Study Evaluates Neutron Shielding Materials for Reactor Antineutrino Detector
Researchers developing the ALARM reactor antineutrino detector at China's Taishan Nuclear Power Plant tested three neutron shielding materials and found that 30 cm of boron-doped high-density polyethylene (BHDPE) blocks more than 95% of both fast and thermal neutrons. The ALARM experiment is designed to monitor reactor power using plastic scintillators deployed roughly 44 meters from the reactor core at a shallow depth of 9.6 meters, where cosmic ray-induced neutrons pose a significant background challenge. The findings provide a practical shielding solution for surface-level neutrino detectors, where overburden is insufficient to naturally suppress cosmic ray backgrounds.
The ALARM (Array of Lattice for Anti-neutrino Reactor Monitoring) experiment, a plastic scintillator-based detector intended for reactor power monitoring at the Taishan Nuclear Power Plant in China, faces a substantial background from cosmic ray-induced fast neutrons due to its shallow underground placement at just 9.6 meters depth. To address this, researchers experimentally evaluated the neutron shielding performance of three candidate materials: water, standard high-density polyethylene (HDPE), and HDPE doped with 40% boron (BHDPE). Using an EJ426 scintillator-based thermal neutron detector and an Am-Be neutron source, they measured shielding efficiency at multiple material thicknesses. A 30-centimeter layer of BHDPE was found to exceed 95% shielding efficiency against both fast and thermal neutrons, outperforming the other two materials. Monte Carlo simulations of the experimental setup reproduced the measured results, and additional simulations of the full ALARM shielding assembly were also conducted and reported. These results inform the final shielding design for ALARM and are broadly relevant to other surface-level or shallow-depth antineutrino experiments facing similar cosmic ray backgrounds.
What's missing
Cost, structural, and safety considerations of deploying 40% boron-loaded HDPE in a nuclear plant environment are not addressed. The study is a preprint and has not yet undergone peer review.
What different sources said
- arXiv physicsCenter
Study on the shielding efficiency of water, HDPE, and boron-loaded HDPE for neutron background of plastic scintillator neutrino detector
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