Neutronics Benchmark of CEFR Start-Up Tests: reaction rates and integral reactivity coefficients

A coordinated research project (CRP) entitled “Neutronics Benchmark of CEFR Start-up Tests” has been conducted for improvement of analytical capabilities of fast reactor modelling and simulations. Among the six experiments and two numerical benchmarks, two benchmarks of reaction rate measurements from foil activations and the integral reactivity coefficient are documented in this paper. Sixteen and ten international organizations participated in the reaction rate benchmark and evaluation of integral reactivity coefficients, respectively, using various deterministic and stochastic computation codes and evaluated nuclear data libraries of ENDF/B, JEFF, and JENDL. For the reaction rate measurement by foil activations, stochastic and deterministic codes used in this study gives results in good agreement with the experiment, axially and radially. However, a relatively large variation is observed in the estimated 197 Au (n, γ) reaction rate values, in particular, at points far from the fueled-region. Except for several outliers, the evaluated integral reactivity coefficients show generally good agreement between participants regardless of deterministic and stochastic calculation methods.