Abstract
Due to the narrow rectangular channel structure, irradiation damage in high burnup condition would result in local swelling of plate-type fuel cladding, which may cause the coolant channel blockage accident and lead to serious consequences that threaten the integrity of the fuel element, such as decrease of the coolant, increase of fuel element temperature, coolant boiling, etc. More attention should be paid to the safety analysis of flow blockage accidents for plate-type fuel reactor. A series of thermal-hydraulics codes have been developed based on the fuel rod bundle reactor core. Owing to the differences of the flow and heat transfer characteristic, the prediction accuracy of these codes is deficient on the plate-type fuel reactor core. In this study, a parallel channels model has been developed in the thermal-hydraulic code especially for plate-type reactor, in which each rectangular channel was divided into a subchannel. Reasonable mathematic and physical models for plate-type fuel reactor core have been built up to meet the command of the safety analysis under flow blockage accident in nuclear systems. In order to ensure the accuracy and applicability of the code, constitutive models used in the code, such as heat transfer coefficient corrections and flow friction pressure drop models, were fit for rectangular channel and all flow regimes and heat transfer regimes were covered. Both experimental data and the calculated results of Computational Fluid Dynamics (CFD) method under locally blocked conditions were used to verify the code. The comparison results indicate that the key parameters such as coolant outlet temperatures, fuel cladding surface temperatures and average Nusselt number match well with reference data. It demonstrates that the developed code can be preliminarily applied in the thermal-hydraulics analysis for the narrow rectangular channel under flow blockage conditions.
