Advances in human internal radiation counting at Los Alamos Multiple simultaneous in-vivo measurements

In order to improve the health physics surveillance programme for radiation workers at the Los Alamos Scientific Laboratory, the In-Vivo Measurements Laboratory at LASL is being upgraded to provide four separate, yet simultaneous, photon spectral measurements on a single individual, with each spectrum providing different information. The four spectra are acquired with the following four detectors for the respective energy regions: (i) the NaI portion of twin phoswich detectors placed over the chest of the subject, monitoring the 10-140 keV photon region (for plutonium isotopes and 241Am); (ii) the CsI portion of the same phoswich detectors, monitoring the energy region from 200-2000 keV (for background radiation, 137Cs, etc.); (iii) a large planar hyperpure germanium detector placed directly over the liver area of the prone subject, monitoring the region 10-250 keV (for gamma activity in special organs); and (iv) a large volume Ge(Li) detector placed directly under the prone subject, monitoring the region 55-2000 keV (for 137Cs, etc.). Data analysis is performed on-line by a minicomputer, with printer output and permanent data storage on floppy diskettes. The simultaneous countings allow potential health physics problems to be identified earlier and provide a more comprehensive monitoring programme at no increase in operating costs and only a modest increase in capital costs. (author)