Rationale

Idaho National Laboratory is requesting the addition of Grade 316H to ASTM A988/A988M. Idaho National Laboratory requires this coverage to support work on experimental micro-reactors conforming to ASME BPVC Section III Division 5 requirements for advanced high-temperature reactors. The policy of the ASME Boiler and Pressure Vessel (BPV) Committee on Materials is to approve, for inclusion in the Code Sections, only materials covered by specifications that standards-developing organizations, such as ASTM, have issued. Idaho National Laboratory is the user and is working with several materials producers. Although the UNS Number will be the same as the wrought 316H, the 316H Grade is being added following the protocol for a new grade because the grain size requirement will differ from that of the forged product. Forged 316H requires a grain size of 6 or coarser; the PM-HIP product will have a grain size of 9 or coarser. Support letters and test data from three heats are included with this proposal.