Measurements and Monte-Carlo simulations of the particle self-shielding effect of B4C grains in neutron shielding concrete

TL;DR

This study combines measurements and Monte-Carlo simulations to analyze how B4C grains in neutron shielding concrete self-shield, revealing that neglecting this effect can underestimate necessary shielding for low-energy neutrons.

Contribution

It introduces a method to include particle self-shielding effects in Geant4 simulations, improving accuracy in neutron shielding calculations.

Findings

Self-shielding effect significantly impacts neutron attenuation.

Simulations with effective cross-sections match experimental results.

Neglecting self-shielding leads to underestimating shielding requirements.

Abstract

A combined measurement and Monte-Carlo simulation study was carried out in order to characterize the particle self-shielding effect of B4C grains in neutron shielding concrete. Several batches of a specialized neutron shielding concrete, with varying B4C grain sizes, were exposed to a 2 {\AA} neutron beam at the R2D2 test beamline at the Institute for Energy Technology located in Kjeller, Norway. The direct and scattered neutrons were detected with a neutron detector placed behind the concrete blocks and the results were compared to Geant4 simulations. The particle self-shielding effect was included in the Geant4 simulations by calculating effective neutron cross-sections during the Monte-Carlo simulation process. It is shown that this method well reproduces the measured results. Our results show that shielding calculations for low-energy neutrons using such materials would lead to an underestimate of the shielding required for a certain design scenario if the particle self-shielding effect is not included in the calculations.