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采用蒙特卡罗(MCNP)程序对置于高通量工程试验堆(HFETR)中的功率跃增辐照考验装置进行物理计算,并采用多优化目标加权评分方法评价不同氦屏结构设计的优劣度。研究结果表明,保持氦屏内侧位置不变时,氦屏气体层的厚度越大,燃料芯块的功率越低;氦屏气体层厚度为2~5 mm时,燃料功率变化范围满足要求,厚度为3~4 mm时较佳。氦屏气体层为3 mm时,氦屏与燃料棒的距离越远,其对燃料芯块处热中子注量率的削减效果越小,对燃料棒功率的控制能力越差,试验时的正反应性引入量呈增大趋势。对于典型装载的HFETR堆芯,处于燃料区域边缘的功率跃增辐照装置,氦屏厚度为3 mm、氦屏内侧冷却水流道宽度为2 mm时的结构为优劣度评分最高的优化氦屏结构。
A Monte Carlo (MCNP) program was used to physically calculate the power jump radiation exposure device placed in a high-throughput engineering test reactor (HFETR), and the multi-objective weighting grading method was used to evaluate the advantages and disadvantages of different helium screen structure designs degree. The results show that when the inner position of the helium shield is constant, the larger the thickness of the helium shield gas layer, the lower the power of the fuel pellet. When the thickness of the helium shield gas layer is 2~5 mm, the range of the fuel power satisfies the requirements. The thickness 3 ~ 4 mm is better. When the helium shield gas layer is 3 mm, the farther the helium shield is away from the fuel rod, the less the effect of reducing the thermal neutron fluence rate at the fuel pellet and the worse the control ability of the fuel rod power. During the test The amount of positive reactivity increased. For a typical loaded HFETR core, the power jump at the edge of the fuel zone increases the irradiance, with a helium shield thickness of 3 mm and a helium shield with a 2 mm wide coolant channel on the inside for the best helium screen structure.