Treatment options for the disposal of radioactive graphite wastes

1. Treatment options for the disposal of radioactive graphite wastes A.J. Wickham Visiting Professor, The University of Manchester, UK; Nuclear Technology Consultancy PO Box 50, Builth Wells, Powys LD2 3XA, UK confer@globalnet.co.uk M.I. Ojovan International Atomic Energy Agency, Vienna, Austria INGSM-15, 2014

2. A Squash Court in Chicago

3. A Squash Court in Chicago

4. Some examples (1)

5. Early UK Magnox (schematic) Some examples (2) UK AGR (view of graphite stack)

6. Some examples (3) Soviet-designed RBMK

7. Some examples (4) Fuel-element sleeves (UK AGR)

8. IRRADIATED NUCLEAR GRAPHITE: • Mostly from reactor moderators and reflectors • Some from nuclear fuel elements • Fast neutrons cause ‘damage’ to the graphitic crystal structures leading components to shrink and distort, to crack, and therefore, long-term, can result in the reactor being closed down because fuel and control rods cannot be guaranteed to move freely; • Ionising radiation (principally gamma) results in oxidation if the graphite is in air or (most often) carbon dioxide; • Slow neutrons create new radioactive isotopes both from the graphite (i.e. 14C) and from impurities. What is i-graphite?

9. IRRADIATED NUCLEAR GRAPHITE: • Mostly from reactor moderators and reflectors • Some from nuclear fuel elements • ... This material contains radioactive isotopes created within the material, plus additional radioactive contamination “picked up” during operation (coolant-borne dusts, for example) • Moulds for nuclear weapon warhead material • ... This material moderately contaminated with fissile isotopes including α-emitters What is i-graphite?

10. The UK has 80,000 tonnes or irradiated graphite wastes; world-wide there are 250,000 tonnes. France (~30,000 tonnes) and Ignalina NPP in Lithuania, (3,400 tonnes) need a quick solution... • There are no suitable disposal facilities yet. • What to do? The Problem • Options are: • ‘Safe Storage’ in reactor vessels or containments • Progress with deep repository construction • Case for shallow repository disposal • Do nothing! • Think laterally!

11. Remove graphite from the reactor containment (methodology might depend upon what happens after); • ?? Package and store ?? • ?? Treat either to give useful product or to reduce radioactivity ?? • ?? Dispose in “temporary” sub-surface facility ?? • ?? Chemical / physical treatment, perhaps to reduce volume or to “consume” completely ?? • Irretrievable disposal in suitable deep repository (or in suitable cases, a shallow repository) The Disposal Stages

12. Unfortunately, the graphite and fuel blocks remain in ‘temporary’ storage • Fort St. Vrain, USA Successful Core Dismantling

13. Fort St. Vrain, USA • WAGR, UK Successful Core Dismantling “If your decommissioning plan involves building a new building, then it is the wrong plan”

14. Fort St. Vrain, USA • WAGR, UK • GLEEP, UK Successful Core Dismantling

15. FORT St. VRAIN, USA – UNDERWATER (for shielding reasons unrelated to the graphite itself) • WAGR, UK – In air: remote handling, questions of dust explosibilitysatisfactority resolved • GLEEP, UK – In air, and by hand (very low irradiation), also allowing 14C to be removed by calcination in an industrial non-nuclear facility, taking advantage of the unexpected mobility of this isotope • BROOKHAVEN, USA – In air with viscous sprays, remote handling... THE ‘BRUTALIST’ METHOD! Successful Core Dismantling

16. Remote Graphite Removal Machine

17. Contamination Control Enclosure

18. Graphite Removal (1) Note also that this graphite contains significant Wigner energy and that no problems were encountered... Note use of ‘Fixative’ for Dust and Contamination Control

19. Graphite Removal (2)

20. Transfer out by ‘Supersack’

21. ‘Supersacks’ placed in ‘Industrial Containers’ and shipped out to Nevada test site for storage

22. United Kingdom: Primarily considering a deep repository option: mechanical dismantling after lengthy safe-storage is the present intention, but there is now low-key support for research into alternative strategies; Official Positions

23. France:Official strategy was for a shallow site for ‘graphite and radium-bearing wastes’: however, this has run into difficulties and a deeper site is under consideration. Alternative strategies for graphite treatment and disposal are back on the French agenda anyway now because... Official Positions ANDRA is obliged (by law) to find and approve a solution for disposal of French graphite by 2016... Thus, for them, work in this topic area is dynamic and extensive!

25. Japan (Tokai 1):Present plan unclear after initial interest in incineration for some of the material (fuel sleeves and reflector at least) mitigated by concerns about 14C releases; • Italy/Spain: One ‘Magnox’ type reactor each: likely to follow French or UK strategy; • Germany (2 HTR prototypes): disposal to salt dome planned, but unique issue (discussed later) Official Positions

27. USA (Hanford): Most plant ‘mothballed’ with intent to dispose of the graphite eventually within the Hanford reservation: recent plan to fully dismantle the KE reactor has been overtaken by concerns about the isotopic content of the graphite and the consequent restrictions upon its disposal there; • Brookhaven: SUCCESS!! – after a fashion: material moved to Nevada test site; • Fort St. Vrain:- graphite and fuel blocks remain in ‘temporary’ storage. Official Positions

28. Russia:No plan beyond ‘safe storage’ on reactor sites: a lot of graphite from production reactors and from Beloyarskaya is fuel-contaminated and thus presents special issues; • Ukraine (Chernobyl): Clearly a special case: the graphite from the damaged core has special issues, and a plan for mechanical dismantling of the undamaged reactors has been prepared; Official Positions

29. Lithuania (Ignalina):Active discussion of options, and preparations, in response to EU obligations, and also the desire to re-utilise the site (and the incumbent workforce) for a new plant: POSSIBLY WILL BE THE ‘LEAD’ IN DISMANTLING A FULL-SIZE COMMERCIAL REACTOR Official Positions The declared position, which cannot now be achieved, is to dismantle one reactor by 2016 and the second by 2020 – delayed AT LEAST six years

30. EdF CIDEN plan underwater dismantling for later UNGG plant – argument thought to be based on concerns of dust explosion risk initially, but CNPP work showed that was of no concern: now argument is based upon shielding. However, this will generate a lot of additional waste: - contaminated water, resin beds, plant items... ... Why use water when it is perfectly fine in air, as WAGR and Brookhaven have demonstrated? ... ... And do you actually need the complex and expensive engineering necessary to remove intact blocks? ...if you don’t, maybe use the ‘Brookhaven Bulldozer’... or something specifically designed with the eventual destiny of the graphite in mind? Future Core Dismantling

31. ...and, if you want ground material for a subsequent process, just go to the collection-hopper stage... “Nibble and Vacuum” Even transportation of finely-ground graphite in an aqueous foam is possible.

32. Pile 1 has distributed damaged fuel and isotope cartridges, along with a high Wigner energy content... • For example: UK Windscale Piles Special Problems

33. For graphite with significant Wigner energy, a disposal route involving heating of batch quantities solves at least one problem... • For example: UK Windscale Piles Special Problems Offers useful experience of special problems, but also offers an excuse for delay!

34. 1984: Keynote EU analysis • 1995: IAEA Technical Meeting “Graphite Moderator Lifecycle Technologies”, Bath UK • 1999: IAEA Technical Meeting “Nuclear Graphite Waste Management”, Manchester, UK • 2006 – 2012: EPRI “Graphite Decommissioning Initiative”: six comprehensive reviews on all aspects of i-graphite disposal • 2007: IAEA Technical Meeting “Progress in Radioactive Waste Management”, Manchester, UK • 2008 -2013: EU CARBOWASTE project • 2011 - 2014: IAEA Collaborative Research Programme “Treatment of Irradiated Graphite to meet Acceptance Criteria for Waste Disposal” Initiatives

35. 1984: Keynote EU analysis • 1995: IAEA Technical Meeting “Graphite Moderator Lifecycle Technologies”, Bath UK • 1999: IAEA Technical Meeting “Nuclear Graphite Waste Management”, Manchester, UK • 2006 – 2012: EPRI “Graphite Decommissioning Initiative”: six comprehensive reviews on all aspects of i-graphite disposal • 2007: IAEA Technical Meeting “Progress in Radioactive Waste Management”, Manchester, UK • 2008 -2013: EU CARBOWASTE project commences (ends March 2013) • 2011 - 2014: IAEA Collaborative Research Programme “Treatment of Irradiated Graphite to meet Acceptance Criteria for Waste Disposal” Initiatives

36. The IAEA does NOT prescribe policy on radwaste management. • The objective of the CRP is to advise Member States of the various options which are being researched, to enable them to make an informed decision on the correct policy for their situation Role of IAEA

37. A significant reduction in waste volume or packaging requirements; • Pre-treatments which either significantly reduce the radioisotope content of the graphite or facilitate other processing options, or both; • A significant cost saving, either through operational efficiencies or by allowing a useful product or products to be recovered from the material; • A favourable timescale (an earlier option to achieve some disposal result which would otherwise be delayed). Objectives of CRP

38. Behaviour of radioactive material from the graphite in terms of handling, packaging, treatment options, storage (leaching), environmental impact... • Short-term issue only – most gamma emitters present • Issue during ‘operational period’ of a repository – 3H (tritium, weak beta emitter) • Long-term issues (perceived) – weak beta emitters with very long half lives – 14C and 36Cl What are the issues?

43. Half-life 5,760 years • Considered an issue if in organic form (methane emissions); also problem with 14C in inorganic (carbonate) form, especially in confined environments... • Formed from 13C and 14N – amounts pale into insignificance compared with creation from 14N in upper atmosphere under influence of cosmic radiation • ‘Massive’ problem for Germany because of apparently intractable limits on ‘releasable’ 14C in KONRAD (salt dome)...could be breached by just the reflector graphite from two prototype HTRs (AVR and THTR) Carbon-14

44. So why should 14C release be an issue? Locally, maybe.. Globally, NO! Carbon-14

45. Half-life 301,000 years (that’s not many Bequerels in anyone’s best estimate!!) • Feared because of capability to get into food chain after release to groundwater where transport is taken to be “at the speed of the water”... • ...but that assumes it is in the form of chloride ions. The best available evidence says that very little (if any) is in the form of chloride ions and almost all is in the form or covalently-bonded “organic” chlorine – which is much less of a ‘hazard’ • ...regulators have seized upon this illogical chain of issues and some countries, especially France, are paralysed in their efforts over i-graphite by ‘fear’ of 36Cl... • Germany will use salt dome such that 36Cl will be stabilised (“dilute and contain”), so do not concern themselves about this isotope (but this ‘strategy’ really only works if chemical forms are the same (i.e. Chloride, which it isn’t...) • UK (NDA) has decided to ‘fear’ both 36Cl and 14C! (Best British tradition of ‘belt and braces’ and dither, whatever the cost...) Chlorine-36

46. Major Players in Weak β-Emitters • IPNL, France (on behalf of EdF, CEA, ANDRA): speciation and location of 3H and 36Cl • Idaho State University: formation and behaviour of 14C within graphite structures, including investigations of production routes 13C(n,γ)14C versus14N(n,p)14C using N-loaded precursors and sophisticated analysis of resulting surface groups and structures... ... new phenomenon of N-‘fixing’ on graphite-pore surfaces identified! (May explain why predictions of the relative contributions from the two routes may be inaccurate)

47. N cluster N cluster (Courtesy ISU)

48. Poco 50000 x Poco 1500 x • Nitrogen clusters preferentially nucleate at edges and activation sites SEM Nitrogen Nucleation NBG-18 35000 x Courtesy ISU

49. “An emerging consensus concludes that current regulations for radiation exposure are not only ‘based in quicksand’ but have become pernicious obstacles to the ethical goal that they purport to achieve: public health protection.... it is ethically disastrous to claim that the LNT hypothesis is an unassailable scientific conclusion, when in fact it is only an inconclusive theory, an extrapolated hypothesis, an ultraconservative exercise of prudence... Fear of radiation has proved to be far more detrimental to public health than radiation itself.... “Moreover, billions of dollars have been spent on trivial radiation risks based upon grotesque scenarios about single atoms destined to migrate through miles of desert soil to contaminate a potential water source in some distant future.” Dr. Margaret Maxey (Bio-ethicist, University of Detroit)

50. Pyrolysis – Steam Reforming • Utilise simple chemical oxidation reaction C + H2O = CO + H2 Endothermic, therefore can be kept well under control, but does need rather large input of energy IPR lies with Studsvik, who developed a similar process for disposal of radioactive resin materials in their former plant at Erwin, Tennessee Selected innovations This is the basis of the integrated gasification – sequestration process described earlier