Developing reliable high-temperature molten salt pumps remains a technical challenge for the advancement of Molten Salt Reactors (MSRs). A critical component of these pumps is the shaft seal, which is essential for preventing salt leakage and the release of radionuclides. To support the development of shaft seal technologies, this study investigated a commercially available promising candidate: circumferential bushing seals. A high-temperature molten salt Shaft Seal Test Facility (SSTF) was designed and constructed to evaluate the static and dynamic performance of the bushing seal. In SSTF, the bushing seal was exposed to FLiNaK salt vapor and cover gas mixtures at temperatures and gauge pressures up to 550 °C and 67 kPa, respectively, with varying shaft rotation speeds up to 1500 RPM. A series of experiments was conducted to evaluate the static and dynamic performance of the bushing seal under MSR operating conditions. A 10-day wear-in (transition) phase was observed, during which graphite bushing wear influenced the pressure field. At steady state, both shaft speed and temperature exhibited negligible impacts on seal performance. Experiments using three different cover gases, i.e., nitrogen, helium, and argon, indicated argon was preferred as it maintained higher pressure at the same flow rate and lower cost. Transient experiments showed that shaft ramping speed and profile had negligible impacts. • A high-temperature molten salt pump shaft seal test facility was developed. • A graphite circumferential bushing seal showed reliable performance. • Initial wear-in phase led to radial clearance growth. • Both shaft speed and temperature demonstrated negligible impacts on seal performance. • Argon exhibited superior performance under the conditions investigated as cover gas.
Che et al. (Thu,) studied this question.