Abstract: The waste heat discharge heat exchanger is the key equipment of the nuclear reactor core cooling system. After the unit is shut down, the residual heat exhaust heat exchanger should be visually inspected according to the requirements of the in-service inspection program. If leakage is found on the primary side and the secondary side, It needs to be overhauled. In order to ensure the safe operation of nuclear power plants, the necessity and methods of penetrant testing of tube sheet welds during the overall overhaul of the waste heat exhaust heat exchanger are discussed.