Scaling Factor Calculation with Robust Regression

The radioactivities of specific nuclides in waste packages have to be declared in accordance with limits and criteria derived from safety assessment of the disposal facility. Some of these nuclides are difficult to measure from the outside of the waste packages because they are alpha or beta emitting nuclides. The scaling-factor method is widely applied in order to evaluate these difficult-to-measure nuclides. The scaling-factor method is based on a correlation between easily measurable gamma emitting nuclides(key nuclides) and difficult-to-measure(DTM) nuclides. Scaling-factor has been calculated by the statistical processing of radiochemical analysis data. Current statistical methods to calculate scaling-factor are geometric mean and the linear regression based on least square. However both methods have a chance to distort the scaling-factor because they are vulnerable to outliers especially in small number of data points. In this study, robust regression (Least Median square, Least Trimmed Square and Reweighted Least Square) is suggested and applied to calculate scaling-factor. These results are compared with the scaling-factors calculated by current statistical methods