Effect of neutron flux on low temperature irradiation embrittlement of reactor pressure vessel steel

Miniature Charpy V-notch impact test specimens of commercial reactor pressu re vessel (RPV) steels having high and low copper contents were irradiated at the different irradiation positions with neutron flux levels of similar to 6 x 10(14) similar to 7 x 10(15), and similar to 8 x 10(16) n m(-2) s(-1 ) (E > 1 MeV) to fluence levels ranging from similar to 6 x 10(21) to simil ar to 7 x 10(22) n m(-2) (E > 1 MeV) at temperatures of about 50 degrees C to 150 degrees C in the Japan Materials Testing Reactor (JMTR). The results showed that the radiation-induced increases in ductile-to-brittle transiti on temperature (Delta DBTT) at a neutron flux level of similar to 6 x 10(14 ) were greater than those for neutron flux level of similar to 7 x 10(15) n m(-2) s(-1). The neutron flux effect on embrittlement tended to be more pr onounced in the lower neutron fluence range of similar to 6 x 10(21)-simila r to 1 x 10(22) n m(-2) than in the higher fluence level of similar to 7 x 10(22) n m(-2), and also to be larger for the low copper steel than for the high copper steel, although the Delta DBTT for the high copper steel was l arger than that for the low copper steel regardless of neutron fluence or f lux, The displacement dose rate effect identified by the data converted to the Delta DBTT for the full size Charpy specimens from those for the miniat ure Charpy specimens was consistent with that based on the comparison of th e results in the literature. (C) 1999 Elsevier Science B.V. All rights rese rved.