamma rays); most is released as vibrational energy of the fission fragments. Almost all this energy is quickly transformed into thermal energy, or heat. A nuclear reactor is basically a vessel that is designed to capture this heat energy in a liquid or gas medium called a coolant in a sustained and controlled way. A nuclear reactor must have the following features:
Reactors are classified into two types: thermal reactors, which use thermal (or "slow") neutrons to sustain the chain reaction, and fast reactors, which use fast, or energetic, neutrons to sustain the chain reaction.
(View summary of reactors here.)
1. Thermal reactors
The design of nuclear reactors depends centrally on the type of coolant that is used to carry off the heat produced in the reactor vessel. For thermal reactors, it also depends on the choice of a material called the moderator, which slows down the fast neutrons emitted in the process of fission.
Sustained chain reactions can be achieved with smaller proportions of fissile isotopes in the reactor fuel if the neutrons emitted from fission reactions are slowed down. For instance, some reactors that use slow neutrons can even use natural uranium as a fuel, even though it contains only about 0.7 percent of fissile uranium-235. Slow neutrons, called thermal neutrons, have energies of a fraction of an electron-volt (eV). Neutrons from fission reactions typically have energies of several megaelectron-volts (MeV) at the time they are emitted.
The process of slowing down neutrons in a nuclear reactor is called moderation. It is achieved by putting a moderator in a nuclear reactor. A moderator should preferentially be a light element so that neutrons can slow down when they collide with its atoms. For the most part, this happens by elastic collisions. This process is analogous to that by which billiard balls slow down when they collide with balls of similar weight. Heavy atoms would make less suitable moderators since neutrons would not lose as much energy to them in collisions. This can be visualized as billiard balls simply bouncing off when they collide with the (far heavier) edge of the pool table. Many collisions are needed to slow down fast neutrons to thermal energies. These collisions convert the kinetic energy of the fast neutrons into heat, which is randomized rather than directed kinetic energy. Finally, the moderator must also not absorb too many neutrons in the process of slowing them down. Otherwise sufficient neutrons will not remain to sustain a chain reaction.
Transfer of energy out of the reactor vessel requires that a coolant flow through it. Without a coolant, continued production of fission energy would cause the reactor vessel and its contents to get very hot. This would rapidly lead to a melting of the fuel and fuel rods, a phenomenon called a "meltdown." The coolant must also carry away the heat generated by the radioactive decay of fission products, which build up in the reactor as the fission process continues. When a reactor has been operating for a long-time, the heat from decaying fission products alone amounts to several percent of the full power rating. Loss of coolant in a reactor can produce a meltdown in such cases just due to the failure to carry away the decay heat from the fission products. For instance, this was the cause of the partial meltdown in Three Mile Island Unit 2 in 1979. (30)
In some reactors, the coolant and moderator are the same material. Hydrogen is an excellent moderator, being light and having a low neutron absorption cross-section (or probability). However, hydrogen gas is explosive and so it is used in the chemical form of ordinary water, H2O, also called light water. Further, the density of hydrogen in water (that is, the number of hydrogen atoms per unit volume of water) is far greater than that of hydrogen gas. Thus, a smaller volume of water gives the same amount of moderation as a far greater volume of hydrogen gas. Besides working well as a moderator, water is also a good coolant. Thus, the most common reactor types in the world use light water as a coolant and moderator. They are called light water reactors or LWRs.
Figure 3 (not available in on-line version of report) shows a schematic diagram of one type of light water reactor called a boiling water reactor, called a BWR. In these reactors, developed by General Electric, the water that serves as a coolant and moderator in the reactor is boiled directly in the reactor. This steam is used to drive a turbine. The main advantage of the BWR design is that it does not require an expensive boiler apart from the reactor. There are a number of disadvantages however, including higher emissions of radioactive gases and the fact that the turbines are exposed to radioactive steam.
Light water reactors are also used in another design, called a pressurized water reactor (PWR). This design, which is the most common power reactor design today, has two water circuits. The primary circuit is the high pressure water in the reactor vessel. This water is kept under such high pressure that it does not boil. The hot, high pressure water is passed though a heat exchanger, called a steam generator, where it heats up water in the secondary circuit and converts it into steam, much as the hot gases in a conventional boiler convert water in a boiler into steam. There are usually three or four steam generators in a PWR. The steam generators add considerable expense to the nuclear reactor but keep the radioactive primary coolant out of the turbines. The line diagram of a nuclear power station in Figure 1 above [not available on-line] shows a power plant with a steam generator. That figure differs from a PWR only in that it indicates a solid moderator, whereas in a PWR the coolant and moderator are the same -- ordinary water.
Deuterium, or heavy hydrogen (symbol: D), whose nucleus consists of one proton and one neutron, can also be used as a moderator. It is the best moderating material from the point of view of low neutron absorption. Like ordinary hydrogen gas, it is explosive and so is used in the chemical form of water, called heavy water (symbol: D2O). In contrast to LWRs, heavy water moderated reactors (HWRs) can use natural uranium as fuel. Figure 4 (not available in on-line version of report) shows a diagram of an HWR used for power generation in Canada, called a CANDU (CANada Deuterium Uranium) reactor.
Carbon in the form of graphite is also a good moderator, but carbon-moderated reactors need a separate coolant. The most common coolants are helium gas, carbon dioxide gas, or water. Reactors of the Chernobyl design (called RBMK reactors) use carbon in the form of graphite as a moderator and water as a coolant.
It is also necessary to control the chain reaction in order to vary the power output of the reactor. To maintain power at a sustained fixed level each fission of a heavy nucleus must produce exactly one more fission. This means that only one of the neutrons arising from fission must give rise to another fission. The ratio of the number of fissions that each fission reaction gives rise to (on average) is called the multiplication factor. For a sustained power level, the multiplication factor must be precisely equal to one. At this point, the reactor is critical and the nuclear chain reaction will sustain itself at constant power output. If the multiplication factor falls below one, the reactor becomes subcritical and the chain reaction will stop. If it rises above one, the reactor is supercritical and the power level will increase.
A parameter, called reactivity, is often used to describe reactor control. It is related to the multiplication factor in the following way: If the multiplication factor is exactly one, the reactivity is exactly zero; if the multiplication factor is greater than one, the reactivity is positive (but less than one). If the multiplication factor is between zero and one, the reactivity is negative. Reactivity is a convenient way to describe reactor control because positive reactivity means a supercritical reactor, zero reactivity means a critical reactor, and negative reactivity means a subcritical reactor.
Start-up, shut down, or change in power level -- that is, control -- of a reactor is accomplished by changing the reactivity. (31) This is done by controlling the number of nuclear fission reactions per second that typically occur in a reactor. A neutron-absorbing material, like boron, is made into rods ("control rods") which are interspersed with the fuel rods and which can be inserted into or removed from the reactor core. (32) This controls the number of neutrons available for fission reactions and the rate of energy production (or power output). A nuclear reactor can be shut down by making the reactivity negative. This is accomplished by inserting the control rods into the reactor far enough so that they will absorb the quantity of neutrons needed to stop the chain reaction. Raising the control rods temporarily makes the reactivity positive, that is, it makes reactor slightly supercritical for a short period of time, enabling an increase in the power level. The reactor is returned to the critical state (reactivity equal to zero) when the desired level of power is achieved.
Control of a reactor can be lost if the reactor continues to stay supercritical (that is, if the reactivity stays positive) for longer than intended. An increase of the multiplication factor is also called a reactivity insertion. The intense heat generated by excess fission could overwhelm the cooling systems, causing a severe accident. The most severe accident in nuclear power history, which occurred in reactor number 4 at the Chernobyl power plant on April 26, 1986, involved a loss of control of the nuclear chain reaction.
The time in which reactor power level increases by a factor of about 2.7 (or more accurately, by a factor equal to e, the base of natural logarithms) is called the reactor period. This quantity depends on the design of the reactor and the composition of the fuel. Power reactors are designed to have long reactor periods in order have slow, smooth increases and decreases in reactor temperature. This minimizes thermal stresses and allows for longer reactor operating lifetime. A typical reactor period in a power reactor would be on the order of one hour.
Control of the reactor is facilitated by the fact that while most (generally more than 99 percent) neutrons from the fission process are emitted essentially at the same time as the fission occurs, a small proportion are emitted after a relatively long time. The former are called prompt neutrons, while the latter are called delayed neutrons. If a reactor becomes critical with only prompt neutrons, the reactor period would be only a tiny fraction of a second, so that control of the reactor would be essentially impossible. But if the reactor is designed so that it does not become critical with prompt neutrons only, then the reactor period and the time available to control it can be increased greatly.
But accidental "prompt criticality" remains a safety concern, since control of the reactor could be lost if a reactor becomes critical with prompt neutrons only. The proportion of delayed neutrons in an LWR is about 0.0065 (that is about two-thirds of one percent). (33) So long as the reactivity of the reactor stays below the proportion of delayed neutrons, the reactor cannot become prompt critical, and can be controlled. An increase of reactivity above the delayed neutron fraction results in the loss of control of the reactor. For comparison, fast neutron reactors using uranium-233 or plutonium-239 fuel are even more difficult to control, since the delayed neutron fraction is only about 0.0020.
Reactors such as LWRs in which fuel is loaded in batches require more complex systems to ensure control because when the fuel is fresh, reactivity increase can be large for a modest movement of control rods. During such periods, reactor control is enhanced by adding neutron absorbing chemicals to the water. As noted above, this is known as chemical shim.
The ejection of control rods from a reactor that has relatively fresh fuel in it could result in a total loss of reactor control. This is more of a potential problem with batch-fueled reactors, such as LWRs, than with continuous fueled reactors, such as the Canadian heavy water reactor (CANDU).
Commercial light water reactors use uranium fuel enriched to between 3 and 5 percent as a fuel. Graphite or heavy water moderated reactors can use natural uranium as a fuel. This is a considerable advantage in countries that do not have uranium enrichment plants. It was a principal factor that led a number of countries, including the Soviet Union, France, and Britain, to choose graphite-moderated reactors when they began their military plutonium production. U.S. naval reactors use highly enriched uranium (up to 97.6 percent enrichment) as a fuel because this enables the reactors to operate for longer periods without refueling.
Table 2 shows various types of thermal reactors, along with the coolants, moderators, and fuel types they use.
2. Breeder Reactors (Fast Neutron Reactors)
As we have discussed above, of the fissile materials usable for practical nuclear energy production, only uranium-235 occurs in any substantial quantities in nature. The other two, plutonium-239 and uranium-233, must be made from uranium-238 and thorium-232 respectively, which are far more abundant than naturally-occurring fissile uranium-235. The process of converting "fertile" uranium-238 and thorium-232 into fissile materials is called "breeding," evidently by analogy with biological reproduction.
Commercial nuclear power reactors use natural or "low-enriched" uranium as fuel. Natural uranium contains 0.711% uranium-235 and "low-enriched" reactor fuel contains from 1% to 5% uranium-235, depending on reactor design. Almost all the rest is uranium-238. (See Uranium Factsheet.)
Some of the neutrons in a nuclear reactor convert uranium-238 into plutonium-239. In other words, there is "breeding" of plutonium in all commercial reactors containing uranium-238. However, the term "breeder" reactor is reserved for those reactors in which the production of plutonium-239 (or uranium-233) from fertile materials is greater than the amount of fissile material consumed in the reactor. The ratio of the number of fissile atoms produced to that consumed is called the "breeding ratio" or "conversion ratio." A reactor that is designed so that the breeding ratio can exceed one is called a "breeder reactor." When this happens, the fuel output is greater than the fuel input. This (potential) feature was one of the reasons that nuclear energy was often described as a magical energy source.
In commercial reactors now in operation around the world, like LWRs and HWRs, the breeding ratio is less than one; they are referred to as "converter reactors." Typically, a light water reactor converts just under two percent of the uranium-238 into plutonium isotopes, about two-thirds of which consists of the fissile isotopes plutonium-239 and plutonium-241, while the rest consists of the non-fissile isotopes, mainly plutonium-240. Almost half of this plutonium is consumed during normal reactor operation, leaving the rest in the spent fuel. The plutonium consumed during reactor operation typically contributes about one-fourth to one-third of the energy generated in light water reactors. (34)
Since doubling times for breeding U-233 are far longer than for breeding Pu-239, almost all breeder reactors so far have been built to breed Pu-239. A further disadvantage of thorium-232-based breeder reactors cycle is the high gamma radioactivity due to contaminants in recovered uranium-233. This radioactivity arises mainly from the decay products of uranium-232, which is created in thorium-uranium fueled breeders by various nuclear reactions. (35) India seems to be the only country with a substantial active program to pursue U-233 breeding, since it has very large thorium-232 reserves, which are far greater than its domestic uranium-238 resources.
The number of neutrons per fission required for successful operation of a breeder reactor is considerably greater than for a converter reactor. This is because in addition to the one neutron per fission required to maintain the nuclear chain reaction in the reactor, at least one more is required to convert one atom of U-238 into an atom Pu-239 in order to maintain a breeding ratio of one or more. In practice, since some neutrons are absorbed by the moderator, by other materials in the reactor vessel, and by the reactor vessel itself, the number of neutrons required for a breeding ratio greater than one is considerably more than two per fission.
The number of neutrons produced per fission from U-235 or Pu-239 when fissioned by slow (thermal) neutrons is 2.07 and 2.14 respectively; neither of these ratios is sufficiently large to permit the breeding ratio to be greater than one. In other words, there are not enough neutrons available to produce enough plutonium so it will exceed the fissile materials consumed and simultaneously maintain the chain reaction, given other neutron loss mechanisms.
To overcome this problem, breeder reactor designers take advantage of the fact that if the nuclei of U-235 or Pu-239 are bombarded by fast neutrons (energies of several hundred KeV or more), then the number of neutrons per fission increases substantially. For instance, the number of neutrons per fission for 5 MeV neutrons rises to about 3 for U-235 and to about 3.5 for Pu-239. Pu-239 breeder reactors employ this property by using fast neutrons to accomplish both fuel breeding and energy production. Breeder reactors using fast neutrons are also called "fast breeders" or "fast neutron reactors."
Fast breeders, by definition, need no moderators which slow down neutrons, since they use fast neutrons for fission and breeding. They cannot use ordinary water or heavy water as a coolant because these materials also act as moderators. Gases, which have low density, or atoms with heavy nuclei (mass numbers much greater than one), such as sodium metal, can be used as coolants in fast breeders. Molten salt has also been proposed. Liquid sodium, which has a mass number of 23, compared to 1 for ordinary hydrogen and 2 for deuterium, is the most common breeder reactor coolant. Since a coolant must continually flow across fuel elements, it must be a gas or liquid. Since sodium is a solid at room temperature, it must be maintained in liquid form in a breeder reactor by heating it continually, even when the reactor is shut down.
The most common type of breeder reactor is called the Liquid Metal Fast Breeder Reactor (LMFBR). Figure 5 (not available in on-line version of report) shows a schematic diagram of an LMFBR. A more recent variant of the liquid metal fast reactor design was being developed by Argonne National Laboratory until it was canceled in 1994. It was called the Integral Fast Reactor (IFR). This design had an electrolytic reprocessing plant that accompanied it. Electrolytic reprocessing, called electrometallurgical processing or pyroprocessing, is still being pursued by the DOE at Argonne West in Idaho. (36)
Sodium catches fire on contact with air and explodes on contact with water. Further, the nucleus of ordinary sodium absorbs a neutron and turns into a highly radioactive isotope sodium-24. This is a major threat in case of a breeder reactor accident. To prevent leakage of sodium-24 into the environment, sodium-cooled reactors are designed with two liquid sodium loops. The secondary, non-radioactive sodium loop draws heat from the primary loop and, in turn, is used to boil water in a steam generator. The December 1995 accident at the Japanese breeder reactor at Monju involved a large leak of sodium from the secondary loop.
Despite its theoretical attractiveness in converting non-fissile into fissile material, the breeder reactor has turned out to be a far tougher technology than thermal reactors. Despite five decades of effort during which many pilot and "demonstration" plants have been built, the sodium-cooled breeder reactor design remains on the margin of commercial nuclear technology. The magic of fuel multiplication has not yet been realized on any meaningful scale relative to nuclear electricity generation levels. Plutonium can also be mixed with uranium for use in thermal reactors. Generally, both plutonium and uranium are mixed after conversion into a dioxide chemical form. For this reason, the plutonium-uranium fuel mixture is called "mixed oxide" fuel, or "MOX" fuel for short.
C. The "Nuclear Fuel Cycle"
Nuclear power as initially conceived was to be based on using both the natural fissile material uranium-235 and increasing the amount of fissile material by converting uranium-238 (or thorium-232) into fissile materials. In this scheme of things, uranium mining and milling would eventually be a supplement to the creation of fissile materials from an initial stock of fertile uranium-238 and thorium-232 in nuclear reactors.
Reprocessing plants would separate the fissile isotopes from the spent fuel for use in fuel fabrication plants. Many of the long-lived highly radioactive fission products resulting from power generation would be used for a variety of purposes, ranging from nuclear medicine to food irradiation to thermoelectric generators to a vast array of science fiction type of applications that became the subject of much swooning prose in the decade that followed the end of World War II. There would be little waste. There would be a nuclear fuel cycle.
However, it was recognized even in the early years that large scale use of nuclear energy would produce fission products in such huge quantities that some arrangements would have to be made for their disposal. But expectations that disposal in salt mines would be a relatively straightforward matter proved too optimistic, like so many other prognostications regarding nuclear power. (See Chapter 6.)[Not available on-line.]
To complicate matters further, reprocessing and fabrication of plutonium into reactor fuel (whether for breeder reactors or light water reactors) turned out to be very expensive, while uranium resources were far more plentiful than anticipated in the 1950s. This made the use of plutonium as a fuel uneconomical, leading to a build-up of spent fuel (which is irradiated fuel discharged from a reactor) at power plant sites. The mounting plutonium stocks, both separated and in spent fuel, are a major source of concern as regards their proliferation potential.
Click here for a table of nuclear reactor accidents.
Nuclear power has been promoted in the late 1980s and early 1990s in a number of ways enabling it to regain ground lost in the wake of the 1979 partial meltdown in Unit 2 of the Three Mile Island nuclear plant in Pennsylvania. This has included diverse efforts such as DOE and nuclear industry intervention on behalf of the beleaguered Shoreham and Seabrook nuclear plants in New York and New Hampshire (the latter opened, the former did not), to major stories on the cover of Time magazine.174 A wide array of nuclear industry groups, operating in a coalition named the Nuclear Power Oversight Committee, had the ambition of having a new commercial nuclear plant ordered by the mid-1990s.175 As another example, the Nuclear Energy Institute in 1995 published the fifth annual update of its plan to revive nuclear power.176 This time around the industry has also been putting forward an environmental rationale as part of its promotion of nuclear power. Its spokespersons state that nuclear power could be a principal factor in cutting back emissions of pollutants, notably carbon dioxide which results from the burning of fossil fuels. As an article in Fortune magazine put it, "concern about the earth's rising temperature could turn a technological pariah into a savior -- if new reactor designs overcome worries about atomic safety."177 To address the safety concern, the nuclear industry has been promoting a "second generation" of commercial nuclear power reactors, some of which have been labeled "inherently safe" by their proponents. Is that claim reasonable? Another big question is whether such plants can be economically viable. And is nuclear power the appropriate way to address concerns about the build-up of greenhouse gases? The safety question is a central one, since public skepticism of industry claims grew greatly after the Three Mile Island and Chernobyl accidents. But the road will be a hard one, perhaps impossible due to the choices that were made in the initial development of nuclear power. The safety issues surrounding nuclear power are especially difficult not only because of the technological complexity of the plants, but also because of the potentially catastrophic and irreversible consequences of severe accidents. For instance, after the accident at Three Mile Island, one of the investigators made the following comment:
Appendix A: Basics of Nuclear Physics and Fission
Part II -- More Nuclear Power Plants or a Sound Energy Policy?
It will not be possible to provide the energy needed to bring a decent standard of living to the world's poor or to sustain the economic well-being of the industrialized countries in environmentally acceptable ways, if the present energy course continues. The path to a sustainable society requires more efficient energy use and a shift to a variety of renewable energy sources.
--Johansson et al., eds. 1993173
Chapter 7: "Inherently Safe" Reactors: Commercial Nuclear Power's Second Generation?
If there is one thing that I have learned through the [Three Mile Island] investigation, it is this: Nuclear power plants are very large, very complex systems that cannot be completely accurately modeled. Dangerous transients cannot be incurred deliberately so that the actual plant response to all events can be experienced and tested....Current plant performance statistics must not be accepted as "good enough" because they may not be good enough for the future, and one accident is one too many.178
NRC Commissioner James Asselstine, in Congressional testimony in 1986, put the results of the NRC reassessment this way:
The bottom line is that given the present level of safety being achieved by the operating nuclear power plants in this country, we can expect to see a core meltdown accident within the next 20 years; and it is possible that such an accident could result in off-site releases of radiation which are as large as, or larger than, the releases estimated to have occurred at Chernobyl.180The safety problems with the current generation of reactors have contributed to the widespread resistance to nuclear power. As even the NRC has acknowledged,
Public acceptance, and hence investor acceptance, of nuclear technology is dependent on demonstrable progress in safety performance, including the reduction in frequency of accident precursor events as well as a diminished controversy among experts as to the adequacy of nuclear safety technology.181Advocates for a second generation of nuclear plants imply or state that this safety problem has been solved with new designs that rely on "passive" or "inherent" safety features. We will discuss some of these designs in the section below.
New Reactor Designs: An Overview
Although there is strong support among nuclear industry manufacturers for the idea of a revitalization of nuclear power, there is considerable debate as to what type of reactor technology should be used for the job.
Many designs have been proposed, ranging from those that are only modest modifications of current light water designs, to substantially different designs cooled by gas or liquid sodium metal. The basic concepts underlying these latter designs have been around as long as nuclear power, but they were edged out of the market in the early years by the light water reactor bandwagon. The "advanced" reactors tend to have the following features;
There is a basic split between the "old guard" which continues to advocate the basic light water design, with improvements, and those who back non-light water designs in the hope that their design will alleviate the widespread concerns about safety associated with light water reactors. Proponents of the LWR believe that its safety can be improved and that investment in its continued dominance of the market is the best strategy for promoting nuclear power. Advocates of newer designs believe that nuclear power may gain more public acceptance through use of the term "inherently safe." But while these designs have been given new life under the label "inherently safe," it has raised concerns among the light water old guard that this nomenclature implicitly brands the LWR as inherently unsafe.
The promoters of variations on the light water design tend to be those who have strong economic interest in reinvigorating the industry on the basis of the existing light water technology, in which they have substantial investment. For instance the Nuclear Power Oversight Committee, mentioned above, has stated that
The extensive operating experience with today's light water reactors (LWRs), and the promise shown in recent technical developments, leads the industry to the conclusion that the next nuclear plants ordered in the United States will be advanced light water reactors (ALWRs).182According to this industry group, the advantage of the light water reactor approach is that it "rel[ies] on proven technology."183 This attitude is shared by similarly situated industry members in Europe. Karlheinz Orth, an official of the nuclear division of Siemens AG, for example, has said that the contrast between the effects of the Three Mile Island and Chernobyl accidents proved the basic soundness of the pressurized light water reactor. But at the same time Orth criticizes some of the new designs for an over-reliance on passive systems. As he told an international safety conference in 1988:
The importance of passivity is overestimated. Every reactor concept is based on certain inherent safety features and also depends on active and passive engineered safety features.... Where reliance is placed solely on inherent safety features or on purely passive engineered safety features, it would not be possible for an operator to select or even influence the final condition of the plant....There is no reason to leave today's mature LWR technology only in order to experiment with ... half-developed but 'alternative' concepts. Preferences established by publicity can be no substitute for operational experience.184To advocates of advanced reactor designs, it is precisely such attitudes that are hurting the chance for the development of a new generation of safer reactors. In the words of an advocate of a helium-cooled, carbon-moderated reactor called the MHTGR (Modular High-Temperature Gas-Cooled Reactor):
Deployment of a qualitatively different second generation of nuclear reactors can have important benefits for the United States. Surprisingly, it may well be the 'nuclear establishment' itself, with enormous investments of money and pride in the existing nuclear systems, that rejects second generation reactors. It may be that we will not have a second generation of reactors until the first generation of nuclear engineers and nuclear power advocates has retired.185We briefly review some of the proposed light water designs and then do the same for the MHTGR.
New Light Water Reactor Designs
The range of new light water designs has been divided in to two broad classes: evolutionary light-water designs (which are similar to recent LWRs, but have enhanced features), and advanced water-cooled designs (which, although water-cooled, have designs which are significantly different than recent LWRs).186 Several examples of evolutionary LWRs include:187
Advanced light water reactor designs, on the other hand, tend to be smaller than the evolutionary designs (ranging from 320 to 750 MWe), incorporating many features which are referred to as "passive" safety systems. They also tend to incorporate modular construction features which it is claimed will reduce the costs of the plants. Some examples of advanced light water designs are:191
Other Reactor Designs
So-called "inherently safe" reactor designs include those which are substantially different from the light water designs referred to above. These include several new versions of liquid metal-cooled breeder reactors, such as the General Electric Power Reactor Inherently Safe Module (PRISM) design, and Rockwell International's Sodium Advanced Fast Reactor (SAFR). As with other supposedly "inherently safe" designs, these claims appear to be more in the realm of propaganda than fact. Any reactor which uses liquid sodium as a coolant is vulnerable to the violent chemical reactions and potential explosions which can occur from contact of sodium metal with water. Moreover, use of breeder reactors generally involves reprocessing of spent nuclear fuel and plutonium fabrication activities, which bring with them a whole host of safety, proliferation, and environmental issues.
The MHTGR
Much of the attention regarding "inherently safe" reactors has been garnered by the modular high-temperature gas-cooled reactor (MHTGR). As noted above, this design relies on helium for coolant and is graphite moderated. As is the case with the pressurized light water reactor, the coolant circulates through steam generators which turn water to steam and drive a steam turbine.196
Although there is a fair amount of experience with gas-cooled reactors in Britain (the Magnox design), there have been only two operating commercial plants in the U.S. which have used the high temperature gas-cooled design: Peach Bottom-1, a 40 MWe reactor in Pennsylvania which operated from January 1967 to November 1974, and the 330 MWe Fort St. Vrain reactor near Denver, Colorado. Neither of these plants is still operating.
It is noteworthy that the Fort St. Vrain HTGR in the U.S. had a lifetime capacity factor of 14.5 percent, an availability factor of 30.9 percent, and a forced outage rate of 60.8 percent before it was permanently shut down in August 1989, partly due to its uneconomic performance.197 In fact, by the above measure, the Ft. St. Vrain HTGR was the single, worst-performing commercial reactor in the U.S. nuclear industry.
The variation of this design most generally discussed in the current debate is of the "modular" variety, so named because each reactor unit is considerably smaller (100 or 150 MWe) than many of the existing reactor units, so that a plant would be made up of several "modules." The smaller versions of the HTGR are claimed to be meltdown proof.
Because it has received so much attention among advanced reactor designs, and because it is one of the electricity-producing designs that may be used for military plutonium disposition and tritium production (although DOE is not now actively considering it), we will discuss this design in some detail.
Although there are several variations, the basic MHTGR design in the U.S. is being promoted by General Atomics. General Atomics' promotional literature describes the reactor in the following words:
The MHTGR is a second generation nuclear power system which can satisfy the concerns of the public, the government, the utilities and the investor community about nuclear safety and investment protection. Based on technology developed and demonstrated in the U.S. and Germany, the unique system makes use of refractory coated nuclear fuel, helium gas as an inert coolant and graphite as a stable core structural material. The safety and protection of the plant investment is provided by inherent and passive features not dependent on operator actions or the activation of engineered systems. The high performance MHTGR provides flexibility in power output and siting, competitive energy costs, and can serve diverse energy needs both domestically and internationally.198According to General Atomics, the basic safety idea which the MHTGR, its different fuel design, combined with a size limitation for the reactor (hence the term "modular"), is supposed to make one of the most commonly feared accident scenarios -- the core meltdown -- impossible.
In contrast to the zircaloy metal-clad uranium oxide ceramic pellets of a light water reactor, the MHTGR fuel form is designed to withstand a much higher temperature. Instead of being arranged in vertical rods, the fuel is in the form of millions of tiny spheres, each about the size of a grain of sand. The fuel "kernels" of these spheres (about 350 microns in diameter) consist of enriched uranium mixture of uranium oxide and uranium carbide. The fuel kernels are coated with two layers of pyrolytic carbon and one layer of silicon carbide. Thorium oxide grains for breeding uranium-233 fuel are similarly configured. A full core of fuel is designed to contain a total of about 10 billion fuel kernels, which are sealed in vertical holes in graphite blocks. The graphite acts as the neutron moderator.199
Normally, during operation or shut-down, the heat generated by MHTGR fuel is carried away by helium gas coolant. If the main heat transfer systems become unavailable through accident or mishap, there is a system which uses natural circulation of air to passively carry away the heat. This system, called the Reactor Cavity Cooling System, operates by natural circulation of outside air through cooling panels along the reactor walls. This system does not depend on active components like pumps, or on actions taken by operators. If by some means even this system is disabled (by vent blockage, for example), the reactor's proponents claim that direct heat conduction from reactor vessel to the reactor cavity wall to the ground is sufficient to remove decay heat without resulting in significant releases of radioactivity from failed fuel elements.200
MIT nuclear engineering professor Lawrence Lidsky, an advocate of another variation of the MHTGR, has described the safety features of the basic design:
The...radically different fuel form...is capable of withstanding very high temperatures. The [MHTGR] reactors are small to ensure that it is physically impossible for such temperatures ever to be achieved. Such reactors are termed "inherently safe." They are sometimes labeled "passively safe" because no action whatever need be taken to mitigate the effects of equipment failure. Whatever the name, these new reactors eliminate the need for the defense-in-depth strategy. They are designed so that the power plant could suffer the simultaneous failure of all its control and cooling systems without any danger to the public living near the power plant.201The claims of "inherent safety" for the MHTGR are based on its ability to withstand a loss-of-coolant accident without a catastrophic release of radioactivity. The power density and overall reactor size are substantially smaller in the MHTGR relative to present light water reactors, while at the same time the temperature at which its fuel fails is higher than the zircaloy cladding of LWR fuel.202 But this does not mean that the reactor cannot suffer a loss-of-coolant-accident even in theory. However, the time-scale over which such an accident might develop would be far longer than with an LWR, and the fuel design would help reduce releases of radioactivity, especially if the reactor design incorporated secondary containment.
Safety Concerns
In considering the safety characteristics of the MHTGR it is well to recall the warning of a British survey, which commented that advanced reactor designers "tend to concentrate...on one particular aspect such as a [loss-of-coolant accident], and replace all the systems for dealing with that with passive ones. In so doing, they ignore other known transients or transients possibly novel to their design."
In this context it is useful to note that the principal original safety concern when nuclear reactor technology was under development was not that they might melt down, but that they might explode due to heating caused by a runaway nuclear reaction. This could result from an inadvertent increase in the multiplication factor causing the reactor to become supercritical (see Chapter 2). Neutrons are what cause the fission reaction, and in some cases, the neutron spike accompanying a sudden supercriticality can lead to an explosion of the reactor core. It is this sort of event which occurred at the Chernobyl reactor unit 4 in the Soviet Union on April 26, 1986, resulting in a catastrophic release of fission products to the environment (see below).
Such a concern was also present in the early days of U.S. nuclear power, particularly with regard to the proposed use of liquid metal cooled fast breeder reactors, such as the Fermi-I reactor which was built near Detroit, Michigan before a partial meltdown in 1966 damaged its reactor core.
In an ironic historical footnote that carries an important cautionary lesson for the current debate, it is interesting that the term "inherently safe" appears to have first been applied to the light water reactor precisely because its design was resistant to large positive reactivity insertions which could lead to a runaway power excursion accident. For example, a 1955 Popular Science magazine article lauded the Indian Point-1 reactor then under construction near New York City because of its use of the "Old reliable PWR" design, which was characterized by the article as "inherently safe" because of its "built-in gentleness."203
The MHTGR design, it is interesting to note, is apparently susceptible to large reactivity insertion events. As stated in the Union of Concerned Scientists analysis of advanced reactors:
...we do not consider it to be 'inherently safe' that the MHTGR design experiences a very large reactivity insertion if a control rod ejection accident should occur. In the case of a control rod ejection, the reactor coolant system boundary is breached, and a large reactivity insertion (combined with access of the coolant and/or core to the atmosphere) could result in a very large release of radioactivity to the environment.204A Nuclear Regulatory Commission study of the MHTGR stated, "Both DOE and [Oak Ridge National Laboratory] calculate that the rapid ejection of a control rod could cause the reactor to go prompt critical. For this reason, the potential for rod ejection from the MHTGR must be precluded by design as it is for Fort St. Vrain."205
In the Fort St. Vrain reactor (which, as mentioned above, is one of only two power-generating HTGRs which have actually operated in the U.S.) the control rod ejection issue was addressed by two redundant structural systems designed to prevent such ejection. As the UCS advanced reactor study notes, however, "This feature of Fort St. Vrain is an engineered safety system solution to an important safety issue; it does not represent an 'inherently safe' design."206
In addition to the potential for reactivity insertions, several other potential safety concerns associated with the MHTGR were discussed in the Union of Concerned Scientists advanced reactor study. These include:
Whatever the mechanism, water ingress to the MHTGR core is another event which leads to power increase due to positive reactivity insertion. Moisture entering the primary system also chemically attacks the graphite core structure and the fuel. Ultimately, chemical attack on the fuel (especially defective fuel elements) combined with elevated temperature could lead to some release of fission products from the fuel. One set of assumptions pertaining to such a scenario results in calculated offsite doses to the thyroid of about 3.8 rem.208 We note here that leakage of moisture into the helium coolant was a problem at the Fort St. Vrain plant and cooling-system component failures were a cause of poor operation and eventual shut down of the plant.209
It is worth noting that versions of the MHTGR design other than General Atomics' reference design may substantially alleviate some of these concerns. For example, the design, advocated by MIT nuclear engineering Professor Lawrence Lidsky, is only 200 megawatts-thermal in size, and employs a direct cycle gas turbine for generating electricity, rather than the use of a steam generator system assumed in the General Atomics design.213 The use of a gas turbine would remove the need for using water in the system, other than for cooling the gas before it is recirculated into the reactor. This would greatly reduce concerns having to do with water contamination and the concomitant risks (such as a reactivity insertion, chemical attack on the fuel elements, and generation of combustible gases from reactions with steam). This design variant may be adopted by DOE or General Atomics should an HTGR be built in the United States or in Russia.In the advanced reactor designs, air passages of the safety-grade decay heat removal systems provide man-sized passages ... from the protected area yard to locations where relatively small amounts of explosives in the form of shaped charges could breach the reactor vessel.212
The discussion above illustrates how variations on the same basic design can potentially result in significant differences in safety level and operational characteristics. They also indicate that a vigorous and open debate over designs while they are still in the paper and experimental, small-scale stages is likely to result in a better and more economical outcome than making adjustments later on.
The Semantics of "Inherent Safety
The general arguments of advanced reactor advocates, some of which may be conceptually plausible and appealing, are difficult to either verify or refute in the abstract. This is because they are all essentially in the design stage, with only very limited details made public. Although greater incorporation of passive safety features, if undertaken with care and rigor, could be an advance in reactor design philosophy, we are concerned with the constant references by advanced reactor advocates to the supposed "inherent safety" of their designs.
Regardless of the validity of claims about immunity to the meltdown accident scenario, this terminology of "inherent safety" has more rhetorical merit than technical content. It is fundamentally misleading to describe as "inherently safe" a technology which necessarily contains and produces such large amounts of extremely hazardous material as does nuclear power. Although it may be possible to design a reactor which renders certain accident scenarios virtually impossible -- or to make reactors that are considerably safer relative to existing reactors -- that does not mean that the technology per se can be considered to have acquired safety as an inherent characteristic.
As stated in a 1990 study by the Union of Concerned Scientists (UCS) which considered several advanced reactor designs,
As a general proposition, there is nothing 'inherently' safe about a nuclear reactor. Regardless of the attention to design, construction, operation, and management of nuclear reactors, there is always something that could be done (or not done) to render the reactor dangerous. The degree to which this is true varies from design to design, but we believe that our general conclusion is correct.214This conclusion is not limited to groups such as the Union of Concerned Scientists, which maintain a healthy skepticism about nuclear power. A study conducted by Oak Ridge National Laboratory also has reached similar conclusions:
A nuclear reactor can never be completely inherently safe because it contains large quantities of radioactive materials to generate usable heat-energy; but nuclear reactors can be made inherently safe against some types of events and have characteristics which limit consequences of certain postulated accidents.215These cautionary statements raise another crucial concern: the possibility that in designing to eliminate certain now-commonly recognized accident possibilities, new accident scenarios will be unwittingly introduced. As a survey of advanced designs by Britain's Atomic Energy Agency concluded,
Safety arguments, in many cases, are very underdeveloped, making it difficult to gauge if the reactor is any safer than traditional systems. [Advanced reactor] designers tend to concentrate... on one particular aspect such as a [loss-of-coolant accident], and replace all the systems for dealing with that with passive ones. In so doing, they ignore other known transients or transients possibly novel to their design.216This is an important warning. Nuclear technology is complex, and it has taken many years of analysis and experience to even recognize the existence or the possibility of some accident possibilities for the four-decade-old light water reactor. The history of nuclear power development is replete with instances of incidents occurring at operating power plants which had not previously been thought possible. This is even true of the meltdown scenario discussed above, which was not even recognized as a safety issue until the mid-1960s -- over a decade after the decision to build the Shippingport reactor. In view of this history and the complexity of reactors, it would be prudent to anticipate that similar unexpected discoveries may be encountered in the development of a new generation of reactors based on any new design.
The verification of the safety claims of any particular vendor, of course, requires that the details of the design be made public so they can be examined for potential safety flaws. Handwaving arguments about general design features which are alleged to guarantee inherent safety should not be allowed to substitute for actual design details and real-world data on actual components. To a large extent, however, the fine engineering details do not yet exist for designs that are not yet "construction ready."
The entire debate to date on the issue of the level of safety of new reactor designs has taken place largely on a theoretical level. While theoretical work is a necessary part of design, it cannot settle all essential safety questions by itself. Even the degree of relative safety of a reactor design is no easy matter to determine. Questions relating to the net level of improved safety are highly complex, and rely on substantial analysis of the fine details of design and experience accrued over time.
Safety uncertainties can never be fully resolved in advance, and will inevitably remain large until many years of operating experience have been acquired with advanced reactor designs. That is a crucial problem in the development of nuclear power. Operating experience is needed to make the right decisions about overall designs as well as critical detail, but getting that operating experience in itself involves non-negligible risks, at least if the scale of reactors is anywhere close to those required for large-scale commercial power generation. The only approach that could resolve this aspect of the problem of nuclear power is to study designs on paper thoroughly and then to acquire long experience with small scale devices, much in the manner that small-scale models of airplanes are tested extensively in wind tunnels prior to construction of full-scale prototypes.
Accidents and Nuclear Technology
Three major reactor design concepts have been put forward since the start of the nuclear era that have been implemented in commercial nuclear power:
As with any technology, there have been a variety of problems in the development and implementation of nuclear power plants which have led to improved safety features. Some malfunctions were the result of experiments to test reactor designs, as was the case with the partial meltdown of the EBR I reactor in Idaho. Table 1 shows a list of some reactor accidents, including the major known ones.
Despite the considerable progress in understanding reactor safety over five decades (including experience with Manhattan Project reactors), the potential for catastrophic accidents continues to exist. A major reason is that nuclear power reactor designs were selected too quickly on the basis of energy, economic, military, and political criteria that did not give sufficient weight to the problems associated with catastrophic accident possibilities.
Light water reactors, by far the most common design today, were the simplest for the U.S. to build in the short-term and hence gave the largest propaganda advantage to the United States during the Cold War. But this meant that the laboratory and theoretical work that was needed to understand the most severe accident, the loss of coolant from the reactor core, was completed over a decade after the 1954 decision to build Shippingport. By that time the investment in the light water reactor was so great that the main reaction of the AEC was to try to cover up or downplay the seriousness of the problems.
Table 1: Some Reactor Accidents
|
Reactor Type |
Location |
Accident Type |
Year |
Iodine-131 Release (Curies) |
Comments |
|
Graphite-moderated, gas-cooled |
Sellafield, Britain |
graphite fire |
1957 |
20,000 |
|
|
Graphite-moderated, water cooled |
Chernobyl, Ukraine |
supercriticality, steam explosion and graphite fire |
1986 |
7 million, perhaps far greater (see text) |
Safety experiment went awry; total release 50 to 80 million curies or more; potential for continuing large releases exists |
|
Sodium-cooled fast breeder |
Lagoona Beach (near Detroit) U.S. |
cooling system block, partial meltdown |
1966 |
release confined to the secondary containment |
Reactor was being tested for full power, but did not reach it; four minutes from indication of negative reactivity to meltdown |
|
Sodium-cooled fast breeder |
Monju, Japan |
major secondary sodium leak |
1995 |
Secondary sodium was not radioactive; reactor was in test phase; extensive sodium contamination in plant |
|
|
Light water reactor, PWR type |
Three Mile Island, near Harrisburg, U.S. |
cooling system failure, partial meltdown |
1979 |
13 to 17 |
Secondary containment prevented release of millions of curies of I-131; accident developed over several hours |
|
Light water reactor, BWR type |
near Idaho Falls, U.S. |
accidental supercriticality followed by explosion and destruction of the reactor |
1961 |
80 |
Small U.S. Army experimental reactor using HEU fuel; 3 operators were killed |
|
Heavy-water cooled and -moderated reactor |
Chalk River, Canada |
lack of coolant for a fuel element |
1958 |
radioactivity apparently contained within building |
Highest worker dose 19 rem |
|
Heavy water-moderated, light water-cooled, experimental reactor |
Chalk River, Canada |
inadvertent supercriticality and partial meltdown |
1952 |
"There was some release of radioactivity" |
President Jimmy Carter helped in the clean-up |
|
Heavy water-moderated and -cooled, CANDU type |
Narora, Uttar Pradesh, India |
turbine fire; emergency core cooling system operated to prevent meltdown system |
1993 |
apparently no release of radioactivity |
Sources: Chernobyl: NRC 1987 and Medvedev 1990; Sellafield: Makhijani et al. eds. 1995, Chapter 8; Three Mile Island: TMI Commission 1979 ; Lagoona Beach (Fermi-I) Alexanderson, ed. 1979 and Fuller 1975; Idaho: Horan and Gammill 1963 and Brynes et al. 1961; Monju: press reports; Chalk River: John May 1989 and Weinberg 1994; Narora, press reports.
There are at least three questions pertaining to catastrophic nuclear power plant accidents that are germane to the evaluation of the soundness of nuclear technology as a choice for future energy supply:
Similar questions can also be asked about other technologies. We will address some aspects of this issue in the concluding chapter of this report [not available on-line]. Let us first examine the Chernobyl accident, by far the worst in the history of nuclear power, for the lessons it might have to offer.
Chernobyl
On April 25, 1986, the operators of the Chernobyl Unit Number 4 were scheduled to perform an experiment designed to test an aspect of the safety of the RBMK design. The experiment was delayed for a number of reasons, including difficulty in stabilizing reactor power level. The operators decided to proceed with the test at 1:22 a.m. on the morning of April 26. Thirty seconds after the test began, an automatic computer printout indicated unsafe conditions, requiring the reactor to be shut down immediately.
There followed a runaway supercriticality which greatly increased the power level, heated up the reactor, and increased the steam pressure in it to such high levels that it exploded, blew off the top of the reactor, and destroyed it. Less than 90 seconds had elapsed between the computer warning to shut the reactor and the total destruction of the reactor.
Thirty fires were ignited in the reactor core and in other parts of the power plant, including the turbine building. Fire fighters arrived at the scene an hour-and-a-half later. They extinguished fires other than those in the reactor core relatively rapidly, but the reactor graphite fire lasted for ten days. Radioactivity releases went on for months after the fire had been extinguished.217
It was one of the two worst industrial disasters in human history, the other being the December 1984 disaster at the Union Carbide plant in Bhopal, India during which deadly methyl isocyanate gas was released. In both accidents hundreds of thousands of people were affected during the accident and in its aftermath. Thousands of people died on the night of the Bhopal catastrophe; in the case of Chernobyl the immediate toll has officially been reported as 31, which is on the order of a hundred times lower. But the affected population increased dramatically in the aftermath of Chernobyl -- 130,000 people were evacuated, including the entire population of 45,000 in the town of Pripyat. More were evacuated subsequently, and hundreds of thousands of workers and soldiers were pressed into entombing the leaking reactor, digging up and burying vast quantities of highly contaminated soil, and performing other clean-up jobs.
Official estimates put the cumulative release of radioactivity between April 26 and May 6, when the fire was put out, at about 80 million curies. Of this total, 45 million curies are attributed to xenon-133, 7.3 million to iodine-131, 1 million to cesium-137, half-a-million to cesium-134, and 220,000 to strontium-90.218
These official Soviet estimates are misleading and understate the actual extent of the releases. For instance, the release estimates are adjusted for decay to ten days after the accident began. Xenon-133 has a half life of 5.27 days and most of it was emitted early on in the fire. On this basis, the actual amount in the fallout cloud as it passed over communities was considerably greater. Similarly, iodine-131 has a half-life of 8.05 days and far more of it was deposited on grazing lands than indicated by the decay-corrected estimate of 7.3 million curies.
Zhores Medvedev, the Soviet scientist who first reported on the other nuclear catastrophe in the Soviet Union, the explosion in a high-level waste tank at Chelyabinsk-65 in 1957,219 states in his study of the Chernobyl accident that the official figures for radioactivity releases include only the amounts deposited inside the former Soviet Union and do not take into account the much larger deposition of some radionuclides, such as iodine-131 and cesium isotopes outside Soviet territory. According to his analysis, this is because the Soviet government did not want to acknowledge "any liability for radioactive contamination of the environment in other countries" and hence it insisted that "the amount [deposited outside the Soviet Union] was negligible."220 Medvedev estimates that releases of radioiodine and radiocesium were about three times higher than the official estimates cited above.221
One of the most important, unanticipated features of the Chernobyl accident was ten-day duration of the fire, which was accompanied by a correspondingly long time during which large releases of radioactivity continued. As Medvedev points out, the modeling of nuclear power plant accidents generally assumes a single, short-term release of radioactivity. Weather conditions during such short releases can reasonably be assumed to be constant. As a result severe accidents are assumed to have a fallout trace that forms a single elongated, cigar-shaped pattern, much like the typical fallout pattern from a nuclear bomb explosion near ground level. This assumption is sometimes valid. It was, for instance, the pattern of radioactivity released as a result of the 1957 Soviet explosion in a tank containing highly radioactive waste. But it was not valid for the Chernobyl accident.
During the ten days of the fire, which was accompanied by huge releases of radioactivity, wind directions and the weather changed many times. As a result, large, widely scattered areas in many compass directions were affected. Rainfall in some areas during this prolonged period created hot spots of radioactivity in three states of the Soviet Union, now separate countries: Ukraine, Belarus, and Russia. Countries far beyond the Soviet Union were also affected. Europe was especially affected by the fallout, and levels of iodine-131 in milk exceeded officially permissible levels in many countries. Every country in the northern hemisphere received some fallout from the accident.
An "exclusion zone" 30 kilometers in radius was established and, after delays, 130,000 people were evacuated. Agriculture and commercial activities were also prohibited in the area. But the actual area that was contaminated and the number of people affected was far larger. There were hot spots as much as 100 to 300 kilometers from the accident that had radiation levels on the order of one thousand times above natural background. Long-lived biologically sensitive radionuclides, notably cesium-137 and strontium-90 were deposited in large quantities.
Iodine-131 concentrates in milk; when this milk is consumed, it concentrates in the thyroid glands, especially affecting children. After the iodine-131 decayed away in a few months (ten to twenty half-lives), milk produced in the contaminated regions continued to be affected by cesium-134 and cesium-137 contamination. The ill-effects of cesium-137 will last for a hundred years or more.222 There was a ban on open market milk sales in several regions, affecting 20 to 25 million people for more than a year after the accident.223 Even with these extensive measures, milk production was not halted in all contaminated regions. Some people in the most rural areas immediately around the plant consumed contaminated milk in the aftermath of the accident at a time when sales of such milk had been banned in Kiev. Cesium-137 contamination of milk will continue for many decades.
The region around Chernobyl consists largely of swamps and soggy forest land. Much of the land has been reclaimed for agricultural use, the dominant use at the time of the accident being cattle grazing. The prevalent ecological conditions are conducive to retention of cesium and to its rapid transfer to plants. As a result, agriculture was affected over a vast region. The most immediately affected area was the 30-kilometer radius exclusion zone in which 70,000 hectares (175,000 acres) of fields, grazing land, and vegetable and fruit gardens were abandoned. In June, there was a further evacuation of 113 villages outside the exclusion zone in Belarus and Ukraine. Between 100,000 and 150,000 hectares (250,000 to 375,000 acres) of agricultural land were abandoned.
Levels of cesium-134 and cesium-137 contamination are especially important as criteria for suitability for agricultural use. Medvedev estimates that "if international standards were being applied for the use of agricultural land, nearly one million hectares would be considered lost for a century, and about two million hectares would be lost for 10-20 years."224 There have been anecdotal reports of large increases in farm animals born with genetic defects. At one collective farm, 27 abnormal calves were born in the year after the accident while none had been reported in the five years preceding it. The number of suckling pigs with genetic defects increased from three cases in five years to 64 in one year.225
Most contaminated agricultural land continues to be used for farming. Indeed, many people who were evacuated from severely contaminated areas have returned to them due to economic problems in the areas to which they were relocated and the wish of many older people to live and die at home.
A large amount of agricultural produce in Europe had to be dumped due to contamination from fallout. For instance, most vegetables in the region around Munich were destroyed because they had become contaminated with iodine-131. The southern portion of the former West Germany was more contaminated than the rest of it. There were also severe restrictions on agricultural activities, including sales of meat from three million sheep and lambs in northwestern England and the neighboring portions of Scotland and northern Wales, which were affected by rain-out of radioactivity when the fallout cloud passed over them.
Health Effects
Several categories of people have been and will be affected adversely by radiation doses from the Chernobyl accident:
The assessments of adverse health effects from the accident have varied widely. Official reports have tended to concentrate on the 31 workers who died of severe radiation exposure. But this attitude ignores the far greater numbers of people who were exposed to considerable levels of radiation and who became ill in the months and years that followed the accident and who have an elevated risk of various radiogenic diseases in the years to come. It also does not take into account the effects of the accident for decades to come.
One complicating factor in assessing the health risks due to the accident has been the severe deterioration, bordering in many areas on collapse, of social services, including health delivery services in the former Soviet Union. As a result, the increases in diseases and death due to radiation exposure are mixed up with those arising from the general deterioration in medical care and economic conditions.
Some indication of the potential health damage can be obtained by looking at the radiation doses. The range of exposures of the people who lived in the exclusion zone was generally of the same order of magnitude as the survivors of Hiroshima and Nagasaki -- that is, about one rem to several tens of rems external gamma radiation. In addition, people were exposed to beta radiation and internal doses from various radionuclides such as iodine-131 and cesium-137. The officially estimated cumulative population dose for the 135,000 people who were initially evacuated (with delays) is estimated at 1.6 million person-rem. Applying a risk factor of 0.0004 cancers per person-rem to this dose yields an estimate of 640 fatal cancers.226
Medvedev has pointed out that the official dose estimate includes only external radiation. It does not include doses from consuming contaminated food, such as milk continuing cesium isotopes and iodine-131. It is now clear that internal exposures are a significant factor in long-term effects of the accident. Thyroid diseases, including thyroid cancer in children, generally attributed to the consumption of milk contaminated with iodine-131, have registered huge increases in the fallout areas. Ten to one hundred-fold increases in thyroid cancer among children in the affected region have been reported.227 Over the decades tens of millions of people will have been put at significantly increased risk, and it is reasonable to assume that many will die as a result. The poor state of both medical monitoring as well as curative medicine in the former Soviet Union means that medical systems are not likely to record many of these deaths as having been related to the Chernobyl accident. But that cannot negate the documented magnitude of the immense contamination and risk to which the present and future generations living in tens of thousands of square kilometers of highly contaminated land are being, and will continue to be, exposed.
The number of deaths from increased exposures even in the far off contaminated regions in the European Community (EC) are projected to be large. The British National Radiation Protection Board estimates that up to 1,000 additional cancer deaths will occur in the EC region due to radiation doses from radiocesium and iodine-131. Medvedev considers this a "minimal assessment."228
Medvedev has cited the entire range of estimates for cancer death estimates that have been made. The lowest estimates are 200 to 600 additional cancer deaths in the former Soviet Union, while the highest estimate is 280,000 additional cancer fatalities worldwide.
These estimates do not include adverse health effects on workers and soldiers who were the clean-up crews and hence among the most severely affected. There are no systematic records of their exposure or even of how many of them were involved. Medvedev quotes an eyewitness account of the working conditions of the soldiers who did the clean-up work in the immediate aftermath of the accident:
I saw soldiers and officers picking up graphite [ejected from the reactor core by the explosion] with their hands...There was graphite lying around everywhere, even behind the fence next to our car. I opened the door and pushed the radiometer almost onto a graphite block. Two thousands of roentgens an hour...Having filled their buckets, the soldiers seemed to walk very slowly to the metal containers where they poured out the contents, You poor dears, I thought, what an awful harvest you are gathering... The faces of the soldiers and officers were dark brown: nuclear tan.229Medvedev estimates that the radiation tan on the soldiers' faces indicates skin doses of 400 to 500 rem, that many of them suffered from acute exposures, and that some died as a result. No records have been kept, or at any rate, made public, of the numbers of soldiers involved in such activities or of their exposures.
Large numbers of workers were also exposed to high levels of radiation in the years that followed when a concrete "sarcophagus" was built around the burned out reactor building to try to encase the radioactivity. Two hundred thousand men, working very short shifts, were involved in its construction. The radiation levels were extremely dangerous, with the most radioactive areas measuring between 5,000 and 20,000 rads per hour. The sarcophagus was built in the hope that it would contain the radioactivity for an extended period. But it has already deteriorated considerably and new measures to contain the radioactivity appear to be necessary. There is no consensus on the appropriate approach to contain the enormous amount of radioactivity in and under the building, but whatever measures are taken, they will be costly. If measures are not taken, the costs, in terms of contamination of important sources of water supply of the region, could be far higher.
The overall costs of the Chernobyl accident are so vast and extend over so many generations that they are impossible to calculate. The official calculation of 8 to 11 billion rubles (1988 rubles), or roughly ten to fifteen billion dollars. But any evaluation is complicated by the fact that a large number of clean-up workers are neither being followed nor treated. It is also very difficult to quantify the economic and social losses caused by the uprooting of hundreds of thousands of people. Further, the high radiation doses received by many mean that problems other than cancer are also likely to occur. For instance, diseases induced by the weakening of immune systems of clean-up workers and off-site populations who received high radiation doses could cause large health and economic impacts. But, given the state of the health delivery systems, they would be difficult or impossible to detect. Finally, the negative impact of Chernobyl on the electricity systems of the former Soviet Union is still being felt and enormous costs loom in terms of preventing the spread of radioactivity from the reactor, preventing accidents at other reactors of the same design, and replacing reactors generally considered to be unsafe well before their design lifetimes. The costs of replacing electric generating capacity not provided by RBMK reactors, which are generally considered to be far too dangerous in the West, could by itself run into tens of billions of dollars.
Some Lessons of the Chernobyl Disaster
The most important and tragic lesson of the Chernobyl accident is the most severe kind of nuclear power accident can actually happen. Nuclear power technology is unforgiving. It has often been stated by proponents and opponents alike that it does not allow room for mistakes. Design, management, and operator errors have typically combined to yield accidents; in many cases, these same features have also helped limit the damage. In the case of Chernobyl, the factors propelling the situation towards a major accident completely overwhelmed any checks in the system.
It is generally agreed that accidents on the scale of Chernobyl or worse are more probable in the Former Soviet Union and Eastern Europe, but they are also possible elsewhere. That potential has been demonstrated events such as the 1979 Three Mile Island accident and the British Windscale reactor fire in 1957. The scale and the irremediable nature of the damage from Chernobyl leads to a crucial question: is it possible to design nuclear reactors that would not be subject to accidents of such catastrophic magnitude? This is not the same as ruling out all accidents, which is clearly impossible with any technology. It is merely to ask whether the damage can be limited so that it is at least remediable in its worst aspects.
As we have discussed, current nuclear power plant designs do not meet this goal. LWRs, graphite-moderated reactors, or sodium-cooled reactors in the West all have vulnerabilities in design and/or operation that could lead to severe accidents. The record shows that the probabilities of catastrophic accidents are lower in the West than in the former Soviet Union. But this is an inadequate response, given the nature of the consequences and the fact that energy alternatives that would avoid catastrophic accident potential are available.
We can grant that the safety of nuclear power plants in the United States has improved over the decades, as public vigilance and the Three Mile Accident have forced the manufacturers to conform to stricter safety standards. However, these efforts cannot negate the fact that current power reactor designs are vulnerable to catastrophic accidents. Chernobyl demonstrates that the effects of such accidents are as devastating as they are irremediable. In this context it is well to recall a criticism of nuclear power plant safety efforts made by Nobel laureate physicist, Hannes Alfven, in 1972:
The reactor constructors claim that they have devoted more effort to safety problems than any other technologists have. This is true. From the beginning they have paid much attention to safety and they have been remarkably clever in devising safety precautions. This is...not relevant. If a problem is too difficult to solve, one cannot claim that it is solved by pointing to all the efforts made to solve it.230
Acknowledgments
Summary and Recommendations
A. Main Findings
B. Recommendations
Other Recommendations
PART I -- HISTORY: NUCLEAR POWER PROPAGANDA AND REALITY
Chapter 1: Romance with the Atom
Chapter 2: Electricity Production and Nuclear Reactors
A. Nuclear Fuel
1. Uranium Fuel
2. Plutonium Fuel
B. Nuclear Reactors
1. Thermal Reactors
2. Breeder Reactors (Fast Neutron Reactors)
C. The "Nuclear Fuel Cycle"
Chapter 3: The Early Years -- Atomic Messiahs, Propagandists, and Skeptics
A. Atomic Messiahs and Propagandists
1. "Atoms for Peace"
B. Atomic Skeptics
1. Early Practical Assessments
Chapter 4: Plutonium, the Nuclear Navy, and Nuclear Power Development
A. Round One: Dual-Purpose Reactors
B. Round Two: Admiral Rickover, the Nuclear Navy, and the Light Water Reactor
1. Propaganda Aspects
2. Shippingport
C. Other Skeptics
Chapter 5: From "Too Cheap" to Bust
A. The First Civilian Reactors
B. Safety
1. Reactor Safety Basics
2. Light Water Reactors -- Basics about Loss of Coolant Accidents
3. Historical Aspects of the Light Water Reactor Accident Debate
4. Sodium-Cooled Fast Breeders
C. Cost
1. Cost -- the 1950s to the 1970s
2. Cost: The 1980s and early 1990s
Chapter 6: Radioactive Waste
A. Radioactive Waste Basics
1. Waste categories
2. Quantities of weapons-usable materials
B. High-Level Waste Management: Short- and Medium-Term Issues
1. Nuclear Waste and Nuclear Power
2. Reprocessing
C. Long-Term Management Issues
Concluding Observations
PART II -- MORE NUCLEAR POWER PLANTS OR A SOUND ENERGY POLICY?
Chapter 7: "Inherently Safe" Reactors: Commercial Nuclear Power's Second Generation?
A. New Reactor Designs -- Overview
B. New Light Water Reactor Designs
C. Other Reactor Designs
1. The MHTGR
D. The Semantics of "Inherent Safety"
E. Accidents and Nuclear Technology
1. Chernobyl
2. Some Lessons of the Chernobyl Disaster
Chapter 8: Plutonium Disposition, Military Tritium, and Commercial Reactors
A. Plutonium Disposition
B. Military Tritium
C. Concluding Observations on the Civilian-Military Nuclear Power Connection
Chapter 9: Nuclear Power and Energy Policy
A. Energy Concepts
B. Renewable Energy Sources
C. Integrating Renewables with Energy Efficiency in the Electricity Sector
1. Obstacles to Efficiency
2. A Proposal for a Financing Structure
3. Improving Efficiency in Existing Large Buildings
4. Improving Efficiency in Existing Small Buildings
5. Other Measures
Appendix A: Basics of Nuclear Physics and Fission
A. Structure of the Atom
B. Radioactive Decay
C. Binding Energy
D. Nuclear Fission
E. Fertile Materials
Appendix B: Uranium
A. The Mining and Milling Process
B. Conversion and Enrichment
C. Regulations in the U.S.
D. The Future
Appendix C: Plutonium
A. Nuclear Properties of Plutonium
B. Chemical Properties and Hazards of Plutonium.
C. Important Plutonium Compounds and Their Uses
D. Formation and grades of Plutonium-239.
Glossary
References
Institute for Energy and Environmental Research
Revised May 9, 1996
(Chapter 7 posted September 11, 2001; revised May 29, 2009)