Radiological Consequences Analysis for a HLW Repository in Bedded Salt in Germany (Project KOSINA)

1. Radiological Consequences Analysis for a
HLW Repository in Bedded Salt in Germany
(Project KOSINA)
Jonathan Kindlein
GRS gGmbH
Middelburg, The Netherlands
September 5-7, 2017

2. Introduction – Project Tasks
WP3: Development of a safety concept and safety demonstration concept
 Development of a safety concept for a repository for heat-generating
radioactive waste and spent fuel in bedded rock salt formations
 Development of a safety demonstration concept based on the safety
concept
 Dealing with uncertainties
WP6: Analysis of radiological consequences
 Derivation of test cases for radiological consequences analysis,
verification of the applicability of existing radiological indicators (RGI,
etc.)
 Verification of the applicability of existing instruments for radiological
consequences analysis on the basis of the specified test cases and
indicators
2

3. Safety Demonstration – Model
 GRS-own software package RepoTREND (Transport and REtention of Non-
decaying and Decaying contaminants in final Repositories)
“Simplified” radiological long-term statement
Output: Radiological safety indicator
RGI (dimensionless, 0 < RGI < 1)
3
CRZ
CRZ = Containment providing rock zone

4. Repository Layout – Drift Disposal
 Mine layout for drift disposal concept  aggregation of areas
(reference to DBE TEC/Bollingerfehr pres. this afternoon)
Pollux-10
Pollux-10 Pollux-10 Pollux-9,
CSD-B/C,
Castor
infrastructural area
hulls and
structural elements
CSD-V
shafts
(sealed)
parallel drifts
(backfill, dry)
access drifts
(backfill, wetted)
cross drifts
(backfill, dry)
emplacement drifts
(waste, backfill)
infrastructure
(backfill, gravel)
4

5. Model Structure and major FEP’s
 LOPOS segmented model structure for drift disposal repository concept
(28 segments, derived and aggregated from mine layout)
 Simulation period
 Consideration of operational phase: 2050-2080, sequential emplacement
 Demonstration period of one million years, simulation period of 10 million years
 Considered processes
 Brine in-/outflow, heat, convergence, salt backfill compaction, seal failure
 Nuclide mobilization, decay, solubility, retention, advection, diffusion, incorporation
 Assessment criteria: Effective radiation dose (RGI)
5
RK-1
ES-
Q1b
S-V
(vertical)
Q1
RU-V2
RU-1
INFRA-B
RK-2
ES-
Q2
Q2
RU-2
ES-
Q1a
RK-3
ES-
Q3b
Q3
RU-3
ES-
Q3a
ES-
Q4
Q4
RU-V1
RK-V1
RK-0
RU-0
RK-V2
RU-4
RK-4
INFRA-RK
INFRA-RU

6. Case Studies - Overview
 Preliminary test case „shaft sealing lengths“
 Preliminary test case „access drift lengths“
 Consequence analysis: Base Case Scenario
 Case study: Reduced Diffusion
 Case study: Reduced Convergence
6

7. Case Study – Shaft Sealing
 Preliminary test case „shaft sealing lengths“
 Bedded z2 formation only  100 m
 Entire bedded salt formation  250 m
 Domal salt formation  500 m (for comparison)
 Preliminary test case „access drift lengths“
 Consequence analysis: Base Case Scenario
 Case study: Reduced Diffusion
 Case study: Reduced Convergence
7

8. Results – Shaft Sealing Lengths
 Brine Inflow Infrastructure Area
8
time [a]
volume[m³]
10
0
10
1
10
2
10
3
10
4
10
5
10
6
10
2
10
3
10
4
10
5
10
6
total volume
pore space
brine volume (shaft 500 m)
brine volume (shaft 250 m)
brine volume (shaft 100 m)
test case "shaft sealing"
30 Aug 2017
W:projektekosinadetabbvolumen_infra-b-v1_id_schacht_en.lay

9. Results – Shaft Sealing Lengths
 Radiological Consequences (RGI)
9
Zeit [a]
RGI[-]
10
3
10
4
10
5
10
6
10
7
10
-9
10
-8
10
-7
10
-6
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
100 m
250 m
500 m
test case "shaft sealing lengths"
W:projektekosinadetabbdosis-fl-sl_det-v1_id_schacht_en.lay
time [a]
RGI=1
t=1Mio.a

10. Case Study – Access Drift
 Preliminary test case „shaft sealing lengths“
 Preliminary test case „access drift lengths“
 Minimum safety distance of emplacement areas  300 m
 Sufficient space for geotechnical and long term sealings  500 m
 Further extension of long term sealings  1000 m
 Consequence analysis: Base Case Scenario
 Case study: Reduced Diffusion
 Case study: Reduced Convergence
10

11. Results – Access Drift Lengths
 Radiological Consequences (RGI)
11
Zeit [a]
RGI[-]
10
3
10
4
10
5
10
6
10
7
10
-6
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
300 m
500 m
1000 m
test case "access drift lenghts"
W:projektekosinadetabbdosis-fl-sl_det-v1_id_rs_en.lay
time [a]

12. Case Study – Base Case
 Preliminary test case „shaft sealing lengths“
 Preliminary test case „access drift lengths“
 Consequence analysis: Base Case Scenario
 100 m shaft sealing length (250 m effective diffusion length)
 500 m access drift lengths
 Failure of geotechnical sealings after 50,000 years (10-17 m²  10-15 m²)
 continuous brine intrusion
 Local void convergence depending on temperature and moisture
 Case study: Reduced Diffusion
 Case study: Reduced Convergence
12

13. Results – Base Case
 Brine level in mine
13
time [a]
brinelevel[m]
10
1
10
2
10
3
10
4
10
5
10
6
0
1
2
3
4
Infra-B
access drift
parallel drift 1
parallel drift 2
parallel drift 3
cross drift 1
cross drift 2
cross drift 3
cross drift 4
basis case
W:projektekosinadetabbpegelhöhe_det-v1_id_ref_en.lay

14. Results – Base Case
 Radiological Consequences (RGI)
14
time [a]
RGI[-]
10
3
10
4
10
5
10
6
10
7
10
-9
10
-8
10
-7
10
-6
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
total
fission products
I 129
Sn 126
Se 79
actinides
Th 230
Ra 226
Pb 210
Basis Case
W:projektekosinadetabbdosis-fl-sl_det-v1_id_ref_en.lay

15. Case Study – Diffusion
 Preliminary test case „shaft sealing lengths“
 Preliminary test case „access drift lengths“
 Consequence analysis: Base Case Scenario
 Case study: Reduced Diffusion
 Reference value: average diffusion coefficient in water
(overestimating)
 Neglecting: accessible pore space, nuclear/molecular size
 Reduction by one magnitude: 1.5·10-9 m²/s  1.5·10-10 m²/s
 Case study: Reduced Convergence
15

16. Results – Reduced Diffusion
 Radiological Consequences (RGI) compared to Base case
16
time [a]
RGI[-]
10
3
10
4
10
5
10
6
10
7
10
-9
10
-8
10
-7
10
-6
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
total
fission products
actinides
solid: basis case
dashed: little diffusion
W:projektekosinadetabbdosis-fl-sl_det-v1_id_vgl_diff_en.lay

17. Case Study – Convergence
 Preliminary test case „shaft sealing lengths“
 Preliminary test case „access drift lengths“
 Consequence analysis: Base Case Scenario
 Case study: Reduced Diffusion
 Case study: Reduced Convergence
 Slower salt rock creep properties, low end of margin
 convergence approx. 10 times slower
17

18. Results – Reduced Convergence
 Porosity evolution of backfilled drifts
18
time [a]
porosity[-]
10
0
10
1
10
2
10
3
10
4
10
5
0
0.1
0.2
0.3
0.4
a.d. (wetted)
c.d. 1 (dry)
c.d. 2
c.d. 3
c.d. 4
W:projektekosinadetabbporo-fl-sl_det-v1_id_vgl_konv_en.lay
solid: basis case
dashed: slow convergence

19. Results – Reduced Convergence
 Radiological Consequences (RGI) compared to Base case
19
time [a]
RGI[-]
10
3
10
4
10
5
10
6
10
7
10
-9
10
-8
10
-7
10
-6
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
total
fission products
actinides
solid: basis case
dashed: slow convergence
W:projektekosinadetabbdosis-fl-sl_det-v1_id_vgl_konv_en.lay

20. Interpretation and Conclusion
 Results
 Geotechnical barriers along with long-term drift sealings of compacting
salt backfill reduce radiological consequences to negligible values
 RN release from repository is mainly controlled by diffusion
 RN releases from CRZ only occur at very late times
 Reduced convergence rates may increase/add advective portion
 Conclusions
 Optimization of repository layout and design based on numerical
consequences analysis is possible and necessary
 Computational case studies are useful and necessary for process
analysis as well as further identification of sensitive parameters
 Outlook
 Different disposal concepts; Probabilistic Analysis; Report
20

21. Thanks and Acknowledgements
Thanks to GRS colleagues D. Buhmann, J. Mönig, J. Wolf.
Thanks to project partners .
Thanks to BMWi for funding, PTKA-WTE for administrating.
Thank you for your attention!
21
FKZ 02E11405B
project management

22. Backup Slides
22

23. KOSINA Safety Concept
Guiding principles of the safety concept for HLW repositories in bedded salt formations:
 The radioactive waste must be contained as far as possible in a well-defined area of the
host rock around the waste (containment providing rock zone – CRZ)
 The containment shall be effective immediately post-closure and it must be provided by
the repository system permanently and maintenance-free
 The immediate and permanent containment shall be accomplished by preventing or at
least limiting intrusion of brine into the disposal area
post closure time / years0 106
geological barrier
shaft seals and drift seals
compacting crushed salt backfill
spent fuel canisters
waste matrix
23

24. Containment Providing Rock Zone
„simplified“ radiological long-term statement
( safety demonstration concept)
HR
OV
CRZ
REP
HR
OV
REP
CRZ
Overburden
Host Rock
Containment providing
rock zone
Seal of CRZ
Disposal Area
Rock body with safety-
relevant
barrier function
Rock body without
safety-relevant
barrier function
24

25. Demonstration of Long-Term Safety
 Proof of radiological negligibility of radionuclide releases from the CRZ
 Indicator: index of marginal radiological impact (RGI, dimensionless number)
 Staged approach for long-term safety assessment
25
𝑅𝐺𝐼 =
10 ∙ 𝑖 𝑆𝑖 ∙ 𝐷𝐾𝐹𝑖
𝑊
𝐾 𝑅𝐺𝐼

26. Diffusion Coefficients from Literature
26

27. Case Study – Discretization
 Preliminary test case „shaft sealing lengths“
 Preliminary test case „access drift lengths“
 Consequence analysis: Base Case Scenario
 Case study: Reduced Diffusion
 Case study: Reduced Convergence
 Case study: Discretization
 Base case: internal discretization of model segments (~20m block
lengths)
 coarse discretization of model segments (no internal blocks)
 refined discretization of model segments (~5m block lengths)
27

28. Results – Different Discretization
 Radiological Consequences (RGI) compared to Base case
28
time [a]
RGI[-]
10
3
10
4
10
5
10
6
10
7
10
-9
10
-8
10
-7
10
-6
10
-5
10
-4
10
-3
10
-2
10
-1
10
0
total
fission products
actinides
basis case: internal discretization ~20 m
dashed: no internal discretization
dotted: fine internal discretization (5 m)
W:projektekosinadetabbdosis-fl-sl_det-v1_id_vgl_disk_en.lay