Integral Decay-Heat Measurements and Comparisons to ENDF/B-IV and V

Results from recent integral decay-power experiments are pre sented and compared with summation calculations.The experiments include the decay power following thermal fission of U, U, and 239Pu.The summation calculations use ENDF/B-IV decay data and yields from Versions IV and V. Limited comparisons of exper imental 6 and y spectra with summation calculations using ENDF/B-IV are included.Generalized least-squares methods are applied to the recent U and Pu decay-power experiments and summation calculations to arrive at evaluated values and uncertainties.Results for 235U imply uncertainties less than 2% (1 a) for the "infinite" exposure case for all cooling times greater than 10 seconds.The uncertainties for 239Pu are larger.Accurate ana lytical representations of the decay power are presented for 2 3 5,2 38y^ 239pu for uge iight_water reactors and as the nominal values in the new ANS 5.1 Draft Standard (1978).Compar isons of the nominal values with ENDF/B-IV and the 1973 ANS Draft Standard in current use are included.Gas content, important to decay-heat experiments, and absorption effects on decay power are reviewed.