Rapid Net Shape Fabrication of Complex Shapes

Need: Safe, efficient nuclear power is a zero-carbon energy source. Small, modular Molten salt reactors are being commercially developed by a number of companies that can resolve much of the nuclear waste (by high burn-up and burning waste fuels), proliferation (use thorium or natural uranium), and safety (not pressurized, not susceptible to reaction with air, fail-safe failure modes) issues preventing the investment in new nuclear power sources. Small modular reactors and several other molten salt reactor designs such as those by TerraPower (MSCR), Terrestrial Energy, and Kairos (LiF-BeF2) are transitioning to demonstration scale, and could make safe, zero greenhouse gas emission electric power generation readily available. One key to commercializing these reactors is enabling cost and lead time reduction for specialty materials of construction to be operated in high temperature molten salts, particularly in wear parts such as valves, pumps, and heat exchangers. Many of these materials currently have excessive lead times (24-50 months) and limited domestic capacity, potentially delaying widespread deployment of small nuclear reactors. Approach: Specialty materials, including cermets and nickel based alloys are required to achieve 30 year life in molten salt reactor systems, including heat exchangers and molten salt pumps, as well as in power conversion systems. Powdermet has developed and demonstrated (TRL 6) advanced materials for use in molten salt pumps, valves, and heat exchangers, and has demonstrated fabrication of cermets and nickel based alloys with wrought or better properties using Spark Plasma Sintering (SPS). Current manufacturing processes consist of making billets, followed by expensive machining, resulting in increased costs and lead times for materials. This project will combine additive manufacturing of SPS molds to produce complex shapes. SPS offers fast development and production cycles and produces fully dense parts without melting (low energy input) from powder feedstock. Rapidly producing net shape components using the SPS process is enabling for rapid development and production of small modular reactor components. Phase I program: Hybrimet™ NiWC3b cermets will be fabricated into net shape components, including heat exchanger plates and valve components by combining additive manufactured molds and spark plasma sintering. Additive manufactured molds will be fabricated from an SPS-compatible pressure transmitting medium (PTM) at Ohio State University. Performance of the PTM will be modified to optimize part properties during the SPS process at 850-1100C, and material will be prepared in forms suitable for additive manufacturing. Demonstration shapes (test coupons), and then representative parts, including valve stems and seats, heat exchanger plates, and bearing cages will be fabricated from Powdermet’s Hybrimet NiWC3b cermets, as well as alloy 230 and Hastelloy N to demonstrate the process and provide initial dimensional input to ICME models to be developed in Phase II Commercial applications and benefits: Enabling 30 yr life 700C+ molten salt reactors to be qualified quickly is key to zero greenhouse gas, low cost nuclear energy generation to supplement variable source renewable energy sources for a stable and expanding electric grid, as well as remote power generation. These materials are also enabling for sCO2 power generation equipment, thermal energy storage systems, and high temperature CSP and thermal energy storage systems for renewable energy and decarbonization. Net shape rapid production of extreme environment materials will reduce costs, lead time, and energy use for production by 50-80%.