Testing CAN/CSA-N288.1-M87 (Air-to-forage-to-milk or -beef pathways for (sup 131)I and (sup 137)Cs and the water-to-fish and sediment pathways for (sup 137)Cs) against post-Chernobyl observations

摘要

The Canadian Standards Associations 'Guidelines for Calculating Derived Release Limits for Radioactive Material in Airborne and Liquid Effluents for Normal Operation of Nuclear Facilities' is a steady-state chronic release model. Although it has been assumed that predictions usually should be conservative, the model had not been tested. An opportunity to test the model arose due to the activities of BIOMOVS (Biospheric Model Validation Study), which developed several scenarios with which to assess model performance. Each of these scenarios asked for predictions for several steps in the pathways studied (e.g., deposition, concentrations in forage and concentrations in milk or meat). The first of these, Scenario B1, was a chronic release over 30 years of (sup 131)I and (sup 137)Cs; predictions of CSA-N288.1-M87 have been compared with those of the sixteen models participating in the scenario. Scenario A4 was developed using world-wide (sup 131)I and (sup 137)Cs data from the Chernobyl accident, and from the following six months. Predictions made using CSA-N288.1-M87 were compared with observations. In addition, the results were compared with those of the 25 participating models. Finally, the model was used to calculate (sup 137)Cs concentrations in water, sediment and fish in a Swedish lake for 18 months post-Chernobyl, for comparison with observations and other predictions. As assumed, most of the transfer parameters are conservative, so that the predictions are usually conservative for a source term of atmospheric (sup 131)I. However, estimates of deposition for both (sup 131)I and (sup 137)Cs are not conservative, which has profound implications for estimating external dose. Furthermore, at some of the sites in the A4 Scenario, concentrations in milk and beef are underestimated for (sup 137C)s, which suggests that the transfer parameters are not as conservative as might be desired. (author). 5 refs., 7 tabs., 9 figs. (Atomindex citation 27:001123)