Criticality safety assessment of tank 241-C-106 remediation

Abstract

The s u b j e c t document contains t h e a n a l y s i s t o support t h e p o s i t i o n paper and t h e c r i t i c a l i t y review team r e p o r t on c r i t i c a l i t y s a f e t y issues associated w i t h the r e t r i e v a l CRITICALITY SAFETY ASSESSMENT OF TANK 241-C-106 REMEDIATIONE x p e r t C r i t i c a l i t y T e a m A u t h o r s : i WHC-SD-W320-CSA-001 REV 0 ACKNOWLEDGEMENTS The authors o f t h e r e p o r t would l i k e t o acknowledge t h e c o n t r i b u t i o n and a s s i s t a n c e p r o v i d e d by D r . Rowland F e l t from t h e U.S. Department o f Energy (EH-34).I n a d d i t i o n t o being a r e p o r t author, Dr. F e l t a l s o arranged a DOE independent r e v i e w o f t h e s a f e t y a n a l y s i s document t o ensure peer r e v i e w and t e c h n i c a l c r e d i b i l i t y . The independent r e v i e w team members are a l s o acknowledged f o r t h e i r t i m e and e f f o r t t o r e v i e w t h e document. Independent The team notes that in order for a neutronic criticality to be possible, the plutonium concentration in an infinite volume of waste must exceed 2.6 g Pu/L. Numerous layers of conservatism are built into this minimum fissile concentration, including optimal neutron moderation (i.e., optimal water moisture content), a waste medium containing a small fraction of the neutron absorbers actually present, and an infinite geometry. Since the maximum concentration of plutonium measured in either donor tank 241-C-106 or receiver tank 241-AY-102 was 0.13 g Pu/L, a plutonium concentration increase of at least 20 would be necessary to achieve criticality under the most ideal possibility of achieving such a scenario is highly unlikely.geometries would be considerably less reactive. The physical More realisticThe important message is that all of the "gates" illustrated in

Chemical and chemically-telated considerations associated with sluicing tank C-106 waste to tank AY-102

“…In evaluating the potential for nuclear criticality related to the transfer of the contents of tank C-106 to tank AY-102, the stability constants for plutonium oxyhydroxide precluded significant solubilization of plutonium by the small amounts of complexants in tank AY-102 (Waltar 1996). CR-SubTAP was concerned with whether there is a criticality issue.…”

“…These results are reported in Tables 7-1 and 7-2. These results are being evaluated by WHC's nuclear criticality experts and will be reported in the final version of Waltar (1996).…”