A study proposed by the Electric Power Research Institute (EPRI) could shed more light on how safe it is to store high-burnup used nuclear fuel in dry casks.
In an August 2013–released draft test plan developed by the research institution for the Department of Energy (DOE)–sponsored study, EPRI proposes using a specially instrumented dry storage cask to monitor conditions and changes to high-burnup used fuel stored for a test period of a decade or more.
The plan calls for a Transnuclear TN-32 demonstration cask and fuel, supplied by AREVA and Westinghouse, to be placed at the independent spent fuel storage installation (ISFSI) at Dominion Virginia Power’s North Anna nuclear energy plant. However, Dominion Virginia Power (which is part of the EPRI team) must first secure a license amendment request for the existing ISFSI from the Nuclear Regulatory Commission (NRC) by 2015 for the test cask to be loaded by July 2017, as planned. Measurements of conditions inside the cask and the state of the stored fuel at the end of the storage period will be compared with data on about two dozen “sister” fuel assemblies examined at the beginning of the test. The DOE, meanwhile, has sought comments from public stakeholders to ensure project resources are invested wisely.
The project is part of efforts that are gaining more urgency to demonstrate the ability to safely store—for many decades—and then transport spent nuclear fuel (SNF). The U.S. has stored lower-burnup SNF of less than 45 GW-days per metric ton uranium since 1986 in dry casks (Figure 3), but dry storage of high-burnup SNF has been more recent. About 200 dry storage casks (out of more than 1,700 nationwide) were loaded with at least some high-burnup SNF as of December 2012. “Furthermore, almost all SNF being loaded in the U.S. is now high burnup,” EPRI points out. “Thus, industry needs data on high burnup SNF under typical conditions.”
EPRI’s planned test would update the results of a similar study, concluded by the Idaho National Laboratory (INL) in 1999, that examined fuel with characteristics that were typical at that time, the Nuclear Energy Institute notes. “Since that study, the industry increasingly has been able to extract more energy from nuclear fuel by operating reactors at higher power levels and by using longer cycles between refueling. The resulting higher-burnup used fuel is both more radioactive and hotter.”
But another reason the study is important is a continuing need for a permanent solution for the disposal of used nuclear fuel from reactor sites, “which makes it more likely that fuel is stored in dry casks for periods longer than the original 20-year license,” the nuclear industry group said. “Based on the INL study and other information, the NRC in 2011 revised its used fuel storage regulations (10 CFR Part 72) to increase the licensing period for dry casks to 40 years with the option for additional renewals of up to 40 years.”
EPRI said the data obtained from the test could also help answer NRC requests for information from applicants for dry storage license extensions on the condition of high-burnup SNF after the initial 20-year license period.
—Sonal Patel, associate editor (@POWERmagazine, @sonalcpatel)