In 2010, EPRI performed a study of the accelerated transfer of spent fuel from pools to dry storage in response to the threat of terrorist activities at nuclear power plants (report 1021049). Following the March 2011 Great East Japan Earthquake and the subsequent accident at the Fukushima Daiichi nuclear power plant, some organizations issued a renewed call for accelerated transfer of used fuel from spent fuel pools (SFP) to dry storage. Their reasoning was that this would lessen the potential consequences from a loss-of-spent-fuel cooling accident by decreasing the heat load and source term available for release. This report revises the 2010 study to evaluate the dose and cost impacts of accelerating transfer of used fuel from SFPs to dry storage for two scenarios—one taking 10 years to transition the removal of all fuel cooled for at least five years, and the other taking 15 years to complete the transition.
EPRI report 1021049 did not assess the amount of decay heat and radionuclide source term reduction in SFPs due to lower numbers of used fuel assemblies in the pools. As cesium-137 (Cs-137) is one of the dominant radionuclides contributing to land contamination in some areas around the Fukushima Daiichi plant, EPRI has now included assessments of the potential reduction in decay heat and source term from Cs-137 and Cs-134 inventory resulting from accelerated off-loading of used fuel out of SFPs.
The 2010 report assumed the transition of five-year cooled fuel could be accomplished in five years. Industry feedback indicated a more realistic time frame is 10 to 15 years. Key objectives were to revise the report using the more realistic transition time and taking into account new assessments of decay heat and source term.
Cost and dose estimates are determined for a representative PWR, BWR, new plant, and the industry as a whole. The report includes a detailed review of assumptions impacting evaluations for areas ranging from fuel inventory, decay heat, and source term to impacts on cask capacity, design, and fabrication. Operational limitations such as the availability of SFPs and cask handling equipment have been taken into account in the two scenarios.
The accelerated transfer of used fuel to dry storage would have significant radiological impacts due to loading fuel with higher decay heat and higher dose rates and to loading more packages. The increase in worker dose for the U.S. nuclear industry as a whole is estimated at 1650 and 2090 person rem for the 10-year and 15-year transition for five-year cooled fuel, respectively. The estimated increase in worker dose is 6 to 21 person-rem for a representative PWR plant, 11 to 12 person-rem for a BWR plant, and 65 person-rem for a new plant.
The economic impact for the U.S. nuclear industry of accelerating dry storage is estimated to be $3.5 to $3.9 billion. Costs included are associated with procurement of dry storage cask systems (DSCs), cask loading operations, dry storage facility construction and/or expansion, and annual operation and maintenance. The cost estimations use more realistic assumptions associated with increased DSC costs to account for 1) high burnup, short-cooled spent nuclear fuel, 2) impacts of increased annual demand for DSC manufacturing, and 3) licensing changes.
Accelerating the transfer of fuel to dry storage for all fuel cooled more than five years would reduce pool inventories by an estimated 67% to 78% for a PWR plant and 73% to 78% for a BWR plant. This transfer would decrease the decay heat remaining in the pool by an estimated 23% to 32% for a PWR plant and 32% for a BWR plant. The corresponding reduction in potential source term from cesium is estimated to be 43% to 53% for a PWR and 47% to 48% for a BWR.
Applications, Value, and Use
It is unclear whether the potential risk reduction due to lower amounts of decay heat and cesium in the SFPs would offset the real increase in risks, occupational safety hazards, operational impacts, and costs associated with a policy decision to transfer SNF from SFPs at an accelerated rate. This report will prove useful as decision makers in the nuclear industry examine the impacts and benefits of transferring spent nuclear fuel from SFPs to dry storage.