Measurement and Calculation of Integral Heavy-Element Cross-Section Ratios in the Fast Breeder Reactor EBR-II

Measurements of integral neutron capture-to-fission cross-section ratios and neutron capture rates of ²³³U, ²³⁵U, ²³⁸U, ²³⁹ Pu, ²⁴⁰ Pu, and ²⁴²Pu at 15 radial and axial positions in EBR-n are reported. Fission rates were determined by measurement of the fission product ¹³⁷Cs and capture rates were determined by mass-spectrometric and alpha-spectrometric analysis. Capture-to-fission ratios at all sample locations and central fission and capture ratios were calculated by two-dimensional RZ and XY geometries using multigroup analyses. Details of geometry and reactor composition changes during the course of the irradiations are considered and found to be significant for the fertile isotopes. A detailed comparison between measurement and calculation is presented and discussed in terms of the calculational model, cross-section data, and experimental uncertainties. Calculations were made using both Versions I and HI of ENDF/B.