Gamma-Ray Spectra of the Products of Fast-Neutron Fission of ²³⁵U and ²³⁸U at Selected Times After Fission

Experimental measurements of the gamma-ray pulse-height distributions due to the products of fast-neutron-induced fission of ²³⁵U and ²³⁸U are presented. The measurements were made at nine selected times, ¼, ½, 1, 2, 5, 10, 24, 48, and 72 h after fission. Irradiation times and counting intervals were chosen to minimize saturation and decay effects. The experimental data were used to calculate 100 energy bin distributions of the absolute number of photons/(fission sec) by means of absolute calibrations of the collimated NaI(Tl) detector. The number of fissions in each sample was determined radiochemically. Machine computation was used extensively.