Development of Corrosion Resistant Bimetallic Structures for Lead-Bismuth Cooled High Temperature Reactor Systems
One of the most promising concepts of advanced high temperature nuclear reactor systems utilizes liquid metal coolants to optimize heat transfer, neutronics, safety, and compactness. Molten lead-bismuth eutectic (LBE) is one of the primary candidates for such coolants due to its unique thermo-mechanical and neutronics properties. The structural components of advanced reactors must be resistant to corrosion from the LBE coolant while being compatible with the materials of the reactor components. Niowave, in collaboration with Los Alamos National Laboratory (LANL), proposes to develop corrosion resistant bimetallic structures for LBE-cooled high temperature reactor systems. The objective of proposed Phase I work was to prototype a candidate bimetal consisting of a niobium corrosion resistant inner layer and 304L stainless steel (ASME code approved) substrate, and then test the bimetal in LBE. The Phase I work scope was designed to test the viability of a candidate LBE corrosion resistant bimetal to move into a robust thermo-mechanical testing in LBE with complex geometries in a Phase II project. During Phase I, Niowave investigated a mechanical bonding process (hydroforming). Stainless steel was chosen as structural material because it is a common structural component in reactor systems and ASME code approved to operate up to 425°C. Niobium was chosen as the protective layer because it has shown excellent corrosion properties in LBE up to 700°C. Three prototype bimetal pipes were manufactured using the hydroforming method by the swage bonding technique. A hydraulic press was used to press oversized nipples through the inner tube, stretching the pipes and forming a compression bond between the materials. The niobium tubes which extend beyond the stainless steel pipes were welded together, and stainless steel chambers were welded around the exposed niobium to fill with argon gas and prevent excessive corrosion. A bimetal cookpot was designed to test the bimetal in argon and LBE environments. The bimetal cookpot was first studied in an inert argon environment. The leak rate of argon through the hydroformed bond (ie through the bond of stainless steel to niobium) was measured as a function of temperature up to 250°C in two experiments. A distinct change in the slope of the measured pressure in the top weld chamber with respect to temperature was observed in both experiments at 150°C, indicating the hydroformed bond is relieved at this temperature. The bimetal cookpot was then loaded with LBE using a conical melter. 5 psig argon was applied in the weld chambers at all times throughout the LBE experiments. The bimetal cookpot was raised to 200°C and the gas pressure in the main chamber was monitored. The LBE in the bimetal cookpot was then melted (150C) and solidified 3 times. Between each process mentioned above, the LBE level was measured from a repeatable position on the top flange. No appreciable LBE was lost during any experiment, showing the hydroformed bimetal is capable of holding liquid LBE at elevated temperatures. A picture of the LBE, which is completely covering the bimetal component of the bimetal cookpot. Ripples are observed because argon is slowly flowing through the hydroformed bond, preventing the LBE from leaking out of the component.
- Research Organization:
- Niowave, Inc., Lansing, MI (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Basic Energy Sciences (BES)
- DOE Contract Number:
- SC0018544
- OSTI ID:
- 1491463
- Type / Phase:
- SBIR (Phase I)
- Report Number(s):
- DOE-NIOW-18544-1
- Country of Publication:
- United States
- Language:
- English
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