Study of pressure tube cold pressurisation of the primary heat transport system under different design basis events

Full text: Avoidance of cold pressurisation of the pressure tubes (PTs) for PHWR is considered to be an important issue from the safety point of view. During the reactor startup/cooldown operation, a hot pressurisation practice is always followed to avoid cold pressurisation to avoid brittle failure of the pressure tube caused by hydrogen pickup. In several design basis events it has been found that system undergoes a cold pressurised conditions. Such events are identified and analysed with thermal-hydraulic safety analysis code RELAP4/MOD6 and discussed in this paper