Radiation Protection Dosimetry (2015), Vol. 164, No. 1–2, pp. 103 –107 Advance Access publication 27 November 2014


A BIOSPHERE ASSESSMENT OF HIGH-LEVEL RADIOACTIVE WASTE DISPOSAL IN SWEDEN Ulrik Kautsky1, Tobias Lindborg1 and Jack Valentin2, * 1 Swedish Nuclear Fuel and Waste Management Co. (SKB), Box 250, Stockholm SE-101 24, Sweden 2 ¨ regrundsgatan 15, Stockholm SE-115 59, Sweden Jack Valentin Radiological Protection, O *Corresponding author: [email protected]

INTRODUCTION A repository site, Forsmark, has been selected for the disposal of Swedish spent nuclear fuel. Licence applications to build the repository have been lodged by SKB, the Swedish Nuclear Fuel and Waste Management Company, which is tasked with safe managing of all manner of Swedish radioactive waste. The applications are underpinned by a vast body of research reports; the complete application exceeds 10 000 pages. The research reports are supplemented by holistic overviews. SKB has previously organised such reviews on, e.g. hydrogeology, geochemistry and ecosystem modelling. Here, after describing very briefly the technical system of disposal and the formal licensing process, the authors summarise a recent SKB review of the effects on humans and ecosystems of a potential release from the planned repository, provide some information on regulatory reactions so far and discuss the possibility of using the same approach in other environmental contexts than radioactive waste.

THE KBS-3 DISPOSAL SYSTEM The well-known KBS-3 disposal system comprises copper canisters with a cast iron inset containing spent nuclear fuel, surrounded by compacted bentonite clay and deposited at 500 m depth in groundwater-saturated granitic rock(1). The system comprises a series of barriers as shown in Figure 1. The integrity or otherwise of these barriers and the factors that might influence them are not part of the biosphere assessment reviewed here but are discussed in, e.g. the 2013 research programme(2) of SKB.

Currently, Swedish spent nuclear fuel is held at the interim storage installation, CLAB, in Oskarshamn in south-eastern Sweden (next to the Oskarshamn nuclear power plant). SKB has selected Forsmark, further north up the east coast of Sweden, as the site for the final repository for spent nuclear fuel. Forsmark also has a nuclear power plant and a final repository for short-lived low- and intermediate-level radioactive waste (SFR). The intention, given the necessary licences, is to build a repository comprising some 70 km of tunnels for deposition of canisters. The construction, operation and decommissioning will take some 60–70 y. It is also planned to extend CLAB with an encapsulation plant, so that completed canisters can be transported from Oskarshamn to Forsmark for deposition, using the existing system for sea transport of spent fuel. THE LICENSING PROCESS In order to carry out these plans, SKB has applied for licences to (a) continue to operate the interim storage at CLAB, (b) build an adjacent encapsulation plant and then operate interim storage and encapsulation as a single integrated installation and (c) build and operate a final repository at Forsmark. The applications, with an Environmental Impact Assessment, are being evaluated by (a) the Swedish Radiation Safety Authority, SSM, under the Nuclear Activities Act and (b) the Land and Environment Court under the Environmental Code. Both agencies are circulating the applications widely for comments. Having taken account of the opinions received, they will submit their comments to the Government. The two municipalities concerned will have a final

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Licence applications to build a repository for the disposal of Swedish spent nuclear fuel have been lodged, underpinned by myriad reports and several broader reviews. This paper sketches out the technical and administrative aspects and highlights a recent review of the biosphere effects of a potential release from the repository. A comprehensive database and an understanding of major fluxes and pools of water and organic matter in the landscape let one envisage the future by looking at older parts of the site. Thus, today’s biosphere is used as a natural analogue of possible future landscapes. It is concluded that the planned repository can meet the safety criteria and will have no detectable radiological impact on plants and animals. This paper also briefly describes biosphere work undertaken after the review. The multidisciplinary approach used is relevant in a much wider context and may prove beneficial across many environmental contexts.


The KBS-3 disposal system and its barriers.

opportunity at this stage to accept or reject the final repository and the encapsulation plant. Assuming that they both accept and that neither the Land and Environment Court nor SSM have voiced serious concerns, the Government will, presumably, issue the requested licences. The process then reverts again to the Court for further comments and to SSM for stipulation of licence conditions. Once these are met, the actual building and operation can begin.

THE BIOSPHERE REVIEW Any licence application for a spent nuclear fuel repository will rest on a safety analysis. The first stage of such an analysis reviews the technical safety and the reliability of the barriers. A biosphere review is the second stage, assuming a barrier failure and a release of radioactive material from a canister. It analyses the transport of radioactive material to and through the biosphere and the impact on man, animals and plants. The major parts of the research and analysis were performed within the SKB project SR-Site(3), a Safety Report for the assessment of a repository for spent nuclear fuel at Forsmark. The results come from a decade of multidisciplinary research aiming to understand how radionuclides from a potential release from the repository might migrate and cause radiation exposures to man and the environment in the far future. The SR-Site Report (3) and the many more specialised supporting documents are detailed, technical and not easily digested even for scientists, let alone for laymen. To provide a summary with the rigour of a scientific journal, yet reasonably accessible to

interested non-specialists, the authors organised a Special Issue of AMBIO (4) with a summary report (5) and papers covering the major components of the biosphere analysis. Objectives and methodology A site investigating programme generated a large database covering marine, limnetic and terrestrial ecosystems as well as information on, e.g. element sorption in soils and transfers to organisms. The high spatial and temporal resolution of the database together with historical data provides an understanding of the landscape changes. An ecosystem approach has been used to understand the major fluxes and pools of water and organic matter in the landscape. Major review components The SR-Site project was very comprehensive, and the AMBIO presentation of the biosphere review did not cover every detail of the safety assessment. It did, however, provide a coherent and adequate description of the assessment by highlighting major components. Here, the authors present the biosphere review of the ‘base case’ of SR-Site. External conditions during the first 120 000-y glacial cycle are assumed to be similar to those of the most recent (Weichselian) cycle and seven repetitions of that cycle cover the assessment period of 1 million years. With this time perspective, there is a (small) risk of canister failures due to enhanced corrosion following buffer erosion. There is an even smaller risk contribution from canister failures due to earthquakes. Based on these canister


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Figure 1.


failure scenarios, a release of radionuclides to the biosphere is possible, primarily through water-bearing fissures. The complicated assessment of a ‘source term’ of radionuclide releases due to such failures and the selection of radionuclides to include in subsequent dose calculations are described in the SR-Site report (3). Here, the authors discuss what happens when radionuclides reach biosphere objects (the sea, lakes, wetlands, etc.) and when these objects develop and change with time.

Discharge areas By solute transport modelling(9), discharge areas for groundwater, potentially carrying radionuclides from a repository to the surface, were located and described. The results showed that topography largely determines the discharge locations. Present and future lake and wetland objects are central for radionuclide transport and dose calculations. The identification of discharge areas was robust in the sense that the discharge pattern in the landscape did not change when more detailed modelling was used.

Landscape development

Climate change Describing the variation in climate and related processes such as formation of ice sheets, growth of permafrost and changes in sea level, it was shown(7) that the climate scenarios range from cases with highend global warming for the coming 100 000 y, through to cases with maximum deep permafrost, to cases with large ice sheets during full glacial conditions. The safety assessment for the planned repository extends to 1 million years, over which period about eight glacial– interglacial cycles are expected.

Element transport Conceptual and numerical reactive transport models were developed(8) in order to assess the retention capacity of Quaternary till and clay deposits for selected radionuclides in the event of a release from the repository. The elements considered were C, Cl, Cs, I, Mo, Nb, Ni, Ra, Se, Sr, Tc, Th and U although other elements and decay chains were also assessed. The nuclides that would be most significantly retained were Th, Ni and Cs, mainly through sorption onto clays, followed by U, C, Sr and Ra, trapped by sorption and/or incorporation into mineral phases.

Hydrology A hydrological analysis(10) showed that at least until year 10 000 AD, the hydrological system will be affected by landscape succession associated with shoreline displacement and changes in vegetation, regolith (soil and sediment) stratigraphy and climate. Shoreline displacement has a strong effect on local hydrology (e.g. groundwater flow) in areas that change from sea to land. Climate variables were particularly important for main hydrological features such as water balances and transport routes. Soil and sediment The mobility of various elements was studied(11) in arable and wetland soils in the Forsmark region, and solid/liquid partition coefficients (KD) were obtained. With this information, radionuclide accumulation and mobility could be rescaled within the future landscape mosaic. Marine system Several modelling studies of coastal areas were performed, covering water exchange on a time span from 6500 BC to 9000 AD(12), particle transport as a function of coastal geometry(13) and retention and hydrodynamics combined with an understanding of accumulation processes in ecosystems(14). By combining the measurable, predictable geometry with process understanding of hydrodynamics, particle retention and ecosystem accumulation, an understanding of the coastal area was achieved. Land use Ingestion is expected to be the major exposure pathway. After characterising the group of individuals with the highest exposures(15), it was possible to calculate intake rates based on land-use scenarios drawn from self-sustained communities spanning prehistoric times to an industrial-age agrarian culture.


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Based on current and historical data, climate change, shoreline displacement and accumulation/erosion processes were found to be the main drivers of landscape development (6). Site-specific information was combined with data from the Scandinavian region to build models of site development. The process models were combined to describe a whole interglacial period. It turned out that the future can be envisaged by looking at older parts of the site, as almost all landscape development stages can be found within the investigation area. Thus, today’s biosphere could function as a natural analogue of possible components of the future landscape.


It is argued that the derived intake rates may serve as credible bounding cases for projected doses. RESULTS

Dose calculations Handling releases in the far future is a challenge. Such releases would occur over long periods during which environmental conditions will be continuously varying. ‘Landscape dose conversion factors’ can be devised, showing how the dose, normalised to activity released, varies over long periods (many thousand years). Using this approach, it is demonstrated(16) that annual effective doses due to releases from the planned repository are expected to be at most 1 mSv, taking account of doses from food intake (the major exposure pathway) of representative future persons. The regulatory acceptance criterion(17) of an annual risk of harm less than 1026 is met; it corresponds to an annual effective dose of 14 mSv, i.e. the maximum repository dose (expected 106 y after closure) is an order of magnitude below the regulatory criterion.

BIOSPHERE WORK AFTER THE REVIEW Supplementary information requested by regulator After analysis of the biosphere review regarding radiological impacts on animals and plants, SSM requested more data on additional radionuclides and total dose rates, some particular species, different climates, pulse rather than continuous release of radionuclides and inclusion of bird eggs in the study. SKB has provided the information requested(21). However, the dose rates to biota are still at least two orders of magnitude below any criteria, so the earlier conclusion that there will be no discernible impact on biota remains unchanged. Another request from the regulator was to motivate the omission of exposure of peat burning. This had not been included since the additional dose from this pathway was regarded as very low. SKB has revisited and extended the earlier assessment with burning of any biofuel (e.g. peat, wood); the conclusion, however, remains that inclusion is not warranted. It was also concluded that peat burning is inefficient and unsustainable in an area of high forest productivity. Associated biosphere work SKB has made a new assessment (2) of SFR, the repository for short-lived low- and intermediate-level waste in Forsmark, in support of an application for an extension of that repository. The new assessment includes a study of climate impacts for the next 100 000 y; a more detailed handling of 14C in the biosphere, a subdivision of the landscape and obtaining site-specific data on KD values and concentration factors of organisms. The risk is estimated in coupled calculations with releases in the repository and transport in the rock and biosphere, instead of using a constant maximum dose conversion factor. The more detailed and realistic assessment reduces the estimated risk to man and the environment. SKB has also initiated a 4D modelling of repository to surface transport (2). The tool includes leaching processes in the repository, hydrological transport in a chemical environment varying in time and space and a spatially complex surface environment with heterogeneous redox conditions. Instead of using a


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The review shows ways of understanding and characterising the future and gives examples of how to handle uncertainty. The future is presented as a derivation from the present conditions at the site, rather than as a collection of scenarios. The examples are not predictions but reasonable speculations of alternative futures for calculating radiation doses and presenting the future risk to humans and environment of the proposed installation. Thus, the current site information is used to develop descriptions of possible future development of the repository site, Forsmark. One main driver for site development is climate change. As a main reference case for future climate in SR-Site, the last glacial cycle is used as an analogue. The reference glacial cycle starts when the Weichselian ice retreated from Forsmark around year 8800 BC and continues until circa 120 000 AD when the cycle is completed. During the reference glacial cycle, a number of climate-driven conditions appear, from submerged conditions directly after the ice sheet has withdrawn to recurrent temperate, periglacial and glacial domains. The different environmental conditions and the transitions between them are described in a landscape development model, which uses input from a range of discipline-specific models, e.g. hydrology, chemistry, sedimentation, ecosystems, shoreline displacement and climate. The final output is a model of the site development and the associated properties under different future conditions, describing Forsmark as it develops during a glacial cycle.

Radiation dose rates to a broad spectrum of relevant organisms were calculated(18). All calculated dose rates for biota were below the default screening dose-rate value of 10 mGy h21 used in the ERICA Tool(19) and also below the lowest band of ‘derived consideration levels’ given by the International Commission on Radiological Protection(20). Thus, no radiological impact on plants and animals from the repository can be detected.


constant KD, the sorption varies over time, based on chemical processes. This tool will be applied for the coming assessment of the repository of long-lived operational and decommissioning waste (SFL), where some dominant radionuclides (e.g. Mo) are sensitive to the biogeochemical environment. CONCLUSION

REFERENCES 1. SKBF/KBS. Final storage of spent nuclear fuel—KBS3, summary. Svensk Ka¨rnbra¨nslefo¨rso¨rjning AB (1983). 2. SKB. RD&D Programme 2013. Programme for research, development and demonstration of methods for the management and disposal of nuclear waste. Svensk Ka¨rnbra¨nslehantering AB, SKB TR-13-18 (2013). 3. SKB. Long-term safety for the final repository for spent nuclear fuel at Forsmark. Main report of the SR-Site project. Svensk Ka¨rnbra¨nslehantering AB, SKB TR-1101 (2011). 4. Valentin, J., Kautsky, U. and Lindborg, T. (Eds). Special issue: humans and ecosystems over the coming millennia: a biosphere assessment of radioactive waste disposal in Sweden. AMBIO 42 no. 4 (2013). 5. Kautsky, U., Lindborg, T. and Valentin, J. Humans and ecosystems over the coming millennia: overview of a biosphere assessment of radioactive waste disposal in Sweden. AMBIO 42, 383 –392 (2013). 6. Lindborg, T., Brydsten, L., Sohlenius, G., Stro¨mgren, M., Andersson, E. and Lo¨fgren, A. Landscape development during a glacial cycle: modeling ecosystems from the past into the future. AMBIO 42, 402–413 (2013). 7. Na¨slund, J.-O., Brandefelt, J. and Claesson Liljedahl, L. Climate considerations in long-term safety assessments for nuclear waste repositories. AMBIO 42, 393–401 (2013). ` ., Arcos, D., Grandia, F., Molinero, J., Duro, L. 8. Pique´, A and Berglund, S. Conceptual and numerical modeling of radionuclide transport and retention in near-surface systems. AMBIO 42, 476–487 (2013).


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In a new biosphere assessment approach, a systematic scientific methodology utilises the spatial and temporal dynamics of the site today as an analogue for future conditions. An understanding of the site and the possible range of future conditions can be inferred from a few measureable variables. Thus, from robust measurements, simple assumptions and modelling, specific results can be obtained defining the future potential areas and populations that will be exposed to the highest risks. This multidisciplinary approach is relevant in a much wider context than radioactive waste and may prove beneficial across a wide range of environmental contexts.

9. Berglund, S., Bosson, E., Selroos, J.-O. and Sassner, M. Identification and characterization of potential discharge areas for radionuclide transport by groundwater from a nuclear waste repository in Sweden. AMBIO 42, 435–446 (2013). 10. Berglund, S., Bosson, E. and Sassner, M. From site data to safety assessment: analysis of present and future hydrological conditions at a coastal site in Sweden. AMBIO 42, 425–434 (2013). 11. Sohlenius, G., Saetre, P., Norde´n, S., Grolander, S. and Sheppard, S. Inferences about radionuclide mobility in soils based on the solid/liquid partition coefficients and soil properties. AMBIO 42, 414 –424 (2013). 12. Eriksson, C. and Engqvist, A. Water exchange on a geological timescale—examples from two coastal sites in the Baltic Sea. AMBIO 42, 447 –454 (2013). 13. Corell, H. and Do¨o¨s, K. Difference in particle transport between two coastal areas in the Baltic Sea investigated with high resolution trajectory modeling. AMBIO 42, 455–463 (2013). 14. Erichsen, A. C., Konovalenko, L., Møhlenberg, F., Closter, R. M., Bradshaw, C., Aquilonius, K. and Kautsky, U. Radionuclide transport and uptake in coastal aquatic ecosystems: a comparison of a 3D dynamic model and a compartment model. AMBIO 42, 464–475 (2013). 15. Saetre, P., Valentin, J., Lagera˚s, P., Avila, R. and Kautsky, U. Land use and food intake of future inhabitants: outlining a representative individual of the most exposed group for dose assessment. AMBIO 42, 488– 496 (2013). ˚ strand, P.-G. 16. Avila, R., Kautsky, U., Ekstro¨m, P.-A., A and Saetre, P. Model of the long-term transport and accumulation of radionuclides in future landscapes. AMBIO 42, 497–505 (2013). 17. Swedish Radiation Safety Authority. Stra˚lsa¨kerhetsmyndighetens fo¨reskrifter och allma¨nna ra˚d om skydd av ma¨nniskors ha¨lsa och miljo¨n vid slutligt omha¨ndertagande av anva¨nt ka¨rnbra¨nsle och ka¨rnavfall. Stra˚lsa¨kerhetsmyndighetens fo¨rfattnings-samling, SSM FS (Code of Statutes) 2008 No. 37; English version see http://www.stralsakerhetsmyndigheten.se/Global/ Publikationer/Forfattning/Engelska/SSMFS-2008-37E .pdf (2008). 18. Torudd, J. and Saetre, P. Assessment of long-term radiological effects on plants and animals from a deep geological repository: No discernible impact detected. AMBIO 42, 506–516 (2013). 19. Brown, J. E., Alfonso, B., Avila, R., Beresford, N. A., Copplestone, D., Pro¨hl, G. and Ulanovsky, A. The ERICA tool. J. Environ. Radioact. 99, 1371–1383 (2008). 20. ICRP. Environmental protection: The concept and use of reference animals and plants. ICRP Publication 108. Ann. ICRP 38 No. 4– 6 (2008). 21. Jaeschke, B., Smith, K., Norde´n, S. and Alfonso, B. Assessment of risk to non-human biota from a repository for the disposal of spent nuclear fuel at Forsmark. Supplementary information. Svensk Ka¨rnbra¨nslehantering AB, SKB TR-13-23 (2013).

A biosphere assessment of high-level radioactive waste disposal in Sweden.

Licence applications to build a repository for the disposal of Swedish spent nuclear fuel have been lodged, underpinned by myriad reports and several ...
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