Session: 04-01: SMRs, Advanced Reactors and Fusion

Paper Number: 130396

130396 - Research on Pressure Suppression and Against Hydrogen Risk of the Smr in Floating Nuclear Power Plants 

Abstract: 

In the event of loss of coolant accident (LOCA) in small modular reactors (SMRs) in floating nuclear power plants (FNPP), the initial stage of the accident sees a significant influx of water vapor into the containment. The swift escalation of temperature and pressure within the containment vessel may lead to the failure of containment due to overpressure. As the accident unfolds, inadequate cooling of the core may result in a robust exothermic oxidation reaction between the zirconium alloy cladding and water or water vapor. This reaction generates a substantial quantity of hydrogen, a significant portion of which enters the containment. The rapid combustion or explosion of this accumulated hydrogen further poses the risk of compromising containment integrity. Appropriate pressure suppression and hydrogen elimination measures must be taken to ensure small modular reactors' safety. This paper utilizes GASFLOW to model and analyze the environmental conditions and gas behavior within the containment following the implementation of pressure suppression and hydrogen elimination measures in small modular reactors. Concerning pressure suppression, the impact of the cross-sectional area of the suppression pipeline in the suppression pool on suppression effectiveness are analyzed. To eliminate the hydrogen risk, the flow distribution of hydrogen within the containment is first analyzed, followed by a simulation calculation of hydrogen elimination using passive autocatalytic recombiners (PARs) alone, igniter alone, and PARs and igniter combined to analyze the ability of hydrogen risk mitigation. The results indicate that: 1) In cases where the cross-sectional area of the suppression pipeline is either excessively large or small, adverse effects on suppression effectiveness are observed. The study shows that there is an optimal cross-sectional area of suppression pipeline to achieve the best suppression effect of suppression pool. 2) When passive autocatalytic recombiners (PARs) are employed as the sole method for hydrogen elimination, due to the slow speed of dehydrogenation of PARs, hydrogen can’t be eliminated quickly, and combustible cloud volume and hydrogen concentration can’t be effectively reduced, Consequently, a residual risk of a hydrogen explosion persists within the containment. 3) When the igniter is employed as a standalone measure, there is a notable reduction in both combustible cloud volume and hydrogen concentration. This effectively mitigates the risk of hydrogen within the containment. Furthermore, the peak pressure in the containment is lower than the design pressure during the hydrogen elimination process. 4) The combination of PARs and igniters proves highly effective in reducing combustible cloud volume and hydrogen concentration, ultimately eliminating hydrogen risks.

Presenting Author: Xuefeng Lyu School of Nuclear Science and Engineering, North China Electric Power University

Presenting Author Biography: Professor and doctoral supervisor at the School of Nuclear Science and Engineering, North China Electric Power University.

Authors:

Jialei Chen School of Nuclear Science and Engineering, North China Electric Power University
Xuefeng Lyu School of Nuclear Science and Engineering, North China Electric Power University
Jiayu Zhang School of Nuclear Science and Engineering, North China Electric Power University
Shengfei Wang School of Nuclear Science and Engineering, North China Electric Power University
Houjian Zhao School of Nuclear Science and Engineering, North China Electric Power University
Fang Liu School of Nuclear Science and Engineering, North China Electric Power University
Yu Yu School of Nuclear Science and Engineering, North China Electric Power University