RELAP5 application for water hammer analysis in different thermal-hydraulic systems

Abstract

• Causes of water hammers: rapid valve operation, void-induced, condensation-induced. • RELAP5 code may represent water hammer due to valve operation and appearance of void. • The developed modelling recommendations are based on comparative analysis. • Water hammer in nuclear, fusion and district heating systems possible due to fast valve actions. • Integrity of pipelines in nuclear, fusion and district heating systems remain not violated. The water hammer phenomenon investigations employing RELAP5 code with one-dimensional two-fluid six-equation models of water and steam flow were performed and the main results shared in this paper. The capability of RELAP5 code to simulate transients leading strong pressure pulses was investigated employing the measurement results of three test facilities for different water hammer types: PPP at UMSICHT, CWHTF at FZR Dresden and PMK-2 at AEKI. Based on the benchmarking results the recommendations for the modelling of piping systems, which could be affected by different types of water hammer were developed and tested. The recommendations cover selection of thermal-hydraulic system conditions, parameters of modelling and RELAP5 code correlations. These recommendations have enabled to develop a detail RELAP5 models for the simulation of water hammer effects in further research works. The applications of RELAP5 code for water hammer analysis in different thermal-hydraulic systems (RBMK-1500 reactor main circulation loop, targets cooling/heating circuit in Wendelstein 7-X experimental stellarator facility and pipelines in district heating system) are presented in this paper. The performed analyses of transients demonstrated that the pressure pulsations could appear in all these systems as results of check valve closures. However, pressure surges are not so strong due to specific of such systems and integrity of pipelines remains not violated.