Addendum 1 to CSER 96-025: PFP storage of 9.25/9.5 inch tall, 4.4 kg Pu cans on existing Vault 4 pedestals

A nuclear criticality safety analysis has been performed to increase the approved plutonium mass limit for cans stored in Vault number-sign 4 cubicles at PFP. The original CSER 96-025 accommodated the storage of 4.4 kg of plutonium in PuO, (5.0 kg PuO,) in Vault number-sign 4 by requiring that half the cubicles be left vacant. This addendum allows for all the cubicles to be used, but with a fissile plutonium mass limit of 58 kg per cubicle. A mass limit for each cubical allows for storage of a larger number of cans if some have less than the 4.4 kg Pu limit per can. The highest k., calculated is 0.932 + 0.003 when an overbatched can is present in every fourth cubicle. This is below the criticality safety limit of kff 0.935, and consequently, an increase of plutonium mass to 4.4 kg per can is within acceptable safety limits for the given mass limit