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1BMA1BLA2BTF1BTFSilo
1BRT2BLA3BLA
4BLA5BLA2BMA
Methodology and results for the safety assessment for the low- and intermediate level waste repository (SFR) in Sweden
Klas Källström, Eva AnderssonSwedish Nuclear Fuel and Waste Management Co.
A schematic picture of the repository showing the existing part (in grey) and the planned extension (blue). The repository is situated approximately between 60 and 120 meters below the sea floor.The different rock caverns have different technical barriers, e.g. the silo were most of the radioactivity is placed has both bentonite and concrete barriers.
• The safety assessment follow a ten step methodology.• The FEP identification and initial state description sets
the framework for the following steps in the assessment.• The purpose of the reference evolution is to provide an
overall understanding of the repository evolution, inclu-ding important uncertainties for the post-closure safety.
• Safety functions defines important safety related aspects of the repository and its environs.
• With the aid of the safety functions and the description of the reference evolution, a number of scenarios and calculation cases are chosen to cover possible future evolutions of the repository system.
• A main scenario and a number of less probable scenarios are analysed to examine whether the total risk from all scenarios is below 10−6.
The assessment period is 100,000 years under which the barriers degrade but also, the radionuclides decay to insignificant levels.
Radionuclides with short half-life, which makes up the major part of the initial radiotoxicity, do not contribute significantly to the total risk. Instead long-lived radionuclides C-14, Mo-93 and Ni-59 contributes most to the risk. During the entire assessment period the risk is below the regulatory risk limit of 10-6, which corresponds to 1 % of the background radiation at the site.
Acknowledgements: A large number of persons, too many to be mentioned here, are acknowledged for contributing to the safety assessment.
10-10
10-9
10-8
10-7
10-6
10-5
2,000 10,000 100,000
Ann
ual r
isk
Time (years AD)
Total (SFR)Mo-93C-14-orgNi-59U-238Ca-41I-129Pu-240Pu-239Am-241Ac-227Pa-231Cs-135U-235Cl-36Ra-226Others
0.01
0.1
1
10
100
1 10 100 1,000 10,000 100,000
Rel
ativ
e ac
tivity
(%)
Time (years)
TotalNi-63Cs-137Nb-93mAm-241Co-60Ni-59C-14-inorgSr-90H-3C-14-orgSm-151Pu-241Ag-108mNb-94Eu-152
1 Handling of FEPs (features, events and processes)- Initial state- Internal processes- External conditions
2a Site description- Site investigations- Site modelling
2b Initial state ofexisting facility- Reference design (System descriptions and drawings)- Current status
2c Initial state ofextended facility- Reference design- Execution plans
2d Initial state ofwaste- Existing waste- Future waste- Acceptance criteria
3 Description of external conditions- Climate and climate-related issues- Large-scale geological processes and effects- Future human actions
4 Description of internal processes- Waste- Barriers- Geosphere- Biosphere
5 Definition of safety functions- Safety functions of the repository system- Measurable or calculable safety function indicators
6 Compilation of input data- Qualification and quality assurance of data- Assessment activities and used data
10 Conclusions- Summary safety evaluation- Future research needs- Requirements on operation and facility design
7 Analysis of reference evolution.Repository system evolution during- First 1,000 years after closure- Temperate climate conditions- Periglacial climate conditions
8 Selection of scenarios- Main scenario- Less probable scenarios- Residual scenarios
9 Analysis of selected scenarios- Selection and description of calculation cases- Radionuclide transport and dose calculations- Evaluation against the risk criterion
Concrete in BMA consideredto be flow limiting
First potentialfreezing of concrete
Institutional controlis feasible
Shorelinepasses repository
Time (years)
10t1/2Co-60
10t1/2Cs-137
10t1/2Ni-63
10t1/2Am-241
10t1/2Mo-93
10t1/2C-14
10t1/2”short lived”
2% of initialradiotoxicity
10 10,0001,000100 100,000
