TESTS FOR THE DYNAMIC BEHAVIOR OF ISOLATION VALVE CONE SCREWS

Hot tensile tests at 270 degrees C were carried out on two unused and two used original isolation valve cone screws M30-T x 92.5 mm (materia l 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 o n 27 December 1992. To assess the ability of these components to withs tand the dynamic stress caused by 'rapid opening' of the isolation val ves, supplementary impact tests were made at 270 degrees C on six orig inal 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 is olation valve situation by means of parameter studies. Hardness values and deformation values, e.g. stress at the start of flow, tensile str ength, total elongation, elongation and reduction in area at fracture and energy absorption up to maximum force and up to break, were determ ined in the hot tensile tests.