SKB s safety assessment on low and intermediate waste. Eva Andersson

Transcription

1 SKB s safety assessment on low and intermediate waste Eva Andersson

2 SFR an existing repository for low and intermediate waste This presentation 1. Our repository for low and intermediate waste 2. Demand on the safety assessment 3. Main working tasks in the safety assessment

3 Overview of the Swedish system

4

5 Construction of SFR ( )

6 SFR - The surface facility

7 The underground facility Total storage capacity is 63,000 m 3 (~400,000 excavated volume m 3 ). Total allowed acitivity Bq The silo is intended to host 80% of the activity in SFR (~20% in BMA).

8 Containers- steel or concrete Top of silo BLA BMA

9 Why a safety assessment now? SSM commented on the last safety assessment SAR-08 and demands an updated safety assessment 2013 SKB wants to extend SFR to be able to store more waste Prolonged life time of nuclear plants - more operational waste than initially planned Decommissioning waste will be stored at SFR

10 Existing SFR and the planned extension in blue

11 Demands on the safety assessment for SFR A safety assessment is conducted in order to show that the facility is safe. Which means that the annual radiological risk is less than 10-6 (which, according to ICRP publication #60 corresponds to an annual dose of 14 µsv) The analysis should cover a time of years

12 Biosphere part of the safety assessment Dose to humans and non-human biota, i.e. transport and accumulation of radionuclides in the biosphere has to be calculated Use the radionuclide model from the safety analysis for spent nuclear fuel (SR-Site) as a basis for calculations Site - Forsmark, the same as previous safety analyses

13 Are we done copy the preceding safety assessments for SFR SSM -comments on the last SAR-08 Identified possible areas for improvements of the SR-Site Radionuclide transport model and the Landscape model Adjust the Radionuclide transport model to better represent C-14 transport and accumulation in the biosphere in order to avoid unnecessary conservatisms

14 Annual dose (μsv) Permafrost Mire/forest Permafrost Coast Permafrost Coast Results from previous safety assessment for SFR, SAR Coast Lake Mire/forest ,1 0,01 0, Time (year) C-14-in C-14-org Cl-36 Ni-59 Se-79 Mo-93 Nb-94 Tc-99 Ag-108m I-129 Cs-135 Pu-239 Pu-240 Sum 14μSv

15 Landscape model Forsmark landscape change with time

16 Forsmark in 5000 years

17 Forsmark with a higher sealevel

18 Landscape model Biosphere objects Object in the landscape where release from the repository can affect humans and the environment Lake Sea Sea Bay Lake Mire Forest SSM Comment on SAR-08: to consider smaller biosphere objects than the main object, large lake object 116 Uncertainties in the model used in previous analyses, especially regarding the threshold of future Lake 116

19 Landscape model- result 1. New site data were used to make a new DEM for present Forsmark 2. New regolith depth model for present Forsmark 3. New landscape model of future Forsmark. Different timing for different climate cases

20 Radionuclide model development New atmosphere model Transition between ecosystems Chemical forms of carbon, behaviour of e.g. methane Update Kd/CR Model resolution

21 Post-processing - Human utilization of the biosphere objects and dose calculations Doses in our previous assessments has been shown to be dominated by intake of food and water. SR-Site approach Production based intake from the biosphere objects. The area and type of ecosystem in the landscape determines the amount of production in the biosphere object. Most exposed individuals are assumed to feed in proportion to of produced food in the biosphere object. Number of people living in the biosphere objects are determined after the size and productivity of the biosphere

22 SFR Still production based biosphere objects but also Physiological and nutritional needs are met Diets are historical relevant or observed in existing human cultures Minimum number of persons utilizing the biosphere objects are introduced based on type of community

23 Summary SKBs safety assessment for low and intermediate level waste SFR is an already existing repository but SKB are planning to expand the repository C-14 is the main dose contributing Radionuclide A new safety assessment should be done by the end of 2013 Main issues are C-14 behavior in the biosphere and chemical forms of carbon, new atmosphere model, accumulation in soils and sediments, transformation between ecosystems Kd/CR for top ten Radionuclides (C-14, Cl-36, Mo-93, Cs-135, Ni-59, Se-79, Nb-94, Tc-99, Ag-108m, I-129) Human behavior and land use, what limitations should be put on behavior and diets?

24 The biosphere team working with SFR