IMPROVING WASTE DISPOSAL PRACTICES AT VAALPUTS

IAEA Disponet Meeting Sweden, 4 October 2011

By:

Alan CarolissenSenior Manager: Nuclear Liabilities Management

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LOW LEVEL WASTE DISPOSAL REPOSITORY: VAALPUTS

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VAALPUTS COMMISSIONING

• Site selection completed in 1985• Site operating license granted in 1986• First waste shipment arrived in November 1986• Only solidified or solid low level waste are disposed

off.

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Red sand – 0,5 m

Red ‘clay’ – 10m

White ‘clay’ – 5m

Weathered granite – 3m

Fresh granite up to 100m

Aquifer

5 5555

DISPOSAL CONCEPT

Monitoring pipe

Natural Clay

5.2 m

8.0 m

Drainage layer – 200mm

Backfill

Compacted clay cap

Natural cover

Top soil

Waste packages

50 m

Shallow Land Disposal (SLD)

Near surface trenches for LLW

TYPES OF WASTEONLY SOLID OR SOLIDIFIED RADIOACTIVE WASTE

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LLW in metal containers

LLW in concretecontainers

Spent fuel racks

VAALPUTS WASTE INVENTORY• Design capacity

- 500 000 metal waste packages- 50 000 concrete waste packages

• Metal waste packages- 14 699 disposed of (3% of capacity)

• Concrete waste packages- 3 769 disposed of (8% of total capacity)

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RECEIVING WASTE

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REHABILATED TRENCH

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INITIATING EVENT: CRACKING OF CONCRETE WASTE CONTAINERS• Discovered damaged containers – May 1997• Was evident that cracking phenomenon has evolved over

period (1986 emplaced containers)• Cracks were observed on the rims, sidewalls and bases of

the containers.• Nuclear occurrence registered.• Independent sampling and environmental monitoring done

by Necsa, NNR, IAEA.• Results: No contamination outside disposal trenches.

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VP006 - Description

VP006 - Description

VP006 - Investigation

NCR-2004/0087 - Investigation

VP006 - Investigation

VP006 - Investigation

ROOT CAUSE IDENTIFICATION• Premature degradation of container due to prolonged exposure to

elements:- Thermal cycling- Corrosive effects of soil- Free liquid between drum wall and metal liner- Expansion of resin matrix.

• Huge trenches• Lack of understanding in container performance in repository

environment (container specs initially adopted from French design.)• Deficiencies in pre-disposal operational processes (handling, filling

and capping).• Insufficient QA control by waste generators

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IMPROVING WASTE DISPOSAL PRACTICES:

TRENCH MANAGEMENT

IMPROVEMENTS: TRENCH MANAGEMENT• Premature closure of trenches necessitated changes in

original trench design.• Concrete cut-off wall build at live end of waste stacks.• Provided a barrier against which backfill and capping

proceeded.• New smaller trenches are used

- Length depends on pre-defined number of containers delivered in concentrated campaigns.

- Backfilling within two months.- Capping within a year.

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Presenter

Presentation Notes

Slid Cobus

Typical near surface trench

6m

3m

1.5m

3m

X m

IMPROVING WASTE DISPOSAL PRACTICES:

CONTAINER FILLING

IMPROVEMENTS: CONTAINER FILLING

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Drum Composition

C1-CONCRETE CONTAINER

Concrete drum

1.3 m

1.4 m

150 mm

C1-CONCRETE CONTAINER

Concrete drum

Metal liner

Void

1.3 m

1.4 m

150 mm

C1-CONCRETE CONTAINER

Concrete drum

Metal liner

Foam seal

Void

1.3 m

1.4 m

150 mm

C1-CONCRETE CONTAINER

Concrete drum

Metal liner

Foam seal

Waste Matrix Resin

Void

1.3 m

1.4 m

150 mm

C1-CONCRETE CONTAINER

Concrete drum

Metal liner

Foam seal

Cap

Void

1.3 m

1.4 m

150 mm

IMPROVEMENTS: CONTAINER FILLINGInsertion of expansion foam.

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IMPROVING WASTE DISPOSAL PRACTICES:

CONTAINER DESIGN

IMPROVEMENTS: CONTAINERContainers shall be so designed that withstand thermal cycling.

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PARAMETER MAXIMUM MINIMUM AVERAGE

Relative humidity 100% 1% 57 %

Ambient temperature

47.1 °C - 7.8 °C 16.5 °C

22 cm soil temperature

38.3 °C 5.6 °C 22.4 °C

60 cm soil temperature

38.2 °C 6.0 °C 22.4 °C

Wind speed 27.2 ms-1 0 ms-1 4.3 ms-1

Atmospheric pressure

915 hPa 879 hPa 883.9 hPa

MAMSL 1 000 m

IMPROVEMENTS: CONTAINERContainers shall be so designed that:

• Following emplacement in the repository, the mechanical integrity of the waste container shall be capable of being maintained for at least the operational life (100 years) of the repository.

• The compressive strength shall be compatible with the repository stacking pressures, including the overburden imposed by the trench cap.

• The tensile strength shall be compatible with the forces that may be exerted on the container by the waste matrix due to, e.g., corrosion expansion, thermal expansion, etc.

• Iron chloride and iron carbonate in cement mixture exclude due to reducing soil environment

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IMPROVING WASTE DISPOSAL PRACTICES:

IMPROVED INSPECTION & QA

Pre-shipmentinspections

Receiving inspections

On arrival at the repository• Condition of shipment;• External package condition, package closure;• Radiological measurements (dose rate, surface

contamination)• Compliance with transport regulations;• Package labelling / unique identification;• Package mass;• Container type.

IMPROVED INSPECTION PRACTICES

Conducted at waste supplier’s site • Visual inspection (waste packages)• Consignment records (data packs)• Status of NC’s and waivers• Process implementation (PDO WAC)

ProcessVerification

In future will include•Destructive testing•Non-destructive testing (X-ray)•Verification of nuclide inventory (direct measurement, random sampling)•Mass verification (weighing)

•Technical audits•Pre-shipment inspections•Receiving inspections•Witness process qualification•Witness process operations•Documented procedures•Non-conformances, CA and PA

IMPROVED QA PRACTICES

IMPROVING WASTE DISPOSAL PRACTICES:

WAC IMPROVEMENTS

• Specific to Koeberg• Added:

- Nuclides to be reported- Administrative procedures (documentation, application,

approval, etc.)- Quality requirements (data pack, process qualification &

verification introduced)- Radiological requirements- Packaging & labeling requirements- Prohibited items and substances- Non-conforming waste- Waivers

EVOLUTION OF WAC: WAC Rev 6

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EVOLUTION OF WAC: WAC Rev 6(a)

Added:• Audit/review of PDO’s QA system• Specific criteria and concessions wrt pH• TRU’s up to 4000 Bq/g per waste package• Toxic and corrosive substances• Passively safe waste form• Tamper seals• NCR’s from PDO’s• WAC Rev 7 currently under development

WAC DEVELOPMENT

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WAC

Long-term safety

Operational safety

Transport safety

StakeholdersWaste

suppliers

Repository economics

Quality control

•Safety•Health•Environment•Radiological•Regulatory

•WM plans•Historical waste•Current waste•Future waste

•Resources•Commercial issues•Disposal contract•Disposal cost•Waste ownership

•Regulators•Public•Government•Waste suppliers

•TS-R-1•WP performance•Nuclide limits•Radiological control

•Inspection•Testing•Verification•Non-conformities•Data packs•Records

•Disposal concept•Safety assessments•Performance assessments

IMPROVING WASTE DISPOSAL PRACTICES:

RESEARCH & DEVELOPMENT

EXPERIMENTAL PROGRAMME

• Trench cap performance• Container performance• Near field studies• Trench cap cracked and subsided• Simulation of possible conditions during institutional control

period

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CONCLUDING REMARKS

Continual improvements in disposal practices are imperative to:

• Deepen and strengthen stakeholder confidence

• Enhance and strengthen the plausibility and robustness of the disposal safety case

Thank You!!!

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