Session: 04-12: SMRs, Advanced Reactors and Fusion

Paper Number: 135407

135407 - Methodology Development for Explosion Hazard Evaluation in Hydrogen Production System Using High Temperature Gas-Cooled Reactor 

Abstract: 

 High temperature gas-cooled reactor (HTGR) is expected to use nuclear heat to wide range of industrial applications such as hydrogen production, seawater desalination, and district heating, which is capable of high temperature heat supply with inherent safe characteristics. Japan Atomic Energy Agency (JAEA) started a High Temperature engineering Test Reactor (HTTR) heat application test project to develop coupling technologies between HTGR and a hydrogen production plant necessary to achieve large-scale, carbon-free hydrogen production. One of the key technologies is a safety evaluation method which can simulate an impact of explosion hazards induced in the hydrogen production plant on reactor facility because HTGR hydrogen production system contains large amount of combustible gases such as hydrogen.

  A computational fluid dynamics code FLACS has been sufficiently validated for dispersion and explosion of combustible gases such as hydrogen and methane worldwide, however, only few attempts have been made for validation of analysis in closed area with small space. A leak of combustible gases to the piping in HTGR hydrogen production system may occur in case of abnormal condition in hydrogen production plant and therefore an explosion in the piping must be considered.

  Two experiments on combustible gas explosion in piping are selected to compare with calculated results obtained by FLACS code. One is the deflagration of natural gas in a simple closed container consisting of two spherical vessels of different sizes and a thin straight piping (Experiment 1), and the other is the deflagration of mixture of hydrogen and methane gas in an opened complex piping including multiple branches (Experiment 2).

  The comparison of calculated and experimental results showed good agreement for maximum pressure and temperature in Experiment 1. In Experiment 2, the maximum pressure and flame spread velocity in a section of straight piping from the ignition point to the first branch also agreed well in calculated and experimental results. On the other hand, the calculated pressure at far points after the first branch were conservatively overestimated compared to the experimental one. This is considered that FLACS code only numerically solves the flame spread process due to combustion phenomena by combustible gases according to the governing equations and does not take into account for heat dissipation, local energy loss and reflections at piping elbows and walls.

  This study concluded that the FLACS code was applicable for conservative evaluation of the maximum pressure for a deflagration of combustible gases in piping in HTGR hydrogen production system.

Presenting Author: Keisuke Morita Japan Atomic Energy Agency

Presenting Author Biography: Keisuke Morita is an engineering researcher in Japan Atomic Energy Agency, Japan. He is currently working on the safety design for high temperature gas cooled reactors (HTGRs). He got Master Degree of Nuclear Engineering from Kyushu University in 2018 for reactor physics for a HTGR.

Authors:

Keisuke Morita Japan Atomic Energy Agency
Takeshi Aoki Japan Atomic Energy Agency
Atsushi Shimizu Japan Atomic Energy Agency
Hiroyuki Sato Japan Atomic Energy Agency