Evaluation of Shutdown Gamma-ray Dose Rates around the Duct Penetration by Three-Dimensional Monte Carlo Decay Gamma-ray Transport Calculation with Variance Reduction Method
Evaluation of Shutdown Gamma-ray Dose Rates around the Duct Penetration by Three-Dimensional Monte Carlo Decay Gamma-ray Transport Calculation with Variance Reduction Method
复制标题
三维蒙特卡罗衰变伽马射线输运计算方差减少法评价管道贯穿部位停堆伽马射线剂量率
DOI：
10.1080/18811248.2002.9715316
复制
发表时间：
2002
影响因子：
1.2
通讯作者：
T. Nishitani
中科院分区：
文献类型：
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作者：
S. Sato;H. Iida;T. Nishitani
为了评估核聚变反应堆停堆后导管穿透处周围的伽马射线剂量率，提出了应用蒙特卡罗中子和衰变伽马射线输运计算的计算方法。对于运行期间的放射性同位素产率，蒙特卡罗计算是通过修改核数据库，用衰变伽马射线谱代替提示伽马射线谱来进行的。通过将每个校正因子（即停工后实际激活水平与运行期间产量之比）与每种放射性同位素引起的每个衰变伽马射线通量相乘，可以评估衰变伽马射线剂量率。为了改善统计误差，提出了一种应用加权窗口重要度技术和衰减伽马射线产生位置规范的方差减小方法。我们确定了在评估点产生衰减伽马射线的能贡献衰减伽马射线通量的单元，并强制终止除已确定的单元外的其他单元的伽马射线输运计算。为了验证该方法的有效性，对ITER （International theruclear Experimental Reactor）实际配置进行了屏蔽计算，得到了小于准则的较小统计误差。实验证明了该方法在ITER设计分析中的有效性。
For the evaluation of gamma-ray dose rates around the duct penetrations after shutdown of nuclear fusion reactor, the calculation method is proposed with an application of the Monte Carlo neutron and decay gamma-ray transport calculation. For the radioisotope production rates during operation, the Monte Carlo calculation is conducted by the modification of the nuclear data library replacing a prompt gamma-ray spectrum with a decay gamma-ray spectrum. By multiplying each correction factor, which is ratio of the actual activation level after shutdown to the production rate during operation, with each decay gamma-ray flux due to each radioisotope, the decay gamma-ray dose rate is evaluated. In order to improve the statistical error, a variance reduction method is proposed by the application of the weight window importance technique and the specification of the decay gamma-ray generation location. We identify the cell producing the decay gamma-ray which can contribute the decay gamma-ray flux in evaluation locations, and forcibly terminate the gamma-ray transport calculation in the cells except for the identified cells. In order to validate the effectiveness of the method, shielding calculation for actual ITER (International Thermonuclear Experimental Reactor) configuration is performed, and small statistical errors below criteria are obtained. The effectiveness of the proposed method for ITER design analysis is demonstrated.