Reflood heat transfer data analysis and model assessment

Reflooding in a postulated large break LOCA is the key to emergency core cooling system effectiveness assessment and reactor safety margin evaluation. In order to provide experimental support for large advanced pressurized water reactor safety analysis, China Institute Atomic Energy has performed the 8 × 8 rod bundles reflood heat transfer test. The test result showed that spacer grid with mixing vanes would enhance heat transfer. The effect of injection water flow rate, injection water temperature and heating power on rewetting velocity was studied. The experimental values of rewetting velocity are compared with the one-dimensional and two-dimensional heat conduction controlled theories. The RELAP5/MOD3.3 reflood model is assessed against the test data. Comparison of code prediction and measured data indicates that the code predicts quench time relatively well but the peak rod temperature differs. (authors)