1. High Burn-up Radioactive Spent Fuel
Dr Paul Dorfman
Nuclear Consultation Group
Helsinki, 8 May 2009

2. Rad waste – US experience
Obama withdraws funding from Yucca Mountain geological rad waste dump
‘After spending billions of dollars on the Yucca Mountain Project, there are still significant questions about whether nuclear waste can be safely stored there’ – Barak Obama, Feb 2009

3. UK rad waste experience
Current legacy - 75 billion sterling
CoRWM 1 – deep disposal concept subject to intensive research and development
To date very limited R & D undertaken
Rhetoric of deep disposal
Until then - surface storage

4. Prof Andy Blowers OBE, Open University, member of NIREX, member of Committee on Radioactive Waste Management 1 (CoRWM)
‘There is, as yet, no proven technical solution for the long-term management of radioactive wastes’

5. Rad waste – French experience
after 15 years of inconclusive research on deep underground burial, the failure to find a solution led the French parliament to authorize continuation of research on disposal and on long-term storage of the wastes

6. Liberalisation of the energy market in Europe
Pressured Electricité de France (EDF) to become more competitive
Resulted in the testing of high burn-up fuel
European Pressurised water Reactor (EPR) ‘re-engineered’

7. EdF ‘Optimization’ study
Decrease in cost could be achieved if:
15% increase in the reactor’s power
Fuel was enriched to up to 4.9% uranium235
Spent fuel discharged at a burn-up of 60,000 MegaWatt days per tonne of Uranium (MWd/tU)

8. Burn-up rate
Measure of the amount of electricity extracted from a given amount of fuel expressed in thousand megawatt days per tonne of uranium (MWd/tU)

9. High burn-up fuel
More enriched fissile uranium used as reactor fuel to increase burn-up rate
Left in the reactor for longer
High burn-up spent fuel is hotter and more radioactive than conventional spent fuel
Much tighter ‘safety envelope’
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10. Burn-up rate AGR burn-up MWd/tU 5,000 - 30,000 EPR burn-up MWd/tU
45, ,000

11. Spent fuel pools
KW sq m at 5 yrs:
AGR – 10.8
EPR – 17.2

12. US Nuclear Regulatory Commission: NUREG-1567 Standard Review Plan for Spent Fuel Dry Storage Facilities, Final Report, 2000
‘Limited data to show that the cladding of spent fuel with burn-ups greater than 45,000 MWd/MTU will remain undamaged during the licensing period´

13. ‘These burn-up dependent effects could potentially lead to failure of the cladding and dispersal of the fuel during transfer and handling operations’

14. FIAEA-TECDOC-1523 : Optimization Strategies for Cask Design and Container Loading in Long Term Spent Fuel Storage, 2006
‘Predictions of the long term behaviour of cladding have significant uncertainties’
Fuel cladding capable of staying in the reactor for longer has been designed without regard to the long-term consequences

15. Hotter and more radioactive
Much more radioactive isotopes in the immediate release fraction
11 x C135 C137
Changes in physical characteristics of the fuel

16. Risk Implications
High burn up increases risk of radioactive releases as the fuel cladding gets thinner
Increased risk persists throughout storage and disposal
Take up much more space in any store
Much bigger repository

17. IAEA-TECHDOC-1558: Selection of Away-From-Reactor Facilities for Spent Fuel Storage. A Guidebook., 2007
‘Higher burn-up of fuel has a significant impact on the choice of the storage option and on the design of storage systems, due to the increased decay heat… imposing a higher cooling load to the storage system’

18. Higher heat Packaging must cope with higher heat transfer
Needs new materials to withstand higher temperatures on components and materials
Higher enrichment - spent fuels with higher gamma and neutron radiation
Needs more shielding

19. Rad Repository Heat Output
All barriers can be compromised by heat build-up from high burn up spent fuel
100 degree C temperatures at canister surface - Bentonite clay may not expand to seal containment
Fractures in containers or surrounding rock – increases risk of rad leak

20. 2006 US committee on safety of spent fuel storage
Concluded that the cooling and shielding:
‘Could be compromised by a terrorist attack that partially or completely drains the spent fuel pool’
Safety and Security of Commercial Spent Nuclear Fuel Storage: Public Report (2006). US Board on Radioactive Waste

21. Safety
Safety will depend on continuous removal of the huge thermal power of high burn-up spent fuel
Additional pumps, back-up electricity supplies and backup water supplies
All systems vulnerable to mechanical failure or deliberate disruption

22. IAEA-TECDOC-1299: Technical and economic limits to fuel burnup extension, Proceedings of a Technical Committee, San Carlos de Bariloche, Argentina, 2002
‘Any benefits of lower electricity costs during the operation of reactors in this way will be offset by an increase in the cost of managing the spent fuel’

23. Safety limits
High burn-up spent fuel trend has already reached the 45,000 MWd/tU limit for dual purpose storage and transportation casks

24. IAEA-TECDOC-1433: Remote technology applications in spent fuel management, 2005
‘General burn-up trend is heading up to a still higher level, even though there should be a plateau level in confrontation with regulatory constraints’

26. Conclusions
Disposal of spent fuel in deep underground repositories is unproven
No experience of high burn-up fuel stored over very long periods
However degradation of high burn-up fuel elements over very long storage periods is certain
Retrieval, encapsulation, emplacement cannot be assumed to be possible - let alone safe

27. High burn-up fuel is more demanding at every stage of the nuclear cycle
From reactor to cooling ponds to drying and storage in dry casks to eventual storage
Increase worker and public exposure to radiation

28. Containment materials after cooling pond are still experimental
Decades additional cooling time
Spaced out in repositories - increasing ‘footprint’
Uncertainties about high burn-up spent fuel - any fixed disposal cost exposes future taxpayer to huge liabilities

29. Dense-packing of high burn-up spent fuel in the pools increases the likelihood of a fuel fire and meltdown should the pool water be lost in an accident or terrorist attack
IAEA response to ever higher fuel burn-up is to say regulatory confrontation is required - when?

30. Driven by financial constraints
Nuclear industry has raised the power output of proposed reactors
Difficulties of managing and disposing radioactive waste are becoming insuperable
Burdens of cost, effort, worker radiation dose transferred to future generations