With the development of materials science and technology, more and more novel neutron shielding materials have been studied and prepared. The test of thermal neutron shielding performance of materials is an important measure of evaluating the shielding performance of novel neutron shielding materials, and provides important guidance for the improvement and application of materials. Special attention has been paid to the thermal neutron shielding properties of some thin materials, such as radiation protection fibers, shielding coatings, radiation protection rubber, composites with thermal neutron absorbers. At present, it is not easy to obtain pure thermal neutron field based on isotope neutron source, and the commonly used thermal neutron detector has a wide energy response range, and there is no unified test standard, hence the accuracy of the test results of thermal neutron shielding performance of materials needs to be further improved.

This study aims to propose an accurate method for testing the thermal neutron shielding properties of materials and to design a corresponding test platform.

A thermal neutron shielding performance testing method based on the "cadmium filter method" was proposed and a corresponding testing platform was established. Firstly, the platform was based on a ²⁵²Cf isotope neutron source and a ³He proportional counter, with the design principle of minimizing errors. Then, Monte Carlo simulation method was used to optimize the materials and dimensions of the radiation shield, neutron moderator, collimator, and detector shield of the platform. The system error caused by the testing principle was reduced by further optimizing the cadmium filter method, and a collimating neutron beam launcher was designed to improve the collimation effect of the neutron beam, increase the thermal neutron fluence rate and thermal neutron share, and reduce the random error and the system error caused by the system design. Finally, the thermal neutron shielding performance of the materials commonly used in the nuclear field were tested and corresponding simulation calculations were carried out to verify the feasibility and accuracy of the test method. Five factors affecting shielding performance testing, i.e., detector type, neutron source intensity, distance to detector, detection system centerline offset, and neutron source type were analyzed simultaneously.

The actual test results are in good agreement with the simulation results, with excellent repeatability and reproducibility under different influencing factors.

This study provides an effective means to accurately evaluate the thermal neutron shielding properties of materials.