ASME Code Case Development Strategy for Ferritic/Martensitic HT-9 Steel
The US Department of Energy (DOE), Office of Nuclear Energy (NE), is supporting the development of an ASME Code Case for adoption of 12Cr-1Mo-VW ferritic/martensitic (F/M) steel, commonly known as HT-9, primarily for use in design of liquid-metal fast reactors (LMFR) and components. In 2011, Los Alamos National Laboratory (LANL) nuclear engineering staff began assisting in the development of a small modular reactor (SMR) design concept, previously known as the Hyperion Module, now called the Gen4 Module, being developed by Gen4 Energy, Inc. located in Denver, Colorado. LANL engineering staff had initially proposed either T91 (9Cr-1Mo-VNb) or HT-9 for the reactor vessel and components, as well as fuel clad and ducting. Although T91 is currently an approved/authorized material for elevated temperature design in the ASME Code, the preference is utilization of HT-9 due to its extensive irradiation database and similar creep resistance as T91. In addition, HT-9 has relatively good corrosion properties for fast reactor environment, such as liquid lead bismuth eutectic coolant. Although the ASME material Code Case, for adoption of HT-9 as an approved elevated temperature material for LMFR service, is the ultimate goal of this project, several key deliverables have been accomplished in FY2012 to provide assurance to DOE/NE of the viability and feasibility of pursuing this goal. An important key deliverable was the recently completed, Gap Analysis of Material Properties Data for Ferritic/Martensitic HT-9 (1). This report provided a cursory research, accumulation, and documentation of specific material parameters; physical, mechanical, and environmental, which are necessary for ensuring a successful ASME Code Case. Time-independent tensile and ductility data and time-dependent creep and creep-rupture behavior are some of the material properties required for a successful ASME Code case. Unfortunately, results of the Gap Analysis report show that many of the material properties have limited data availability in open-source documentation, or are contained in Applied Technology documents, or there is insufficient data to support the ASME requirement from 3-separate heats of material.