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Disposal of radioactive waste

P. Ormai

Waste Technology SectionDivision of Nuclear Fuel Cycle and Waste Technology

South Africa - IAEA Nuclear Energy Management School 17-28 October 2016, Cape Town, South Africa

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LecturerPeter ORMAIHungarian nationality

Degree in chemical engineering and PhD in radiochemistry

1977-1998: Different managerial positions at Hungarian NPP

1998-2011: Chief engineer of the Radioactive Waste Management Agency (PURAM)

2011-: Waste Disposal Specialist of the IAEA Waste Technology Section in the Division of Nuclear Fuel Cycle and Waste Technology

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Presentation outline

Safety objective and criteria for the disposal

Components of the disposal system

Take away pointsDisposal facilities

Safety of disposal

Practical examples

How is safety to be evaluated and

confirmed?

Useful IAEA references

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Basis of radioactive waste management (WM)

The residual material (waste) hierarchy

The most effective WM strategyis the prevention of waste generation.

PREDISPOSAL

End point

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DisposalOnly disposal can provide safe, secure and environmentally appropriate end-point to the

radioactive waste.

Why should radioactive waste be disposed of and not just stored?

STORAGEAlthough storage of RW is an a essential

part of WM, it is always a temporary solution.

Ethical / sustainability / security concerns

• Storage requires active controls;• Consideration is needed of the

possibility of periodic renewal;• Guardianship is not a robust strategy

over the long term;• Indefinite storage means passing the

responsibility to future generations (very expensive);

Ultimate safety requires a stable endpoint !

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`SOURCE` IMPACT TAKER

DISPOSAL SYSYTEM

Barriers with safety functions

Concept of disposal

BIOSPHERE

ISOLATION

CONTAINMENT (low- release)

Containment:avoid or minimize the release of radionuclides (delay and decay)

Isolation: - keep the waste and its associated hazard apart from the accessible biosphere- minimize the influence of factors that could reduce the integrity of the disposal facility

The goal : to keep hazardous radioactive wastes away from

people

waste

RETARDATION (dilute and disperse)

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Specific Safety Requirements SSR-5

This publication sets out the safety objective and criteria for the disposal of all types of radioactive waste and establishes the requirements that must be satisfied in the disposal of radioactive waste.

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Aims of disposal

Disposal: emplacement of radioactive waste into a facility or a location with no intention of retrieving the waste.

The effort and expense required to provide containment and isolation will scale the level of hazard presented by the waste and its longevity.

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Design concepts for safetyDisposal system: disposal facility and the geological

environment in which it is sited

The various elements of the disposal system, including natural features, physical components and control procedures, contribute to performing safety functions in different ways over different timescales.

All disposal designs aim: determine which combination of choice of site, depth of

disposal, engineered barriers and institutional controls be relied upon to prevent or minimize the exposure to man.

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Elements of the disposal system

Engineered barriersNatural barriers

Stable environment can ensure for long time the non-disturbance of the waste disposed of

Barriers: features (natural or man-made) that prevent or restrict migration of radionuclides

• provide structural stability • minimise contact of water with the waste• restrict human intrusion into the disposal

units • prevent or delay the movement (e.g.

migration) of radionuclides from the disposal facility

Defence in depth principle: implementation of complementary and redundant levels of protectionThe overall performance of the disposal system shall not be unduly dependent on a single barrier or function (-> robustness of the disposal system).

A system of multiple barriers (multiple safety functions) gives greater assurance of isolation and helps ensure that any release of

radionuclides to the environment will occur at an acceptably low rate.

A safety functions: limited corrosion, dissolution, leach rate and solubility, retention of radionuclides and retardation radionuclide migration

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Waste types & relevant disposal options (1)

IAEA Waste classification scheme provides a general system of classification accommodating various waste types and disposal solutions (IAEA G-SG-1)

This scheme offers a useful initial consideration despite it identifies only

boundaries & provides guidance and does not prescribe specific disposal solution for

certain waste types.

The task is to adapt / match particular waste streams to the possible disposal solutions

Half-life

Spe

cific

act

ivity

VSLW: T1/2 less than 100 days, so during the storage period of several years or less it will reach exempt level and can be recycled or disposed of in an ordinary / non-radioactive landfill.

EW: This has level f activity is close to background. For legal purposes, it is defined as not radioactive.

HLW: Heat generation significant, activities around 5x104 to 5x105 TBq/m3

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Deep geological disposal

Near surface disposal

Geological disposal

VLLWVSLW

LLW

ILW

SNF/HLW

Waste types & relevant disposal options (2)

• High reliance on ENGINEERED BARRIERS, supported by natural site characteristics

• Institutional control may continue after repository closure to ensure safety

• High reliance on NATURAL BARRIERS, supported by engineered and chemical barriers

• Possible post-closure monitoring, but concept rely on passive safety

increasingly

robust isolation

and containment

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The selection of a disposal option depends on many factors, both technical and administrative.

Selection of disposal option (1)

• radioactive waste management policy

• overall disposal strategy in the country

• national legislative and regulatory requirements

• political decisions • social acceptance

• waste inventory• waste characteristics• availability of suitable host media• conditions of the country such as

climatic conditions and site characteristics

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Radioactive waste stream

END POINT

Long-term

storage

decay storage

surface trenchfacility

engineered surface facility

geologic repository (intermediate depth)

geologic repository (deep)

shallowborehole

deep borehole other

VSLWlow volume

large volume

VLLWlow volume

large volume

LLWlow volume

large volume

ILWlow volume

large volume

SNF/HLW

DSRS

short-lived

long-lived

High activity (SHARS)

NORM low volume

large volume

preferable acceptablePossible but needs to be assessedfrom technical or economic aspects

Not possible for technical reason

Based on the IAEA Waste classification scheme VSLW, VLLW, LLW, ILW, HLW can be differentiated (special consideration may be given to DSRS, NORM/TENORM Uranium M&M waste).

When assessing the disposal options, consideration should also be given to the volume of waste to be disposed of.

Safety is the fundamental objective of RW disposal. Several options above can be excluded from safety consideration point of view.Other options can be ruled out on the grounds of technical reasons (not feasible, difficult to implement, etc.).

Based on the generic safety considerations, the characteristics and volume of waste potentially acceptable or preferable options can then be identified. There might be options which need to be more closely assessed from technical and economic aspects.

Not possible for safety reason

Selection of disposal option (2)

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Radioactive waste stream

END POINT

decay storage

surface trench facility

engineered surface facility

geologic repository

(intermediate depth)

geologic repository

(deep)

shallowborehole

VSLWLow volume

Large volume

VLLWLow volume

Large volume

LLWLow volume

Large volume

ILWLow volume

Large volume

SNF/HLW

DSRSShort-lived

Long-lived

SHARS

NORMLow volume

Large volume

preferable acceptableNot possible for safety reason

Possible but needs to be assessedfrom technical or economic aspects

Not possible for technical reason

Selection of disposal option (3)

This is only for qualitative screening!For each disposal facility specific safety assessment

is required.

IAEASafety Case development: progressive approach to support the major decision points in the repository development

Safety case: (IAEA Safety Glossary 2007):“A collection of arguments and evidence to demonstrate the safety of a facility or activity.

Safety case contentStructured approach that starts with the SC context and includes the management system, peer reviews, uncertainties, limits, controls and conditions etc.

Demonstration of safety

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Safety Assessment

Iterative evaluation process

Assessment of the future behaviour of the repository

Considered situations:

• Reference situation• Very probable natural events• Altered situations

• Verification of the favourable behaviour of the performance of the disposal components associated to safety functions.

• Verification of the various objectives and criteria assigned to components, taken individually, then together.

• Evaluation of the disturbances caused by the construction of the repository (e.g. mechanical, chemical, hydraulic effects on the geological medium).

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Disposal examples

Near-surface disposal facilities (trench, vault)

Geological disposal facilitiesFor LLW and ILW

Ezeiza, Argentina Vaalputs, South AfricaWolsong, KoreaWIPP, USA

Richland, USA Rokkasho, Japan

EL-Cabril Spain

SFR, Sweden

Bátaapáti, Hungary Loviisa, Finland

Mochovce, Slovakia

Morsleben, Germany

Centre de l’Aube , France

China

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• Borehole facilities offer safe, simple, economic alternative for all DSRS

• No decrease in safety standards• Small footprint• Broad range of suitable (safe) site

properties• Safe implementation with limited

resources

Disposal of DSRS is an issue in many countries, often with limited infrastructure and

resources.

Disposal of disused sealed radioactive sources (DSRS)

IAEA BDC: Borehole Disposal Concept

Sources conditioned in capsules and containers

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In a typical multi-barrier design, either a thick-walled or a highly corrosion-resistant metal container will be placed around the waste.

This could be protected in turn by a shell, or ‘buffer’ of compacted clay or cement, which isolates the container from the surrounding rock and from water in the rock.

The host rock formation in which the repository is built provides a further barrier and the overall geological environment back to the surface constitutes the outer shell of the multi-barrier system

For SF, HLW, ILW-LL the only long term solution is deep geological (DG) disposal.

Spent fuel in copper canister

Vitrified HLW in stainless steel canister

Disposal of spent fuel (SF) and high level waste (HLW)

Passive long-term safety does not depend at all on post-closure institutional control.

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RD&D

Sweden: Bentonite laboratory

Sweden: Canister laboratory

France: URL, 10 years of in-situ RD&D

France: TBM test in Meuse-Haute-Marne URL

Sweden:Äspö Hard Rock Laboratory, in

operation since 1996

Finland: Disposal borehole demonstrationConstruction & Emplacement

No purpose built DISPOSAL facilities exist yet for HLW or SF disposal but some programs are advanced.

Finnish government granted a construction license for geological repository in November 2015.

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Satisfying social and political acceptability

Sound governance must secure and maintain acceptance

One of the greater challenges is gaining and maintaining societal acceptance

Acceptability is almost entirely concerned with the Process:

• clarity of goals, objectives, uncertainties, impacts• transparency of process, information and findings• involvement of concerned parties from the outset• empowerment of key parties in decision process• staging, in easy steps• right of community veto, up to an agreed point

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National vs. Multinational / Regional cooperation solution

1998

2004

2005

2011

2006

2016

Joint Convention – Preamble:„…. in certain circumstances, safe and efficient management of SF and RW might be fostered through agreements among Contracting Parties to use facilities in one of them for the benefit of the other Parties, particularly where waste originates from joint projects.”

The IAEA supportive to the regional / multinational ideas but also cautious.

Each country is ethically and legally responsible for its own wastes, in accordance with the provisions of the

Joint Convention.

Therefore the default position is that all nuclear wastes will be disposed of in each country

concerned with nuclear power generation or part of the fuel cycle.

IAEAExtensive experience and technical knowledge exists for disposal of LILW.

Repository type/design depends on several factors and boundary conditions.

Technical options based on compliance with national policies, available funding, human resources and public sensitivities.

Take away points (1)The effort and expense required to provide containment and isolation will scale with the level of hazard presented by the waste and its longevity.

“Feasibility” is not only a technical issue, social acceptance is vital.

A “best” solution remains elusive – a “good” solution meets all safety requirements, and is accepted (or at least tolerated) by its stakeholders.

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Take away points (2)

Deep GD is considered the most appropriate solution for the long-term management of HLW and SF, should SF be declared a waste.

The safety assessment cannot, by itself, adequately demonstrate the safety of the disposal system. A holistic view is needed, with a broader range of arguments and activities to justify disposal of RW (safety case).

Safe, secure, sustainable, technology exists but development timescale is long.

Acceptance is a difficult but achievable.

Reversible for decades so allows considerable flexibility.

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Further useful IAEA references

• Site aspects• Design• Construction • Operation• Closure• Post closure• Safety assessment • Management system

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International Atomic Energy Agency

SF and RW management, Decommissioning and Environmental remediation Curriculum Map

IAEA E-learning

International Atomic Energy Agency

International Atomic Energy Agency

Thank you!