Acceptability of ASME Code, Section III, Division 5, High Temperature Reactors

The U.S. Nuclear Regulatory Commission (NRC) is issuing Revision 2 to Regulatory Guide (RG), 1.87, "Acceptability of ASME Code, Section III, Division 5, `High Temperature Reactors.' " This RG describes an approach that is acceptable to the NRC staff to assure the mechanical/structural integrity of components that operate in elevated temperature environments and that are subject to time-dependent material properties and failure modes. It endorses, with exceptions and limitations, the American Society of Mechanical Engineers (ASME) Boiler and Pressure Vessel (BPV) Code (ASME Code) Section III, "Rules for Construction of Nuclear Facility Components," Division 5, "High Temperature Reactors," and Code Cases N-861, N-862, N-872, and N-898. The NRC is also issuing NUREG-2245, "Technical Review of the 2017 Edition of ASME Section III, Division 5, `High Temperature Reactors,' " that documents the NRC staff's review of the 2017 Edition of ASME Section III, Division 5, certain portions of the 2019 Edition, and Code Cases N-861 and N-862. The technical basis for the NRC's endorsement of Code Cases N-872 and N-898 is contained in Technical Letter Report (TLR)-RES/DE/REB-2022-01, "Review of Code Cases Permitting Use of Nickel-Based Alloy 617 in Conjunction with ASME Section III, Division 5."