Subcritical Limits for Plutonium Systems

As a contribution to a required review of American National Standard for Nuclear Criticality Safety in Operations with Fissionable Materials Outside Reactors, limits for plutonium systems have been recalculated to confirm their subcriticality under the stated conditions or to propose other values. Additional limits were calculated for Pu(NO₃)₄ solutions that allow credit for the presence of ²⁴⁰Pu. Limits were calculated for PuO₂. Three methods were used to calculate limits for aqueous solutions. Only the two S_n methods were applied to metal and oxide. The validity of each was established by extensive correlation with critical experiments, and in some cases with experiments performed subsequent to the original limit calculations.