The document summarizes improvements made to waste disposal practices at Vaalputs, South Africa's low-level radioactive waste disposal facility. Concrete waste containers were cracking prematurely due to thermal cycling and corrosion. In response, Vaalputs implemented smaller trenches, improved container filling and design, strengthened inspection and quality assurance practices, updated waste acceptance criteria, and conducted research on container and trench cap performance. The improvements aimed to enhance long-term safety and strengthen stakeholder confidence in the facility.

1. IMPROVING WASTE DISPOSAL
PRACTICES AT VAALPUTS
IAEA Disponet Meeting Sweden, 4 October 2011
By:
Alan Carolissen
Senior Manager: Nuclear Liabilities Management

2. 2

3. LOW LEVEL WASTE DISPOSAL REPOSITORY:
VAALPUTS
3

4. 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.
4

5. 5
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
5.2m
8.0m
Drainage layer – 200mm
Backfill
Compacted clay cap
Natural cover
Top soil
Waste packages
50m
Shallow Land Disposal (SLD)
Near surface trenches for LLW

6. TYPES OF WASTE
ONLY SOLID OR SOLIDIFIED RADIOACTIVE WASTE
6
LLW in metal containers
LLW in concrete
containers
Spent fuel racks

7. 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)
7

8. RECEIVING WASTE
8

9. 9

10. 10

11. REHABILATED TRENCH
11

12. 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.
12

13. VP006 - Description

14. VP006 - Description

15. VP006 - Investigation

16. NCR-2004/0087 - Investigation

17. VP006 - Investigation

18. VP006 - Investigation

20. 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
20

21. IMPROVING WASTE DISPOSAL PRACTICES:
TRENCH MANAGEMENT

22. 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.
22

24. Typical near surface trench
6m
3m
1.5m
3m
X m

25. IMPROVING WASTE DISPOSAL PRACTICES:
CONTAINER FILLING

26. IMPROVEMENTS: CONTAINER FILLING
26

27. Drum Composition

28. C1-CONCRETE CONTAINER
Concrete drum
1.3 m
1.4 m
150 mm

29. C1-CONCRETE CONTAINER
Concrete drum
Metal liner
Void
1.3 m
1.4 m
150 mm

30. C1-CONCRETE CONTAINER
Concrete drum
Metal liner
Foam seal
Void
1.3 m
1.4 m
150 mm

31. C1-CONCRETE CONTAINER
Concrete drum
Metal liner
Foam seal
Waste Matrix Resin
Void
1.3 m
1.4 m
150 mm

32. C1-CONCRETE CONTAINER
Concrete drum
Metal liner
Foam seal
Cap
Void
1.3 m
1.4 m
150 mm

33. IMPROVEMENTS: CONTAINER FILLING
Insertion of expansion foam.
33

34. IMPROVING WASTE DISPOSAL PRACTICES:
CONTAINER DESIGN

35. IMPROVEMENTS: CONTAINER
Containers shall be so designed that withstand thermal cycling.
35
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

36. IMPROVEMENTS: CONTAINER
Containers 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
36

37. IMPROVING WASTE DISPOSAL PRACTICES:
IMPROVED INSPECTION & QA

38. Pre-shipment
inspections
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)

39. Process
Verification
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

40. IMPROVING WASTE DISPOSAL PRACTICES:
WAC IMPROVEMENTS

41. • 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

42. 42
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

43. WAC DEVELOPMENT
43
WAC
Long-term
safety
Operational
safety
Transport
safety
Stakeholders
Waste
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

44. IMPROVING WASTE DISPOSAL PRACTICES:
RESEARCH & DEVELOPMENT

45. EXPERIMENTAL PROGRAMME
• Trench cap performance
• Container performance
• Near field studies
• Trench cap cracked and subsided
• Simulation of possible conditions during institutional control
period

49. 49

52. 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

53. Thank You!!!
53