Evaluation of advanced reactor pressure vessel steels under neutron irradiation

The objective of the work described in this paper is to assess the radiation behavior of improved steels and weldments, produced in various countries. Three of the materials supplied by France and Japan to the IAEA program have been irradiated at 290 and/or 2500C in the HERALD light water research reactor to assess the mechanical and upper shelf toughness properties after exposure to neutron fluences of approx. 1 x 1019 n.cm2 (E > 1 MeV). A fourth material, a weld supplied by the UK, has been included in the program for reference. Supplementary test methods used in the evaluation include hardness tests, chemical analyses, electron microscopy and positron annihilation. Results indicate that the improved steels are more resistant to radiation induced embrittlement compared to both the UK reference material and published data on older steels. The mechanistic understanding of irradiation embrittlement is becoming increasingly important particularly in terms of deriving a damage correlation model. The data from the supplementary tests are making a significant contribution towards this objective