STEAM-WATER TEST ANALYSIS ON TWO-PHASE NATURALCIRCULATION AND HEAT TRANSFER OF THE INTEGRATEDMODULAR WATER REACTOR (IMR) USING RELAP5

摘要

The Integrated Modular Water Reactor (IMR) hasrnbeen developed as an advanced small-sized reactorrngenerating 1000 MW of thermal power, featuringrninnovative technologies to attain the economyrncompetitiveness and high-level of safety. The IMRrnadopts Hybrid Heat Transport System (HHTS) as itsrnprimary cooling system. The HHTS enablesrnself-pressurization in reactor vessel and eliminates thernneeds of recirculation pumps and associated piping,rnby employing two-phase natural circulation with thernin-vessel steam generators. The performance of thernHHTS was investigated by conducting steam-waterrnhigh-pressure tests, simulating the actual IMR's operating condition. The test loop is a 1/17540-scaledrnof volumetric ratio, with actual axial height. Itrnsimulates internal components inside the reactorrnvessel. Afterwards, posttest analyses are performedrnusing RELAP5/Mod3.2 code. The objectives of thernanalysis are to clarify the thermal-hydraulic and heatrntransfer characteristic of the IMR under two-phasernnatural circulation, and to benchmark the applicabilityrnof the code by identifying discrepancies andrnuncertainties. Typical cases for corresponding testsrnwere simulated using the RELAP5, ranging fromrnlow-pressure-low-power to high-power-high-pressurernstates. In-depth assessment of the results demonstratesrnthe applicability of the code for adequately predicting the IMR experimental results. Discrepancies occur inrnestimating void fraction, vapor flow rate ratio and thernliquid-vapor separation process. The discrepanciesrncould be solved by applying and modifyingrnappropriate drift-flux correlations for void fractionrncalculation.