SPENT FUEL INTERIM STORAGE WITH NUHOMS® HSM MATRIX

摘要

In the United States, used fuel assemblies dischargedfrom nuclear power plants (NPPs) have historically beenstored on-site using licensed dry storage systems. Due toshutdown/decommissioning of several NPPs and delays inthe implementation of the geological repository, there is aneed to develop solutions to manage the storage of drystorage systems in interim storage facilities.The centralized interim storage facility (CISF)functions as an intermediate repository/staging area fordry storage systems for an extended duration of time priorto eventual transportation to a geological repository. Theoperation of a CISF will lead to a significant reduction inthe number of independent spent fuel storage installations(ISFSIs) nationally and enable release of space in thosedecommissioned reactor sites that currently only maintaintheir respective ISFSIs.The NUHOMS® System has been licensed in theUnited States for the on-site storage of used nuclear fuelfor more than 35 years. The system consists of a dryshielded canister (DSC) containing the used nuclear fuelwhich is inserted into the concrete horizontal storagemodule (HSM) using a transfer cask. Several DSCsdesigns have been licensed for storage and arecharacterized by differences in physical dimensions(diameter, length), allowable used fuel contents (BWR,PWR), performance parameters (heat load, burnup).The NUHOMS® MATRIX is an evolutionary design ofthe storage module that will provide for a two-tieredplacement of DSCs resulting in improved storageefficiency, stability and self-shielding. The design of theMATRIX ensures that it is able to house the various DSCdesigns and therefore, serve as a universal over-pack.Managing the effects of aging of the structures, systems,and components associated with dry storage is therefore,an important aspect of the extended interim storage ofused fuel. The CISF approach to dry storage offers asignificant advantage wherein an aging managementprogram can be effectively and uniformly implemented fora wide variety of currently licensed dry storage systems.The paper provides additional insights into designand licensing of the MATRIX in a CISF with an objectiveto be employed as a universal storage over-pack forvarious DSC types. The suitability of the MATRIX foreffective aging management of spent fuel canisters forlong-term interim storage is also discussed herein.