Improvement of Radiolytic Gas Model for Criticality Accident Analysis of Nuclear Fuel Solution System
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摘要: 对瞬态临界事故的准确模拟是核燃料溶液系统临界安全评估的关键因素。现有的辐解气体模型经验参数较多，导致功率特性预测存在较大偏差。为提高模拟精度和避免对模型中经验参数取值的依赖，需对辐解气体模型进行改进。基于对溶液中辐解气体行为的分析和简化假设，建立了包含辐解气体浓度、辐解气泡单位体积物质量和气泡数量密度的守恒模型，并将其与点堆中子动力学模型和二维导热模型相耦合，开发了溶液系统二维瞬态分析程序，通过日本TRACY实验进行了验证。结果表明，程序模拟值与实验数据符合较好，程序模型能够准确模拟溶液系统临界事故的功率变化。Abstract: The accurate simulation of transient criticality accident is a key factor in critical safety assessment of nuclear fuel solution system. However, the existing radiolysis gas models contain many empirical parameters, which result in significant deviations in the prediction of the power characteristics. To improve the simulation accuracy and avoid relying on the empirical parameters in the model, the radiolytic gas model needs to be improved. Based on the analysis of radiolysis gas behavior in solution and simplified assumptions, a conservation model including radiolytic gas concentration, mass per unit volume of radiolytic bubbles and number of density bubbles was established. This model was coupled with a point reactor kinetics model and a two-dimensional heat conduction model to develop a two-dimensional transient analysis code for solution systems. The code was verified with the Japanese TRACY experiment. The results show that the simulated values of the code are in good agreement with the experimental data, and the improved model can accurately simulate the power change of the solution system during critical accidents.
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Key words:
- Nuclear fuel solution system /
- Critical safety /
- Radiolytic gas model
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图 2 TRACY R100工况功率与温度模拟结果
Figure 2. Power and Temperature Simulation Results for TRACY R100 Experiment
图 3 TRACY R072工况功率与反应性模拟结果
Figure 3. Power and Reactivity Simulation Results for TRACY R072 Experiment
图 4 TRACY R072工况平均临界浓度、溶解氢气平均浓度、平均平衡浓度和气泡平均数量密度模拟结果
Figure 4. Simulation Results of Average Critical Concentration, Average Dissolved Hydrogen Concentration, Average Equilibrium Concentration and Average Number Density of Hydrogen Bubbles for TRACY R072 Experiment
图 5 TRACY R072工况气泡平均半径和空泡份额模拟结果
Figure 5. Simulation Results of Average Bubble Radius and Average Void Fraction for TRACY R072 Experiment
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