Hydrogen production based on nuclear energy plays a crucial role in achieving national major strategic goals of carbon peaking and carbon neutrality. The high-temperature gas-cooled reactor (HGTR) combined with thermochemical water splitting is considered a promising method for large-scale green hydrogen production. Safety concerns, especially hydrogen leakage and diffusion, are central to the development of nuclear hydrogen production systems.

This study aims to investigate how the parameters of hydrogen storage and environmental conditions affect hydrogen leakage, diffusion, and the minimum safe separation distance between hydrogen production plants and nuclear power plants.

A numerical simulation approach was adopted to assess the leakage and diffusion behavior of hydrogen under various conditions, focusing on three main variables, i.e. internal tank pressure, tank volume, and ambient temperature. Hydrogen release and subsequent diffusion were simulated using a defined range of these parameters to evaluate their effects on gas dispersion. The Netherlands Organization (TNO) multi-energy method was applied to estimating the peak overpressure resulting from potential hydrogen explosions. Based on the overpressure thresholds, the minimum separation distance required to prevent safety accidents was predicted. All simulations were conducted under conservative assumptions to ensure robustness of the results.

The results show a clear linear relationship between internal tank pressure and hydrogen diffusion distance. When the pressure is increased from 1.0 MPa to 3.0 MPa, the diffusion radius is extended from approximately 120 m to over 230 m. The ambient temperature has negligible effects on both the diffusion distance and concentration distribution. However, a larger tank volume significantly prolongs the leakage and diffusion duration. Under the worst-case conditions simulated, the conservative minimum safe separation distance is determined to be 253 m.

The results of this study indicate that internal pressure and tank volume are critical factors influencing hydrogen dispersion risk whilst environmental temperature has limited impact. The findings provide valuable reference data for the safety evaluation and spatial planning of nuclear hydrogen production systems, supporting the development of safe and efficient green hydrogen infrastructure.