Prediction of minimum departure from nucleate boiling ratio in VVER-1200 reactor core using heat balance and direct substitution methods

Abstract

Based on the direct substitution and heat balance methods and using the Levitan-Lantsman correlation, a prediction of the minimum departure from nucleate boiling ratio (MDNBR) was made. The equilibrium quality at the exit of the VVER-1200 channel was directly substituted into the correlation to predict the critical heat flux (CHF) while keeping other parameters constant. This was done for 100 %, 105 %, 110 %, until the CHF and the maximum local heat flux intersected each other. The ratio of the CHF and the maximum local heat flux was also recorded for each power level. The point at which the MDNBR intersected the local heat flux was regarded as the operational limit of VVER-1200 with an MDNBR value of 1.445 at thermal power of 160 %. While the point at which the local heat flux intersects the CHF was regarded as the point of CHF occurrence with an MDNBR equaling to a critical power ratio (CPR) value of 1.195 and a CHF value of 1.83 MW m-2. A statistical analysis was carried out to ascertain the accuracy of the predicted MDNBR. Furthermore, a comparison of the result was done with VVER-1200 PCTRAN Simulator, and a good result comparison was achieved