中文摘要：

采用Matlab数据拟合方法及数值计算方法给出校正后的衰减距离。通过Monte-Carlo模拟密度为1.0g/cm^3的聚乙烯材料均匀填充的放射性废物桶,在7个不同的旋转圆周上每隔30°模拟一次探测器计数,得到137Cs点源在桶内7个不同旋转半径上旋转一周的探测器计数,以贡献率较大的部分区域计算给出校正后的平均衰减距离。实验结果显示,通过此方法得到的活度相对误差在0.6%-25.2%之间,相对于传统以桶半径为固定衰减距离计算的结果（相对误差11.8%-209.9%）,误差得到明显降低。说明此方法对提高核废物桶中点源活度估计的准确度是有效的。

英文摘要：

In nuclear waste drum inspection by Segmented Gramma Scanning（SGS）, the detector counts are different with the point sources at different positions during the rotation process, and the attenuation distance needs to be calibrated. We used the Matlab＇s data fitting method and numerical calculation method to get the corrected attenuation distance. The Monte Carlo code was used to simulate the radionuelide in a waste barrel uniformly filled with polyethylene material with density of 1.0 g/cm^3. Then the count distributions of 137Cs point sources at seven different locations in the barrel were obtained. The detector counts were simulated every 30 degrees on seven different rotational circles, and the corrected average attenuation distance was given by calculating the partial area with high contribution rate. The relative error of the activity estimation obtained by this method is between 0.6%and 25.2%. Compared to traditional methods （the relative error of the activity estimation is between 11.8G and 209.9 G）, the error is decreased obviously.