Design and safety basis sludge characterization from exposure-adjusted radioisotopic source terms for N reactor fuel stored at K-East and K-West basins

The Safeguards and Accountability database was used as the primary source document for exposure data for spent N Reactor fuel stored at the K-East and K-West basins. This database is a listing of all keys (ie., groups of fuel discharged from the reactor at the same time), and the exposure for that key, mass of uranium in the key, fuel type (whether Mark IV or Mark IA), and several other parameters. There are nearly five hundred records (keys) in this database. Figure 1 illustrates an N Reactor Mark IV fuel assembly. The axial length of the endcap is approximately 0.19 inch. Mark IA and Mark IV fuel are low enriched zircalloy-2 clad metallic uranium tube-in-tube assemblies held together with spacers and clips. Unexposed Mark IV fuel assemblies have an enrichment of 0.947 wt% 235U in both inner and outer tubes. Unexposed Mark IA assemblies have an enrichment of 1.25 wt% 235U in the outer tube and 0.947 wt% 235U in the inner tube