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

•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.