Magnetic Bearing Supported Impeller for Molten Salt Reactor Pump

Molten salt reactors (MSR) use molten salts as both a carrier of dissolved fission materials and coolant. Reliable high temperature impeller type pump is indispensable for the safe operation of future MSR. The mechanical pump is considered to be ideal for pumping high temperature and corrosive molten salts compared to the electromagnetic pump because of its efficiency. However, the mechanical pump requires mechanical rolling ball bearings and dynamic sealing, which causes the maintenance issue. The technical objective is to develop a high-performance pump using a high-temperature magnetic bearing supported impeller that meets the load, speed and high temperature requirements. Since the impeller is levitated, this pump has a unique advantage that no direct contact of moving parts with the chemically aggressive melt is necessary. The proposed pump design is much simpler and cost-effective in terms of maintenance and system integration. In particular, using Electron Energy Corporation (EEC)’s high- temperature magnetic bearing and coupler technology will improve the pump performance. The proposed novel magnetic bearings combine permanent magnets for supplying the bias field and electromagnets for supplying the control field, both in high-temperature conditions. This reduces power consumption, power electronics costs and overall system size due to a reduced number of coil turns. The ultra-high-temperature permanent magnet materials (US patent 6,451,132) developed solely by EEC can withstand temperatures up to 550°C without significant magnetic strength degradation. The 6-pole homopolar design permits uninterrupted force delivery via a redundant control capability (US patent 7,429,811) even if 3 poles were to fail. In Phase I, the magnetic and mechanical designs of high-temperature magnetic bearing supported impeller and co-axial magnetic coupler were developed. The pump performance was evaluated by thermodynamic and CFD flow studies. The capability, reliability, complexity and risk management associated with development and implementation of the pump were studied and compared. Based on various strengths and weaknesses of design options, a final pump design was selected for the technology demonstration. EEC’s permanent magnet material samples was produced for thermal stability test for Phase II prototyping. In Phase II, two prototypes will be manufactured at EEC’s facilities, where we have the infrastructure necessary for the complete fabrication. The first unit will be tested for proof-of-principle purpose. The second unit will be refined, if necessary, and its performance testing in relevant MSR environments will be carried out to provide insight for further improvement of the pump efficiency and performance. In Phase III, EEC, working with commercial pump manufacturers such as Nagle Pumps, CMI Novacast, Hayward Tyler or Creative Engineer, will optimize the technology to produce full size pumps and develop guidelines for system manufacturing and software control. Once successfully completed, this project will significantly extend the operating environment capability for MSR applications such as nuclear power, concentrated solar power, fossil fuel, geothermal, and shipboard propulsion. The further advancement of high-temperature magnetic bearing will also strengthen the US position in permanent magnet technology, which is presently heavily dominated by China. Many actuators, motors, generators and other magnetic bearing applications will greatly benefit from the proposed work.