ROOT UPTAKE OF RADIONUCLIDES IN AGRICULTURAL ECOSYSTEMS

BALONOV, M; VELASCO, H; Y COLABORADORES

HANDBOOK OF PARAMETER VALUES FOR THE PREDICTION OF RADIONUCLIDE TRANSFER IN TERRESTRIAL AND FRESHWATER ENVIRONMENTS

INTERNATIONAL ATOMIC ENERGY AGENCY

Lugar: Vienna; Año: 2010; p. 39 - 77

The impacts of planned discharges of radionuclides to the environment are assessed by means of mathematical models that approximate the transfer of radionuclides through the compartments of the environment [1]. These models can be used as tools to evaluate the effectiveness of countermeasures applied to reduce the impacts of accidental releases of radionuclides and to predict the future impact of releases from underground waste repositories. In all these applications, the reliability of the predictions of the models depends on the quality of the data used to represent radionuclide transfer through the environment. Ideally, such data should be obtained by measurements made in the environment being assessed. However, this is often impracticable or overly costly, and thus there is heavy reliance on data obtained from the literature. Often such data can provide an estimate of the radiological impact of a planned release to satisfy regulatory requirements. Only when the estimated radiation doses to humans approach nationally established regulatory limits is a more site specific approach needed. Similarly, the potential impact of accidental releases and of releases in the far future can usually be adequately assessed using such generic data sets. The International Atomic Energy Agency (IAEA) has for many years supported efforts to develop models for radiological assessments [1, 2] and to assemble sets of transfer parameter data, and in 1994 it published a collection of data for estimating radionuclide transfer in the terrestrial and freshwater environments (Technical Reports Series No. 364) [3]. The IAEA also published a similar collection relevant to transfer in the marine environment, which was updated in 2004 [4]. These data collections draw upon data from many countries of the world and have come to be regarded as international reference values. Since the publication of TRS-364 [3], new data sets have become available, and an update of the report was considered appropriate. The present publication supersedes TRS-364 [3] and includes considerably expanded information on ecosystems other than temperate ecosystems, on radionuclides, and on processes to be taken into account in the assessment of the radiation impact of radionuclide discharges to the terrestrial and freshwater environments. The data included here relate mainly to equilibrium conditions, that is, they relate to the conditions where equilibrium has been established between the movements of radionuclides into and out of the compartments of the environment. Such a situation may exist during the controlled and continuous release of radionuclides to the environment from a nuclear facility. In the case of short term releases, as might occur in the event of an accident, equilibrium cannot be assumed, and the rate of transfer between compartments must be assumed to vary with time. Some data relevant to time dependent radionuclide transfer in the environment are also included in this publication, for example, data on weathering and translocation for foliar uptake, on the long term dynamic of transfer factors for root uptake, and on some processes in semi-natural ecosystems.