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![Page 1: The need for process understanding in the derivation of a credible dose model for geological repositories Shulan Xu 2010-01-26.](https://reader036.fdocuments.in/reader036/viewer/2022062309/56649db25503460f94aa18de/html5/thumbnails/1.jpg)
The need for process understanding in the derivation of a credible dose model
for geological repositories
Shulan Xu
2010-01-26
![Page 2: The need for process understanding in the derivation of a credible dose model for geological repositories Shulan Xu 2010-01-26.](https://reader036.fdocuments.in/reader036/viewer/2022062309/56649db25503460f94aa18de/html5/thumbnails/2.jpg)
Contents
Introduction
Critical issues
Modelling exercises
Considerations
![Page 3: The need for process understanding in the derivation of a credible dose model for geological repositories Shulan Xu 2010-01-26.](https://reader036.fdocuments.in/reader036/viewer/2022062309/56649db25503460f94aa18de/html5/thumbnails/3.jpg)
Introduction Historical development of biosphere models
For thirty years or more, dose models have employed a compartmental representation of the surface hydrogeology to model the dynamic concentration of contaminants in various ecosystems– BIOMOVS I & II, BIOMASS-6
Landscape models in SR-Can (SKB, 2006) – A number of ecosystems connected – Evolution of site
Dose assessment in the overall assessment – Dose factor, DF, (Sv/yr per Bq/yr) – Defensible, transparent
– ACM, – possible impacts
Microsoft PowerPoint-presentation
![Page 4: The need for process understanding in the derivation of a credible dose model for geological repositories Shulan Xu 2010-01-26.](https://reader036.fdocuments.in/reader036/viewer/2022062309/56649db25503460f94aa18de/html5/thumbnails/4.jpg)
Developments in safety assessment
SSM has initiated research and development projects in the area of performance assessment (PA) modelling a few years ago.– Processes understanding of transport and distribution of
radionuclides– Independent modeling capacity to perform replication
calculations and development of alternative models/tools to give critical analysis for the safety assessment.
Performance of reviews– SR-97, SR-Can– SAFE, SAR-08
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Characteristics of discharge areas
Lake, stream or wetlands
Thick soil layer (QD)
Coincidence with fracture zone
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How a size of biosphere object can be identified?
Path 1
Path 2
Contaminated area
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Critical issues
Representation of discharge areas
Process descriptions– Accumulation/GBI– subsurface chemical zonation
Model discretisation
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Research and modelling work in 2009
Project on radionuclide transport through the ”GBI”
Modelling exercises– Effect of accumulation– Effect of different combinations of discharge points
Microsoft PowerPoint-presentation
![Page 9: The need for process understanding in the derivation of a credible dose model for geological repositories Shulan Xu 2010-01-26.](https://reader036.fdocuments.in/reader036/viewer/2022062309/56649db25503460f94aa18de/html5/thumbnails/9.jpg)
Modelling exercises in 2009
Assume discharge point moving with time due to uplift
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Modelling exercises in 2009
0 – 3000 years
3000 – 20000 years
1 Bq/y
1 Bq/y
river
river
lake
lake
wetland
wetlandAgr. land
a)
b)
QD
QD
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Modelling exercises in 2009
0 0.2 0.4 0.6 0.8 1 1.2 1.4 1.6 1.8 2
x 104
0
100
200
300
400
500
600
700
800
Time (years)
Inve
ntor
y
(Bq)
Ra-226
C-14Cl-36
Cs-135
I-129
Ni-59Pb-210
Po-210
Simulated inventory of top soil vs time
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Estimates of dose rates for agricultural land compared with doses for
different ecosystems.
Nuclides Agricultural
Land/River
Agricultural
Land/Lake
Agricultural
Land/Mire
226Ra 0.7 3 33
36Cl 16 58 10
135Cs 0.4 2.5 17
129I 15 90 21
59Ni 20 140 17
Modelling exercises in 2009
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Findings from modelling exercises
It is not always that the discharge point/object has highest dose effects
A clear link between FEP matrix and PA models is necessary
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Considerations
Do we know enough about dilution to make credible dose calculations?
Consensus