The effects of flux on radiation embrittlement of low-copper pressure vessel steels

The effects of neutron flux (E>1MeV) on the radiation embrittlement of the low-copper RPV steels are investigated. Tested materials include the forging matrix (JF) weld (JW) of Japan's SA 508-3 steel as well as the matrix (CF) and weld (CW) of China's domestic RPV steel. JF and CF were irradiated to fluences from 3.2 to 4.9 x 10(23)n/m(2)(E>1MeV) at 280+/-5 degrees C, JW and CW irradiated to fluences of 1.4 and 1.5 x 10(23)n/m(2) at 290+/-5 degrees C, respectively, in the test reactor. JF and JW are also used as surveillance specimens for PWR RPV, and two sets of surveillance data have been acquired. The experimental results indicate that the transition temperature shifts (Delta RTNDT) for JF irradiated in the test reactor are larger than those from surveillance specimens, when these Delta RTNDT are normalized to an effective fluence of 2 x 10(23)n/m(2) (E>1MeV) and an effective temperature of 290 degrees C. This shows notably the influence of neutron flux on Delta RTNDT. The mean Delta RTNDT for CF and CW is about 0.7 times that for JF and JW in terms of the normalized data, which imply the influences of the impurities besides Cu and microstructures on radiation embrittlement of low-copper RPV steels.