Quantitative safety assessment of pressure control failure in a deep underground large scale cryogenic installation

•Risk assessment of a deep underground large scale cryogen storage facilityDevelopment of accident sequences and evaluation of cryogen leak frequencies.•Identification of process design vulnerabilities for targeted improvements.•3D CFD transient dispersion simulations of 2-phase leak of fluid heavier than air.•Personnel safety in a next generation neutrino physics observatory.

This work considers the safety analysis and quantitative risk assessment of a cryogenic installation located in specially excavated caverns 1400 m underground. The installation includes a custom-designed heat insulated Tank hosting over 65 kt of cryogenic argon. The conditions inside the Tank and its cavern will be maintained using appropriate process systems for cooling, heating, pressurization and filtration. Smaller adjacent caverns will host the auxiliary process equipment. This paper identifies the possible hazards, quantifies accident occurrence frequencies, and performs detailed simulations of accidental argon release due to pressure control failures. The quantitative results indicate weak spots for improvements on the current process design of the installation.