Institute for Energy and Environmental Research
However, the spent fuel pools will not be capable of accommodating all spent fuel expected to be produced. The many delays (discussed further below) in the promised repository date have made it inevitable that additional onsite or other interim storage will be needed for some spent fuel from most nuclear reactors. The primary technology being considered today is the use of dry storage casks located either at a centralized Monitored Retrievable Storage (MRS) facility, or locally at each reactor site.
Centralized Away-From-Reactor Interim Storage at MRS
The 1982 Nuclear Waste Policy Act (NWPA) required the DOE to prepare a proposal for the construction of a Monitored Retrievable Storage (MRS) facility. The stated purpose of such an MRS facility would be to receive and prepare irradiated nuclear fuel from commercial reactors for temporary storage (in dry storage containers) before final disposal in a geologic repository.29
Part of the purpose of the MRS system was to allow the DOE to accept waste for storage up to eight years in advance of the opening of a permanent repository. It could therefore reduce the need for utilities to expand temporary waste storage facilities at nuclear plant sites.30
This ability to reduce utility needs to build expanded storage -- an entirely self-serving reason benefitting primarily nuclear utilities -- is, however, as discussed below, the only clearly identifiable motivating reason to build an MRS in the system as currently envisioned.
Nonetheless, the 1987 amendments to the NWPA formally authorized the MRS, but also imposed a number of restrictions on its development which linked it to the opening of a permanent repository. These restrictions were the result of fears that an MRS could become a de facto permanent storage site. This concern has been one of the most consistently voiced criticisms of the MRS. The concern is that once it is constructed, an MRS is likely to become a substitute for a repository, thereby removing necessary governmental incentive for the development of long-term solutions to the nuclear waste problem.
In addition, there appears to be no other overall advantage to building an MRS. There is no cost advantage, and in fact there are recognized system cost disadvantages that are acknowledge by the DOE. The DOE's own cost estimates, over a range of scenarios and repository availability dates, indicate that an MRS will result in cost increases for all scenarios considered. These MRS-related cost increases range from $1.7 billion to $2.2 billion.31 The MRS Review Commission's own study, mandated by the 1987 amendment to the 1982 Nuclear Waste Policy Act, which included consideration of increased costs for storage at shut-down reactors not considered by the DOE, found that in all scenarios considered but one, MRS would still increase nominal constant-dollar costs by up to $2.2 billion. In only one case, introducing an MRS in the overall waste management system was found to result in an $800 million savings, but even these savings were reversed in favor of a $500 million increase when the Review Commission discounted all costs to present value.32
Regarding risks due to transportation of spent fuel, the study by the MRS Review Commission found no significant difference between the MRS and No-MRS scenarios. However, this assessment is highly dependent on the location of the eventual repository with respect to the MRS because overall transportation requirements will depend on that. The Nuclear Waste Policy Act prohibits location of an MRS in the same state as a candidate repository site.
Extended onsite storage will actually considerably decrease transportation risk for two reasons. First, the quantities of cesium-137, strontium-90, and plutonium-241, among the most dangerous radionuclides, will greatly decrease due to radioactive decay, reducing accident consequences. Second, extended onsite storage will allow time for better casks to be developed, thereby further reducing risks of accidental radioactivity releases.
Regarding overall system risks, including occupational, public, and environmental effects, the Commission found that "the differences in risks among the alternatives considered are so small that they do not provide a basis for discriminating between MRS and No-MRS alternatives."33
Despite these issues, the DOE is still planning to build an MRS, and the administration is currently supporting energy policy legislation that includes an abolition of the schedule linkages between an MRS and a repository.
One of the driving incentives for the DOE appears to be a consequence of DOE's interpretation of the 1998 target date for repository opening contained in the 1982 law. The DOE used this date as a basis to enter into contracts with some utilities to take the spent fuel off their hands at this date. With the subsequent delay of the repository timetable by at least 12 years, this leaves the DOE with an obligation to take the spent fuel, but no place to put it, unless an MRS is built.
Demonstrating the frustration and exasperation of some utilities with the lack of progress and the delays in the waste program, a utility executive recently said at a DOE-sponsored meeting that he wanted the government to take charge of the spent fuel by 1998 and "I don't care where you put it."34
Onsite Interim Storage in Dry Casks
Dry cask storage, which would be used at an MRS, can also be used as an alternative method (to the use of irradiated fuel pools) of storing irradiated fuel rods at reactor sites. It can be accomplished in various types of casks, modules, or vaults located outside the pools.35
Dry casks have several potential advantages over storage in water pools. First, since they do not contain water, which is necessary to enable a nuclear reaction in light water reactors, there is no chance of an accidental chain reaction, as there would be in water storage pools.36 Second, since there is no water circulation and filtering, no "low-level" radioactive waste is produced by fuel storage, as is continually the case in the fuel pools. However, there are likely to be some decommissioning wastes as with other nuclear facilities. Third, since dry-cask storage systems are, for the most part, self-contained, with no mechanical pumps or other active systems, the maintenance of safety relies passively on the cask integrity.
Dry casks do pose their own dangers, as is to be expected. For example, the DOE notes that "rough handling" could result in the release of "small quantities" of gaseous radionuclides from the storage casks.37 Dry casks also do not eliminate hazards which may result from earthquakes. It is not feasible to expect complete safety when dealing with the extreme hazard represented by the intense radioactivity of irradiated fuel no matter what the storage technology, but using a passive dry storage system is better than having to rely on active mechanical systems that can wear out, malfunction or break down.
Dry storage is currently in use at two nuclear plants under the auspices of a DOE-utility cooperative demonstration program authorized by the Nuclear Waste Policy Act of 1982. The NRC granted licenses in 1986 to the Virginia Power Company for dry storage in metal casks at its Surry nuclear plant near Gravel Neck, Virginia, and to the Carolina Power & Light Company for the use of horizontal concrete modules at its H.B. Robinson plant near Hartsville, South Carolina. Both of these plants have loaded irradiated fuel into their dry storage systems. Dry storage in horizontal concrete modules was also licensed at Duke Power's Oconee plant near Seneca, North Carolina in 1990. License applications for spent fuel dry storage facilities are under review for the following five plants as well:38
| Plant | Utility | Location |
|---|---|---|
| Calvert Cliffs | Baltimore Gas & Electric | Annapolis, MD |
| Brunswick | Public Service of Colorado | Southport, NC |
| Ft. St. Vrain | Northern States Power | Denver, CO |
| Prairie Island | Northern States Power | Minneapolis, MN |
| Palisades | Consumer Power Company | South Haven, MI |
There does not seem to be any reason why this form of storage at reactor sites cannot be expanded to accommodate anticipated future spent fuel generation, even in the absence of an MRS or repository in the near term. Indeed, the NRC has recently finalized regulations which essentially encourage such expansion (as long as certain pre-approved cask designs are used) by relaxing previously existing licensing requirements which applied to dry casks.39 And in considering both the pools and the dry cask option, the NRC has stated that it considers onsite storage to be safe for at least an interim period of 100 years.40 Of course, careful monitoring should accompany any expansion, since the technology is still relatively new.
It is important to note that dry storage on site does not eliminate the need for spent fuel pools altogether, since recently discharged fuel is so hot, it must be cooled in wet pool storage for one year or more before it can be placed in dry storage.
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Last Updated October, 1996
29. GAO 1986b, p. 4.
30. GAO 1988a, p. 4.
31. DOE, cited in MRSRC 1989, p. 65. Costs are in 1989 dollars.
32. MRSRC 1989, p. 73. The MRS Review Commission used a discount rate of 4 percent. See footnote 19 in Chapter 4 for an explanation of cost discounting.
33. MRSRC 1989, pp. 52, 45.
34. Comments of a nuclear utility executive at the January 15-16, 1991 DOE-sponsored meeting on strategic principles for high-level waste management. The meeting was open to the public and the comments could be cited, but the ground rules were that the participants were not to be named.
35. DOE 1989d.
36. With current U.S. nuclear fuel designs, water is used to moderate the neutrons, thereby allowing the nuclear chain reaction to continue. If there is no neutron moderation, there cannot be an accidental criticality.
37. DOE 1989d, p. I-95.
38. NRC 1991, p. 61; and Harvey 1991, p. 16.
39. NRC 1990, pp. 29181-29195.
40. NRC 1989a, p. 39767.