SALT Workshop

1. Safety Case: German Approach
- from ISIBEL to KOSINA
Jens Wolf
GRS gGmbH
7th US/German Workshop on Salt
Repository Research, Design, and
Operation
Washington, DC, September 7-9, 2016

2. Safety Case
The safety case is the collection of scientific, technical,
administrative and managerial arguments and evidence in
support of the safety of a disposal facility, covering the
suitability of the site and the design, construction and operation
of the facility, the assessment of radiation risks and assurance of
the adequacy and quality of all of the safety related work
associated with the disposal facility.
(…)
The safety case and supporting safety assessment provide the
basis for demonstration of safety and for licensing. They will
evolve with the development of the disposal facility, and will
assist and guide decisions on siting, design and operations.
2
Source: IAEA SSG-23

3. 3
Source: NEA No. 3679, 2004 Source: NEA No. 78121, 2013
Safety Case: Nature and Purpose

4. Elements of the Safety Case
4
Safety Case Context Safety Strategy
System description
Safety assessment
Limits, controls and conditions
Integration of safety arguments
Iterationanddesignoptimization
Managementofuncertainty
Source: IAEA SSG-23

5. Safety Case
German Safety Case Approach has been developed in R&D
projects dealing with the following questions:
 How to achieve safety?
 Safety strategy (OS/PCS)
 How to demonstrate safety?
 Safety assessment
 How to manage uncertainties?
 Management of uncertainties
 How to communicate safety?
 Integration of safety arguments
5
Preliminary Safety Case Comprehensive Safety Case
Safety Case R&D

6. Elements of Safety Case R&D
R&D in Germany
6
Safety Case Context Safety Strategy
System description
Safety assessment
Limits, controls and conditions
Integration of safety arguments
Iterationanddesignoptimization
Managementofuncertainty
Source: IAEA SSG-23

7. Safety Case: R&D in Germany
7
ISIBEL
ISIBEL-II
VSG
AnSichT
KOSINA
clay
CHRISTA
salt crystalline
BASEL
bedded
domal
t
2016
X R&D BMWi
+ support international cooperation (NEA/IAEA)

8. Safety Strategy
8
How to achieve safety?
Regulations / Geology / Repository Concept
Protection Goals
Safety Principles / Safety Functions
Guiding Principles
Design Requirements
(…)
Objectives  Measures
How to demonstrate safety?
Safety Case Context Safety Strategy
System description
Safety assessment
Limits, controls and conditions
Integration of safety arguments
Iterationanddesignoptimization
Managementofuncertainty

9. Requirement A:
The stored waste packages ought to be quickly and as close as possible enclosed
by rock salt in conjunction with the geotechnical barriers (containment).
Requirement B:
The containment providing rock zone remains intact (geological and geotechnical
barriers) and is not altered by internal or external events and processes (integrity
/ freedom from maintenance)
Requirement C:
A recriticality must be excluded at every stage of the repository evolution
(criticality exclusion)
 Specific objectives (14 principal goals)
 Strategic measures (17 design specifications and technical measures)
9Project Meeting KOSINA; Hannover 16.03.2016
Safety concept:
Domal salt (VSG)

10. Safety concept
10

11. Safety concept:
Containment-providing rock zone
11
REP
CRZ
HR
OV
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
Seals
Geological barrier
106 a
Crushed salt backfill
Requirement A,C
Requirement B

12. Management of Uncertainties
12
• Scenario uncertainties
Scenario analysis (FEP, scenario development)
• Data and parameter uncertainties
Uncertainty and sensitivity analysis
• Model uncertainties
Benchmarking, uncertainty and sensitivity analysis

13. Demonstration concept
13
Containment:
- CRZ: dimension
- CRZ: preservation
- Integrity of barriersHuman
intrusion
Proof of
sub-
criticality
Non-radio-
logical
protection
goals
Opera-
tional
safety
Handling of
uncertainties:
- data
- model
- scenario
Safety demonstration concept
Radiological safety indicator
Assessment
Evolution(s)
of repository
system

14. Radiological Indicator
14
RGI > 1
Assessment of safe containment
RGI = 0
No contact
between
solution and
waste
No release of
RN into the
gas phase
No release
of RN
out of CRZ
0 < RGI ≤ 1
Difussive
transport of
RN
Advective
transport of
RN
Repository
system in this
form (layout)
not suitable
Complete containment
Assessment by simplified statement
Criteria
according to
Safety
Requirements
fulfilled
RGI > 1
Criteria
according to
Safety
Requirements
not fulfilled
Stage 2
Stage 3
Stage 1
Stage 4
REP
CRZ
HR
OV

15. Radiological consequences
15
Zeit [a]
RGI[-]
103
104
105
106
107
10-6
10-5
10-4
10-3
10-2
10-1
10
0
101
Referenzfall
Referenzfall Var1
Referenzfall Var3
Referenzfall Var5
A1i6-1
A1w1-1
A1w2-1
WIF-1
WIF-2
WIF-3
Klassischer Ansatz
RGI [-]
RelativeHäufigkeit[%]
10-6
10-5
10-4
10-3
10-2
10-1
0
5
10
15 Referenzfall R-0
Mittelwert
Median
0.05 Quantil
0.95 Quantil
Minimum
Maximum
5.11E-3
4.58E-3
1.62E-3
1.06E-2
9.74E-4
1.46E-2
classical
PPA Scenario
approach
What If

16. Integration of Arguments
16
• Performance assessment (radiological consequences) still
main argument
• Complementary safety and performance indicators
NEA/RWM/R(2012)7: Indicators in the Safety Case
• Natural analogues
NEA/RWM/R(2013)10: Natural Analogues for Safety Cases of
Repositories in Rock Salt, Salt Club Workshop Proceedings 2013
NAWG, http://www.natural-analogues.com/

17. Requirement A:
The stored waste packages ought to be quickly and as close as possible enclosed
by rock salt in conjunction with the geotechnical barriers (containment).
Requirement B:
The containment providing rock zone remains intact (geological and geotechnical
barriers) and is not altered by internal or external events and processes (integrity
/ freedom from maintenance)
Requirement C:
A recriticality must be excluded at every stage of the repository evolution
(criticality exclusion)
 Specific objectives (14 principal goals)
 Strategic measures (17 design specifications and technical measures)
17Project Meeting KOSINA; Hannover 16.03.2016
Safety concept:
Bedded salt (KOSINA)

18. 18
From domal to bedded salt
Guiding principles
Design requirements
Specific objectives
 Strategic measures
Source: BGR
Source: BGR

19. 19
Domal vs bedded salt
Domal salt Bedded salt Safety and
Demonstration Concept
vertical extent horizontally layered,
thickness rock salt ≤ 200 m
Different safety margins
Underlying layers
CRZ-concept
Integrity analysis host rock
- temperature criteria
- dilatancy
Vertical boreholes
Shaft seals
Lateral
inhomogeneous
geology
horizontal extent Different safety margins
CRZ-concept
Disposal area
Drift seals / Drift disposal

20. National focus on Safety Case R&D
20
 FEP and scenarios
 Safety concept / Demonstration concept
 Integrity of geological and geotechnical barriers
 Geomechanical behaviour of rock salt
 Geomechanical behaviour of crushed salt
 Transport processes in crushed salt
 Uncertainty and sensitivity analysis
 Operational safety
 Operational safety vs. Long-term safety

21. Discussion of key technical issues
Jens Wolf
GRS gGmbH
7th US/German Workshop on Salt
Repository Research, Design, and
Operation
Washington, DC, September 7-9, 2016

22. Int. Focus on Safety Case R&D
[EC, IAEA, NEA since 2010]
22
 Forum on Stakeholder Confidence
 Socio-Technical Challenges for Implementing Geological Disposal
 Records, Knowledge Preservation and Memory (RK&M)
 Implementing Public Participation Approaches
 Monitoring
 Full Scale Demonstration of Plugs and Seals
 Implementing sustainable education programmes
 Biosphere Research
 Operational safety
 (…)

23. Discussion of key technical issues
23
Statements to discuss:
 Safety Case needs should lead R&D
 Safety assessment is the main element of the safety case
(SSG-23 4.4)
 Status of national programs is diverging
 Different R&D needs
 Safety Case R&D:
 How to achieve safety?
 How to demonstrate safety?
 How to manage uncertainties?
 How to communicate safety?
PAMINA (2008)
MeSA (2012)
SCS (2013), next 2018
GEOSAF

24. Discussion of key technical issues
24
Important topics such as
 Uncertainty and sensitivity analysis
 Scenario development
 Model development / Benchmarks
 Additional arguments (indicators, analogues)
are not adequately addressed in international activities