Critical Heat Flux Measurements in a Full Scale Rod Cluster

抄録

Critical heat flux data obtained for boiling water flow with a full-scale rod cluster of a water cooled reactor. The tests were performed on the effects of unknown parameters such as rod cluster eccentricity, spacer pitch and fuel configuration. From the experiment, the following conclusions are obtained : 1) The existence of low and high flow velocity burn-out regions was confirmed for rod cluster and the boundary between these two regions was almost the same as that for the round tube. 2) Rod cluster eccentricity has a marked effect on burn-out. An eccentricity of 0.6 mm lowers the critical heat flux by approximately 20%. 3) Burn-out is affected considerably by spacer pitch. If the spacer pitch is changed from 420 mm to 260 mm, critical heat flux increases by 38% maximum. 4) Critical heat flux can be increased by improvement of the fuel configuration. Test conditions were as follows ; pressure 70 kg/cm², mass velocity 0.1∼10.7 × 10⁶ kg/m²h, inlet subcooling 5∼200 kcal/kg, eccentricity 0∼1.0 mm and spacer pitch 260∼420mm.