OBSERVATIONS ON THE RECOVERY OF NEUTRON-EMBRITTLED REACTOR PRESSURE VESSEL STEELS.

One of the limiting constraints on normal PWR operation concerns the prevention of catastrophic crack propagation by maintaining adequate fracture toughness in the reactor pressure vessel (RPV) steel. Annealing studies on some neutron-embrittled reactor pressure vessel (RPV) steels have suggested that a hitherto unrecognized mechanism may be responsible for their embrittlement. In order to test this damage model a positron annihilation technique was applied. The results of these experiments suggest a novel approach to the in-service inspection of these vessels.