Measurement based contribution of 95Zr, 103Ru, 106Ru, 140Ba, 141Ce and 144Ce, to nuclear weapon test fallout.

Philippe RENAUD and Didier LOUVAT 7ième Congrès SPERA (South Pacific Environmental Radioactivity Association) du 13 au 18 mai 2002 à Sydney - Australie.

Contribution of 137Cs and 90Sr in nuclear weapon test fallout are already well assessed, based on extensive measurements results. Activities and relative contributions of other fission products : 95Zr, 103Ru, 106Ru, 140Ba, 141Ce and 144Ce are mainly deducted from fission yield and isotopic activity ratios (UNSCEAR, 1982). In France, from 1961 to 1980, the all set of these fission products have been measured in air, rain and grass on a monthly base. 3000 of these measurements results are used to reconstruct wet and dry deposits as well as transfer to grass for each them. This reconstruction led to conclude that all these nuclides behave in similar way since their emission up to their foliar transfer to grass. This exercise gives a strong support to UNSCEAR hypotheses for deposits of fission products other than Cs and Sr and for their contribution to dose assessment.