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Bramblett and Czirr Self-Shielded Fission Rates for 235 U Physical and Analytic Benchmark

These experiments were performed by Bramblett and Czirr at UCRL (i.e., LLNL) in the late 1960s through the 1970s and evaluated by Mark Lee (LFO, retired) for the ICSBEP Handbook. Dimensions, geometry, and benchmark RSFR values are taken from the Handbook. All sample calculational results used COG 11.3 with ENDF/B-VIII.0 cross-sections. A sample input listing is provided in Appendix A.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

COG Beta-Effective Benchmarks

COG 11.3 calculations with the “new method” using ENDF/B-VIII.0 data are shown to produce results with |C/E – 1| < 3σ in all cases, whereas the other methods produce a few minor outliers. Furthermore, the “new method” using ENDF/B-VIII.0 data is observed to produce “over” and “under” results consistent with 50/50 expectations whereas the other methods appear to be slightly over or under predicting. JEFF-3.3 results are slightly larger overall than ENDF/B-VIII.0 results. In all but a few cases, it is also observed that $F_d/F_t ≥ (vF)_d/(vF)_t ≥ 1 – (k_{prompt}/k_{eff})$ and all estimators produce equivalent results for the most thermal systems. In those other cases, this relation holds within the given statistics.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗