2021:03 Updated radiological risk assessment for the “Radon” type surface disposal facility in Chisinau, Moldova

SSM perspective

Background

Bilateral cooperation between Sweden and the Republic of Moldova in nuclear and radiological safety and security has been ongoing since 2010, focusing on activities aimed at strengthening the institutional capacity of the National Agency for Regulation of Nuclear and Radiological Activities in Moldova (NARNRA) as well as infrastructure development in radioactive waste management, handling and treatment at the Radioactive Waste Management Company`s Special Facilities 5101 and 5102.

In 2019, SSM funded development of a geoscientific and radiological measurement program at the National Radioactive Waste Management site outside Chişinău and provided assistance in carrying out an environmental and radiological risk assessment of a near-surface Radontype facility of historical radioactive waste at the site (Radiological risk assessment for the “Radon” type surface disposal facility in Chişinău, Moldova, SSM Report 2019:12). The objective of the risk assessment was to support future governmental decisions on the possible retrieval and treatment of this legacy waste. The assessment addressed potential future radiological consequences of the disposal facility, i.e. the consequences of migration of various radionuclides for staff, population and the environment, for the case where the disposal facility will remain as before (the zero alternative scenario).

Results

This report is an update of the previous environmental and radiological risk assessment and is funded by the Swedish International Development Agency (SIDA) as part of a project on design and construction of a storage facility for radioactive waste at the National Radioactive Waste Management in Moldova. The updated assessment comprises a dynamic biosphere model based on the site specific data that is compared to the simplified model used in the previous report. In addition, the effect of neglecting interception in the irrigation is evaluated and a set of fully probabilistic simulations and sensitivity analysis are conducted. The updated report confirms the results of the previous assessment of potential radiological impacts of the disposal facility, but also identifies areas that may be considered for further model development.

Relevance

This study is relevant for other countries in the former Soviet Republic with similar legacy radioactive waste disposal sites and so has a wider significance. The combination of the ISAM and updated BIOMASS methodologies and the use of GIS techniques to provide detailed site-specific data from the digital elevation model for the local topography illustrates how practical limits for the well dilution can be estimated from topographic maps of the kind that are often available from national geographic surveys. The used methods here – based on a straightforward interpretation of water balance – can be used to bound well dilution as a first approximation to site-specific conditions. Model results can therefore be used as part of a screening process to determine if more detailed site investigation might be needed. This demonstrates a significant improvement compared to earlier approaches before the advent of GIS (geographic information systems) methods. As a relatively simple and inexpensive approach it has much to recommend it for preliminary studies of potential radiological impact.

Need for further research

Environmental and radiological risk assessment for legacy radioactive waste disposal facilities are essential for decision-making on remediation and retrieval activities. This study demonstrate the use of a simplified approach to guide decision-making on retrieval and remediation. Depending on factors such as the inventory, properties of the disposal facility and its setting and potential radiological consequences, further research may be warranted to justify simplified approaches. There remain significant uncertainties in the representation of the near-surface hydrology that could be addressed by further research.

Project information

Contact person SSM: Viviana Sandberg Reference: SSM2019-12