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Comparison of Different Models in Case of Plomin Site Contamination Analysis

In the past few years radioactively contaminated sites and their clean-up have made it to the list of topical environmental issues with both professionals as well as general public. TE Plomin site, situated in the western littoral area of the Istrian peninsula, some ten kilometres north-west to the town of Labin, within the complex of the power plant carrying the same name, is a good example of such a site. It contains 700.000 m3 of radioactively contaminated slag and ash, covering the area of 120.000 m2. Slag and ash have continuously been accumulated there since 1971 as a result of burning coal with naturally elevated radioactivity level in the boiler plant. Application of quantitative methods for the assessment of impacts on human health and environment is a crucial step in the process of making a decision on possible clean-up procedures of contaminated sites. That is why a number of models have been designed, each of them tackling the problem in a different way, within a more or less limited scope, with a higher or lower level of precision. In the case of TE Plomin site doses were calculated by RESRAD and GENII computer codes and PATHRAE method. Doses received are relevant to an individual who spends some time at the site every day, and they are inclusive of contributions from the direct radiation of the deposited material and inhalation of contaminated particles. The highest cumulative doses were obtained by RESRAD code, and the lowest by GENII code. It has been established that, regardless of the method or code applied, the doses received from the direct radiation of deposited material are several times higher than the doses received by inhaling contaminated particles. It has also been established that aberrations encountered in cumulative doses are due to differences in models and dose conversion factors for the calculation of doses from the direct radiation. Generally speaking, it can be said that uncertainty of input data determines the level of conservativeness in the approach to analysis. Since in this case the uncertainty of some input data was substantial (this refers to specific activity of radionuclides, concentration of contaminated particles in the air, as well to a series of data associated with the exposure scenario), the authors feel that the results obtained by the RESRAD code should be considered more reliable than the others.

radioactively contaminated sites; clean-up; RESRAD; GENII; PATHRAE

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