Simulation Study on Neutron Dose Monitoring Based on Joint Measurement of Neutron and Prompt Gamma-Rays

Abstract

The monitoring of neutron ambient dose equivalent rate in a radiation field is of significant importance as it can reflect the operational status of nuclear facilities and provide radiation protection information. Currently, the commonly used monitoring instrument is the A-B type dose equivalent rate meter based on a single detector and a single moderator. However, its response curve differs from the “neutron fluence-ambient dose equivalent conversion coefficient,” leading to measurement errors. In this study, in order to improve the accuracy of neutron dosimeter measurement, a feasibility study was carried out on the joint monitoring of neutron dose rate based on neutrons and instant γ-rays. Lead, borated polyethylene, polymethyl methacrylate, and sodium chloride were used to establish a conversion object. Monte Carlo simulations were performed to calculate the neutron responses of elements B, H, Cl, Pb, C and O. Then, these response curves were combined with the response curves of the LB6411 dosimeter to obtain a new response curve closer to the “neutron fluence-ambient dose equivalent conversion coefficient”. The linear fitting coefficients were calculated by using the differential evolution algorithm. The results demonstrate that the modified response curve is closely to the \begin{document}$h_{\phi} $\end{document} response curve. The relative discrepancies are within 50% for the energy range of 1×10−8-16 MeV. The study indicates the feasibility of joint measurement of neutron and prompt gamma-ray for monitoring neutron ambient dose equivalent rate, providing new directions and support for neutron dosimeter calibration and development.

Keywords

• neutron ambient dose equivalent
• prompt gamma rays
• response curve
• differential evolution algorithm