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Sediment and aquatic plants were collected annually since the early 1990s in the main French rivers, upstream of nuclear power plants. These time series were used in order to assess the parameters of a compartmental model describing the Chernobyl-derived 137Cs flux from soil to rivers. In order to reduce the dispersal of 137Cs measured activities in sediment samples due to the granulometric heterogeneity, a correction method was set up using sediment test-fractions artificially enriched with specific diameter particles. The method was based on 137Cs affinity for fine particles, especially clays, and thus clay and fine silt contents of each sample was analysed. Corrected sediment data showed (1) that the method efficiently reduced the variability; and (2) that 137Cs activities in French rivers decreased with a half-life of 4 to 6 years since 1987 (after correction by radioactive decay). A similar half-life value was obtained for aquatic plants pointing out that this half-life is related to the gradual decay of the flux from soil to rivers, not to the indicator itself. Comparing our results with similar ones published by other authors, it appeared possible that this kinetic varies with the time period over which the study is conducted, the longer the period the lower is the kinetic. [Copyright &y& Elsevier]

Abstract: In order to assess the level of residual radioactivity and evaluate the radiological conditions at the former French nuclear testing sites of Reggane and Taourirt Tan Afella in the south of Algeria, the International Atomic Energy Agency, at the request of the government of Algeria, conducted a field mission to the sites in 1999. At these locations, France conducted a number of nuclear tests in the early 1960s. At the ground zero locality of the ‘‘Gerboise Blanche’’ atmospheric test (Reggane) and in the vicinity of a tunnel where radioactive lava was ejected during a poorly contained explosion (Taourirt Tan Afella), non-negligible levels of radioactive material could still be measured. Using the information collected and using realistic potential exposure scenarios, radiation doses to potential occupants and visitors to the sites were estimated. [Copyright &y& Elsevier]

The natural nuclear fission reactor at Bangombe´ is located at a depth of approximately 12 m and has undergone supergene weathering and chemical exchange with groundwater under moderately oxidizing conditions. This reactor has been studied as an analogue for the migration of radionuclides in a geologic repository. Five water samples were taken from a drill hole in the reactor zone and from drill holes that are situated along the direction of the groundwater flow. Dissolution of phosphates in the weathering profile provided an important mechanism for the mobilization of phosphorous and REE. This phosphorous allowed the formation of secondary minerals, e.g., phosphatian coffinites and Fe-uranyl phosphate hydroxide hydrates. The filtered groundwaters (dissolved phase) obtained directly from the reactor zone had anomalous 143Nd/146Nd, 145Nd/146Nd and 149Sm/147Sm isotope ratios of 0.7235, 0.4933 and 0.843, respectively, confirming mixing between a fissiogenic and normal REE component. In this dissoved phase, a small fraction of the Nd (2.3 at.%) is of fissiogenic origin. The suspended loads (filtered particulates) of the same groundwater from within the reactor show similar isotopic anomalies with a fissiogenic Nd contribution of 3.2 at.%. Similar fissiogenic Nd contributions are observable for groundwater samples from outside the reactor zone (3 m distance). Both dissolved and suspended load samples from the more distant well (25 m) have normal isotopic ratios. Thus, the prevailing physico-chemical conditions within this groundwater system allow the migration of the fissiogenic REE over at least 3 m but less than 25 m. Although REE phases are abundant in the reactor zone, the REE concentrations of the water in contact with the sediments of this zone are very low (<17 ppt). The most important lanthanide- and actinide-bearing phases are uraninite, coffinites and Fe-uranyl phosphate hydroxide hydrate. The presence of all of these phases retards the mobility of the fissiogenic lanthanides and actinides. [Copyright &y& Elsevier]