Reactor core upper mechanisms

Purpose: To improve the safety of LMFBR type reactors by specifying the materials used for flow stabilizer of the upper mechanisms for reactor core. Constitution: The support pipes, the support plates for the stabilizer and the sodium stabilizer of the reactor core upper mechanisms are made of such materials as alloy 718 according to AMS standard that has greater than 13 kg/mm2 of peak stress strength corresponding to repeating thermal stresses of 108 at a temperature of about 5000C. The reactor core upper mechanisms can thus surely endure for a long time against stationary thermal stresses resulted from a large temperature difference of sodium issued from the reactor core constituent elements, as well as to periodical thermal stresses resulted from large temperature fluctuations with usual plate thickness and the reactor safety can be improved. Further, the support pipes and the sodium stabilizer can be made as in usual coupling structure with the thick support plates, whereby corrosion problems can be solved and the ensurance for the material wholesomeness can be obtained with ease. (Horiuchi, T.)