Numerical Study of the Impact of the Fuel Rod Swelling on the Thermal Hydraulics in 2X2 Rod Bundle

摘要

1. According to the results of the simulations, the blockage in the flow channel caused by the cladding swelling will increase the pressure drop. If the blocked ratio is big enough, negative pressure will appear at the blocked region, which will lead to the back flow. 2. From the results in this investigation, the secondary flow intensity in the blocked region will go up and down according to the geometry of the corresponding location, the tapered section, the maximum blocked section and the divergent section. While the blocked ratio equals 60% the secondary flow intensity will decrease in fluctuation near the outlet of the blockage. Besides, whether the blockage benefits the secondary flow intensity or not is decided by the blockage ratio. 3. Based on the results of the simulations, when the blocked ratio equals to 40%, the temperature distribution is more uniform in the blocked region than that of the normal models. A blockage ratio of 60% will increase the non-uniformity of the flow field. In general, the blockage would benefit the thermal distribution downstream of the blockage region. 4. More optimized indexes are needed to evaluate the overall effect of the blockage on the thermal hydraulics of the coolant.