Microhardness as a measure of embrittlement of pressure vessel steels

The exposure of reactor pressure vessel steels to fast neutrons is known to result in reduced ductility and increased possibility of brittle failure. Initial research at the University of Virginia and previous measurements indicate that the microhardness test can be used as a supplemental nondestructive measurement of embrittlement. Increases in microhardness with irradiation correlate with shifts in the ductile to brittle transition temperature. It appears that the microhardness test can provide a direct measurement of the actual transition temperature, irradiation induced shifts in transition temperature and in uppershelf fracture energy. Thus, the microhardness test may provide a valid method for supplying the material property information required for safety analyses to prevent the premature shutdown of some operating nuclear power plants