Structural design code for very high temperature cooled nuclear reactor cooling components

A structural design code was developed for application to the very high temperature service ranging to 1,000C. The Japanese High Temperature Engineering Test Reactor (HTTR) is under construction and is aimed primarily at demonstrating the application of high temperature gas cooled reactor technology. In the HTTR design, a helium-to-helium intermediate heat exchanger is operated at a very high temperature (in excess of 900 C) and serves as the reactor coolant pressure boundary. As a structural material of the very high temperature component, Hastelloy XR, solid-solution strengthened Ni-based Cr-Mo-Fe alloy has been developed with improved compatibility with primary and secondary helium coolants. The operating temperature is in the very significant creep range of the mechanical properties for the superalloy. Several measures to cope with the very significant creep issue were proposed so as to extend existing elevated temperature structural design methodologies to the very high temperature service