Applicability of the global spectral analysis in X detection for the anthroporadiametric measurement of plutonium 239

In vivo detection of 239Pu within the lung relies on measuring the LX rays which accompany most transuranic radioactive decays. Current limits of detectors for the measurement of lung intake of 239Pu remain high compared with the annual limit of intake. This work was aimed at characterizing the response of a HPGe detector to 239Pu LX rays in different conditions approaching lung monitoring. The measurements were performed using different geometric sources combined with different absorbers and using a realistic chest phantom. The results were analyzed in terms of detection limit with the emphasis on the influence of X ray absorption in the lung and the overlying tissues, or muscle-equivalent thicknesses. The analysis of mixed 239Pu/241Am spectra were investigated using a deconvolution method based on spectra measured in the same geometric conditions for each radioelement. The applicability of this method was assessed with regard to different parameters as activity level, absorption and region of interest. The advantage of using such an analysis method for the interpretation of the mixed spectra is discussed with regard to detection limit and the application of X ray spectrometry in whole body counting. (authors). 5 tabs., 5 figs., 8 refs