Waterproof and radon suppression engineering technology and application at China Jinping underground laboratory

Abstract

[Objective] Radon, an inert gas continuously exuded and decayed from the surrounding rock of underground chambers, is seriously interfered with cutting-edge physical experiments, such as dark matter research in deep underground laboratories, and poses health hazards to experimental personnel. To reduce radon levels in the experimental space and maintain the dryness of the chamber environment, [Methods] a special lightweight waterproof radon-suppressing structure was innovatively constructed in Phase II of the China Jinping Underground Laboratory. This structure was designed to isolate radon and groundwater exuded from the surrounding rock outside the experimental space while minimizing additional radiation background introduced by external materials. Measurements of air radon concentration under different protective structures and ventilation conditions were conducted in situ.[Results] It was shown that, under good ventilation conditions, an ultralow radon concentration of 11.1 Bq/m³ was achieved with the self-developed waterproof radon-suppressing structure, creating a clean air environment. Without a fresh air system, radon concentrations were reduced to 18.75% of the level in a chamber with conditions similar to the original chamber. One year after the construction of the waterproof radon-suppressing structure, radon concentrations in the laboratory remained stable, and no leakage was observed throughout the lifecycle of the chamber.[Conclusion] The self-developed waterproof radon-suppressing structure was demonstrated to significantly reduce radon concentration in indoor environments, maintain stable radon levels without leakage, and provide a novel method and technology for constructing waterproof and radon-suppressing environments in underground laboratories worldwide.

Keywords

waterproof and radon suppression / low radiation background / China Jinping underground laboratory / Indoor radon measurement / influencing factors / groundwater / underground cavity