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Safety Case: German Approach- from ISIBEL to KOSINA
Jens WolfGRS gGmbH
7th US/German Workshop on Salt Repository Research, Design, and
OperationWashington, 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.
Source: IAEA SSG-23
3Source: NEA No. 3679, 2004 Source: NEA No. 78121, 2013
Safety Case: Nature and Purpose
4
Elements of the Safety Case
Safety Case Context Safety Strategy
System description
Safety assessment
Limits, controls and conditions
Integration of safety argumentsItera
tion
and
desi
gn o
ptim
izat
ion M
anagement of uncertainty
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
Preliminary Safety Case Comprehensive Safety Case
Safety Case R&D
6
Elements of Safety Case R&DR&D in Germany
Safety Case Context Safety Strategy
System description
Safety assessment
Limits, controls and conditions
Integration of safety argumentsItera
tion
and
desi
gn o
ptim
izat
ion M
anagement of uncertainty
Source: IAEA SSG-23
7
Safety Case: R&D in Germany
ISIBEL
ISIBEL-II
VSG
AnSichT
KOSINA
clay
CHRISTA
salt crystalline
BASEL
bedded
domal
t2016
X R&D BMWi+ support international cooperation (NEA/IAEA)
8
Safety Strategy
How to achieve safety? Regulations / Geology / Repository Concept
Protection GoalsSafety Principles / Safety FunctionsGuiding PrinciplesDesign Requirements (…)Objectives Measures
How to demonstrate safety?
Safety Case Context Safety Strategy
System description
Safety assessment
Limits, controls and conditions
Integration of safety arguments
Itera
tion
and
desi
gn o
ptim
izat
ion M
anagement of uncertainty
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
11
Safety concept: Containment-providing rock zone
REP
CRZ
HR
OVHROV
REP
CRZ
OverburdenHost RockContainment-providing rock zoneSeal of CRZ
Disposal Area
Rock body with safety-relevant
barrier functionRock body without safety-relevant barrier function
Seals
Geological barrier
106 a
Crushed salt backfill
Requirement A,C
Requirement B
12
Management of Uncertainties
• Scenario uncertaintiesScenario analysis (FEP, scenario development)
• Data and parameter uncertainties Uncertainty and sensitivity analysis
• Model uncertaintiesBenchmarking, uncertainty and sensitivity analysis
13
Demonstration concept
Containment:- CRZ: dimension- CRZ: preservation- Integrity of barriersHuman
intrusion
Proof ofsub-
criticality
Non-radio-logical
protectiongoals
Opera-tionalsafety
Handling ofuncertainties:- data- model- scenario
Safety demonstration concept
Radiological safety indicator
Assessment
Evolution(s) of repositorysystem
14
Radiological Indicator
RGI > 1
Assessment of safe containment
RGI = 0
No contactbetween
solution andwaste
No release ofRN into thegas phase
No releaseof RN
out of CRZ
0 < RGI ≤ 1
Difussivetransport of
RNAdvective
transport ofRN
Repository system in thisform (layout) not suitable
Complete containment
Assessment by simplified statement
Criteriaaccording to
SafetyRequirements
fulfilled
RGI > 1
Criteriaaccording to
SafetyRequirements
not fulfilled
Stage 2
Stage 3
Stage 1
Stage 4
REP
CRZ
HR
OV
15
Radiological consequences
Zeit [a]
RG
I[-]
103 104 105 106 10710-6
10-5
10-4
10-3
10-2
10-1
100
101
ReferenzfallReferenzfall Var1Referenzfall Var3Referenzfall Var5A1i6-1A1w1-1A1w2-1WIF-1WIF-2WIF-3Klassischer Ansatz
RGI [-]
Rel
ativ
eH
äufig
keit
[%]
10-6 10-5 10-4 10-3 10-2 10-10
5
10
15 Referenzfall R-0
MittelwertMedian0.05 Quantil0.95 QuantilMinimumMaximum
5.11E-34.58E-31.62E-31.06E-29.74E-41.46E-2
classical PPA Scenario
approach
What If
16
Integration of Arguments
• Performance assessment (radiological consequences) still main argument
• Complementary safety and performance indicatorsNEA/RWM/R(2012)7: Indicators in the Safety Case
• Natural analoguesNEA/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/
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
From domal to bedded salt
Guiding principlesDesign requirementsSpecific objectives
Strategic measures
Source: BGR
Source: BGR
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 layersCRZ-conceptIntegrity analysis host rock - temperature criteria - dilatancyVertical boreholesShaft seals
Lateral inhomogeneousgeology
horizontal extent Different safety marginsCRZ-conceptDisposal areaDrift seals / Drift disposal
20
National focus on Safety Case R&D
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
Discussion of key technical issues
Jens WolfGRS gGmbH
7th US/German Workshop on Salt Repository Research, Design, and
OperationWashington, DC, September 7-9, 2016
22
Int. Focus on Safety Case R&D[EC, IAEA, NEA since 2010] 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
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 2018GEOSAF
24
Discussion of key technical issues
Important topics such as Uncertainty and sensitivity analysis Scenario development Model development / Benchmarks Additional arguments (indicators, analogues)are not adequately addressed in international activities