management including long term site management and on-site disposal
4 Scientific, technical and regulatory aspects for remediation (including safety and environmental
4.3 Scientific and practical achievements in the field of regulatory supervision during remediation of nuclear legacy sites in the Russian Far East
Sergey Kiselev (SRC FMBC) presented.
Technical bases of the Pacific Fleet were created in the Russian Far East in the 1960s at the Sysoeva and Krasheninnikova bays on the coast of the Pacific Ocean. They maintained nuclear submarines, performing receipt and storage of radioactive waste (RW) and spent nuclear fuel (SNF). The nuclear fleet was decommissioning in the 1980’s and 1990’s, but a lack of regulation resulted in poor storage conditions at these sites. In 2000 the bases were transferred to the ownership of the Ministry of Atomic Energy. Since 2011, the State Atomic Energy Corporation, Rosatom, has been responsible for the former bases.
There are three bases in the Far Eastern region of Russia (Figure 4-4).
FIGURE 4-4.LOCATION OF THE FORMER TECHNICAL BASES IN THE FAR EAST OF RUSSIA.
The Vilyuchinsk site has two shallow ground storage facilities for the temporary storage of high and medium level solid radioactive wastes. No spent nuclear fuel is stored at this site. The main remediation plans for this site are to remove radioactive wastes, demolish storage facilities, and clean up the site to the state of brownfield. The total activity accumulated at the site is approximately 6 x 1014 Bq. Radioecological situation at the Krasheninnikov Bay STS is determined by the presence of artificial radionuclides in the environment at the level of global fallouts values. The only exception is local areas, the remediation of which requires finding optimal solutions.
The Ustrichny Cape and Sysoev Bay sites are quite closely located and have been used for the long-term storage of nuclear submarine reactor compartments and radioactive waste management. The largest challenges are associated with Sysoev Bay where spent nuclear fuel and radioactive waste are managed and high activity liquid wastes are stored. The spent nuclear fuel was removed from this site two years ago, being transferred to Mayak for reprocessing. There remains one building at the site, however, that is in bad condition and where fuel elements are still present. The
remediation strategy for the site is illustrated in FIGURE 4-5. The strategy will be undertaken in different stages. Initially, infrastructure such as roads will be constructed to support waste management activities. Spent nuclear fuel will then be managed with a dedicated management facility being constructed at the site. It is currently intended that a regional center for radioactive waste management will be established, that will include a reprocessing plant.
FIGURE 4-5.STRATEGY FOR THE REMEDIATION OF THE NUCLEAR LEGACY SITES.
As with other sites in Russia, characterization activities have been undertaken to develop an understanding of the environmental contamination present at the site and the site has been divided into three zones, the controlled access area (CAA), HPZ and supervised area (SA). Spent nuclear fuel and radioactive waste storage facilities are situated within the CA. Health protection zone (HPZ) – This is the area to which administrative and technical provisions of the STS relate. The SA is subject to monitoring to ensure the safety of the local population. The zones are illustrated in Figure 4-6.
FIGURE 4-6. THE SYSOEV BAY SITE AND DELINEATION INTO CAA(RED),HPZ(YELLOW) AND SA(GREEN) ZONES. The main challenges at the site arise from the discover ten years ago that RW storage facilities were in poor condition and radioactivity had leaked into the soil, resulting in soil and groundwater contamination. There was also some contamination in the coastal area. Contaminated soils have been found at three locations within the HPZ with concentrations of Cs-137 up to 14 kBq/kg and Sr-90 up to 60 kBq/kg being recorded. Groundwater contamination from radioactivity and chemicals has also been monitored (Figure 4-7). Due to the mobility of Sr-90, it has been found to penetrate to greater depths and enter groundwater whereas Cs-137 is concentrated between 1 and 2 m depth and is found in groundwater at the site in small quantities, not exceeding interventional levels. In general, the ecological situation at the Sysoev Bay STS is characterised by combined environmental impact caused by both radioactive and non-radioactive contaminants.
FIGURE 4-7.CHEMICAL AND RADIOACTIVE GROUNDWATER CONTAMINATION AT THE SERIES OF WELLS AROUND SYSOEV BAY AND CORRESPONDING NORMS FOR DRINKING WATER (BLACK CIRCLE).
Analyses have shown that both radionuclides and metals are present in groundwater at the site (Figure 4-6) and holistic solutions are required that will address both radioactive and chemical contamination issues. At the use of analytical techniques solely, nobody can be sure that all compounds of concern are determined. Also, consequences of simultaneous impact could hardly be forecast both for human or non-human species because of possibility for synergistic or antagonistic interactions. In contrast to the specific nature of the assessment based on exposure, studies of biological effects integrate the impacts of all harmful agents as well as their interactions. So, in addition to radiation and chemical monitoring, biological monitoring has also been used.
Cytotoxicity, genotoxicity and bio-indicators have all been applied to groundwater samples with significant impacts being observed. Chromatid aberrations recognized as damage of moderate severity were prevailing type in aberration spectrum in most samples. However, in a number of samples, there were found an appreciable fraction of genomic disturbances such as laggings and conglutinations. These types of disorders are caused by damage of a spindle and are typical of chemical toxicants. Frequency of chromosome (double) aberrations, which are commonly regarded as radiation markers, is similar to the control in all cases. In total, these data prove the leading role of chemical pollutants in the observed genotoxic effect.
Exposure doses to the local population have also been evaluated. The exposure dose from artificial radioactivity is around 0.3 mSv/y, almost 15 times lower than that from natural sources (primarily radon inhalation).
The former military technical base in Sysoeva bay is therefore a key industrial site for spent nuclear fuel and radioactive waste management in the Russian Far East for which there are a number of ongoing radioactive waste management activities. There also remains a number of challenges at the site resulting from the extensive spread of contamination across the site and disposal of large volumes of industrial wastes located at the site. A key obstacle to cleaning up the site is that there is currently no disposal solution for this category of wastes. The spent nuclear fuel storage facility on the site also presents a danger to the environment and a solution for its remediation is awaited. A full scale, comprehensive monitoring methodology for both chemical and radiation pollution is needed to support effective regulatory supervision at this site based on appropriate estimation of radiological and non-radiological risks.