Zero-power criticality benchmark evaluation of the Molten Salt Reactor Experiment

An effort is being carried to create a reactor physics benchmark based on the Molten Salt Reactor Experiment (MSRE). In this framework, detailed benchmark specifications were compiled and a corresponding model was created using the Monte Carlo code Serpent. The model was used to analyze the first zero-power critical experiment at MSRE when ²³⁵U was progressively added to the fuel salt in order to achieve criticality with stationary salt and isothermal conditions. The calculated multiplication factor in such conditions was 1.01276 (±10 pcm). The total uncertainty for experimental k_eff was estimated to be 478 pcm. The total uncertainty of k_eff from cross section data uncertainty using Scale-6.2 56-group covariance matrices was estimated to be 667 pcm. The benchmark model was also applied to determine the reactivity loss due to fuel circulation. The obtained reactivity drop (-224±7 pcm) matches well with the value calculated by the scientists at the MSRE (-212 pcm). Calculations of the differential and integral control rod worth also show good agreement with the experiment values. The benchmark specifications are expected to appear in the International Reactor Physics Experiment Evaluation Project handbook in next two years. (Author)