PSI contribution to the IAEA study on the radiological situation at the atolls of Mururoa and Fangataufa

Upon the definitive end of the French atomic bomb tests in the South Pacific, the International Atomic Energy Agency (IAEA) was asked to evaluate the radiological situation at the atolls of Mururoa and Fangataufa. The IAEA put up various working groups and invited PSI to participate in the group of geosphere radionuclide transport. Together with the other members of the Working Group, PSI developed models, performed calculations and assessed the radionuclide releases from the various sources and the transport of radionuclides through the geological layers. There were 137 underground sources at Mururoa and 10 at Fangataufa. Release via the groundwater has been assessed for radionuclides which were judged of potential importance, 35 in number. Certain nuclides, notably 3H, 90Sr, 137Cs and 239Pu were investigated in more detail. Data and, partially, model uncertainty was handled by varying the parameters and by comparing differing model concepts. In cases of lack of data ; assumptions were made such that nuclide fluxes are deemed to be overestimated. Calculated results could partially be checked against experimental information. Radionuclide concentrations observed at various test sites are consistent with results from the solution source term model. Calculated releases to the lagoon are generally consistent with measurements. The analysis of all test categories has shown that the radionuclide release to either the lagoon or the ocean is dominated by a few tests. (author)