Tests for the dynamic behaviour of isolation valve cone screws Original Research Article

Hot tensile tests at 270°C were carried out on two unused and two used original isolation valve cone screws M30-T × 92.5 mm (material 21 CrMo V 5 7) from the KKP nuclear power plant. The latter had been stressed in an incident at the Philippsburg 1 reactor power station on 27 December 1992. To assess the ability of these components to withstand the dynamic stress caused by ‘rapid opening’ of the isolation valves, supplementary impact tests were made at 270°C on six original KKP isolation valve cone screws. The impact velocity was 13.5 m s−1 for four screws and 6 m s−1 for two screws. The test conditions regarding impact damping and mass distribution were adapted to the isolation valve situation by means of parameter studies. Hardness values and deformation values, e.g. stress at the start of flow, tensile strength, total elongation, elongation and reduction in area at fracture and energy absorption up to maximum force and up to break, were determined in the hot tensile tests.