LAUSR

Abstract The paper presents a benchmark aimed at assessing the accuracy of Monte Carlo codes to simulate the neutron detector response in near-core geometry of a subcritical water-moderated reactor. The experiment included six levels of subcriticality with keff from 0.93 to 0.996, and four fixed detector positions. Studied parameters included: first, the prediction of the change in detector response with the change in subcritical multiplication at a given detector position; second, the prediction of the change in neutron flux spatial distribution; third, the effectiveness of calculated correction factors to decrease the inconsistency in reactivity determined using detectors at various locations. Calculations were performed in MCNP6 code using two nuclear data sets. Both the general source and the eigenvalue (criticality) mode of calculation were studied. Finally, the effect of the offset between the calculated and experimentally determined critical condition on the prediction of detector response in the subcritical state was analysed.