DETECTION OF REPROCESSING ACTIVITIES THROUGH STABLE-ISOTOPE MEASUREMENTS OF ATMOSPHERIC NOBLE-GASES

Noble gas stable isotope abundance measurements may provide a tool for detecting reprocessing activities of nuclear fuels. An approach has b een made by carrying out blending calculations of released fission xen on and krypton in air using the Isotope Mixture Programs which have be en developed at the IRMM. After having obtained a reliable approximati on to the expected range of the isotope ratios in the blends and the r espective detection limit thereof through these calculations, the pote ntial application of ultra-accurate measurements of the isotopic compo sition of anthropogenic and atmospheric noble gases is taken into cons ideration. Also the important role of radiometric measurements of Kr-8 5 and Xe-133 for the detection of nuclear fuel reprocessing is taken i nto account. The information provided by such activity measurements is limited, therefore a method to calculate the initial isotopic composi tion of released fission noble gases, through measuring of their atmos pheric mixing ratio, is presented and discussed. Highly accurate stabl e isotopic measurements of atmospheric noble gases might provide more detailed information on the ''history'' of the reprocessed nuclear fue l. Therefore they could serve, in combination with radiometric detecti on techniques, as an excellent tool for the identification of reproces sing activities.