Rehabilitation programs for nuclear legacy objects in north-western regions in Russia involve decommissioning; a former coast technical support base belonging to the RF Navy and located on the Gremikha peninsula in Murmansk region is now being removed from service. At present spent nuclear fuel is being extracted from ship reactors with liquid-metal coolant and nuclear wastes that have been accumulated during active operations are being treated. The current activities at the site result in complex influence on the environment determined by both radiation and non-radiation contaminants. The present work focuses on examining a hygienic situation existing in residential areas located close to this nuclear legacy object. In general, radiation situation in residential areas is determined by technogenic contaminants, basically 137Cs and 90Sr radionuclides. Our research has revealed that at the moment their contents in the environmental objects correspond to background levels that are typical for the examined region. Chemical contamination detected in residential areas is characterized with elevated heavy metals contents (Cd, As, Pb, V, Zn, Cu etc.) in soils in urban settlements that are higher than background levels. We detected lead and zinc concentrations that were higher than MPC. Total soil contamination with heavy metals (Zc) is still «permissible» in most residential areas. Carcinogenic health risk for people living in the examined residential areas does not exceed 10-6 as per radiation and chemical factors. Research results allow assessing the current hygienic situation as normal and concluding that decommissioning of SZC «SevRAO» objects (Gremikha section) does not exert negative impacts on the environment and health of people living in residential areas located nearby. The obtained data give grounds for controlling activities when environmental monitoring is accomplished during works aimed at recovering contaminated areas where nuclear legacy objects are located.

Algorithm for management of decision-making on the decommissioning of nuclear and radiation hazardous objects (RHO) should be both based on an comprehensive approach, with taking into account all the potential dangers, and relied upon on the requirements of a modern regulatory framework, as well as economically sound and socially oriented. The aim of the work was a development of a comprehensive approach to the assessment of the degree of the potential danger of near surface radioactive waste repositories in RHO, on the base of which it is possible to make substantiated management decisions for their decommissioning. Tasks: To develop an array of radio-ecological approaches, including radiation-hygienic, hydrogeological and engineering criteria for the assessment of the potential danger of radioactive waste repositories. Results There are presented radiation hygienic, hydrogeological and engineering and technical criteria on the basis of which there are calculated coefficients of the relative hazard of storages. In dependence to the value of the coefficients there are suggested four categories of danger - a safe, low dangerous, dangerous and very dangerous. There are elaborated approaches on management decisions-making in various variants of decommissioning - the conversion, renovation, conservation and liquidation.

In this article there is considered the experience of carrying out works on the reclamation of objects and territories contaminated by technogenic alpha emitters. The paper presents main criteria for monitoring the radiation safety of premises, provides a rationale for the residual activity for decontamination, control levels for control of pollution by technogenic alpha emitters of working surfaces, and justification of the criteria for the acceptability of radiation-safe buildings.

The article describes the evaluation of the efficiency of using the technology of dry method of decontamination of α-radionuclides from working surfaces of premises for different materials, equipment and building structures. Materials and methods. Instruments for measuring of ambient dose equivalent rate (ADER) with a lower limit of 0.03 μSv/h. Specific activity of α-radionuclides in the samples was determined by radiometric, radiochemical and spectrometric methods using standard methods in the accredited laboratory. The measurements in situ were also carried out using the ISOCS «CANBERRA» mobile gamma-ray spectrometry system with high purity germanium detector and a collimator. Technological equipment included industrial vacuum cleaner with nozzles; high-pressure device; packing sets for RAW collection; HEPA filters; personal protective equipment. Results. Maps of spatial distribution of surface α-contamination in the building was constructed. We performed cluster analysis of data for zoning of contaminated surfaces. The decontamination factor for porous (brick, concrete), smooth (wood, brown tiles, laminate) and sticky (bitumen, mastic) surfaces was determined. Conclusion. The cluster analysis made it possible to identify 4 levels of surface α- and β- contamination, particles/cm2 ∙ min: zone I - for α- above 50, for β- above 10,000; zone II - for α- 5-50, for β- 2,000-10,000; zone III - for α- no more than 5, for β- 2000; zone IV - corresponds to the background values of the workspace surfaces. The dry decontamination method revealed a high content of fine dust aerosol fraction deposited in the lungs. To increase the efficiency of dust suppression, water aerosol with droplet size of 100 - 400 microns and quartz sand with particle size of 100-200 microns were sprayed at the rate of 200-400 g per 1 m2. The decontamination coefficient depends on the coating material and the level of surface contamination: concrete - 91 to 97.8%; brick - 85-86%, wood - 38.8-53%; brownstone tiles - up to 29%; mastic - 22-28%; bitumen - 15.9-20%. To protect the personnel, radiation-hygienic rationing of PM10 and PM2,5 content is necessary.

The global pollution of the environment and the functioning of the Mining and Chemical Combine (MCC), Rosatom State Corporation are potential sources of tritium in the Yenisei River ecosystem. The distribution of residual tritium in organs and tissues of the freshwater rayfinned fish Carassius gibelio (Prussian carp) as a representative of the Carassius phytophagous genus of Cyprinidae family was studied for the determination of the 3Н accumulation in the aquatic plants-fishes food chain in water bodies contaminated with radionuclides. At the first stage, the work was done on the accumulation of tritium by the biomass of hydrobiont plants. To do this, 3000 g of biomass in terms of wet weight were placed in aquaria with a volume of 100 liters with specific water activity of 100 kBq/l. The work shows mentioned aquatic plants to accumulate actively the introduced tritium, storing up to 70% of the radionuclide. At the same time, the content of organically bound tritium in biomass increased to 21% of total accumulated tritium. Then the plants (hornwort, duckweed) were dried, mixed with dry fish food (1: 1), and the mixture was compressed into pellets, each with activity up to 50 Bq. The pellets were used for forcible feeding of fish, during the experiment, each individual absorbed up to 330 kBq of tritium radionuclide for 550 days. Studies have shown about 75% of the total accumulated amount of tritium in fish specimens to present in muscle tissue. When determining the content of tritium in proteins and lipids in experimental systems, no specific features have been revealed in the use of Ceratophyllum and Lemna as a source of nutrition.