In Belarus about 1.7 million ha of forestlands have received significant radionuclide surface deposition as a result of the Chernobyl Accident. The mature wood-stand in this area will gradually lose its economical value and quality for a long term, and it is in urgent need of appropriate countermeasures to reduce collective doses and safely reintroduce forest resources. One countermeasure being investigated is the use of contaminated biomass as a fuel for steam and power production. The present study deals with assessment of radiological risks associated with implementing the countermeasure proposed.

Initially, a baseline risk analysis was performed to quantify the radiological doses associated with routine forestry and habitual use of forest products, i.e., in the absence of remediation efforts. Five scenarios were examined: (Sc1a) Exposure due to routine forestry; (Sc1b) Exposure due to recreation; (Sc2a) Exposure posed by domestic use of firewood; (Sc2b) Exposure posed by use of ash as a fertilizer; (Sc3) Exposure due to forest fire. Doses from twelve possible pathways were evaluated within these scenarios.

These risks were then compared to the results of actual measurements of average annual external doses and to those arising from the proposed action (i.e., worker exposure during wood fuel preparation and power plant operation, management and disposal of ash, and releases to the atmosphere during combustion of contaminated fuel).

A generic, multi-pathway exposure RESRAD model was used to calculate individual and collective doses to forestry personal and residents in contaminated area. This model uses site-specific data to describe the pathways and processes of radionuclide movement through the ecosystem, time-dependent radionuclide concentrations, collective doses and human health risks. This model was complemented with COSYMA, LOGMIGR and MCNP4A codes while evaluating the doses within "active" option, i.e. doses to wood-fired power plant's personnel and to residents in the vicinity of the plant.

Three pathways were estimated within the "active" option: (i) external exposure from biomass-fired facilities and ash handled, (ii) external exposure from ash repository, and (iii) inhalation from radionuclide release. To evaluate doses from the identified facilities the Monte Carlo simulations of three radiation sources - fuel, furnace chamber media, and ash - was used to provide the values of energy deposited per a source particle. To convert it to absorbed dose rate values the specific activity of sources in each element of facility was used. The stack release controlled by bag-house and radionuclide distribution in surrounding area was evaluated.

Quantitative risk information obtained will be provided to decision-makers in the Belarus government to support a sound, risk-based decision on the countermeasure.