Advanced Molten Halide Salt Valves Operation Demonstration

To ensure confident molten salt flow operations within Generation 2 concentrating solar power (CSP) and other advanced >700°C molten salt-based power systems, for Gen 3 CSP and Gen 4 Nuclear Energy (NE), an advanced flow control valve is required. This paper investigates development of two molten salt flow control valves (FCV) for operational demonstration of bellows-style and quick-change packing designs. This innovative high-temperature molten salt valve, with nominal operation at 750°C and 11 bar has been demonstrated using FLiNaK and a ternary chloride molten salt. This work details the general design and flow testing of a bellows-seal FCV. This design includes an integrated closed-loop thermal control system to ensure robust design for freeze-thaw cycles. The design of both valves includes advanced thermal management with ceramic fiber (CF) heaters as well as a novel heat pipe valve stem. This investigation details the development of two high-temperature molten salt test systems that tested these valves up to 750°C and at 11 bar operational pressure. The valve test performed within the Flowserve Corp. Villach test loop employed a DOE Gen 3 CSP (20%NaCl/40%MgCl2/40%KCl by mol. wt. %) ternary chloride salt, while the Kairos Power Isothermal batch test system used FLiNaK (LiF-NaF-KF) as the salt chemistry. The results indicated nominal operation for the two valve systems without the heat pipes at 750°C though with the inclusion of the novel valve stem incorporating these, the temperature gradient along the bonnet was reduced by as much as 210°C, to improve thermal management performance and operational reliability.