Development of a compact active neutron monitor to measure the H∗(10): Design, simulation and validation

The rapid advancement of radiation technology underscores the need for effective radiation protection and monitoring. Neutron dose equivalent (NDE) meters play a crucial role in measuring the ambient dose equivalent, H∗(10), in neutron radiation environments. However, traditional NDE meters, while effective, tend to be bulky and less suitable for use in anisotropic neutron fields and confined spaces. This study presents the development of a compact, portable NDE meter designed to overcome these challenges. The device, featuring a cylindrical design with a diameter of 14.8 cm, a length of 30.5 cm, and weighing under 4 kg, is optimized for ease of use in constrained spaces. It incorporates a BF₃ thermal neutron detector encased within a high-density polyethylene moderation assembly, calibrated to replicate ICRP-74 dose conversion coefficients. The design was optimized using Monte Carlo simulations using FLUKA, emphasizing neutron response uniformity and effective moderation. Experimental validation in standard neutron reference fields confirmed the accuracy of the simulated performance, with dose rate estimates deviating by less than 8% from reference values. The NDE meter's response was consistent with that of commercially available devices, showing relative energy response variations of less than 20% for both ²⁴¹Am-Be and ²⁵²Cf sources. It demonstrated reliable energy response up to 5 MeV and consistent angular response (up to ∼ $60°$), highlighting its potential for practical radiation protection applications in diverse and constrained environments.