engleski

Risk Assessment of a Phosphogypsum Disposal Site

In the Republic of Croatia there is a certain number of radioactively contaminated sites. In order to improve the clean up process of such sites, in March 1993 Croatia joined the international project entitled "Technical Co-operation Regional Project for Countries in Central and Eastern Europe on Environmental Restoration", initiated and co-ordinated by the International Atomic Energy Agency (IAEA). The project is being executed in three separate phases. In the first phase of the project the data on radioactively contaminated sites were gathered, and sites were prioritized according to the pre-set quality criteria. In the second phase, which is currently under way, health risk is being assessed for each of the prioritized sites, so that an adequate clean up procedure could be selected on the basis of a cost-benefit analysis. The very clean-up of contaminated sites falls under the third project phase. The disposal site of phosphogypsum generated by the INA - Petrokemija factory is one of such priority sites for which the radiation risk has been assessed. In the paper, the risk assessment results, which are only a part of the total calculations performed within the second project phase, will be presented. Phosphogypsum disposal site is situated in the vicinity of the city of Kutina, in the continental region of Croatia. It consists of four basins whose total surface is approximately a million square meters. The basins contain approximately 4,5 million tones of phosphogypsum with increased radioactivity, covered by approximately a million cubic meters of water. Phosphogypsum has been deposited there since 1983. It is generated during the production of phosphate fertilizers that makes place in the near by INA - Petrokemija factory, and it is transported from the factory to the disposal site through a pipeline as water suspension. Bearing in mind the properties of phosphogypsum (average concentration of Ra-226 is 670 Bq/kg), of the disposal site and the broader area, three exposure scenarios have been selected to serve as a basis for the assessment of radiation risk. The risk has been assessed separately for the disposal site supervisors, for the most exposed individual and for the local population as a whole. One of the exposure scenarios takes into account the current situation at the disposal site and the neighboring area, whereas the other bear upon predictions of possible situations in the near future. The results relative to the current situation show that both individual and collective risks are within the acceptable values. However, risk of radon inhaled by a disposal site supervisor is close to the acceptability threshold. Results relative to the circumstances that may occur in the near future also show the assessed risk values to be within the boundaries of acceptable risk. On the basis of the obtained preliminary results a regular monitoring of radon concentration at the disposal site as well as measuring the concentration of radionuclides in the ground water is recommended. It is also recommended to perform the risk analysis of other (non-radiation) harmful effects on human health in order to get the more complete picture of potential impact to the human health and environment.

phosphate fertilizers; phosphogypsum; exposure scenarios; risk assessment; clean up

nije evidentirano