Impacts on the terrestrial environment in case of a hypothetical accident involving the recovery of the dumped Russian submarine K-27.

Objects containing radioactivity have been routinely dumped in Arctic waters near NW Russia up until the 1990s. One of the most radioactive objects in this region, the nuclear submarine K-27, was dumped in Stepogovo Fjord and contained spent nuclear fuel (SNF). Although the two K-27 submarine reactors were mothballed before dumping, concerns about the potential long term risks of contamination remain and plans to retrieve and decommission K-27 exist. In this article, human dose and environmental impact aseessments are presented for two possible future scenarios involving: (1) an ingress of water into a reactor in situ leading to a spontaneous chain reaction (SCR) and (2) an on-board fire when SNF is being removed at the mainland decommissiong site at Gremhika Bay on the Kola Peninsula. Assessments have been completed using conservative assumptions, focusing on possible effects to Norwegian territory. Atmospheric transport and deposition of radioactivity was modelled near field and regionally, using appropriate models, whilst human doses and environmental exposures were modelled using a standard IAEA approach and the ERICA tool, respectively. Results indicate that large areas of Norwegian territory could be affected by fallout from the Gremhika scenario, especially in the north, though at levels two orders of magnitude lower than those observed after the Chernobyl accident. Potential doses, primarily due to ground shine, to a critical group of personnel on-site at Stepogovo resulting from a SCR could require preventative measures based on ICRP recommendations (20-100 mSv). Doses to non-human biota in Norway for the Gremhika scenario would be negligible, typical of background dose rates for terrestrial organisms.

Vertical distribution of anthropogenic radionuclides in cores from contaminated floodplains of the Yenisey River.

The Mining and Chemical Industrial Combine, Zheleznogorsk (MCIC, previously known as Krasnoyarsk-26) on the River Yenisey has contaminated the surrounding environment with anthropogenic radionuclides as a result of discharges of radioactive wastes. The purpose of this study was to investigate the vertical distribution of anthropogenic contamination ((137)Cs and plutonium) within floodplain areas at different distances from the discharge point. Sites were chosen that display different characteristics with respect to periodic inundation with river water. Cs-137 activity concentrations were in the range 23-3770 Bq/kg (dry weight, d.w.); Pu-239,240 activity concentrations were in the range <0.01-14.2 Bq/kg (d.w.). Numerous sample cores exhibited sub-surface maxima which may be related to the historical discharges from the MCIC. Possible evidence indicating the deposition of earlier discharges at MCIC in deeper core layers was observed in the (238)Pu:(239,240)Pu activity ratio data: a Pu signal discernible from global fallout could be observed in numerous samples. Cs-137 and Pu-239,240 activity concentrations were correlated with the silt fraction (% by mass <63 microm) though no significant correlation was observed between (grain-size) normalised (137)Cs activity concentrations and distance downstream from the MCIC.

Norway's role in international collaboration towards rehabilitation of Andreeva Bay.

Andreeva Bay is one of the largest and most hazardous nuclear legacy sites in northwest Russia. The site is the location of large amounts of Spent Nuclear Fuel (SNF) and radioactive wastes and the risks associated with the site have precipitated an extensive international collaborative effort towards securing and rehabilitating the site. Given the location and proximity of the site, Norway has and continues to contribute in a number of ways towards this effort. Norway's activities in relation to rehabilitative efforts at Andreeva Bay are focused on both infrastructural and remediative initiatives as well as regulatory collaboration with Russia towards ensuring effective and safe operations during handling and removal of SNF and radioactive materials. This article describes Norway's role within international efforts in the context of the rehabilitation of Andreeva Bay and outlines previous activities and Norway's future direction with respect to the site.

Floating nuclear power plants: potential implications for radioactive pollution of the northern marine environment.

Recent media reports as to the development, construction and possible deployment of floating nuclear power plants in the northern regions has generated significant interest in the matter. This paper presents background to the concept of floating nuclear power plants, information as to possible designs and iterations and some aspects of potential concern with respect to safety and the potential for environmental or other impacts as a result of the development and use of such systems in the northern regions.

Will global warming affect soil-to-plant transfer of radionuclides?

Recent assessments of global climate/environmental change are reaching a consensus that global climate change is occurring but there is significant uncertainty over the likely magnitude of this change and its impacts. There is little doubt that all aspects of the natural environment will be impacted to some degree. Soil-to-plant transfer of radionuclides has long been a significant topic in radioecology, both for the protection of humans and the environment from the effects of ionising radiation. Even after five decades of research considerable uncertainty exists as to the interplay of key environmental processes in controlling soil-plant transfer. As many of these processes are, to a lesser or greater extent, climate-dependent, it can be argued that climate/environmental change will impact soil-to-plant transfer of radionuclides and subsequent transfers in specific environments. This discussion attempts to highlight the possible role of climatic and climate-dependent variables in soil-to-plant transfer processes within the overall predictions of climate/environmental change. The work is speculative, and intended to stimulate debate on a theme that radioecology has either ignored or avoided in recent years.

On-site radioactive soil contamination at the Andreeva Bay shore technical base, Northwest Russia.

The radioactive waste (RAW) storage site at Andreeva Bay in the Russian Northwest has experienced radioactive contamination both as a result of activities carried out at the site and due to incidents that have occurred there in the past such as accidental releases of radioactive materials. The site is an interesting case study for decommissioning due to the extremely large amounts of radioactivity present at the site and the conditions under which it is stored; very little has been previously published in the scientific literature about this site. This paper complements the paper describing dose rates at Andreeva Bay which is published in this issue of Journal of Environmental Radioactivity by the same authors. This study presents new data related to the activity concentrations of (137)Cs and (90)Sr in surface soils and measurements of alpha- and beta-particle fluxes taken at different areas around the site. Limited data on 60Co is also presented. The results of the study indicate that the main areas of site contamination are associated with the former spent nuclear fuel storage facility at Building 5, due to accidental discharges which began in 1982. Substantial contamination is also observed at the solid radioactive waste storage facilities, probably due to the ingress of water into these facilities. More than 240 samples were measured: maximum contamination levels were 1 x 10(6)Bq/kg (137)Cs (mean value 4.1 x 10(5)Bq/kg) and 4 x 10(6)Bq/kg (90)Sr (mean value 1.2 x1 0(5)Bq/kg). Localised patches of alpha and beta contamination were also observed throughout the site.

On-site gamma dose rates at the Andreeva Bay shore technical base, northwest Russia.

The spent nuclear fuel (SNF) and radioactive waste (RAW) storage facility at Andreeva Bay shore technical base (STB) is one of the largest and most hazardous nuclear legacy sites in northwest Russia. Originally commissioned in the 1960s the facility now stores large amounts of SNF and RAW associated with the Russian Northern Fleet of nuclear powered submarines. The objective of the present study was to map ambient gamma dose rates throughout the facility, in particular at a number of specific sites where SNF and RAW are stored. The data presented here are taken from a Norwegian-Russian collaboration enabling the first publication in the scientific literature of the complete survey of on-site dose rates. Results indicate that elevated gamma dose rates are found primarily at discrete sites within the facility; maximum dose rates of up to 1000 microSv/h close to the ground (0.1m) and up to 3000 microSv/h at 1m above ground were recorded, higher doses at the 1m height being indicative primarily of the presence of contaminated equipment as opposed to ground contamination. Highest dose rates were measured at sites located in the immediate vicinity of buildings used for storing SNF and sites associated with storage of solid and liquid radioactive wastes. Elevated dose rates were also observed near the former channel of a small brook that became heavily contaminated as a result of radioactive leaks from the SNF storage at Building 5 starting in 1982. Isolated patches of elevated dose rates were also observed throughout the STB. A second paper detailing the radioactive soil contamination at the site is published in this issue of Journal of Environmental Radioactivity.

Radionuclide contamination of sediment deposits in the Ob and Yenisey estuaries and areas of the Kara Sea.

The Ob and Yenisey rivers are major contributors to total riverine discharge to the Arctic Ocean. Several large nuclear facilities discharge into these rivers, which could affect actual and potential discharges of radionuclides to the Arctic region. This article presents new radionuclide concentration and grain-size data resulting from analyses of several sediment samples collected during research cruises in the Ob and Yenisey estuaries and adjacent areas during 2000 and 2001. Results indicate that discharges from the main nuclear facilities do not constitute a major contribution to the level of radioactive contamination in the marine areas studied, though Co-60 was detected at low concentrations in some sediment horizons. However, the aggregate contamination from different sources is not radioecologically significant in sediments within the study area, maximum Cs-137 levels being approximately 80 Bq kg(-1) dry weight.

Environmental, health and safety assessment of decommissioning radioisotope thermoelectric generators (RTGs) in northwest Russia.

This paper presents findings from public health and environmental assessment work that has been conducted as part of a joint Norwegian-Russian project to decommission radioisotope thermoelectric generators (RTG) in northwest Russia. RTGs utilise heat energy from radioactive isotopes, in this case 90Sr and its daughter nuclide 90Y, to generate electricity as a power source. Different accident scenarios based on the decommissioning process for RTGs are assessed in terms of possible radiation effects to humans and the environment. Doses to humans and biota under the worst-case scenario were lower than threshold limits given in ICRP and IAEA literature.

Pu and U atom ratios and concentration factors in reservoir 11 and Asanov Swamp, Mayak PA: an application of accelerator mass spectrometry.

Mayak Production Association, East Ural, Russia, was established to produce weapons-grade plutonium. Routine discharges and accidents at Mayak PA contaminated large areas, including the Techa River. The objectives of the present work were to study atom ratios for plutonium and, for the first time to our knowledge, uranium isotopes in water, soil, grass, and aquatic biota samples from Reservoir 11 and the Asanov Swamp, downstream from Mayak PA. Atom ratios (240Pu/239Pu, 236U/235U, 235U/238U) were determined using accelerator mass spectrometry to confirm radionuclide source characteristics and calculate activities and concentration factors for the studied samples. The lowest 240Pu/239Pu atom ratios were consistently found in Asanov Swamp samples (approximately 0.019), indicating a major contribution from early discharges of weapons-grade Pu. 240Pu/239Pu atom ratios in Reservoir 11 were higher, indicating influence from more recent civil reprocessing. The presence of 236U is usually indicative of fuel irradiation; 236U/235U ratios increase from weapons to civil sources. Our new data show that Asanov samples had lower 236U/ 235U ratios than Reservoir 11 samples (0.0005-0.0045 for Asanov compared with 0.0074-0.0153 for Reservoir 11) in agreement with Pu results. Pu and U concentration factors calculated for vegetation and biota samples at Mayak were comparable with corresponding values found in the literature.

Remobilisation of 109Cd, 65Zn and 54Mn from freshwater-labelled river sediments when mixed with seawater.

A major fraction of trace metals transported by rivers is associated with sediments, especially during flooding, when erosion and resuspension increase sediment loads. Upon contact with seawater in estuaries, changes in ionic strength and pH may remobilise trace metals from sediment surfaces into more bioavailable forms. The objective of the present work was to investigate time-dependent interactions between trace metals and freshwater sediments and their potential remobilisation upon contact with seawater. Two river sediments (one organic and one inorganic) were labelled with 109Cd2+, 65Zn2+ and 54Mn2+ radioactive tracers for periods up to 6 months. Sorption of tracers occurred rapidly (> or = 80% sorption, < 1 h), followed by a slower approach to pseudoequilibrium. Kd(6 months) were estimated as 460, 480 and 2200 ml/g (inorganic sediment) compared to 5300, 4000 and 1200 ml/g (organic sediment) for 109Cd, 65Zn and 54Mn, respectively. Remobilisation of tracers from labelled sediments was studied using sequential extractions. Artificial seawater extracts simulated an estuarine environment. Subsequent extractions provided information about more strongly sorbed tracer fractions within sediments. Remobilisation of 109Cd by seawater was significant (> 65%) and least affected by sediment type or freshwater labelling time. Redistribution of Cd to strongly bound phases was minimal (4% and 1% of 109Cd in strongly oxidisable fractions). Seawater remobilisation of 65Zn was significantly greater from the organic sediment (54%) compared to the inorganic sediment (8%), where a large fraction of 65Zn (14%) became irreversibly bound. Similarly, more 54Mn was remobilised by seawater from the organic sediment than the inorganic sediment (66% and 3% remobilised, respectively), i.e., 54Mn became more strongly bound in the inorganic sediment. A simple three-box model, based on first-order differential equations, was used to describe the interaction between tracers in spiked freshwater and two operationally defined sediment fractions ("seawater exchangeable" and "seawater unexchangeable") up to 6 months of freshwater labelling. Model simulations were fitted to experiment data and apparent rate constants were calculated using numerical optimisation methods. Sorption ratios from modelling data (i.e., k1/k2) were greater for organic compared to inorganic sediments, while fixation ratios were higher in inorganic sediments. In conclusion, trace metals can be remobilised from sediments on contact with seawater in estuaries. High organic content in sediments increased initial sorption of tracers but inhibited redistribution to more strongly bound fractions over time, resulting in greater remobilisation of tracers when in contact with seawater.