Thermal-fluid-structure analysis of fast pressure relief valve under severe nuclear accident

• Published in: Nuclear engineering and design 2021-01, Vol.371, p.110937, Article 110937
• Main Authors: Zhang, Hu, Zhao, Lei, Peng, Shao-En, Ru, Qiang, Liu, Ping, Wu, Jun-Mei
• Format: Article
• Language: English
• Subjects: Comparative analysis; Computational fluid dynamics; Coupling; Fast pressure relief valve; Fluid flow; Heat transfer; High pressure; High temperature; Load; Mass flow; Mathematical models; Mechanical properties; Nuclear accidents; Nuclear accidents & safety; Nuclear energy; Nuclear engineering; Nuclear power plants; Nuclear safety; Pressure; Primary circuits; Reliability analysis; Relief valves; Severe accident condition; Simulation; Static structural analysis; Steam electric power generation; Stress analysis; Structural analysis; Temperature effects; Thermal analysis; Thermal shock; Thermal stress; Thermal-fluid-structure coupling; Transient thermal shock
• ISSN: 0029-5493; 1872-759X
• DOI: 10.1016/j.nucengdes.2020.110937

•Transient thermal-fluid-structure analysis of fast pressure relief valve (FPRV).•Transient thermal analysis and structural static analysis are conducted.•Thermal stress is much larger than mechanical stress within FPRV in severe accident.•Safety evaluation method of structural stability under severe nuclear accident is discussed. Fast pressure relief valve (FPRV) equipped at the pressurizer of nuclear power system is used to release steam with high pressure and high temperature rapidly from the primary circuit loop and to prevent high temperature core melting in case of severe accident condition. When releasing the steam, the time-varying temperature, mass flow and interior pressure of the inlet will affect the reliability of FPRV. In this study, the thermal analysis and the static structural analysis of FPRV under severe transient thermal shock are conducted by a 3D thermal-fluid-structure coupling numerical simulation considering the transient coupled flow, heat transfer and mechanical load. In the analysis, one-way coupling simulation is conducted. Firstly, the fluid flow and heat transfer in the valve and valve body are simulated with time. Then the instantaneous temperature fields of FPRV structure obtained from the CFD analysis at different critical moments, at which the valve is bearing high temperature, high mass flow or high interior pressure, are imported into static structural analysis as thermal load for stress analysis. Through comparative analysis of stress under mechanical load, thermal load and their combined effect, it is found that the thermal stress is the primary component of the coupled stress of FPRV and the thermal loads rather than the pressure loads are responsible for accidents related to stress overload in nuclear power plants. Therefore, the coupled stress including thermal stress should be less than the allowable stress intensity for the safety evaluation of the FPRV in a nuclear power plant.