Development of insulating system for FBR electro-magnetic pump

Development of sodium immersed type electro-magnetic pumps (EMP) is expected to improve the reliability, safety, maintainability, and construction cost of FBR compared with the conventional mechanical pumps. To realize electro-magnetic pumps, establishment of a high-temperature-resist electrical insulating system is indispensable. The authors had selected a mica-alumina combination for the insulating system at temperatures higher than 500°C. Using this insulating system, an ageing pre-test was performed. The ageing condition was to apply 1.5 kV AC voltage in a nitrogen atmosphere at 550°C for 4000 hours. The dielectric properties before and after ageing were measured to understand the tendency of temporal change in ageing. In this result, dielectric performance after ageing was improved compared with the initial one. This phenomenon was clarified to be caused by a decrease of organic component in the insulation. Also, the possibility of the thermal runaway was considered to be higher as a dielectric breakdown mechanism