Numerical calculation of detection efficiency of response functions of Segmented Gamma Scanning system
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摘要: 基于SGS探测系统中放射性核废物桶、准直器及HPGe探测器的空间几何分布建立数学模型。对低、中放射性核废物桶中点源137Cs的探测效率响应函数进行了数值公式推导，然后利用蒙特卡罗工具包MCNP模拟计算了相应的效率函数。将这两种方法模拟的结果进行了对比分析发现：数值计算方法的数据普遍高于MCNP模拟的数据，最大相对误差达143.26%，误差平均值为37.15%。对数值计算方法进行修正后，最大值相对误差为17.22%，平均值为4.54%。在误差范围内，可以认为该修正方法有效。Abstract: The research of Segmented Gamma Scanning(SGS) technique is mainly focused on two aspects: self-absorption correction of waste drum and efficiency calibration of the system. For the purpose of self-absorption correction, it is necessary to calculate the scanning efficiency. In this paper, a mathematical model was established for the correction, which was based on the spatial distribution of radioactive waste barrels, collimators and HPGe detectors in SGS detection systems. In addition, calculation of the detection efficiency of midpoint sources (Cs-137) in low and intermediate level radioactive waste steel drum was managed. Then the calculation corresponding to efficiency function based on MCNP method was operated as well. The results of the two methods were compared with the numerical calculations. It was found that the results from numerical calculation was usually larger than that from MCNP simulation and the maximum relative error reached 143.26% whereas the average error was 37.15%. After correction the maximum error was reduced down to 17.22% and the average value was 4.54%, which indicates that the model is scientific for the temporary storage, transportation and final disposal of the waste bucket.
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Key words:
- Segmented Gamma Scanning(SGS) /
- detection efficiency /
- numerical calculation /
- MCNP
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图 5 探测效率响应函数随旋转角度的关系曲线
Figure 5. Relation curve of the detection efficiency response function and rotation angle
图 9 修正前后探测效率响应函数与MCNP模拟值的结果对比
Figure 9. Comparison of results before and after correction of relative error
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