INTEGRAL DETERMINATION OF THE BETA AND GAMMA HEAT IN THERMAL-NEUTRON-INDUCED FISSION OF ^{235}U AND ^{239}Pu, AND OF THE GAMMA HEAT IN FAST FISSION OF ^{238}UThe Studsvik Neutron Research Laboratory University of Uppsala 61182 NYKÖPING SWEDEN Decay gamma energy and beta energy release rates for thermal neutron fission of ^{235}U and ^{239}Pu and the gamma energy release rates from ^{238}U for neutrons of 2.3 MeV have been measured by integral measurement. The gamma-rays and beta-rays were measured separately in different spectroscopic measurements. Absolute values have been obtained for the ^{235}U gamma energy over the time range 10 s to 1500 s and beta-energy from 10 s to 10^{4} s and for ^{239}Pu gamma- and beta-energy from 10 s to 10^{4} s time, and for ^{238}U gamma energy from 50 s to 10^{4} s cooling time. The accuracy of the data is better than 7 %. Summation calculations for the beta-energy release rates from ^{235}U and ^{239}Pu agree within a few % over the entire time range. Summation calculations gives systematically lower gamma energy at short cooling time. For cooling times around 700 s the discrepancy is about 15 %. KEYWORDS: Average beta and gamma energies, decay heat, ^{235}U, ^{238}U, ^{239}Pu |