The Slow-Neutron Fission Cross Sections of the Common Fissile Nuclides (Revised 1975)

The fission cross sections for ²³³U, ²³⁵U, ²³⁹Pu, and ²⁴¹Pu reported in 1958 have been revised using the very precise, recently published, specific activities 21 405 ± 20 dpm/µg ²³³U, 4798.1 ± 3.3 dpm/mg ²³⁵U, and 746.19 ± 0.41 dpm/mg ²³⁸U. Revised ratios of fission cross sections at 2200 m/sec are: ²³³U/²³⁵U = 0.9142 ± 0.0012, ²³⁹Pu/²³⁵U = 1.2876 ± 0.0034, ²³⁹Pu/ ²³³U = 1.4084 ± 0.0036, and ²⁴¹Pu/²³⁹Pu = 1.3506 ± 0.007. Revised fission cross sections at 200 m/sec in barns relative to σ^c(¹⁹⁷ Au) = 98.7 ± 0.2 are: σ^f(²³³ U) = 527.4 ± 3.1 σ^f(²³⁵ U) = 576.9 ± 3.4, σ^f(²³⁹ Pu) = 742.8 ± 4.4, and σ^f(²⁴¹ Pu) = 1003.3 ± 5.2. The errors do not include g-factor errors of ±0.2% for ²³³U, ±0.155% for ²³⁵U, ±0.285% for ²³⁹Pu, and ±0.7% for ²⁴¹Pu.