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

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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

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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)

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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)

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Safety concept

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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

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Management of Uncertainties

• Scenario uncertaintiesScenario analysis (FEP, scenario development)

• Data and parameter uncertainties Uncertainty and sensitivity analysis

• Model uncertaintiesBenchmarking, uncertainty and sensitivity analysis

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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

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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

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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

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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)

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From domal to bedded salt

Guiding principlesDesign requirementsSpecific objectives

Strategic measures

Source: BGR

Source: BGR

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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

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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 (…)

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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

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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