Criticality Safety Evaluation Report for the Multi-Canister Overpack

Abstract

Ila. ModificationHNF-SD-SNF-CSER-005 REV 5 . . 4-7 LIST OF TABLES. . 4-9. 4-10. 4-11. 4-12. 4-13. 4-14. . . 5-75-8 5-95-10 HNF-SD-SNF-CSER-005 REV 5 CRITICALITY SAFETY EVALUATION REPORT FOR THE MULTI-CANISTER OVERPACK INTRODUCTION AND SUMMARY OF LIMIT AND CONTROLSThis criticality safety evaluation report (CSER) addresses the criticality analysis for spent nuclear fuel (SNFjinside a multi-canister overpack (MCO). The results reported in this revision of the CSER have been upgraded to incorporate the basket designs from HNF-S-0426, Performance Specification for Spent Nuclear Fuel Multi-Canister Overpack (Goldmann 1998). OVERVIEWSNF w i l l be removed from existing canisters in both the K East and K West Basins, washed, sorted, loaded into baskets, and the baskets loaded into MCOs. Since the majority of the.SNF consists of spent N Reactor fuel, the basket designs are based on the Mark IV and Mark IA fuel assemblies.A fraction of the fuel inventory is damaged or corroded and does not closely resemble fuel elements. This fissionable material is referred to as scrap. Scrap materials, and any additional scrap that may be generated during the fuel retrieval process, will be loaded into scrap baskets. Normally, Mark IV fuel scrap will be placed in Mark IV scrap baskets and Mark IA fuel scrap in Mark IA scrap baskets. Some single pass reactor (SPR) fuel also is stored in canisters in the K Basins. This fuel will be loaded into modified Mark IA baskets and loaded into an MCO that contains no other fuel type.Baskets containing fuel or scrap are loaded into the MCO by the MCO loading system in the K Basins. An MCO can contain either six Mark IA baskets or five Mark IV baskets. Mark IA and Mark IV baskets are not mixed in the same MCO. Each MCO may be loaded with all fuel baskets, one scrap basket with the rest of the baskets being fuel baskets, or two scrap baskets with the rest being fuel baskets. By design, a Mark IA fuel basket may contain a maximum of 48 fuel assemblies, and a Mark IV basket may contain a maximum of 54 fuel assemblies.Once the MCO has been loaded with baskets of fuel and scrap, it is sealed and the cask-MCO removed from the K Basin pool, the lid installed on the shipping cask, and the cask-MCO secured to a transporter. The cask-MCO is then taken to the Cold Vacuum Drying Facility ( O F ) where the water inside the MCO is removed. The dry cask-MCO is taken to the Canister Storage Building (CSB), and the MCO is removed from the cask. A cover cap is welded into place on top of the MCO, and the sealed MCO is then inserted into a tube in the CSB vault for interim storage, Some MCOs are monitored and will not have a welded cover cap installed until the monitoring campaign has been completed. CSER-OOS.RS 1-1 odoba 1999HNF-SD-SNF-CSER-005 REV 5The fissile materials in the K Basins that are to be put into the MCO baskets exist in different forms. These forms include whole fuel assemblies, parts of fuel assemblies (scrap), and oxides of corroded fuel. The terms used in this report to describe each modeling catego...