ICONE19-43635 MODERATOR HEAT-LOSS ANALYSIS OF A CERAMIC-INSULATED RE-ENTRANT SCWR FUEL-CHANNEL

Two types of SuperCritical Water-cooled Reactor (SCWR) concepts currently under development worldwide are a large Pressure-Vessel (PV) and Pressure-Tube (PT) Reactors. The current reference fuel-channel design for a PT Reactor, the High Efficiency Channel (HEC), consists of a bundle, ceramic layer and pressure tube. While such a design might work, alternative fuel-channel design concepts are under development to explore various options. One such alternative approach is called the Re-Entrant fuel Channel (REC). The REC consists of three tubes, the inner tube (flow tube), pressure tube and an outer tube or calandria tube. Fuel bundles are placed in the inner flow tube. An annulus is formed between the flow and pressure tubes, through which the primary coolant flows. A ceramic insulator is placed between the pressure tube and the outer calandria tube. The coolant flows through the annulus receiving heat through the flow tube from fuel bundles. At the far end, the flow will reverse direction and enter the flow tube, and hence, the fuel-string. The objective of this work is to model the heat loss to the moderator for the proposed REC design and to compare it with that of the reference HEC design. Two different ceramic insulators were used for the analysis, Porous Yttria Stabilized Zirconia (YSZ) and solid Zirconium Dioxide (ZrO_2). The results from the analysis indicate that YSZ is a better insulator for the REC. The total heat loss from the Porous YSZ insulated REC is about 87 kW, which is approximately 1% of the channel's total power, and is 16.3% less than the heat loss in the reference fuel-channel, i.e., HEC. Based on the results from the numerical model, the design of the insulated REC can be optimized to improve its efficiency.