DEVELOPMENT OF SODIUM HEAT PIPES FOR NUCLEAR SILENT THERMAL-ELECTRICAL REACTOR (NUSTER-100)

Employing high-temperature sodium heat pipes to remove heat from the reactor core and realizing energy conversion through the cascaded thermoelectric generators, a conceptual design of a 100 kWe level Nuclear Silent Thermal-Electrical Reactor (NUSTER-100) is presented. Aiming at providing sufficient cooling capacity for NUSTER-100, the development of high-performance sodium heat pipes is faced with challenges for the large length-diameter ratio, high thermal power density, material properties decay at high temperature, etc. In this study, the experimental evaluation of the heat transfer performance of sodium heat pipes is conducted. It is found that the maximum thermal load of sodium heat pipes (ϕ30×3×2000 mm) is more than 10 kWt, which shows the design of NUSTER-100 is reasonable and available. Besides, the failure of high-temperature sodium heat pipes is observed. With a high thermal load (> 10 kW) and high temperature (> 1000 °C), the upper part of the evaporator section of sodium heat pipes is overheated, which leads to the breach in the container of sodium heat pipes. Due to the difference in the container material, one small rupture with a diameter of 7 mm (HAYNES® 233™ alloy) and two large ruptures with a diameter of more than 10 mm (stainless steel 310S) occur near the outlet of the evaporator section. Furtherly, the attenuation effect of the oxidation of the working fluid on the thermal performance of sodium heat pipes is verified experimentally. Through heating and oxidating the sodium with a purity of 99.7% in the air at 250 °C for 5 hours, the heat transfer performance of sodium heat pipes with the same specification is compared, in which the heat pipe with the oxidated sodium reduces the heat transfer power by 59.4%. This paper summarizes the research progress of sodium heat pipes for NUSTER-100 and provides data support for the research and development of heat pipe cooled reactor.