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Chlorine-36 in the Biosphere

A number of tasks have been undertaken on Chlorine-36 in the biosphere as part of the BIOPROTA work programme. Those for which reports are currently available are detailed below.

A forum on the behaviour of Cl-36 in the biosphere was held from 27 - 28 September 2006 at Chatenay-Malabry near Paris and was hosted by ANDRA. The workshop was well attended by 33 participants from nine countries, including operators and regulators. Various participants presented their current models for assessing the radiological impact of Cl-36 ranging from those models using equilibrium concentration ratios those using dynamic specific activity approaches. The chlorine cycle and the behaviour of organic and inorganic chlorine was also discussed. The workshop report is available here.

The BIOPROTA programme recently completed a study of Cl-36 behaviour in soils and uptake into plants. Within this study, a significant range of model types and alternative data assumptions were described and compared, demonstrating the degree of understanding of the likely behaviour of Cl-36 in soil and uptake into plants. Quantitative estimates were presented and compared for Cl-36 concentrations in crops based on contaminated water entering surface soil in irrigation water and via upward migration processes from below. Both deterministic and probabilistic assessments were demonstrated and a wide range of sensitivity calculations was also presented. Despite the variations in the models, the results for concentrations in crops were generally within about an order of magnitude of each other. The spread of results obtained in probabilistic calculations did not indicate much greater variation for a given set of site conditions. The report published by ANDRA is available to download.

The project extended the work previously undertaken on the behaviour of Cl-36 in soils and uptake into plants [Limer et al, 2008] to include dose assessment and took into account not only root uptake but also contamination of crops by direct interception of irrigation water. This is so that the relative significance of direct deposition and root uptake can be understood. Special consideration has been given to the assessment of uncertainties, with a clear separation of the contribution to uncertainties arising from:

The report is available to download.