Next Generation Nuclear Plant Steam Generator and Intermediate Heat Exchanger Materials Research and Development Plan

Abstract

SUMMARYThe U.S. Department of Energy (DOE) has selected the high temperature gas-cooled reactor (HTGR) design for the Next Generation Nuclear Plant (NGNP) Project. The NGNP will demonstrate the use of nuclear power for process heat, hydrogen and electricity production. The reactor will be graphite moderated with helium as the primary coolant. Final design features have not been determined and the reactor may be either prismatic or pebble-bed. It will use low-enriched uranium tri-isotopic (TRISO)-coated fuel. It is likely to have an outlet gas temperature of 750°C with a steam generator (SG) and a design service life of 60 years. The plant size, reactor thermal power, and core configuration will ensure passive decay heat removal without fuel damage or radioactive material releases during accidents. Follow-on HTGRs may have outlet temperatures up to 950°C and will incorporate a gas-to-gas intermediate heat exchanger (IHX).The revisions incorporated into this research and development (R&D) plan reflect technical issues associated with the SG that were not considered for application in the NGNP when the plan was initially developed. This R&D plan describes work that is necessary for the first-of-a-kind NGNP and follow-on reactors that might have different design parameters. The fundamental challenge for NGNP is to achieve a significant advancement in nuclear technology while setting the stage for an economically viable deployment of the new technology in the commercial sector soon after 2020.Alloy 800H is approved in the American Society of Mechanical Engineers (ASME) Codes for nuclear applications up to 760°C with a maximum design life of 300,000 h. An SG for 750°C service may require longer service life than the currently allowed 300,000 h. Testing and constitutive model development to support extension of the allowable temperature for this alloy and the allowable lifetime to 500,000 h (~60 years with 95% of availability) are included in this plan. Due to the high design temperature, the requirements of materials for the IHX are among the most demanding. In addition to the SG, this R&D plan focuses on tasks that will be required to generate sufficient understanding of materials for successful design and operation of the NGNP IHX for which the prime candidate material is Alloy 617. Requirements for other core internals (e.g., the core barrel or control rod sleeves) are described in less detail in Appendix C.A number of solid solution strengthened nickel-and iron-based alloys have been considered for application in the NGNP. The primary candidates were Alloy 617, Alloy 230, Alloy 800H and Alloy X. Based on the technical maturity, availability in required product forms, experience base, and high temperature mechanical properties, all of the pre-conceptual design studies prepared by potential reactor vendors have specified Alloy 617 as the material of choice for heat exchangers. Also a draft ASME Code case for Alloy 617 was developed previously. Although action was suspended before the Draft Alloy 617 Code Case was ac...

Study on Creep-Fatigue Mechanical Behavior and Life Prediction of Ti2AlNb-Based Alloy

“…Creep-fatigue failure may occur in the high-temperature structures of aeroengines during operation, which is the result of power changes during equipment operation. Power transience will lead to cyclic loads, and stress relaxation will occur during stable operation [1]. Creep failure is usually caused by creep voids near grain boundaries, and fatigue failure is usually caused by crack damage.…”