RELEASE OF ANTHROPOGENIC XENON TO THE ATMOSPHERE - A LARGE-SCALE ISOTOPE-DILUTION

As a result of the reprocessing of nuclear fuel, the fission products xenon and krypton are released to the atmosphere. Due to their differe nt isotopic composition as compared to natural atmospheric xenon (kryp ton) the dilution process in air results in isotopic alterations in th e blend. The isotopic compositions of fission noble gases were calcula ted for two scenarios. Subsequently blending calculations were carried out in order to simulate the mixing of the fission off-gases with atm ospheric noble gases. In order to estimate the detection limit of the alternations occurring, the calculated isotope ratios in the blend wer e compared to the ratios of natural xenon (krypton) as measured using the highly developed ultra-accurate measurement facilities for isotopi c mass spectrometry at the Institute for Reference Materials and Measu rements. The calculated sensitivity of this method lies within a range of some 10(9) m(3) of air g(-1) fission gas. Finally the potential ap plication of stable isotope measurements of xenon (krypton) as a suppl ementary method for detecting reprocessing activities is discussed.