Radiation situation in the area of the state scientific centre "Research Institute of Atomic Reactors" before putting a multi-purpose fast neutron reactor into operation. Part 1. Terrestrial ecosystems

The paper presents results of radiation survey of terrestrial (natural and agrarian) ecosystems in the 30-km zone around the State Scientific Centre "Research Institute of Atomic Reactors" (SSC RIAR, Institute) before the commissioning of the fast neutron reactor MBIR. Due to long-term emissions during the RIAR operation, 137Cs was mainly emitted into the environment. The most part of the radionuclide activity never extends beyond the border of the Institute sanitary protection zone. In 2011 the average density contamination of the soil with 137Cs was 11.1±6.5 in the sanitary protection zone (0-5 km), 3.1±2.3 in the observation zone (5-12.5 km), 1.3±0.4 kBq/m2 in the influence zone (12.5-30 km). The 137Cs/90Sr ratio is maximum in the soil cover in the sanitary protection zone - 24.5±19.4; it is 8.2±6.8 in the observation zone and it is close to the level of global fallout - 2.0±0.5 in the influence zone. More than 90% of 137Cs is deposited in the 0-5 cm soil layer in forest and meadow cenoses and the radionuclide is deposited at a depth of up to 20 cm in a swamp. The highest 137Cs concentration was found in ecosystems components: in vegetation in the RIAR sanitary protection zone and, to a greater extent, in forest litter. At the initial period of RIAR operation discharges of process water happened, a piece of land of 0.12 km2 was contaminated with 137Cs, 90Sr and 239,240Pu. Over the past 15 years (2005-2020), the density of soil contamination with 137Cs and 90Sr in RIAR zones of observation and influence has been decaying in accordance with the radioactive decay law. It means that no significant emissions from the Institute have been registered. The content of artificial radionuclides in agricultural products and foodstuffs of local production fully meets the established radiological standards and does not have a significant effect on the additional exposure of the population living near RIAR. To assess the impact of the SSC “RIAR" activities on the environment and to assess the radiation safety of the MBIR after putting it in operation, a forecast of 137Cs and 90Sr contamination levels in soils of terrestrial ecosystems within 30-km around the Institute until 2080 was made.