Irradiation Embrittlement of Advanced Pressure Vessel Steels

Abstract

Seven commercial steels in the form of plate, forging, or weldments supplied by Japan, France, and the Federal Republic of Germany to the International Atomic Energy Agency (IAEA) Co-ordinated Research Programme on “Analysis of the Behaviour of Advanced Reactor Pressure Vessel Steels under Neutron Irradiation” were irradiated at 290°C to a nominal fast fluence of 1 × 1019 n/cm2 (>1 MeV) to evaluate the embrittlement sensitivity of these steels under neutron irradiation. These steels were basically of ASTM Types A533 and A508 (Unified Numbering System [UNI] K12521 and K13502) and their weldments, which had extra low copper and phosphorous contents. The copper and phosphorous contents in these individual steels varied from 0.01 to 0.07 wt% and 0.007 to 0.015 wt%, respectively. The nickel contents in these steels varied from 0.56 to 0.93 wt%. The scope of this study was mainly to evaluate the changes in the notch ductility, tensile properties, and hardness as caused by fast neutron irradiation. This paper reports the results obtained on these advanced pressure vessel steels in the form of base metal, weldments, and weld heat affected zones. The results indicated that these advanced steels were practically insensitive to fast neutron induced embrittlement. The relative embrittlement of these steels were further analyzed to examine the contribution of nickel in presence of copper in causing embrittlement. The impact test results indicated that threshold amounts of 0.04-wt% copper and 0.7-wt% nickel would perhaps be required to cause relatively enhanced embrittlement in these steels, confirming thereby that nickel in presence of copper can cause enhanced fast neutron induced embrittlement.