900MWe PWR: Behaviour of cables in severe accident conditions

Some items of equipment inside the containment can be used to minimise the consequences of a severe accident in terms of radioactive releases. Therefore, this equipment should be tested and estimations should be made regarding its behaviour when subjected to extreme conditions, particularly in terms of irradiation. This paper describes the tests carried out on the behaviour of instrumentation and control cables of the pressure relief valves installed on the pressuriser and which must be opened in order to prevent a meltdown under pressure. A specific study was conducted on the Hypalon(R) outer cladding of these cables. After dealing with the various problems which could call into question the relevance of the experiments in relation to real accident conditions, the test conditions are described and the results obtained are given. Based on monitoring of mechanical and electrical properties, it has been shown that the instrumentation and control cables of the pressure relief valves of the reactor coolant system remain intact for first 40 hours of the accident sequences used in these tests.