Nuclear reactor structures

Purpose: To improve the stress corrosion cracking resistance of nuclear reactor structures in high temperature and high pressure water. Constitution: Control rod driving mechanisms, housing stab tubes, shroud supports, nozzle safe ends and stretch tubes of reactor core pumps, etc. of nuclear reactor structures having clevises in high temperature and high pressure water are constituted with Ni-based alloy of high stress corrosion cracking resistance. When formulating the ingredients of the Ni-based alloy so as to comprise less than 0.04 % C, 14 - 17 % Cr, 6 - 10 % Fe, less than 0.5 % Cu, less than 0.01 % of at least one of Mg and Ca, less than 0.05 % of at least one of Zr and Y and the balance of Ni by weight, the alloy shows no sensitivity to stress corrosion crackings even when heated at 400 - 450 deg C for a long period of time. Accordingly, the stress corrosion cracking resistance of nuclear reactor structures in high temperature and high pressure water can be improved. (Seki, T.)