Measurements of the Neutron Fission Cross Sections of ²³⁵U (E_n = 0.01 eV to 30 keV) and ²³⁹Pu (E_n = 0.01 to 60 eV)

Measurements were made of the energy dependence of the ²³⁵U neutron fission cross section over the energy range from 0.01 eV to 30 keV and of the ²³⁹Pu fission cross section over the range from 0.01 to 60 eV. The energy integral of the fission cross section for ²³⁵U was normalized to 19.26 b·eV in the 0.0206- to 0.06239-eV interval; this yielded a value of 248 ± 1.7 b·eV for the 7.8- to 11-eV interval, which is in good agreement with other measurements normalized in the same manner. The energy integral for ²³⁹Pu was normalized to 25.15 b·eV in the 0.02001- to 0.06001-eV interval; the resulting value of 504 b·eV in the 9- to 12.6-eV interval was also in good agreement with other data. For the energy ranges covered, the energy dependence of both the ²³⁵U fission cross section and the ²³⁹Pu fission cross section is consistent with ENDF/B-V data except f or a few energy intervals in which the ²³⁵U cross section differs by as much as 4%.