Status and future for ANSI/ANS-5. 1 decay heat power in light water reactors

This standard, issued in 1979 sets forth values for the decay heat power from fission products and [sup 239]U and [sup 239]Np following shutdown of light water reactors containing [sup 235]U, [sup 238]U, and plutonium. The decay heat power from fission products is presented in tables and equivalent analytical representations. Methods are described that account for the reactor operating history, for the effect of neutron capture in fission products, and for assessing the uncertainty in the resultant decay heat power. Equations for the decay heat power from the decay of [sup 239]U and [sup 239]Np are presented separately. It represents a significant improvement over the previous Draft' standard issued in 1973. Future improvements in the standard will focus on including the recent integral experiment results with summation calculations using the soon-to-be-released Evaluated Nuclear Data File (ENDF/B-VI) fission yield and fission product decay data tapes.