分类： 核科学技术 >> 裂变堆工程技术 提交时间： 2023-06-18 合作期刊: 《Nuclear Science and Techniques》
摘要： Ex-vessel steam explosion may happen as a result of melting core falling into the reactor cavity after failure of the reactor vessel and interaction with the coolant in the cavity pool. It can cause the formation of shock waves and production of missiles that may endanger surrounding structures. Ex-vessel steam explosion energetics is affected strongly by three dimensional (3D) structure geometry and initial conditions. Ex-vessel steam explosions in a typical pressurized water reactor cavity are analyzed with the code MC3D, which is developed for simulating fuel-coolant interactions. The reactor cavity with a venting tunnel is modeled based on 3D cylindrical coordinate. A study was performed with parameters of the location of molten drop release, break size, melting temperature, cavity water subcooling, triggering time and explosion position, so as to establish parameters influence on the fuel-coolant interaction behavior, to determine the most challenging cases and to estimate the expected pressure loadings on the cavity walls. The most dangerous case shows the pressure loading is above the capacity of a typical reactor cavity wall.
分类： 物理学 >> 核物理学 提交时间： 2025-03-08
摘要： During severe accidents in pressurized water reactors, thermal and hydraulic interactions play a crucial role in the Fuel-Coolant Interactions (FCI). Motivated to benefit the understanding on the fragmentation behavior of molten metallic fuel in water, in this study a series of simulated experiments is systematically conducted by injecting molten copper into a water pool. By adjusting parameters such as melt temperature, water temperature, melt penetration velocity, and water depth, the effects of these parameters on the fragmentation behavior of molten copper jet are investigated. It is found that water temperature determines the boiling mode during FCI, and at higher water temperatures, molten copper may not solidify and instead reach the bottom of the vessel in liquid form. When the melt temperature rises, the fragmentation process becomes less thorough, leading to an increase in the mass mean debris diameter. Higher penetration velocity of the molten metal results in smaller particles. A water depth greater than 70 cm has little effect on the fragmentation behavior. Weber number theory performs better in predicting the mass mean diameter of debris formed, comparing with the Rayleigh-Taylor and Kelvin-Helmholtz instability fragmentation theories.
分类： 物理学 >> 核物理学 提交时间： 2023-11-29
摘要： The phenomenology involved in severe accidents (SA) in nuclear reactors is highly complex. Currently, integrated analysis programs used for severe accident analysis heavily rely on custom empirical parameters, which introduce considerable uncertainty. Therefore, in recent years, the field of severe accidents has shifted its focus toward applying uncertainty analysis methods to quantify uncertainty in safety assessment programs, known as best estimate plus uncertainty (BEPU). This approach aids in enhancing our comprehension of these programs and their further development and improvement. This study concentrates on a third-generation pressurized water reactor (Gen-III PWR) equipped with advanced active and passive mitigation strategies. Through an Integrated Severe Accident Analysis Program (ISAA), numerical modeling and uncertainty analysis were conducted on severe accidents resulting from large break loss of coolant accidents (LBLOCA). Seventeen uncertainty parameters of the ISAA program were meticulously screened. Using Wilks' formula, the developed uncertainty program code, SAUP, was employed to carry out Latin hypercube sampling (LHS), while ISAA was employed to execute batch calculations. Statistical analysis was then conducted on two figures of merit (FOMs), namely, hydrogen generation and the release of fission products (FP) within the pressure vessel. Uncertainty calculations revealed that hydrogen production and the fraction of fission product released exhibited a normal distribution, ranging from 182.784 kg to 329.581 kg and from 15.6% to 84.3%, respectively. The ratio of hydrogen production to reactor thermal power fell within the range of 0.0578 to 0.104. A sensitivity analysis was performed for uncertain input parameters, revealing significant correlations between the failure temperature of the cladding oxide layer, maximum melt flow rate, size of the particulate debris, and porosity of the debris with both hydrogen generation and the release of fission products.
点击量
通过
点击量
下载量
评论
待评议
