Biosphere analyses for the safety assessment SR-Site – synthesis and summary of results

Technical Report

TR-10-09

Biosphere analyses for the safetyassessment SR-Site – synthesis
and summary of results
Svensk Kärnbränslehantering AB

December 2010

Svensk Kärnbränslehantering AB

Box 250, SE-101 24 Stockholm
Phone +46 8 459 84 00

TR-10-09

CM Gruppen AB, Bromma, 2011

Swedish Nuclear Fueland Waste Management Co

ISSN 1404-0344
Tänd ett lager:
SKB TR-10-09
P, R eller TR.

Biosphere analyses for the safetyassessment SR-Site – synthesis
and summary of results
Svensk Kärnbränslehantering AB

December 2010

Keywords: SKBdoc 1269178, Assessment context, Biosphere object, Discharge areas,
Features, events and processes (FEP), Interaction matrix, Landscape development,
Landscape dose conversion factors (LDF), Non-human biota (NHB), Radionuclide transport, Sensitivity analysis, Site description, Surface ecosystems, Uncertainty analysis.
A pdf version of this document can be downloaded from www.skb.se.

Preface
This report presents a synthesis of a number of biosphere analyses undertaken in an assessment oflong-term safety of a KBS-3 repository for spent nuclear fuel. The report forms part of the safetyassessment SR-Site, which will support the licence application for a final repository in Sweden.
The report was compiled by Peter Saetre, SKB. A number of additional authors have contributed tovarious sections of the report as listed at the end of Chapter 1.
Stockholm, February 2011
Allan Hedin
Project leader SR-Site

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Summary
The Swedish Nuclear Fuel and Waste Management Co, SKB, launched the project SR-Site to conduct a safety assessment of the planned repository for spent nuclear fuel in Forsmark after closure.
The assessment focuses on the performance of the repository, the transport of potentially released
radionuclides from the repository, through the geosphere, up to and within the biosphere, and theconsequences for humans and the environment in the biosphere. The purpose is to show whether
humans and the environment are sufficiently protected from harmful effects of ionising radiation.
This report summarises nearly 20 biosphere reports and gives a synthesis of the work performed
within the SR-Site Biosphere project, i.e. the biosphere part of SR-Site. SR-Site Biosphere provides
the main project with dose conversion factors (LDFs), given a unit release rate, for calculation ofhuman doses under different release scenarios, and assesses if a potential release from the repository
would have detrimental effects on the environment. The intention of this report is to give sufficientdetails for an overview of methods, results and major conclusions, with references to the biospherereports where methods, data and results are presented and discussed in detail.
The philosophy of the biosphere assessment was to make estimations of the radiological risk forhumans and the environment as realistic as possible, based on the knowledge of present-day conditions at Forsmark and the past and expected future development of the site. This was achieved byusing the best available knowledge, understanding and data from extensive site investigations fromtwo sites. When sufficient information was not available, uncertainties were handled cautiously.
A systematic identification and evaluation of features and processes that affect transport andaccumulation of radionuclides at the site was conducted, and the results were summarised in aninteraction matrix. Data and understanding from the site investigation was an integral part of thiswork, the interaction matrix underpinned the development of the radionuclide model used in thebiosphere assessment.
Understanding of the marine, lake and river and terrestrial ecosystems at the site was summarized in aconceptual model, and relevant features and process have been characterized to capture site specificparameter values. Detailed investigations of the structure and history of the regolith at the site andsimulations of regolith dynamics were used to describe the present day state at Forsmark and the
expected development of the site. The hydrodynamics in the coastal areas was characterized in thefield and combined with the bathymetry of the future landscape to forecast the turnover of water infuture coastal basins. The surface and near surface hydrology was described at the site and dynamic
models were applied on the future landscape to predict vertical and horizontal transport under different climatic conditions. Historical and present human settlement at the site was used to characterize
the utilisation of natural resources in a landscape perspective, and the productivity of food items
was described and evaluated. The collection and analysis of multi-elemental chemistry data fromdifferent environmental media and a wide array of organisms were used to the estimate a uniqueparameter set describing sorption and biological uptake at the site.
A continuous and iterative effort to improve the site characterisation and the site modelling during
the investigations resulted in a refined collection of data, in parallel with detailed understanding of
the processes that affects transport and accumulation in the surface ecosystems. This interdisciplinary and synchronously large scale collection and analysis of site data makes Forsmark one of themost extensively investigated sites used in risk or environmental assessments.
By combining predicted discharge of deep groundwater from the repository and landscape geo­
metries, the areas most likely to be affected by a potential release of radionuclides were identified
and outlined, i.e. biosphere objects. The properties and temporal development of these discharge
areas were described, developing from a coastal sea basin to a terrestrial ecosystem. The identified
biosphere objects represent a considerable variation in size, timing of succession and object-specificproperties.

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An ecosystem-based approach was used to dynamically model transport and accumulation of radionuclides in biosphere objects. The simulations with the model covered a 70,000 year ice free period
between two glaciations. The radionuclide model used in SR-Site has been improved in several
important ways since previous safety assessments conducted by SKB. For example, the aquaticand terrestrial ecosystems are handled in the same model, which gives a continuous transition fromthe sea stage to the lake and terrestrial stages. Transport and accumulation in till (lower regolith)
is represented in the model. The uptake by plants is included in the mass-balance, and it is related
to biomass growth. Moreover, parameter values including hydrological flows, sedimentation andresuspension rates, biomass growth rates, gas exchange rates, as well as element specific distribution
coefficients and concentration rations, were as far as possible based on site data.
One endpoint from the simulations with the radionuclide model was the landscape dose conversion
factors (LDFs). The LDF represents the mean annual effective dose over lifetime for an individualliving in the most contaminated area, assuming a constant unit release rate (1Bq/y). In the safetyassessment, the maximum LDF for each nuclide have been selected from the biosphere object at thetime yielding the highest unit release dose, and consequently LDFs from different nuclides does notnecessarily match the same group of exposed individuals with respect to point in time or location in
the landscape. In the SR-Site main report, the resulting dose is presented when the maximum LDF is
multiplied by a release.
The potential effect of a radionuclide release on non-human biota in Forsmark is also assessed. For
this analysis maximum release under the central corrosion case was multiplied with the maximum environmental concentrations (per unit release) from the radionuclide model. The resulting environmental
activity concentrations were used to calculate dose rates for representative species in Forsmark with the
ERICA tool. Calculated dose rates were far below the screening no-effect dose rate of 10 µGy h–1 for
all investigated organisms, demonstrating that a potential release from the repository is highly unlikely
to cause detrimental effects on the survival and reproduction of organisms. Thus, from this assessment
it is concluded that neither negative effects of the repository on biodiversity, nor sustainable use ofnatural resources in the Forsmark area are of concern.
In the final chapter the effects of uncertainties on the LDF that are used to calculate the final risk are
examined. The analysis showed that the handling of system, model and parameter uncertainties isbalanced, and that the effects of quantified uncertainties are limited. Consequently, identified uncertainties are not expected to have a significant effect on the assessment endpoint, and it is concluded
that the maximum LDFs used in SR-Site are robust estimates for a representative individual of themost exposed group, reflecting process understanding and the best available description of the site.

6

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Contents
1

Introduction

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2
2.1

This report
Report hierarchy
2.1.1 Process understanding
2.1.2 Description of the site and its development
2.1.3 Identification and characterization of discharge areas
2.1.4 Radionuclide modelling
Overview of contents

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Assessment context
Assessment purpose
Preconditions for the SR-Site safety assessment
3.2.1 Repository system
3.2.2 Site context
3.2.3 Release scenarios and source terms
Regulatory requirements on post closure safety
3.3.1 Time frames
3.3.2 Risk criteria for protection of human health3.3.3 Most exposed group
3.3.4 Effects on the environment
Relationship to international experience
3.4.1 Background to international cooperation in biosphere assessments
3.4.2 Biosphere analysis and dose assessments in other countries
3.4.3 Current international projects and related research
3.4.4 Application of the BIOMASS methodology in SR-Site
Conclusions from earlier SKB work
3.5.1 KBS-3
3.5.2 SR-97
3.5.3 SAFE
3.5.4 SR-Can interim assessment
3.5.5 SR-Can
Assessment philosophy

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Biosphere features, processes and pathways
Evaluation of important biosphere processes
4.1.1 Identification of processes for transport and accumulation ofradionuclides in the biosphere4.1.2 Major components and processes identified in the biosphereassessment of SR-Site
Exposure pathways

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Site description – present-day conditions at Forsmark
Abiotic characteristics
5.1.1 Topography
5.1.2 Regolith
5.1.3 Climate
5.1.4 Surface hydrology
5.1.5 Coastal oceanography
5.1.6 Chemistry
Ecosystems
5.2.1 Terrestrial ecosystems
5.2.2 Aquatic ecosystems
5.2.3 Human utilization of natural resources

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Site development
Main factors affecting site development

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2.2
3
3.1
3.2

3.3

3.4

3.5

3.6
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4.1

4.2
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5.1

5.2

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6.1

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6.2

6.3

6.4
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7.1
7.2

7.3

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8.1
8.2
8.3

8.4

8.5
8.6

8.7

8

Long-term site development
6.2.1 Climate and climate-related processes
6.2.2 Topography
6.2.3 Regolith
6.2.4 Surface hydrology
6.2.5 Coastal oceanography
6.2.6 Chemistry
6.2.7 Ecosystems
6.2.8 Human utilisation of natural resources
Site development during the reference glacial cycle
6.3.1 Site development during the initial 1,000 years after repository
closure6.3.2 Site development until the end of the initial period of a temperate
climate domain
6.3.3 Site development during the remaining part of the reference
glacial cycle
Site development according to the SR-Site global warming climate case
6.4.1 Ecosystems in a climate characterised by global warming

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Landscape model for radionuclide assessment
Discharge points
7.1.1 Modelling of deep groundwater discharge
7.1.2 Description of delivered discharge points
Near-surface flow and transport
7.2.1 Flow model results for different climate conditions
7.2.2 Near-surface flow paths
7.2.3 Transport by advection and dispersion
7.2.4 Radionuclide retention and reactive transport
Biosphere objects and landscape modelling
7.3.1 Identification of biosphere objects
7.3.2 Geometric features in the landscape
7.3.3 Temporal development of biosphere objects
7.3.4 Biosphere objects in the landscape
7.3.5 Parameterisation of biosphere objects
7.3.6 The landscape model during the reference glacial cycle

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The radionuclide model for the biosphere
Source terms
Future ecosystems
The most exposed group
8.3.1 Production and consumption of food and size of the most
exposed group
8.3.2 Land use on artificially drained wetlands
8.3.3 Water use
Modelling transport and accumulation of radionuclides in biosphere objects
8.4.1 Radionuclide fluxes
8.4.2 The temporal development of biosphere objects
8.4.3 Model represention of arable land
8.4.4 Modelling radionuclide flux between biosphere objects
8.4.5 Model represention of a well drilled through bedrock
8.4.6 The mathematical representation
Estimating activity concentrations
Assessment of human exposure
8.6.1 Exposures via inhalation and external irradiation
8.6.2 Exposures from consumption of contaminated water
8.6.3 Exposure from food consumption
Landscape dose conversion factors
8.7.1 LDF and modified LDF for pulse release
8.7.2 LDF values for different climatic conditions

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8.8
8.9

Software implementation
Quality assurance
8.9.1 Version handling and tracking systems
8.9.2 Handling of primary and generic data
8.9.3 Handling of parameters to the radionuclide model
8.9.4 Handling of results

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9.1

Data for assessment
Methods for selecting parameter values and probability density functions
9.1.1 Principles and uncertainties in parameterisation
9.1.2 Estimating concentration ratios from site and literature data
Description of model parameters9.2.1 Nuclide specific parameters9.2.2 Landscape geometries
9.2.3 Regolith
9.2.4 Ecosystem properties
9.2.5 Surface hydrology and water exchange
9.2.6 Distribution coefficients and diffusivity
9.2.7 Concentration ratios, retention and release
9.2.8 Human characteristics and dose coefficientsParameterisation at different climate stages
9.3.1 Periglacial parameterisation for supporting calculation

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9.2

9.3

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The landscape dose conversion factors (LDF)
113
10.1 Resulting LDFs
113
10.1.1 Comparison with results from earlier studies
115
10.2 Variation of LDFs in time and between biosphere objects
116
10.3 Calculations for pulse release near future scenarios and illustrations of barrier
functions117
10.3.1 Modified LDF for pulse release118
10.3.2 Early canister failure due to shear load
118
10.3.3 Residual scenarios to illustrate barrier functions
119
10.4 Natural concentrations of radionuclides in surface ecosystems
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11
Assessment of impact on non-human biota
11.1 Background11.2 Methodology
11.2.1 Radionuclides considered in the assessments
11.2.2 Organisms considered in the assessments
11.2.3 No-effect dose rate
11.2.4 Dose assessments using the ERICA tool
11.2.5 Representation of organisms
11.2.6 Activity concentrations in biota
11.2.7 Dosimetry
11.2.8 Activity concentrations in environmental media
11.3 Resulting doses to non-human biota
11.4 Discussion

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The effect of uncertainties on the landscape dose conversion factors
12.1 Background12.2 System uncertainties
12.2.1 Development of the biosphere12.2.2 Use of natural resources by future human inhabitants
Consumption of contaminated drinking water
12.3 Model uncertainties
12.3.1 Discretisation
12.3.2 Vertical transport
12.4 Parameter uncertainties and sensitivity analysis
12.4.1 Uncertainty analysis
12.4.2 Sensitivity analysis

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12.5 Overall uncertainty
12.6 Feedback for future Site investigations and the biosphere RD&D program

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151

References

Appendix 1

Forsmark area

159

Appendix 2

Glossary of terms and acronyms used in the SR-Site biosphereassessment

161

Appendix 3

Parameters for calculations of environmental concentrations

165

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TR-10-09

1

Introduction

Radioactive waste and spent nuclear fuel from Swedish nuclear power plants are managed by the
Swedish Nuclear Fuel and Waste Management Co, SKB. Both waste and spent fuel are planned to
be placed in a geological repository. According to KBS-3, copper canisters with a cast iron insert
containing spent fuel are to be enclosed by bentonite clay and deposited at approximately 500 m depth
in granitic bedrock. Approximately 12,000 tonnes of spent nuclear fuel is forecasted to arise from theSwedish nuclear power programme, corresponding to roughly 6,000 canisters in a KBS-3 repository.
Between 2002 and 2008, SKB performed site investigations with the intention on finding a suitablelocation for a repository. Investigations were focused on two different sites along the eastern coast ofsouthern Sweden; Forsmark in the municipality of Östhammar and Laxemar-Simpevarp in the municipality of Oskarshamn. Data from the site investigations have been used to produce comprehensive,
multi-disciplinary site descriptions for each of the sites. The resulting site descriptions were reportedin /­SKB 2008/ (Forsmark) and /­SKB 2009/ (Laxemar-Simpevarp). Based on available knowledge
from the site descriptions and from preliminary safety assessments of the planned repository, SKB
decided in June 2009 to put forward Forsmark as suggested site for the repository. The location ofForsmark is shown in Figure 1‑1. An application for the construction of a geological repository forspent nuclear fuel at Forsmark is planned to be filed in 2011.

Swe
den

According to the regulations from the Swedish Radiation Safety Authority, SSM, a safety assessmentof the planned repository has to be performed before the construction of the repository starts /SSM
2008/. The assessment should focus on potential developments that may lead to the release of radionuclides. SKB launched the project SR-Site to conduct the safety assessment, which is summarisedin the SR-Site main report. This report summarises and gives a synthesis of the biosphere part of
SR-Site and constitutes a supporting document to the application.

Östhammar
municipality

Forsmark
Stockholm

Göteborg
Oskarshamn
municipality

Malmö

Laxemar-Simpevarp

0

100

200

300

400 kmFigure 1‑1. Location of the Forsmark and Laxemar-Simpevarp sites.

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11

The safety assessment SR-Site focuses on three major fields of investigation: performance of therepository, the geosphere and the biosphere. The biosphere part of SR-Site, SR-Site Biosphere,
provides estimates for human exposure given a unit release, expressed as landscape dose conversion
factors (LDFs). Multiplying these factors with modelled release rates from the geosphere results inestimates of the annual doses used to assess compliance with the regulatory risk criterion. The effects
on the environment of a potential release from the repository are also assessed in SR-Site Biosphere.
The work done within the biosphere assessment in SR-Site has been conducted by a number of people.
The major part of the group has been involved from the beginning of the site investigation, via the sitecharacterisation and modelling tasks, and in this final synthesis for the safety assessment SR-Site. The
project members in alphabetic order, their role and affiliation are listed below:
Eva Andersson**, Studsvik Nuclear AB
Karin Aquilonius, Studsvik Nuclear AB
Rodolfo Avila, Facilia AB
Sten Berglund, SKB
Emma Bosson, SKB
Lars Brydsten, Umeå University
Anders Clarhäll, SKB
Per-Anders Ekström, Facilia AB
Anders Engqvist, KTH
Sara Grolander, Facilia AB
Anna Hedenström, SGU
Ulrik Kautsky*, SKB
Tobias Lindborg*, SKB
Angelica Lorentzon af Ekenstam, SKB
Anders Löfgren, EcoAnalytica
Sara Nordén, SKB
Peter Saetre, SKB
Mona Sassner, DHI
Gustav Sohlenius, SGUMårten Strömgren, Umeå University
Björn Söderbäck, SKB
Jesper Torudd, Facilia AB
Mats Tröjbom, MTK AB
Per-Gustav Åstrand, Facilia AB

process descriptions and limnic ecosystems
marine ecosystems
radionuclide modelling and dose assessmenthydrology and near-surface radionuclide transportsurface hydrology and near-surface hydrology
regolith dynamics and lake development and GIS analysis
editorial work
numerical modelling
oceanographysite specific chemical data
regolith
overall biosphere assessments project leader, scientificand method development
site modelling and landscape development
process description and project administrationterrestrial ecosystems and synthesis
radionuclide and element specific properties
data evaluation, synthesis and review of results, editor ofthis reportsurface hydrology
regolith and future land use
GIS analysis, landscape development
site descriptions and historical development
non-human biota assessment
biogeochemistry and mass balances
numerical modelling* project leader SR-Site Biosphere** assistant project leader SR-Site Biosphere12TR-10-09

2

This report

This report is the main document for reporting the biosphere analysis for the SR-Site safety assessment (­SR-Site main report), and as such it provides the background information for conclusions on
the biosphere communicated in the SR-Site main report. This report gives the context of, and thephilosophy behind, the biosphere assessment. It describes the methodologies used and summarises
the most important results. The findings are synthesised and discussed, and the effects of assumptions and uncertainties on the final results is evaluated. All information necessary for a detailed
review and for a reconstruction of the work done can be found in the subordinate reports, which
communicate primary analysis and results (Figure 2‑1).
To make the safety assessment of the planned repository possible, the SR-Site Biosphere project isdivided into a number of subtasks.
1. identify features and processes of importance for modelling radionuclide dynamics of present
and future ecosystems in Forsmark,2. describe the site and predict its future development with respect to identified features and processes,
3. identify and describe areas in the landscape that may be affected by release of radionuclides fromthe planned repository,
4. calculate radiological exposure to a representative individual of the most exposed group in the
future Forsmark landscape, and radiological exposure to the environment.

SR-Site Main report TR-11-01

SR-Site groundwaterflow modelling R-09-20

Climate TR-10-49

Marine Ecosystem Limnic ecosystem
TR-10-03
TR-10-02
Terrestrial Ecosystem
TR-10-01
Process definition
R-10-37
Marine radionuclide
model R-10-10

Biosphere Synthesis TR-10-09

The Forsmark
Landscape TR-10-05

Radionuclide transport
report TR-10-50

Landscape dose conversion factors TR-10-06

Radiological effects onother biota TR-10-08

Regolith -lake development
TR-10-56

Pandora Software R-11-01

Present and future hydrology
R-10-02

Element specific parameters
TR-10-07

Radionuclide transport insurface systems R-10-30

Chemistry for site KD and CR
R-10-28

Present and future chemistryR-10-27
Hydrodynamic modeling of themarine environment R-10-09

SDM
Site description

Figure 2‑1. The hierarchy of reports produced in the SR-Site Biosphere project. This report (market orange)
and its dependencies on information from subordinate biosphere reports (green) and other reports within
SR-Site. Arrows indicates major interactions during project work flow of analysis and results, but interactions have been substantial between most parts of the project throughout the process. The sources of data
should be searched for in subordinate reports if not explicitly pointed out. SDM refers to the site descriptivemodel /­Lindborg 2008/.
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13

2.1

Report hierarchy

In line with other SR-Site reports, main references sited in this report are written in abbreviated form
when they occur in the text. Table 2-1 lists these main references and defines the abbreviations bywhich they are identified in the text hereinafter.
As indicated in the previous section, several of the steps carried out in the SR-Site biosphere assessment result in specific reports that are of central importance for the conclusions and analyses in this
synthesis report. Sections below presents a summary of all SR-Site biosphere reports in the context ofthe subtasks listed in Section 2.0. The content in most reports spans over several of the listed subtasks.
Table 2‑1. Main references sited in this report. All these reports are available at www.skb.se.
Full title

Abbreviation used whenreferenced in this report

Long-term safety for the final
SR-Site Main report
repository for spent nuclear fuelat Forsmark. Main Report of the
SR-Site project.
Long-term safety for KBS-3 reposi- SR-Can Main report
tories at Forsmark and Laxemar- a first evaluation. Main report of
the SR-Can project.
Climate and climate related issues Climate reportfor the safety assessment SR-Site.
Radionuclide transport report forthe safety assessment SR-Site.

Radionuclide transport report

Data report for the safety assessment SR-Site.

Data report

FEP report for the safety assessment SR-Site.

FEP report

Text in reference list (Chapter 13)

SR-Site Main report, 2011. Long-term safety
for the final repository for spent nuclear fuel at
Forsmark. Main Report of the SR-Site project.
SKB TR-11-01, Svensk Kärnbränsle­hantering AB.
SR-Can Main report, 2006. Long-term safety
for KBS-3 repositories at Forsmark and Laxemar– a first evaluation. Main report of the SR-Can
project. SKB TR-06-09, Svensk Kärnbränslehantering AB.
Climate report, 2010. Climate and climate
related issues for the safety assessment SR-Site.
SKB TR-10-49, Svensk Kärn­bränslehantering AB.
Radionuclide transport report, 2010. Radionuclide transport report for the safety assessment
SR-Site. SKB TR-10-50, Svensk Kärnbränslehantering AB.
Data report, 2010. Data report for the safetyassessment SR-Site. SKB TR-10-52, Svensk
Kärnbränslehantering AB.
FEP report, 2010. FEP report for the safetyassessment SR-Site. SKB TR-10-45, Svensk
Kärnbränslehantering AB.

2.1.1 Process understanding
The identification and handling of features and processes that are important for transport and accumulation of radionuclides in the environment is of importance to assessment of human health and safety ofthe environment. Understanding of the site and its development over time is crucial for a successful
identification and handling of relevant features and processes. Thus, SKB has updated the descriptionof biosphere features and processes for the SR-Site safety assessment to reflect the current understandingof ecosystem processes and radionuclide behaviour at the investigated site /­Andersson 2010, Aquionius
2010, Löfgren 2010, SKB 2010/.
2.1.2 Description of the site and its development
The past and present biosphere at Forsmark has been thoroughly described in a number of SKB reports
and articles published in peer-reviewed scientific journals. This knowledge, which constitutes thefoundation for future development scenarios of the Forsmark site, is summarised and synthesised in/­Lindborg 2008/ and /­Söderbäck 2008/.
SR-Site have refined descriptions of the site and its proposed development during non-glacial conditions. Emphasis was put on improving the understanding of features and processes where uncertainties are likely to have a large influence on estimates of exposure. This includes expanded descriptions
on landscape development /­Brydsten and Strömgren 2010, Lindborg 2010/, and present and futurehydrology and hydrodynamics /­Bosson et al. 2010, Karlsson et al. 2010/. Transport and retention ofradionuclides has been simulated with high resolution in present marine and terrestrial ecosystems/­Erichsen et al. 2010, Piqué et al. 2010/. Finally, the SR-Site have improved characterisation ofelement pools and their turnover rates in the present landscape /­Tröjbom and Grolander 2010/.

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2.1.3 Identification and characterization of discharge areas
The discharge of deep groundwater in future landscapes has been used to identify areas that may
be directly affected by released radionuclides from a repository /­Lindborg 2010/. These areas arereferred to as biosphere objects, and extensive work has been invested on detailed description of
the ecosystems that are likely to develop in these areas /­Andersson 2010, Aquionius 2010, Löfgren
2010/, and of their successional development /­Brydsten and Strömgren 2010/. Transport within andbetween biosphere objects have been modelled /­Bosson et al. 2010, Karlsson et al. 2010/ and thepresent retention in regolith and in biota from similar environments at the site has been characterised/­Tröjbom and Nordén 2010, Nordén et al. 2010/. The focused description of the biosphere objects
and their development in time has been the foundation for a site specific parameterisation of themodels used to assess human safety and the protection of the environment (Section 2.1.4).
2.1.4 Radionuclide modelling
Transport and accumulation of potentially released radionuclides to biosphere objects was simulatedwith the radionuclide model /­Andersson 2010/ implemented in the Pandora software /­Ekström 2011/.
The model is based on process understanding from the site, incorporates the development of discharge
areas at the site, and has been parameterised primarily from site data. The exposure of the most exposedgroup was calculated for a constant release rate of radionuclides to the biosphere and for a pulse release/­Avila et al. 2010/. Environmental activity concentrations were used to assess the radiological impact
on the environment /­Torudd 2010/.

2.2

Overview of contents

The report is divided into chapters and sections that will guide the reader through the work flow thathave resulted in quantitative estimates of exposure for humans and other organisms as follows:
Chapter 1 gives a short background to the SR-Site safety assessment and a list of the persons
involved in SR-Site Biosphere.
Chapter 2 (this chapter) is an introduction to the SR-Site Biosphere work. It gives a brief descriptionof the framework and workflow of the project and of the use of the end results.
Chapter 3 puts the biosphere analysis into the context of the SR-Site safety assessment. The chapter
describes the legal requirements related to the assessment of long-term safety of a repository forradioactive waste, and reviews conclusions of previous SKB safety assessments. The SR-Sitesafety assessment is put in relation to international recommendations and to corresponding work incountries with similar plans for storage of used nuclear fuel.
Chapter 4 lists identified features and processes that are important for transport and accumulation ofradionuclides, and for the subsequent exposure of humans and the environment. The identification offeatures and processes is based on the current understanding of the site.
Chapter 5 provides a description of the present-day conditions at Forsmark. The site description
focuses on features and process that are important for transport and accumulation of radionuclides.
The chapter is structured on descriptions of the Forsmark landscape with respect to climate, topography, regolith, near-surface hydrology, coastal oceanography, chemistry, ecology and utilisation of thelandscape by humans.
Chapter 6 describes long-term site development at Forsmark based on climate development according to the SR-Site reference glacial cycle and the SR-Site global warming climate case. The structure
follows that of Chapter 5 (see above). Lakes, streams and wetlands render special attention as they
are the potential discharge areas for deep groundwater. Site development under prolonged warmer
global temperatures is described in the last section.
Chapter 7 identifies the areas in the landscape that are most likely to be affected by a potential
release of radionuclides from the repository, i.e. biosphere objects. The chapter starts with identifying
discharge points for deep groundwater to the surface, followed by a presentation of the principles fordelineating biosphere objects. Finally, positions, properties and temporal development of biosphereobject are described.
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Chapter 8 gives a brief presentation of the mathematical model, assumptions and how the model
calculates transport and accumulation of radionuclides in the biosphere. The radionuclide model
simulates activity concentrations in environmental media (regolith, water, air), and in natural andagricultural food crops, and from these quantify human exposure through relevant pathways. All
biosphere objects and their temporal development during a full period of non-glacial conditions are
considered in the simulations. This chapter also describes the procedures used to assure quality of
data, codes and results.
Chapter 9 presents the input parameters that are needed to calculate radiological exposure. The
chapter describes the principles and methods used to select parameter values that represent the site,
and the procedures used to assure data quality and traceability. Emphasis is put on descriptions ofparameters that serve as input to the radionuclide model.
Chapter 10 describes how the results from the radionuclide model were used to calculate landscapedose conversion factors (LDFs) for a constant unit release rate and for a unit pulse release (LDF
pulse). The results are presented assuming human land use in climate conditions corresponding
to the SR-Site reference glacial cycle or to the SR-Site global warming climate case. Effects ofparameter and conceptual uncertainties on the results are numerically quantified in the last sectionof the chapter.
Chapter 11 summarises the assessment of the radiological impact on non-human biota. Doses toreference organisms and representative species from the site are presented assuming a release ofradionuclides that corresponds to the SR-Site advection/corrosion base case. Results are assessedin the light of regulations and requirements of the Swedish Radiation Safety Authority concerning
protection of the environment.
Chapter 12 synthesises and discusses the results of the biosphere analysis, including evaluation ofassumptions and how they may affect the final results. Starting point for the discussion is identification of radionuclides that are likely to pose greatest risk for human health, followed by discussion
on assumptions and uncertainties regarding activity concentrations in the environment and potential
food resources. The discussion considers human behaviour and land use, configuration and long-termchanges that may affect LDF values.

16

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3

Assessment context

This chapter gives a presentation of the background to the biosphere part of the SR-Site assessment.
It points out the assessment purpose and the constraints that are placed on the assessment. This isfollowed by a section describing the legal requirements in Sweden related to the assessment of longterm safety of a repository for radioactive waste. After that, a description of how the SKB biosphere
analysis and dose assessment relates to international expertise and to corresponding work in othercountries is given, followed by some main conclusions from previous SKB work. The chapter
concludes with a short account of the assessment philosophy.

3.1

Assessment purpose

The main purposes of the safety assessment SR-Site are:•to assess the safety of a potential KBS-3 repository at Forsmark in order to support the licenceapplication,•

to provide feedback to design development, to SKB’s R&D programme, to further site investigations and to future safety assessment projects.

The overall objective of the SR-Site project is to investigate whether the KBS-3 method has thepotential of fulfilling regulatory safety criteria at the Forsmark site, given the level of knowledge on
important conditions and processes in the host rock and in the surface system after completion of thesurface-based site investigations. The assessment is based on a reference design of the engineeredparts of the repository, including reference methods to achieve the specified design, taking into
account methods of ensuring that the specifications of the reference design have been achieved. The
intention is, however, not to finally establish the technical system for disposal, but rather to investigate
the safety of the system as it is specified at this stage, and to give feedback for further developments
to that specification. For the biosphere part of the assessment, the general purpose is to determine theradiological significance of potential future releases of radionuclides from a KBS-3 repository into thebiosphere at Forsmark, and to consider such releases in relation to Swedish regulatory requirements
for solid radioactive waste disposal.

3.2

Preconditions for the SR-Site safety assessment

3.2.1 Repository system
The repository system is based on the KBS-3 method, in which copper canisters with a cast ironinsert containing spent nuclear fuel are surrounded by bentonite clay and deposited at approximately
500 m depth in granitic bedrock (see Figure 3‑1).
The facility design, with rock caverns, tunnels, deposition positions, is based on the design originallypresented in the KBS-3 report /­SKBF/KBS 1983/ which subsequently has been developed and describedin more detail. The deposition tunnels are linked by tunnels for transport and communication, and shaftsfor ventilation. One ramp and five shafts connect the surface facility to the underground repository.
The ramp is used for heavy and bulky transport and the shafts are for utility systems and for transportof excavated rock and backfill material. The different parts of the final repository are sketched in
Figure 3‑2.
Spent nuclear fuel with an initial weight of uranium or heavy metal of around 12,000 tonnes is forecast to arise from the Swedish nuclear power programme, corresponding to roughly 6,000 canisters
in the repository. These figures are based on a reference scenario for the operation of the nuclear
power plants with assumed reactor operational times of 50 years for the facilities at Forsmark andRinghals and 60 years for the Oskarshamn reactors (SR-Site main report).

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Cladding tube

Spent nuclear fuelSurface portion of final repository

Bentonite clay

500 m

Fuel pellet ofuranium dioxide

Copper canister withductile iron insert

Crystalline
bedrock

Underground portion of
final repository

Figure 3‑1. The KBS-3 concept for storage of spent nuclear fuel.

Operational area
• Information buildning• Office building• Staff permises• Ventilation buildning

Exhaust air plant• Elevator buildning• Workshop, garage, storage buildning• Production building• Electrical building, electrical switchyard

Ramp• Transport casks• Bentonite blocks• Building materials

Elevator shaft• Staff• Drainage

Exhaust air shaft• Ventilation

Skip shaft• Rock masses• Backfilling material

Exhaust air shaft• Ventilation• Power supply
Intake air shaft• Ventilation

0

100

200 m

Central area
Deposition area 2

Deposition area 1

Figure 3‑2. Generic example of repository layout.

18

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3.2.2 Site context
This section gives a short summary of the site context. More detailed descriptions are given in
Chapter 5 (Site description) and Chapter 6 (Site development). The Forsmark site is located on
the coast of the Baltic Sea in the county of Uppland within the municipality of Östhammar, about
120 km north of Stockholm, Sweden (Figure 1-1). The planned repository area covers approximately
2·2 km, and is situated immediately southeast of the Forsmark nuclear power plant close to thepresent-day shoreline. The surroundings show small-scale topographic variations of less than
20 metres.
Post-glacial uplift, in combination with the flat topography, implies fast shoreline displacement. This
has resulted in a young terrestrial system that contains a number of recently isolated lakes and wetlands,
and new lakes are continuously formed as a consequence of the regressing shoreline (Figure 3‑3). The
coastline consists of sheltered shallow bays and small islands in an archipelago setting. The seabed in the
coastal areas is dominated by erosion and transport bottoms with heterogeneous sediments, consisting
mainly of sand and gravel with varying fractions of glacial clay.
The major part of the landscape is covered by a thin regolith layer, dominated by till. The mean regolith
depth in the Forsmark area is c. 4 m /­Hedenström et al. 2008/. Exposed bedrock and bedrock with only athin regolith layer (<0.5 m) occupy c. 9% of the area /­Lindborg 2008/. The underlying bedrock consistsof crystalline rock that formed between 1,850 and 1,890 million years ago during the Svecokarelianorogeny, and it has been affected by both ductile and brittle deformation /­Söderbäck 2008/. The ductile
deformation has resulted in large-scale ductile high-strain zones and the brittle deformation has givenrise to large-scale fracture zones. Tectonic lenses, in which the bedrock is much less affected by ductile
deformation, are enclosed between the ductile high strain zones.
Today the Forsmark site has no permanent inhabitants and the surroundings are sparsely populated(see Chapter 5). Land use is dominated by forestry, including hunting. The major food supply forhumans around Forsmark is, as in the rest of society, obtained primarily from general dealers, whichmeans that it is produced at distant farms. Historically, the land use at the site has been dominated byforestry for supply to the ironworks at Forsmark, and by small-scale farming. Before that, from thelast deglaciation until c. 500 BC, the whole area was submerged below the sea /­Söderbäck 2008/.

Figure 3‑3. The coastal area in Forsmark, characterised by small altitudinal differences, shallow coastal
bays and recently isolated small lakes and wetlands.

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3.2.3 Release scenarios and source terms
The release of radionuclides from damaged canisters and the transport from the repository to thebiosphere is not included in the SR-Site biosphere analysis. The chain of calculations that results inthe source term is described in detail in the SR-Site main report. Below follows a brief descriptionof the scenarios that could contribute significantly to the release of radionuclides into the biosphere.
The scenario that results in the largest predicted release of radionuclides to the biosphere is canister
failure as a result of enhanced corrosion due to advective conditions in the deposition hole following
the loss of buffer through erosion (SR-Site main report). For this failure mode, both the canisterand the buffer are bypassed. The rock retention is small since substantial copper corrosion after
buffer erosion only occurs in deposition holes with high flow rates, and these are associated withlow retention flow paths to the surface. Under this scenario, radionuclides from the repository are
unlikely to reach the biosphere within the first 100,000 years.
The probability of canister failure due to rock shear in the event of a large earthquake is very small
during the initial 1,000 years. However, the probability for a canister failure increases cumulatively
with time, and in a perspective beyond 100,000 years this scenario contributes significantly to therisk for release of radionuclides to the biosphere.
Under both the corrosion and the shear load scenarios, the most likely outcome is that only one
canister will fail. Contaminated groundwater from a failed canister may reach the biosphere at different times: the instantaneously accessible fraction of radionuclides from fuel dissolution may reachthe biosphere in a pulse within years or tens of years after failure, whereas the release from the fuelmatrix and corroded metals will result in a continuous release of radionuclides during very long timespans (> million years).
In SR-Site, radionuclide transport and dose consequences have been calculated by a sequence ofmodels (Figure 3‑4). The near-field model describes radionuclide release and transport in the canisterinterior, in the buffer, in the backfill of the deposition tunnel and it handles also the exit pathways
from the near-field. The far-field model is used to describe transport in the water phase from therepository to the biosphere. In the assessment, groundwater flow is primarily modelled through a
discrete fracture network (DFN) where individual fractures are represented explicitly.
The discharge points (exit points in Figure 3‑4), which are simulated in the hydrogeological analysis,
describes where in the landscape the discharge of deep groundwater from the repository could be
expected and during which time periods. Accordingly, the analysis of discharge points includes both aspatial and a temporal dimension. However, it contains no information on the transport of radionuclides
and when they might appear in the biosphere. The far-field transport model delivers radionuclide fluxes
varying over time, however, the results contain no information on where in the surface system radionuclides are released or on the simultaneous flux of water. Thus, the discharge points are decoupled fromthe far field release. Finally, the requirement from the calculation chain is that an a priori conversion
constant without temporal or spatial dimensions is used for calculating dose.
For the assessment of human safety, the radionuclide releases from the geosphere are multiplied by aLandscape dose conversion factor, LDF (see Chapter 10). The LDF describes transport, accumulationand consequences of the subsequent exposure of inhabitants in the biosphere, given a unit release
rate per year of each considered radionuclide. The maximum LDF, taken over all potential discharge
areas and times, is the endpoint of the biosphere assessment. By multiplying the maximum LDF witha release rate, the mean annual dose is obtained. Thus the biosphere assessment provides a conversion
constant, which is used without any spatial or temporal connection to the release. The dose is scaledwith a risk conversion factor (see below) to obtain the mean annual risk, which is the main endpointin the SR-Site safety assessment, see SR-Site main report.
For the assessment of radiological effects on the environment, the release from the geosphere is used
as input into the Radionuclide model for the biosphere (Chapter 8) to calculate activity concentrations
in different environmental media. From these activity concentrations, internal and external exposure
is assessed and the calculation endpoints are incremental dose rates for reference organisms and for
representative species occurring at the site (μGy h–1).

20

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Hydro analysis
Inventory,
IRF and CRF

Canister defectand delay time

Exit points
Near-field flow

Far-field flow
Biospheretransport model

Far-field
transport model

ReleaseSolubilities

Near-fieldtransport model

ReleaseFuel andmetal conversion
rates

LDF values

Site specificbiosphere data

Dose

Migrationand material datafor backfill
Migrationand material datafor bentonite
Groundwaterchemistry

Migrationand material datafor rock

Figure 3‑4. Models and data for the SR-Site consequence calculations (cf. Section 13-4 in SR-Site main
report /­SKB 2010/).

3.3

Regulatory requirements on post closure safety

The form and content of a safety assessment and the criteria for judging the safety of the repository
are defined in regulations issued by the Swedish Radiation Safety Authority, SSM. The regulations
are based on various pertinent components of framework legislation, the most important being the
Nuclear Activities Act and the Radiation Protection Act. Guidance on radiation protection mattersis provided by a number of international bodies, and national legislation is often, as in the case of
Sweden, influenced by international rules and recommendations. There are two more detailed regulations and guidelines of particular relevance for the long-term safety of nuclear waste repositories:•“The Swedish Radiation Safety Authority’s regulations concerning the protection of humanhealth and the environment in connection with the final management of spent nuclear fuel or
nuclear waste”(SSMFS 2008:37) /SSM 2008a/.

•“The Swedish Radiation Safety Authority’s regulations concerning safety in final disposal of
nuclear waste” (SSMFS 2008:21) /SSM 2008b/.

According to the Swedish regulations, human health and the environment should be protected fromthe harmful effects of ionising radiation from the repository. The risk and dose criteria for protectionof human health and environment, which are given in SSMFS 2008:37, are summarised below.

3.3.1 Time frames
The Swedish regulations require that the assessment of potential harm from the repository covers
a period of 1 million years. Moreover, the regulations place stricter requirements on details of theassessment during the earlier parts of the period, i.e. during the first 1000 years after repository
closure and during a period representing a glacial cycle (c. 100,000 years).

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21

In SR-Site, the assessment is divided into four main periods; the initial period after closure, including the buffer resaturation phase, the first 1,000 years after closure of the repository, a complete
glacial cycle (exemplified by Weichsel), and the period up to one million years after closure of therepository. Note that SR-Site covers only the post-closure assessment of the repository; assessmentof human and environmental impacts during the operation phase can be found in the environmental
impact assessment /­SKB 2011/.

3.3.2 Risk criteria for protection of human health
The regulations state that “A repository for spent nuclear fuel or nuclear waste shall be designed so thatthe annual risk of harmful effects after closure does not exceed 10–6 for a representative individual in thegroup exposed to the greatest risk” /SSM 2008a/. Moreover, it is stated that the recommendations of
the International Commission on Radiological Protection (ICRP) Publication 60 /­ICRP 1991/ are to be
used for calculation of the harmful effects of ionizing radiation. According to ICRP Publication No. 60,
the factor for conversion of effective dose to risk is 7.3% per Sievert.
3.3.3 Most exposed group
The most exposed group is not possible to describe in an unequivocal way. /SSM 2008a/ states that“One way of defining the most exposed group is to include the individuals that receive a risk in theinterval from the highest risk down to a tenth of this risk. If a larger number of individuals can beconsidered to be included in such a group, the arithmetic average of individual risks in the group canbe used for demonstrating compliance with the criterion for individual risk in the regulations. One
example of such exposure situation is a release of radioactive substances into a large lake that can beused as a source of drinking water and for fishing”.
/SSM 2008a/ also states that “If the exposed group only consists of a few individuals, the criterion of
the regulations for individual risk can be considered as being complied with if the highest calculated
individual risk does not exceed 10–5 per year. An example of a situation of this kind might be if
consumption of drinking water from a drilled well is the dominant exposure path. In such a calculation
example, the choice of individuals with the highest risk load should be justified by information about
the spread in calculated individual risks with respect to assumed living habits and places of stay”.
It should be noted that there are no prescriptions in the Swedish regulations concerning assumptions
on future human behaviour and land use.

3.3.4 Effects on the environment
For the protection of the environment, no Swedish risk criteria exist. However, /SSM 2008a/ states:“The final management of spent nuclear fuel or nuclear waste shall be implemented so that biodiversity
and the sustainable use of biological resources are protected against the harmful effects of ionisingradiation”.
With reference to the assessment of protection of the environment, the guidance part of the regulations
points out that (unofficial translation from Swedish):“The organisms included in the analysis of the environmental impact should be selected on the basisof their importance in the ecosystems, but also according to their protection value according to otherbiological, economic or conservation criteria. Other biological criteria refers, among other things,
to genetic distinctiveness and isolation (for example, presently known endemic species), economic
criteria refers to the importance of the organisms for different kinds of obtaining a livelihood (forinstance, hunting and fishing), and conservation criteria refers to if they are protected by current
legislation and local regulations. Other aspects, for instance cultural history, should also be taken
into consideration in the identification of such organisms.
The assessment of effects of ionising radiation in selected organisms, deriving from radioactive
substances from a repository, can be made on the basis of the general guidance provided in theInternational Commission on Radiological Protection’s (ICRP) Publication 91 /­ICRP 2003/. The
applicability of the knowledge and databases used for the analyses of dispersion and transfer ofradioactive substances in ecosystems, and for analysing the effects of radiation on different organisms, should be assessed and reported on.”22

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3.4

Relationship to international experience

The Swedish programme for handling and storage of spent nuclear fuel has a substantial history ofworking with international organisations and other national agencies with interests and responsibilities
for radioactive waste management. This international cooperation gives the international community
feedback from practical assessments, as well as feedback to the development of the safety assessment.
Thus, the assessment context is dependent on the current international views of assessments.

3.4.1 Background to international cooperation in biosphere assessments
The Swedish programme has offered a willingness for peer review aspects of its safety assessment
methods, going back as far as 1984 /­Swedish Ministry of Industry 1984/. The reviews presented
included contributions from the IAEA, the NEA-OECD, a Technical Advisory Committee of AECL
(Canada), the French Institute of Protection and Nuclear Safety, the Atomic Energy Research
Establishment (UK), the National Radiological Protection Board (UK), the US National Academyof Sciences, and the British Geological Survey. The reviews specifically included consideration of
the biosphere, as illustrated in /­Hill et al. 1984/. Shortly after that peer review process, the Swedish
Radiation Protection Institute promoted and helped to maintain an international cooperation
programme called BIOMOVS with the primary objectives to• test the accuracy of predictions made by environmental assessment models for selected contaminants and exposure scenarios,• explain differences in model predictions due to structural deficiencies, invalid assumptions and/or
differences in selected input data, and• recommend priorities for future research to improve the accuracy of model predictions.
The programme considered, among others scenarios, a range of very long-term radionuclide releases
to the environment, as might arise as a result of solid radioactive waste disposal in repositories.
The work focussed on scientific issues and the best use of data, allowing specialists to explore anddevelop assessment methods relevant to these long-term situations.
The participants included experts from 22 organisations from 14 countries. One of the model toolsthat was applied to the model testing exercises was BIOPATH, the biosphere model tool used in
the 1983 KBS-3 study, which was subject to review in 1984 /­Swedish Ministry of Industry 1984/.
Following a programme running from 1985 to 1990, in which various exposure situations were
evaluated, a final technical report was issued /­BIOMOVS 1993/ and a second phase of cooperation,
BIOMOVS II, was started.
The BIOMOVS II programme was similar in scope and also had wide international participation.
Consideration was given to identification of critical Features, Events and Processes (FEPs), and thecorresponding relevant model features and data requirements. Results from extensive quantitativemodel inter-comparisons were used to identify which processes could be important in which
exposure circumstances, and what the implications might be of alternative representations of theseprocesses. The BIOPATH model, in use at the time by SKB, was among the ten models tested in thecomparison exercises under the heading of Complementary Studies /­BIOMOVS II 1996b/.
In addition, consideration was given to the development of so-called reference biospheres. The initialidea had been to identify a few key sets of biosphere situations (reference biospheres) and assess theradiological implications of releases in these situations. The intention was to avoid endless speculation about the environmental conditions that might arise by the time of release. The results would be
used as a measuring stick, or point of reference, by which to compare the performance of alternative
disposal systems. However, it was apparent that a limited set of conditions, or reference biospheres,
could not address the range of assessment contexts arising in all the different countries. Apart fromthe geographical and other physical conditions at different sites, it was recognised that the stage inthe development of a repository programme largely determined the necessary and appropriate levelof detail. However, it was agreed that a common approach should be developed internationally tosolve the problem of identifying and justifying appropriate assumptions for environmental conditions
and human behaviour in the long term when addressing a specific site. An outline methodology wasdeveloped, along with a corresponding structured list of FEPs and recommendations for methodology enhancement /­BIOMOVS II 1996a/.
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With the objective of addressing the BIOMOVS II recommendations, the International Atomic
Energy Agency (IAEA) set up a “Reference biospheres” project within its BIOMASS CoordinatedResearch Programme. The project was completed over the period from 1996 to 2001 and built on themodelling and assessment experience within existing programmes, such as that on-going at SKB,
as well as the evolution of international recommendations on radiological protection objectives for
disposal of radioactive waste. Work was carried out under six Task Groups, including the participation of SKB experts and support organisations.

3.4.2 Biosphere analysis and dose assessments in other countries
Many countries are developing deep repositories for radioactive waste. They are at different stages ofdevelopment; some are at a conceptual stage, some are investigating the scope for disposal according
to assumptions related to geology type and corresponding design options, but are non site-specific,
and yet others, like SR-Site are site specific. ‘Reference biospheres’, as discussed above, will be fit
for purpose in the early stages, such as the well scenario described in /­Vieno 1994/. Examples ofgeology-specific cases are given by /­NAGRA 2002/ and /­JNC 2000/, with biosphere assumptions
relevant to the region being investigated. Later stage assessments require substantially more information /­Haapanen et al. 2009/ and more detailed assessment /­US DOE 2008/, so as to meet regulatory
objectives as the programme approaches the licensing stage.
A common feature of the biosphere assessments is the use of assessment biospheres according to /­IAEA
2003/, either in its draft forms or the final version, as a methodological basis for organising and structuring relevant information, and then identifying and justifying the specific assessment assumptions.

3.4.3 Current international projects and related research
A number of international projects that support or have relevance for the biosphere part of a waste
repository performance assessment have been completed or are on-going. A common feature of themodern programmes of research has been the focus on site-specific assessments, which reflects the
progress in stages of repository development.
Among the most substantial international collaboration projects has been the BIOPROTA programme. The project was initiated in 2002 and continues today involving a wide range of operators,
regulators technical support organisations and research institutes from North America, Europe andAsia. Participants include operators, regulators and their technical support organisations, as well as
research establishments. BIOPROTA is designed to support resolution of key issues in biosphereaspects of assessments of the long-term impact of contaminant releases associated with radioactive
waste management.
SKB has been pleased to participate in the project, given the clear focus on scientific evaluation of
the science and site investigation work that can support environmental safety cases and related safetyassessments. SKB has been among those organisations formally publishing the BIOPROTA output
e.g. /­Bergström et al. 2006/.

3.4.4 Application of the BIOMASS methodology in SR-Site
The BIOMASS methodology provides a formal procedure for the development of assessment
biospheres in general /­IAEA 2003/. An assessment biosphere is defined as:“The set of assumptions and hypotheses that is necessary to provide a consistent basis for the
calculations of the radiological impact arising from long-term releases of repository derived
radionuclides into the biosphere.”24

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The methodology is based on a staged approach in which each stage introduces further detail so thata coherent biosphere system description and corresponding conceptual, mathematical and numericalmodels can be constructed. The steps are as follows:•

Define the assessment context•

Identify and justify the biosphere systems to be evaluated•Biosphere system description•

Consideration of potentially exposed groups•

Model development•

Calculation•

Iteration

This subsection provides a commentary on how those steps are matched within SR-Site. Since the startof the SKB s program the iteration has affected all parts in the program and thus the steps indentified
in /­IAEA 2003/ are not necessarily taken in the same order, but rather in parallel. It is also noted thatthe methodological steps are developed through serial investigation of potential sites and site selection,
leading to selection of the Forsmark site for investigation within SR-Site.
Define the assessment context

This chapter sets out the assessment context for the biosphere within SR-Site. The overall objective
is to:•

Set out what is to be assessed and why.

•Set out the initial premises which provide the boundary conditions to the assessment.

•

Define the components of the context, e.g. purpose, assessment endpoints, and societal assumptions,generally issues which are resolved by scientific investigations, but which are needed to make theassessment coherent.

•

Provide a clear record of the purpose of making the calculation.

Identify and justify the biosphere systems to be evaluated

A key issue in identifying biosphere systems is the fact that they are changing with time. SKB haveplaced great emphasis on this issue, because the sites of interest will be subject to substantial environmental change, and this change is explicitly recognised in regulatory guidance.
Environmental changes, primarily driven by climate change and isostatic changes in sea-level at
Forsmark, are addressed in Chapter 6. These changes have substantial implications for the information needed to address the assessment endpoints, and include the importance of various biosphereprocesses and potentially relevant exposure pathways (Chapter 4), the identification of discharge
areas and the development of these over time (Chapter 7), and model assumptions (Chapter 8),
taking into account previous assessment experience.
Biosphere system description/IAEA 2003/ offers suggestions for structuring biosphere system descriptions, and these have beentaken into account in developing the description of Forsmark as it is today (Chapter 5) and how it isexpected to develop as a result of environmental change (Chapter 6). In developing these descriptions, SKB has decided to take a thorough approach to the collection of information about the site,in order to develop an in depth bottom-up understanding of the ecosystems and their evolution, /­see/­Lindborg 2008/.

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Consideration of potentially exposed groups

This is a difficult topic because one cannot reliably predict human behaviour so far into the future as
is required for the safety demonstration. /­IAEA 2003/ proposes the following approach:•review exposure modes and routes relevant within the ecosystems of interest,•

identify and describe coherently human activities within those ecosystems, and•combine human activities and exposure modes to identify those that are most likely to result in
the highest doses.

Taking account of the assumptions for societal behaviour set out in this chapter, the same approach istaken by SKB. Human activities relevant within the ecosystems are set out in Chapter 4, and humanutilization of resources in the area is described in Chapters 5 and 6. From this, reasonable and cautious
assumptions on future human behaviour are developed in Chapter 8, and the most exposed groupwith respect to all potential discharge areas during a full interglacial is in Chapter 10 used to assess
the consequences of a release from the repository.
Model development/IAEA 2003/ suggests the following steps in model development.
•

Identify conceptual model objects, i.e. distinct environmental media potentially influencing doseto the candidate exposure groups.

•

Construct the conceptual model by considering the interactions between the conceptual model
objects.

•

Ensure that no potentially important Features, Events and Processes (FEPs) are omitted from theconceptual model.

•

Identify data sources, define a mathematical model taking account of available data sources andscientific understanding, and derive relevant parameter values according to the data protocol.

•

Incorporate the exposure group information.

SKB has taken the same steps, critically noting first the locations of possible release into the biosphereand describing the biosphere objects at those locations in chapter (Chapter 7). Similar to /­IAEA 2003/,
interaction matrices were used to develop an understanding of how these objects exist together over thearea and ecosystems of interest (Table 4-2). A systematic approach was used to check the inclusion, or
justified exclusion, of potentially FEPs. Two stages were then adopted to model development, first thedevelopment of potential discharge within the Forsmark landscape was modelled (Chapter 6 and 7),then the movement of radionuclides within the evolving biosphere objects was modelled (Chapter 8).
The calculation step in the biosphere assessment of SR-Site includes description of the selection andapplication of appropriate data to the mathematical formulations set out previously, in Chapters 7 and8. similar to the /­IAEA 2003/ protocol for parameter selection. This selection of data and data quality
assurance are described in Chapter 9 and 8, respectively.
Iteration

The same methodological steps have been taken through serial investigation of potential sites and site
selection, leading to selection of the Forsmark site for investigation within SR-Site. As increasing focus
has been given to fewer, now a single, site, it has been both appropriate and possible to give greater
consideration to particularly critical matters of the site, such as the details of the connection between
the geophere with the surface ecosystems, the bio-geochemical features of soils and other importantfeatures of the biosphere.

26

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3.5

Conclusions from earlier SKB work

The methodology for assessment of radiological effects on humans and the environment from a
repository for spent nuclear fuel has developed considerably during the last few decades and SKB
are deeply involved in this development. A number of biosphere assessments have been performed
by SKB, starting with the KBS-3 assessment. The development has regularly been reported in the
RD&D Programme, where /­SKB 2010/ is the latest. A review of the first c. 25 years work with
biosphere assessements is found in /­Edlund et al. 1999/.

3.5.1 KBS-3
Already when the KBS-3 report was presented, the biosphere assessment was state of the art in termsof the consideration that it gave to current trends and knowledge in radioecology and systems ecology. In contrast to most other contemporary work it focussed on a real site. This work also inspired
the implementation of the BIOMOVS international collaboration and its successors, as described in
Section 3.3.
3.5.2 SR-97
With the SR-97 assessment, a spatially distributed model was introduced and site-specific data
were used to parameterise the model. The biosphere was subdivided into different ecosystems, andecosystem-specific dose conversion factors (EDFs) were calculated. Several important issues wereidentified. One of them was the gap in spatial vertical resolution between geosphere models andsurface hydrology, i.e. the geosphere and biosphere interface was inadequately represented. Also,
the importance of being able to communicate across the disciplines covering the repository, thegeosphere and the biosphere in a coherent way was recognised. This was particularly highlighted by
the large ranges of spatial and temporal scales of relevance in repository safety assessment.
It was also recognised that site-specific data regarding the biosphere was lacking in the previous
SKB programmes, which led to the initiation of a collection of biosphere data that was the embryo ofthe site investigation programme for the biosphere. It was also apparent that a biosphere assessment
must be flexible enough to handle a multitude of radionuclides and configurations, thus requiring amore flexible assessment tool. The results clearly showed that the use of a well for domestic water
use as a main indicator in biosphere assessments had several drawbacks, mainly because higher
doses where obtained from other sources. The lack of understanding of forest ecosystems contaminated by groundwater discharge was identified.

3.5.3 SAFE
SR-97 was followed by the renewed assessment of the SFR facility called SAFE, in which thegeosphere-biosphere gap was eliminated and instead substituted by an overlap. However, some of
the tools had difficulties in handling the resolution of the model domain, and there was a need for
expanded site data. These insights contributed to the setup of the SKB site investigation programme,in order to collect better site data, and resulted also in the use of new numerical modelling tools forsurface hydrology, such as MIKE-SHE. Studies of the surface hydrology indicated that discharge
points seemed to be concentrated to low-lying areas, i.e. lakes, rivers, shorelines, a conclusion that has
been further confirmed in SR-Site. The implication of this is that discharge points are not randomly
distributed among the surface ecosystems, but are instead concentrated to specific ecosystems.
The biosphere assessment was in SAFE made directly on the discharge flux, in contrast to the use ofa unit release rate as in the other assessments. The landscape was allowed to change with shoreline
displacement and lake succession. This gave a temporal and spatial connection to the biosphere forthe discharge. There was also an opportunity to collect some more site data that had been identified as
crucial. A large effort was put into a systematic review of potential processes in the biosphere, resulting in the development of an interaction matrix that has been the basis for all following assessments.
An important insight was that there is a local biosphere around the repository that interacts with an
external biosphere. This small concept adjustment has large implications on the use of e.g. concentration factors and other concepts commonly used in the assessment. Moreover, it was recognised that

TR-10-0927

a concentration factor model is not very useful for addressing C-14, the most important radionuclide
in this case, and a programme was initiated to substitute concentration factor models with models
describing fluxes of organic matter and which also can handle point sources. In the assessment, a new
flexible tool for simulation of the C-14 fluxes, implemented in Matlab/Simulink, was tested. This
was the embryo of the tool used today, PANDORA. Moreover, a detailed oceanographic model withhigh discretisation was used to estimate water turnover. This assessment also developed a shoreline
displacement model and the first versions of models for sedimentation and lake succession, models
that have been further developed for SR-Site.
The SAFE assessment was also the first time when the draft version of the SSM regulations wereapplied and discussed. Especially, the concept of “today’s biosphere” was clarified in the authorities’ review, which criticised SKB’s interpretation that it was the biosphere at the moment, i.e. theBothnian Sea, which gave very high dilution and thus low doses. Moreover, the authorities asked forevidence that downstream accumulation gives lower doses than the doses at the point of discharge
into the biosphere. In the SAFE assessment, SKB identified the need for a forest model for the assessment, and this conclusion was reinforced by the authorities. The SAFE project was the foundation forthe biosphere group that has since then continued and extended its work for SR-Can and SR-Site.

3.5.4 SR-Can interim assessment
The development of the safety assessment for the HLW repository included several preparatory
steps. One was a test safety assessment “SR-Can interim”. This was then followed by SR-Can andnow by SR-Site.
In SR-Can interim, the first version of the landscape model was implemented using a new developed
toolbox for Matlab/Simulink called TENSIT. Exposure models were essentially the same as in SR-97
and SAFE, as there were no more site data available. The lessons learnt, besides those resulting in
improvements of the modelling tool which resulted in PANDORA, was that with the models used
the highest exposure was obtained in the first object in a chain or network of objects in a landscape.
It was also realised that data handling and representation increased markedly when addressing alandscape with about 20 objects over 20 time steps. This required improved traceability and error
checking, and to obtain this, new tools for filing and version handling were implemented. It was also
realised that a full probabilistic treatment of a landscape was not a fruitful exercise.
Simultaneously, a large effort was made to implement a site investigation programme which, among
other things, was designed to improve the knowledge database for the surface ecosystems, as well as
providing data on several parameters used in SR-Site.

3.5.5 SR-Can
The SR-Can assessment aimed at presenting the methodology to be used for the application to
construct a HLW repository and to demonstrate the role of the copper canister. In SR-Can, the
PANDORA tool was used extensively and the landscape models were developed further. Site data
were still sparse, but the understanding from the sites had improved substantially. From the transportmodelling it was obvious that discharge from the repository will likely be limited to a restricted
number of objects situated at the lowest points in the landscape, thus mainly lakes, mires, rivers andthe sea. Moreover, it was concluded that forests, located in the more elevated areas, are unlikely
recipients of a release from the repository.
A major step forward was that ecosystem models provided data on the sizes of groups that
potentially will receive doses of different magnitudes. The landscape dose conversion factor (LDF)
was calculated as the maximum dose conversion factor from all objects in a landscape over time.
The risk to a representative member of the most exposed group was calculated with a log-normal
distribution fit to the spectrum of persons receiving the highest dose to one tenth of the highest dose.
The effects on non-human biota were evaluated with the ERICA tool (see description in Chapter 11)
and it was demonstrated that the potential levels of environmental contamination from a repository
were below screening levels discussed for tier 1 (the lowest screening level assessment in the ERICAtool). Furthermore, the concepts for representing the biosphere under conditions of permafrost andgreenhouse warming were sketched out. In the simulations, the landscape changed at 1,000 year28

TR-10-09

intervals and this resulted in artefacts in the calculations. Moreover, the land use at a given timein an object was either agricultural or “natural”, which introduced conceptual misunderstandings,
contradicting the well-based observations from the sites showing a gradual continuum of land use intime and space.
The international review by SSM pointed out several issues. Major concerns were about discretisationof the biosphere, the distribution of the discharge points, and the assessment of potential impact on
non-human biota, which was not regarded as sufficient. Moreover, errors in calculations and parametervalues were pointed out, as well as difficulties in traceability of data and results. The authorities also
requested a presentation of the process understanding. The review comments have been taken into
account in this safety assessment. For instance, some of the more important issues have been addressed
through improved documentation of processes, and use of a clearer hierarchy of reports (outlined inthis report). Traceability in the handling of review issues has been improved with the tools Subversion
and Trac (Section 8.10).

3.6

Assessment philosophy

The assessment context includes what should be assessed, requirements set by the authorities, the international discussions and the history of the SKB biosphere assessment, as well as the constraints that are
imposed by the assessment chain in SR-Site (Figure 3‑4, see also below). Additionally, there are ourown ambitions and goals how to solve the assessment, which we call the assessment philosophy.
The philosophy of the biosphere assessment has been to make estimations of the radiological risk forhumans and the environment as realistic as possible, and as far as possible based on conditions measured at the site. The use of real site data means that assumptions and parameter values can easily be
traced back to the site model and data. The assessment is based on a representative data set where
the measured parameters are sampled at the same site during the same time period, which means that
correlations and dependencies are taken into account. Thus, it is possible to make a scientificallyunderpinned and realistic assessment.
The assessment is based on substantial knowledge of present-day conditions at Forsmark and its past
Holocene history. For the current situation, the uncertainty in assumptions and parameter estimatesis relatively low (Chapter 5). For future situations, uncertainties in the societal development andbiosphere properties are larger, and therefore some cautious assumptions have to be introduced in theassessments (Chapter 8 and discussion in Chapter 12). The only constraints on the future human land
use in the SR-Site assessment are given by what humans reasonably can do in order to (unintentionally)
maximise their exposure to potentially released radionuclides.
In Section 3.2.3, the assessment context for the calculation chain is described. The calculations chain
set the frames and constraints for the biosphere assessment in several ways. Since there is no information on actual releases in time and space available for the biosphere assessment, we assume thatall biosphere objects are equally likely to receive a release, and the release is assumed to be moreor less constant over long periods. The results from the hydrogeological analysis (Figure 3‑4) areonly used only to identify biosphere objects in the biosphere assessment (Chapter 7) where potential
releases might occur at any time, and, equally important, to screen out areas which never will get
any release. This step reduces the number of potential biosphere objects and helps to concentrate thework on specific areas and ecosystem types for further considerations (Chapter 7)
Moreover, because an a priori conversion factor has to be estimated before the results from far field calculations are available, the dose conversion factor for a unit release rate (LDF) is estimated (Chapter 10).
The maximum LDF value over time and across all biosphere objects is used to cautiously reassure thatthe worst instance in time and space is taken into account, regardless of the likelihood of radionuclide
release into that specific object. This maximum LDF, which has no spatial or temporal dimension (even
if detailed temporal and spatial calculations have provided it), is used as the conversion factor in thecalculation chain. Since the maximum LDF is an a priori estimate, no further considerations are madeon whether radionuclides are saturated in the environment or organisms.

TR-10-09

29

The landscape dose conversion factors obtained from the biosphere assessment are best estimates
for the most exposed group from deterministic simulations. These deterministic simulations are
the combined result of process understanding, the most precise description of the site available andrelevant assumptions on societal development. In addition, the effects of parameter uncertainties,
assumptions and conceptual uncertainties on the estimated LDFs have been addressed throughprobabilistic simulations, alternative models and informed assumptions. This approach is consistent
with recommendations from the ICRP /­ICRP 2006/ and with the guidelines from SSM /­SSM 2008/.
We conclude that the current approach is cautious and sufficient to demonstrate compliance with theregulations, but that detailed consideration of the temporal and spatial scales in the assessment canpotentially reduce the LDF.

30

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4

Biosphere features, processes and pathways

This chapter provides a description of processes that are important for transport and accumulationof radionuclides within ecosystems. The knowledge of important processes is used in all aspects ofthe safety assessment, i.e. from site investigations and site description (Chapter 5) to radionuclide
models (Chapter 8) and estimations of exposure (Chapter 10). In addition, exposure pathways forhumans and other organisms are given in this chapter.

4.1

Evaluation of important biosphere processes

4.1.1

Identification of processes for transport and accumulation ofradionuclides in the biosphere
The identification and handling of features, events and processes that are of significance for transport
and accumulation of radionuclides in the environment is important in the assessment of humanhealth and the safety of the environment. Ecosystems are complex with a large number of structuresand functions, and the number of interactions within an ecosystem is unlimited. Thus, a systematic
approach is needed to identify the ecosystems that are likely to receive discharge of contaminatedgroundwater, the compartments where radionuclides may potentially accumulate within theseecosystems, and the processes that affect the transport, accumulation and exposure of organisms andhumans that live in or utilize the ecosystem. For the time frames of a deep geological repository,
the effects of landscape development and ecosystem succession on transport, accumulation andexposure also need to be considered.
The interaction matrix (IM) is a practical tool to display identified components and pathways thatmay potentially affect radionuclide accumulation and exposure. When constructing an IM the major
components of the system (in the case of the biosphere, an ecosystem), are listed along the leaddiagonal of the matrix. The dynamics of the system is then described by processes acting between
the major components. Processes are displayed as off-diagonal elements in the matrix, and represent
direct interactions between two components that will result in a change in at least one of the components. Thus, an IM transparently documents compartments and processes considered in the safetyassessment, and can be used to list the rationale for dismissing identified processes as being of little
or no quantitative importance in a particular safety assessment /­Avila and Moberg 1999, Velasco
et al. 2006, Harrison and Hudson 2006/.
SKB has been working with IM to describe the effects of a potential release of radionuclides fromdeep repositories since the early 1990s /­Eng et al. 1994, Skagius et al. 1995, Pers et al. 1999/. An
early version of the IM for the biosphere was presented in 2001 /­Kautsky 2001, SKB 2001/. SKB
produced the IM for the biosphere with the aid of experts from several scientific disciplines including
geology, oceanography, hydrology, soil science, chemistry, physiology and ecology. For the SR-Sitesafety assessment, the original IM has been updated to reflect the current understanding of ecosystemprocesses and radionuclide behaviour at the investigated site /­SKB 2010/. The understanding reflectedin the IM has been used as help to guide the planning of site investigations, the modelling of the site
and its development, and the development of the radio­nuclide model.
The International Atomic Energy Agency (IAEA) has produced a database of features, events andprocesses (FEPs) that is used in safety assessments of repositories for radioactive waste by a numberof countries. IAEA features and processes associated with the biosphere are included in SKB’s
biosphere IM unless they are clearly irrelevant to Swedish conditions. Definitions of IAEA FEPs
and how they correlate to the process names used by SKB can be found in SKB’s database of FEPs
(FEP report).

TR-10-0931

4.1.2Major components and processes identified in the biosphereassessment of SR-Site
15 components and 51 processes have been identified and described in total in the biosphere IM for
SR-Site /­SKB 2010/ (Figure 4‑1). The identified components primarily represent different environmental media (geosphere, regolith, soil water, surface water, and atmosphere) and organism groups thatare exposed, directly or indirectly, through these media (primary producers, decomposers, herbivores,
carnivores, and humans). In addition, water chemistry, released radionuclides, temperature and external
conditions were also included as separate components in order to increase matrix resolution and to
make the IM more useful for radionuclide pathway analysis.
If the number of leading diagonal components increases, then the number of possible processinteractions and the matrix resolution also increase. To keep the number of diagonal elements manageable they represent broad categories and there will be processes acting within these categories,
i.e. within the diagonal elements. However, the diagonal elements have been selected in such a waythat as many binary interactions as possible are placed in off-diagonal elements. As an example, it
is possible to include water composition in soil water and surface water. However, that would leadto many process interactions occurring within diagonal elements and the IM would not sufficiently
illustrate important radionuclide pathways.
Not all processes between the components in the IM are expected to be quantitatively important fortransport and accumulation of radionuclides from a deep repository in Forsmark. Thus, of the 51 identified processes, 34 were considered to be relevant and sufficient for assessing the safety of human healthand the environment (Table 4‑1). To illustrate the nature of these processes they have been grouped
into six broad categories, namely 1) biological processes, 2) processes related to human behaviour,3) chemical, mechanical and physical processes, 4) transport processes, 5) radiological and thermal
processes and 6) landscape development processes. In the text below, these process categories aredescribed, and key processes are briefly described. A detailed description of all processes is given in/­SKB 2010/, and the rationale for why some of these processes are not relevant in the safety assessment
is provided in /­Andersson 2010, Aquilonius 2010, Löfgren 2010/.
Biological processes

Biological processes are processes that are dependent on organisms. One way of exposure of radionuclides is via intake of water and food and thus the distribution of biota and food-web interactions
is important to consider. In addition, biota may influence the distribution of radionuclides in abiotic
pools by e.g. disturbing sediment or affecting water composition. The biotic processes are generaland may involve both humans and other organisms. Processes that are strictly related to humans
are categorised as processes related to human behaviour (see below). Consumption, decomposition,
excretion, food supply, growth, habitat supply, primary production, stimulation/inhibition, anduptake are biotic processes that influence the distribution of radionuclides in biota and transportof radionuclides in food webs.
The processes bioturbation and particle release/trapping are biotic processes that influence the abiotic
compartment of the environment. Bioturbation influences the properties of the regolith and thereby
affects the accumulation of radionuclides in the regolith. Particle release/trapping influences the amountsof particles in water and air, which is important for the transport of radionuclides adhering to particles.
Processes related to human behaviour

Human behaviour may have large effect on the biosphere, e.g. by introducing species of biota or
chemical elements or by disturbing or removing material in large quantities. Water use, anthropogenic release, and species introduction/extermination are processes related to human behaviour thatare necessary to consider in a safety assessment.
Chemical, mechanical and physical processes

These are processes that result from interactions at varying degree of strength: strong interactions(physical, including mechanical) follow physical laws, chemical laws regulate weaker interactions.

32

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Chemical, mechanical and physical processes can influence the state of elements and compounds,
which can be important for the transport of radionuclides. For example, in some states elements aretightly bound to particles and in other states they may be easily dissolved and transported by water.
Chemical, mechanical and physical processes necessary to consider in the safety assessment are, forexample, element supply, phase transitions and sorption/desorption. Element supply is the amount ofelements available to use for biota and a low element supply may limit the production. The process
phase transition is important, among others, for transport of C-14 from water to air. The process
sorption/desorption determines whether radionuclides are bound to surfaces or dissolved in waterand is crucial to consider when determining the transport and biological uptake of radionuclides.
Transport processes

Transport processes are processes whereby elements and substances are transported from one point
to another in a system. Transport processes important to consider in the safety assessment areconvection, deposition, import, resuspension, relocation and saturation.
Convection includes surface water flow, and groundwater discharge and recharge. Discharge andrecharge are important for the transport upwards from a repository to surface systems and the patternof discharge and recharge is important for understanding why transport of deep groundwater occurs.
Surface water flow is also important for relocation of radionuclides, since relatively fast transport
through the landscape can take place in surface waters compared with groundwater and may affectthe retention time in water bodies. In addition, flooding may cause a redistribution of radionuclides
in the landscape. Radionuclides that have reached the surface system can, via flooding and recharge,
go back to the groundwater system again.
Import is the transport of radionuclides from surrounding ecosystems. This process may be of importance for the amounts of radionuclides in an ecosystem. The processes resuspension, relocation anddeposition are important for the transport from sediment to water column and vice versa. Depositionis, in addition to sedimentation, also used to describe meteorological precipitation, which is important
for water balances and surface water flow. Saturation refers to changes in water content of the regolith,
which is important for the properties of the regolith, which in turn, affect convection as well as living
conditions for biota.
Radiological and thermal processes

Thermal and radiological processes are those processes that concern temperature, solar insolation
and radionuclides. Thermal and radiological processes important to consider in safety assessments
are decay, exposure, light-related processes, and radionuclide release. Radionuclide-specific characteristics influence the transport of radionuclides and are, for obvious reasons, important to consider
in the safety assessment. The amount of radionuclides released, decay and exposure are crucial forthe safety analysis.
The process heat storage has a great influence on both biotic and abiotic components of aquatic
ecosystems influencing e.g. distribution of biota, mixing of the water column, and occurrenceof ice cover preventing exchange across the air-water interface. Light-related processes include
insolation, light absorption, light reflection and light scattering, which influence primary production.
Radionuclide release is the release of radionuclides from the repository and is for obvious reasons
important to quantify in the safety assessment.
Landscape development processes

Type of ecosystem influences transport and accumulation of radionuclides. Landscape development
processes important to consider in the safety assessment are change in rock-surface location, sealevel change, terrestrialisation, and thresholding. Terrestrialisation is the process that turns lakes tomires. Thresholding is the occurrence and location of thresholds that delimit water bodies like lakes
and sea basins. The processes change in rock surface location, sea level change, terrestrialisation andthresholding determine the size and type of ecosystem at the site.

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33

Necessary
for dose
assessment
1
1

GEOSPHERE(B.C.)

Not necessary
for dose
No interaction
assessment
2

3

4

5

6

7

a) Change in rocksurface locationb) Weatheringa) Element supplyb) Habitat supplyc) Light related processesd) Relocation

2a) Consolidationb) Loading

3a) Intrusiona) Bioturbationb) Death4a) Intrusiona) Bioturbationb) Consumptionc) Deathd) Decomposition

5a) Intrusiona) Bioturbationb) Deatha) Consumptionb) Habitat supplyc) Stimulation/inhibition

6a) Intrusiona) Bioturbationb) Deatha) Consumptionb) Stimulation/inhibition

7a) Intrusiona) Bioturbationb) Death

Regolitha) Deathb) Material usec) Relocation

8a) Material supplya) Convectiona) Food Supplyb) Habitat supplyc) Material supplya) Convectionb) Thresholdinga) Food supplyb) Material supplyc) Stimulation/inhibitiona) Excretionb) Uptakea) Decompositionb) Excretionc)Uptakea) Element supplyb) Food supplyc) Habitat supplya) Food supplyb) Habitat supplya) Habitat supplya) Habitat supplya) Habitat supplyb) Stimulation/inhibitiona) Food supplyb) Habitat supplyc) Stimulation/inhibitiona) Food supplyb) Habitat supplyc) Stimulation/inhibitiona) Habitat supplyb) Stimulation/inhibition

Decomposersa) Food supplyb) Stimulation/inhibitiona) Food supplyb) Stimulation/inhibitiona) Food supplyb) Stimulation/inhibitiona) Food supplyb) Material supplyc) Stimulation/inhibitiona) Consumptionb) Habitat supplyc) Stimulation/inhibition

Filter feedersa) Consumptionb) Stimulation/inhibitiona) Consumptionb) Food supplyc) Stimulation/inhibitiona) Food supplyb) Material supplyc) Stimulation/inhibitiona) Stimulation/inhibitiona) Food supplyb) Stimulation/inhibition

Herbivoresa) Food supplyb) Stimulation/inhibitiona) Food supplyb) Material supplyc) Stimulation/inhibitiona) Stimulation/inhibitiona) Consumptionb) Stimulation/inhibitiona) Consumptionb) Food supplyc) Stimulation/inhibitiona) Consumptionb) Stimulation/inhibition

Carnivoresa) Consumptionb) Material usec) Species introduction/
exterminationd) Stimulation/inhibitiona) Consumptionb) Material usec) Species introduction/
exterminationd) Stimulation/inhibitiona) Consumptionb) Material usec) Species introduction/
exterminationd) Stimulation/inhibitiona) Consumptionb) Material usec) Species introduction/
exterminationd) Stimulation/inhibitiona) Consumptionb) Material usec) Species introduction/
exterminatione) Stimulation/inhibition

Primary
producersa) Stimulation/inhibition

9a) Consumptionb) Food supplyc) Material supplyd) Stimulation/inhibition

8a) Intrusionb) Material use

9a) Change of pressurea) Relocationb) Convectionb) Saturationc) Weatheringa) Habitat supplyb) Water supplya) Habitat supplyb) Water supplya) Water supplya) Water supplya) Water supplya) Water supply

10a) Change of pressureb) Convectiona) Relocationc) Loadingb) Resuspensiond) Weatheringa) Habitat supplyb) Relocationc) Water supplya) Habitat supplyb) Relocationc) Water supplya) Habitat supplyb) Relocationc) Water supplya) Habitat supplyb) Relocationc) Water supplya) Habitat supplyb) Water supplya) Habitat supplyb) Water supplya) Convection

11a) Convectionb) Weatheringa) Depositionb) Phase transitionc) Weatheringa) Element supplyb) Food supplyc) Light-related processesd) Stimulation/inhibitiona) Element supplyb) Food supplyc) Habitat supplyd) Stimulation/inhibitiona) Element supplyb) Food supplyc) Stimulation/inhibitiona) Element supplyb) Stimulation/inhibitiona) Element supplyb) Stimulation/inhibitiona) Stimulation/inhibitiona) Convection

12a) Convectiona) Reactionsa) Element supplyb) Stimulation/inhibitiona) Element supplya) Element supplya) Element supplya) Element supplya) Depositionb) Element supplyc) Stimulation/inhibitiona) Convectionb) Phase transitio

13a) Convectionb) Weatheringa) Physical propertiesa) Stimulation/inhibitionchangeb) Weatheringa) Stimulation/inhibitiona) Stimulation/inhibitiona) Stimulation/inhibitiona) Stimulation/inhibitiona) Stimulation/inhibitiona) Phase transitio

14a) Radionuclide
releasea) Depositionb) Irradiationa) Exposurea) Exposurea) Exposurea) Exposurea) Exposurea) Exposure

15a) Change in rocksurface locationa) Importb) Light-related processesa) Importa) Importa) Importa) Importa) Change in rocksurface locationb) Importc) Saturationd) Terrestrialisation

Humansa) Import

Figure 4‑1. The interaction matrix used in the SR-Site biosphere assessment. The diagonal elements (grey)
are key components of an ecosystem. The off-diagonal elements (coloured boxes) represent processes
where by the components interact. The matrix is read clockwise, so that the effect of e.g. Regolith (2:2) on
Primary Producers (3:3) through e.g. supply of nutrients and trace elements is found above the diagonal
in box (2:3), whereas the effects of Primary Producers on the Regolith through e.g. plant Senescence(“death”) is found below the diagonal in box (3:2). An off-diagonal element is empty when two ecosystem

34

TR-10-09a) Uptakec) Water use

Water in rea) Import

/

n

8

9

10

11

12

13

a) Material supplya) Convectiona) Convectiona) Convectiona) Convectiona) Convectiona) Food Supplyb) Habitat supplyc) Material supplya) Convectionb) Thresholdinga) Accelerationb) Convectionb) Thresholdinga) Phase transitionb) Reactionsc) Resuspensiond) Sorption/desorptiona) Reactionsa) Convectionb) Heat storagea) Phase transitionc) Light-related processes r b) Sorption/desorptiond) Pressure changea) Food supplyb) Material supplyc) Stimulation/inhibitiona) Excretionb) Uptakea) Accelerationb) Coveringc) Excretiond) Interceptione) Uptakea) Deathb) Excretionc) Particle
release/trappingd) Uptakea) Accelerationa) Excretiona) Convectionb) Excretionb) Growthb) Light-related processesc) Sorption/desorptionc) Particle releas/trappingc) Reactionsd) Uptaked) Uptakea) Exporta) Food supplyb) Material supplyc) Stimulation/inhibitiona) Decompositionb) Excretionc)Uptakea) Accelerationb) Decompositionc) Excretiond) Movemente) Uptakea) Consumptionb) Deathc) Decompositiond) Excretione) Particle release/trappingf) Uptakea) Excretionb) Uptakea) Excretiona) Convectionb) Growthb) Light-related processesc) Sorption/desorptionc) Reactionsd) Uptakea) Exporta) Food supplyb) Material supplyc) Stimulation/inhibitiona) Accelerationb) Excretionc) Movementd) Uptakea) Deathb) Excretionc) Particle
release/trappingd) Uptakea) Excretionb) Uptakea) Excretiona) Convectionb) Growthb) Light-related processesc) Sorption/desorptionc) Reactionsd) Uptakea) Exporta) Food supplyb) Material supplyc) Stimulation/inhibitiona) Accelerationb) Excretionc) Movementd) Uptakea) Deathb) Excretionc) Particle
release/trappingd) Uptakea) Excretionb) Particle
release/trappingc) Uptakea) Excretiona) Convectionb) Growthb) Light-relaetd processesc) Sorption/desorptionc) Reactionsd) Uptakea) Exporta) Excretionb) Movementc) Uptakea) Deathb) Excretionc) Particle
release/trappingd) Uptakea) Excretiona) Excretiona) Convectionb) Growthb) Particle release/trapping b) Light-related processesc) Sorption/desorptionc) Uptakec) Reactionsd) Uptakea) Exporta) Consumptionb) Food supplyc) Material supplyd) Stimulation/inhibition

Humansa) Water supplya) Uptakec) Water use

Water in regolitha) Accelerationb) Antropogenic release a) Anthropogenic releasea) Accelerationc) Coveringb) Deathb) Anthropogenic released) Excretionc) Excretionc) Excretione) Movementd) Uptaked) Uptakef) Uptakee) Water useg) Water usea) Convectiona) Convectionb) Physical properties
changec) Relocation

1415a) Radionuclide releasea) Exportb) Thresholdinga) Anthropogenic release a) Anthropogenic releaseb) Excretionb) Convectionc) Growthc) Light-related processesd) Sorption/desorptiond) Reactionse) Uptakea) Exporta) Phase transitiona) Convectionb) Heat storagea) Convectiona) Exporta) Habitat supplyb) Water supplya) Convection

Surface water b) Physical propertiesa) Phase transitionb) Relocationc) Resuspensiona) Change of pressureb) Convectiona) Convectionc) Heat storaged) Light related processesa) Exportb) Importa) Stimulation/inhibitiona) Convectiona) Convection

Water
compositiona) Phase transitionb) Relocationc) Resuspensiona) Change of pressurea) Phase transitionb) Light-related processesb) Sorption/desorptionc) Reactionsa) Exporta) Depositionb) Element supplyc) Stimulation/inhibitiona) Convectionb) Phase transitiona) Convectionb) Depositionc) Phase transitiond) Wind stressa) Depositionb) Phase transitionc) Wind stressa) Change of pressureb) Convectionc) Heat storagea) Convectiond) Phase transitionb) Sorption/desorptione) Light-related processesf) Reactionsa) Exporta) Stimulation/inhibitiona) Phase transitiona) Convectionb) Phase transitiona) Convectionb) Physical properties
changec) Reactionsa) Change of pressureb) Convectionc) Phase transitiona) Decayb) Radiolysisc) Reactionsa) Phase transitiona) Decaya) Importb) Reactionsa) Importa) Importb) Light-related processesa) Convectionchangea) Exposurea) Importa) Convectionsb) Importc) Sea level changed) Terrestrialisationa) Importa) Import

Local
atmosphere

Temperaturea) Reactionsb) Phase transition

Radionuclides(*)a) Exporta) Export

External
conditions

components do not interact. Interactions that were considered in detail in the biosphere assessments aremarked in orange, whereas interactions that were judged to have a minor or insignificant effect on thetransport and accumulation of radionuclides are marked in yellow. The details of the biosphere interaction
matrix, and the underlying matrices for the sea, lake and terrestrial ecosystems are presented in /­SKB 2010,
Andersson 2010, Aquilonius 2010, Löfgren 2010/.

TR-10-0935

Table 4‑1. Short definitions of the 34 processes that are included in the safety assessment for
spent nuclear fuel in Forsmark. A fuller description of the processes is given in /­SKB 2010/.
* denotes biological processes that may concern humans in some interactions.
Biological processes
Bioturbation
Consumption*
Death
Decomposition
Excretion*
Food supply
Growth*Habitat supply
Particle release/trapping
Primary production
Stimulation/inhibition*

Uptake*The mixing of elements and particles in both aquatic and terrestrial regolith by organisms.
When organisms feed on solid material and/or on other organisms.
The generation of dead organic matter by organisms.
The breakdown of organic matter.
The excretion of water or elements to the surrounding media by humans and otherorganisms.
The fraction of produced biomass that can be used as a food source for humans andother organisms.
The generation of biomass by organisms
The providing of habitat for organisms by abiotic elements or other organisms.
Organisms release particles (for example by fragmentation, spawning and pollen
release) or trap particles (for example with gills, feathers and slime).
The fixation of carbon by primary producers in photosynthesis.
When one diagonal element positively or negatively influences another diagonal
element. The extreme of inhibition prevents an interaction completely and leads to
exclusion from the model domain (e.g. primary production is not possible below thephotic depth in lakes and sea).
The incorporation of water or elements from the surrounding media into humans andother organisms.

Processes related to human behaviour
Anthropogenic release
Species introduction/
extermination
Water use

Release caused by humans of substances, water or energy into the local biosphere.
(For example irrigation of vegetables).
Introduction or extermination of species from the model area by human activities(e.g. introduction of crayfish in lakes).
Water used by humans for other purposes than drinking, e.g. washing, irrigation andenergy production. This process may affect the water table.

Chemical, mechanical and physical processes
Element supply
Phase transition
Physical properties change
Sorption/desorption
Wind stress

The availability of elements and substances for use by organisms.
Changes between different states of matter: solid, liquid and gas.
Changes in volume, densities and/or viscosity.
Dissolved substances adhere to surfaces or are released from surfaces.
A mechanical force generated by wind.

Transport processes
Convection
Deposition
ImportRelocation
Resuspension

The transport of a substance or a conserved property with a fluid or gas.
Vertical transfer of a material or element to a surface of any kind due to gravitation,e.g. sedimentation, rainfall, and snowfall.
Transport into the model area.
Transport of solid matter and sessile organism from one point to another.
The stirring up of previously settled particles in water or air.

Radiological and thermal processes
Decay
Exposure
Heat storage
Light-related processes
Radionuclide release

The physical disintegration or transformation of radionuclides to other radionuclides or
stable elements.
The act or condition of being subject to irradiation. Exposure can either be external
exposure from sources outside the body or internal exposure from sources inside
the body.
The storage of heat in solids and water.
Processes related to the light entering the biosphere (insolation), e.g. absorption,
attenuation, reflection and scattering.
Release of radionuclides from the repository for spent nuclear fuel.

Landscape development processes
Change in rock surface
location
Sea level change
Terrestrialisation
Thresholding

36

Changes in the location of the rock surface due to isostatic rebound or repositoryinduced changes.
Alteration in the level of the sea relative to the land.
Infilling of a lake or shallow sea basin with mire vegetation.
The occurrence and location of thresholds delimit water bodies like lakes and sea basins.

TR-10-09

4.2

Exposure pathways

Man and other organisms can be exposed to radionuclides both externally and internally in theenvironment. Exposure pathways identified as significant from an analysis of a diverse use of natural
resources that can be observed today have been included in this safety assessment /­Avila et al.
2010/. These pathways are briefly described below whereas a fuller description and a discussion of
exposure pathways considered but found to be insignificant (e.g. the use of contaminated peat) arepresented in /­Avila et al. 2010/.
Based on earlier assessments /­Bergström et al. 1999, Avila and Bergström 2006, SR-Can main
report/ it is concluded that the major long-term risk for human exposure to radionuclides from a
repository is from internal exposure. The internal exposure is always preceded by incorporation ofradionuclides into the human body. This can occur mainly by ingestion of contaminated water andfood or inhalation of contaminated air.
The internal exposure will, among other things, depend on the fraction of contaminated food andwater consumed and the level of activity in the food and water. In this methodology, it is assumed
that all water and food is contaminated, but other situations can easily be addressed by introducing
corrections to account for the fraction of consumed water and food that is not contaminated. The
dietary composition can also have an impact on the internal exposure, as different foods can havedifferent contamination levels. However, for long-term assessments it is difficult to postulate aparticular dietary composition, as the human habits and choices may change. Food intake and foodproduction are important processes that will affect the potential exposure of humans to radionuclides
derived from the repository. The assumptions on human food consumption are discussed in moredetail in Chapter 12.
The exposure via inhalation of contaminated air can occur both outdoors and indoors. However,exposure indoors may be lower than outdoors due to the filtering effects of buildings. In SR-Site,
only outdoor exposure (hundred percent of time) was considered, which in most cases gives aconservative estimate, as the radionuclide contamination of the air comes from resuspension of soil
particles. The situation could, however, be different for isotopes of elements that can exist in gas formin the environment. No separate biosphere assessment is carried out for such radionuclides. However,isotopes that are likely to enter the gas phase to any significant extent are assessed in Section 13.8
in the SR-Site Main Report. Other pathways for radionuclide penetration into the human body, forexample through the skin, are of little significance in comparison with the pathways that are assessed/Avila et al. 2010/.
The external exposure comes from radiation emitted by the radionuclides in surrounding environmental media, comprising air, water, soils and sediments. Previous safety assessments of planned
geologic repositories /­Bergström et al. 1999, Karlsson and Bergström 2000, SR-Can main report/
have shown that, for most radionuclides of interest, external exposure gives a minor contribution to
the total dose. Thus, in most cases, external exposure contributes only marginally to total risk.

TR-10-0937

5Site description – present-day conditions
at Forsmark

This chapter provides a brief description of the present-day conditions at Forsmark, based on available knowledge from the site investigations. More detailed descriptions of the site can be found in
the site description report for Forsmark /­SKB 2008/ and in the report describing the surface systems
at Forsmark /­Lindborg 2008/.
Understanding of surface systems at the Forsmark site needs a combination of information fromseveral scientific disciplines in order to give an overall picture of factors forming the conditions in
the present landscape. Moreover, the present conditions could not be understood without a historic
perspective that forms a basis for understanding of the continuously transforming landscape. Abiotic
factors set the limits and create prerequisites for the formation of ecosystems, which in turn affectthe physical environment via feedback mechanisms.
The chapter starts with a presentation of the abiotic characteristics of the Forsmark area which sets
the physical and chemical limits for the formation of ecosystems (Section 5.1), and continues with an
overview of the present-day ecosystems of the site and of the utilisation of the landscape by humans(Section 5.2).

5.1

Abiotic characteristics

Abiotic characteristics like topography and climate, as well as physical properties of the bedrock,regolith and water, set the limits for development of ecosystems and human utilization of thelandscape. Abiotic factors, the development of ecosystems and the resulting chemical environment
are interdependent; the formation of ecosystems influences abiotic factors such as soil properties,
as well as hydrochemical characteristics of the surface water, whereas the chemical environment inturn gives prerequisites for the formation of specific ecosystems. The abiotic factors and conditions
described in this section are important for the understanding of the present-day Forsmark area andconstitute important input parameters in the radionuclide transport modelling.

5.1.1 Topography
The topography of the Forsmark area is characterised by a low relief (Figure 5‑1). In terrestrial
areas, elevation differences are usually less than 20 metres. Prominent topographical features ofthe landscape are the relatively small glacial landforms like eskers. The relief is more pronounced
west and south of the Forsmark area, where the relative relief reaches 50 metres in a landscapecharacterised by bedrock lineaments and fracture zones oriented largely in the directions of N-S and
NW-SE (Figure 5‑2) /­Olvmo 2010/.
SKB has developed a digital elevation model (DEM) to describe the topography of the area
(Figure 5‑3). The DEM, which covers an area of approximately 30 km · 30 km serves as input toother models for projection of both past and future conditions. The DEM is a central data source forthe site characterisation, and is used as input to most of the descriptions and models produced for thesurface system. Detailed descriptions of the DEM are provided in /­Brydsten and Strömgren 2004/ and/­Strömgren and Brydsten 2008/.

5.1.2 Regolith
The term regolith refers to all loose material overlying the bedrock. The major portion of regolith at
Forsmark is glacial deposits, reworked during multiple glaciations and relocated by subsequent glacialand post-glacial processes. The upper part of the regolith is affected by deposition and decompositionof organic material, and in terrestrial areas also by weathering of the original material, thus forming
soil in terrestrial areas and sediments, often rich in organic matter, in aquatic areas. Data describing
regolith properties is an important input when modelling the hydrology and transport of elements andvarious compounds within the geosphere and between the biosphere and the geosphere. Soil properties are also strongly associated with classification of vegetation types and land use in the terrestrial
ecosystem, and regolith data therefore contribute to the prediction of future vegetation types when thepresent-day sea floor becomes parts of the terrestrial system following isostatic rebound.
TR-10-0939

Figure 5‑1. The Forsmark area seen from south-east, with the only larger arable land area, Storskäret,in the foreground.

Figure 5‑2. Topography of the region around Forsmark illustrated by relative relief, in this case calculated
as maximum elevation range within grid cells of 300 x 300 metres. The relative relief is less than 20 metresin most parts of the area, which makes glacial landforms like eskers (north-south trending lines of yellow
pixels north of Uppsala) protrude more than bedrock hills. Figure from /­Olvmo 2010/.

40

TR-10-09

Figure 5‑3. The digital elevation model (DEM) for the Forsmark area describes the topography (including
the present-day bathymetry). The current shoreline is illustrated by a light blue line. Figure modified from/­Strömgren and Brydsten 2008/.

Regolith distribution and properties

Approximately 90% of the ground surface in the Forsmark area consists of regolith that originatesfrom the last glaciation when the ice sheet reworked and redistributed sediments of earlier Quaternary
glaciations. The distribution of regolith, shown in Figure 5‑4, follows the general pattern for areas in
Sweden below the highest postglacial coast-line. Elevated parts of the terrain are dominated by till or
exposed bedrock and valleys have a higher percentage of clay and postglacial redeposited fine-grainedmaterial. Till constitutes the dominant regolith exposed at the ground surface, occupying approximately
65% of the terrestrial surface areas and 30% of the area currently submerged by the sea. Generally,
the till is thicker in depressions, thus levelling out some of the bedrock relief. The till in the Forsmark
area is subdivided into 1) a sandy till with medium frequency of superficial boulders (dominant), 2) aclayey till with low boulder frequency, and 3) a sandy till with high boulder frequency /­Hedenström
and Sohlenius 2008/. Clay, gyttja clay, sand and peat occur frequently but scattered, mainly covering
smaller patches. Peat accumulation occurs in all Forsmark wetlands, but deposits thicker than 0.5 m
are restricted to the south-western part of the investigated area. This is the most elevated part of theForsmark area and has therefore experienced terrestrial conditions and peat accumulation for the longest
time /­Fredriksson 2004/.

TR-10-0941

1630000

1635000

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Quaternary deposits

0Peat and gyttja

Glaciofluvial sediment

Clay-silt (not specified)

Till

Postglacial clay and clay gyttja

Clayey till or boulder clay

Glacial clay

Precambrian bedrock

Postglacial sand - shingle

Artificial fill

1

2

4 km

© Lantmäteriverket Gävle 2007.
Consent I 2007/1092
2008-02-11, 10:00±

Figure 5‑4. The distribution of regolith at Forsmark, characterised at 0.5 m depth /­Hedenström andSohlenius 2008/. It should be noted that the areas presently submerged by water (limnic and marine
environments) are presented without water. The black line shows the extension of the regolith depth model(Figure 5‑5). Figure from /­Hedenström and Sohlenius 2008/.
Table 5‑1. The proportions (%) of areas covered with different Quaternary deposits (characterised at 0.5 m depth) and bedrock exposures, overall and in subareas of the Forsmark area. The
subareas are described in /­Figure 2-3 in Hedenström et al. 2008/. Terrestrial refers to all areas not
submerged by the sea.
All areas

Terrestrial

Marine area

Bedrock exposures

9

13

6

Glacial clay

25

4

41

Postglacial clay (including gyttja clay and gyttja)

11

4

17

Postglacial sand and gravel

4

2

6

Till total (sandy/clayey)

48.5 (46/2.5)

65 (58/7)30

Glaciofluvial sediment

0.5

1

0

Peat

1

8

–

Artificial fill

1

3

–

42

TR-10-09

A high content of calcium carbonate (CaCO3) is recorded in a majority of the glacial deposits/­Hedenström and Sohlenius 2008/. The carbonates originate from Palaeozoic limestone on thebottom of the Bothnian Sea, brought to Forsmark by glacial transport. Due to continuous weathering,
the CaCO3 affects shallow groundwater and soil conditions by increased concentrations of calcium
and bicarbonate /­Tröjbom and Söderbäck 2006/. The soil types in the area are typically of low
maturity and lacks well developed soil horizons because of the relatively short period of exposure tosoil-forming processes /­Lundin et al. 2004/.
Regolith depth and stratigraphy

Information on regolith depth and stratigraphy in Forsmark is extensive as a result of drillings,
excavations and geophysical measurements during the site investigations /­Hedenström and Sohlenius
2008/. This information is used for interpolation in a regolith depth model /­Hedenström et al. 2008/
to get a total coverage of estimated regolith vertical distribution (Figure 5‑5). Regolith in the model
is subdivided into seven layers and three generalised lake sediment lenses. The total regolith depth
in the model varies between 0.1 and 42 m. Areas with thin regolith and frequent bedrock outcrops
are mainly the coastal zone and the islands, including the coastal zone of Gräsö Island. Generally,

1630000

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6708000
6706000
6702000
6700000
6698000
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6696000

6698000

6700000

6702000

6704000

6706000

6708000

6710000

1628000

6710000

1626000

6704000

D:\GIS\SR_Site\Bearbetad_data\Mxd_TR_10_09\Fig6_5.mxd

1624000

Regolith depth, m

3.01 - 5

15.01 - 20

0-0.1

5.01 - 7

20.01 - 25

0.11 - 1

7.01 - 10

25.01 - 42.38

1.01 - 3

10.01 - 15

Model area regolith model
Present shore line

0

1

2

4 km

±

Bakgrundskartor © Lantmäteriet
SKB/skbebo 2011-01-18 10:12

Figure 5‑5. Total modelled regolith depth at Forsmark. Figure from /­Hedenström et al. 2008/.

TR-10-0943

the regolith is deeper in the marine area where the average regolith depth is c. 8 m, whereas theaverage regolith depth in the terrestrial area is approximately 4 m. A reason for thicker sediments inthe marine areas is the local bathymetry; the submarine N-S trending trough west of Gräsö Island has
functioned as a sediment trap, enhancing deposition both due to glacial and postglacial processes.
The stratigraphical distribution of till is homogenous in most parts of the area, however, a more
complex till stratigraphy has been observed at some sites. The distribution of sediments in the lakes
and ponds is fairly uniform, with generally thin sediment sequences. The total thickness of water-laid
sediments is less than 2 metres in the majority of the investigated lakes /­Hedenström 2004/. Basedon the results from the site investigations, a general stratigraphy for the Forsmark area is shown in
Table 5‑2.
An inventory of small and shallow basins located in the central part of the investigation area showedthat approximately half the investigated sites had a layer of clay under organic sediments /­Sohlenius
and Hedenström 2009/.

5.1.3 Climate
The mean annual temperature at Forsmark is approximately +7°C (Table 5‑3), measured during threesubsequent years (Jan. 2004–Dec. 2006) at two meteorological stations in the vicinity of Forsmark.
The temperatures are slightly milder at the station closest to the coast. The dominating wind directionin the area is from south-west. The region shows a strong precipitation gradient in the east-westerly
direction. The annual corrected precipitation in the Forsmark area during the studied period was
546 mm/y /­Johansson 2008/, to be compared with the 30 year long-term mean precipitation of
690 mm/y 15 km west of the Forsmark area, and only 490 mm/y at a similar distance north-east ofForsmark /­Larsson-McCann et al. 2002/.
Snow cover in the area has been measured weekly during five seasons (2002/03–2006/07). On average, snow covered the ground for 105 and 80 days/season on forest land and open land, respectively,
and the period of snow cover was typically from the end of November until the beginning of April/­Löfgren 2008/. The maximum snow depth recorded was 48 cm in forest land and 25 cm in open land,
and the maximum snow water content was 144 and 64 mm, respectively. Measurements of ground
frost penetration during three seasons (2003/04–2005/06) showed that ground frost was present for
40 and 80 days/season in forest land and open land, respectively. The maximum ground frost depth
was 46 cm on open land, and only 8 cm on forest land.
Table 5‑2. The general stratigraphical distribution of Quaternary deposits in the Forsmark area/­Hedenström and Sohlenius 2008/. It should be noted that not all deposit types are always
present at the same site. Gyttja is formed in lakes and consists mainly of remnants from plantsthat have grown in the lake.
Quaternary deposit

Relative age

Environment

Bog peat

Youngest↑

Bog

Fen peat
Microphytobenthos/calcareous gyttja/algal gyttja
Clay gyttja-gyttja clay
Postglacial sand/gravel↑↑

Glacial clay
Glaciofluvial sediment

Lake
Coastal and lake
MarineGlacio-lacustrine

Till

↑

Bedrock

Oldest44

Fen

GlacialTR-10-09

Table 5‑3. Some climate characteristics for the Forsmark area. Data are for 2004 to 2007 from
Storskäret, Forsmark /­Johansson 2008/.
Forsmark area

Latitude, longitude

60° 22’ N, 18° 11’ E

Mean annual temp.

+7°C

Min.–max. daily temp.

–14 – +25°C

Mean annual precipitation (mm)546

Vegetation period

May–September

Length of vegetation period* 2004–2006

204 days*Starts when 5 consecutive days have a daily mean >+5°.
Ends when 4 consecutive days have a daily mean <+5°.

5.1.4 Surface hydrology
The overall aim of the hydrological description is to describe objects such as lakes, watercourses andaquifers, primarily in terms of their geometries and hydraulic properties. Modelling of the hydrological surface system gives information on interaction between the objects and the integrated hydrological system at the site, and produces an overall water balance for the area. Important results presented
within the framework of the site description /­Johansson 2008/ include delineations of surface-water
catchment areas, hydraulic parameters of the regolith, water balances, cross sections and elevation of
streams, and lake turnover times.
In total, 25 lake-centered catchment areas, ranging in size from 0.03 to 8.67 km2, have been delineated
and described within the Forsmark area /­Brunberg et al. 2004, Andersson 2010/. The 25 lakes are
all small and shallow with mean and maximum depths ranging from approximately 0.1 to 1 m and
0.4 to 2 m, respectively (Figure 5‑6). Seawater flows occasionally into lakes close to the sea during
events of higher sea level. Wetlands are frequent and cover 25 to 35% of some of the catchments/­Johansson 2008/.

Figure 5‑6. Lake Eckarfjärden, one of the larger lakes in the Forsmark area. Eckarfjärden is, like all otherlakes in the area, a shallow oligotrophic hardwater lake surrounded by reed.

TR-10-0945

No major watercourses flow through the central part of the site investigation area, and most streams
in the area dry out during parts of the year (Figure 5‑7). Downstream of the lakes Gunnarsboträsket,
Eckarfjärden and Gällsboträsket the streams carry water for most of the year, except for dry years
such as 2003 and 2006. Many streams in the area have been straightened and deepened in order toincrease drainage.
The long-term overall water balance in the area was roughly estimated from measurements ofprecipitation, surface discharge and water levels during the period April 2004–April 2007 /­Johansson
2008/ (Table 5‑4). Numerical modelling of the surface water and groundwater flow systems has been
performed using the MIKE SHE tool /­Bosson et al. 2008/. The modelling results for surface waterand groundwater levels and the main water balance components are in agreement with the resultsfrom field measurements.
Table 5‑4. Longterm water balance for Forsmark, based on statistical calculations and measurements during the period April 2004–April 2007 /­Johansson 2008/.
Parameter

Precipitation (P)560 mm/year

Actual evapotranspiration (ET)

400–410 mm/year

Runoff (R)

150–160 mm/year

Figure 5‑7. The largest stream in the site investigation area in Forsmark, near the inlet to Lake
Bolundsfjärden (May 2007).

46

TR-10-09

Direct groundwater recharge from precipitation is the dominant source of recharge. Generally, the lakes
are locations for discharge of groundwater for most of the year. During summer, when groundwaterlevels in the vicinity of the lakes are lowered by plant water uptake, some of the lakes may periodicallychange from discharge to recharge areas. Due to a high infiltration capacity of the topmost regolithlayer, overland flow rarely occurs in unsaturated areas. However, overland flow may occur in saturated
areas where the groundwater level reaches the ground surface. The runoff in streams is dominatedby water of groundwater origin. During intensive rain-events or snow-melt, overland flow may also
contribute substantially to the runoff.
The hydraulic conductivity (K) of the till is typically in the range 10–7 to 10–4 m/s. The hydraulic conductivity is comparatively high in the uppermost c. 0.5 m of the till, and then decreases with depth in
the regolith profile. However, the hydraulic conductivity is again comparatively high in the zone closest
to the bedrock /­Johansson 2008/. The high hydraulic conductivity in the uppermost till is probably due
to the combined effect of several soil-forming processes (e.g. bioturbation by roots and soil organisms
and ground frost), which results in increased porosity and permeability.
The small-scale topography of the area gives rise to many small catchments with local, shallow
groundwater flow systems in the regolith. This, in combination with the decreasing hydraulicconductivity with regolith depth, means that a dominant part of the near surface groundwater will
move along shallow flow paths. Shallow groundwater flow paths imply strong interactions among
evapotranspiration, soil moisture and groundwater levels and flow. In Forsmark, the groundwatertable in the regolith is very shallow, in general the depth to the groundwater table is less than ametre. The groundwater level in the regolith is highly correlated with the topography of the groundsurface. This local flow system in the regolith overlies a larger-scale flow system in the bedrock.

5.1.5 Coastal oceanography
The marine part of the Forsmark area is located in Öregrundsgrepen, a funnel-shaped bay of theBothnian Sea which is a part of the Baltic Sea with its wide end to the north and the narrow end
southwards. The studied area was divided into 28 sub-basins, based on today’s bathymetry and the
projected pattern of future drainage areas arising in consequence of isostatic rebound /­Brydsten
2006/. The sub-basins are presented in Figure 5‑8, together with the DEM for the marine area at
Forsmark. The major part of the area is shallow and most sub-basins show a mean depth shallower
than 10 m. The only exception is the N-S trending deeper channel west of Gräsö Island, exceeding
depths of 40 m. The salinity stratification in Öregrundsgrepen is generally weak. Local freshwaterrunoff produces slightly lower salinities in the area compared with the Bothnian Sea /­Aquilonius
2010/. The direction of the flow through Öregrundsgrepen varies from time to time, but on an annual
basis there is a net flow directed from north to south /­Karlsson et al. 2010/.
Marine sub-basins in the area were identified from the DEM /­Strömgren and Brydsten 2008/ (Figure 5‑8).
The water retention time in the 28 sub-basins varies between 13 and 34 days (22 on average) /­Karlsson
et al. 2010/. The more rapid water turnover is found in the deeper areas close to the open Bothnian Sea
and the longest retention in the partly isolated shallow sub-basins 117 and 118.

5.1.6 Chemistry
The present chemical characteristics at Forsmark are a consequence of the past landscape development, together with the abiotic and biotic factors acting today. The description presented below isbased on extensive studies reported in /­Sonesten 2005, Tröjbom and Söderbäck 2006, SKB 2008,
Tröjbom et al. 2007, Hedenström and Sohlenius 2008, Andersson 2010, Löfgren 2010, Aquilonius
2010, Tröjbom and Nordén 2010, Tröjbom and Grolander 2010/.
Fresh surface waters and shallow groundwater in the Forsmark area are generally characterised byhigh contents of marine ions, high pH and high alkalinity, as well as very high concentrations ofcalcium compared with the general conditions in Sweden. These site-specific characteristics canbe explained by marine remnants left by a regressing Baltic Sea, together with glacial remnants inthe form of the calcite-rich till layer deposited during the Weichselian glaciation /­Sonesten 2005,
Tröjbom and Söderbäck 2006, Tröjbom et al. 2007/.

TR-10-0947

Figure 5‑8. Marine sub-basins used in the SR-Site assessment, projected on the bathymetric map ofForsmark. Numbers are identification numbers of the sub-basins. Figure from /­Aquilonius 2010/.

The influence from calcite has had a strong effect on the development of the terrestrial and limnic
ecosystems in the Forsmark area. Secondary precipitation of calcite, with co-precipitation ofdissolved phosphorus, mediates the development of the nutrient-poor oligotrophic hardwater lakes
which are typical of this region (Section 5.2.2). In comparison with other parts of Sweden, lakes in
the Forsmark area are characterised by low concentrations of phosphorus and high concentrationsof nitrogen and dissolved organic carbon /­Brunberg and Blomqvist 1999, Tröjbom and Söderbäck
2006/. The rich supply of calcium also influences soil formation and the development and structureof the terrestrial ecosystems /­Löfgren 2010/.
The distribution of different elements among biotic and abiotic pools gives, together with estimates of
element fluxes in to and out of the pools, an overall picture of major sources and sinks of elements inthe landscape. Based on measured element concentrations in a large number of organisms, in different
parts of the regolith and in lake water /­Löfgren 2008, Nordén et al. 2008/, the amounts of different
elements in major terrestrial and limnic ecosystems pools have been estimated at the landscape level/­Tröjbom and Grolander 2010/. The results show that the completely dominating fraction for mostelements in both terrestrial and limnic ecosystems is found in the regolith pools, i.e. in soils andsediments. The only pools in the landscape that are not negligible in comparison with the total regolithpool are those of nutrients and essential trace elements found in organisms in terrestrial ecosystems.
The terrestrial biota pools in Forsmark are usually much larger than the corresponding limnic pools.
Major element fluxes in the Forsmark landscape have been quantified by the use of a simple massbalance model /­Tröjbom and Grolander 2010/. This model couples major sources of elements
48

TR-10-09

released in the system (i.e. atmospheric deposition, fixation of gases, weathering of regolith andbedrock and flushing of relict sea water) to major sinks (i.e. accumulation in the terrestrial and limnic
systems, export via surface water and emissions to the atmosphere) at the landscape level. The massbalance indicates large differences among elements in terms of transport and retention in the landscape,depending on their properties and biological functions (Figure 5-9). For a number of metals in theupper part of the figure, input from the atmosphere is equal to or exceeds the known sinks, which
implies that a significant fraction is retained in the terrestrial system. In the lower part of this figure,atmospheric deposition balances only a minor fraction of the known sinks, which means that weathering reactions and other processes in the terrestrial system are the main sources of these elements.

5.2

Ecosystems

This section presents a general description of the ecosystems in the Forsmark area. Detailed information on biomass, production, chemical composition, and turnover of tissue and carbon content used in
the ecosystem models can be found in the ecosystem reports; terrestrial ecosystems /­Löfgren 2010/,
limnic ecosystems /­Andersson 2010/ and marine ecosystems /­Aquilonius 2010/.

5.2.1 Terrestrial ecosystems
Terrestrial vegetation is strongly affected by the topography, regolith characteristics and humanland use. In Forsmark, 73% of the terrestrial area is covered by forests, dominated by Scots pine
(Pinus sylvestris) and Norway spruce (Picea abies), which are the dominating tree species in the
boreal forests of Scandinavia. The relative large portion of a variety of deciduous trees is both aconsequence of the previous or present human land use and of the location by the coast. The fieldlayer is characterised by herbs and broad-leaved grasses, along with a number of orchid species,
favoured by the calcareous soils. The area has a long history of forestry, in recent times generally
managed by clear-cutting.
Wetlands occur frequently and cover 10–20% of the area, locally reaching a coverage of 25–35%
in some sub-catchments /­Johansson et al. 2005/. A major part of the wetlands in the Forsmark area
consists of coniferous forest swamps and open mires (Figure 5‑10). The less mature wetlands consistof moderatly to extremely rich fens /­Jonsell and Jonsell 1995/, which is a consequence of the highcalcareous content of the local regolith (Section 5.1.2). Arable land and pastures are found close tosettlements, including settlements now abandoned. The grasslands were earlier intensively managed,
but a majority are no longer managed following the nation-wide general regression of cultivatedland. The spatial distribution of different vegetation types is presented by /­Löfgren 2010/.
The most common larger mammal species in the Forsmark area are roe deer and moose. Wild boar
occurred sparsely at the start of the site investigations in 2002, but the population has increased at
an amazing rate during subsequent years, similar to many other parts of the country /­Truvé 2007/. In
total, 96 bird species have been found in the Forsmark area /­Green 2004/. The most common species
in Forsmark are, as in the rest of Sweden, Chaffinch and Willow Warbler.
A conceptual model of important fluxes

Ecosystem characteristics, such as biomass, net primary production, consumption and accumulationof soil organic matter, have been in focus because of their direct implication to food web transfer
and long-term accumulation of elements in the landscape. The largest carbon flux in terrestrial ecosystems is the uptake of carbon by primary producers. This net primary production creates a demandof a number of macro- and micronutrients that are incorporated into the biomass according to moreor less well-described stoichiometric relationships /­Sterner and Elser 2002/. Consequently, NPP will
set the upper limit to the potential uptake of different elements into biomass. In turn, this will set
limits to what extent further propagation up in the food web is possible. Biomass does eventuallyreach the soil compartment as litter, where it is mineralized. The balance between litter production
and heterotrophic respiration determines to what extent organic material (and incorporated elements)
may be accumulated in the soil.
Figure 5‑11 is a compilation of important processes that have been identified from the descriptionsof ecosystems at the site and from the interaction matrix (Chapter 4) for a mire ecosystem at a given
point in time. These ecosystem characteristics are further described for Forsmark in /­Löfgren 2010/.
TR-10-09

49

Sources
Residual

Sinks
Deposition

Accumulation in lakes

Discharge

Pb
Zn
Cd
Cu
Hg
Bi
Ag
Se
Ni
Nb
V
Ga
P
Cr
Be
I
Sb
W
Co
Th
N
Rb
As
Mn
Fe
Cl
Y
Sc
Zr
Na
Li
Mo
Sr
Ba
S
Br
K
Mg
Ca
Si
U
Al

Figure 5‑9. Relative element fluxes at the landscape level in the Forsmark area, based on a mass balance
model /­Tröjbom and Grolander 2010/. Exchange with the atmosphere is consistently treated as a source(i.e. atmospheric deposition). The major sinks are accumulation in lake sediments and discharge via
watercourses. The residual (i.e. the difference between the above mentioned fluxes) may either be positiveor negative. If positive, it represents the additional supply via weathering in the terrestrial system that isneeded to obtain balance (grey bar at the left side). A negative residual represents an additional sink in
the terrestrial system where elements supplied via atmospheric deposition are accumulated (grey bar at
the right side). Figure from /­Tröjbom and Grolander 2010/.

50

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Figure 5‑10. A wetland in Forsmark dominated by Reed (Phragmites australis).

consumption

uptakesorptiondesorption

consumption
uptakeption

consum

ow

infl

relea

se

gas
transport

uptakedecomp.

uptakeow

litterconsumption

infl

Figure 5‑11. A conceptual description of important fluxes affecting the transport and accumulation ofelements in a wetland ecosystem and in an arable land on a drained part of a mire, where the human
exposure in a safety assessment is in focus. Green arrows are fluxes mediated by biota, grey arrows arewater and gas fluxes, blue arrow represents sorption/desorption processes, consumption also includes water
for drinking. The mire was preceded by a lake and a marine stage in which gyttja/clay and postglacial clay
were deposited prior to the peat.

TR-10-0951

5.2.2Aquatic ecosystems

LimnicAll present-day lakes in the Forsmark area are small and shallow, and are characterised as oligotrophic
hardwater lakes /­Andersson 2010/. The shallow depths and relatively clear water of the lakes permit
photosynthesis in the entire benthic habitat of the lakes, and the bottoms are covered by dense standsof the macroalgae Chara sp. Moreover, many of the lakes also have a thick (>10 cm) microbial mat,consisting of cyanobacteria and diatoms, in the benthic habitat.
The large amounts of macroalgae and microphytobenthos give rise to high primary production in thebenthic habitat, whereas primary production in the water column is modest. Modelling of limnic ecosystems within SR-Site indicates that only minor parts of the primary produced carbon are consumedby other organisms and transported upwards in the food chain /­Andersson 2010/. Instead, much of
the produced carbon is circulated within the microbial food web and transferred back to abiotic poolsor sequestered in the sediment.
The fish community in the lakes is dominated by species resistant to low oxygen concentrations, mainly
due to poor oxygen conditions during the winter. As described above (Section 5.1.4), the streams in
Forsmark are all very small and long stretches of the streams are dry during summer (Figure 5‑12). The
downstream parts of some of the streams may function as passages for migrating fish, and extensive
spawning migration between the sea and a lake has been observed.

Figure 5‑12. Many of the small streams in the Forsmark area dry out during summer (photo from July 2003).

52

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MarineShallow waters, a subdued bathymetry and restricted light penetration characterise the marine ecosystems in Forsmark. Together, these factors result in high primary production in the near-shore zone,
were the highest biomasses and primary production are found. In deeper areas, where primary production is restricted to the pelagic zone, the production is lower. The marine system of the Forsmark area
is a relatively productive coastal zone in a region of otherwise fairly low primary production. This isdue to upwelling along the coast /­Eriksson et al. 1977/. Like in the rest of the Bothnian Sea, the faunaconsists of mixed freshwater and saltwater species. The benthic fauna occurs in the highest densities
in association with vegetation. In offshore areas, herring and sprat are the dominating fish species,
whereas perch and pike are the most common species in the inner bays /­Aquilonius 2010/.
Conceptual model of important fluxes in aquatic ecosystems

sum

resp

con

gas flux

ry
pri

ma

influxproddeposition

Both abiotic and biotic process influence transport and accumulation of elements in aquatic eco­systems
and are thus of interest in the safety assessment. Of the biotic processes identified in Chapter 4, primary
production, growth, death, consumption, uptake, excretion and particle release/trapping are the major
biotic processes that may affect the transfer and accumulation of elements in aquatic ecosystems(Figure 5‑13). In lakes, these processes often involve larger fluxes of matter than abiotic processes suchas convection (influx and outflux of matter via inlets and outlets). Advective flux (i.e. water turnover)is often the overall dominating factor affecting the transfer and accumulation of chemical elements inthe sea, especially in open and more offshore basins. In comparison, biotic processes are less important.
In general, the abiotic processes sedimentation, resuspension and sorption/desorption of radionuclides
to particles and sediments are important for the transport and accumulation of radionuclides in aquatic
ecosystems.

ptio

n

e
/up
tak
bioturbation

disc

harg

e

resuspension

mp

co
ns

co

sedimentation

de

cr
ex

mixingsorp/desorp

outflux

Figure 5‑13. A conceptual model of aquatic (i.e. both limnic and marine) ecosystem processes.

TR-10-0953

5.2.3 Human utilization of natural resources
Today, the Forsmark area has no permanent residents, but there are five holiday houses and three
farms situated within the area /­Miliander et al. 2004/. The only agricultural enterprise operating
today is situated at Storskäret. It is focused on meat production and the cattle graze outdoors during
the vegetation periods. The area used for agricultural purposes (pastures, meadows and fields) comprises 4% of the total area. The land use is dominated by forestry, and wood extraction is the only
significant outflow of biomass from the area. The dominant leisure activity is hunting. Besides this,the area is only occasionally used for leisure as a result of the small local population, the relative
inaccessibility of the locality and the distance from major urban areas. The area contains one large
industrial plant, the Forsmark nuclear power plant, with more than 700 employees. Besides these,
there are only a few work places within the area /­Miliander et al. 2004/.

54

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6

Site development

6.1

Main factors affecting site development

The long-term landscape development in the Forsmark area is determined by two main and partly
interdependent factors, climate variations and shoreline displacement. These two factors in combination affect a number of processes, which in turn determine the development of ecosystems. Some
examples of such processes are erosion and sedimentation, groundwater recharge and discharge, soil
formation, primary production, and decomposition of organic matter. The shoreline displacement
is mainly a secondary effect of climate variations. It is caused by the interplay between glaciallyinduced isostatic rebound on the one hand, and eustatic sea level variations (Section 3.3 in Climate
report). Periodically, shoreline displacement has strongly affected the Forsmark area, both before
and after the latest deglaciation, and it is likely that the area repeatedly has been situated below thesea level for long periods /­Chapter 3 in Söderbäck 2008/.
Many of the analyses of surface systems within SR-Site are focused on the development of today’s
landscape, influenced by the transgressing shoreline (Figure 6‑1) which divides the area into a submerged and a terrestrial part. The shoreline is of course a place of special attention since it is a highly
dynamic part of the landscape system. It is along the shoreline where coastal processes determine
the development; unconsolidated sediments are eroded and transported to deeper areas, waterborne
nutrients create a productive littoral zone were flooding regularly occurs, and much of the marine
primary production is concentrated to the shallow waters in the vicinity of the shoreline.
This coastal zone migrates continuously as a consequence of the isostatic rebound, which means that
traces of coastal processes ascend with the land and can be found higher up from the current shoreline. Furthermore, as soon as land emerges from the sea, other types of processes start to dominate
landscape development; terrestrial processes create a zonation as a consequence of exposure. Areason higher altitudes have been exposed to these transforming processes during a longer period thanhave areas at lower altitudes. For example, land higher up is more weathered, soil-forming processes
have created soils with a higher degree of maturity, and wetlands have accumulated more gyttja andpeat. Studies of these terrestrial environments in different successiv stages constituted a fundamental
part of the SR-Site surface systems programme. Lower lying land, i.e. of a younger terrestrial
age, is assumed to develop in the same direction as the older parts of the terrestrial landscape,and the development of older land higher up in the terrain is assumed to continue along the same
successional path until shifts in climate regimes are projected to alter the dominant processes oftransformation. Such a concept of “space-for-time substitution” is used in all disciplines of SR-Sitesurface systems as described in this chapter. It is applied to knowledge from the site investigations,but also in numerical models and studies of analogue areas currently experiencing climate regimes
different from today’s Forsmark.
Lakes, streams and wetlands are given special attention in the following sections because they are
the most likely recipients for potentially released radionuclides. This is because lakes, streams andwetlands often coincide with topographic depressions, which in turn are probable locations of deep
groundwater discharge reaching the surface /­Joyce et al. 2010/.

6.2

Long-term site development

The following sections (6.2.1 through 6.3.3) describe the long-term site development at Forsmark
based on the SR-Site reference glacial cycle (Section 4.5 in Climate report), which presupposes
the global climate system to be continuously characterised by repeated mid-latitude glaciations
interrupted by warmer periods in cycles of approximately 100,000 years (Section 6.2.1). Site development under prolonged global mean temperatures higher than those existing today is described in
Section 6.4, which is based on a development according to the SR-Site global warming climate case(Section 5.1 in Climate report).

TR-10-09

55

C

Time

B

A

Figure 6‑1. Potential development of a coastal area with two delineated sub-catchments (red solid andred dotted line, respectively) in east-central Sweden over approximately 800 years (A-C). Following theshoreline transgression, the smaller area (red dotted line) goes from being a shallow marine basin (A),to a lake-centred sub-catchment (B), and the subsequent expansion of reed belts in the littoral zone thentransforms the lake into a wetland (C).

6.2.1 Climate and climate-related processes
The SR-Site primary approach of handling the complex issue of future climates is by constructinga reference glacial cycle, which constitutes a repetition of the climate reconstructed for the latest
glacial cycle, in Europe called Weichsel, and the subsequent warm period, the Holocene (Climate
report). Covering a period of 120,000 years, the reference glacial cycle provides an example of how
climate and climate-related processes are likely to succeed during a future glacial cycle including
full glacial conditions, interrupted by several warmer periods (interstadials). The reference glacial
cycle gives input on timing, function and feedbacks of climate-related phenomena like ice sheets,
permafrost and shoreline displacement (­Climate report). In SR-Site, the reference glacial cycle
is complemented with additional climate cases with potentially larger impact on repository safety(Chapter 5 in Climate report).
56

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Figure 6‑2 shows how the climate develops at Forsmark in the reference glacial cycle, represented
by so called climate domains, i.e. areas dominated by certain climate related processes such as for
instance ice sheets and permafrost. For a motivation and full description of the climate domains(Chapter in Climate report). The Forsmark site is dominated by temperate climate domain (green)
for the first ~ 25 thousand years, although shorter periods of the periglacial climate domain (blue)
occur around 10 kyrs after present. Subsequently, up to the first period of glacial climate domain(white or light grey), temperate conditions are gradually replaced by periglacial conditions.
The trend with gradually more dominating periglacial conditions is a natural result of the progressively
colder climate during the first and major part of a glacial cycle (Section 4.5 in Climate report). This
progressively cooling trend during the glacial cycle also causes periods with glacial climate domain to
increase in length each time glacial conditions appear. The trend is not interrupted until the final deglaciation at the very end of the scenario, when ice-free conditions dominate again in a warm interglacial
climate.
At the time of the latest deglaciation of Forsmark around 8800 BC, which corresponds to the lastpart of the reference glacial cycle (Figure 6‑2), the area was covered by approximately 150 m ofglacio-lacustrine water /­Söderbäck 2008/ and the nearest shoreline was situated some 100 km westof Forsmark. Thereafter, the isostatic rebound has been continuous and slowly declining. The rateof rebound in Forsmark has decreased from c. 3.5 m/100 years directly after the deglaciation to apresent rate of c. 0.6 m/100 years, and it is predicted to decrease further to become insignificant
around 30,000 AD.
The global warming climate case describes a future climate development influenced by anthropogenic emissions of greenhouse gases and associated perturbations of the natural climate system(Section 6.4). These perturbations may cause the occurrence of air temperatures several degrees
warmer than present in central Sweden and Forsmark within the first hundreds to thousands ofyears after present (Section 5.1 in Climate report). Subsequently, following reduction in emissions,temperatures are envisaged to slowly decline for the rest of the long initial period with temperate
climate conditions.

Ice sheet thickness (m)3000
Climate domains
Temperate
Periglacial
Glacialbasal frozen
basal melting

2000

1000

Submerged
conditions

0

400
-100

300

-200

Permafrost depth
Frozen depth

200

Relative shore-level

100
0

-300

-100
0

10

20

30

40

50

60

70

80

90

100

110

120

Relative shore-level (m)Permafrost andfrozen depth (m)0Time (kyrs after present)

Figure 6‑2. Evolution of important climate-related variables at Forsmark for the coming 120 kyrs in the
SR-Site reference glacial cycle. Figure from Climate report.

TR-10-0957

6.2.2 Topography
The obvious glacial origin of dominating regolith and noticeable glacial erosion on exposed bedrock
have traditionally resulted in interpretations of ice sheets leaving a significant imprint on today’s
bedrock morphology in areas once covered by Quaternary glaciations. However, numerous studies
during recent decades have shown that glacial erosion under certain conditions may have been very
restricted (­Section 3.5 in Climate report, see also /Kleman and Hättestrand 1999/). Many areas,
Forsmark included, do show glacial sediments laid down during the latest glaciation, but even inthese cases a likely explanation is that these sediments primarily consist of early Quaternary sediments reworked during several subsequent glaciations /­Kleman et al. 2008/. In south central Sweden,
including the Forsmark site, the accumulated amount of bedrock erosion from all Quaternary glaciations is likely less than some 10 metres on average /­Lidmar-Bergström 1996/.
Considering the bedrock topography in Forsmark to have been fairly stable throughout Quaternary
glaciations, there is no reason to believe that future glaciations would leave a significantly different
imprint on the bedrock topography /­Olvmo 2010/. The future denudation (all erosion and weathering
combined) in Forsmark has been estimated to 1–2.6 metres for the coming c. 100,000 years and between
8–21 metres for the coming 1 million years (Section 3.5 in Climate report). The landscape that will
emerge from a vanishing future ice sheet will not be exactly the same as the landscape we know from
Forsmark today, but it will most probably show a similar pattern of glacial sediments and minor bedrockbasins occupied by lakes. We assume a future deglaciated landscape to include all relevant processes andfeatures we know from today and the surface system to function in a similar manner.

6.2.3 Regolith
Similar to many other areas covered by Late Quaternary glaciations, Forsmark experienced a complete
redistribution and reshaping of unconsolidated deposits during the latest glaciation. Since then, muchof the fine-grained glacial sediment has been eroded and relocated to sedimentation basins, within or
outside the Forsmark area. Postglacial redistribution of fine-grained material is a continuous process,even though the locations of maximum erosion (primarily by waves in exposed shallow waters) andaccumulation migrate as a consequence of a transgressing shoreline.
Postglacial redistribution also occurs on land, where material is transported and settles as sedimentin lakes and shallow marine embayments. Growth and decomposition of plants gives rise to organic
material in the form of gyttja and peat, further infilling lakes and marine embayments. The ongoing
isostatic uplift results in the emergence of new land areas, transforming the coastal basins to shelteredpositions that favour the accumulation of clay gyttja and gyttja. Gyttja is formed in lakes and consists
mainly of remnants from plants that had grown in the lake. Many of the present and future ponds andlakes in Forsmark are very shallow, often less than 1 m water depth at the deepest, and will have only
a short duration as a lake/pond before the basin is infilled and developed into a wetland. In several of
the present-day small wetlands, the lacustrine sediments, representing the lake stage of the basin, aremissing and peat is formed directly on the marine sediments or till.
The above general description implies that processes controlling regolith distribution are essentiallydifferent during glacial and non-glacial periods; glaciations giving a new set of regolith units, partly
redistributed during non-glacial periods, with the addition of organic material during non-glacial
periods. SR-Site primarily handles the future redistribution of regolith during non-glacial periods
by applying the coupled regolith-lake development model (RLDM) /­Brydsten and Strömgren 2010/.
This model is divided into a marine module that predicts the sediment dynamics caused by waves,and a lake module that predicts infilling of lakes. The model forecasts regolith distribution and thickness of different strata at time-steps of 500 years (marine stage) or 100 years (lake stage) from 9000
BC until the sea has withdrawn from the model area (c. 30,000 AD).
The marine module of the model runs from the time when the area has recently been deglaciated atabout 8800 BC until 11,500 AD. Inputs to the model are site description data on the current surface
distribution of regolith /­Hedenström and Sohlenius 2008/ and the regolith depth model (RDM) thatshows the stratigraphy and thickness of different sediments /­Hedenström et al. 2008/.
Lakes are modelled individually with a module based on equations for net sedimentation rate andvegetation colonisation /­Brydsten 2006/. The lake module gives the distribution of regolith, surface
elevation and thickness of the marine and limnic postglacial deposits in each time step until the lake
is totally infilled.
58

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The RLDM suggests that a major part of the study area was covered by postglacial clay shortly after
the area was deglaciated. As the water got shallower following isostatic rebound, much of the postglacial clay was resuspended and exposed glacial sediments underneath. According to the RLDM,
the minimum areal extension of postglacial clay occurred at about 2000 BC, mainly in today’s
marine basin Gräsörännan west of the Gräsö Island. Postglacial clay extension increases during
the following period, and reaches a local maximum around 2500 AD, and successively decreases
until the shoreline reaches a location outside the model area at about 11,500 AD. At that time, theregolith in the model area is, as in present-day conditions, dominated by till, but large areas of themore recently emerged parts are covered by glacial or postglacial clay (Figure 6‑3). According to the
RLDM, the maximum thickness of postglacial clay in the area (28.6 metres) will be found west of
Gräsö Island /­Brydsten and Strömgren 2010/.

6694000 6696000 6698000 6700000 6702000 6704000 6706000 6708000 6710000 6712000

6694000 6696000 6698000 6700000 6702000 6704000 6706000 6708000 6710000 6712000

D:\GIS\SR_Site\Bearbetad_data\Mxd_TR_10_09\Fig6-3.mxd

1622000 1624000 1626000 1628000 1630000 1632000 1634000 1636000 1638000 1640000 1642000 1644000 1646000 1648000

1622000 1624000 1626000 1628000 1630000 1632000 1634000 1636000 1638000 1640000 1642000 1644000 1646000 1648000

0

1

2

Precambrian bedrock

Artificial fill

Gyttja, Peat

Till

Postglacial clay

Lake

Glacial clay

Thin postglacial clay

Glacifluvial sediment

4 km

±

SKB/skbebo 2011-01-18 10:52
Bakgrundskartor © Lantmäteriet

Figure 6‑3. Surface distribution of regolith at 10,000 AD according to the Coupled regolith-lake development model /­Brydsten and Strömgren 2010/. Most of the postglacial clay is eroded and transported out of
the area. The only larger remaining area of postglacial clay is in the former marine basin Gräsörännan, inthe north-central part of the figure. Figure from /­Brydsten and Strömgren 2010/.

TR-10-0959

6.2.4 Surface hydrology
Hydrological processes play a substantial role in the development of surface systems, primarily by
regulating the availability of water for biomass production and by the role of water as a medium
for transport of particles and dissolved substances. Since surface hydrology is highly dependent on
climate, we can anticipate substantial changes in altered climate domains during a glacial cycle.
By using conceptual knowledge and output from hydrological modelling performed within the site
description /­Bosson et al. 2008/ as a starting point, numerical models describing present and future
conditions have been developed and applied in order to answer questions about the future hydrology
in Forsmark /­Bosson et al. 2010/.
Modelling of future hydrology has been conducted both on a regional spatial scale and on a local
scale for two selected sub-catchments. The models were run for different time-slices (2000, 5000 and
10,000 AD) and with input data representing different climate conditions, i.e. a normal temperate climate (based on measured data from the Forsmark area), a temperate climate with increased precipitation (referred to as “wet climate”) and a periglacial climate with lower temperatures and permafrost.
The three time-slices differ in shoreline position, in the distribution of regolith and vegetation (basedon information from the RLDM /­Brydsten and Strömgren 2010, Löfgren 2010, Section 6.2.3/).
According to the model results, water balance does not change dramatically during continuous
temperate climate at Forsmark. The change of internal distribution of the precipitated water will
not exceed 10% of the present water balance at the site, but changes in water balances will be
more pronounced during other climate domains. A larger amount of water will contribute to runoff
during times characterised by wet conditions, with a faster turnover time as a result. In a periglacial
climate regime, infiltration is strongly reduced because of perennially frozen ground, causing large
annual variations in hydrological characteristics, since water turnover takes place during a restricted
summer season.
The overall pattern of recharge and discharge areas does not change when prolonging a temperate
climate to the studied future periods, which confirms that the flow gradient is more dependent
on topography than on the distribution of regolith or distance to the shore. However, the results
show that regolith stratigraphy and thickness may influence the local distribution of recharge anddischarge areas in the near-surface system. Since most of the discharge areas for deep groundwater
are concentrated to low-elevation points in the landscape, the distribution of the regolith in theseareas can cause local deviations in transport of dissolved substances and particles.
Permafrost has a profound effect on patterns of recharge and discharge in the landscape /­Vidstrand
et al. 2010/. This is because vertical exchange of groundwater under permafrost conditions is con­centrated to areas were thawed conditions prevail from the ground surface all the way down to theunfrozen conditions that underlie the permafrost. These through taliks generally occur under lakes
and are encased by permafrost on the sides (Section 3.4 in Climate report). Some taliks act asrecharge areas and some as discharge areas. Thus, the flow paths from a repository in a periglacial
climate domain will deviate from flow paths developed under present climate conditions. Many of
the areas likely to be taliks are discharge areas also under present conditions, but the funnelling offlow in through taliks might lead to higher concentrations of transported substances where discharge
reaches the surface in a periglacial environment /­Bosson et al. 2010/.

6.2.5 Coastal oceanography
Of profound importance to marine environment development in Forsmark is the interplay between
glacially induced isostatic depression/recovery and eustatic sea level variations. This interplay gives
changing local water depths and residence times as well as changing regional circulation and salinityof water bodies in the Baltic basin. Today, the Baltic Sea is a brackish sea with substantial input offreshwater and restricted inflow of saline water via narrow and shallow straits connecting the Baltic
Sea to the Atlantic. Isostacy of the straits is today relatively stable and the height of the thresholds
will only marginally affect the future salinity of the Baltic Sea /­Gustafsson 2004a, b/.
In contrast, isostatic rebound in central and northern Sweden is significant. The Southern Kvark sill
is characterised by a maximum water depth of 40 metres and isostatic rebound of about 5 mm per
year /­Ekman 1996/, which implies large changes in the exchange of water between the Bothnian Sea
and the Baltic Proper within the next few millennia /­Gustafsson 2004a, b/. Isostatic rebound is mostevident even on the local scale. Even though the process is fast enough to make a noticeable difference during a generation, it takes time to complete. It takes about 12,000 years to transfer the entire
Forsmark area from fully submerged from just before the first islet emerges above the sea surface(1000 BC), until the last marine embayment is turned into a lake (11,000 AD).
60

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The description of coastal oceanography within SR-Site has focused on hydraulic residence time,
because of its importance for transfer and accumulation of radionuclides. According to /­Brydsten
2006/, the local development can be divided into three stages; an open sea stage, an open-ended
coastal stage (as the present stage) and a bay stage with only one open boundary. These stages
will appear in the above mentioned order following deglaciation over the subsequent roughly
15,000 years. Using the shoreline displacement equation /­Brydsten 2006/ as input, /­Karlsson et al.
2010/ conducted detailed hydrodynamic modelling of marine basins in the Forsmark area. The
hydrodynamic model gives outputs of annual mean flows between adjacent basins and a measure of
the water retention time for each basin and for the whole area. For the open sea stage, the circulation
was simulated using a model for the entire Baltic Sea. For the other two stages, a high-resolution
local model was set up for the near-coastal basin Öregrundsgrepen.
During the open sea stage the water turnover will be rapid and similar in the whole model area andin the open Baltic Sea. Oceanographic conditions will be fairly homogenous and the water exchange
is at its maximum. In the open-ended coastal stage a net through-flow of the area is still possible,
although the water retention time increases as a result of a complex interplay between a narrowersouthern boundary, decreasing volumes of the marine basins and decreasing of the cross-sectional
areas between adjacent basins. The water turnover during this stage is primarily determined by
the wind and fluctuating sea levels, and water retention times will be longest in the shallow basinslocated far from the boundaries to the Baltic Sea. During the bay stage, the southern entrance has
closed and Öregrundsgrepen has been transformed into a bay, whereby the water retention time forthe whole area increases. The oceanographic conditions will be typical for estuarine circulation in
an enclosed bay. The basins gradually become more enclosed and are one by one transformed intolakes. Runoff from land becomes more important for water turnover during this stage and wind still
plays an important role.

6.2.6 Chemistry
The chemistry observed in the Forsmark area today is a consequence of past landscape development,
present and historic land use, and anthropogenic inputs. The ongoing shoreline regression createsa spatial gradient from the coast in an inland direction, which represents a timeline in landscapematurity. This means that the spatial gradient of today may be extrapolated and translated into a
succession of landscape maturation for the future. The present chemical conditions found in themodelled area in Forsmark therefore represent a historic time span of about 10,000 years since thelast deglaciation. In Figure 6‑4 this is illustrated as a box moving over time from the sea-bottom
environment to the terrestrial environment, although the illustration is somewhat limited by the factthat climate, vegetation cover and anthropogenic influence via e.g. atmospheric deposition and land
use have varied during the period.
Meteoric
recharge

Terrestial
ecosystem
Water (fresh – salt – brackish)sits
ary depo
Quatern

Bedrock

Figure 6‑4. A hypothetical cross-section of the Forsmark area today, illustrating the spatial gradient thatcan be extrapolated and translated into a succession of landscape maturation for the future. The left box
may represent the conditions soon after the deglaciation (8800 BC), whereas the right box represents conditions in the most elevated parts of the area, which have been exposed to meteoric recharge and chemical
weathering for several thousands of years. Figure from /­Tröjbom and Grolander 2010/.

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The historical development of the chemistry in the surface system at Forsmark can be divided
into four stages, based on differing hydrological conditions: (1) Deglaciation of exposed glacial
sediments, submerged by the freshwater Baltic Ice Lake. These deposits contained large amountsof limestone. (2) Freshwater conditions were replaced by the brackish Littorina Sea, with increasing
salinity, where density turnover infiltrated sea water through the underlying sediments. (3) Close to
the emerging coast when a shallow sea still covered the area, the topographical discharge gradient
may have transported traces of deep groundwater into glacial and post-glacial deposits. (4) As soon
as land emerged, recharge of meteoric water created new hydrological flow patterns recharging
through the regolith and discharging in streams and lakes. At this stage, aeration by meteoric
recharge, in combination with a supply of organic carbon, altered redox conditions in the shallow
groundwater. Increased supply of H+ ions, mainly supplied through decomposition of organic matter,is the ultimate driving force for weathering reactions that take place in the regolith and bedrock.
Most of the easily weathered calcite in the upper regolith will be dissolved and washed out within aperiod of some thousands of years /­Tröjbom and Grolander 2010/. This means that the strong influence of the calcium-rich deposits on the terrestrial and limnic ecosystems will be reduced over time.
For instance, the oligotrophic hardwater lakes that are characteristic for the coastal area in Forsmark
will likely be transformed to more dystrophic (low pH, brown-water) and nutrient-rich conditions
within some thousands of years after isolation from the sea, if they have not been turned into wetlands
before this /­Andersson 2010/.
The part of the Forsmark area currently submerged by the sea has larger areas of clay than thecurrently emerged part, which is dominated by till /­Hedenström and Sohlenius 2008/. This implies
that weathering rates and area-specific discharge of different elements will increase with a lowering
shore-level. This is especially the case if these areas are drained and cultivated in a way similar tocomparable land areas in the region today. Area-specific losses of e.g. phosphorus are at least anorder of magnitude larger for arable land than for forest land /­Tröjbom et al. 2007/, and a greater
proportion of arable land could significantly increase the nutrient status and primary production in
the freshwater recipients.

6.2.7 Ecosystems
The costal setting of Forsmark supports a large number of diversified ecosystems, such as shallow
marine basins with protruding islets, mixed forests with interspersed grasslands and cultivated fields,
and freshwater lakes in different stages of succession towards wetlands. The location along a coast
characterised by isostatic rebound also makes the distribution of ecosystems highly dynamic; a shoreline
regressing at a speed of about 6 mm/year /­Ekman 1996/ transforms marine ecosystems into limnic andsubsequently to terrestrial ecosystems. Development continues as terrestrial sites are elevated to higher
ground and successional processes reorganize both the habitat and the species pool. Successional paths
can change into new directions with shifts in climate or human utilisation of the area.
All these environments and their possible development are extensively described in three SR-Siteecosystem reports covering the marine /­Aquilonius 2010/, limnic /­Andersson 2010/, and terrestrial/­Löfgren 2010/ ecosystems. Modelling of potential climate extremes has made it possible to make asketch of the boundaries that would set the limits to what ecosystems that might occur. Output fromsuch modelling has also been used as input to vegetation modelling in order to describe the vegetation during a prevailing climate /­Kjellström et al. 2009/.
As the sea bottom is elevated by the isostatic rebound, deeper off-shore areas become shallow coastal
areas. Water turnover becomes slower as a consequence of shallower water and a more secluded
position. The marine ecosystem will transform from being net heterotrophic and dominated by pelagic
primary production towards a primarily benthic and in general autotrophic ecosystem. A bay turns intoa lake ecosystem after isolation from the sea, and gradually matures in an ontogenetic process, including sedimentation in combination with mire growth from the lake edges.
In Forsmark, all present-day lakes have developed into oligotrophic hardwater lakes with high primary production at the sediment surface. The subsequent development into wetland is dominated by
the ingrowth of littoral plants and by a gradual infilling with allocthonous sediments. Some stages inpeatland development might include sedges, mosses, or flood tolerant trees like pine, birch or alder/­Fredriksson 2004/. The richer types of mires, which are typical of the Forsmark area, will undergo anatural long-term acidification when turning into more bog-like mires. A stylised illustration of this
temporal development is shown in Figure 6‑5.
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Bog

Agricultural land

Lake/Mire

ForestLake
Semi-enclosed bay

Sea

Figure 6‑5. A schematic illustration of the major ecosystems that may be found during a temporal sequence,
where the original sea bottom develops to a lake or a terrestrial ecosystem. Black arrows indicate natural
succession, whereas grey arrows indicate human-induced changes. Agricultural land may be abandoned anddevelop into forest or, if the hydrological conditions are suitable, into a fen. Figure from /­Söderbäck 2008/.

Biotic processes will be restricted by a shorter vegetation period during a periglacial climate domain
and, consequently, this will lead to lower biomasses and net primary production in both forested taiga
and tundra peatlands /­Gower et al. 2001, Wielgolaski et al. 1981/. In aquatic ecosystems, the biomassof primary producers is not necessarily lower in periglacial conditions, since periglacial lakes often
contain large amounts of macrophytes, microbial algae and mosses, which are less affected by a shorter
vegetation period, and lower temperatures in the sea may increase the upwelling of deep nutrient-richwater and thereby alter the production. Biomass and production of higher biota do, however, most
likely decrease in aquatic ecosystems under periglacial conditions.

6.2.8 Human utilisation of natural resources
The possibility for future agriculture in Forsmark was studied in /­Lindborg 2010/ by classifying theavailability of arable land from maps of Quaternary deposits /­Hedenström and Sohlenius 2008/ andfrom the output of the RLDM /­Brydsten and Strömgren 2010/, thus giving availability in time steps
until 35,000 AD. The classification of land as arable was done by using current regional agriculture
practices as a reference. Cultivation in Uppsala County today is mainly occurring on areas with glacialand postglacial clay and sand. Only a small fraction of the cultivated land is situated in areas with peat
and till. The limited cultivation of peatlands is because peat decomposes and subsides quickly whendrained and cultivated, thus making agriculture possible only for a few tens of years /­Section 4.3 in
Lindborg 2010/.

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Parts of the currently submerged land consists of regolith with a high content of stones and boulders, andis therefore unsuitable for farming even after being elevated to a terrestrial position. There are, however,large areas with fine-grained sediments that potentially may be cultivated (see the north-eastern half of
Figure 6‑6c below). Since the proportion of land that it is possible to cultivate will increase as new land
areas are formed, this means that the potential food productivity in the total area is expected to increaseduring the period up to 10,000 AD.

6.3

Site development during the reference glacial cycle

According to the regulations, the assessment has to be subdivided into several time periods (Chapter 3).
To provide a forecast of what will happen in the future is an impossible task and is not the intentionof the safety assessment. The intention is instead to provide a range of likely scenarios or variants ofpotential future conditions, based on available scientific knowledge, and to examine the effects of apotential release of radionuclides from a repository on humans and other biota under these scenarios
or variants. In this section, available knowledge of the present-day properties of the site, and of theprocesses affecting its future changes, is used in a scientific coherent way to describe a possible andlikely development of the site during the reference glacial cycle.
As a combined effect of the ongoing shoreline displacement, redistribution of marine sediments,
infilling of lakes and climate variations, the landscape properties and features will continuously
change in predictable ways. By combining information from the contemporary DEM /­Strömgren
and Brydsten 2008/ with the shoreline displacement in the reference glacial cycle (Section 4.5 inClimate report), output from the RLDM /­Brydsten and Strömgren 2010/ (Section 6.2.3) and biotic
information from the ecosystem modelling, a landscape development model that describes the longterm development of the site at the landscape level has been developed.
The landscape development model produces a description over time in spatial detail (20 m · 20 m)of landscape properties and features, including topography, location of the shoreline, regolith depth,
areas and depths of present and future lakes and sea basins, stream network, and vegetation and landuse. This description can in turn be used to extract time-dependent properties of the biosphere objects(Chapter 7) that are input parameters to the radionuclide model that is presented in Chapter 8.
Below follows a short description of the development of the Forsmark site, from present-day andover the complete reference glacial cycle. During the initial period of temperate climate domain, i.e.
until c. 10,000 AD, the landscape is highly dynamic due to the moving shoreline and the infilling oflakes, and the description during this period is based mainly on output from the landscape development model. Thereafter, and until the onset of the next glacial loading, the landscape development
will be more static and the succession will be determined mainly by climate variations.

6.3.1 Site development during the initial 1,000 years after repository closure
The shoreline displacement, measured as relative sea water-level, is projected to be nearly 6 mduring the next 1,000 years, assuming an almost constant isostatic rebound rate of 6 mm/year/­Ekman 1996, Hedenström and Risberg 2003/ and a constant absolute sea level. Based on this
scenario, a likely development of the site is described below.
The shoreline displacement will result in a horizontal transfer of the coastline to a location c. 1 km
east of the repository at 3000 AD, which means that parts of the present seafloor will become land.
Also, some of the coastal bays will be isolated and transformed to lakes (see Figure 6‑6a). The ongoing
shoreline regression causes a succession pattern, where the shore vegetation, dominated by herbs,
sedges and grasses, will be replaced by forest vegetation. The types of dominant vegetation communities during this succession are mainly determined by the composition of the underlying Quaternary
deposits, which, in turn, depend on the extent of previous wave exposure of the shallow coast.
All present-day lakes in the Forsmark area are small and shallow. This means that large parts of thelakes will be transformed to wetland during the coming 1,000 years /­Brydsten and Strömgren 2010/.
For example, two of the smaller lakes, Lake Puttan and Norra Bassängen, situated close to the planned
repository, are expected to be almost completely transformed to wetland, whereas a minor part of thelarger Lake Bolundsfjärden will continue to be open water in the year 3000 AD (see Appendix 1 fora map of the Forsmark area today).
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a)

b)

c)

Figure 6‑6. Modelled distribution of different vegetation types and of arable land in Forsmark at a) 3000 AD,b) 5000 AD and c) 10,000 AD. All areas that potentially can be cultivated are represented on the map asarable land /­Chapter 4 in Lindborg 2010/. The present shoreline is marked as a black line and darker shadesof blue represent deeper sea. Figure from /­Lindborg 2010/.

The man-made, deep inlet canal for cooling water to the nuclear power plants, situated immediately
north of the planned repository, will be isolated from the sea around 2500 AD /­Lindborg 2010/.
If it is left unaltered after decommissioning of the power plants, it will probably remain as a lake
far beyond the initial 1,000 years. Moreover, two new, relatively large lakes situated north of therepository and west of the present “Biotest basin”, will be isolated from the sea in the latter part ofthe period.
As the seafloor close to the coast gets shallower, erosion will occur on wave-exposed bottoms. Somesheltered areas inside a developing, denser archipelago will show accumulation for a short period/­Brydsten 2009/. The circulation in Öregrundsgrepen is expected to remain essentially the sameas today /­Karlsson et al. 2010/. The salinity of the Bothnian Sea is expected to decrease slightly
to around 4.8‰ during the initial 1,000 years, assuming unaltered runoff to the Bothnian Sea/­Gustafsson 2004a/.

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The potential for sustainable human exploitation of food resources in the area over the coming 1,000
years is not expected to differ much from the situation today. Only minor parts of the newly formed
land will have the potential for cultivation due to the boulder-rich sediments in the former sea andlake areas, but also due to problems with draining the low-elevation new areas /­Lindborg 2010/. New
areas will, however, be available for grazing by livestock.
The potential water supply for humans is expected to be fairly unaltered during this period. In the
future, the deep canal north of the repository has potential as a freshwater reservoir when the salinity
decreases, and also the stream through Bolundsfjärden may potentially be used for freshwater supply.
New wells may be drilled in the bedrock or dug in the regolith in the area which is land today, whereas
the new land will be too young for wells if current practises are sustained /­Kautsky 2001/.
In summary, the biosphere at the site during the next 1,000 years is assumed to be quite similar
to the present situation. The most important changes are the natural infilling of lakes and a slightwithdrawal of the sea with its effects on the near-shore areas and the shallow coastal basins.

6.3.2

Site development until the end of the initial period of a temperate
climate domain
During the initial period of a temperate climate domain, the regressive shoreline displacement isassumed to continue, but at a gradually declining rate (Section 4.5 in Climate report, see also
/Lindborg 2010/). Initially, the coastline will be subjected to a horizontal transfer of approximately
1 km per 1,000 years. This will strongly influence the landscape, especially during the first partof the period, and eventually it will result in a situation where the planned repository will have an
inland rather than a coastal setting (Figure 6‑6c).
The strait at Öregrund, south of the modelled area, is expected to be cut off about 3000 AD, andÖregrundsgrepen will turn into a bay. This will affect the water circulation, and due to the continued
narrowing of the bay, the water turnover will be further restricted /­Karlsson et al. 2010, Engqvist andAndrejev 2000/. During the period from 3000 to 5000 AD, a semi-enclosed archipelago is expected
to develop northeast of the repository. Around 5000 AD, many straits in this archipelago will close
and a number of lakes will be isolated from the sea.
At 5000 AD, the coastline has withdrawn c. 5 km from the repository. A small stream drains the area
above the repository, and some small and shallow lakes are expected to be situated along the stream.
This small stream will join a large stream to the south-east at about 5000 AD. The large stream consists of the upstream joined Forsmarksån and Olandsån, draining a large part of Northern Uppland(drainage area 1.3·103 km2). During the period from 3000 AD to 10,000 AD, the Öregrundsgrepen
bay gradually shrinks to finally form a short and narrow bay along the island of Gräsö (Figure 6‑6c).
In the modelled area, a large number of lakes will be isolated from the sea during the period from3000 AD to 10,000 AD. Most of the new lakes are small and shallow, and are expected to be infilled
and transformed into mires within a period of 2,000 to 6,000 years /­Brydsten and Strömgren 2010/.
Around 10,000 AD, almost all lakes in the area have been infilled and only some initially relatively
large and deep lakes near the Gräsö Island are expected to remain (Figure 6‑6c).
The salinity of the sea will continuously decrease due to the isostatic rebound of the shallow sills atÅland between the Bothnian Sea and the Baltic Proper. Around 6000 AD, the salinity is expected
to have decreased to 3–4‰, which means that an ecosystem similar to that in the Northern Kvark
today, with lower abundance of marine species and higher of freshwater species, will develop.
According to /­Brydsten 2009/, accumulation of sediments may occur both on bottoms at large water
depths and on shallow bottoms that are sheltered from wave exposure inside a belt of skerries. Erosion
occurs mainly on shallow bottoms exposed to waves. Transport bottoms can be found in all places
between these two extremes, i.e. at intermediate depths with moderate wave exposure. This means thatthe seafloor in the model area will show a characteristic evolution over time, beginning with a periodof accumulation due to large water depth early after deglaciation. Then comes a period with transport,
after which erosion dominates when the water depth decreases even more. Finally, transport and accumulation may occur in sheltered locations during a short period before the sea bottom becomes land.
This means that there are very limited parts of the model area that will show continuous accumulation

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of sediments throughout the whole marine period. The small areas that potentially may show continuous accumulation since the latest deglaciation are situated in the deepest parts of Öregrundsgrepen/­Brydsten and Strömgren 2010/.
Much of the newly formed land will be unsuitable for farming due to boulder- and stone-rich deposits/­Lindborg 2010/, but there are large areas currently submerged in central Öregrundsgrepen with finegrained sediments that will be possible to cultivate when exposed on land. Also patches of organicsoils on previous lakes/mires may be cultivated, but presumably these soils can be sustainably utilised
only for limited periods since compression and oxidation of the organic material will lower the groundsurface and cause problems with drainage /­Lindborg 2010/.
The food productivity in agricultural areas is several hundred times higher than that in aquatic or noncultivated terrestrial areas /­Andersson 2010, Aquilonius 2010, Löfgren 2010/. Since the proportions ofland possible to cultivate will increase as new land areas are formed, this means that the potential foodproductivity in the total modelled area is expected to increase during the period. However, the numberof people that potentially can be sustained by food produced within the Forsmark area is strongly
dependent on the degree to which land is used for farming.
The availability of freshwater for human supply is expected to gradually increase. As mentioned above,new lakes and streams will form. These will probably resemble the present-day lakes and streams, andmost of the lakes will be short-lived due to their shallowness. New groundwater, potentially usefulas drinking water, will be available when the shoreline moves eastwards. Among existing geologicalformations, the Börstilåsen esker, situated approximately 4 km southeast of the planned repository,
may provide groundwater of drinking-water quality, but there are no indications in the hydrogeologicalmodelling results that this aquifer will have contact with discharging groundwater from the repository/­Joyce et al. 2010/.

6.3.3

Site development during the remaining part of the reference
glacial cycle
As described in Section 6.2.1, SR-Site uses a reconstruction of the last glacial cycle to give one example of possible future changes in climate and climate-related processes. This reconstruction covers, ina realistic way, all relevant climate-related changes that can be expected in a 120,000-year perspective(Climate report). The reconstruction divides the period into distinct climate domains, but in reality
when looking at the entire modelled area at Forsmark, changeover from one climate domain to anotheris a smooth transition (Section 4.4.4 in Climate report). In addition, it takes time for the environment
and its predominant processes to adapt to an abrupt change in climate /­Chapter 3 in Lindborg 2010/.
For the modelled area at Forsmark it obviously takes time for a change in environmental conditions topropagate from one end to the other. For instance, this is true for the changeover after the deglaciation,from submerged conditions to an entirely terrestrial and temperate domain. This transition is causedby shoreline displacement, which takes 12,000 years to transfer the whole area from fully submerged
just before the first islet emerges from the sea (1000 BC), until the last marine embayment is turned
into a lake (around 11,000 AD). During two periods in the later part of the reference evolution,
Forsmark is covered by an ice sheet (Figure 6‑2). The site will be submerged by water directly after
deglaciation and thereafter the transfer from submerged conditions to an entirely terrestrial area isassumed to be repeated. For further descriptions of transitions between climate domains (Section 4.5
in Climate report).
Temperate climate domain

The temperate climate domain corresponds to 26% of the reference glacial cycle. After the initial
temperate period, which according to the reference glacial cycle ends around 9400 AD, a relative
short period of periglacial conditions will follow, and thereafter temperate conditions will dominate
again until c. 23,000 AD. Another temperate period that will last for about 5,000 years occurs around
40,000 AD.

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During future periods of temperate conditions before the next glaciation, Forsmark is assumed toshow biosphere characteristics similar to those of the later parts of the initial temperate period, i.e. thelandscape will consist of terrestrial ecosystems, mainly forests and mires, with few or no lakes and nosea. Parts of the area, especially those with fine-grained sediments in central Öregrundsgrepen, canpotentially be used for long-term agriculture (Figure 6‑6c). Patches with mainly organic soils may also
be cultivated for restriced periods. Higher altitude areas with outcrops of bedrock will likely be forested
with pine. Also the pattern for discharge of deep groundwater, as well as the conditions determining
transport and accumulation of radionuclides in the landscape, are expected to be similar to thoseprevailing during the late part of the initial temperate period /­Chapter 4 and 5 in Lindborg 2010/.
Periglacial climate domain

Periods of periglacial conditions, which are characterised by tundra vegetation and permafrost features,
correspond to 34% of the reference glacial cycle. Although the periglacial domain constitutes the largest proportion of the reference glacial cycle, it often occurs during relatively short periods interrupted
by other climate domains. The longest uninterrupted period of periglacial conditions starts around23,000 AD and continues for another 10,000 years. Below follows a generalised description of conditions during the periglacial climate domain. It should, however, be noted that the conditions may varyconsiderably within this climate domain, from a situation not very different from temperate conditions
but with shallow permafrost, to a harsh arctic climate with deep permafrost and very sparse vegetation.
The annual vegetation period of the periglacial domain is short. Nevertheless, primary production
may be high in some environments, e.g. in shallow lakes /­Andersson 2010/. The terrestrial vegetation consists of sedges, herbs and shrubs. At more exposed and dryer localities lichens dominate,
whereas vegetation on wet ground is dominated by mosses. The precipitation will typically be lower
than during temperate conditions, due to the limited evapotranspiration transporting water to theatmosphere, exemplified for periglacial conditions at Forsmark in /­Kjellström et al. 2009/. The low
evapotranspiration means that wet ground is prevalent, because surplus water is unable to infiltrate
into the ground /­Bosson et al. 2010, French 2007/. This may result in larger areas of wetlands
compared with a temperate climate, but on the other hand the peat formation rate is lower, partly
because the terrestrial plant productivity is low.
Even on gentle slopes, the soil creeps downhill. Other processes typical of periglacial conditions
are upward migration of stones induced by freeze-thaw processes, so called cryoturbation, causing
tundra-polygons and thermokarst phenomena. Thus, there are many periglacial processes disturbing
the soil and also exposing it to erosion.
Taliks are unfrozen areas, often occurring under lakes or rivers in the permafrost region /­Hartikainen et al.
2010/. The talik features are the only spots in the periglacial landscape where radionuclides released fromthe repository can be transported up to the biosphere /­Bosson et al. 2010/. Given that lakes and streams
often are locations for human settlement and land use, taliks can potentially be locations where humans
during periglacial conditions are exposed to radionuclides released from a repository.
Glacial climate domain

Forsmark is covered by an ice sheet during 24% of the reference glacial cycle, mainly during its later
part. On the ice-surface, microbes, algae and some insects can exist. At the ice-margin, a productive
aquatic community may exist, which can sustain fish populations that may be exploited by humans andby animals living on the ice (e.g. birds, arctic foxes, polar bears) and in the sea (e.g. seals and whales).
Any larger vertebrates or humans living on the ice are likely to migrate over large areas due to low foodproduction and severe weather conditions. In most cases, a human population will probably compriseoccasional visitors, due to the harsh environment. The only situation under glacial conditions whenhumans or other biota may be exposed to high concentrations of radionuclides from the repository iswhen the retreating ice-front is situated near the Forsmark area and the area is submerged. Under these
conditions, it is possible that a human population could be present for longer periods and live on fish
taken from close to the ice margin.

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Submerged conditions

In the reference glacial cycle, two periods of submerged conditions at Forsmark are present, representing 16% of the total reference glacial cycle. These periods always follow directly after the ice sheet
has withdrawn as a result of the bedrock being depressed by the ice load. After the last glaciation
which ended at 8800 BC in Forsmark, the first terrestrial areas appeared around 1000 BC and thelast marine embayment in the modelled area is turned into a lake around 11,000 AD. This means thatthe submerged conditions in the modelled area may be divided into two phases; one first phase of c.
8,000 years when the whole area is submerged, and another that continues for a further 12,000 years
when the sea gradually withdraws and the land area expands accordingly. This description of the temporal succession is not seen in the description in the reference glacial cycle (Figure 6‑2) since the latteris valid specifically for a point above the repository target area, but it gives a more realistic picture of
the succession for the whole landscape (see also the section on transitions between climate domains in(Section 4.4.4 in Climate report).
Submerged conditions are not defined as a climate domain in SR-Site Climate report. Instead, it isa state when the processes and properties related to the marine conditions are dominant. The marine
ecosystem is not expected to change dramatically from today as a result of changes in climate, except
for the long-term variations in salinity and water depth. Therefore, the submerged future landscape isin SR-Site treated in the same way as the historical and present aquatic ecosystems at Forsmark, andthe prerequisites for transport and accumulation of radionuclides are assumed to be similar to those in
the present marine ecosystem.

6.4

Site development according to the SR-Site global warming
climate case

SR-Site handles the possibility of anthropogenic induced global warming by constructing a global
warming climate case (Climate report), describing a future climate development influenced by perturbations of the natural climate system. In this climate case, the perturbations are assumed to cause
air temperatures several degrees warmer than present in central Sweden within the first hundreds tothousands of years after present. Subsequently, following reductions in emissions, temperatures areenvisaged to slowly decline for the rest of the prolonged period with temperate climate conditions(Climate report).
The combined effect of greenhouse-gas emissions and exceptionally small amplitudes of solar insolation variations during the coming 100,000-year period /­Berger 1978/, may cause the present interglacial
to be exceptionally long /­Berger and Loutre 2002/. The global warming climate case follows the
proposition by /­Berger and Loutre 2002/, and extends the initial period of temperate climate domain by
50,000 years compared with the reference glacial cycle (Section 6.2.1). After this initial 50,000 years oftemperate conditions, the global warming climate case follows the same pattern as the reference glacial
cycle and the corresponding first period of periglacial domain will occur in about 58 kyrs from now.
Consequently, the climate-related processes will be identical in the two climate cases, but displaced by
50,000 years.
As exemplified in the global and regional climate modelling performed by /­Kjellström et al. 2009/,
a global warming climate may result in the Forsmark region experiencing a mean annual air temperature increase of ~3.5°C and an increase in mean annual precipitation by ~20% as compared withthe climate during 1961–2000, which is chosen as reference period in the study by /­Kjellström et al.
2009/. These conditions were modelled for a period a few thousand years after present, but similar
conditions could arise also within a few hundreds of years. The results by /­Kjellström et al. 2009/ arein line with several other climate model simulations assuming similar future atmospheric greenhousegas concentrations /­BIOCLIM 2003, Rummukainen 2003/.
An important question related to future global warming is changing sea level and shoreline position,
which may result from melting of present glaciers and ice sheets and from the thermal expansionof sea water. This is of particular importance for Forsmark, being an area of low relief in a coastal
position close to the Bothnian Sea. Contradictory predictions regarding the future of the Greenland
ice sheet in a warming climate /­Lindborg 2010/ have been taken into account in SR-Site by including
an assessment of the consequences of a melting ice sheet and its effect on sea level at Forsmark(Figure 6‑7). The global warming climate case is therefore designed to allow the Greenland ice sheet
to collapse and melt completely during the next thousand years.
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Relative shore-level (m)

500
400
300
200

Relative shore-level
Global warming case

100

Relative shore-levelreference glacial cycle

0
-100
0

10

20

30

40

50

60

70

80

90

100

110

120

Time (kyrs after present)

Figure 6‑7. Shore-level evolution at Forsmark for the reference glacial cycle (grey) and the global warming
climate case (green). Negative numbers indicate that the area is situated above the present sea level. Figure
from Climate report.

In the modelling, counterbalancing gravitational effects associated with the removal of the massof the Greenland ice sheet, combined with the local isostatic rebound that follows removal of
the Fennoscandian ice sheet, mean that isostatic changes compensates for the eustatic change at
Forsmark (Figure 6‑7), resulting in a continuation of the present shore-level displacement (Climate
report /Milne et al. 1999, Whitehouse 2009/). However, because of the large uncertainties related tothe amount of global sea level rise in a warming climate, Forsmark may experience, contrary to whatis shown in Figure 6‑7, a transgression and associated submerged conditions during the initial few
thousands of years, after which the isostatic component again dominates and results in regression.
Accordingly, also in the global warming climate case Forsmark will in the long run be situated above
sea level until the occurrence of a future Fennoscandian ice sheet (Climate report).

6.4.1 Ecosystems in a climate characterised by global warming/Kjellström et al. 2009/ modelled the development of terrestrial vegetation during conditions ofglobal warming and suggested that Forsmark will be dominated by broadleaved trees with larger
biomasses, but with net primary production similar to today. /­Craft et al. 2008/ showed that carbon
sequestration is negatively correlated to the mean annual air temperature for temperate freshwater
peatlands in the USA. A similar pattern has also been described from the former Soviet Union, where
accumulation of peat was found to increase during periods of colder conditions /­Gorham 1991/. Peat
production in peatlands is also a function of precipitation, and a higher temperature combined withincreased precipitation may result in periods of unchanged peat accumulation under warmer conditions. An increased temperature, with increased evapotranspiration, will likely lower the groundwatertable and increase the heterotrophic respiration. /­Strack et al. 2008/ suggested that dry peatland areas
such as bog hummocks and ridges will act as smaller sinks or sources of atmospheric carbon, whereas
wet zones will likely become greater sinks.
The effects of global warming on aquatic ecosystems are complex and difficult to predict. Manychanges in ecosystem properties may vary in both positive and negative directions, depending on acomplex set of feedbacks. Although several factors may lead to increased primary production, there arealso several factors that may lead to increased respiration, and a possible outcome of warmer conditions
is that net ecosystem production will remain almost the same or at least be included within the range ofvariation in present-day temperate conditions /­Andersson 2010, Aquilonius 2010/.

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7

Landscape model for radionuclide assessment

Temporal development of discharge areas of deep groundwater is analysed by hydrological models
in SR-Site. This approach has been possible by utilisation of extensive site data and systematisation documented processes. The concept builds upon a landscape model exploring dynamics of theenvironments during non-glacial conditions and screens out potential objects which can be affectedby deep groundwater discharge, potentially with radionuclides from the repository. The landscapedevelopment is based on a scientific coherent, temporal and spatial understanding of the landscapewhich is essential to provide robust estimates for the radionuclide model.
The landscape model delivers location, delimitation and development of biosphere objects, as well
as spatial interactions between neighbouring objects. This chapter summarises the methodology used
to link the geosphere models to the surface system and the results derived from the landscape model.
Specifically, the following sections present a summary of how the biosphere objects are identified byusing the groundwater modelling, together with a discussion on how object development in time isdescribed, using data from the landscape development model.
The discharge of deep groundwater in future landscapes is illustrated in Section 7.1, where also theanalysis of groundwater flow simulations used to identify biosphere objects is described. Section 7.2
summarises the modelling of near-surface hydrology and transport that was performed in order tosupport the landscape model. In Section 7.3, the biosphere objects are put together in the evolving
landscape. This gives an illustration on how the objects are linked to each other and how the object
configuration develops during non-glacial conditions. The input from the landscape development
model used to populate the biosphere objects is also described in Section 7.3, and the data used in
the radionuclide model obtained from the landscape model are explained. The chapter concludes
with a short description on application of the landscape model in different climate scenarios.

7.1

Discharge points

7.1.1 Modelling of deep groundwater discharge
The identification of deep groundwater discharge areas in the future Forsmark area is based on themodelling of flow paths from the repository to the ground surface /­Section 4.2 in Joyce et al. 2010/.
To locate potential discharge areas, the end positions of flow paths emerging at the surface in theparticle tracking simulations, so-called discharge points, were related to present and future featuresof the Forsmark landscape, such as lakes and shallow parts of the sea floor. According to /­Joyce
et al. 2010/, the discharge pattern is determined mainly by the local topography and the deterministic
deformation zones. The pattern does not vary significantly between model realizations. With few
exceptions, the discharge points form clusters in limited numbers. For the identification of discharge
areas, it was assumed that the locations of these groups indicate areas likely to be affected bydischarge of deep groundwater that could potentially be contaminated.
The location of discharge points in the Forsmark landscape shows that: 1) deep groundwater fromthe repository is primarily attracted to low points in the landscape, e.g. shallow parts of the sea,along the shoreline, and in lakes, streams and wetlands, 2) discharge areas covered by the sea tend
to be relatively large, whereas discharge areas above sea level are narrower and primarily locatedto lake basins (which may be infilled), 3) discharge areas are located in a limited number of basins/­Lindborg 2010/. Uncertainties in forecasted location of discharge points are discussed in /­Joyce
et al. 2010/. Transport in the near-surface and surface system is also compared with results from themore detailed MIKE SHE modelling (Section 7.2.2).
A number of discharge points are concentrated along the north-eastern boundary of the model
domain according to the modelling of flow paths /­Joyce et al. 2010/. This may indicate that themodelled area should be extended further north-east to consider correctly the transport of particles
with the longest transport times. However, even if the modelled area was extended and this resulted
in the identification of some additional discharge areas outside the present boundary, it is argued on

TR-10-0971

the basis of the modelled discharge pattern that the same types of discharge areas would be affected(i.e. lakes, streams, wetlands and shallow parts of the sea, see Section 7.2.2). Therefore, the risk calculations based on the currently identified discharge areas are considered to fulfil needs of the assessment.
Shoreline regression affects the size and position of potential discharge areas in two important ways.
First, the size of a discharge area that receives groundwater from the repository over extended periods of time (e.g. areas situated above the repository) decreases substantially when the area emerges
from the sea. Secondly, changes in the hydrological driving forces due to a regressing shoreline will
directly affect the discharge of deep groundwater; the discharge in terrestrial areas will cease withtime, whereas new discharge areas will appear in the newly emerged parts of the landscape and inshallow parts of the sea.

7.1.2 Description of delivered discharge points
The hydrogeological modelling, briefly described above, traced the transport of “water parcels” orparticles from each canister position through the bedrock and regolith up to the ground surface. The
positions where the traces reached the surface are called “discharge points”. The present analysis isbased on discharge points delivered in September 2009; the data are stored in the SKB SR-Site data
storage1.
There are three data sets with discharge points, two covering the whole model area (regional models)and one for the area close to the repository (local model). The two regional models are based on
different hydrogeological models. The differences in traces between the models are small; only nine
traces have different exit positions.
Version 1 of the regional models have been used for the selection of basins included in the landscapemodel. The data set holds 89,908 records. Many of the traces never reach the surface, or may reach thesurface when the Forsmark area experiences a glacial climate domain (> 57,000 AD). These records
were deleted from the data set; the number of records left after deletion was 20,802. The spatial
distribution of the discharge points from the regional model is shown in Figure 7‑1. This distribution is
not taking the temporal distribution into account and is not to be used to delimit discharge areas. The
temporal distribution is discussed in Section 7.3.1 together with the identification of biosphere objects.
Discharge points for the whole simulation period are shown in Figure 7-1. The discharge points
are displayed on a background map showing the present shoreline; note that many of the discharge
points shown in the figure were calculated using other (future) shoreline positions. The major part ofthe discharge points are found close to the repository during submerged periods, and a minor part are
displaced late in the simulated interglacial in the upper north-eastern area, mainly due to shoreline
displacement. The most distant points are displaced approximately 10 km (Figure 7-2).
The distribution of travel distances (calculated as the straight distance between canister and discharge
positions) is bimodal with local maxima at c. 750 and 9,250 m, whereas travel distances between
5,000 and 8,000 m are few. Note that more than 500 traces are less than 500 m in travel distance,
although the vertical distances alone are almost 500 m; these particles travel straight up through the
bedrock. Approximately 42% of the discharge points are within what is referred to as the northernbranch and 58% in the southern branch (all canister positions are situated in the southern branch).
The distribution of discharge points by basin is shown in Table 7‑1.
Five of the basins contain 94% of the discharge points (Table 7‑1). The two basins 118 and 124(Figure 7‑8) show high values after normalisation by area. As many as 14 basins have no discharge
points and 8 basins have less than 100 discharge points, see Figure 7-8 for a map of basins. The
discharge points are mostly situated in low-points in the landscape (groundwater discharge areas)
and more than 70% of the points are in consequence situated in present and future lakes.

SKB doc 1263189 (http://svn.skb.se/trac/SR-SiteDataStorage/browser/SERCO/Pathlines/090911)
access might be given on request.

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Figure 7‑1. Distribution of future discharge areas resulting from hydrogeological modelling. Note that
extension of the sea (light blue) mirrors the current situation. Extension of the sea at the time of future
discharge will be reduced as a result of isostatic rebound. The site for the proposed repository is marked
with blue frames.

7.2

Near-surface flow and transport

7.2.1 Flow model results for different climate conditions
The hydrological development of the landscape in a hydrological perspective was studied by analysing the effects of shoreline displacement, development of the regolith layers and the vegetation coverin different climates /­Bosson et al. 2010/. Numerical models providing output on present and future
conditions were developed using the MIKE SHE tool and applied in order to answer questions about
the future hydrology in Forsmark. In particular, the modelling focused on the development of waterbalances, recharge-discharge conditions and on solute transport in the uppermost part of the bedrockand in the regolith.
Present conditions regarding meteorology, surface water levels and discharges, groundwater levels
in regolith and bedrock, and locations of recharge and discharge areas were investigated during
the site investigations. Detailed modelling of the present hydrology at the site was performed andpresented as a part of the site descriptive modelling /­Bosson et al. 2008/. The data and models fromthe site investigations and the site descriptive modelling provided the basis for the models describing
possible futures in Forsmark. Simulations were performed for present conditions, wet temperate
climates and for a periglacial climate.

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5000
4500

Number of discharge points

4000
3500
3000
2500
2000
1500
1000
500
0

Travel distance (m)Figure 7-2. Distribution of particle travel distances between canister positions in the repository anddischarge positions on the surface for the whole simulation period. Figure from /­Lindborg 2010/.
Table 7-1. Number of discharge points and density of points per basin /­Lindborg 2010/.
Locations of individual basins listed below are shown in Figure 7‑8.
Basin

PointsPoints/km2

101
105
107
108
109
110
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
131
132
133
136
141
146
147

0
369
0
0
85
19
28
29
2,842
12
2,940
14
5,892
0
4,511
3,279
0
0
290
157
0
1
13
0
0
0
0
321
0
0
0

0
13
0
0
56
3
40
18
150
3
208
1
2,939
0
865
644
0
0
1,189
449
0
3
182
0
0
0
0
143
0
0
0

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The SR-Site MIKE SHE modelling were performed as a regional model, primarily used for flow
calculations, and two local models that were used mainly for transport modelling (Figure 7-3). The
transport analyses included both particle tracking, where calculated flow paths and discharge points
were used to assess the discharge points delivered from the modelling of the deeper groundwater
system, as described above, and modelling with the MIKE SHE advection-dispersion module, which
was used to investigate solute dispersal.
The water balances calculated by numerical modelling with future shorelines do not differ significantly from the measured or calculated water balances for present conditions. Thus, when studying
only the effects of the shoreline displacement on the overall water balance, no major changes frompresent conditions were found. The flows between different model compartments differ less than
10% in all the studied cases. The internal distribution of the precipitation water is approximately
70% evapotranspiration and 30% runoff independently of the shoreline position and hence of theland area considered (present or future land areas).

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Figure 7-3. The regional and local MIKE SHE model areas. In the figure, the site descriptive modelling (SDM)
regional model area and the future lakes and streams are also marked. Figure from /­Bosson et al. 2010/.

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The considered case of a wet temperate climate implies a three-fold increase of the precipitationcompared to the current mean annual precipitation. In this case, the runoff is approximately 20% of
the applied precipitation and the evapotranspiration is 80%. Due to the higher evapotranspiration
caused by the higher temperature and the longer vegetation period, the proportion of the precipitationwater leaving the model volume as runoff under wet temperate climate conditions is lower than for
normal temperate climate conditions. However, there is an absolute increase in the calculated annual
runoff from c. 180 mm to c. 360 mm. The increased runoff under wet temperate climate conditions
affects the residence times of water in lakes and streams, which influence the transport of matterwithin and between the different ecosystems in the landscape.
The largest change in the overall water balance is observed when modelling periglacial climate conditions. The internal distribution of the precipitated water is 50% runoff and 50% evapotranspiration. The
water demand from the vegetation is very low, due to a more sparse vegetation cover with less total leafarea, but also because the unfrozen period is short. Even during the active period, the temperature isquite low; thus, there is no driving force for effective evapotranspiration. The precipitation applied whenmodelling cold conditions is c. 20% lower than for temperate weather conditions. However, because theevapotranspiration is very low, the runoff leaving the system via the surface water streams is larger forthe cold climate than under temperate climate conditions, even though the applied precipitation is lower.
The shallow groundwater table at present will prevail also under future conditions. However, a loweringof the water table within the area above the planned repository can be noticed when taking shoreline
displacement and the development of the regolith into consideration. At present, the main part of thearea has a groundwater table within one metre below ground surface. Under future conditions with amore distant shoreline, the depth to the groundwater will increase somewhat. Specifically, the model
results indicate that the part of the model area having depths between 1 and 3 m below ground surface
will increase. With a lower groundwater table, the amount of water transported in the upper part of the
profile, which has a high transport capacity, will decrease.
The overall pattern of recharge and discharge areas is the same for the different time periods studied.
A scattered pattern governed by the local topography is found in the regolith independently of theshoreline position, the vegetation or the applied coupled regolith-lake development model (RLDM)/­Brydsten and Strömgren 2010/. In the bedrock, discharges are concentrated to areas under thelakes and stream valleys. Changing the RLDM from the one representing the present conditions to
the ones reflecting the regolith development up to 5000 AD or 10,000 AD does not have a strong
influence on the pattern of recharge and discharge areas. There are some exceptions, but, in general,
the overall recharge-discharge pattern seems to be governed by the topography, and not so much by
the stratigraphy, thickness or type of regolith.

7.2.2 Near-surface flow paths
Water flow paths from the deep bedrock do not change with different output from the RLDM orvegetation covers. The areas receiving particles at present are also discharge areas in the future
models as long as a temperate climate is applied. As described above, most of the lakes act asdischarge areas and the transport under the lakes is dominated by the vertical component as long as
the transport takes place in the bedrock. The transport in the regolith under and around the lakes isdominated by the horizontal component. The low conductivity lake sediments reduce the verticalflow through lake bottoms and the main discharge of groundwater is seen along the shorelinesof the lakes and wetlands.
Figure 7‑4 compares discharge points calculated by particle tracking in the MIKE SHE and ConnectFlow
models, where ConnectFlow is the modelling tool used in the bedrock hydrogeology modelling /­Joyce
et al. 2010/. The starting positions of the particles in the MIKE SHE simulation were given by theConnectFlow particle positions at 40 m.b.s.l. which means that observed differences in discharge
locations are caused by differences between the two models in the representation of properties andprocesses in the upper 40 m of the system. For the particles going to surface streams, the differences
between results from the two models are small. However, some differences can be observed in thelake areas. The particles leaving the MIKE SHE model tend to be more concentrated along theshorelines of the lakes, whereas the particles from the ConnectFlow model mainly appear in thecentral parts of the lakes.

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Figure 7-4. Comparison of discharge points in local model A, calculated with MIKE SHE (red dots) andConnectFlow (CF, green dots). The modelled future surface streams are indicated by blue lines “MIKE 11
network”. Figure from /­Bosson et al. 2010/.

One reason for the differences between the results from the ConnectFlow model and the MIKE SHE
model may be that the extents and thicknesses of the lake sediments are described in more detail in
the MIKE SHE model. Another reason is that the MIKE SHE model includes more surface processes
than the ConnectFlow model. In relation to the lakes, the evapotranspiration along the lake shorelines
decreases the groundwater head in the upper soil layers, creating an upward hydraulic gradient fromthe deeper layers /­Bosson et al. 2008/. However, more important to note is that particles appear todischarge in the same objects in the two models, which means that the simplified representation of
the surface system in the ConnectFlow model has no major effects on the identification of biosphereobjects in the landscape model (cf. below).
The same pattern as described above is found when a wet temperate climate is applied to the model.
Under cold conditions with continuous permafrost, the pattern of recharge and discharge areaschanges dramatically. During the present temperate period, the local topography has a strong influence on the location of recharge and discharge areas, whereas the recharge and discharge areas areconcentrated to through taliks under permafrost conditions. Through taliks provide the only available
pathways for the water, and consequently also for matter transported by water, to be transported up
or down through the permafrost. Figure 7-5 shows results of particle tracking between through taliks
in a model domain with a 100 m thick permafrost layer (except in taliks).

TR-10-0977

Figure 7-5. Flow paths between through taliks in a model with 100 m thick permafrost (except in unfrozen
taliks). Particles were released in the uppermost regolith layer during the thawed season, i.e. the period
when this layer is not frozen. The colour along each flow path shows the accumulated particle travel time indays. Figure from /­Bosson et al. 2010/.

7.2.3 Transport by advection and dispersion
Of particular interest are the advection-dispersion simulations of transport from sources defined byindividual canister positions. These transports are characterised by relatively larger groundwaterflow velocities and short transport times to the surface. Figure 7‑6 shows results from one of thesesimulations, which can be regarded as typical. As shown in the figure, transport is in the verticaldirection up to the near-surface layers where horizontal spreading takes place. A detailed presentation of this modelling and the results obtained is given in /­Bosson et al. 2010/.
7.2.4 Radionuclide retention and reactive transport
In addition to the advective and advective-dispersive simulations discussed above, reactive transportmodelling has been performed. The reactive transport modelling takes into account that dissolved
substances may be affected by processes such as sorption and precipitation, which act to retain thetransported substances in the regolith. This contrasts to the advective and dispersive simulations,which describe how water-borne particles are transported without interactions with solid phases.
Both conceptual modelling of radionuclide retention processes and numerical modelling of coupledadvective-dispersive and reactive transport modelling have been performed. This modelling work
is reported in /­Piqué et al. 2010/, from which the contents of this section were taken; an extended
summary is provided in /­Lindborg 2010/. The objective of the modelling performed was to evaluate

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Figure 7‑6. Concentrations after 1, 10 and 65 years of advection-dispersion simulation of transport from asingle canister position. The source in MIKE SHE is at –40 m.a.s.l. along a flow path identified by particle
tracking in the ConnectFlow model. Red colour indicates high and yellow low concentration. Figure from/­Bosson et al. 2010/.

TR-10-0979

the retention capacity of the near-surface systems, which in the numerical modelling part of thework were represented by one till system and one clay system. The study was focused on long-lived
radioactive isotopes of C, I, Cl, Nb, Ni, Mo, Se, Tc, Th, Sr, Ra, Cs and U.
Conceptual description and numerical simulations of radionuclide reactive transport show that cationexchange and surface complexation on illite are active processes for the retention of several radionuclides (U, Th, Ni, Cs, Sr and Ra). Surface complexation on iron hydroxide is an active process inthe till system, able to effectively retain U and Ni. Another retention process of importance is theincorporation of the radionuclides into mineral phases, either by the precipitation of pure phases orsolid solutions. Quantitative modelling has been useful to illustrate the incorporation of C and Sr in
the carbonate solid solution, as well as the precipitation of uraninite in the clay and the precipitationof native selenium and radiobarite in the till.
Other mineral phases that potentially could retain U, Se, Nb and Tc do not precipitate in the numerical simulations. This is either due to the considered pH-Eh conditions and/or because the dissolved
concentrations of the studied elements are not high enough under the considered simulation conditions. It is important to keep in mind that changes in these parameters and in the boundary conditions
could modify the predicted behaviour of these elements.
The elements Th, Ni and Cs are most significantly retarded, mainly through sorption onto illite. Therefore,
if the amount of illite (i.e. the amount of available sorption sites) decreases, the retardation of theseelements will also decrease accordingly, as illustrated by the sensitivity analyses performed. The
strong retardation predicted for these elements is in good agreement with reported Kd values for
Forsmark till and lake sediments /­Sheppard et al. 2009/. According to the models, Cs, Th and Ni arestrongly retained, whereas C, U, Sr and Ra are more mobile. The simulations also show that Nb and
Tc behave conservatively in both domains, as expected due to their anionic character under these
conditions, and Se only in the clay domain.
Although not directly comparable to the calculated effective Kd, it can be stated that the reported Kdvalues of Forsmark soils and sediments /­Sheppard et al. 2009/ show a similar general trend (i.e. themost strongly retained elements are Th, Cs and Ni, followed by U and Sr). Se and Nb are the two
exceptions, for which the computed behaviour does not agree with reported Kd values. Not all thepossible retention processes considered in the conceptual model were included in the simulation,either due to lack of reliable knowledge on the processes and/or scarcity of thermodynamic datarequired for the numerical modelling.
Besides the retention mechanisms, other processes that act to reduce radionuclide concentrationsin the studied systems are dilution of the radionuclide-bearing deep groundwater, which applies toall elements, and radioactive decay. Decay is not included in the performed modelling, but it can benoted that the radionuclides being most strongly affected by this process are the relatively short-lived
Ra-226 and Sr-90.

7.3

Biosphere objects and landscape modelling

The temporal and spatial extension of the biosphere is analysed in a landscape model. This uniqueapproach allows a good resolution of how potential discharges from a future repository can beredistributed in the surface ecosystem considering constraints in the ecosystem, hydrology and land use
in a coherent and systematic way. The biosphere at Forsmark is represented by a set of interconnected
biosphere objects. A biosphere object is defined as an area of the landscape that can receive radio­
nuclides released, either through discharge of deep groundwater or in contaminated surface water, at
any time during a glacial cycle. The identification of biosphere objects, their positions in the landscape,and their development in time, are described below and in more detail in /­Chapter 6 in Lindborg 2010/.

7.3.1 Identification of biosphere objects
Clusters of discharge points have been used to identify the locations of biosphere objects in the Forsmark
area. By applying discharge points on the landscape development model in time steps of 1,000 years, thespatial and temporal pattern of discharge areas were identified and assigned to specific objects. Threedifferent patterns in time were observed: i) discharge areas that were active under submerged conditions

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only, ii) areas that received discharge during all succession stages, and iii) discharge that followed theshoreline displacement towards north-east. The outer boundary of each biosphere object was determinedfrom the hypsography of the sea basin during the submerged phase, whereas the shoreline of the lake attime of isolation from the sea delineates the biosphere object during the lake and terrestrial phases. The
identification of biosphere objects is illustrated in Figure 7‑7 as an example of how discharge points areapplied on a specific time step map (11,000 AD) of the future Forsmark landscape.
Key geometrical characteristics of the objects have been determined from the local (i.e. sea or lakebasin) topography, whereas the regional geometry defined landscape characteristics, like hydrologicallinks between biosphere objects and sizes of catchment areas. In total ten biosphere objects have been
identified, containing a discharge area during any period of the present interglacial. Five additional biosphere objects located downstream of the discharge areas have also been identified. Finally, to represent
discharge directly into a stream or a wetland without an initial lake stage, the basin of one of the original
biosphere objects has been partitioned into three separate biosphere objects.

7.3.2 Geometric features in the landscape
The landscape model is, apart from the biosphere objects, based on three different geometric features:basins, watersheds and sub-catchments. These partly overlap each other and are used for different
tasks to define and populate the final Landscape model. The “basin” is the main feature and most of
the parameters are based on data from each basin area. The watershed is the total upstream area fora basin, and the sub-catchment is the drainage area for a biosphere object minus the drainage area forthe surface water inlet into the biosphere object. These features are described in more detail below.

Figure 7‑7. Illustration of the work to identify biosphere objects. The discharge points are displayed on
the landscape development model (here shown without sediment dynamics, lake infilling and vegetation
type/land use) for a specific time step (11,000 AD). The discharge clusters are encircled in red where thebiosphere objects were identified and the black arrows indicate the surface water flow paths. Figure from/­Lindborg 2010/.

TR-10-0981

BasinA basin is defined as the catchment for an outlet from a lake all the way to the outlet of next upstream
lake. If a basin has two or more major streams (streams discharging lakes treated in the landscapemodel), the basin is defined as the actual lake catchment minus all upstream lake catchments. The
basin area is constant over time and smaller than or equal to the maximum watershed area.
The landscape is divided into basins (Figure 7-8). Each basin holds one single lake (existing or future).
The extents of the basins were established by mapping the water divides for the total model area byusing digital elevation models and field measurements /­Brunberg et al. 2004, Brydsten 2006/. Onlybasins that are of significance for the radionuclide model are used in the final landscape model. To
identify areas of significance, the hydrogeological models were used as described above in this chapter.
Watershed

The watershed is always the largest of the three geometric features used. It is defined as the catchment to an outlet from a lake. The watershed area is used for calculation of discharge (m3 s–1) withknown specific runoff (m3 s–1 m–2). The discharge is then used for calculation of the theoretical water
turnover time of the lake. It is also used for calculation of the fresh water dilution of the sea waterin a basin and also the theoretical residence time of the sea water. In Figure 7‑9, the watershed isillustrated for a fictitious lake. All rain that falls within the watershed is drained through the lake

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Figure 7‑9. Illustration of watershed and sub-catchment for a hypothetical lake. The watershed and the
sub-catchment are outlined in red and yellow, respectively. The sub-catchment is defined as the catchment
for the lake minus the catchment for the lake inlet (see text for details). Figure from /­Lindborg 2010/.

outlet. The watershed area is in Forsmark successively increasing over time due to regression following isostatic rebound during an interglacial. Note that island areas are included in the watershed area
and thus the discharge in the stream will not be correctly calculated for time steps with archipelago
configuration.
Sub-catchment

The geometric feature sub-catchment is defined as the catchment of the outlet of a lake minus thecatchment of the inlet of the same lake. The sub-catchment is used in the radionuclide model for
calculation of diffuse discharge of water into the lake, i.e. inflow of water not included in the major
stream discharge. The sub-catchment area is a constant and always equal to or smaller than the basin
area. The sub-catchment of the hypothetical lake is shown in Figure 7‑9. The sub-catchment area
is identical to the corresponding basin area for basins situated highest in the river systems. Only
small differences in area occur where two linked lakes are in juxtaposed positions.

7.3.3 Temporal development of biosphere objects
The core features of the landscape relief in the Forsmark area are determined mainly by the bedrock
topography /­Lindborg 2010/. The small-scale undulations of the bedrock surface are smoothed byglacial and post-glacial deposits, which, to a limited extent, are redistributed by wave erosion when
the shoreline regresses over the area. Since the bedrock topography is expected to be only marginallyaffected by weathering, and since the shoreline displacement is expected to be repeated during future
glacial cycles, it is argued that the development of the landscape during the present interglacial will
give an acceptable representation also of the landscape development during repeated glacial cycles.
Since each biosphere object is associated with the local topography of a sea or lake basin, the physicalboundaries of the object reflect the geometry of the bedrock and the overlying till and glacial sediments, which changes marginally during an interglacial. In contrast, the properties of the biosphereobjects change continuously, e.g. due to shoreline displacement, wave erosion and sedimentation, lake
infilling and ecosystem succession. When the glacial ice sheet has disappeared, all biosphere objects
will typically go through a similar succession, from being part of the open sea, over a sea bay phase,to a lake, which eventually will transform into a wetland. The associated work flow for describing thedevelopment of a biosphere object is illustrated in Figure 7‑10.

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Figure 7‑10. Flow chart of activities and inputs to obtain the biosphere object characteristics. The starting
point is the description of present-day and historical conditions of the site. Data from the site description
together with process understanding provide the starting point for producing models describing the site
development for a number of disciplines. All the combined models are then merged together into a landscapedevelopment model. By using the discharge information from the hydrogeological modelling, the biosphereobjects are identified. The landscape model is constructed by extracting information from the areas identified
as biosphere objects from the landscape development model. Light blue colours indicate activities not
performed within the biosphere modelling in SR-Site. Figure from /­Lindborg 2010/.

The temporal development of each object is described by the modelled succession from the landscape development model. Most biosphere objects are predicted to go through a general succession
during a temperate interglacial, which is characterized by the following four main stages.
•

Sea stage – the biosphere object is a sea basin. As landscape emerges from the sea, it continuously
decreases in size. During this period, the object has only an aquatic part and all fluxes from thedeep regolith layers are directed to aquatic sediments.

•

Transitional stage – the sea bay is isolated and transforms into a lake or a stream (aquatic object)surrounded by wetland (terrestrial), or directly into a wetland. The isolation of a lake in the
Forsmark area takes approximately 500 years, and, during this phase, saltwater flooding will
occur periodically. During the transitional stage, the values of the aquatic model parameterschange continuously from sea to lake characteristics.

•

Lake stage – the surrounding wetland expands into the lake, and aquatic sediments are gradually
covered by a layer of peat. This process is represented in the radionuclide model by a flux ofradionuclides from the aquatic sediments to the terrestrial regolith. The lake stage ends when thelake has been fully transformed into a wetland.

•

Terrestrial stage – the biosphere object has reached a mature state and no further natural succession
occurs. For the majority of discharge areas, the end stage is a wetland that is drained by a small
stream. However, in some small objects located upstream, no stream develops, e.g. object 121_3,
and in a few downstream objects a substantial river flows through the object, e.g. object 114.

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7.3.4 Biosphere objects in the landscapeEach biosphere object has a defined location in the landscape. The object may change in type of eco­system or size as described in sections above. This is due to natural succession within objects, or the
long-term development of landscape features. Depending on succession stage, the objects that define
the landscape model therefore will have a specific set of ecosystems.
At the start of an interglacial, all are objects submerged by approximately 180 metres of water. This
landscape is described as a submerged landscape, and all objects interact with their neighbour objects.
As the shoreline displacement proceeds, the objects gradually emerge above the sea and becomelakes and wetlands. At this stage, the dominating interactions start to go one way, slowly turning into
a terrestrial surface flow system where the chain of objects is linked in a one way direction from themost upstream object and down to the final outlet to the Baltic Sea. Figure 7‑11 shows the landscapemodel displayed on the landscape development model at three different times during the modelled
time period.

1

101

107

105

1

10

101

108

107

105

108
114

114

117

117

116

121_03

118

120
125

116

121_03118

121_02123

121_01

124

10

120

121_02
125

126

136

124

123

121_01

126

136

1

101

107

105

10

108
114

117

116

121_03

118

120

121_02
125

124

123

121_01

126

136

Figure 7‑11. The landscape model displayed on the landscape development model at three different time
steps (2000, 5000 and 10,000 AD). The boxes shows biosphere objects (with id numbers) at their approximate locations in the landscape and red arrows indicate the surface water flow paths connecting the objects.
The blue boxes represent the combined objects of Öregrundsgrepen (object 10), see text, and the model area
outlet, the Baltic Sea (object 1).

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To represent the total area of the sea covering all submerged basins, a general object is included in
the model (object id 10). This object is used to merge all sea objects into one object representingÖregrundsgrepen. Moreover, the landscape constellation of biosphere objects used in the radionuclide
model may be changed when performing simulations for different purposes. For example, all objects
can be used when analysing transport in the whole surface water network, whereas a simulation
calculating concentrations and doses for a single object may be restricted to the object of interestand the affected downstream objects (Chapter 8).

7.3.5 Parameterisation of biosphere objects
The landscape development model is used to parameterise the biosphere objects during landscapedevelopment. This model contains all information needed to describe the time-dependent properties
for each biosphere object in the landscape over time. By following the succession for each biosphereobject on the landscape development model, the data is extracted into tables (Table 7‑2). The bedrock
topography and the regolith depth has been mapped at the site /­Lindborg 2008/. These descriptions
have been used to model the landscape development together with the effects of shoreline displacement and lake infilling.
The information from the landscape development model has been integrated and averaged over theobject area to describe the development of the biosphere objects in terms of a number of characteristics that change continuously over time. Properties that are used to describe the individual biosphereobjects over time include e.g. area and depth of regolith layers, water depth and volume of sea basins
and lakes, areas of sea and lake bottoms that can support primary production, sedimentation andresuspension rates, wetland areas and upper regolith depths (soils and sediment).
Table 7‑2. The output data from the landscape development model for the biosphere objects(dw stands for dry weight).
Name

Description

Units

Aqu_area_obj

Water aream2

area_subcatch

The area of the subcatchmentm2

area_wshed

Watershed aream2

depth_averAverage water depthmdepth_max

Maximum water depthm

growth_rego

Average sedimentation rate calculated forlake and marine bottoms

m/year

res_rate

Resuspension ratekg dw/(m2year)

sed_rate

Sedimentation ratekg dw/(m2 year)

Ter_area_obj

Organic sediment area in lakes

m2

threshold_start

The year a threshold starts isolating a baythat will become a lakeyear

threshold_stop

The year a threshold has isolated a baythat from that year is a lakeyear

threshold_end

Time when ingrowth of wetland stops (inmost cases a stream remains)year

threshold_agriculture

Point in time when wetland is 2 m above
sea levelyear

Aqu_z_rego_pg

Depth of organic and inorganic postglacial
deposits (gyttja, clay gyttja, sand andgravel) under sea, lake or streamm

Ter_growth_rego

Growth of relative wetland area

m2/(m2 year)

Ter_z_regoMid_pg

The depth of the post glacial deposits inthe wetland (these are covered by peat)m

Ter_z_regoUp

The depth of the terrestrial upper regolithlayer (peat)m

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7.3.6 The landscape model during the reference glacial cycle
As described in Chapter 6 the landscape will change dramatically during the period of a glacial cycle.
This does not necessary mean that the configuration of biosphere objects will alter. We describe how
the biosphere objects will undergo a succession from sea stage, via lake/wetland to a terrestrial stage
during non-glacial conditions. This is a development that may take between 8,000 and 20,000 years
depending on where in the landscape the object is located. The landscape model comprises mainly
terrestrial ecosystems when the first period of periglacial domain starts at Forsmark (Figure 7‑12).
Only one or two objects are still in the lake phase and no objects represent the sea.
The submerged landscape is used to describe the glacial climate domain (Figure 7‑12). This is dueto the possibility of having a situation where a human population is using the marine landscape forfood gathering when the ice edge is close to the site. This situation will only be possible in submerged
conditions during ice cap retreat. There is no other relevant landscape configuration under glacialconditions due to absence of inhabitants.
This chapter summarises the methods and results described in /­Lindborg 2010/ and provide a few examples of modelling results and supporting analyses. The use of output from the landscape development
model and the hydrogeological models to identify discharge areas (biosphere objects) are demonstrated.
Further, it is shown how these areas are described in terms of properties and processes needed to model
radiological effects of radionuclide releases to man and biota, and how time-dependant changes of biosphere objects are handled. These changes include the whole process from deglaciation, via a temperate
climate domain during an interglacial to the periglacial domain, and finally the reappearance of a glacial
domain. By applying the described methodology, the landscape data needed to populate the radionuclide
model for all biosphere objects are obtained in space and time.

1

1

101

107

105

101

10

107

108

105

108
114

114

117

117

116

121_03

118

120

121_02
125

136

124

116

121_03

118
123

121_01

126

10

120

121_02
125

124

123

121_01

126

136

Figure 7‑12. Figure illustrating the landscape model under periglacial and submerged conditions.
The boxes show biosphere objects (with id numbers) at their approximate locations in the landscape,and red arrows indicate the surface water flow paths connecting the objects. The blue boxes representÖregrundsgrepen (object 10) and the model area outlet, the Baltic Sea (object 1).

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8

The radionuclide model for the biosphere

In SR-Site, assessment of doses to humans resulting from releases to the biosphere in different scenarios have been calculated by multiplying release rates, or pulse releases, of different radionuclides
with a landscape dose conversion factor (LDF). The LDFs are assessment endpoints for the biosphere
analysis and represent the mean annual effective dose to a representative individual from the most
exposed group, resulting from a unit constant release rate, or alternatively per unit released in a single
pulse to the biosphere, of a specific radionuclide.
In SR-Site the methodology for calculating transport and accumulation in the biosphere has been
improved in several ways as compared to previous safety assessments. For example the terrestrial
and aquatic ecosystems are combined in one model, and the transition from sea basin to lake andwetland is handled continuously. Plant uptake is included in the mass balance and is modelled as afunction of primary production.
This chapter describes the methods used to assess the safety of humans inhabiting potential discharge
areas (i.e. to calculate LDFs), and to calculate activity concentrations in environmental media that areused in the assessment of protection of the environment (Chapter 11). The chapter starts by presenting
the assumptions made about radionuclide releases from the repository (source terms). It then describes
the types of future ecosystems that are considered in the safety assessments and the habits andcharacteristics of future inhabitants. Next follows sections that describe the conceptual and mathematical model used to simulate transport and accumulation of radionuclides in the biosphere, andthe methods used to calculate activity concentrations in environmental media, and to assess human
exposure through relevant pathways. The definitions of the LDFs for a continuous release rate andfor a pulse release are given, and the procedure to calculate LDFs for different climate conditions is
described. The last sections describe the Pandora software used in the calculations and the procedureused to assure quality and traceability from site data to LDF values.
A detailed description of the methods that are presented in this chapter, including the mathematicalequations applied in the model, is provided in /­Avila et al. 2010/ and /­Andersson 2010/.

8.1

Source terms

In the corrosion and the shear load scenarios, radionuclides from the repository are unlikely to reachthe biosphere within the first 100,000 years. However after this period contaminated groundwaterfrom the repository may reach the biosphere resulting in a continuous release of radionuclides during
more than 1,000,000 years. When a release from the repository reaches the biosphere 100,000 years
after closure, the peak release rates for most dose dominating nuclides will remain on a near-constantlevel for periods of 10,000 years or more (see SR-Site main report for details).
In both of the significant release scenarios, radionuclides that reach the biosphere are most likely
originating from one single canister. In the corrosion scenario, the failing canister has been depositedin a position with a high groundwater flow rate, which is associated with low geosphere transport
resistance. In the shear load scenario, the shearing fracture is assumed to be among the larger inthe rock fracture network, and therefore radionuclide retention in the geosphere is pessimisticallydisregarded in the safety assessment, (see further the SR-Site main report). For releases which areassociated with low or negligible geosphere transport retention, the shoreline position is expected tohave limited effect on the geographical location of the discharge area, and discharge of contaminatedgroundwater may thus be restricted to one biosphere object /­Lindborg 2010/.

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For the calculation of LDFs, it has consequently been assumed that the release to the biosphere fromthe fuel matrix and corroded metals will be approximately constant on the time scale of the biosphere assessment (~20,000 years). It is cautiously assumed that the whole release of radionuclides
will reach the discharge area where it will cause maximum exposure (the most exposed group), i.e.
the release will not be subdivided over several biosphere objects. Similarly, for the calculations of
the modified LDF for pulse releases, it is cautiously assumed that the total instantaneously accessible
fraction of radionuclides from fuel dissolution will reach the discharge area where it will cause
maximum exposure.
The effect of indirect release to a biosphere object, originating from a contaminated object locatedupstream, has not been included in LDF calculations. This simplification is appropriate for derivationof LDF values that represent the maximum doses across all biosphere objects in the Forsmark area
during the whole simulation period (see Section 12.3.1).
In addition to the radionuclides released into deeper parts of the regolith of a biosphere object, it has
been assumed that the released radionuclides also reach a well drilled in the bedrock, as soon as abiosphere object has emerged from the sea.

8.2

Future ecosystems

The radionuclide model for the biosphere simulates transport and accumulation of radionuclides indischarge areas of Forsmark. It is assumed that the landscape development during repeated glacial
cycles will follow a path similar to the present glacial cycle. Thus, also after a future deglaciation,discharge areas will go through a succession from being part of the open sea, over a sea bay phase, toa lake, which eventually will transform into a wetland (Section 6.2.7).
Future sea and lake ecosystems are assumed to have similar characteristics as the current aquatic
ecosystems in Forsmark. The wetlands that will develop from future lakes are assumed to be similar
to the rich fens that are presently found in the area. If drained, these wetlands will provide an organic
soil rich in nutrients that will be suitable for cultivation for a limited period of time.

8.3

The most exposed group

In SR-Site, the most exposed group is defined as the group of individuals exposed to the biosphereobject with the potentially highest contamination, considering a glacial cycle from a submergedlandscape to fully terrestrial conditions. A representative individual from the most exposed group isassumed to spend all time in this object, and get his/her entire supply of food and water from the object.

8.3.1

Production and consumption of food and size of the most
exposed group
The production capacity for human food in a biosphere object is directly determined by the size ofthe object, (i.e. the size of the sea basin or the size of the wetland and the surface water body), andthe sustainable yield of natural foods and agricultural products, which in turn may vary with climaticconditions. Assuming that food production is the limiting factor for humans living in a biosphereobject, the number of individuals that can be sustained in a biosphere object is thus proportional tothe area of the object. However, the size of the population that can be sustained also depends on landuse, since the productivity per unit area of crop is two to three orders of magnitude larger than the
productivity of natural foods in a wetland.
For SR-Site, it has been assumed that all available food sources from both aquatic and terrestrial
parts of a biosphere object are utilised by human inhabitants. Additionally, it is assumed that wetlands will, at least partly, be converted to agricultural land as soon as that is possible (Section 8.3.3).
No assumptions are made regarding food preferences of future individuals. Instead, the human dietreflects the production of different types of food in the object.

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Thus, the human diet consists of sea food when the biosphere object is submerged by sea water.
When the object has been isolated from the sea, the diet consists of natural food from lakes, streams
and wetlands. When agriculture is possible, the diet will be a combination of natural food and agricultural produce. The contribution of each food type to the human diet is assumed to be proportional
to the production of that food type in the object. When agriculture is possible, it is deemed equally
likely that the drained wetland is used for food production such as cereals, root crops, vegetables orfodder for meat and dairy production.
Biosphere objects with a large proportion of wetland that can be drained and cultivated can typicallyfeed a population in the range of 170–1,300 persons. Biosphere objects that cannot be cultivatedcan only support a limited number of individuals, aorund10 individuals during submerged or coastal
conditions and typically one or a few individuals when inhabitants are limited to utilization of lakes
and wetlands for food.

8.3.2 Land use on artificially drained wetlands
When the wetland in a biosphere object has emerged to a sufficiently high elevation above sea level toavoid periodic seawater intrusions, it can be drained and used for agricultural purposes. It is assumed
that human inhabitants can drain and subsequently use wetlands situated more than 2 metres above
the sea level for production of food crops and livestock at any point in time. For the biosphere assessment it is further assumed that a wetland will be converted to agricultural land at the point in time whenutilization results in the largest annual dose.
Sustainable use of organic soils that originate from drained wetlands in the Forsmark area is expected
to be productive for agriculture only during a limited time. This is because peat subsides when the
groundwater is lowered, and the organic layers of the peat and the former lake sediments will typicallybe oxidised within 50 – 100 years. Regolith underlying surficial organic layers mainly consist of glacial
till rich in stones and boulders and is therefore not suitable for cultivation /­Lindborg 2010/.
There are areas in Öresundsgrepen that are covered by thick layers of clay and sand. Future shallow wetlands in these areas can probably be drained relatively easily, and the underlying minerogenic deposits
can be sustainably cultivated for thousands of years. Thus, the consequences of long-term cultivation
have been assessed for areas with deep deposits of glacial and post-glacial clay only (Section 12.2.2).

8.3.3 Water use
The need for drinking water of future human inhabitants living in a biosphere object is assumed tobe equally likely to be covered by a well drilled into the rock and by the surface water in the lake orstream passing through the object. Drinking water from a well excavated in till is assumed to have
similar composition as contaminated surface water and has not been treated as separate source ofdrinking water.
Exposure from contaminated drinking water is considered from the point in time when a biosphereobject has emerged from the sea. Livestock is assumed to consume water from the same sources ashuman inhabitants, i.e. consumption of surface water and a water from well drilled through bedrock is
considered equally likely.
Exposure from irrigation with contaminated surface water has been considered in the production ofvegetables. Surface water for irrigation of agricultural soils will be readily available in all biosphereobjects, and irrigation with water from a drilled well has consequently not been included as it isconsidered unlikely to occur /­Löfgren 2010/.

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8.4

Modelling transport and accumulation of radionuclides inbiosphere objects

The radionuclide model for the biosphere is a compartment model. A graphical representation of
the conceptual model is shown in Figure 8‑1, where each box corresponds to a model compartment.
Definitions of the compartments are presented in Table 8-1. A main assumption in the model is thatradionuclides entering a compartment become homogeneously mixed in the compartment within
the relevant time scale of the model. The model supports the description of the lower regolith withany number of compartments. In simulations for estimating LDF values only one compartment has
been used (Section 10.1). However, the effect of finer discretisation of the lower regolith has been
investigated in a separate analysis (Section 12.3.1).

8.4.1 Radionuclide fluxes
The arrows in Figure 8‑1 represent radionuclide fluxes between compartments and fluxes into and outof the system. Radionuclide fluxes are linked to the main fluxes of matter in the biosphere, i.e. water
fluxes (2 in Figure 8‑1), gas fluxes (3) and particle fluxes (4). Radionuclide transfers mediated by biota,
like uptake by primary producers, have also been included in the model (6). The arrow reaching thelower regolith compartment (1) represents radionuclide releases from the geosphere into the biosphereobject. These releases are directed to the deeper parts of the regolith, which at the site normally consistsof glacial till deposited on the bedrock.

3

Atmosphere
Ter Primary
producers
Biota

Ter
Litter

6

3
3

6

6

3

Ter Regolith Up

2

2

3

Exchange
Biota
Water

2

Ter Regolith Mid

5

2

5

Terrestrial

Exchange

Regolith Low

4

2

AquRegolith up

4

6

Aqu Primary
producers

2

Aqu Regolith Mid

2

6

Aquatic

1

Figure 8‑1. Conceptual illustration of the radionuclide model for the biosphere. Boxes represent compartments, thick arrow fluxes, and dotted arrows concentration computations for biota (not included in the massbalance). The model represents one biosphere object which contains an aquatic (right) and a terrestrial part(left) with a common lower regolith and atmosphere. The source flux (1 Bq/y) is represented by a red arrow(1). The radionuclide transport is mediated by different major processes, indicated with dark blue arrows forwater (2), light blue for gas (3), black for sedimentation/resuspension (4), dark brown for terrestrialisation(5), and green for biological uptake/decomposition (6). Import from and export to surrounding objects in thelandscape is represented by arrows marked “exchange”. A detailed explanation can be found in /­Andersson
2010/ and descriptions of the compartments are given in Table 8‑1. Figure from /­Andersson 2010, Avilia et al.
2010/.

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Table 8‑1. Compartments included in the radionuclide model for the biosphere.
Model name

Description

Regolith Low

The lower part of the regolith overlying the bedrock, primarily composed of till. It is common to
the terrestrial and aquatic parts of biosphere objects and originates from the glaciation.

Aqu Regolith Mid

The middle part of the regolith in the aquatic part, usually consisting of glacial and postglacial
clays, gyttja and finer sediments which mainly originate from the period after the retreat of theglacial ice sheet, or from later resuspended matter mixed with organic sediments.

Aqu Regolith Up

The part of the aquatic regolith with highest biological activity, comprising 5-10 cm of the upperaquatic sediments where resuspension and bioturbation can maintain an oxidizing environment.

Ter Regolith Mid

The middle part of the terrestrial regolith, containing glacial and postglacial fine material, i.e.
former sediments from the seabed / lake bottoms.

Ter Regolith Up

The upper part of the terrestrial regolith which has the highest biological activity, primarily
composed of wetland peat.

LitterDead plant material overlaying the regolith.

Water

The surface water (stream, lake, or sea water).

Aqu Primary
Producers

The biotic community in aquatic habitats, comprising both primary producers and consumers.

Ter Primary
Producers

Terrestrial primary producers.

Atmosphere

The lower part of the atmosphere where released radionuclides are fully mixed.

Radionuclides released to the lower regolith compartment are distributed to the upper layers of theecosystems by advection and diffusion. The representation of the waterborne transport of radio­nuclides
between compartments is based on detailed hydrological modelling with MIKE-SHE /­Bosson et al.
2010/. These studies have shown that the vertical hydrological fluxes in the deep regolith layer of sea
basins and bays are limited. Discharge areas above sea level may, on the other hand, have substantial
vertical fluxes with preferential flow paths through areas of higher permeability within a biosphereobject, as in wetlands surrounding lakes and streams.
The effect of radionuclide sorption on the advective and diffusive transport of radionuclides is taken
into account by assuming equilibrium between the pore water and the solid phase of the compartments.
The model also considers the transport of radionuclides absorbed to suspended particles driven by
surface water fluxes, sedimentation and resuspension processes.
The radionuclide transport mediated by biota is described in the model through fluxes driven by
primary production, in both terrestrial and aquatic ecosystems. It is assumed that equilibrium isestablished between the concentration of radionuclides in the newly produced biomass and thecorresponding environmental media (regolith for terrestrial primary producers and water for aquatic
primary producers). This is an improvement from traditional models as plant uptake is a function of
growth and the uptake is including in the mass balances /­Avila 2006, Andersson 2010/. Losses fromthe regolith and surface waters via degassing processes are conservatively neglected for all radionuclides, except for C-14. For the terrestrial biota, fixation of carbon from air by primary producers
is the main entry point of C-14 into the food chain. Therefore, gas-exchange processes between
regolith and the atmosphere, and between surface waters and the atmosphere, have been represented
in the model for this radionuclide /­Avila et al. 2010/.

8.4.2 The temporal development of biosphere objects
To be able to handle the continuous development of the landscape, the aquatic and terrestrial ecosystemwere simulated simultaneously in one model. Consequently, the radionuclide model has two parts, one
aquatic (right side in Figure 8‑1) and one terrestrial (left side). The temporal development of an object
is handled by varying the sizes and properties of these two parts in accordance with the simulated
natural development of the specific biosphere object, resulting from shoreline displacement, sedimentation, and lake infilling (see Section 7.3.5 for details on the development of biosphere objects).

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Throughout the succession from open sea to a wetland, the model representation of a biosphere objectchanges as follows. During the sea stage there are no terrestrial compartments, and all fluxes from thedeep regolith layers are directed to aquatic sediments. During a transitional stage (~500 years), the sea
bay is isolated and transforms into a lake, and a wetland starts to develop. The flux of radionuclides
from the deep regolith will gradually shift from aquatic sediments to sediments under the wetland.
During this phase, saltwater intrusions will occur with a reduced intensity, and consequently thevalues of the aquatic model parameters change continuously over the transition, from sea to lakevalues. After isolation is completed, the surrounding wetland will continue to expand into the lake.
Thus, during the lake stage, aquatic sediments are gradually covered by a layer of peat. In the model
this processes is represented by a flux of radionuclides from the aquatic sediments to the terrestrial
regolith (arrows 5 in Figure 8‑1). The natural end state of the biosphere objects is a wetland.

8.4.3 Model represention of arable land
When the wetland in a biosphere object has emerged to a sufficiently high elevation above sea level,
it is assumed that human inhabitants can drain and subsequently use wetlands for crop and livestock
production /­Löfgren 2010/. The organic layers (peat and gyttja) on drained and cultivated wetlands
will rapidly become oxidised and compacted (Section 6.1.8), resulting in an agricultural soil which isa mixture of contaminated organic matter and deeper mineral layers (glacial and postglacial deposits),
where radionuclides may have accumulated since the early sea stage.
Once the wetlands have been drained, further contamination through groundwater is assumed not
to be of quantitative importance. Instead, radionuclides are leached from the soil through runoff.
Accordingly, the highest concentrations of radionuclides in agricultural soil are expected in the
period directly after drainage, and thus the 50 years immediately following drainage are cautiously
used to assess the average exposure during a life time from the use of contaminated agricultural soil.
It is assumed that radionuclides will continuously accumulate in the wetland during the whole simulation period, and for assessing the doses it is further assumed that the wetland will be converted toagricultural soil at the point in time that results in the maximum doses.

8.4.4 Modelling radionuclide flux between biosphere objects
Biosphere objects can receive radionuclide releases to the deep regolith or from contaminatedsurface water originating from another adjacent biosphere object. The radionuclide model has been
implemented for each identified biosphere object and the individual models have been connectedwith each other according to the flux of surface water in the developing landscape (Figure 7‑11).
Thus, the flow of radionuclides between biosphere objects has been modelled as a function of
surface water and suspended particle fluxes. In the sea stage, each sea object interacts with theentire Öregrundsgrepen (object 10 in Figure 7‑11) via water exchange in both directions. FromÖregrundsgrepen radionuclides are then discharged to the rest of the Baltic Sea, which is treated asa sink in the model /­Andersson 2010/. In the transition, lake and terrestrial stages, the radionuclide
fluxes from a biosphere object (arrows marked with “exchange” that are directed from the object inFigure 8‑1) are directed to the connected downstream objects. Hence, all downstream objects will
receive inputs from one or several upstream objects.

8.4.5 Model represention of a well drilled through bedrock
In addition to the radionuclides released into deeper parts of the regolith of a biosphere object, aunit release rate has also been applied to a hypothetical well drilled through bedrock. The activity
concentration in well water (Bq/m3) is calculated by dividing the release rate (Bq/y) by the wellcapacity (m3/y). The capacity of the well has been selected to represent a drilled well in the central
site investigation area /­Gentzschein et al. 2007/ where it would have the possibility to receive 100%of the released radionuclides from the repository /­Andersson 2010/.

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8.4.6 The mathematical representation
The mathematical model for each biosphere object consists of a system of ordinary differential
equations (ODEs). Each ODE represents the rate of change for a radionuclide inventory (Bq) in amodel compartment, as a function the radionuclide fluxes (Bq/y) into and out from the compartment,
and radioactive decay.
The model assumes that the radionuclide fluxes are proportional to the radionuclide inventory inthe source compartment (Bq), multiplied by a transfer rate coefficient (1/y). Radionuclide-specificbehaviour is taken into account by using element-specific values for some of the model parametersthat describe e.g. retention (distribution coefficients or Kd) and biological uptake (concentration
ratios or CR).
The radionuclide fluxes have been modelled in the same way for all radionuclides, except for C-14.
In the case of C-14, the uptake by biota is modelled using a specific activity approach /­Avila and Pröhl
2008/, and gas exchange between the peat and surface water on the one hand and the atmosphere on
the other hand has been represented /­Andersson 2010/.
The radionuclide model has the same mathematical formulation for all biosphere objects. The differences between biosphere objects have been captured by using object-specific values for parametersdescribing the geometry of the biosphere objects, the depths of regolith layers, and the rate andtiming of transitions between sea, lake and terrestrial stages.

8.5

Estimating activity concentrations

The radionuclide model simulates the radionuclide inventory (Bq) dynamically in ten compartmentsof the biosphere object (Figure 8-1). From these, the activity concentrations in the upper regolith(peat, agricultural soil, aquatic sediments), in the atmosphere and in the surface water are calculated.
Environmental concentrations are used to assess the impact on non-human biota (Chapter 11) and to
calculate human exposure (see the following sections).
Environmental activity concentrations in regolith and surface water (Bq/kg dw or Bq/m3) are calculated by dividing the inventory of the compartment with the mass (for regolith) or the volume (waterand atmosphere) of the compartment. The activity concentrations in atmospheric air (Bq/m3), due todust are calculated by multiplying the activity concentrations in terrestrial regolith (Bq/kg dw) by
the dust concentrations (kg dw/m3) in air /­Andersson 2010/.
The initial inventory in agricultural soil (Bq) is calculated by summing the radionuclide inventories
in the upper terrestrial regolith compartment and in 25 cm of the middle terrestrial compartment(representing depth of ploughing). The average inventory in the agricultural soil during a period of
50 years is then calculated assuming leaching due to runoff. For vegetables, additional input via contaminated irrigation with surface water is taken into account. The activity concentration (Bq/kg dw)
in soil is obtained by dividing the average radionuclide inventory by the soil mass (kg dw), which isthe product of agricultural soil density (kg dw/m3) and ploughing depth (m) /­Andersson 2010/.
The activity concentrations in human foods (Bq/kg C) are calculated from concentrations in environmental media (upper regolith and surface water), assuming equilibrium between the concentrations infood and in the corresponding environmental media. For aquatic food (e.g fish, crayfish and mussels),
the activity concentrations are calculated by multiplying the activity concentration in water with theconcentration ratio (Bq/kg C per Bq/m3) for each food item, respectively. For terrestrial food, activity
concentrations are calculated by multiplying the activity concentration in upper regolith (peat or agricultural soil) with the corresponding concentration ratios (Bq/kg C per Bq/kg dw) /­Nordén et al. 2010/.
To determine the activity concentration in meat from game and cattle and in dairy products, theconcentrations in the animal diet (wetland vegetation or green fodder) are first calculated by multiplying activity concentrations in upper regolith with the corresponding concentration ratios (Bq/kg C
per Bq/kg dw). Activity concentrations in meat and milk are then calculated from the concentrationsin animal diet and animal consumption rates, using equilibrium models. Radionuclide intake fromcontaminated water and ingestion of soil are also included in these calculations /­Nordén et al. 2010/.

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8.6

Assessment of human exposure

The activity concentrations in environmental media are used to assess human exposure. For theseassessments, it is assumed that a representative individual of the most exposed group spends all timein the contaminated biosphere object, and gets his or her full demand of food and water from thatbiosphere object (Section 8.3).
In the SR-Site biosphere analysis, the average exposure over the lifetime of individuals that will
live in the Forsmark area in the far future is assessed. For this assessment, adults were considered toprovide a sufficiently good approximation of the average exposure during a lifetime. This is in linewith the ICRP recommendations /­ICRP 2000, ICRP 2006/.
To estimate annual exposure during the lifetime of an individual, predicted doses have been averaged
over a period of 50 years, which is the integration period used by ICRP in the derivation of dosecoefficients for adults. Exposures have been calculated following the methods outlined in /­Avila andBergström 2006/, summing the contributions from all relevant pathways. Below is a brief description of
the assumptions made in the calculations of human exposure from inhalation, external irradiation, andconsumption of contaminated food and water. A detailed description can be found in /­Avila et al. 2010/.

8.6.1 Exposures via inhalation and external irradiation
To calculate exposure from inhalation and external irradiation, it was assumed that the human inhabitants are subjected to a constant exposure. Shielding by buildings is assumed to be negligible. Annual
doses by inhalation (Sv) are calculated by multiplying the activity concentrations in air (Bq/m3) with
the inhalation rate (m3/h), the exposure time (h/y) and the dose coefficient for inhalation (Sv/Bq).
Annual doses from external irradiation (Sv) are calculated by multiplying volumetric concentrations
in peat and agricultural soil (Bq/m3) by the exposure time (h/y) and the dose coefficient for external
exposure (Sv/h per Bq/m3).
8.6.2 Exposures from consumption of contaminated water
To calculate exposure via ingestion of contaminated water it was assumed that future human inhabitants are equally likely to satisfy their need for drinking water from a well drilled into the rock andfrom the surface water. Doses via water ingestion (Sv/y) are calculated by multiplying the activity
concentration in drinking water (Bq/m3) by the water ingestion rate (m3/y) and the dose coefficientfor ingestion (Sv/Bq).
8.6.3 Exposure from food consumption
To calculate exposure via ingestion of contaminated food it was assumed that human inhabitants are
self-sustaining and utilise all available food sources in proportion to their productivity (Section 8.3).
Doses via food ingestion (Sv/y) are calculated by multiplying the activity concentration in food (Bq/kg
C) with the food ingestion rate (kg C/y), and the Dose Conversion Coefficient for ingestion (Sv/Bq).

8.7

Landscape dose conversion factors

In SR-Site, doses to humans are assessed by multiplying release rates or instant releases to the biosphereby landscape dose conversion factors (LDFs). Two different LDFs were derived: i) LDFs that are
applicable to continuous long-term releases at a constant rate, and ii) modified LDFs for pulse releases
that are applicable for releases of radionuclides that reach the biosphere as a pulse with a duration ofyears or hundreds of years. The definition of these LDFs is provided below and details on how they
have been derived are given in /­Avila et al. 2010/.

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8.7.1 LDF and modified LDF for pulse release
Initial simulations demonstrated that LDF values which represent the maximum doses across all biosphere objects did not depend on surface water transfer between objects (Section 13.3.1 and /­Avila
et al. 2010/). Thus to simplify calculations the LDF and the modified LDF for pulse release were
calculated by running the radionuclide model for each biosphere object separately. The LDF for eachpotentially released radionuclide is defined as the mean annual dose to a representative individualfrom the most exposed group resulting from a constant unit release rate of this radionuclide. The
exposure is averaged over the lifetime of an individual, and the units of the LDFs are Sv/y per Bq/y.
The modified LDF for pulse releases for each potentially released radionuclide is defined as themean annual dose to a representative individual from the most exposed group, resulting from a unit
pulse release of this radionuclide. The exposure is averaged over the lifetime of an individual, andthe units of the modified LDF for a pulse are Sv/y per Bq.

8.7.2 LDF values for different climatic conditions
LDF values were calculated for three different periods of the reference glacial cycle; a period ofsubmerged conditions following the deglaciation, the whole interglacial period, and a prolonged
period of periglacial conditions /­Avila et al. 2010/. Additionally, LDFs were calculated for the
global warming climate case. The modified LDF values for a pulse release were calculated for theinterglacial period only.
The calculation period starts at the time for the deglaciation around 9000 BC, when the landscapeexperiences submerged conditions. The length of the submerged period differs between biosphereobjects since it takes about 12,000 years from the emergence of the first biosphere object until thelast marine embayment is turned into a lake (Section 6.2.5). During submerge conditions consumption of contaminated sea-food is the only considered exposure pathway.
The initial period of temperate climate domain, i.e. the period from deglaciation to the onset of
periglacial domain (Section 6.2.1), is represented by climate conditions similar to those of today
and is, in accordance with the reference glacial cycle, assumed to prevail for 18,400 years (i.e. from
–9000 to 9400 AD). As land has emerged sufficiently from the sea, wetlands are assumed to beconverted to arable land. Drinking water for humans and livestock during the terrestrial stage of thisperiod is supplied in equal parts from surface water and from a contaminated well drilled into the
bedrock (Section 8.3.4).
The initial period of temperate climate conditions is followed by a period of periglacial conditionsin the reference glacial cycle. For the LDF calculation, periglacial conditions are assumed to prevail
until the onset of the next glaciation around 60,000 AD. During this period, it is assumed that agriculture is not possible, and drinking water from a contaminated deep drilled well is not accessible /­Avila
et al. 2010/.
Permafrost will prevent discharge of deep groundwater to most lakes and wetlands in the area during
periods of a periglacial domain, and an expected decrease in runoff will reduce surface water fluxes
in lakes where discharge occurs /­Bosson et al. 2010/. This will result in lower or no radionuclide
releases to most biosphere objects. Permafrost conditions will also result in changes in the terrestrial
vegetation community and in primary production. The effects of permafrost conditions on LDF
values were studied by alternative simulations, which are described in /­Avila et al. 2010/ and further
discussed in Section 9.3.1.
Releases to the biosphere under glacial conditions, when the site is covered by an ice sheet, areunlikely to give exposure to humans. Humans might be exposed to radionuclides through ingestionof sea food when the ice margin is situated close to the repository. As a cautious estimate of the
exposure from releases during glacial conditions, the LDFs from the time when isolation of the sea
basin starts are used in the assessment.
In the SR-Site global warming climate case, it is assumed that the temperate climate domain isextended with approximately 50,000 years as compared with the reference glacial cycle (i.e. the temperate
climate domain prevails until 60,000 AD (Section 5.1 in Climate report). Human utilisation of

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natural resources under this extended period of non-glacial conditions is assumed to be similar tothat of the inter-glacial period, i.e. wetlands are converted to arable land when possible, and drinking
water for humans and livestock is supplied by surface water and water from a contaminated well drilled
through bedrock.

8.8

Software implementation

The radionuclide model was implemented in the software package Pandora /­Åstrand et al. 2005,
Ekström 2011/. Pandora is an extension of the codes Matlab and Simulink /­http://www.mathworks.
com/. The tool is described in detail in /­Ekström 2011/. Below is a brief description of the development, functionality and features of the Pandora tool.
Pandora was developed by Facilia AB togheter with SKB for the specific needs of the biospheremodelling, and it has been used by SKB and Posiva OY for their safety assessments of high level waste
repositories. Pandora supports solution of systems of ODEs using numerical methods that are appropriate for solving stiff and non-stiff problems, and has all required functionalities for such biosphereassessments, including handling of large sets of parameters, handling of time-evolving parameters,
representation of discrete transitions between states, handling of large numbers of radionuclides anddecay chains, and performance of probabilistic simulations.
Pandora also simplifies the development of compartment models consisting of large systems ofordinary differential equations and the handling of radionuclide decay chains. The tool comprises alibrary of Simulink blocks that facilitates the creation of compartment models, a Manager that aids
the model building, and a standalone assessment tool called Pandas.
Pandora extends the Simulink graphical user interface to allow the user to easily inspect andmodify the conceptual and mathematical models implemented. Since Pandora is integrated withthe assessment tool Pandas, it facilitates performance of sensitivity and uncertainty analyses of theimplemented models.
Pandora has been benchmarked, tested and compared with other similar tools /­Åstrand et al. 2005/
and /­Ekström 2011/. The solutions with the predecessor of Pandora (Tensit) were compared withanalytical results, as well as with numerical results obtained with other simulation tools /­Jones et al.
2004, Jones et al. 2005/. These comparisons have shown that Pandora provides reliable solutions.

8.9

Quality assurance

Controlled handling of data and workflow is crucial to guarantee the quality of data and model
results. Consequently, SR-Site Biosphere follows the quality assurance plan that has been developed
for the SR-Site project (see Section 2.9 in SR-Site Main Report). In addition, tools and routines tomaintain a high quality in the daily workflow were developed within the biosphere project. Theseroutines include the use of version and tracking systems, controlled handling and delivery of data,
and reasonability assessment of model results.

8.9.1 Version handling and tracking systems
To secure full traceability in the daily work, with data, modelling, and production of reports, andin the handling of issues in the project, a sophisticated version handling system was integrated(SubVersion, /­http://svnbook.red-bean.com/) with an errand tracking system (Trac, /­http://trac.
edgewall.org/) in SR-Site Biosphere project.
Thus storage and updates of parameters, models, results, and reports were handled with SubVersion,
keeping a full record from data sources (e.g. SDM data, scientific results, new calculations, and GIS
manipulations) to delivery in SKB doc (e.g. final report text) or the GIS database (GIS projects).
SubVersion was also used as a secure backup system, keeping a complete track of the time and user
responsible for updating a file. Moreover, with this system the calculation environment that produced
a specific result can always be reconstructed, disregarding later changes in codes or input data.
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Trac is an issue tracking system, which was used to track delivery and control of data and simulation results, and to file related issues. The system was also used to document issues from reviewsof earlier safety assessments (SR-Can, SAR08) and how they were handled in SR-Site.

8.9.2 Handling of primary and generic data
All primary data collected in the field are stored in the SKB databases Sicada and SKB-GIS. The
delivery of data to the databases are specified in the SKB QA document SDK-508 and involves
several steps with review of data to ensure quality and to eliminate mistakes introduced by datatransfer. In SR-Site, approved (signed) tables from the Sicada and SKB GIS databases were the only
sources for primary data collected at the site. All orders and data deliveries were registered, andfollowed SKBs quality assurance system.
The quality of information from sources other than the previous SKB site investigation phase wasalso assessed. The generic data were treated in standard scientific manner and traceability secured byreferences to the literature from where the information was gathered. In the large literature datasetscollected from the database EMRAS, a quality check was performed to guarantee that data werecorrectly transferred to the parameter files used in the radionuclide model /­Nordén et al. 2010/.

8.9.3 Handling of parameters to the radionuclide model
To allow simulations with a minimum of interference with the source data, correct and consistentparameter files were delivered to a pre-specified location in SubVersion. The format and content of
the parameter-files were assessed by the deliverer, an independent reviewer and by the modeler. A
ticket in the tracking system Trac accompanied the delivery of each file, and modifications made to
the parameter files were documented on the ticket and in the logbook in Subversion.
In short, format according to existing specifications, and completeness and correctness of data, werechecked by the deliverer. A reviewer panel checked the reasonablility of data with respect to themagnitude of values, parameter correlations and parameter time dependencies. Finally, the modeller
confirmed that the file contained sufficient data for successful simulations.When mistakes or inconsistencies were detectected, the file was reassigned to the deliverer and the original file was updated andthe procedure started over again.

8.9.4 Handling of results
To verify results from the Pandora simulations, the radionuclide model was also implemented in
Ecolego. The simulation results obtained with the two packages were practically identical /­Avila
et al. 2010/.
The reasonability of model results with respect to transport and accumulation of radionuclides
was assessed by subject-matter experts. For example, the changes of radionuclide inventories andconcentrations over time were evaluated in relation to parameters describing the development of thelandscape (e.g. geometric and regolith parameters), stage transitions (sea to lake transition) and thedevelopment of aquatic and terrestrial ecosystems (e.g. biomass, production and decomposition).
The consistency in behaviour of nuclides and elements with similar properties were also assessed.

TR-10-0999

9

Data for assessment

SR-Site has a unique position to include site data in the biosphere assessment. Site data describes
both important ecological and hydrological processes as well providing concentrations of elements
in site specific organisms, regolith and waters, together with a high resolution DEM and a detailed
stratigraphy of the regolith /­SKB 2008/. This dataset is probably the most detailed collection of synchronised surface data ever produced in Sweden. Moreover, site investigations of the two candidate
sites Forsmark and Laxemar-Simpevarp were coordinated, which gives valuable possibilities tovalidate data and build confidence. The radionuclide model for the biosphere has, as far as possible,
utilised the site specific data both for describing parameters and populating parameter values.
The radionuclide model for the biosphere presented in Chapter 8 relies on nearly 140 input
parameters, of which one third represent radionuclide- or element-specific properties. For eachparameter, a best estimate was derived from site and/or literature data, and the parameter uncertainty
was described by a probability density function (PDF). The best estimate was used for deterministic
calculations of human exposure (Chapter 10) and to assess potential radiological impacts on theenvironment (Chapter 11).
To identify model parameters with a large influence on exposure estimates, and to assess the precision of these estimates, probabilistic simulations with the radionuclide model were also performed.
For these calculations, parameter values were randomly varied according to their PDFs. In order tosummarise the number and types of parameters that are used to model transport and accumulationof radionuclides in the biosphere and the potential exposure to organisms, the parameters have been
divided into a number of categories (Table 9‑1).
The parameters used in the radionuclide model reflect important processes relating to transport,
accumulation and exposure to radionuclides at the site over time, thus including the effects of site
development. This chapter starts with a description of the principles and methods used to selectparameter values that represent the site and to determine PDFs that represent the natural variationand the uncertainties associated with the selected parameter values (Section 9.1). The bulk of thechapter is devoted to describing the parameters in the context of the categories (Section 9.2), and in
the last section (Section 9.3) parameterisations for different climatic conditions are discussed.

9.1

Methods for selecting parameter values and probability
density functions

The extensive site investigations performed by SKB at Forsmark have resulted in a detailed description of the site and its development (Chapters 5 and 6). Data from this description have been the
primary source for parameter values of the radionuclide model. Below is a brief description of theprinciples used to derive typical values of input parameters, and to describe the natural variation andmeasurement uncertainties in model parameter values. When the available site data were insufficient
for reliable parameter estimation, site data were combined with data from the open literature. The
procedures used to combine site and literature data when calculating concentration ratios is describedin a separate section (Section 9.1.2).

9.1.1 Principles and uncertainties in parameterisation
For each parameter describing a property or process in biosphere objects, a best estimate has been
derived from site and/or literature data, and the parameter variation has been described by a probability
density function (PDF). Objects develop in time, but for the purpose of the assessment the properties
within an object are assessed to be homogenous and to represent a yearly average. Thus, the parametervalues that are used in the simulations of transport, accumulation and exposure, should give representative descriptions (typical) of compartments or flows between compartments within a biosphere object,disregarding spatial variation within the compartments, and temporal variations within a year. Thismeans that when the distributions of parameters values are given (e.g. standard deviation, max, min),TR-10-09

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Table 9‑1. Parameters used in the radionuclide model. a each parameter estimated for 48 radionuclides, b each parameter estimated for 31 stable elements, c time-dependent parameters forwhich a separate parameter value is given for each time step and object (8 landscape geometry
parameters, 4 regolith parameters, 8 aquatic ecosystem parameters and 1 surface hydrology andwater exchange parameter). Total number of parameters listed in parenthesis. The references are
given in the footnote below the table.
Type of parameter

Nuclide specificN

SectionExampleSourceReference

Literature

TR-10-071

9.2.1

Radionuclide half life

Landscape geometriesc

13

9.2.2

Size of biosphere objects
Siteand catchment areas, sedi- investigation,
mentation and resuspension site modellingrates

TR-10-05

Regolith propertiesc

27

9.2.3

Depth, density and porosityof sediments and soil

Siteinvestigation,site modelling

TR-10-01, TR-10-02,
TR-10-03, TR-10-05

Aquatic ecosystempropertiesc

17

9.2.4

Biomass, productivity, gas
exchange

Siteinvestigation,site modelling

TR-10-02, TR-10-03

Terrestrial ecosytem
properties

34

9.2.4

Biomass, productivity, gas
exchange

Siteinvestigation,site modelling

TR-10-01,TR-10-07

Surface hydrology andwater exchangec

9

9.2.5

Runoff, vertical andhorizontal advective fluxes,
marine water exchange

Siteinvestigation,site modelling

TR-10-01, TR-10-02,
TR-10-03

Distribution coefficientsand diffusivityb

10

9.2.6

Element-specific solid/liquid
distribution coefficients (Kd)for regolith and particulatematterSiteinvestigation,
literature

TR-10-07

Concentration ratios,
retention and releaseb

19

9.2.7

Element-specific ratios
between environmental
media and organisms (CR)Siteinvestigation,
literature

TR-10-07

Human characteristics

5

9.2.8

Life span, energy and water Literature
consumption

TR-10-07

Dose coefficientsa

4

9.2.8

Radionuclide-specificfactors for radiation
exposure through external
exposure, inhalation andingestion

TR-10-07a

Literature

References:
TR-10-01: /­Löfgren 2010/
TR-10-02: /­Andersson 2010/
TR-10-03: /­Aquilonius 2010/
TR-10-05: /­Lindborg 2010/
TR-10-07: /­Nordén et al. 2010/

these should reflect the random variation of the typical value between years, or, if such data are notavailable, the random variation between compartments in similar landscape objects within the study
area. Only the natural variation existing within a climate domain is used to characterize the probability
distribution of a parameter.
The term “parameter uncertainty” is used in the context of assessing the precision of estimated LDFs.
The parameter uncertainty refers to the sum of natural variation, comprising variation due to real andidentifiable heterogeneity in nature and measurement uncertainties (i.e. errors in measurement or
limitations in the assessment).
Each parameter has been described by a best estimate and a probability density function (PDF),
which includes both natural variation and measurement uncertainties. The shape of the PDF for eachparameter was judged to be either log-normal or normal. For a lognormal distribution, the geometricmean and standard deviation were used to describe the best estimate and the variation around themean whereas the arithmetic mean and standard deviation were used for parameters with a normal
distribution. For each parameter, maximum and minimum values were also identified to set limits on
the possible range of the parameter value. The possible range includes expected natural variation that102

TR-10-09

is not observed at the site presently, but may historically have existed at the site or is expected in the
future under similar climate conditions (e.g. presence/characteristics of species/communities that arelikely to develop on the site, but are not presently observed).
When data were insufficient to estimate a parameter distribution (e.g. for properties of future site
conditions estimated from literature data) the parameter was represented with a uniform distribution.
For most of these parameters, the best estimate corresponded to the arithmetic mean of the min andmax values.

9.1.2 Estimating concentration ratios from site and literature data
In the radionuclide model, distribution coefficients (Kd) and concentration ratios (CR) are used todescribe radionuclide retention and biological uptake. In previous safety assessment /­SR-Can main
report/ literature data were used to derive the parameter values. In the SR-Site safety assessment,
sufficient site-specific data for calculations of many distribution coefficients and concentration ratios
were available in varying degrees for most elements of interest. The method to derive element ratios
varied with the availability of site and literature data.
When site-specific data were available, but representative literature data could not be found, best
estimates and PDFs were derived from the site data only, assuming a log-normal distribution. Whenboth site-specific and literature data were available, Bayesian inference methods were used to derive
best-estimate values and PDFs by combining the site and literature data /­Nordén et al. 2010/. Literature
data were primarily retrieved through the EMRAS and ERICA databases /­IAEA 2010, Beresford et al.
2007/. Where data were missing in these databases, parameter values compiled for previous SKB
safety assessments were used /­Karlsson and Bergström 2002/.
For a few elements, appropriate data were not available from the site or from the open literature.
In these cases, data for other biota types or analogue elements were used to derive best estimatesand PDFs for model parameters. Concentration ratios for herbivores were derived from a kineticallometric model /­Nordén et al. 2010/. A detailed description of the methods used to derive best
estimates and PDFs for element ratios is presented in /­Nordén et al. 2010/.

9.2

Description of model parameters

Parameters used in the radionuclide model have been divided into 10 categories that are described
below. In addition, all parameters are listed in Appendix 2 where there are references to reports inwhich the parameter calculations are described and in which files they have been delivered to theradionuclide modelling.

9.2.1 Nuclide specific parameters
This parameter category contains parameters connected to radioactive decay. Forty radionuclides
were considered in the biosphere assessment of SR-Site. The half-life, dominant radiation typefrom decay and the decay chains considered in the assessment are presented below (Table 9‑2). The
data were taken from (Firestone and Ekström 1999. www table of radioactive isotopes, version 2.1[Online]. Available at http://ie.lbl.gov/toi/).
9.2.2 Landscape geometries
The continuous temporal development of the landscape results in time-specific volumes and areas ofobjects and surrounding catchments, and determines the type of ecosystem at different time steps in
the model (i.e. terrestrial or aquatic). The geometric parameters describe geometric extensions (i.e.
areas and depths) and sediment parameters as well as transition times for different ecosystem stages,
e.g. the time of transition between marine and limnic stages.

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Table 9‑2. Radionuclides considered in SR-Site safety assessment. Half-life and the decay chainsconsidered in the safety assessment are listed.
NuclideHalf-life (y)Ac-227
Ag-108m
Am-2414.32 · 10

Am-242m

1.41 · 102

Decay chain

NuclideHalf-life (y)2.18 · 10

Pa-231

3.28 · 10

4.18 · 102

Pb-2102.23 · 104

Pd-107

6.50 · 106

Po-2104.00 · 10–1

Pu-2381.90 · 10

Decay chain4

2

Am-243–>Pu-239–>U-235–>Pa-231

Am-243

7.37 · 10

C-14

5.73 · 103

Pu-2392.41 · 104

Ca-41

1.03 · 105

Pu-2406.56 · 103

Cd-113m

1.41 · 10

Pu-242

3.73 · 105

Cl-36

3.01 · 105

Ra-2261.60 · 103

Cm-2441.81 · 10

Se-79

1.13 · 10

Cm-2458.50 · 10

Sm-1519.00 · 10

Cm-2464.73 · 103

Sn-121m

5.50 · 10

Cs-1352.30 · 10

Sn-1261.00 · 105

Cs-1373.01 · 10

Sr-90

2.88 · 10

Eu-1521.35 · 10

Tc-99

2.11 · 105

H-3

1.23 · 10

3

3

6

Pb-210–>Po-210–17

Ra-226–>Pb-210–>Po-210

6Th-2297.34 · 103

Ho-166m

1.20 · 103

Th-2307.54 · 104

I-129

1.57 · 107

Th-232

1.41 · 1010

Mo-93

4.00 · 103

U-233

1.59 · 105

U-233->Th-229

Nb-93m1.61 · 10U-234

2.46 · 105

U-234–>Th-230–>Ra-226–>Pb-210–>Po-210

Nb-94

2.03 · 104

U-235

7.04 · 108

U-235–>Pa-231

Ni-59

7.60 · 10

4

U-236

2.34 · 10

Ni-63

1.00 · 102

U-238

4.47 · 109

Np-2372.14 · 106

Zr-93

1.53 · 106

Th-230–>Ra-226–>Pb-210–>Po-2107

U-238–>U-234–>Th-230–>Ra-226–>Pb-210–>Po-210

Geometric extensions

The geometric extensions of the biosphere objects were calculated in a coupled regolith-lake development model (RLDM) for Forsmark /­Brydsten and Strömgren 2010/. The outputs from the model wereareas of the biosphere objects (Aqu_area_obj and Ter_area_obj), average and maximum depths of theaquatic object (depth_aver and depth_max) and areas of watersheds and sub-catchments (area_wshed
and area_subcatch). These parameters changes over time due to shoreline displacement and ecosystem
succession (Chapter 6).
The outer boundary for each biosphere object during submerged conditions was determined fromthe bathymetry of the sea basin, whereas the shoreline of the lake at the time of isolation from the sea
delineates the biosphere object during the lake and terrestrial stages. For the majority of the objects,
the wetland in the terrestrial stage is drained by a small stream. The morphometry of the stream
flowing through the wetland is calculated based on stream length and stream width/depth/crosssection geometry /­Lindborg 2010/.
Sediment parameters

Parameters representing sedimentation processes in aquatic ecosystems were calculated by the
RLDM. Sedimentation (sed_rate) represents the amount of particulate matter that is deposited onlake and sea bottoms in a year. Some of this material will accumulate permanently (growth_rego)

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and some will be resuspended and return to the water column (res_rate). In streams, resuspension
is set to the same value as modelled sedimentation, and accumulated material is set to zero, i.e. all
sedimented material is assumed to be transported further downstream /­Andersson 2010/.
Transition times

Due to shore line displacement, sea bays are isolated and transformed into lakes or streams surrounded
by wetlands, or directly into a wetland. The isolation of a lake from a sea bay in the Forsmark area takes
approximately 500 years /­Lindborg 2010/, and during the transitional stage the values of the aquaticmodel parameters change linear in time from sea to lake values. The isolation starts (threshold_start)
when the basin is isolated from the adjacent marine areas for at least part of the year and isolation ends
(threshold_stop) when there are no saltwater intrusions to the lake basin even at high sea water levels.
As soon as a lake is formed, it starts to get infilled and is gradually transformed into a wetland. The
time (threshold_end) when the entire lake is infilled (in most cases a stream remains) was modelled
for each object. In the radionuclide model, it is assumed that when a mire object is located 2 m above
sea level, it can be drained and used for agriculture /­Lindborg 2010/.

9.2.3 Regolith
The regolith parameters describe properties of different generalized geological units found in thebiosphere objects. The regolith in each biosphere object is described according to the conceptualmodel of the spatial distribution of regolith at Forsmark (Figure 9‑1) based on the surface map ofregolith, the regolith depth model (RDM) /­Hedenström et al. 2008/, the soil type map /­Lundin et al.
2004/ and the RLDM /­Brydsten and Strömgren 2010/.

Agricultural land
Mire
Lake

Parameter nameRegolith nameBiosphere object
AgriregoUpregomid_PG

Ter (mire)

Lake

Sea

Biological active layer(part of peat/sediment)
Post glacial deposits(gyttja/clay gyttja)

regomid_GL

Glacial clay

regoLow

Till

-

Sea

Bedrock
Successional trajectory

Figure 9‑1. Conceptual model of generalized distribution of regolith for different types of biosphere objects
at Forsmark. The different depths of the various regolith layers in profiles are also seen in the landscapepictures, which represent a generalized succession trajectory from sea to wetland that is later converted toagricultural land by draining. In the radionuclide model, the postglacial and glacial clay deposits are
combined in regard to the radionuclide inventory.

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The regolith is divided into four layers: regoUp, regoMid_PG, regoMid_GL and regoLow. In theradionuclide model, RegoMid_PG (i.e. gyttja and clay gyttja) and regoMid_Gl (glacial clay) are
combined into one layer, regoMid (Figure 9‑1).
Depths of the regolith layers

The upper regolith is defined as the bioactive layer and the thickness of this layer differs between
ecosystem types. In aquatic ecosystems, the upper regolith is defined as the oxygenated upper sediments where bioturbation occurs. The marine parameter value (Sea_z_regoUp) is taken from literatureand is a mean for the Baltic Sea /­Aquilonius 2010/ whereas the limnic parameter value is calculated
from site measurements in Forsmark /­Andersson 2010/.The upper regolith in wetlands (Ter_z_
regoUp) represents the peat layer and the peat ingrowth is modelled using the RLDM /­Brydsten and
Strömgren 2010/ (Chapter 6). In agricultural land, the bioactive layer represents the thickness of thecultivated soil layer that is regularly ploughed (taken from literature) /­Löfgren 2010/.
Depths of organic and inorganic postglacial deposits (Aqu_z_rego_pg and Ter_z_regoMid_pg) changeover time and are modeled in the RLDM for each time step and object used in the radionuclide model.
The depth and distribution of the glacial clay (z_regoMid_gl_basin and Aqu_z_regoMid_gl_lake),and till (Sea_z_regoLow, Lake_z_regoLow), on the other hand, are regarded as constant over time.
However, the depth of the glacial clay and till layers varies in the landscape and is specific for eachobject, based on the RDM /­Hedenström et al. 2008/.
Density and porosity

The density and porosity of the upper regolith, differs between ecosystems. The density and porosityof the upper regolith in aquatic ecosystems (Aqu_dens_regoUp and Aqu_poro_regoUp) are basedon measurements of the water content and organic carbon content of sediments from both limnic
and coastal surface samples at Forsmark. The dry bulk density and porosity of wetlands (Ter_dens_
regoUp and Ter_poro_regoUp) are taken from site measurements from several depths in one mire in
the Forsmark area /­Löfgren 2010/. Density and porosity of drained wetlands, which are assumed to
be used for cultivation (Agri_dens_regoUp and Agri_poro_regoUp) are based on literature data fororganic soils.
In the middle and lower regolith layers, the same density and porosity parameter values are used
for aquatic and terrestrial ecosystems. The dry bulk density and porosity of postglacial deposits
and glacial clay in aquatic and terrestrial regolith (Aqu_dens_regoMid_pg, Ter_dens_regoMid_pg,
Aqu_dens_regoMid_gl, Ter_dens_regoMid_gl, Aqu_poro_regoMid_pg, Ter_poro_regoMid_pg,
Aqu_poro_regoMid_gl, Ter_poro_regoMid_gl) are based on site measurements in lakes and marine
basins at Forsmark. The parameter values of dry bulk density and porosity of the lower regolith(dens_rego_low, poro_regoLow) are based on site-specific measurements, at varying depths in thetill at four terrestrial localities.

9.2.4 Ecosystem properties
The ecosystem parameters describe relevant properties of aquatic and terrestrial ecosystems in the
Forsmark area today and in the future. It is not possible to predict species composition in a fully
dynamic future ecosystem in detail, and instead data from the site and nearby ecosystems are usedas natural analogues for the future ecosystems. This is based on the assumption that all relevantinteractions among species and between organisms and the abiotic environment are contained inthese analogue ecosystems.
Aquatic ecosystems

Aquatic ecosystems include marine, lake and stream stages of the aquatic objects. Lakes and marine
basins are parameterised with site data, i.e. with data from brackish marine basins and oligotrophic hardwater lakes at Forsmark today. The maximum and minimum parameter values were selected to coverchanges that may be induced due to altered salinity in the marine basins, and altered nutrient conditionsin the oligotrophic lakes. Ecosystem properties include chemical and biological parameters, as well as
parameters connected to human utilisation of the ecosystem. The ecosystem properties parameters forlimnic and marine ecosystems are fully described in /­Andersson 2010, Aquilonius 2010/.
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Biological parameters
Biomass and production of biota in the aquatic ecosystems are calculated for three categories, 1) the
pelagic community (Aqu_biom_pp_plank, Aqu_prod_pp_plank), 2) the benthic macro community(Aqu_biom_pp_macro, Aqu_prod_pp_macro ), and 3) the benthic micro community (Aqu_biom_pp_
ubent, Aqu_prod_pp_ubent ). Biomasses include both primary producers and consumers. Production is
the net ecosystem productivity (NEP) and is calculated as the difference between primary production
and respiration. Biota incorporate radionuclides during primary production and the production excess(i.e. the NEP) settles on the lake floor as sediment or is transported to downstream objects. Biomass
and net ecosystem production are based on site investigations together with modelling of the future
depth distribution of the aquatic objects. The major factors affecting biomass and production of thebiotic community in aquatic ecosystems are water depth and light penetration, and thus biomass andproduction parameters change over time due to landscape development.
Chemical parameters
Chemical parameters include concentrations of particulate matter and inorganic carbon as well
as fluxes of carbon dioxide gas across the air-water interface. Parameter values of concentrationsof particulate matter (conc_PM) and dissolved inorganic carbon (conc_DIC) are annual averages
calculated from site-specific measurements in lakes and in the sea.
There is equilibrium of CO2 between air and surface waters resulting in a flux of carbon dioxide
upon primary production (consuming CO2) or respiration (releasing CO2) in water bodies. Thereby,
primary production and respiration in aquatic ecosystems result in a flux of C-14, across the air-waterinterface. For other radionuclides and their analogues, this flux is considered to be small or insignificant. The CO2- flux is related to primary production and gas influx (gasUptake_C) and is calculated
for the aquatic objects as a proportion of net primary production. The data for NPP are based onsite-specific measurements and modelling of future objects. Gas outflow from the aquatic objects(Aqu_degass_C) were calculated by assuming a mass balance for the ecosystem, i.e. the amount ofcarbon entering the system must be the same as the amount of carbon leaving the system.
Parameters related to human utilization of the ecosystem
The production in aquatic ecosystems that can be sustainably harvested is parameterised in orderto evaluate the potential utilisation of ecosystems. It is assumed that fish, mussels, and crayfish areorganisms normally consumed from the aquatic ecosystems by humans. Fish production that can besustainably harvested (prod_edib_fish_Sea and prod_edib_fish_Lake) was estimated based on sitedata on fish sizes and conversion factors from literature. Parameter values for crayfish in future lakes
were estimated based on literature, but crayfish are assumed not to occur in the future marine basins.
Fish and crayfish are sensitive to shallow water depths (and effects of this, such as poor oxygen conditions and habitat type) and constraints were introduced that only allow fish and crayfish in lakes withcertain minimum depth (z_min_prod_edib_fish_Lake, and z_min_prod_edib_crayfish_Lake). Basedon literature and knowledge from the site, filter feeders are assumed not to be part of the diet fromaquatic ecosystems in Forsmark.
Terrestrial ecosystems

Terrestrial ecosystems include both agricultural land and wetlands. Wetlands are parameterised withdata from forested wetlands at Forsmark and Laxemar-Simpevarp. Ecosystem properties include
production and decomposition, fluxes between the terrestrial area and the atmosphere and fluxes
out of the system, as well as parameters connected with human utilisation of the ecosystem. Unlessotherwise stated in the text below, these parameters are fully described in /­Löfgren 2010/.
Biomass, production and decomposition
Biomass and production of primary producers in wetlands (Ter_biom_pp and Ter_prodBiom_pp)
include, vascular plants (including trees) and mosses and are calculated based on site data for three
localities, two of which are wetlands and one is a moist drained peatland with planted forest.

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The decomposition rate in wetlands (Ter_decomp), i.e. the amount of litter that is respired each year, isestimated based on long-term (1,600 years) mean accumulation from the bog Rönningarna in Forsmark/­Sternbeck et al. 2006/ by subtracting the mean accumulation in peat from the net primary productionof the median wetland. It was thereby assumed that the long-term accumulation in the vegetation wasclose to zero.
Fluxes of carbon between terrestrial area and the atmosphere
Fluxes of carbon between atmosphere and the terrestrial part of the ecosystem include release to theatmosphere from peat (upper regolith in wetlands), release to the atmosphere from decomposing
biota and uptake from the atmosphere by plants. The release from wetlands to the atmosphere is
calculated based on the concentration of carbon in the regolith (Ter_conc_C_regoUp) and the releaseof carbon as CO2 (Ter_degass_C). The release of CO2 is dependent on dissolved inorganic carbon
and pH, and this flux is based on literature conditioned by pH values of wetlands in Forsmark.
Decomposition of litter based on site data (see above) results in fluxes to the atmosphere and to dissolved inorganic and organic carbon in the soil. The fraction of decomposed carbon that is released
to the atmosphere (frac_C_atmos) was based on literature. Uptake of carbon from the atmosphereby plants is calculated based on biomass and production of primary producers (see above), carbon
concentration in the air (conc_C_atmos) and the height of the atmospheric layer from which CO2 istaken up by primary producers (Ter_z_mixlay).
C-14 is exported from the atmosphere above the terrestrial areas by wind exchange. The export wascalculated based on wind velocity (vel_wind), the height of the atmospheric layer where CO2 istaken up by vegetation (Ter_z_mixlay) and the zero displacement height of the wetland/agricultural
field (Ter_z_roughness, i.e. where the wind speed becomes zero when the wind profile above thecanopy is extrapolated down through vegetation). Wind velocities are site specific, whereas the otherparameters influencing the export are taken from literature /­Nordén et al. 2010/.
Parameters related to human utilization of the ecosystem
The production in terrestrial ecosystems that can be sustainably harvested is parameterised in theradionuclide model. In addition, humans are exposed to radionuclides by inhalation. Humans may
also influence exposure by activities such as irrigation.
From wetlands, the production of berries, mushrooms and game meat (prod_edib_berry, prod_edib_
mush, prod_edib_game) are taken to be consumed by humans. In addition to production of gamemeat, the fraction of mushrooms in the diet of terrestrial herbivores (frac_mush_Herbiv) has been
considered in the model. These parameters are based on both site data and literature.
From agricultural land, the production of domestic animals (prod_edib_meat and prod_edib_milk),
cereals (prod_edib_cereal), tubers (prod_edib_tuber) and vegetables (prod_edib_vegetab) are utilisedby humans. The production of domestic animals is dependent on fodder production (prod_fodder)which is also considered. These parameters are calculated based on literature and knowledge ofcommon crops and husbandry representative of the Forsmark region today.
Some characteristics of agricultural products are important for the exposure estimates in the radio­
nuclide model, i.e. carbon concentrations in milk and meat (conc_C_milk and conc_C_meat) and density of milk (densMilk). Leaf area index (leaf_areaIndex), based on literature values of the ratio of thetotal upper leaf surface of vegetation divided by the surface area of the plot and CR (see Section 9.2.7)
are used to calculate the concentrations of radionuclides in vegetables. Characteristics of products arefurther described in /­Nordén et al. 2010/.
Based on literature data, parameter values for ingestion rates of food, water and soil by dairy cattle
and beef cattle (ingRate_food_milk, ingRate_water_milk, ingRate_soil_Cow, ingRate_food_meat,
ingRate_water_meat) are included in the radionuclide model, described in /­Nordén et al. 2010/.
In order to estimate the human exposure to radionuclides due to inhalation of dust, the concentrationof dust in the air above agricultural land (Agri_conc_Dust) and wetlands (Ter_conc_Dust) were
included in the radionuclide model. These parameters are based on literature /­Nordén et al. 2010/.
The time spent in the agricultural and wetland areas is also important and is treated in Section 9.2.8.

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In the base case of SR-Site, irrigation of vegetables with surface water occurs during the time period
when agricultural practises are considered possible. The parameters used to describe irrigation are thetotal amount of water used per year (vol_irrig), the number of irrigation events per year (numb_irrig),
the leaf water storage capacity of the vegetation (leaf_StoreCapac) and an element-specific parameter
describing the retention on the vegetation surfaces (coefRetent, Section 9.2.7). All irrigation parameters are fully described in /­Nordén et al. 2010/.

9.2.5 Surface hydrology and water exchange
It is assumed that waterborne transport of radionuclides in the biosphere is proportional to the transport of water. Surface water fluxes in marine, terrestrial and limnic ecosystems have been modelled
and the capacity of a well above the repository has been estimated.
Water fluxes in the sea

The hydraulic residence time for the marine stages of objects (wat_ret), i.e. the average time a waterparcel spends within a given volume was calculated with a hydrodynamic model using external
forcing factors from the atmosphere, the surrounding sea and land runoff /­Karlsson et al. 2010/. The
estimates of these factors are based on site data from Forsmark. The major time-dependent forcing
factor influencing retention time in the models is the bathymetry (depth and shoreline), which was
determined from the DEM /­Brydsten 2006/.
In the sea, it is assumed that there is a net upward flux through the regolith layers (Sea_adv_low_mid), equal to the flux from the geosphere to the lowest regolith layer. This flux is assumed constantthrough the regolith layers because there is no influence of lateral surface fluxes like in lakes andterrestrial objects /­Bosson et al. 2010/. In the radionuclide model, it is assumed that there is no
influence of lateral advective fluxes in the marine biosphere object as in lakes, and therefore there
is no water flux between the regolith and surface water (i.e. sea_adv_mid_up is set to 0). However,there is a transport from sediments to water also in the marine basins caused by resuspension(Section 9.2.2) and diffusion (Section 9.2.6).
Water fluxes in lakes and terrestrial areas

The representation of the waterborne transport of radionuclides between compartments in the limnic andterrestrial ecosystems is based on detailed hydrological modelling with MIKE SHE /­Bosson et al. 2010/.
Water balances for today’s conditions have been analysed for different landscape objects and by simulating different time periods, i.e. different shoreline positions, regolith distribution, and climate cases,
the dynamics (i.e. the fluxes) of the groundwater and surface water in the future have been described/­Bosson et al. 2010/. MIKE SHE and the radionuclide model divide the ecosystem components somewhat differently and the outputs from water balances in MIKE SHE had to be transformed in order to fit
the set-up in the radionuclide model (Figure 9‑2). This is extensively described in /­Andersson 2010/.
In the model simulations, the radionuclide releases from the geosphere are directed to the lower regolith.
Thereafter a vertical flux from the lower regolith to the middle regolith (lake_ adv_low_mid) anddistribution of this flux between terrestrial area (i.e. wetland) and lake is calculated (fract_mire).
In the wetland, a flux from the middle regolith (i.e. post-glacial and glacial deposits) to the upper
regolith (i.e. peat) is calculated. The vertical fluxes between the lake water and sediment are assumed
to be equal in both directions. The same fluxes are used to represent the water exchange between the
top sediment (i.e. upper regolith) and the rest of the sediment (i.e. middle regolith layer). Thus, in theradionuclide model, the there is a flux from the middle regolith layer to surface water (Lake_Aqu_adv_
mid_up_norm).
The lateral fluxes between wetland and lake are calculated as functions of the sub-catchment areasof the object (area_subcatch) and the runoff (runoff) and by introducing a flooding coefficient(Flooding_coef). The runoff and flooding coefficient were estimated based on water balances in the
MIKE SHE SDM-Site model /­Bosson et al. 2008/.

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Mike She water balances
LAKE+MIRE
OL in
OL outMIRE

LAKE

Net precOL to L1 L1 to OL

Net prec

L1 in
L1 outMIRE

OL in
L1 to L2

L2 to L1

L2 in
L2 outL2 to L3 L3 to L2

OL out

L1 in
L1 out

L2 in
L2 outOL to L1

L1 to L2

L2 to L3

Water balance figure

OL

L1

L1 to OL

L2 to L1

L2 L3 to L2

Water fluxesin the Pandora model
Area_subcatchment · runoff ·(1 + Flooding_coef)

Area_watershed · runoff
Aqu_WATER

Area_subcatchment · runoff ·Flooding_coef

Area_subcatchment · runoff ·Aqu_adv_mid_up_norm

L3

Ter_REGOLITH_UP

Aqu_REGOLITH_UP

Area_subcatchment · runoff ·Aqu_adv_mid_up_norm

Area_subcatchment · runoff ·Ter_adv_mid_up_norm

Ter_REGOLITH_MID

Aqu_REGOLITH_MID

adv_low_mid · area_object · fract_mire

adv_low_mid · area_object · (1-fract_mire)

REGOLITH_LOW

Figure 9‑2. Detailed hydrological models are used to parameterise water fluxes between compartments in
the radionuclide model. Parameter names in bold are water fluxes described in Section 9.2.5.

Well capacity

The well capacity in the Forsmark area (wellCapac) is estimated based on site data from 22 percussion
boreholes /­Gentzschein et al. 2007/.

9.2.6 Distribution coefficients and diffusivity
In the radionuclide model, distribution coefficients (hereafter named Kd) and diffusivity are elementspecific parameters that are used in simulating the radionuclide transport in the deposits. The diffusivity(diffcoef) was used for calculation of the diffusion fluxes between different regolith compartments,
whereas Kd values are used to describe retention within the deposits. The Kd concept assumesa reversible, linear relationship between sorbed and dissolved species of an element in the soil,
sediments and particulate matter /­Tröjbom and Nordén 2010/. To include variations in Kd values
between sites with different local environments, in situ measurements from both Laxemar andForsmark, as well as literature data, have been used to assign the PDFs. The use of empirical in-situ
measurements also ensures that the effect of competing stable elements is included in the Kd values.
Kd values have been assigned for inorganic deposits (kD_regoLow) and organic deposits interrestrial and aquatic environments (Ter_kD_regoUp, Ter_kD_regoMid, Lake_kD_regoUp, Lake_
kD_regoMid, Sea_kD_regoUp and Sea_kD_regoMid) as well as for particulate matter in limnic
and marine environments (Sea_kD_PM, Lake_kD_PM). These parameters are further described in/­Nordén et al. 2010/.
When estimating Kd values, available site-specific data have been combined with literature data,
as described in Section 9.1.2. The reported parameter value ranges were often several orders ofmagnitude.
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9.2.7 Concentration ratios, retention and release
The modelled uptake of radionuclides in biota is described by concentration ratios (CR) in SR-Site.
The concentrations of different radionuclides in terrestrial vegetation (natural as well as crops) andmushrooms (cR_soilToPast, cR_soilToCereal, cR_soilToTuber, cR_soilToVegetab, Ter_cR_pp,
cR_soilToBerr, cR_soilToMush) were related to the corresponding concentrations in the soil whereas
concentrations in terrestrial herbivores (cR_foodToHerbiv) were related to concentrations in theirfood. For aquatic biota (Lake_cR_pp_plank, Lake_cR_pp_ubent, Lake_cR_pp_macro, cR_watToFish_Lake, cR_watToCray_Lake, Sea_cR_pp_plank, Sea_cR_pp_ubent, Sea_cR_pp_macro,cR_watToFish_Sea) the radionuclide concentrations were related to the corresponding concentrationsof the water in their habitat. These element-specific parameters are described in /­Nordén et al. 2010/.
Modelling plant uptake via CR factors reflects a reversible transport mechanism including both influxand efflux depending on the concentrations in plants and soil. The CR calculation approach assumes
a linear relationship between plant and soil concentrations /­Tröjbom and Nordén 2010/. To include
this variation, available site specific data have been combined with literature data when estimating
CR (Section 9.1.2). The reported parameter value ranges are often several orders of magnitude.
The retention of radionuclides supplied to vegetation surfaces as a consequence of irrigation bycontaminated water is described by an element-dependent retention factor (coefRetent). The values
used are those recommended in /­Bergström and Barkefors 2004/.
To describe the turnover of elements in terrestrial ecosystems, one parameter describing the behaviourof different elements during decomposition was used (Ter_df_decomp). The parameter gives thefraction of the element retained in the organic part of the litter compared with the amount present in
the dry mass. Elements were grouped into carbon-like elements or other elements according to patterns
identified in /­Brun et al. 2008/.

9.2.8 Human characteristics and dose coefficientsParameters that describe habits and characteristics of the exposed individual were primarily collectedfrom the literature. In SR-Site, these parameters include the amount of food and water consumed(ingRate_food and ingRate_water), inhalation rate (inhRate) and time spent in the contaminated area
(expTime), as well as dose coefficients for external exposure, inhalation, and ingestion of water andfood (dosCoef_ext, dosCoef_inhal, dosCoef_ing_water, dosCoef_ing_food).
The dose coefficients used in the dose calculations take into account retention of radionuclides in thehuman body and exposure from daughter radionuclides, as well as radiation sensitivities of different
tissues and organs. Doses calculated using these coefficients are committed effective doses, which
are appropriate for calculating the probability of harmful effects of ionizing radiation using the dose
to risk factors given in the Swedish regulation /­SSM 2008/.
In line with international recommendations /­ICRP 2006/, fixed, slightly conservative values werechosen for these parameters. Thus, these parameters were excluded from the probabilistic simulations,leaving the uncertainty distribution in LDFs to primarily reflect the environmental uncertainties.
The food consumption rate was expressed in kg carbon per year, since the total intake of carbon by
an individual is related to the food energy intake. The water consumption rate used did not include
the water contained in the food, since its contribution to man’s water balance is indirectly included in
the calculations of the internal dose from food ingestion. The inhalation rate and exposure time usedwere conservative (high) values.
The dose coefficients for ingestion and inhalation were taken from /­EU 1996/, whereas the values
for external exposure were taken from /­Eckerman and Leggett 1996/. These parameters are further
described in /­Nordén et al. 2010/. As recommended by the ICRP /­ICRP 2000/, only dose coefficientsfor adults have been used.

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9.3

Parameterisation at different climate stages

The biosphere safety assessment has been performed for the reference glacial cycle (including temperate, periglacial, and glacial climate and submerged conditions) and the global warming climate case
(Climate report). Descriptions of the Forsmark site for the different climate domains are presented in
Chapter 6 and how this has been considered in the safety assessment is described in Section 8.7.2.
The parameter description above refers to values for a temperate climate domain. For periglacial
climate domain, the state of the biosphere is expected to be similar to the temperate climate, with theadjustments that the agricultural pathways are omitted and that there are no wells. Other potential
implications, such as changed hydrology and altered parameter values, are considered in supporting
calculations (see below). In a similar way, the global warming climate case is treated as an extended
temperate climate and temperate parameterisation was prolonged up to year 60,000 AD in the calculations of LDFs. For warmer conditions (e.g. following global warming), production in terrestrial
areas is likely to increase, but no supporting calculations to investigate the effects of this on LDFs havebeen performed (Chapter 12 and in /­Löfgren 2010/). During periods of glaciation, it is possible that asmall human population could potentially utilise fish from the sea at the ice margin and the temperateparameterisation for the sea stage has been used to encompass this possibility. In summary, the only
case for which a different parameterisation has been used for other climate conditions than temperate
is for the supporting calculation performed for the periglacial climate domain (for a discussion of theresults of this simulation, see Chapter 12).

9.3.1 Periglacial parameterisation for supporting calculation
During a periglacial climate domain, the processes in the biosphere that affect transport, accumulation and exposure are expected to be altered in several ways. For example, permafrost will prevent
discharge of deep groundwater to most of the lakes and wetlands in the area /­Bosson et al. 2010/.
Another effect is that surface water fluxes in lakes where discharge occurs will be reduced, mainly
due to lower precipitation. The terrestrial vegetation community will change with climate. Primary
production will decrease in a harsher climate, resulting in a reduced rate of in-growth of wetlands
into lakes /­Brydsten and Strömgren 2010/ and a reduced productivity of natural foods and agricultural
crops in the area /­Löfgren 2010/.
During permafrost periods, parameters that describe hydrological fluxes (runoff, Lake_aqu_adv_mid_
up_norm, Lake_fract_Mire, Lake_adv_low_mid, Ter_adv_mid_up_norm and Flooding_coef) andproperties of wetland vegetation (Ter_biom_pp, Ter_prodBiom_pp, Ter_z_roughness, Ter_z_mixlay,
Ter_decomp and frac_C_atmos) and crops (prod_edib_cereal, prod_edib_tuber, prod_fodder, prod_
vegetab and leaf_areaIndex) were given values representative of permafrost conditions /­Bosson et al.
2010, Löfgren 2010, Andersson 2010/ and the wetland ingrowth rate was reduced by 75% /­Brydsten
and Strömgren 2010/.
Under permafrost conditions, modelled parameters describing hydrological fluxes are generally lower
than in temperate conditions, although the runoff is larger /­Bosson et al. 2010/. The terrestrial ecosystemparameters are also, in general, lower during permafrost conditions. Values for these parameters were
derived from other parts of Sweden, or from other sites, e.g. Greenland /­Löfgren 2010/. For mostaquatic ecosystem parameters, on the other hand, the same parameter values were used for temperate
and periglacial conditions. The exceptions were production of fish and crayfish in lakes (prod_edib_
fish_Lake and prod_edib_cray_Lake), which were assumed to be lower in a colder climate.
The permafrost depth and area of open water were used to determine whether the conditions werefavourable to permafrost development under lakes /­Brydsten and Strömgren 2010/. During conditions
with permafrost under lakes, it is assumed that there is no further release of radionuclides to the object.
It was also assumed that drilled wells would provide no water during periglacial climate domains.
The transition between temperate conditions and full permafrost conditions in the whole Forsmark
area has been estimated to prevail for a time period varying between 2,000 and 5,000 years (­Climate
report). Transition periods, in which parameters affected by permafrost were assumed to change
continuously between temperate and permafrost values, were assumed to be 2,000 years for themodelled biosphere object.

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10

The landscape dose conversion factors (LDF)

In SR-Site, doses to humans resulting from releases to the biosphere in different scenarios have been
calculated by multiplying release rates or pulse releases of radionuclides to the biosphere with a corresponding maximum landscape dose conversion factor (LDF). The maximum LDFs were generated
by running the radionuclide model for each separate biosphere object as described in Chapter 8 andusing the parameterisation presented in Chapter 9. For each radionuclide, the maximum LDFs were
derived by first finding the maximum annual dose over time per unit release rate or unit release to arepresentative individual of the most exposed group in each biosphere object, and thereafter finding
the maximum dose conversion factor across all biosphere objects.
This chapter summarises the results from the radionuclide model. First, the calculated LDFs are presented and compared with results from other assessments. Thereafter, brief descriptions of the resulting
patterns of LDFs in space and time are provided, including a discussion of the mechanisms behind the
behaviour. Finally, some calculations for additional, near future scenarios and for illustration of barrier
functions are presented. The chapter ends with a comparison between measured, present-day activity
concentrations and calculated concentrations resulting from a potential release from the repository. A
more complete description of the model and results, including examples from the different steps in thecalculation of LDFs and of the modified LDFs for a pulse release, are provided by /­Avila et al. 2010/.

10.1

Resulting LDFs

Maximum LDFs for a constant unit release rate (1 Bq/year) of different radionuclides were calculated
for the three different climate domains within a reference glacial cycle; temperate (represented by
the interglacial period), periglacial, and glacial domains, and for the global warming climate case (seeSection 8.7.2 for details on calculations). Results for the 19 radionuclides that were expected to contributed the most to human exposure are presented in Figure 10‑1. LDFs for all 40 assessed radionuclides
are presented in /­Avila et al. 2010/ and in the Data report.
10-8
10-9

LDF (Sv/y per Bq/y)

10-10
10-11
10-12

Global warming

10-13

Periglacial

10-14

Submerged/Glacial

10-15

Interglacial, no agri
Interglacial, agri

10-16
10-17

Zr-93

U-238

Th-230Th-229

Tc-99

Se-79

Pu-242

Ra-226

Pu-240

Pu-239

Ni-59

Np-237

I-129

Nb-94

Cl-36

Cs-135

C-14

Am-241

Ac-227

10-18

Figure 10‑1. Calculated maximum LDFs (the highest LDF over time among all biosphere objects) for
different climate domains/condition. LDFs for the initial submerged period were used to represent glacialconditions in the assessment. The effect on the LDFs of using agricultural products as food is evaluated bycontrasting LDFs for the intergalacial period before after agriculture is possible. Figure from /­Avila et al.
2010/.

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During the reference glacial cycle, the maximum LDF is consistently higher under the interglacial
period than under the other climate domains (Figure 10‑1). For instance, LDFs for glacial conditions
were below the values for interglacial conditions by two orders of magnitude. The maximum LDFs
during periglacial conditions were also lower than during temperate conditions, and these results wereconfirmed by detailed simulations of periglacial conditions (Section 12.2.1). Hence, the maximum
LDFs for the interglacial period are also maximum values during the whole reference glacial cycle,
and have therefore been used for cautious dose assessments for long-term release of radionuclieds
from the repository.
For most radionuclides, the LDF for temperate conditions differs marginally between the periods withand without agriculture (Figure 10‑1). However, for a few radionuclides (i.e. C‑14, I‑129, Nb‑54,
Ni‑59, U‑238), the LDFs differ by more than an order of magnitude between these two situations, and
it is only for C‑14 that the LDF is higher in the period when agriculture is not possible. The reason forthese differences are discussed in /­Avila et al. 2010/. Since the maximum value over the whole period
is used as maximum LDF, the differences have no effect on the final risk estimates. However the
results imply that the most exposed group corresponding to different radionuclides can be in viewed
as homogenous with respect to land use.
In the biosphere assessment, the global warming climate case is represented by a 50,000 year extensionof temperate conditions. Consequently, radionuclides that do not reach steady state activity concentrations within the initial temperate period (–9000 to 9400 AD) will continue to accumulate during theextended temperate period. However, most radionuclides have approached steady state at 9400 AD,
and additional accumulation and associated increase in maximum LDF is marginal for radionuclides
expected to contribute to dose. Only for two radionuclides, Cs‑135 and U‑238, LDFs were larger(approximately an order of magnitude) in the global warming climate case than under the reference
glacial cycle, which can be explained by several factors as discussed in /­Avila et al. 2010/. However,
due to the small contribution of Cs‑135 and U‑238 to the total risk estimate resulting from a long-term
release (see Section 13.5.4 in SR-Site main report), a tenfold increase in the LDFs of these nuclides
would not affect the final risk estimates significantly.
Table 10‑1. Characteristics of radionuclides contributing most to dose in the central corrosion
case /­Section 13.5.4 in SR-Site main report/. Pathway shows the dominant exposure pathway(s).
The contribution to dose from drinking water (Ingestion water) is in % of the LDF. Doses frominhalation and external irradiation are insignificant for all radionuclides presented in the table.
The columns Time (AD), N and Biosphere object show the time, number of affected individuals
and biosphere object, respectively, for the maximum LDF value. The Biosphere objects areshown in Figure 7-11.
Radionuclide

Maximum LDF Pathway(Sv Bq–1)

Ingestionwater (%)

Time (AD)N

Biosphere object

Ra-226

3.8 · 10–12

Vegetables

54

9400

79

121_3

Se-79

1.2 · 10–9

Vegetables,
cereals

0

4750

79

121_3

I-129

6.5 · 10–10

Vegetables,
milk

0.1

4050

79

121_3

Np-237

4.8 · 10–11

Crayfish, fish

1.0

3200

0.9

118

Cs-135

1.8 · 10–16

Vegetables,
milk

18

9400

80

124

Cl-36

3.8 · 10–15

Vegetables,
milk, cereals,
roots

1.2

3900

79

121_3

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10.1.1 Comparison with results from earlier studies
The method used for calculating landscape dose conversion factors in SR‑Site has been updated in several
important ways since the last two biosphere assessments of a deep repository: SR‑Can (SR-Can main
report) and SR-97 /­SKB 1999/. Data from the site have been used to modify parameter values, increasing their relevance and representativeness of the site. The changes in methodology and parameter values,
and their consequences for exposure, are discussed in detail in /­Avila et al. 2010/.
The maximum values of the ecosystem specific dose conversion factors (EDF) used in SR-97 /­SKB
1999/ were systematically higher than the LDFs calculated in the present assessment, with exception
for a few radionuclides (e.g. C‑14) (Figure 10‑2). These differences are attributable to important methodological differences between the two assessments, including the delineation of the sub-catchment,
assumptions on where a release will reach discharge areas and enter the ecosystems, as well as differences in the represention of the well /­Avila et al. 2010/. Moreover, in the SR-97 assessment genericparameter values were used in most cases, whereas data from the site investigation programs have beenused to a large extent in the SR‑Site assessment.
The methodology applied in SR-Site is based on that developed in SR-Can, but has been updated inseveral important ways. In the SR-Can assessment it was assumed that the releases were distributed
over the whole landscape, whereas in SR-Site it is assumed that all releases will reach the discharge
area where it will cause maximum exposure (i.e. to the most exposed group). In SR-Site, the representation of ecosystems and of the transition between them has been improved, and radionuclidetransport in till (lower layer of the regolith) has been explicitly included in the biosphere model.
For radionuclides where the consumption of contaminated food is the dominant pathway for exposure,the LDFs are typically an order of magnitude higher in the SR-Site than in the SR-Can assessment.
However, the activity concentration in well water was calculated in a similar way in the two assessments (though the exposure from the well was not combined with other pathways in SR-Can), andconsequently LDFs for radionuclides where drinking water is the dominant pathway is similar in the
two assessments /­Avila et al. 2010/.
10-08

EDF SR-97 (Sv/y per Bq/y)

10-09
10-10
10-11
10-12

EDF -Well

10-13

EDF -Mire

10-14

EDF -AgriLand

10-15

EDF -Lake

10-16

EDF -running waters

10-17
10-18
10-19
10-16

10-15

10-14

10-13

10-12

10-11

10-10

10-9

10-8

LDF SR-Site (Sv/y per Bq/y)Figure 10‑2. Comparison of the SR-Site LDFs with corresponding dose conversion factors (EDF) reported
in SR-97 /­SKB 1999/. The solid line represents a 1:1 relationship between SR-Site and the SR-97 dose factors,
and each point represents a specific in radionuclide. Figure from /­Avila et al. 2010/.

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10.2

Variation of LDFs in time and between biosphere objects

The effects of the shoreline regression and the subsequent succession of biosphere objects on LDFs
are similar for many of the radionuclides expected to contribute to dose (Figure 10‑3). LDFs increase
continuously with time during the sea stage (1 in Figure 10‑3), reflecting a gradually increasing activity
concentration in sea water. The flux of radionuclides to the water column increases when deep accumulation bottoms are first exposed to wave erosion (1a), but this is a transient phenomenon. The increasein concentrations during the sea stage is primarily driven by a decrease in water exchange as the sea
basins gradually become sheltered, and this development becomes most pronounced towards the endof the stage when land starts to emerge out of the sea (1b).
The LDFs increase further in the transition stage (2). In Figure 10‑3, the selected biosphere object develops directly into a wetland, and the increase in the LDF during the transition stage is a function of thegradual accumulation of radionuclides in peat. In the terrestrial stage (3) the wetland is fully developed.
A steep increase in LDFs early in this stage occurs when it is first possible to transform the wetland into
arable land (3a). This is because the agricultural soil is enriched in radionuclides in comparison withwetland peat, as a consequence of draining and mixing with deeper regolith layers by ploughing. From
this point, further accumulation of radionuclides in agricultural soil only marginally affects the LDFs.
For some radionuclides long-term accumulation results in a slight increase of LDFs (e.g. Cs-135),
whereas for others (Se-79, I-129) wetland concentrations are slightly lower under stable conditions.
1E-07

3

3a
1E-09

2

1E-11

1b

Sv/y per Bq/y

1E-13

1

1a

Se-79

1E-15

I-129
1E-17

Np-237

1E-19

Ra-226

1E-21

Cl-36
Cs-135

1E-23
1E-25
1E-27
-9000

-7000

-5000

-3000

-1000

1000

3000

5000

7000

9000

Time AD (y)Figure 10‑3. The development of LDFs for a number of dose-contributing radionuclides during an interglacial for Biosphere object 121_3. The nuclides Se-79, I-129, Ra-226 and Cl-36 all had their maximum
LDFs from this biosphere object. The objects goes through three development stages: 1) the sea stage(blue), 2) the transitional stage (white) and 3) the terrestrial stage (brown). Index letters refer to events thatcause relatively fast changes in the LDFs and are explained in the text. Note that object 121_03 does not
go through a lake stage, but the sea bay develops directly into a wetland. Figure from /­Avila et al. 2010/.

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The dose factors clearly vary between biosphere objects, but the degree of variation depends on theproperties of radionuclides (Figure 10‑4). Landscape object 105, which is in the sea stage during thefull temperate period, has maximum LDFs that for all radionuclides are consistently lower by threeorders of magnitude or more, compared with all other objects. For radionuclides where exposure fromfood is the dominant exposure pathway (i.e. C-14, Cl-35, I-129, Nb-94, Np-237, Se-79, Sn-126 andTc-99), LDFs typically vary by two to three orders of magnitude (excluding object 105). However,for radionuclides where drinking water is an important pathway for exposure (e.g. Am-241, Pa-231,
Pu-231, Pu-239, Pu-242, Ra-226 and Th-229), the variation in LDFs between objects is typicallywithin a factor of three. Furthermore, the order of objects with respect to LDF values is similar for
most radionuclides. For example, the biosphere object 121_3 yields the highest LDF for most of theexamined radionuclides /Availa et al. 2010/.

10.3

Calculations for pulse release, near future scenarios andillustrations of barrier functions

The methodology for calculating maximum LDFs for long-term releases has gradually developed
from the earlier assessments SR-97 /­SKB 1999/ and SR-Can (SR-Can main report). During the
SR-Site work results have been thoroughly explored and validated, and models and parametervalues iteratively updated. For short pulse releases and for releases in the near future, the results
have not been iterated and validated in the same thorough way. There is confidence that the numericalmodel can be applied also to these situations and that derived results do not underestimate the risk.
However, the temporal and spatial resolution of the model may not be sufficent to capture the detailed
dynamics of transient events. Moreover, some parameter values may have to be adjusted to be
representative for short-term equilibriums, and there are also a number of radionuclides appearing
in these situations which have received less attention at the site investigation and in the literature.
10−8
10−9
10−10
10−11

Sv/y per Bq/y

10−12
10−13
10−14
10−15
10−16
10−17

Zr−93

U−238

Th−230Th−229Tc −99Se−79

Ra−226Pu−242Pu−240Pu−239Ni−59

Np−237

Nb−94

I−129

Cs−135

Cl−36

C−14

Am−241

10−19

Ac−227

10−18

Figure 10‑4. Mean (red circles), minimum and maximum LDF for a selection of radionuclides acrossbiosphere objects (excluding object 105). The LDF values for object 105, which is submerged during
the whole interglacial, are shown separately (green squares). Figure from /­Avila et al. 2010/.

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10.3.1 Modified LDF for pulse release
The maximum LDF for each potentially released radionuclide is defined as the average annual
dose during the lifetime of a representative individual of the most exposed group, resulting from a
constant release rate of 1 Bq/y of this radionuclide. By contrast, the modified LDF for pulse releases
is defined as the average annual dose during the lifetime of a representative individual of the most
exposed group, resulting from a unit pulse release. The modified LDFs are used to evaluate doses
from pulse releases of the fraction of the inventory in a canister that is assumed to be instantaneously
available for release upon water contact.
Values for the modified LDF for pulse release (derived for radionuclides likely to be present in apulse releases), are presented in Table 10‑2. These values correspond to the maximum value of theannual doses obtained from simulation with pulse releases of 1 year duration, occurring at different
time points within an interglacial period.
Table 10‑2. Modified Landscape Dose conversion factors derived for pulse releases. LDFs wereobtained from simulations where a total of 1 Bq was released to a biosphere object during one year.
Radionuclide

LDF pulse
Sv/y per Bq

I-129

5.6 · 10–14

Se-79

9.7 · 10–14

Cl-36

4.3 · 10–15

Tc-99

2.8 · 10–15

Sn-126

2.3 · 10–15

Ag-108m

5.1 · 10–16

Cs-135

1.8 · 10–16

Nb-94

3.2 · 10–16

Ni-59

9.7 · 10–18

10.3.2 Early canister failure due to shear load
Canister failure due to rock shear has a low probability in the reference evolution, and the only identified
cause for such failure is a large earthquake close to the repository (Section 13.6 in SR-Site main report).
For times up to 1,000 years after closure, the probability that one out of the 6,000 canister has failed
at the end of the period is 2.4·10−5 (Section 13.6 in SR-Site main report). For such short periods, theLDFs do not give a reasonable representation of consequences of a radionuclide release to the biosphere. That is, the LDFs represent an upper bound of consequences from an approximately constantrelease during a full interglacial, or from a short pulse released at any time during an interglacial. The
release that would result from an earthquake in the near future would on the other hand occur when alarge part of the present interglacial period has elapsed (and hence not contribute to accumulation in
the biosphere) and the release rate would vary continuously over time.
Thus, to calculate the consequences from a failure due to an earthquake that occurs for times up to
1,000 years after the repository is sealed, the near-field release was used as a time dependent input
parameter to the radionuclide model. For these simulations it was assumed that each landscapeobject received the full release, and dose curves were generated for each biosphere object. By selecting, for each radionuclide individually, the maximum dose over all biosphere objects for each point
in time, a dose curve representing the landscape was generated for each nuclide (Figure 10‑5). These
results are presented and discussed in Section 13.6 in the SR-Site main report, as a part of the shear
load scenario.

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Mean annual effective dose (µSv)

102

C14
(0.0027)
Nb94(0.00041)
Cs137(0.00028)
I129(0.00024)
Ag108m (0.00018)
Ni59(0.00018)
Sr90(0.00016)
Total(0.0027)

10

1Dose corresponding to risk limit

10-1

10-2

10-3

10-4

102

103

104

Time (years)

Figure 10‑5. Mean annual effective dose from probabilistically calculated consequences of shear failure
occurring randomly during the initial 10,000 years. The peaks correspond to the time of the transition
period between the sea and lake stage for different biosphere objects in the Forsmark landscape. Figure
from Section 13.6 in SR-Site main report.

10.3.3 Residual scenarios to illustrate barrier functions
The radionuclide model has also been applied to illustrate the barrier function of the repository fora number of hypothetical release scenarios, where losses of barrier function are assumed already at
deposition (see Section 13.7 in SR-Site main report for details). These hypothetical residual scenarios include one failure mode where an initial defect in the canister copper shell of each canister
grows into a larger defect, and also calculation cases where there is a large opening in the copper
shell of all canisters.
In the above scenarios all canisters contribute to the release of radionuclides to the biosphere andthe assumption that the entire release will reach one biosphere object (as in the LDF calculations) isclearly not valid. For these scenarios it was instead assumed that the release of radionuclides would
be distributed over all identified discharge areas in the landscape, and that each biosphere object
would get a release proportional to the fraction of release points in the object, at each point in time.
To assess consequences in the period directly after closing the repository, the release was used as atime dependent input parameter to the radionuclide model (see above). Dose curves were generated
for each biosphere object. By selecting the maximum dose over all biosphere objects for each point
in time a dose curve representing the landscape was generated for each nuclide.
To assess periods far into the future, when the release is expected to vary little within time spansof 10,000 years, a constant unit release was distributed over the Forsmark landscape. LDFs werethen calculated in accordance with the methods described in Chapter 8. That is, the LDF for eachradionuclide was defined as the maximum dose over all biosphere objects and time points during
a full interglacial.

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10.4

Natural concentrations of radionuclides insurface ecosystems

A comparison between the background levels of radionuclides which occur naturally in the environment, and the activity concentrations resulting from a potential release from the repository, may givean indication of the extent to which the exposure of humans and organisms living in the Forsmark
area would be affected by a potential release. Below follows an attempt to compare measured activity concentrations of naturally occurring radionuclides in Forsmark, in the previously considered
Laxemar site, and in a number of reference sites /­Aastrup 1981, Porcelli et al. 2001, UNSCEAR 2010/,
with the calculated concentrations resulting from a release according to the central corrosion case.
The naturally occurring radioactive isotopes that contribute the most to the alpha activity in natural
waters are U‑238, U‑234, Ra‑226 and its daughter products and Po‑210 /­Östergren et al. 2003/.
Data from the site investigations also confirm that uranium isotopes (U‑234, U‑235, U‑238), anddaughter products from the decay of uranium (Ra‑226, Th‑230), contribute to a significant part of
the total background activity concentrations in surface water, sediments and soil in the Forsmark
area today /­Tröjbom and Grolander 2010/. Deep groundwater, which is enriched in uranium andradium isotopes (as compared to surface water), is a potential source of the activity concentration
presently found in the environment in Forsmark, and natural fluxes of U‑238, U‑234 and Ra‑226
to the investigation area has been estimated to be 4.7·105 Bq/yr, 1.2·106 Bq/yr and 7.6·106 Bq/yr,
respectively (Radionuclide transport report). Thus, isotopes of uranium, thorium and radium wereused to compare background levels of radionuclides with those expected to result from a potential
release from the repository.
The activity concentrations resulting from a constant release of radionuclides to natural ecosystems
in potential discharge areas in Forsmark were calculated with the radionuclide model, assuming the
maximum release for each radionuclide given the central corrosion case /­Avila et al. 2010/. The maximum activity concentrations in surface water, near surface groundwater and upper regolith acrossall biosphere objects were extracted, considering a full interglacial period. In addition, calculated
peak values for Biosphere object 136 (Lake Bolundsfjärden) were used to contrast calculated activity
concentrations resulting from a release into a discharge area which is well represented in site data.
The natural activity concentrations in surface water observed in Forsmark and Laxemar, and in reference sites available in the literature /­Porcelli et al. 2001/, were all several orders of magnitude higher
than the expected contribution from a potential release from the repository to sea and lake water(Table 10-3). Similarly, the background activity concentrations near surface groundwater at the two
investigated sites and in samples collected across Sweden /­Aastrup 1981/ were orders of magnitude
higher than the expected contribution from a repository release.
A comparison between measured activity concentrations in upper regolith and calculated concentrations resulting from a release yielded similar results. That is, the natural activity concentrations
observed at Forsmark and Laxemar were several orders of magnitude higher than those expected toresult from a potential release from a repository at Forsmark (Table 10‑4). This was also true for thecomparison of calculated activity concentrations in peat with that reported for top soils in Northern
Europe /­UNSCEAR 2010/. Thus, it can be concluded that the natural background radiation fromuranium, thorium and radium in potential discharge areas in Forsmark would not be significantly
affected by a release of these radionuclides from the repository.

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Table 10‑3. Calculated activity concentrations in lake and sea water and in near surface
ground­water, resulting from a release of radionuclides given the central corrosion case. Activity
consentrations are compared with measured concentrations (median values) from Forsmark and
Laxemar and from reference sites available in the literature /­Porcelli et al. 2001, Aastrup 1981/.
Calculated concentrations from a release

Measured background concentrations

Radionuclide(Bq/l)

Biosphere
object 136

Max across all
biosphere objects

Forsmark1)

Laxemar2)

Lake water
Ra-226
Th-230Th-232
U-234
U-235
U-238

4.5 · 10–7
1.6 · 10–12
1.3 · 10–16
1.0 · 10–10
9.9 · 10–12
1.1 · 10–10

2.7 · 10–7
1.1 · 10–11
1.1 · 10–16
4.0 · 10–10
2.7 · 10–11
2.9 · 10–10

6.0 · 10–3
4.2 · 10–4
2.0 · 10–4
1.7 · 10–2
6.2 · 10–4
1.5 · 10–2

2.2 · 10–3
1.4 · 10–3
7.3 · 10–3
3.2 · 10–4
6.3 · 10–3

Sea water
Ra-226
Th-230Th-232
U-234
U-235
U-238

3.1 · 10–9
5.0 · 10–17
2.8 · 10–21
9.6 · 10–14
8.7 · 10–15
9.8 · 10–14

7.2 · 10–9
4.2 · 10–15
2.3 · 10–20
3.0 · 10–12
1.9 · 10–13
2.1 · 10–12

3.1 · 10–3
3.5 · 10–4
1.6 · 10–4
1.8 · 10–2
2.9 · 10–4
1.5 · 10–2

8.2 · 10–4
5.4 · 10–4
8.3 · 10–3
3.0 · 10–4
6.4 · 10–3

Near surface groundwater
Ra-226
4.2 · 10–5
Th-2301.8 · 10–10
Th-232
1.3 · 10–14
U-234
6.8 · 10–9
U-235
6.7 · 10–10
U-238
7.5 · 10–9

4.4 · 10–4
1.8 · 10–9
1.3 · 10–13
7.1 · 10–8
6.9 · 10–9
7.7 · 10–8

7.2 · 10–2
1.7 · 10–3
9.0 · 10–4
8.8 · 10–2
2.5 · 10–3
7.4 · 10–2

5.9 · 10–2
4.2 · 10–3
2.7 · 10–3
3.2 · 10–2
4.7 · 10–4
2.1 · 10–2

1)

Literature

4.6 · 10–4 3)
8.2 · 10–5 3)

1.8 · 10–3 3)
1.1 · 10–3 3)
3.1 · 10–6 3)

4.2 · 10–3 4)/­Tröjbom and Grolander 2010/, 2) /­Roos et al. 2007/, 3) /­Porcelli et al. 2001/, 4) /­Aastrup 1981/

Table 10‑4. Calculated activity concentrations in sediments and soil, resulting from a releaseof radionuclides given the central corrosion case. Activity consentrations are compared withmeasured concentrations (median values) from Forsmark and Laxemar and from reference sites
available in the literature /­UNSCEAR 2010/.
Calculated concentrations from a release

Measured background concentrations

Radionuclide(Bq/l)

Biosphere
object 136

Max across all
biosphere objects

Forsmark1)

Laxemar2)

Limnic sedimentRa-226
Th-230Th-232
U-234
U-235
U-238

2.9 · 10–3
9.4 · 10–8
7.3 · 10–12
7.4 · 10–7
7.2 · 10–8
8.1 · 10–7

3.8 · 10–2
2.9 · 10–6
3.1 · 10–11
2.3 · 10–5
1.5 · 10–6
1.6 · 10–5

3.6 · 102.9 · 102.0 · 10
1.3 · 102
5.3
1.1 · 102

7.0 · 10
2.8 · 10
2.4 · 10
1.6 · 102
6.2
1.3 · 102

Marine sedimentRa-226
Th-230Th-232
U-234
U-235
U-238

3.5 · 10–4
2.1 · 10–9
1.2 · 10–13
2.2 · 10–8
2.0 · 10–9
2.2 · 10–8

6.4 · 10–4
6.8 · 10–8
3.8 · 10–13
3.4 · 10–7
2.2 · 10–8
2.4 · 10–7

8.5
5.6
5.8
8.5
3.8 · 10–1
8.0

8.5
2.7 · 10
2.6 · 109.9 · 104.0
8.1 · 10Top soil
Ra-226
Th-230Th-232
U-234
U-235
U-238

2.2 · 10–3
1.8 · 10–7
1.4 · 10–11
1.3 · 10–6
1.3 · 10–7
1.5 · 10–6

2.8 · 10–3
2.4 · 10–6
1.8 · 10–11
8.6 · 10–6
5.7 · 10–7
6.1 · 10–6

3.9 · 10
1.7 · 10–5
9.6
5.1 · 10
1.8
4.6 · 10

1.6 · 105.6
4.5
4.8 · 101.8
3.4 · 101)

Literature

2 –1000 3)
0.5 –115 3)

10 –1000 3)/­Tröjbom and Grolander 2010/, 2) /­Roos et al. 2007/, 3) /­UNSCEAR 2010/

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11

Assessment of impact on non-human biota

The aim of this chapter is to summarise the assessment of the impact on non-human biota of potential radioactive releases from the high-level waste repository planned at Forsmark, in order to ensure
adequate protection of the environment /­Torudd 2010/. Doses to reference organisms corresponding
to species of interest at the site were calculated with the ERICA software tool, assuming release
under the central corrosion case (see Secation 3.5.4 in SR-Site main report). Results were assessedin the light of regulations and requirements of the Swedish Radiation Safety Authority concerning
protection of the environment /­SSM 2008a/.

11.1

Background

Attitudes concerning the protection of animals and plants from deleterious effects of ionising radiations have changed considerably over the last 35 years. Up until around 1975, the issue was entirely
ignored. As a next stage, the 1977 Recommendations of ICRP /­ICRP 1977/ made the assumption that
if man is adequately protected, then other living things are also likely to be sufficiently protected,
and essentially the same attitude was taken in the 1990 ICRP Recommendations /­ICRP 1991/. The
2007 ICRP Recommendations /­ICRP 2007/, however, include a systematic approach for radiologicalassessment of non-human species. This was not driven by any particular concern over environmental
radiation hazards. It was meant to fill a conceptual gap in radiological protection, and to develop a
protection policy in line with society’s general goals for environmental protection.
However, the objectives of such a protection policy for non-human biota are not yet as clear as thoseof human radiological protection, which aims to prevent deterministic tissue reactions and reduce
stochastic effects as much as reasonably achievable. /­ICRP 2007/ suggests that the aim should bea negligible effect on the maintenance of biological diversity, the conservation of species, and thehealth and status of natural habitats, communities, and ecosystems. In line with this, /­ICRP 2008/
notes that the biological endpoints of most relevance in individuals after radiation exposure will bethose that could lead to changes in population size or structure.
/ICRP 2008/ goes on to say that some form of practical means is required to translate knowledge ofthe effects of radiation on different types of animals and plants into advice on management decisions
and judgements that may be needed. To this end, ICRP proposes the use of a limited set of Reference
Animals and Plants to serve as a basis for the understanding and interpretation of the relationships
between exposure and dose, and between dose and certain categories of effect, for a few, clearly
defined types of animals and plants.
Furthermore, /­ICRP 2008/ notes that “dose limits” of the form used in human radiological protection
would be inappropriate, but that some form of numerical guidance is required, and sets out proposed
bands of “derived consideration reference levels”. Within these bands, there is likely to be some chanceof deleterious effects of ionising radiation to the pertinent Reference Animal or Plant that could be used to
optimise protection efforts (and by inference, below these bands the risks would appear to be negligible).
In parallel and aligned with these developments, a series of major research projects (EPIC, FASSET,ERICA, PROTECT) concerning these issues has been funded under the European Commission Euratom
Framework programmes. SKB participated in the FASSET and ERICA project. An overview of the entire
series and detailed descriptions of each project, including links to the resulting scientific publications,are available at the erica-project.org web site. The project programme generated the ERICA Integrated
Assessment approach and the ERICA tool used in the present study and described in Chapter 12. The
screening dose rate used in the ERICA tool is, again, not a “dose limit”. It is an instrument to assist in theseparation of situations of negligible concern from those situations where it is appropriate to pause forreflection to consider whether any concern is warranted. Thus, the ERICA screening dose rate and the
ICRP derived consideration level serve much the same purposes.

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The current awareness of environmental protection issues has emerged over about a decade, andthe policy advice of ICRP and the practical tools provided by the Euratom research frameworkprogrammes were generated over that time-scale. However, the present study is one of the very firstcases where the policy and the tools are applied to a practical case where the results are intended toform part of the underpinning of a license application for the localisation of a repository for spent
nuclear fuel.

11.2

Methodology

The assessment of the environment has been carried out by evaluating the potential effects of aradionuclide release on individual organisms. The rationale for this approach is the assumptionthat if there are no detrimental effects at the level of individuals, then negative consequences at the
population, community or ecosystem levels can also be excluded.
For the assessment, radionuclide release from the geosphere was used as input to the radionuclide
model for the biosphere (Chapter 8). Radionuclide activity concentrations in environmental media indischarge areas in the Forsmark landscape were then simulated for an interglacial (Figure 11‑1).
The activity concentrations in water and sediments in freshwater and marine ecosystems, and in peat
and air in wetland ecosystems were used as input in the ERICA tool /­Brown et al. 2008/ to obtain
activity concentrations in selected organisms.
Calculation and evaluation of
total dose rates to biota

Radionuclide concentrations
in biota

Internal dose
rates to biota

External dose
rates to biota

Simulations with
the ERICA toolRadionuclide concentrations in environmental media:soil, sediments, water and air

Simulations with theradionuclide transportmodel

Geosphere
releases

Figure 11‑1. Assessment of the consequences of radionuclide releases for non-human biota. The assessent
starts by calculating radionuclide concentrations in environmental medias. These concentrations are thenused as input data to the ERICA tool, and the resulting dose rates are compared to a screening dose rate.
Each step in the calculation procedure are explained in Sections 11.2.1 to 11.2.8 below, and details areprovided in /­Torudd 2010/. Figure from /­Torudd 2010/.

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The ERICA tool calculates the internal dose rates to biota from modelled activity concentrations in
the different organisms, and estimates the external dose rates from the activity concentrations in environmental media. The numerical endpoint of the consequence assessment is the total absorbed dose
rate to the selected organism from each radionuclide considered in the assessment. Finally, the sum of
the dose rates was evaluated against a screening dose rate, corresponding to the lowest dose rate that
potentially may lead to detrimental effects on individual organisms, (i.e. a no-effects dose rate).

11.2.1 Radionuclides considered in the assessments
The list of radionuclides considered in the assessment is presented in Table 11-1. This list covers
all nuclides included in the SR-Site safety assessment, with the exceptions of Ac-227, Pa-231and
Pd-107. For these three nuclides neither site nor literature data were available with respect tobiological uptake (i.e. CR), precluding a meaningful analysis. Most of the 37 radionuclides (of 24
elements) included in the assessment are present by default in the ERICA tool, but some isotopes,
shown in italics in Table 11‑1, were added to the ERICA database.
11.2.2 Organisms considered in the assessments
In order to prevent or reduce the frequency of deleterious radiation effects in the environment toa level where they would have a negligible impact on the maintenance of biological diversity, theconservation of species, or the health and status of natural habitats, communities and ecosystems,
there is a need to relate exposure to dose, dose to effect, and effect to consequences /­ICRP 2008/. To
permit such analyses, the ERICA tool uses a small, well-defined set of data for the reference organisms. Each reference organism has its own specified geometry and selection of habitat in terrestrial,
freshwater or marine ecosystems. The approach is compatible with that used by ICRP, and someof the geometries proposed for the ICRP “Reference Animals and Plants” /­ICRP 2008/ are used as
defaults in the ERICA tool.
Species that are presently found in the Forsmark area were the primary target for the SR-Site assessment. To ensure that ecosystem functioning is protected, organisms playing a critical role (key-stone
species) or being very abundant (foundation species) and representing different functional groups,
were identified. In addition, species that have an economic importance to man (e.g. livestock, fishand game) or a conservation value (e.g. endemic and endangered species) were identified.
The assessment was limited to species occurring in marine and freshwater ecosystems and in
wetlands, since it was expected that these are the natural ecosystem types that may be most affectedby potential releases (Chapter 7). Agricultural ecosystems were not considered in the analysis.
This was because future contaminated agricultural land in Forsmark is likely to originate fromdrained wetland, and these agricultural soils are expected to be productive (and thus provide a stableenvironment) for 100 years or less (Section 8.3.3). Thus, the species associated with this land would
either be introduced by humans (crop or livestock), or invade from adjacent agricultural land andconsequently they would be part of large and more stable biological populations.
Table 11‑1. Elements and radionuclides considered in the assessments. Entries in italics wereadded to the default database of the ERICA tool /­Torudd 2010/.
Element

Radionuclide

Element

RadionuclideAg

Ag-108m

Pb

Pb-210Am

Am-241, Am-243

Po

Po-210

C

C-14

Pu

Pu-239, Pu-240, Pu-242

Ca

Ca-41

Ra

Ra-226

Cl

Cl-36

Se

Se-79

Cm

Cm-244, Cm-245, Cm-246

Sm

Sm-151Cs

Cs-135, Cs-137

Sn

Sn-126

Ho

Ho-166m

Sr

Sr-90

I

I-129

Tc

Tc-99

Nb

Nb-94

Th

Th-229, Th-230, Th-232

Ni

Ni-59, Ni-63

U

U-233, U-234, U-235, U-236, U-238

Np

Np-237

Zr

Zr-93

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For most of the identified species of interest, site and literature data were lacking. Instead, eachspecies was mapped to a reference organism of similar taxonomy within the appropriate ecosystem.
The mapping of functional and dominant species and economically important species can be foundin Table 11‑2 and Table 11‑3 respectively. Identified endangered or “red-listed” species (~100 species)
and their corresponding reference organisms are listed in /­Torudd 2010/.
According to /­Beresford et al. 2007/, the selection of reference organisms included in the ERICA
tool makes it possible to address all protected species within Europe. Nevertheless, to increase theconfidence in the analysis, a number of common species currently found in Forsmark were also
included.
For most of the species sampled at the site, concentration ratios for a number of radionuclides (CR,see below) and morphology were available from the site investigation or could be determined.
However, most species were represented by a few individuals only (typically three or less). Thus, it
was unlikely that the field data would capture the large inherent variability in the equilibrium concentration ratios at the species level /­Sheppard 2005/, and consequently the assessment was primarilyfounded on ERICA reference organisms.
Table 11‑2. Organisms with important ecosystem functions in the Forsmark area. English
and scientific names are listed together with the corresponding ERICA reference organisms.
Ecosystem indicated by capital letter (F = freshwater, M = marine, T = terrestrial). N.A. = norelated species sampled at the site.
English names

Swedish names

Scientific names

ERICA reference organism

Terrestrial

alder

klibbalAlnus glutinosa

Treebottle sedge

flaskstarr

Carex rostrata

Grasses and herbs

common frog

vanlig groda

Rana temporaria

Amphibia

Norwegian spruce

granPicea abies

Treepeat moss

vitmossa

Sphagnum spp.

Lichen and bryophytes

pine tree

tall

Pinus silvestrisTree

red foxrödräv

Vulpes vulpes

Mammalreed

vassPhragmites australis

Grasses and herbs

water volevattensork

Arvicola terrestris

Mammalchara

kransalgChara spp.

microphytobenthos

zooplankon

Fresh water

Vascular plant
Zooplankton

midge

fjädermygga

Tanypodinae

Insect larvae

pike

gädda

Esox lucius

Pelagic fishperchaborrePerca fluviatilis

Pelagic fish

reed

vass

Phragmites australis

Vascular plant

roach

mört

Rutilus rutilus

Pelagic fish

ruffe

gärs

Gymnocephalus cernua

Pelagic fishtenchsutareTinca tinca

Pelagic fish

MarineBaltic macomaÖstersjömussla

Macoma balthica

Benthic mollusc

bladder wrack

blåstång

Fucus vesiculosus

Macroalgae

duck mussel

allmän dammussla

Anodonta anatina

Bivalve mollusc

herring

strömming

Clupea harengus

Pelagic fish

idotheagråsugga

Idothea spp.

phytoplankton

phytoplankton

Crustacean
Phytoplankton

perchaborrePerca fluviatilis

Pelagic fishtenchsutareTinca tinca

Pelagic fish

zooplankton

zooplankton

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Table 11‑3. Economically important organisms in the Forsmark area. English and scientificnames are listed together with the corresponding ERICA reference organisms. Ecosystem
indicated by capital letter (F = freshwater, M = marine, T=terrestrial).
English names

Swedish nameScientific names

ERICA reference organism

cloudberry (T)hjortron

Rubus chamaemorus

Grasses and herbs

cranberry (T)tranbär

Vaccinium oxycoccus

Grasses and herbs

Norwegian spruce (T)granPicea abies

Tree

Peat moss (T)vitmossa

Sphagnum sp

Lichen and bryophytes

Pine tree (T)tall

Pinus silvestris

Tree

Sedges (T)starr

Carex sp

Grasses and herbs

sutareTinca tinca

Pelagic fishburbot (M)lake

Lota lota

Benthic fish

common eider (M)ejder

Somateria mollissima

Bird (duck)eel (M)ål

Anguilla anguilla

Pelagic fish

herring (M)strömming

Clupea harengus

Pelagic fish

Cyclopterus lumpus

Benthic fish

Terrestrial

Fresh watertench (F)Marinelumpsucker (M)perch (F, M)

aborrePerca fluviatilis

Pelagic fish

pike (F, M)

gädda

Esox lucius

Pelagic fishringed seal (M)vikarsäl

Pusa hispida

Mammal

11.2.3 No-effect dose rate
The basic quantity for estimating exposure to ionising radiation is the amount of absorbed energy
per unit mass, i.e. the absorbed dose. For assessment of radiological effects on biota, the whole-body
exposure is considered, and the exposure is related to effects on traits such as survival, growth
and reproduction. The sensitivity of the individual organism to exposure is likely to vary between
ecosystems and taxonomic groups. Moreover, radiological effects at the population level may beaffected by species differences in habitat size, life history strategies and population dynamics.
However, data and knowledge are currently not sufficient to derive consistent and robust screening
values for separate organism groups, and best practice for judging the level of environmental risk is
to contrast estimated dose rates against a generic no-effect dose level /­Howard et al. 2010/. In thisassessment the no-effect incremental dose rate of 10 μGy h–1 was used.
This value is the default screening criterion in the ERICA tool and has been derived from a distribution analysis of species sensitivity on reproductive traits in vertebrates, invertebrates and plants,
performed on the basis of chronic exposure data /­Andersson et al. 2009/. Howard and co-workers/­Howard et al. 2010/ reviewed the numerical criteria for protection of non-human biota, andrecommended use of the 10 μGy h–1 criteria. Furthermore, this screening value is below the bandsof “derived consideration levels” proposed by /­ICRP 2008/.

11.2.4 Dose assessments using the ERICA tool
The ERICA tool is a software package that supports the ERICA Integrated Approach to assessing thesafety of the environment. The approach provides guidelines on problem formulation, impact assessment and data evaluation. The ERICA tool guides the user through the assessment process, keeps
records and performs the calculations to estimate whole body dose rates to selected organisms. The
tool considers the majority of the radionuclides included in ICRP Publication 38 /­ICRP 1983/, andinteracts with the FREDERICA database on radiation effects, which is a compilation of the scientific
literature on radiation effect experiments and field studies.

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The assessment element is organised in three separate tiers with increasing complexity. When theeffects are not shown to be negligible in a lower tier, the assessment should continue to the nexttier. To permit the use of site-specific organism data (CR and geometries) and the addition of someradionuclides, Tier 2 was used as the entry point in the SR-Site assessment.
Tier 2 assessment

In Tier 2, Risk Quotients (RQ) are calculated for each organism and each radionuclide according to
the relationship:
RQi = Di / Dlim
where Di = the estimated whole-body absorbed dose to organism i, and Dlim = the projected no-effect(“screening”) dose rate. RQi values were summed over all radionuclides to obtain total RQ values
for each organism.
The output from the Tier 2 assessments were 1) “expected” RQs obtained by deterministic calculations
using mean values for all parameters, and 2) “conservative” RQs (95th percentile, assuming an exponential distribution of dose rates) obtained by multiplying the “expected” RQ by an uncertainty factor.
If all “conservative” RQ’s are less than one, the situation is likely to be of negligible radiologicalconcern. If some “conservative” RQ’s exceed one, but all “expected” RQs are less than one, theresults and assessments needs to be reviewed. Finally, if any “expected” RQ exceeds one, thenfurther assessment using Tier 3 is warranted.
Probabilistic simulations

To examine the effect of parameter uncertainty on the estimate of total absorbed dose rates, probabilistic simulations were carried out with probability density functions (PDF) for the concentration ratios(CR) and mean values for all other model parameters. PDFs for reference organisms were based ondata from the ERICA tool. For each radionuclide and organism, the mean values, standard deviation,
median, and different percentiles of the dose rates were calculated from the probabilistic simulations.

11.2.5 Representation of organisms
There is an enormous diversity of organisms with respect to size, morphology and habitat choice.
To allow dosimetric calculations that cover a wide range of exposure situations, the ERICA tool has
made a number of simplifications with respect to the representation of organisms. Thus, the shapesof organisms are approximated by spheres or ellipsoids. In addition, the habitat selection of organisms
is assigned to one of ten habitat types, namely: in-soil, and on-soil (including in-air) in terrestrial
ecosystems, and in-sediment, on surface-sediment, in water-column, and on water-surface in fresh
water and marine ecosystems, respectively. For the SR-Site assessment it was further assumed thatorganism density was the same as that of water for all evaluated organisms.
11.2.6 Activity concentrations in biota
Plant root uptake from contaminated soil, ingestion of contaminated food and water, and inhalationof contaminated air will result in an internal activity concentration of radionuclides. In the ERICA
tool, whole-body activity concentrations in biota are predicted directly from the activity concentrations in the environmental media, using equilibrium concentration ratios (CRs). For terrestrial biota,
the CRs are defined as the radionuclide activity concentration in whole-body (Bq kg–1 fresh weight)
divided by the radionuclide activity concentration in soil (Bq kg–1 dry weight) or in air (Bq m–3)
for 3H, 14C, 32P and 35S. For aquatic biota, the CRs are defined as the activity concentration in biota
whole body (Bq kg-1 fresh weight) divided by the activity concentration in filtered water (Bq l–1).
Most CRs estimated in this study are based on measured values of stable element concentrations inbiota and environmental media, reported in /­Tröjbom and Nordén 2010/. The number of available
samples used to calculate CRs were typically limited to three or less on the species level.

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11.2.7 DosimetryRadionuclides in the environment lead to both internal and external exposure of organisms. In the
ERICA tool, the internal absorbed dose rate (µGy h–1) in biota is a function of whole-body activity
concentrations (see above), size of organism and the type and energy of emitted radiation. Absorbed
dose rate from external radiation depends in addition on the contamination level in and the propertiesof the environment. Below is a brief description of the methods used for calculating dose conversion
factors in the ERICA tool. A detailed description of the underlying approaches and the data that havebeen applied in the dosimetric module of the ERICA tool is presented in /­Ulanovsky et al. 2008/.
Calculation of Dose Conversion Coefficients

Dose Conversion Coefficients (DCCs) are defined as the internal absorbed dose rates (µGy h–1)
per unit activity concentration in an organism (Bq kg–1 fw) or as the external absorbed dose rates(µGy h–1) per unit concentration in environmental media (Bq kg–1 fw or Bq l–1) /­Pröhl 2003/. Doseconversion factors are specific with respect to organism (size and habitat) and radionuclide (typeand energy of emitted radiation, decay chain).
For internal exposure, the radioactivity is assumed to be homogenously distributed in the whole
body, and individual tissues or organs are not considered. Moreover, the fraction of the emitted
energy per transformation in the body that is absorbed (i.e. DCCint) does not depend on propertiesof the environment. In the derivations of DCCs, α-, β-, and γ-radiation are treated separately anddifferent radiation weighting factors are applied for the radiation types. In this study, the default
weighting factors 10, 3 and 1 were used for α-radiation, low‑β energy radiation, and γ-radiation
plus higher-energy β-radiation, respectively.
For external exposure, DCCs are calculated separately for the different environmental media water,
soil/sediments and air. The external dose conversion factor for an organism (DCCext) is calculated
by combining media-specific DCCs according to the fraction of time that an organism spends ineach habitat.
The external DCC values depend on radioactive decay properties (which is radionuclide-specific),
the geometrical relationship between the source of radiation and the target organism, the compositionand shielding properties of materials or media in the environment, and the habitat and size of theorganism. For external radiation, only β- and γ-radiations are considered. That is because external
exposure of macroscopic organisms by short-range radiation (α and low energy β) is limited due to
weak penetration.
For all radionuclides of interest for this study, DCC-values were calculated for reference organisms
and for species from the site using the interpolation procedure available within the ERICA tool. The
details for these calculations are provided in /­Torudd 2010/.

11.2.8 Activity concentrations in environmental media
The basic assumption of the SR-Site assessment is that some degree of failure of the barriers at
the repository will lead to a release of radionuclides. The activity concentrations in environmental
media that would result from such a release constitute the primary input to the ERICA tool. For each
assessed radionuclide (Table 11‑1), such input data were obtained by taking the maximum far-fieldrelease for the central corrosion case during the simulation period of 1 million years (SR-Site main
report), and apply it as a constant release rate to the biosphere of Forsmark. The radionuclide modelfor the biosphere (Chapter 8) was used to run the biosphere simulations through an interglacial(~20,000 years) for all biosphere objects in the Forsmark landscape.
The output from the model was radionuclide concentrations in upper regolith (peat and sediment),
air (for C-14), and water (freshwater and marine) as a function of time for each biosphere object.
For each radionuclide and environmental media, the maximum values over all biosphere objects
during the simulation period were used as input values for calculations of dose rates to biota with
the ERICA tool /­Torudd 2010/.

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11.3

Resulting doses to non-human biota

For all investigated organisms the calculated dose rates were at least four orders of magnitude
below the screening no-effect dose level of 10 μGy h–1 (Table 11‑4). When the uncertainty of thedose rates was taken into account (by using the 95th percentile of the probabilistic simulations or byusing the conservative RQ), the dose rates were still far below the no-effect dose rate. That is, forfreshwater phytoplankton that received the highest dose rate, the deterministic dose rate was 3·10–3,
corresponding to a RQ of 3·10–4. The 95th percentile of the dose rate was below 0.01 μGy h–1, andthe conservative risk quota was 10–3. It was noted that the mean values from the probabilistic calculations were almost identical to the deterministic estimates (data not shown), which was expected as
the arithmetic mean from the PDF of the CR parameters were used in the deterministic calculations.
Table 11‑4. Whole body dose rates for terrestrial, fresh water and marine biota in Forsmark given
the release from the central corrosion case. Estimates from deterministic calculations are given
together with the 95th percentile from probabilistic simulations. Expected and conservative risk
quotients are explained in Section 11.2.4.
Reference organsim

Dose rate (μGy h–1)

Risk Quotients

Deterministic
estimate

95th
percentile

Expected

Conservative

Amphibia

2.9 · 10–5

5.9 · 10–5

2.9 · 10–6

8.7 · 10–6

Bird

2.7 · 105.9 · 10

2.7 · 108.1 · 10–6

Detritivorous invertebrate

6.4 · 10

1.4 · 10

6.4 · 10

1.9 · 10–5

Flying insect

6.1 · 10

1.4 · 10

6.1 · 10

1.8 · 10–5

Gastropod

5.9 · 10

1.4 · 105.9 · 10

1.8 · 10–5

Grasses and herbs

3.7 · 108.5 · 10

3.7 · 10

1.1 · 10–5

Mammal, large

2.2 · 104.9 · 102.2 · 10

6.5 · 10–6

Mammal, small

2.5 · 105.2 · 10

2.5 · 10

7.6 · 10–6

Lichen and bryophytes

6.7 · 10

1.2 · 10

6.7 · 102.0 · 10–4

Reptile2.9 · 105.8 · 102.9 · 10

8.6 · 10–6

Shrub

7.6 · 102.0 · 10

7.6 · 10

2.3 · 10–5

Soil invertebrate

6.3 · 10

1.4 · 10–6

6.3 · 10

1.9 · 10–5

Tree

6.1 · 10–5

1.6 · 10–4

6.1 · 10–6

1.8 · 10–5

Bird

1.6 · 10–5

4.4 · 10–5

1.6 · 10–6

4.9 · 10–6

Bivalve mollusc

3.7 · 107.7 · 10

3.7 · 10

1.1 · 10–4

Crustacean

2.7 · 10

4.8 · 10

2.7 · 108.1 · 10–5

Gastropod

2.7 · 10

5.3 · 10

2.7 · 108.2 · 10–5

Insect larvae

1.9 · 105.1 · 10

1.9 · 10

5.6 · 10–4

Mammal

1.8 · 10

4.3 · 10

1.8 · 10

5.4 · 10–6

Pelagic fish

1.7 · 104.0 · 10

1.7 · 105.0 · 10–6

Phytoplankton

3.4 · 109.7 · 10

3.4 · 101.0 · 10–3

Vascular plant

5.2 · 10

1.2 · 105.2 · 10

1.6 · 10–4

Zooplankton

2.2 · 104.9 · 10–5

2.2 · 10

6.5 · 10–5

Benthic fish

1.1 · 10–6

1.8 · 10–6

1.1 · 10–7

3.4 · 10–7

Benthic mollusc

1.9 · 10

3.1 · 10

1.9 · 10

5.6 · 10–7

Bird

3.2 · 109.0 · 10

3.2 · 109.5 · 10–8

Crustacean

6.3 · 10

1.2 · 10

6.3 · 10

1.9 · 10–7

Macroalgae

1.4 · 10

1.8 · 10

1.4 · 10

4.3 · 10–7

Mammal

8.5 · 102.2 · 108.5 · 10

2.5 · 10–8

Pelagic fish

3.4 · 101.0 · 10

3.4 · 101.0 · 10–7

Phytoplankton

2.9 · 10

6.2 · 102.9 · 108.7 · 10–7

Polychaete worm

3.0 · 10

4.6 · 103.0 · 108.9 · 10–7

Vascular plant

1.3 · 10

1.9 · 10–7

1.3 · 104.0 · 10–7

Zooplankton

3.4 · 10–7

6.9 · 10–7

3.4 · 10–8

1.0 · 10–7

Terrestrial
–5
–5
–5
–5
–5
–5
–5
–4
–5
–5
–5

–5
–4
–4
–4
–5
–5
–5
–3
–5
–4
–4

–6
–6
–6
–6
–6
–6
–6
–5
–6
–6

Fresh water
–4
–4
–4
–3
–5
–5
–3
–4
–4

–4
–4
–4
–3
–5
–5
–3
–3
–4

–5
–5
–5
–4
–6
–6
–4
–5

Marine

130

–6
–7
–7
–6
–8
–7
–6
–6
–6

–6
–7
–6
–6
–7
–6
–6
–6
–6

–7
–8
–8
–7
–9
–8
–7
–7

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Dose rates were also calculated for organisms from the site (based on morphology and CR from sitedata as far as possible) and the detailed results from these analyses are presented in /Torudd 2010/. For
most individual species the sample size did not justify inference from these calculations to the safetyassessment. Moreover, no substantive difference in calculated dose rates could be detected for ERICA
reference organism when CRs from the site were used (as far as possible) as compared to calculations
based entirely on generic data. Thus, the use of site data did not appreciably affect the calculated
dose rate; primarily because site data was missing for major dose contributing radionuclides.
Comparisons of the concentration ratios (CR) from site data with CR for comparable ERICA reference
organisms showed that the site data was reasonably well represented by the ERICA database for wellinvestigated organisms (e.g. terrestrial vascular plants and marine pelagic fish) and elements. However,for organism groups that were less well represented in the database, CR for individual species from thesite frequently fell outside the 95% interval of the distribution of the corresponding ERICA reference
organism. This pattern was seen for all three ecosystems. Systematic differences could in most cases be
attributed to the limited sample size or lack of representative samples in the database, but in a few cases
there were indications that CR at the site showed site specific characteristics. For example, the CR for
Pb and Cs were systematically lower in vascular plants, rodents and larger herbivores, possibly indicating that the transfer characteristics at the site was not fully captured by the average conditions reflectedin the ERICA data. Similarly CR for U was systematically lower by one or two orders of magnitudein freshwater fish and plants at the site, possibly reflecting the naturally elevated concentrations ofuranium at the site /Tröjbom and Grolander 2010/.

11.4

Discussion

The dose rates for all investigated ERICA reference organisms were found to be several orders ofmagnitude below the screening dose rate of 10 µGy h–1. This suggests that the release under thecentral corrosion case would be of negligible concern for the protection of non-human biota in the
Forsmark area. The uncertainty of calculated dose rates did not affect these results significantly.
It is not possible to sample endangered species living in the Forsmark area today, or to get site representative samples from species that are not presently found in the area. Thus, endangered species, species
which are of economic or biological importance and species which are important for ecosystem function,
were mapped to similar ERICA reference organisms as far as possible. Based on the analyses of thesereference organisms, it is inferred that that the species of interest will also be subject to dose rates well
below the screening criterion.
The comparison of transfer parameters and the limited effect of size and morphology on absorbed
doses /Torudd 2010/, suggest that reference organisms give a sound representation of the species
of interest. Moreover substitution of generic parameter estimates with site data did not affect theresults in any significant way. Nevertheless, the comparison of transfer parameters high-lighted theimportance of collecting sufficient measurements from the site, as the representation of a numberof radionuclides and organism groups were limited in generic data, and as consistent differences
between site and ERICA data existed.
There are only two scenarios in SR-Site that contribute to a significant release of radionuclides to thebiosphere, namely the corrosion scenario and the shear load scenario (Chapter 3 and SR-Site main
report). The consequences for biota were calculated for the central calculation cases of the corrosion
scenario, but the conclusions can be generalised to encompass the whole corrosion scenario andthe shear load scenarios. This is because the predicted release rates of dose contributing nuclides inthe different release scenarios (and calculation cases) varies with less than an order of magnitude,(see Section 13.5.7 and 13.6.5 in SR-Site main report) and calculated dose rates were several ordersof magnitude below the screening dose rate. In a similar study relating to the planned repository atOlkiluoto, /­Smith and Robinson 2006/ identified some data gaps but concluded that the dose rates
predicted for all organism types were several orders of magnitude below those at which population
effects would be expected and, accordingly, below those at which effects on the individual may be
anticipated. These general results agree with the results obtained in the present study.

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The more complete and final study of the Olkiluoto case by /­Hjerpe et al. 2010/ was performed using
the full ERICA approach and tool, i.e. in a manner directly comparable to the present study. Theirresults concerning dose rates were similar and they concluded that any radiological consequencesof releases from the repository would be negligible. In their study, Hjerpe and co-authors listed several
remaining issues which were expected to require further work. Issues that are relevant for the SR-Siteassessment include the use of ecosystem models vs. a transfer factor approach in radionuclide transportmodeling, management of uncertainties, and difficulties in applying geometry constrain in the assessment of dose to non-human biota.
To some extent, the first issue agrees with the experience from the biosphere assessment in general,and the last two issues are applicable to the SR-Site assessment of non-human biota in particular. For
example, in this assessment the maximum environmental concentrations across multiple discharge
areas and points in time were cautiously used, instead of explicitly managing the uncertainties in thecalculated environmental activity concentrations. Difficulties in the translation of species morphology
to ellipsoidal geometries were also encountered for a few organism groups. However, morphology
was shown to have little or insignificant effect on calculated dose rates of the organisms used in theassessment /­Torudd 2010/.
Conclusion

Given that dose rates for all investigated organisms are far below the screening dose rate of 10 µGy h–1,
and the fact that identified uncertainties were found to have no significant effect on these result, it
follows that a potential release from the repository is highly unlikely to cause detrimental effects on
the survival and reproduction of individual organisms. This conclusion can be generalised to the two
significant release scenarios, and encompasses endangered species, species which are of economic or
biological importance, as well as species which are important for ecosystem function. As no effects
are expected on the level of the individual organism, effects on the level of populations, communities
and ecosystems are also highly unlikely. Thus, from this assessment it is concluded that neither negative effects of the repository on biodiversity, nor sustainable use of natural resources in the Forsmark
area are of concern. Nevertheless, SKB recognises that technical refinements of the methods used toassess the safety of non-human biota are ongoing, and SKB will keep the international developments
under review and refine the methods of analysis as required.

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12

The effect of uncertainties on the landscape doseconversion factors

The final risk estimate is built upon a number of assumptions and modelling results that areassociated with different degrees of simplifications, uncertainties and degree of caution. The aimof this chapter is to discuss the end points of the biosphere modelling, the LDFs, and evaluate theconsequensces of uncertainties in the light of results from altenative models and the knowledge
gathered during the site investigations.
The first section outlines the background, scope and limits of this chapter. Then the three following
sections examine the effect of system uncertainties, model uncertainties and parameter uncertainties
respectively. The results are summarized and it is concludes that the effects of quantified uncertainties
on LDF estimates are limited, and not expected to have any significant effect on assessment endpoints. The last section considers methodological improvements for future biosphere assessments.

12.1

Background

Large amounts of site-specific information have been collected in order to better understand transport
and accumulation of elements in the biosphere at the site. This understanding underpins conceptualand numerical models, and site data have been used to parameterise the radionuclide model used
to calculate environmental concentrations and subsequent human exposure. Uncertainties enter
all aspects of the data collection, interpretation, conceptual model formulation and mathematicalimplementation. In this chapter the effects of uncertainties on the calculated LDFs are examined.
Following the framework outlined by /­Galson and Khursheed 2007/ uncertainties were categorised into
three types: system uncertainties, model uncertainties and parameter uncertainties (see below). The
consequences of uncertainties in LDF were evaluated by exploring the reasonability of assumptions,by formulating and quantitative comparing results with those resulting from alternative assumptions,models and parameters, and by performing Monte-Carlo simulations. The results from Monte-Carlosimulations were also used in sensitivity analyses to identify the parameters contributing most to
uncertainty in the LDFs.
The description of uncertainties in the following text is primarily based on modelling of the long-term
release during an interglacial. That is, the effect of system, model and parameter uncertainties areevaluated by contrasting the maximum LDF from the interglacial period (referred to as SR-Site LDF
below) with an LDF resulting from an alternative model or set of assumptions. However, many of
the uncertainties underpinning LDFs for long-term release are shared by the modified LDF for pulse
release, since the major difference between the two is in the timing and duration of the release. The
reader is referred results and discussions in /­Avila et al. 2010/ for the effect of uncertainties that relates
specifically to the timing and duration of a pulse release.
For the overall safety assessment, the mean annual dose is calculated by multiplying the radionuclide
release to the biosphere with the LDF derived with the radionuclide model (Chapter 8). The impact
to non-human biota is calculated using activity concentrations in environmental media deliveredfrom the radionuclide model (Chapter 11), and consequently, many of the uncertainties in the LDF
calculations are also relevant for the calculations of dose rates to non-human biota.
The discussions in this chapter are focused on long-lived radionuclides that are expected to contributing most to dose of future human inhabitants. Examples are most frequently drawn from the resultsof Ra-226 (including daughter nuclides Pb-210 and Po-210) and I-129, and to a lesser extent from
Se-79, Np-237, Cs-135, and Cl-36. The first four of these radionuclides where selected becauseof their expected effect in long-term release (as indicated by the central corrosion case), where as
Cs-135, and Cl-36 are primarily expected to contribute to dose in a pulse release (see Section 13.5.4
in SR-Site Main report).

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12.2

System uncertainties

In the biosphere analysis, system uncertainties refer to uncertainties associated with the developmentof the biosphere and future human utilisation of natural resources. The handling of these two sourcesof uncertainty in the biosphere analysis is described and discussed below. The quantitative effects ofsystem uncertainty on LDF used in SR-Site is summarised in Table 12-2 at the end of this section.

12.2.1 Development of the biosphere
The main features of the Forsmark landscape are primarily determined by bedrock topography. It isargued in Section 7.3.3 that the landscape development during the present ice-free period will givean acceptable representation also of the landscape development during future ice-free periods ofrepeated glacial cycles (see also /­Lindborg 2010/).
Geometries of the landscape will change with glacial cycles, as bedrock is eroded the regolith isreworked by glacial and post-glacial processes. However the general geometrical patterns are expected
to be similar and the identified biosphere objects span a wide range of sizes and positions in thelandscape. Thus it is argued that the geometric properties of future objects will be captured in thevariation of identified biosphere objects. Uncertainties with respect to depth and development of
regolith layers were treated as parameter uncertainties, and consequently are handled in Section 12.4.2.
State of the biosphere object in relation to the timing and duration of release

The uncertainties with respect to timing and duration of releases reaching biosphere objects have beenhandled by assuming that the release from the repository will reach the assessed biosphere object(Section 8.1). The degree of cautiousness in this assumption was quantified by calculating LDF for thealternative and perhaps equally likely assumption that the release will only reach the biosphere object
after isolation from the sea /­Avila et al. 2010/. The simulations showed that accumulation during thesea stage had a significant effect on the maximum LDF on several (but not all) of the examined radio­
nuclides. For example the LDFs for I-129 (Figure 12-1), Se-79, Cs-135 and Np-237 were four, three, twoand 14 times lower, respectively, when no radionuclides were released under the sea stage as comparedto the SR-Site LDF. For these nuclides the SR-Site handling of this uncertainty was clearly cautious.
Location of release

Uncertainty with respect to which of the biosphere objects will be affected by a release has been handled
by assuming that the entire release will reach the biosphere object where the consequences will be theworst (Section 8.1). The degree of cautiousness in this assumption was quantified by calculating LDF
for the alternative assumption that all identified biosphere objects are equally likely to receive the release/­Avila et al. 2010/.
10-9
10-10

Sv/y per Bq/y

10-11
10-12
10-13
10-14
10-15
10-16
10-17
10-18
-9000

-4000

1000

6000

11000

16000

Time AD (y)Figure 12-1. Effect of start and duration of release on LDF for I-129. Annual dose per unit release is shown
as a function of release start and time. In the simulations 1Bq/y was released to biosphere object 121_03 at
the beginning of the interglacial period (blue line, SR-Site LDF), at the start and end of lake isolation (red andgreen lines respectively) or at the end of the interglacial period (purple line). Figure from /­Avila et al. 2010/.

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The LDF clearly vary between biosphere objects, and the degree of variation depends on the properties of radionuclides (Section 10.2). Thus the difference between the maximum interglacial LDF andthe expected value under the alternative assumption (i.e. the arithmetic mean, excluding object 105)
was typically a factor two for radionuclides where drinking water was an important pathway for
exposure (e.g. Ra-226). For radionuclides where exposure from food was the dominant pathway the
LDF under the alternative assumption was between four (Cl-36) and nine (I-129) times smaller thenthe SR-Site LDF. Thus the handling of this uncertainty was clearly cautious in SR-Site.
Climate conditions – reference climate

In the SR-Site assessment the uncertainty of future climates has been handled by assuming that areconstruction of the latest glacial cycle, (see reference glacial cycle in Section 6.2.1 and Climate
report) will cover the climatic variations that is expected in the future. According to the reference
glacial cycle, the initial period of a temperate climate domain will be followed by a 40,000 year ice
free period, where episodes of temperate and periglacial domains will alternate.
A separate LDF was calculated assuming that radionuclides from contaminated groundwater would
reach all biosphere objects during this period, but that the climate after the initial interglacial period
would prevent agriculture and the use of well water due to deep permafrost (Section 8.7.2). Fromthese simulations it was concluded that the maximum LDF from the period of temperate domain will
not be exceeded in the subsequent period with colder climate.

10-13
10-14

Cs-137

10-15

Maximum LDF
interglacial

Sv/y per Bq/y

10-16

Extendedtemperate
conditions

10-17

Referenceclimate

10-18
Temperate climate

Permafrost and talik

10-19

Permafrost
andno talik

Permafrost
conditions (0-1)

10-20
10-21
10-22

-9000
-7350
-5700
-4050
-2400
-750
900
2550
4200
5850
7500
9150
10800
12450
14100
15750
17400
19050
20700
22350
24000
25650
27300
28950
30600
32250
33900
35550
37200
38850
40500
42150
43800
45450
47100
48750
50400
52050
53700
55350
57000
58650

10-23

Time AD (y)Figure 12-2. Effect of fluctuating periods of temperate and permafrost conditions on LDF for Cs-135 fromsimulations of object 114. In the simulation the initial 20 ky interglacial was followed by a period wherelong periods of permafrost are alternated with short periods of temperate climate conditions. The LDF
from the simulation (blue line) is contrasted against LDF from constant temperate conditions in the object(dotted line) and the maximum LDF over all biosphere objects from interglacial conditions used in thesafety assessment (black line). The spikes in the simulated LDF correspond to short periods of temperateconditions when absence of permafrost allowed use of a deep drilled well. Background colour indicate
climate condition (green = temperate, blue = permafrost, light green = transition). In the transition
between temperate and permafrost conditions parameters affected by permafrost were averaged according
to the dotted line.

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However, cold climate and permafrost may effect a number of driving processes and a hydrologicaldescription of permafrost conditions in Forsmark suggest that permafrost will prevent discharge ofground water in most biosphere objects /­Bosson et al. 2010/. Thus, to evaluate whether the maximum
interglacial LDF could be exceeded during fluctuating periods of temperate and permafrost conditions,an alternative simulation was carried out. In this simulation a biosphere object having a potential troughtalik (Section 6.1.4.) was simulated allowing key temperature depend parameters (Section 9.3.1)
to fluctuate according to the reference glacial cycle /­Figure 12-2, Avila et al. 2010/. From thesesimulations it was concluded that the dose from a unit release during ice free conditions following
the initial interglacial was unlikely to exceed the maximum LDF used in SR-Site for examinedradionuclides (Ra-226, I-129, Se-79, Cs-135, Np-237 and Cl-36).
Climate conditions – global warming

The temperate domain covers a broad range of mean annual temperatures and precipitation, spanning
conditions for a Global warming scenario as predicted by for example /­BIOCLIM 2003, Rummukainen
2003/ and /­Kjellström et al. 2009/. Conditions characterising global warming have not been assigned
a special climate domain or a unique parameterisation in SR-Site surface system modelling. Instead
the uncertainty associated with global warming has been handled by calculating maximum LDF for
a 40,000 years extension of the initial temperate domain (Sections 8.2.7, Figure 10-1).
The potential effect of a systematic change in parameter values caused by a warmer climate was
evaluated for six radionuclides (Ra-226, I-129, Se-79, Cs-135, Np-237 and Cl-36). Sensitivity analysis(see Section 12.4.2) showed runoff to be the only parameters that had any quantitatively important
effect on LDF calculations, among the parameters that are expected to be significantly affected by awarmer climate /Löfgren 2010/. Moreover, a warmer climate is associated with an increased runoff/­Kjellström et al. 2009/ and for the examined radionuclides an increase in runoff was associated witha decrease in LDF. Thus, the uncertainties associated with a warmer climate were not expected to have asignificant effect on the maximum LDF for most radionuclides. For radionuclides with LDFs that would
potentially be affected (e.g. I-129 and Cl-36), the uncertainty was handled by the cautious use of a temperate parameter value /­Avila et al. 2010/.
Chemical evolution

Most of the easily weathered calcite in the upper regolith of the Forsmark area is likely to be dissolved
and washed out within a period of some thousands of years (Section 6.2.6). This means that the influence of the calcium-rich deposits on the terrestrial and limnic ecosystems will be reduced over time,with possible consequences for retention in soil and biological uptake /­Tröjbom and Grolander 2010/.
The uncertainty of potential effects of an outwash of calcite was handled as parameter uncertainty inthe biosphere analysis. That is, the uncertainty of parameters that describe retention (Kd) and biologicaluptake (CR) covers conditions with and without the influence of calcite. Moreover, the site data used
representing Kd and CR was based on samples from the two SKB sites Forsmark and LaxemarSimpevarp. There is no influence of calcite in Laxemar-Simpevarp and thus the differences in parametervalues between site were used to estimate the potential effect of calcite outwash. The difference in Kd
and CR parameters between the two site were small as compared to the natural variation at the sites(Nordén et al. 2010), and consequently it was concluded that the uncertainty associated with future lackof influence of calcite was appropriately handled as parameter uncertainty.

12.2.2 Use of natural resources by future human inhabitants
Occupancy of potentially contaminated areas

The uncertainties with respect to the degree that future humans will inhabit contaminated areas andthe extent to which they will be dependent of the natural resources in the object has been handled bycautious or even conservative assumptions. Below follows a discussion on why the assumption thata representative individual of the most exposed group spend all of her/his time in the contaminatedarea, and get her/his full supply of food and water from the biosphere object are a cautious assumption in a cultural and landscape use perspective.

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When agriculture is not possible, (as is assumed in a biosphere object where intrusion of salt water
is still frequent), most lakes and wetlands will support no more than one or a few individuals. Nonagricultural communities existing in the past or today are typically non-stationary, and it is hard to see
why future inhabitants of such cultures would restrict their foraging for food to one isolated lake witha surrounding wetland in the Forsmark area. In addition, during the terrestrial phase the production
in most biosphere objects could only support a fraction of the yearly energy demand of a family sizedgroup. It is possible that a family group or a small community living in the coastal area can be fully
supported by the fish production corresponding to the size of the sea basin of a biosphere object.
However these groups would be catching fish primarily from migrating stocks. Consequently, it islikely that individuals that feed only on natural food would obtain only a fraction of their diet from acontaminated discharge area, and thus contaminated food would be diluted considerably.
Sustainable agricultural is made possible only for a period of 50–100 years on drained organic soils,
which may provide the only arable land in several biosphere objects /­Lindborg 2010/. In contrast,
the thick and partly continuous layers of clay and sand in the central parts of Öregrundsgrepen canbe sustainably cultivated for thousands of years. Thus, a more realistic scenario for a future selfsupporting society in the area is that the mainly low contaminated central parts of Öregrundsgrepen
will be intensively cultivated and contribute the major part of the food consumed, even to the most
exposed group. Some of the small biosphere object may be cultivated during limited periods intime and complement the food produced in the more suitable agricultural areas in Öregrundsgrepen.
However even for self-sustained agricultural community it seems more likely that the biosphereobjects will primarily be utilised for extensive collection of naturally produced food. Thus, it isconcluded that the assumption of a representative individual of the most exposed group to spend
all time in the contaminated area and get his/her full supply of food and water from this biosphereobject seems improbable given the availability of non-contaminated land in the future landscape andthe organisation of present and historical societies.

Consumption of contaminated drinking water
The exposure from contaminated well water has been calculated by assuming that the release ofradionuclides is intersected by a well drilled in bedrock. The activity concentration in the well water
has been calculated by dividing the release rate (1Bq/year) by the well capacity, cautiously assumingthat the release is completely captured by the wells annual recharge. The release into the well ismade independently of the release into the biosphere object of 1Bq/year. For radionuclides wherecontaminated water and food are both important exposure pathways this handling is cautious ascompared to assuming that the release would transect a well or reach a biosphere object (as assumed
in previous biosphere assessments). However, the effect of this handling on LDF calculations will not
exceed a factor two as compared to the alternative handling.
The uncertainty of what type of water source that will be used for drinking in the contaminated area
has been handled by assuming that it is equally likely that humans and livestock will use surface water
and water from a well drilled in bedrock. Under this assumption, the well water is the dominating
exposure pathway by two orders of magnitude (or more) for short lived radionuclides (λ < 100 years).
However, for longer lived radionuclides the well is a less important pathway for exposure (Table 10-1).
The degree of cautiousness in this assumption was quantified by calculating LDF for the alternative
assumption that no release would reach a well drilled in bedrock /­Avila et al. 2010/. From this comparison, it was clear that for radionuclides expected to contribute to dose, Ra-226 was the only radionuclide
to be affected by the handling of the uncertainty associated with the use of contaminated well water.
For Ra-226 the LDF decreased by a factor two when well water was disregarded.

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Irrigation with contaminated water

In the Forsmark area, stream or lake water will be readily available in most biosphere objects anddrainage water can be stored for periods of draught. This also apply to a warmer climate than today
as runoff is expected to increase at the site with increased temperatures /Kjellström et al. 2009/.
Irrigation with well water is therefore considered to be unlikely in the area /­Löfgren 2010/, andconsequently for LDF calculations it was assumed, that vegetables are irrigated with contaminatedsurface water (Section 8.5.1). However as irrigation with water from a well drilled in bedrock cannot
be excluded, this uncertainty was examined by calculating LDFs under the alternative assumption thatwell and surface water are equally likely to be used for irrigation /­Avila et al. 2010/.
Irrigation considering well water increased activity concentrations in vegetables somewhat formost examined radionuclides, but the effects on radionuclides expected to contribute to dose wastypically below a factor two. From this comparison it was clear that the handling of the uncertainty
associated with the use of well water for irrigation did not affect the LDF for these radionuclides,with the exception for Ra-226. For Ra-226 the LDF increased by a factor two when well water wasconsidered for irrigation.
Long term irrigation

In organic soils that originate from drained wetlands in the Forsmark area is expected to be productive for agriculture only during a limited time (Section 8.3.3), and consequently long term use ofarable land has not been considered in the LDF calculations. However, future shallow wetlandsÖregrundsgrepen can probably be drained relatively easily, and the underlying minerogenic deposits
can be sustainably cultivated for thousands of years.
In an alternative simulation it was assumed that initially uncontaminated deposits of glacial and postglacial clay in Öregrundsgrepen were cultivated and irrigated for 10,000 years with contaminatedsurface water. The simulations showed that resulting activity concentrations in vegetables was
typically two orders of magnitude lower than those resulting from draining and cultivating a wetland
in an adjacent contaminated discharge area. That is, the accumulation of radionuclides in the wetland
is much higher than accumulation resulting from irrigation. From these simulations it was concluded
that the consequences of disregarding contamination through long-term irrigation were insignificant/­Avila et al. 2010/.
Land use and dietNo specific diet was pre-specified for the LDF calculations in SR-Site. Instead it was assumed
that the human inhabitants utilize all available food sources in a biosphere object, and that thecontribution of food types to the diet is proportional to the production capacity of the food types(Section 8.3.2). More over it is assumed that most of the wetland will be drained and cultivated when
agriculture is possible, and the uncertainty associated with the use of the contaminated land washandled by assigning an equal probability of all considered land use. Consequently the diet during
periods when agriculture is possible will be dominated by root crops, cereals and vegetables, withminor contributions from meat, milk and natural food (Table 12-1).
The effect of uncertainty with respect to human land use on LDF was examined by two Monte-Carlosimulations. Human diet of the first simulation was varied according to randomly allocation of landfor production of different agricultural crops or natural food, and to uncertainty in the productivityof each food type. In the second simulation, uncertainty in activity concentration (due to parameter
uncertainty) was added /­Avila et al. 2010/.
The simulations showed that for radionuclides expected to contribute to dose, the uncertainty in theactivity concentration in the food types caused an order of magnitude larger uncertainty in dose thanuncertainty introduced by land use and food productivity combined (Figure 12-3). Consequently
uncertainty with respect to human diet had a small effect on dose from food ingestion, and the differences between SR-Site calculations and the expected value from including uncertainty with respect
to land use and productivity was within a factor two. It was concluded from these simulations thatthe handling of the uncertainty with respect to human land use and productivity of food types had no
significant influence on SR-Site LDFs.

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1.6

All varied
Constant concentrations
SR-Site LDF
Contemporary diet

1.4

1.2

Frequency

1

0.8

0.6

0.4

0.2

0
−14

−13.5

−13

−12.5

−12

−11.5

−11

−10.5

−10

−9.5

−9

Sv/y per Bq/y, log−scale

Figure 12-3. Distribution of dose from Ra-226 (and daughter radionuclides) originating from ingestionof contaminted food. Results were obtained from two Monte-Carlo simulations: Red line corresponds todose distribution resulting from uncertainty in land use and food productivity. Black line corresponds todose distribution resulting from uncertainty in land use, food productivity and activity concentration in
food. The green vertical line shows the dose corresponding to SR-Site LDF. The purple vertical lines shows
the value corresponding to a diet based on contemporary food statistics.
Table 12‑1. Productivity and potential diet for food items used in the SR-Site assessment.
Modern diet was derived from national food statistics /­Avila et al. 2010/.
Production
Productivity(kgC m y )-2-1

Diet fromFood Statistic

Relative Production
Without agriculturea

With agriculturea(kgFW y-1)

Relative

Milk

0.169

4.3%

115b

12%

Meat

0.011

0.3%

72

14%

Vegetables

0.135

34%

51

3%

Tuber

0.127

32%

84

14%

Cereal

0.114

29%

71

45%

Fruit
48.3%

0.3%

23.5

2%

27

4.2%

Fish

2.7 · 10–4

Crayfish

3.1 · 10–5

5.5%

0.04%

1.7

0.2%

Berries

1.3 · 10–4

23.2%

0.03%

4.25

3%

Mushrooms

1.2 · 10

–4

21.5%

0.03%

1.3

0.03%

Game

8.3 · 10-6

1.5%

0.002%

25

5%

a
b

equal land and lake area,
unit is litre per year.

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139

The LDFs used in SR-Site were also contrasted against the dose from contaminated food that would
result from a diet derived from contemporary Swedish food statistics (further described in /­Avila et al.
2010/). The differences in LDFs for nuclides expected to contribute to dose was typically within afactor two. However, for Np-237, which gave peak exposure from natural foods, the SR-Site LDFs
was an order of magnitude larger than the LDF from the alternative diet, as it was not diluted byuncontaminated agricultural products. These results supported the conclusion that the handling of theuncertainty with respect to human diet, land use and productivity of food types did not significantly
affect SR-Site LDFs.
Table12‑2. Quantative effects of system uncertainties on maximum LDF from the interglacial period(SR-Site LDF). Source of uncertainty listed together with handling in the SR-Site assessment,
and alternative model/assumption. Comparisons were done for six radionuclides (Ra-226, I-129,
Np-237, Se-79, Cs-135, and Cl-36). A difference within a factor two between SR-Site LDFs and
LDFs calculated with an alternative approach was considered non-significant.
Source of uncertainty

SR-Site handling

Alternativemodel/assumptions

SR-Site handling comparedto alternative

State of biosphere object inrelation to the timing andduration of the releases.

All release to one object.
Maximum LDFs over thefull interglacial period.

Simulations with different
timing and duration of
release.

Cautious. Ra-226 notaffected.

Location of release

Maximum LDF over all
potential discharge areas

Development of the biosphere

In reference climate
Interglacial is the 20 k year
followed by alternating
periods of permafrost andtemperate conditions.

All biosphere objects
equally likely to recieve thefull release
Maximum LDF from theSimulations withinterglacial period represent alternating conditions after
the worst case during thethe intial 20 k year
70 k year simulation period. interglacial period.

Cautious

SR-Site handling supported.
LDF from alternative model
did not exceed SR-Site LDF.

Human utilization of natural resources

Consumption ofcontaminated drinking
water
Irrigation, source ofcontaminated waterLong term irrigation

Land use and productivity

Diet

12.3

Contaminated surface andwell water used for drinking
Surface water from
biosphere object used
for irrigation
Contaminated organic soil
cultivated for 50 years
Different use of wetland
for food production
equally likely
Diet proportional toproduction capacity inbiosphere object

Drinking water from surface Ra-226 cautious. No
water only (no deep well)significant difference othernuclides.
Irrigation with
Ra-226 non-cautious. No
contaminated surface and significant difference otherwell water
nuclides.
Inorganic soils irrigated for SR-Site handling supported,
thousands of years(contribution of long term
irrigation insignificant).
Land use and productivity No significant difference.
randomly varied
Diet from contemporary
Swedish food statistics

Np-237 cautious. No
significant difference othernuclides.

Model uncertainties

Model uncertainties refers to uncertainties arising from an incomplete knowledge or lack of understanding of ecosystems and the processes important for transport and accumulation at the site, andtheir representation in simplified models.
For example, complex ecosystems are represented in the radionuclide model by ten compartments.
These are considered internally homogeneous, and radionuclides entering a compartment are assumed
to become mixed within time scales of thousands of years (Section 8.4). The lower regolith isassociated with very slow hydrological flows and thus the assumption of mixing may be questioned.
Consequently the effect of a simplified model representation was evaluated by a finer discretisation(see 12.3.1 Representation of lower regolith for a summary). A thorough examination of the140

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uncertainties associated with the simplified representation of the biosphere with the radionuclide
model, including a discussion on the assumptions of the internal homogeneity of compartments, arepresented in /­Avila et al. 2010/.
Soil retention and biological uptake of radionuclides are complex processes. These have been
represented in the biosphere assessment by simple equilibrium parameters (for a description of CR and
Kd see Sections 9.2.6 and 9.2.7 respectively). The uncertainties associated with this highly stylised andsimplified approach are handled by using large intervals for parameter values spanning a wide range
of environmental conditions, and consequences of this for the uncertainty of LDF are discussed in
Secetion 12.4.2. The general assumptions and limitations of the Kd and CR approaches, in relation to
the natural variation at the site, are discussed in details in /­Nordén et al. 2010/, and their implications
for dose calculations are further examined in /­Avila et al. 2010/.
In the following sections, model uncertainties have been divided into uncertainties associated withthe model discretisation and vertical transport respectively. The handling of these uncertainties aredescribed and discussed, and the quantitative effects of model uncertainty on LDF are summarisedin Table 12‑3.

12.3.1 Discretisation
Size of the biosphere object

Several characteristics of the biosphere objects (including area of sub-catchment, timing of emergencefrom the sea and depth of regolith layers) affect the transport and accumulation of radionuclides. Someof these are related to the size of the object. For example, the steady state activity concentration in surface water is primarily determined by the watershed area of the object, and the steady state concentrationin the wetland peat is influenced by the size of the sub-catchment /Avila et al. 2010/.
The biosphere objects which yields the highest environmental activity concentrations are objects
with small sub-catchments and no inflow of surface water from upstream watersheds (Figure 12-4).
These objects can typically support 80 individuals from agriculture , and the most extreme object
has a local drainage area which is only three times as large as the lake/wetland area (0,24 km2). In
theory smaller biosphere objects, with smaller sub-catchments, could sustainably support a group of
approximately 10–20 individuals. However, a thorough analysis of the Forsmark landscape fails to
identify any discharge areas with a local drainage area less than 0.24 km2 and a reasonable likelihoodof persistent release from the repository /­Lindborg 2010/.
The basin of one of the original biosphere objects (121) was partitioned into three separate biosphereobjects in order to represent discharge directly into a stream or a wetland without going through alake stage. One of these objects, 121_03, turned out to be small with respect to both area of the subcatchment and watershed. Thus to examine the effect of this subdivision of a biosphere object, theLDF was calculated for the original undivided biosphere object. The LDF of most radionuclides was
lower when the undivided object 121 was used. However, as several other small biosphere objects
were included in the assessment and the contribution from the well is independent of the size of theobjects, the effect on the maximum LDF was small. Among radionuclides expected to contribute todose, only I-129 and Se-79 were significantly affected the division of object 121 (by a factor two andthree respectively).
Representation of lower regolith

The lower regolith is represented by a single compartment in the radionuclide model. As the verticalflow rates associated with the lower regolith are small, a single-compartment model will tend tounderestimate the time for break-through and over estimate dispersion of radionuclides in the regolith.
The effect of discretisation was examined by alternative models in which the lower regolith compartment was split into a varying number of compartments, stacked on top of each other /­Avila et al.
2010/. The retention of low-sorbing radionuclides was not affected by the model discretisation. For
radionuclides with a moderate or high Kd, the retention increased by orders of magnitude with finer
discretisation. However, this had a limited effect on the calculated LDFs as contamination from well
water was unaffected by retention in the lower regolith. Thus it was concluded that the uncertainty

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141

1010

108
107

105

114

123

101

108

107

126

121_01

121_02

117

116

120

124

Watershed

103

125

Sub-catchment

104
136

Biosphere object

105

118

106

121_03

Log Area (m2)109

Biosphere object

Figure 12-4. The size of biosphere objects and their sub-catchment and watershed. Objects are sorted inascending order of the watershed size and their position in the landscape is shown in Figure 7-11.

associated with the representation of the lower regolith layer had no significant effect on the LDF
for most nuclides expected to contribute to dose. Moreover, for radionuclides that were significantly
affected by the discretisation (e.g. the LDF of Cs-135 decreased with a factor five), the singlecompartment representation lead to cautious LDF estimates, as compared to estimates from higher
discretised alternative models.
Contamination through surface water

The LDFs used in the dose assessments were derived from simulations in which a constant release
rate (see above) was applied to the lower regolith layer of each biosphere object separately, disregarding the effects of contamination of downstream objects. This was considered and appropriate
approach for finding maximum doses in the landscape over the simulation period. The effect of thissimplified representation of contamination was examined by alternative simulations where the fulllandscape configuration (Figure 7-13) was captured, accounting for indirect contamination throughsurface water (see /­Avila et al. 2010/ for details).
Results from a simulation of chain of biosphere objects are presented in Figure 12-5. In this simulation
radio­nuclides were released to object 136, and objects downstream were contaminated through flowof surface water. For this, and all other possible chains of biosphere objects, the LDF was highest
in the first object of the chain that received radionuclides directly into the lower regolith. For mostobjects and radionuclides, the LDF from an indirect release was typically an order of magnitude lower
than that from a direct release. It was concluded that the simulations that only consider direct releaseto each biosphere object will give a realistic or cautious values of LDF for individual objects, as compared to results with more complex models where all objects and connections are explicitly modelled.
Moreover the maximum LDF (over all biosphere objects) where identical for landscape chains and thesimplified representation used in the biosphere analysis.

12.3.2 Vertical transport
Diffusion

Vertical transport of radionuclides in the radionuclide model is driven by both advection and diffusion. There are uncertainties associated with the description of diffusion in situations when verticalwater fluxes vary both in time and space. To quantify the relative contribution of diffusion to the vertical transport of radionuclides and how it affected the LDF estimates, simulations with an alternativemodel disregarding diffusion were carried out /­Avila et al. 2010/. Results from this analysis showed
LDFs to be insensitive to the presence of diffusion in the model and the difference between LDFs
including or excluding diffusion was within a factor two. Therefore, it is concluded that uncertainties
associated with the representation of diffusion in the radionuclide model has no significant effect on
the SR-Site LDFs.

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10-10
10-11

Sv/y per Bq/y

10-12

Se-79

10-13

I-129

10-14

Np-237

10-15

Ra-226

10-16

Cl-36

10-17

Cs-135

10-18
136

125

121_02

121_01

126

123

114

105

Biosphere objects

Figure 12-5. LDFs from one chain of biosphere objects. Radionuclides were released at a constant rate
to the lower regolith of biosphere object 136. Biosphere objects downstream were contaminated throughsurface water. LDFs are maximum values from an interglacial period. Biosphere objects appear in orderof the chain from left to right (see Figure 7-11). Figure from /­Avila et al. 2010/.

Advective transport from the lower regolith

The parameter describing upward hydrological flux from the lower regolith increase by a factor fivewhen the biosphere object develops from the sea stage to the lake/terrestrial stage. As a constantrelease rate has been applied to the biosphere in the simulations, an increased flow rate will be associated with a proportional decrease in the steady state inventory of radionuclides with a long half-life.
Thus, in the model, radionuclides may potentially be flushed out from the lower regolith when thebiosphere object is under transgression.
However, groundwater flow and transport from the geosphere to the biosphere is also expected tochange when the site develops from submerged to terrestrial conditions. For example, in the MARFA
flow transport simulations that illustrate the effect of varying flow conditions on final risk estimates,
the flow scaling factor for submerged conditions is a factor five smaller than the corresponding factor
for terrestrial temperate conditions (Section 13.5.6 in SR-Site main report). No flush of radionuclides
would be expected if this change in release rate was factored in to the biosphere simulations.
To illustrate how a potential flush associated with the change in vertical hydrological fluxes from thelower regolith affected the LDF, two simulations were carried out with a constant flux from thelower regolith during the whole simulation period. One with low flux, corresponding to the flux inthe sea stage and one with a higher flux, corresponding to flux in the terrestrial stage /­Avila et al.
2010/. These simulations also allow estimating the sensitivity of the LDF to the value of the flux
from the lower regolith. The alternative simulations showed that assumptions on flow rate had alimited effect on LDF calculations. Of nuclides expected to contribute to dose, Cs-135 was the only
one to be significantly affected by the alternative parameterisation. That is, SR-Site LDF was afactor two larger for Cs-135 than the estimate assuming a constant low flux from the lower regolith.
Thus, it was concluded that the handling of the uncertainty associated with flux rates from the lower
regolith during coastline passage did not have a significant effect on the SR-Site LDFs.

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Table 12‑3. Quantitative effects of model uncertainties on maximum LDF from the interglacial
period (SR-Site LDF). Source of uncertainty listed together with handling in the SR-Site assessment, and alternative model/assumption. Comparisons were done for six radionuclides (Ra-226,
I-129, Np-237, Se-79, Cs-135, and Cl-36). A difference within a factor two between SR-Site LDFs
and LDFs calculate with an alternative approach was considered non-significant.
Source of uncertainty

SR-Site handling

Alternativemodel/assumptions

SR-Site handling comparedto alternative

Size of biospher object
equals size of sea / lakebasin. Basin 121 diveded
into three biosphereobjects.
Represented by a single
compartment.

Basin 121 one biosphereobjectI-129 and Se-79 cautious. No
significant difference othernuclides.

Represented by multiple
stacked layers

Cs-135 cautious. No
significant difference othernuclides.
SR-Site handling supported.
Maximum LDF fromalternative model identical to
SR-Site LDF.

Discretisation

Size of biosphere object

Reprsentation of lower
regolith
Contamination may reachan object from direct releaseor by surface water fromanother object
Vertical transport

Contamination fromneighbouring objects
disregaded.

Simulations of allbiosphere objects
conceted according to thelandscape configuration

Representation of diffusion

Both advection anddiffusion represented inmodel.
Advective transport
increases from sea tolake/terrestrial stage

Transport by diffusion
excluded

Advective transport fromthe lower regolith

12.4

No significant difference

Constant high advection

No significant difference.

Constant low advection

Cs-135 cautious. No
significant difference othernuclides.

Parameter uncertainties and sensitivity analysis

Site-specific data, generic data, and expert judgement were used to determine best estimate values,
and to characterise the uncertainty in parameter estimates with probability density functions(Chapter 9). For each selected radionuclide, probabilistic simulations were performed by applying
Monte-Carlo simulations for the biosphere object which showed the highest LDF value in the deterministic simulations. The results from these simulations were also used in sensitivity analyses to identify theparameters contributing most to uncertainty in the LDFs.
Not all parameters were treated probabilistically in the evaluation of LDF uncertainties. Parameters that
represent habits and properties of the exposed individuals and future use of the biosphere were kept
constant for the uncertainty analysis calculations. In line with international recommendations /­ICRP
2006/, fixed, slightly conservative values were chosen for these parameters. For instance, the uncertainties in inhalation rates, water ingestion rates and food ingestion rates were not included in probabilistic
simulations. Some parameters that occur in the model as time series do not vary independently ofeach other and were therefore excluded from the probabilistic simulations. Instead, their effect on LDFs
were quantified by systematically varying parameters together, preserving their correlation structure/­Avila et al. 2010/.

12.4.1 Uncertainty analysis
The uncertainty analysis was carried out to estimate the effects of parameter uncertainties on LDFs.
This was done by propagating uncertainties in input distributions through the model to develop
distribution functions for the LDFs.

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LDF-distributions were derived for the point in time when the median of the distribution reached its
peak value for each examined radionuclide. The derived distributions were approximately log-normal
for most examined radionuclides, with a 90% confidence interval typically spanning two orders ofmagnitude (Figure 12-6). The LDFs were generally close to the median of the probabilistic simulations, and the LDFs used in the safety assessment thus reflect the central tendency, or the typicaloutcome, when parameter uncertainties are considered. However, it is the arithmetic mean value fromthe probabilistic simulations that represents the expected outcome if the parameter uncertainties were
to be taken into account.
The arithmetic means from the probabilistic simulations were systematically higher than the medianvalue due to the approximately log-normal distribution of LDFs. The difference between the deterministic LDFs and the arithmetic mean was within a factor three for most radionuclides, including
nuclides expected to contribute to dose (i.e. Ra-226, I-129, Se-79, Cs-135, Np-237 and Cl-36). Fora few radionuclides, inclusion of parameter uncertainties resulted in an expected value that was anorder of magnitude larger than the LDF used in the safety assessment (e.g. Tc‑99, Th‑230, U‑238
and Zr-93). However, the potential release of these radionuclides to the biosphere is expected to be
insignificant (SR-Site main report). This is discussed in more detail in /­Avila et al. 2010/.
From the analysis of time dependent parameters, it was shown that uncertainty associated withbounding assumptions on biomass and productivity for aquatic primary producers, and on water
retention for sea and coastal basins, had an insignificant effect on the LDF /­Avila et al. 2010/.
10–8

10–9

Sv/y per Bq/y

10–10

10–11

10–12

10–13

Zr-93

U-238

Th-230Th-229

Tc-99

Sn-126

Se-79

Ra-226

Pu-239Pa-231

Np-237

Ni-59

Nb-94

I-129

Cs-135

Cl-36

C-14

Am-241

10–15

Pu-242

Deterministic
Mean

10–14

Figure 12‑6. Effects of parameter uncertainty on maximum LDF estimates. LDF distributions were derived
from Monte-Carlo simulations (see text). The mean (square) from the simulations are contrasted against the
SR-Site LDF (circle). The box represents the 25th percentile, the median and the 75th percentile of the LDF
distribution from the simulation, and whiskers represents the 90 percent confidence interval. (Figure from/­Avila et al. 2010/.)

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12.4.2 Sensitivity analysis
The Monte-Carlo simulations described above were also used in a sensitivity analysis. This analysis
aimed to identify individual parameters with a strong influence on the assessment endpoint, andexamine to what extent the importance of these parameters varied with the development of abiosphere object. The results were focused on LDF variation with respect to the uncertainty of
individual parameters (i.e. not with respect absolute or proportional changes), and thus the results
identify parameters or processes where most benefit would be gained from improved understandingor measurements.
The results below were derived from regression analysis of first order effects on a logarithmic scale.
However, several other methods were applied to understand the effect of individual parameters on
the assessment endpoint. Details on all methods and the results are presented in /­Avila et al. 2010/.
It was clear from the sensitivity analyses that the importance of a parameter on LDF varied withthe development of the biosphere objects. This was not unexpected as major process rates andpathways change throughout the development of an object. For example, for Ra-226 uncertainty inthe properties of regolith layers and fish productivity caused the majority of uncertainty in the LDF
during the sea stage. Where as to uncertainty in well capacity and parameters describing plant uptake
dominating LDF uncertainty during the terrestrial stage (Figure 12-7).
Althrough sensitivity analyses were carried out for the full simulation time, it is the maximum
LDF through­out the interglacial period that is used to assess the safety of future human inhabitants(Chapter 10). The Ra-226 LDF reaches its maximum in the terrestrial stage at the end of the temperatedomain (9400 AD, Table 10-1). At this point in time, uncertainty in well capacity explains 48% of
LDF uncertainty, and the corresponding numbers for plant uptake (CR) of Ra-226 and its daughter
Pb-210 is 6% and 20%, respectively (Figure 12-8). Uncertainty in the parameter describing
retention in the low regolith layer (Kd_regolow) explains an additional 5% of LDF uncertainty. The
standardized regression coefficients from the sensitivity analysis of first order effects indicate boththe importance and direction of the effects of a parameter on LDF. Thus as expected, the LDF for
Ra-226 would decrease with an increase in well capacity or in the Kd of the low regolith layer.
Similarily it would increase with an increase in plant uptake (see wellCapac, kD_regoLow[Ra-226],
cR_soilToVegetab[Pb-210] and cR_soilToVegetab[Ra-226] in Figure 12-8a).

First order sensitivity index

1

R2

0,9

KD regolow (Ra-226)

0,8
KD regolow (Ra-226)

0,7
0,6
0,5

Well capacity

KD regomid (Ra-226)

0,4
0,3
0,2

Depth regomid

CR soil to vegetables (Ra-226)

0,1Fish productivity

CR soil to vegetables (Pb-210)
57000

52500

48000

43500

39000

34500

30000

25500

21000

16500

8000

12000

4850

4400

3950

3500

3050

2600

2150

0

1700

-4500

-9000

0

Time AD (y)Figure 12-7. Effects of parameter uncertainty on LDF uncertainty for Ra-226 as a function of time. The
first order sensitivity index indicates the proportion of uncertainty in LDF that is explained by uncertainty
in each of the parameters. The dotted line shows the fraction of the total parameter uncertainty in LDF thatis explained by first order effects of the model parameters. The vertical lines represents (from left to right)
the start and end of lake isolation, the time when the wetland can first be converted to arable land and theend of the interglacial period, respectively. The analysis is based on the fit of a regression model to the resultsfrom Monte-Carlo simulations of biosphere object 121_03. The sensitivity analysis was carried out on alogarithmic scale. Figure from /­Avila et al. 2010/.

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wellCapac

Ter_kD_regoUp[I-129]

Ra-226cR_soilToVegetab[Pb-210]

I-129

Ter_kD_regoMid[I-129]
cR_soilToTuber[I-129]

kD_regoLow[Ra-226]
cR_soilToVegetab[Ra-226]

kD_regoLow[I-129]

Aqu_z_regoMid_gl_lake

cR_soilToVegetab[I-129]

Lake_z_regoLow

z_regoMid_gl_basin

Agri_dens_regoUp

runoffLake_adv_low_mid

Aqu_z_regoMid_gl_lake

Ter_kD_regoMid[Ra-226]

Ter_dens_regoUp

runoffTer_cR_pp[I-129]
-1

-0,5

0

0,5

1

-1

Standardized regression coefficient, log data (R2 =0.80)

Ter_kD_regoUp[Se-79]

cR_soilToVegetab[Cs-135]

cR_soilToVegetab[Se-79]

Aqu_z_regoMid_gl_lake

cR_soilToTuber[Se-79]

Lake_z_regoLow

runoffcR_soilToTuber[Cs-135]

z_regoMid_gl_basin

tC_cowMilk[Cs-135]

Aqu_z_regoMid_gl_lake

cR_soilToCereal[Cs-135]

cR_soilToCereal[Se-79]

Agri_dens_regoUp

Agri_dens_regoUp

Ter_kD_regoUp[Cs-135]
-0,5

0

0,5

0,5

1

Standardized regression coefficient, log data (R2 =0.87)

1

Cs-135kD_regoLow[Cs-135]

kD_regoLow[Se-79]-10

wellCapac

Se-79

Ter_kD_regoMid[Se-79]-0,5Standardized regression coefficient, log data (R2 =0.80)

-1

-0,5

0

0,5

1

Standardized regression coefficient, log data (R2 =0.81)

Figure 12-8. Effects of parameter uncertainty on uncertainty in maximum LDF for four radionuclides. The sizeand direction (negative or positive) of vertical bar reflects the effects of uncertainty in individual parameters on
LDF uncertainty. The R2 value indicates the fraction of the total uncertainty in LDF that is explained by firstorder effects of the model parameters. Parameter name are explanied in Appendix 2. The results are based onMonte-Carlo simulations in biosphere objects 121_03 (Ra-226, I-129, Se-79) and 124 (Cs-135), respectively.
Figure from /­Avila et al. 2010/.

As a rule, parameter uncertainty associated with the dominating exposure pathway was the major
source of LDF uncertainty, and consequently the relative importance of parameters for LDF
uncertainty varied with radionuclide properties (for examples of dominating exposure pathways for
expected dose contributing radionuclides see Table 10-1). Detailed results on the source of uncertainty of individual radionuclides and the influence on individual parameters on LDF uncertainty arepresented and discussed in /­Avila et al. 2010/.
Uncertainty in parameters that describe retention in regolith layers (Kd) and plant uptake (CR)explained a large fraction of LDF uncertainty for many radionuclides. For medium sorbing nuclides
with long half-life (e.g. I-129 and Se-79) the uncertainty of these parameters clearly dominated LDF
uncertainty (see e.g. parameters names with kD or cR i Figure 12-8). An increase in plant uptake andretention in the upper and the mid regolith layers was always associated with an increase in LDF,
whereas an increase in the retention of the low regolith layer was associated with a decrease in LDF(Figure 12-8, Avila et al. 2010).
The primary reason for the large impact of Kd and CR values on LDF, was that the distribution ofthese parameters was typically very wide. That is, as these parameters were estimated from combining site and literature data they covered a broad range of environments. As systematic variation due
to for example climate, geographic location, type of ecosystem or measurement techniques were notpartitioned out before site and literature data were combined, the derived PDFs for these parameters
are likely to overestimate the natural variation expected at the site /­Tröjbom and Nordén 2010/.
Thus it is expected that model uncertainty could be significantly reduced if the uncertainties in theseparameters could be limited to reflect natural variation at the site. It may also be possible to reduce
uncertainties for some radionuclides by describing sorption and plant uptake by alternative modelling approaches which are less sensitive to parameter uncertainties.
The development of biosphere objects are captured by several parameters that vary systematically in time (Table 7-2). To assess the sensitivity of LDF to variation in the predicted landscapedevelopment, alternative parameter sets were derived by systematically varying key process rates in
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the coupled regolith-lake development model (see Chapter 5 in /­Brydsten and Strömgren 2010/ fordetails). From this analysis it was concluded that LDF for nuclides expected to contribute to dose,
was insensitive to changes in the predicted landscape development /­Avila et al. 2010/.

12.5

Overall uncertainty

The LDFs obtained from the biosphere assessment are best estimates for a representative individualin the most exposed group from deterministic simulations. These deterministic simulations are the
combined result of process understanding, the most precise description of the site available andrelevant assumptions on the use of natural resources by future human inhabitants.
The effect of uncertainties on the calculated LDFs was examined in this chapter. Uncertainties
were divided into three categories for this analysis ; system uncertainties, model uncertainties andparameter uncertainties. The consequences of uncertainties in LDF calculations were carried out by
discussions of the reasonability of assumptions, by formulating and quantitatively exploring alternative assumptions, models and the parameters, and by performing Monte-Carlo simulations.
The philosophy of the biosphere assessment has been to make estimations of landscape dose conversion factors as realistic as possible, based on the knowledge of present-day conditions at Forsmark
and of the past and expected future development of the site. From the summary of quantitative
effects of system and model uncertainties (Tables 12-2 and 12-3, respectively) it is evident that thehandling of these types of uncertainties has been balanced for the examined radionuclides. /­Avila
et al. 2010/.
The effect of parameter uncertainties on LDF calculations were assessed with both systematic andrandom variation of model parameters. From these assessments it was concluded that uncertainties
in parameters which reflected landscape development had limited effect on LDF estimates. However,from the Monte-Carlo simulations it was clear that parameter uncertainty was the major source of
LDF uncertainty, and that the effects of examined system and model uncertainties fell within the 90
percent confidence interval corresponding to parameter uncertainties (Avila et al. 2010, Figure 12-9).
Moreover it was noted that the handling of parameter uncertainties was not cautious as the expectedvalue from the probabilistic simulations were systematically higher than the LDFs used in the safetyassessment.
The LDFs are based on best estimates of all available parameters, i.e. they reflect typical values
representing available knowledge from the site and literature. Though a great effort was put into theprocess to derive meaningful PDFs (see Section 9.1), information from the site was occasionally insufficient, resulting in PDFs reflecting the span reported in the literature rather than the natural variation
expected on the site. Moreover, the Monte-Carlo sampling did not incorporate dependence between
parameters (e.g. a negative correlation between CR for plants and Kd for soil), and the sampling was notdesigned to give precise estimates in presence of long-tailed distributions. These and other limitationsin probabilistic simulations are discussed in /­Avila et al. 2010/. Nevertheless, the difference between
deterministic calculations and expected values from the probabilistic simulations gives an indication of
the potential impact of parameter uncertainties. Thus if the final risk estimates are close to the regulatory
limits, (as compared to difference between LDFs and the expected value from the Monte-Carlo simulation), it would be reasonable to make an effort to reduce the parameter uncertainty of dose contributing
radionuclides.
A representative individual of the most exposed group is assumed spend a life time in the discharge
area where the environmental concentrations lead to the highest dose, and to get his or her full supplyof food and water from the contaminated area. A fairly sized group of individual (>40) can be sustainably supported by agriculture from a transformed wetland in any of the biosphere objects. However,
the assumption that a representative individual of the most exposed group should be totally dependent
on resources from a small area seems improbable given the availability of non-contaminated land in
the future landscape and the organisation of present and historical societies (Section 6.1.8). Though
no attempt has been made to quantify a reasonable degree of dilution that would result from theconsumption of non-contaminated food and water due to e.g. trading or migration, the assumption on
the behaviour of future human inhabitants are inherently cautious or even conservative.

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10-10

10-8

Ra-226

I-129
10-9

10-10
10-12

Discretisation

Use ofnatural resources

Discretisation

Parameter uncert

Constant advection - low

Diffusion

Constant advection - highSurface water contam

Size of object

Layers of rego low

Land use

Irrigation waterLong term irrigation

Beyond interglacial

Development

Water consumption

Location of release

10-12
Timing of release

Advection low

Transport

Parameter uncert

Diffusion

Advection highSurface water contam

Deep regolithLand use

Use ofnatural resources

Size of object

Long term irrigation

Irrigation water

Reference climate

Development

Water consumption

10-13

Release time

10-11

Discharge area

Sv/y per Bq/y10-11

Transport

Figure 12-9. Uncertainties of LDF for Ra-226 and I-129. Grey circles represents LDFs calculated withalternative assumptions/models, where as white circle represents the expected value taking parameter
uncertainties into account (whiskers represents the 90 percent confidence interval).The dotted line
represents the maximum LDF from the interglacial period.

Extensive analyses were carried out to characterise which parameters have a strong influence on theassessment endpoint (see /­Avila et al. 2010/ summarized above). The sensitivity analyses demonstrated
that the influence of individual parameters on LDFs varied between radionuclides and depended on
the development of the landscape. The analyses highlighted that a large proportion in LDF uncertainty
can be attributed to parameters describing the partitioning of radionuclides between the solid and liquid
phases (i.e. Kd) and biological uptake (i.e. CR). For most radionuclides, a combination of generic andsite data was used to estimate these parameters, indicating the potential benefit of additional site measurements that would reveal systematic natural variation and reduce measurement errors. Alternatively,
LDF uncertainty could be reduced by describing sorption and uptake of radionuclides with models thatare less sensitive to parameter uncertainties.
Conclusion

A systematic evaluation of the effects of uncertainties on the SR-Site LDFs demonstrated that thehandling of system and model uncertainties was balanced. Site representative values were used formodel parameters, and their uncertainties were not handled in a cautious way, where as the definitionof the most exposed group was clearly cautious. However, the effect of quantified uncertainties waslimited and is therefore not expected to have a significant effect on the assessment endpoint. Thus taken
together we are confident that the maximum LDFs used in SR-Site are robust estimates for the most
exposed group, reflecting process understanding and the most precise description of the site available.
Nevertheless, SR-Site biosphere recognises that there is a potential to reduce uncertainties, in particularwith respect to processes describing the partitioning of radionuclides between the solid and liquid
phases (i.e. Kd) and biological uptake (i.e. CR). Thus if the final risk estimates are close to the regulatory limits, it would be reasonable to make an effort to reduce the uncertainty associated with theseprocesses, at least for dose contributing radionuclides.

12.6

Feedback for future Site investigations and the biosphere
RD&D program

In the above analysis several areas where benefit from improved understanding or measurements
would reduce uncertainty in dose calculations were identified. Implications from these findings
for future site investigations and for the biosphere research and development programme (RD&D
programme) are briefly discussed below.
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The LDF calculations for long-term release are based on the assumptions that the release from therepository will reach the biosphere objects where the consequences for human inhabitants will beworst. Moreover, the release is assumed to reach an object at a constant rate for the entire assessment
period. Although these assumptions are not unrealistic with respect to geo-hydrological predictions,they were shown to be cautious (Table 2-2). Thus, reducing uncertainties with respect to the locationand timing of the release would result in more reliable dose estimates.
Along these lines, SKB plans to re-examine the possibility to represent the release to the biospherewith a probability weighted function that captures the timing and location of deep groundwater
discharge according to relevant geo-hydrological predictions. For near future calculation scenarios,
the release from the geosphere is used as a direct and time-dependent input to the radionuclide model(Section 10-4). An advantage of this approach is that it allows estimates of total dose that corresponds
to a most exposed group which is well defined in time and space. A similar approach could be used tolong-term release. Thus, the possibility to complement the unit release approach with a realistic releaseterm that accounts for the relevant driving hydrology will be further investigated (see e.g. MARFA
simulations with flow scaling, Section 13.5.6 in SR-Site Main Report).
A major part of the quantified uncertainty in LDF could be attributed to parameters describing thepartitioning of radionuclides between the solid and liquid phases (Kd) and by parameters describing
biological uptake (CR). A high uncertainty in parameter estimates of Kd and CR could often be attributed to the lack of site data, and in these cases the parameter uncertainty reflects the variation in thedata reported to international databases rather than natural variation expected at the site. Consequently,
a better coverage of concentration measurements of a few elements (including Ra and I) is desirable
for all environmental media, and there is a need to obtain concentrations of all elements in agricultural
products and soils similar to those expected in a future Forsmark landscape.
In order to predict sorption and biological uptake in the future when environmental conditions may
be different from today, it is important to increase our understanding of the processes that are likely
to affect Kd and CR at the site. A better process understanding may be achieved by identification ofsystematic variation in element concentrations and ratios at the site (and similar sites), with respect
to for example type of ecosystem, soil and sediment conditions, and to background fluxes due to e.g.
plant uptake, mineralisation, deposition and weathering. Studies of element pools and fluxes offer an
important perspective on element transport and retention at larger scales, and results from studies atthe catchment and landscape levels will be continued, and possibly used to validate the assumptions
and approaches used in the assessment model.
It may also be possible to describe sorption and/or biological uptake by alternative modelling approaches
that are less sensitive to parameter uncertainties. Hence, the coming RD&D program will also aim atdeveloping assessment tools that explicitly describe biological uptake as a function of physiologicalprocesses /Kumblad and Kautsky 2004 /. For primary producers this means that both active and passive
uptake will be considered accounting for bioavailability of radionuclides and competition between
radioactive and stable isotopes /e.g. Avila 2006/. Similarly, uncertainty in Kd values for specificradionuclides may be reduced by explicitly modelling radionuclide transport as a function of known
chemical processes as in reactive transport models / Piqué et al. 2010/.
The assumptions on the behaviour of future human inhabitants are inherently cautious or even conservative. Further literature reviews of present and historic self-sustained communities will aim to
replace a cautious approach by reasonable assumption on human habits associated with sustainable
land use in a cultural and landscape context.
Finally, the analysis of non-human biota high-lighted the importance of collecting sufficient measurements from the site, as the representation of a number of radionuclides and organism groups arelimited in generic data on non-human biota.

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Sohlenius G, Hedenström A, 2009. Platsundersökning Forsmark. Stratigrafiska undersökningar
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Sonesten L, 2005. Chemical characteristics of surface waters in the Forsmark area. Evaluation ofdata from lakes, streams, and coastal sites. SKB R-05-41, Svensk Kärnbränslehantering AB.
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Sterner R W, Elser J J, 2002. Ecological stoichiometry: the biology of elements from molecules
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Forsmark area
1628000

1630000

1632000

1634000

1636000

1638000

1640000

1642000

1644000

1646000

1648000

6712000
6710000

6710000

6712000

Svensk Kärnbränslehantering AB

SKB/skbebo 2011-02-22 11:14

6708000

101

6708000

D:\GIS\SR_Site\Bearbetad_data\Mxd_TR_10_09\AppendixKarta.mxd

1626000

Appendix 1

1056706000

6706000

Stream107

Biosphere Object

108

Gräsö
6704000

6704000

114
117

Biotest BasinÖregrundsgrepen

6702000

6702000

SFR

Nuclear Power Plant121_03

Model area landscape model

Catchment areas future lake
Present wetland

Topography, m.a.s.l.

120

Norra Bassängen
125 124
Puttan6700000

121

6700000

Present lake

Future lake

116

118

Present shoreline

123

136

126

Bolundsfjärden

-31.9 - -20-19.9 - -106698000

146

6698000-58.8 - -32

Börstilåsen

-9.9 - -5-4.9 - 0

6696000

6696000

0.1 - 5
5.1 - 1010.1 - 15

Forsmarksån
6694000

6694000

15.1 - 2000.5

16260001

20.1 - 51.1

2 Kilometers

1628000

1630000

1632000

1634000

1636000

1638000

1640000

1642000

1644000

1646000

1648000

Figure A-1. Map over the Forsmark area today. Numbers within biosphere objects show object id-number. The sizes of biosphere objects shown on the map represent sizes during the lake and terrestrial stages in the landscape succession (seeFigure 7-8 for object sizes during the marine stage). The basin of biosphere object 121 was subdivided into 3 separate objects, of which biosphere object 121_03 is shown on the map. See Figure 6-6 for the location of the planned repository.
TR-10-09

159

Appendix 2
Glossary of terms and acronyms used in the SR-Site biosphereassessment
Term

Definition

abiotic

Non-living physical or chemical component or process.

autotroph

Organism that utilises photosynthesis or chemosynthesis to build uporganic carbon.

basin

In the SR-Site terminology, a basin is the drainage area of a biosphereobject (e.g. lake), minus the drainage area of any upstream object.
When the basin is below sea level, the basin equals the biosphere object.

biosphere

That part of the environment normally inhabited by living organisms.

biosphere object

A part of the landscape that potentially will receive radionuclides released
from a repository.

bioticLiving ecosystem component or process involving living organisms.

climate cases

SR-Site describes climate cases, which are possible future climate
developments at Forsmark.

climate domain

A climatically determined environment with a specific set of characteristic
processes of importance for repository safety.

CR (concentration ratio) The CR is used to calculate uptake of radionuclides by biota and isdefined as the element-specific concentration ratio between the concentrations in biota, and in the surrounding media (soil or surface water).
conceptual model

A qualitative description of important components and their interactions.

deterministic analysis

Analysis using, for key parameters, single numerical values (taken to havea probability of 1), leading to a single value for the result.

DEM (digital elevation
model)The DEM describes topography and bathymetry of a certain area. The DEM
is a central data source for the site characterisation, and is used as input tomost of the descriptions and models produced for the surface system.

discharge points /area

The area where deep groundwater reaches the ground surface.

dose

Dose, as used in SR-site refers to the mean annual dose of the most exposedgroup. The calculated dose accounts for retention of radionuclides in thehuman body and exposure from daughter radionuclides, as well as radiation
sensitivities of different tissues and organs.

dose rate to biota

Dose rate to biota represents mean absorbed dose rates in the whole bodyof a given radionuclide and is expressed in uGy h–1.

ecosystem model

Conceptual or numerical representation of an ecosystem, divided into
compartments, and its included processes.

effective dose(or effective dose equivalent). A measure of dose designed to reflect therisk associated with the dose, calculated as the weighted sum of the dose
equivalents in the different tissues of the body.

ERICA toolComputer software used to obtain activity concentrations and radiologicaleffects on different types of non-human biota.

TR-10-09161

exposure

The act or condition of being subject to irradiation. (Exposure should
not be used as a synonym for dose. Dose is a measure of the effects of
exposure.)
External exposure. Exposure to radiation from a source outside the body.
Internal exposure. Exposure to radiation from a source within the body.

functional group

A group of organisms with a common function in the ecosystem,e.g. primary producers, filter feeders etc.

geosphere

Those parts of the lithosphere not considered to be part of the biosphere.
In safety assessment, usually used to distinguish the subsoil and rock(below the depth affected by normal human activities, in particular
agriculture) from the soil that is part of the biosphere.

glacial cycle

A period of c. 120,000 years that includes both a glacial (e.g. theWeichselian) and an interglacial.

GPP (gross primary
production)

Total fixation of carbon by photosynthesis, including respiration (cf. net
primary production, NPP).

heterotroph

Organism that uses organic compounds produced by autotrophs.

hydrodynamic model

The hydrodynamic model gives outputs of annual mean flows between
adjacent marine basins and water retention time for each individual basin.

hydrological model

Hydrological modelling performes simulation of surface and near surface
water flow. Each model run have different environmental settings as input
parameters. The hydrological modelling utilises GIS, as well as MIKESHE and ConnectFlow as numerical modelling tools.

infilling

Infilling describes the combined process of sedimentation and organogenic
deposition, turning lakes into wetlands.

interglacial

A warm period between two glacials. In SR-Site an interglacial is definedas the time from when the ice sheet retreats from the area (time ofdeglaciation) to the time for the first occurrence of permafrost.

Kd

Soil/liquid partition coefficients are defined as the ratio between theelement concentrations in the solid and liquid phases.

landscape developmentmodel

A model at landscape level that describes the long-term development of alandscape. The model is used to describe time-dependent properties of thebiosphere objects that are input parameters to the Radionuclide model.

landscape model

In SR-Site, the landscape model is a description of where biosphereobjects are situated in the landscape and how they are hydrologicallyinterconnected.

LDF (landscape doseconversion factor)

The LDF is a radionuclide-specific dose conversion factor, expressed in
Sv/y per Bq/y. The LDF represents the mean annual effective dose to arepresentative individual from the most exposed group, resulting froma unit constant release rate, or alternatively per unit released in a single
pulse to the biosphere of a specific radionuclide. The LDF relates a unit
release rate to dose.

mass balance model

The mass balance model calculates the total sum of major sources andsinks for individual chemical elements in the landscape.

most exposed group

In SR-Site, the expression most exposed group refers to the group ofindividuals subjected to the highest exposure during any time period.

NEP (net ecosystemproduction)

The sum of gross primary production and ecosystem respiration.

162

TR-10-09

NPP (net primary
production)

The balance between gross primary production and plant respiration(cf. gross primary production, GPP).

PANDORAThe Matlab/Simulink toolbox used for implementation of the SR-Siteradionuclide model.

probabilistic analysis

Mathematical analysis of stochastic (random) events or processes andtheir consequences.

radionuclide model

Model used to calculate radionuclide inventories in different compartmentsof the biosphere, radionuclide fluxes between the compartments andradionuclide concentrations in environmental media (soil, water, air andbiota). Exposure calculations for humans to estimate LDF’s are includedin the radionuclide model, whereas exposure of non-human biota is
calculated separately. The radionuclide model utilises PANDORA andEcolego modelling tools.

regolith

All matter overlying the bedrock are collectively denominated regolith.
This includes both minerogenic and organogenic deposits as well as
antropogenic landfills.

RDM (regolith depth
model)The RDM interpolates observation points of analysed vertical distributionof regolith into 3-dimensional regolith extension.

RLDM (coupled
regolith-lakedevelopment model)

The RLDM is divided into a marine module that predicts the sediment
dynamics caused by waves, and a lake module that predicts infilling oflakes. The model forecasts regolith distribution and thickness of different
strata at time-steps.

sub-catchment

The drainage area of a biosphere object minus the drainage area of theinlets to the object.

terrestrialisation

The transfer of an aquatic ecosystem (marine or limnic) to a terrestrial
ecosystem.

watershed

The drainage area of a biosphere object.

TR-10-09163

Appendix 3
Parameters for calculations of environmental concentrations
Parmeter Name

Description

Unit

Type

ReportSource File

Half_life

Radionuclide half-life.

year

Nuclidespecific

TR-10-07

ParametersES.xls

Landscape geometry
Aqu_area_obj

Water area in the lake basin.

m2

TR-10-05

area_subcatch
area_wshed

Area of the subcatchment.
Watershed area.

m2
m2

depth_averAverage water depth.

mdepth_max

Maximum water depth.

m

growth_regom/yearParameters_TS_
all_basins.xls
ParametersSS.xls
Parameters_TS_
all_basins.xls
Parameters_TS_
all_basins.xls
Parameters_TS_
all_basins.xls
Parameters_TS_
all_basins.xls

res_rate

Average accumulation rate of
sediment calculated for lakeand marine bottoms.
Resuspension rate.

Site Specific(Time Series)
Site SpecificSite Specific(Time Series)
Site Specific(Time Series)
Site Specific(Time Series)
Site Specific(Time Series)

TR-10-05

ParametersTS.xls

sed_rate

Sedimentation rate.

TR-10-05

ParametersTS.xls

Ter_area_obj

Area with peat in the lakebasin.
Point in time when wetland is
2 m above sea level.
Point in time when ingrowth ofwetland stops.
Point in time when lake
isolation starts.
Point in time when lake
isolation is completed.

TR-10-05

year

Site Specific(Time Series)
Site Specific(Time Series)
Site Specific(Time Series)
Site SpecificTR-10-05

Parameters_TS_
all_basins.xls
ParametersSS.xls

year

Site SpecificTR-10-05

ParametersSS.xls

year

Site SpecificTR-10-05

ParametersSS.xls

year

Site SpecificTR-10-05

ParametersSS.xls

mGeneric

TR-10-01

ParametersUC.xls

kg DW/m3

Site SpecificParametersSS.xls

kg DW/ m3

Site SpecificTR-10-02
TR-10-03
TR-10-01

m3/ m3Site SpecificTR-10-01

ParametersSS.xls

kg DW/ m3

Site SpecificTR-10-02
TR-10-03

ParametersSS.xls

kg DW/m3

Site SpecificParametersSS.xls

m3/m3

Site Specificm3/m3

Site SpecificTR-10-02
TR-10-03
TR-10-02
TR-10-03
TR-10-02
TR-10-03

m3/m3

Site SpecificParametersSS.xlsm

Site Specific(Time Series)

TR-10-02
TR-10-03
TR-10-05m

Site SpecificTR-10-05

ParametersSS.xls

Physical constantthreshold_agriculture
threshold_end
threshold_start
threshold_stop
Regolith
Agri_z_regoUp

Depth of the agricultural upper
regolith layer
Aqu_dens_regoMid_gl
Density of glacial clay in the
middle layer of the regolith.
Agri_dens_regoUp
Density of the agricultural
upper regolith layer.
Agri_poro_regoUp
Porosity of the agricultural
upper regolith layer.
Aqu_dens_regoMid_pg Density of the postglacial
sediments in aquatic middle
layer of regolith.
Aqu_dens_regoUp
Density of the aquatic upper
layer of the regolith
Aqu_poro_regoMid_gl
Porosity of the glacial clay inaquatic middle regolith layer.
Aqu_poro_regoMid_pg Porosity of postglacial
sediments in aquatic middle
regolith layer.
Aqu_poro_regoUp
Porosity of the aquatic upper
regolith layer.
Aqu_z_regoMid_pg
Depth of postglacial clay inaquatic middle regolith layer
under sea, lake or stream
Aqu_z_regoMid_gl_lake Average depth of glacial
deposits in lake.

TR-10-09

kg DW/(m2year)kg DW/(m2year)m2

TR-10-05
TR-10-05
TR-10-05
TR-10-05
TR-10-05

ParametersSS.xls

ParametersSS.xls
ParametersSS.xls

Parameters_TS_
all_basins.xls

165Parmeter Name

Description

Unit

Type

ReportSource Filedens_regoLow

Density of the lower regolithlayer (till).

kg DW/m3

Site SpecificParametersSS.xls

Lake_z_regoLow

Depth of the lower regolith (till)in the lake/terrestrial stage.
Depth of the upper regolithlayer in the lake basin.
Porosit of the lower regolithlayer (till).

m

Site SpecificTR-10-01
TR-10-02
TR-10-03
TR-10-05m

Site SpecificTR-10-02

ParametersSS.xls

m3/m3

Site SpecificParametersSS.xls

Average depth of glacial till insea basin
Depth of the upper regolithlayer in sea.
Density of the glacial clay interrestrial middle regolith layer.
Density of the postglacial clay
in terrestrial middle regolithlayer.
Density of the terrestrial upper
regolith layer (peat).
Growth of wetland relative
water area.
Porosity of the glacial clay interrestrial middle regolith layer.
Porosity of the post glacial
clay in terrestrial middle
regolith layer.
Porosity of the terrestrial
upper regolith layer (peat).
Depth of the post glacial clay
in terrestrial middle regolithlayer (covered by peat).
Depth of the terrestrial upper
regolith layer (peat).
Depth of the glacial clay of
the aquatic middle layer inthe sea basin.

m

Site SpecificTR-10-01
TR-10-02
TR-10-03
TR-10-05m

Site SpecificTR-10-03

ParametersSS.xls

kg DW/m3

Site SpecificTR-10-01

ParametersSS.xls

kg DW/m3

Site SpecificTR-10-01

ParametersSS.xls

kg DW/m3

Site SpecificTR-10-01

ParametersSS.xls

m2/ (m2year) Site Specific(Time Series)
Site Specificm3/m3

TR-10-05
TR-10-01

Parameters_TS_
all_basins.xls
ParametersSS.xls

m3/m3

Site SpecificTR-10-01

ParametersSS.xls

m3/m3

Site SpecificTR-10-01

ParametersSS.xlsm

Site Specific(Time Series)

TR-10-05

Parameters_TS_
all_basins.xlsmSite Specific(Time Series)
Site SpecificTR-10-05

Parameters_TS_
all_basins.xls
ParametersSS.xls

Biomass of macroflora andmacrofauna (macroalgae,
macrophytes, benthic macrofauna) in lake.
Biomass of pelagic biota (i.e.
phytoplankton bacterioplankton, zooplankton and fish) inlake.
Biomass of microphytobenthosand benthic bacteria in lake.
Carbon degassing rate.
Release of carbon from lakewater surface to atmosphere.
Net productivity of the benthic
macrocommunity, i.e. the net
primary production minus
respiration of macrofauna andflora, in lake.
Net productivity of the pelagic
community, i.e. net primary
production by phytoplankton
minus respiration by zooplankton, bacterioplankton,and fish, in lake.
Net productivity of the benthic
microscopic community, i.e. net
primary production by microphytobenthos minus respiration
by benthic bacteria in lake.

kg C/m2

Site Specific(Time Series)

TR-10-02
TR-10-03

ParametersTS.xls

kg C/m2

Site Specific(Time Series)

TR-10-02
TR-10-03

ParametersTS.xls

kg C/m2

Site Specific(Time Series)
Site Specific(Time Series)

TR-10-02
TR-10-03
TR-10-02
TR-10-03

ParametersTS.xls

year–1Site Specific(Time Series)

TR-10-02
TR-10-03

ParametersTS.xls

year–1Site Specific(Time Series)

TR-10-02
TR-10-03

ParametersTS.xls

year–1Site Specific(Time Series)

TR-10-02
TR-10-03

ParametersTS.xls

Lake_z_regoUp
poro_regoLow
Sea_z_regoLow
Sea_z_regoUp
Ter_dens_regoMid_gl
Ter_dens_regoMid_pg
Ter_dens_regoUp
Ter_growth_rego
Ter_poro_regoMid_gl
Ter_poro_regoMid_pg
Ter_poro_regoUp
Ter_z_regoMid_pg
Ter_z_regoUp
z_regoMid_gl_basin

Aquatic ecosystem
Aqu_biom_pp_macro

Aqu_biom_pp_plank

Aqu_biom_pp_ubent
Aqu_degass_C
Aqu_prod_pp_macro

Aqu_prod_pp_plank

Aqu_prod_pp_ubent

166

m

kg C/
(m2year)TR-10-05

ParametersSS.xls

ParametersSS.xls

ParametersTS.xls

TR-10-09

Parmeter Name

Description

Unit

Type

ReportSource FilegasUptake_C

Uptake of carbon fromatmosphere to lake water(mainly CO2).
Concentration of dissolved
inorganic carbon in lake water.
Concentration of particulatematter in lake water.
Production of edible crayfish
in the lake.
Production of edible fish in
the lake.
Minimum lake depth for
crayfish production.
Minimum lake depth for
production of edible fish.
Production of edible fish in
the sea.
Concentration of dissolved
inorganic carbon in sea water.
Concentration of particulatematter in sea water.

kg C/(m2year)Site Specific(Time Series)

TR-10-02
TR-10-03

ParametersTS.xls

kg C/m3

Site SpecificTR-10-02

ParametersSS.xls

kg DW/m3

Site SpecificTR-10-02

ParametersSS.xls

kg C/(m2year)kg C/(m2year)m

Site SpecificTR-10-02

Site SpecificTR-10-02

Site SpecificTR-10-02m

Site SpecificTR-10-02kg C/(m2year)kg C/m3

Site SpecificTR-10-03

Site SpecificTR-10-03

PostProcessing
ParametersSS.xls
PostProcessing
ParametersSS.xls
PostProcessing
ParametersSS.xls
PostProcessing
ParametersSS.xls
PostProcessing
ParametersSS.xls
ParametersSS.xls

kg DW/m3

Site SpecificTR-10-03

ParametersSS.xls

kg C/m3

Generic

TR-10-01

ParametersUC.xls–

Site SpecificTR-10-01

ParametersSS.xls–

Generic

TR-10-01

ParametersUC.xls

kg C/(m2year)kg C/(m2year)kg C/(m2year)kg C/m2

Site SpecificTR-10-01

Site SpecificTR-10-01

Site SpecificTR-10-01

Site SpecificTR-10-01

PostProcessing
ParametersSS.xls
PostProcessing
ParametersSS.xls
PostProcessing
ParametersSS.xls
ParametersSS.xls

kg C/m3

Site SpecificTR-10-01

ParametersSS.xls

kg DW/m3
1/yearkg C/ m2
year

Generic
Site SpecificSite SpecificTR-10-01
TR-10-01
TR-10-01

ParametersUC.xls
ParametersES.xls
ParametersSS.xls

kg C/(kg C
year)

Site SpecificTR-10-01

ParametersSS.xlsm

Site SpecificTR-10-01m

Generic

TR-10-01

PostProcessing
ParametersSS.xls
ParametersUC.xls

m/year

Site SpecificTR-10-01

kg DW/m3

Generic

TR-10-01

kg C/kg FW Generic

TR-10-07

ParametersUC.xls

kg C/kg FW Generic

TR-10-07

ParametersUC.xls

kg FW/lTR-10-07

ParametersUC.xls

Lake_conc_DIC
Lake_conc_PM
prod_edib_cray_Lake
prod_edib_fish_Lakez_min_prod_edib_crayfish_Lakez_min_prod_edib_fish_Lake
prod_edib_fish_Sea
Sea_conc_DIC
Sea_conc_PM
Terrestrial Ecosystem
conc_C_atmos
frac_C_atmos

frac_mush_Herbiv
prod_edib_berry
prod_edib_game
prod_edib_mush
Ter_biom_pp
Ter_conc_C_regoUp
Ter_conc_Dust
Ter_decomp
Ter_degass_C
Ter_prodBiom_pp
Ter_z_mixlay
Ter_z_roughness
vel_wind
Agri_conc_Dust
conc_C_meat
conc_C_milk
densMilk

TR-10-09

Concentration of carbon in
the atmosphere above theterrestrial ecosystem
Fraction of decomposed
carbon that is mineralised(leaving as CO2 to theatmosphere)
Fraction of mushrooms in thediet of terrestrial herbivores.
Production of edible berries.
Production of edible gamemeat.
Production of edible mushrooms.
Biomass of terrestrial primary
producers.
Concentration of dissolved
inorganic carbon in the upperterrestrial regolith (peat).
Concentration of dust in air.
Decomposition rate.
Degassing rate of dissolved
inorganic carbon in the terrestrial ecosystem.
Net primary production perunit biomass in the terrestrial
ecosystem.
Height of the mixing layer inthe terrestrial ecosystem.
Height above ground below
which the wind speed is zerodue to vegetation.
Wind velocity.
Concentration of dust in theatmosphere on agriculturalland.
Concentration of carbon inmeat.
Concentration of carbon in
milk.
Density of the milk.

Generic

PostProcessing
ParametersSS.xls
PostProcessing
ParametersSS.xls

167

Parmeter Name

Description

Unit

Type

ReportSource File

ingRate_food_meat

Fodder ingestion rate for meat
cattle.
Fodder ingestion rate for milk
producing cattle.
Soil ingestion rate for cattle.
Water ingestion rate for meat
cattle.
Water ingestion rate for milk
producing cattle.
Ratio of total upper leaf
surface of vegetation divided
by the surface area of the landon which the vegetation grows.
Storage capacity of interceptedwater on leaf surface.
Number of irrigation events.
Production of edible cereals.

kg C/dGeneric

TR-10-07

ParametersUC.xls

kg C/dGeneric

TR-10-07

ParametersUC.xls

kg DW/dm3/dGeneric
Generic

TR-10-07
TR-10-07

ParametersUC.xls
ParametersUC.xls

m3/d

Generic

TR-10-07

ParametersUC.xls

m2/ m2

Generic

TR-10-01

ParametersUC.xls

m3/ m2

Generic

TR-10-01

ParametersUC.xls

year–1kg C/(m2year)kg C/kg C

Generic
Site SpecificTR-10-01
TR-10-01

Site SpecificTR-10-01

kg C/kg C

Site SpecificTR-10-01

kg C/(m2year)kg C/(m2year)kg C/(m2year)m/year

Site SpecificTR-10-01

Site SpecificTR-10-01

Site SpecificTR-10-01

Generic

TR-10-01

ParametersUC.xls
PostProcessing
ParametersSS.xls
PostProcessing
ParametersSS.xls
PostProcessing
ParametersSS.xls
PostProcessing
ParametersSS.xls
PostProcessing
ParametersSS.xls
PostProcessing
ParametersSS.xls
ParametersUC.xls

Gross lateral flux of water fromlake/stream to wetland, normalised by the net lateral flux
from wetland to lake/stream.
Total advective flux fromregoLow (till) to regoMid (glacial and post glacial deposits)
for the lake/terrestrial stage.
Advective flux in the aquaticobject between the sedimentand the water during lakestage, normalised by the net
lateral advective flux fromwetland to lake/stream.
Fraction of the upward flux
from regoLow (till) that is
directed to the terrestrial partof the biosphere object.
Total annual runoff.

unitless or(m3/year)/(m3/year)

Site SpecificTR-10-01
TR-10-02

ParametersSS.xls

m/year

Site SpecificTR-10-01
TR-10-02

ParametersSS.xls–

Site SpecificTR-10-02

ParametersSS.xls–

Site SpecificTR-10-01
TR-10-02

ParametersSS.xls

m/year

Site SpecificParametersSS.xls

Total advective flux fromregoLow (till) to regoMid (glacial and post glacial deposits)
for the sea stage.
The advective flux from regoMid (glacial and post glacial
deposits) to regoUp (peat)in the terrestrial ecosystem.
normalised by the net lateral
flux from terrestrial ecosystem
to lake/stream.
Average water retention timein the sea basin.
The water volume capacity ofa well.

m/year

Site SpecificTR-10-01
TR-10-02
TR-10-03
TR-10-03–

Site SpecificTR-10-01
TR-10-02

ParametersSS.xls

year

Site Specific(Time Series)
Site SpecificTR-10-03

Water_retention.
xls
PostProcessing
ParametersSS.xls

ingRate_food_milk
ingRate_soil_Cow
ingRate_water_meat
ingRate_water_milk
leaf_areaIndex

leaf_StoreCapac
numb_irrig
prod_edib_cereal
prod_edib_meat
prod_edib_milk
prod_edib_tuber
prod_edib_vegetab
prod_fodder
vol_irrig
Surface Hydrology andwater exchange
Flooding_coef

Lake_adv_low_mid

Lake_Aqu_adv_mid_
up_norm

Lake_fract_MirerunoffSea_adv_low_mid

Ter_adv_mid_up_norm

wat_retwellCapac

168

Production of edible meat(relative fodder consumption).
Production of edible milk(relative fodder consumption).
Production of edible root crop,
e.g. potato.
Production of edible vegetables.
Production of fodder on
agricultural land.
Volume of irrigation waterused each year.

m3/yearTR-10-01

ParametersSS.xls

TR-10-09

Parmeter NameDistribution coefficientsand diffusivity
kD_regoLow
Lake_kD_PM
Lake_kD_regoMid
Lake_kD_regoUp
Sea_kD_PM
Sea_kD_regoMid

Sea_kD_regoUp
Ter_kD_regoMid

Ter_kD_regoUp
diffcoef
Concentration ratios,
retention and releasecR_foodToHerbiv
cR_soilToCerealcR_soilToMush
cR_soilToTubercR_soilToVegetab
cR_watToCray_LakecR_watToFish_LakecR_watToFish_Sea
Lake_cR_pp_macro
Lake_cR_pp_plank
Lake_cR_pp_ubent
Sea_cR_pp_macro
Sea_cR_pp_plank
Sea_cR_pp_ubent
tC_cowMeat

TR-10-09

Description

Unit

Type

ReportSource File

Distribution coefficient forlower regolith layer (till).
Distribution coefficient forparticulate matter in lake/
stream.
Distribution coefficient forparticulate matter in lake/
stream.
Distribution coefficient for the
middle regolith layer in lake/
stream.
Distribution coefficient forparticulate matter in sea.
Distribution coefficient for the
middle regolith layer in sea(glacial clay and post glacial
sediments combined).
Distribution coefficient for theupper regolith layer in sea.
Distribution coefficient for theterrestrial middle regolith layer(glacial clay and post glacial
sediments combined).
Distribution coefficient for theterrestrial upper regolith layer(peat).
Diffusion coefficient.

m3/kg DW

Element
Specific
Element
Specific

TR-10-07

ParametersES.xls

TR-10-07

ParametersSS.xls

m3/kg DW

Element
Specific

TR-10-07

ParametersES.xls

m3/kg DW

Element
Specific

TR-10-07

ParametersES.xls

m3/kg DW

Element
Specific
Element
Specific

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

Element
Specific
Element
Specific

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

m3/kg DW

Element
Specific

TR-10-07

ParametersES.xls

m2/yearElement
Specific

TR-10-02

ParametersES.xls

kg C/kg C

Element
Specific
Element
Specific
Element
Specific
Element
Specific
Element
Specific
Element
Specific
Element
Specific
Element
Specific
Element
Specific

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

m3/kg C

Element
Specific

TR-10-07

ParametersES.xls

m3/kg C

Element
Specific

TR-10-07

ParametersES.xls

m3/kg C

Element
Specific

TR-10-07

ParametersES.xls

m3/kg C

Element
Specific
Element
Specific
Element
Specific

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

Concentration ratio from foodto terrestrial herbivores.
Concentration ratio from soil
to cereals.
Concentration ratio from soil
to mushrooms.
Concentration ratio from soil
to tubers.
Concentration ratio from soil
to vegetables.
Concentration ratio from waterto crustacean in the lake.
Concentration ratio from waterto fish in the lake.
Concentration ratio from waterto fish in the sea.
Concentration ratio from water
to macrophytes/macroalgae inlake/stream.
Concentration ratio from water
to macrophytes/macroalgae inlake/stream.
Concentration ratio from waterto phytoplankton in lake/
stream.
Concentration ratio from water
to macrophytes/macroalgae
in sea.
Concentration ratio from waterto phytoplankton in sea.
Concentration ratio from water
to microphytobenthos in sea.
Transfer coefficient fromintake of radionuclides in fodder and water to cow meat.

m3/kg DW

m3/kg DW

m3/kg DW
m3/kg DW

kg DW/kg C
kg DW/kg C
kg DW/kg C
kg DW/kg C
m3/kg C
m3/kg C
m3/kg C
m3/kg C

m3/kg Cd/kg FW

169

Parmeter Name

Description

Unit

Type

ReportSource FiletC_cowMilk

Transfer coefficient fromintake of radionuclides in fodder and water to cow milk.
Concentration ratio for terrestrial primary producers.
Fraction of leaf interceptedradionuclides that is adsorbed
to edible parts of vegetables
during irrigation.
Discrimination factor duringdecomposition.

d/lElement
Specific

TR-10-07

ParametersES.xls

kg DW/kg C Element
Specific–
Element
Specific

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls–

Element
Specific

TR-10-07

ParametersES.xls

The time interval over which
concentration in agriculturalsoil is averaged over.
Time spent outdoor (timefor exposure from externalradiation).
Human food ingestion rate.
Human water ingestion rate.
Human inhalation rate ofvolume air.

yGeneric

TR-10-07

ParametersUC.xls

h/year

Generic

TR-10-07

ParametersUC.xls

kg C/year
m3/yearm3/h

Generic
Generic
Generic

TR-10-07
TR-10-07
TR-10-07

ParametersUC.xls
ParametersUC.xls
ParametersUC.xls

Sv/h*Bq/m3

Element
Specific
Element
Specific
Element
Specific
Element
Specific

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

TR-10-07

ParametersES.xls

Ter_cR_pp
coefRetent

Ter_df_decomp
Human characteristics
AverTime
expTimeingRate_C
ingRate_wat
inhalRate
Dose coefficients
dosCoef_ext
dosCoef_ing_food
dosCoef_ing_water
dosCoef_inhal

170

Dose coefficient from external
exposure.
Dose coefficient from ingestion of food.
Dose coefficient from ingestion of water.
Dose coefficient from inhalation.

Sv/Bq
Sv/Bq
Sv/Bq

TR-10-09