R. Pampin EURATOM/UKAEA Fusion Association

1. TW5-TSW-001&002 final meeting Culham Science Centre, October 2006 Study on recycling of fusion activated materials:Identify activation levels and decay time requirements of irradiated material(deliverable 3) R. Pampin EURATOM/UKAEA Fusion Association

2. Background • European Fusion Programme strategy for fusion irradiated waste: • Release from regulatory control mildly activated material, usually lifetime, bulky, outer components: TFC, VV, LTS. • Recycle within the nuclear industry (fission/fusion) the rest. • PPCS radioactive waste results: all material cleared/recycled within 100 years, but: • Release criteria: out-of-date IAEA clearance levels (1996). • Lack of detail in the models (e.g. outer components). • Inadequate modelling of particular materials (e.g. LiPb). • Recycling criteria based on radiological parameters only, which were imprecise and over-conservative.

3. Background • IAEA 1996/2004 clearance levels: many changes affect fusion-relevant radionuclides (e.g. 30-fold decrease in Ni-63 level). • TW5-TSW-002 D1 report on implications, TW5-TSW-001 D3 report on specific effects on PPCS-AB.

4. Background • PPCS recycling criteria: some sensible for certain waste streams following certain routes (e.g. re-melting of steels); “complex recycling” limit is: (a) noticeably over-conservative and (b) uncertain: depends on route followed !

5. Scope and objectives • To review and update PPCS work using: • Up-to-date international clearance levels: IAEA 2004. • Up-to-date nuclear data: EAF 2005. • Practical feasibility criteria: findings of this task. • More accurate modelling methodology (e.g. LiPb flow) and increased level of detail (e.g. TFC and breeder materials). • With the aim of: • Determining more realistic amounts and activation features of the material inventory. • Identifying interim decay times required during recycling. • Identifying potential for (a) reduction of waste, and (b) simplification of processes.

6. Material inventory • PPCS-AB based on the HCLL blanket concept, PPCS-B based on the HCPB blanket concept.

7. Distinction between recycling and refurbishment: Refurbishment: little or no processing, on-site, immediate or early reuse in the fusion plant (e.g. LiPb, ceramics). Recycling: greater processing, off-site, later reuse in the nuclear industry in general. Recycling strategies in the industry exist for: Very low activity: fabrication of simple components. Very high activity: de-activation and re-fabrication of internals. Recycling routes envisaged for all PPCS-AB and PPCS-B materials (TW5-TSW-001 B report). Industry experience

8. Radiological levels • Use radiological levels to ascertain storage times needed for the activity to decay to levels facilitating recycling processes: • Clearance: C.I. • Lower RH needs: contact dose rate. • Lower cooling needs: decay heat rate. • Easier transport: ?

9. Computational tools and models

10. Results: clearance • New IAEA levels  increased amounts of material to be recycled: OB VV and IB TFC. • Time scales: few years OB, few decades IB. • Segregation alleviates this.

11. Results: refurbishment • Refurbishment of LiPb is possible and reduces considerably the amount of operational waste (from 124000 to 97000 tonnes). • PPCS-B ceramic breeder and other materials also possible, but much lower impact  strategic value?

12. Results: recycling • PPCS-AB results: • Ex-vessel: most materials, individually or as TFC, VV and LTS, show contact dose rates < 2 mSv/h (earlier OB than IB). • Ex-vessel: many of these show < 0.01 mSv/h after suitable decay time (few years OB, several decades IB). • In-vessel: poloidal variation is negligible. • In-vessel: all Eurofer and LTS neutron shield (WC) show contact dose rates < 2 mSv/h after ~75 years. • In-vessel: LiPb breeder and W armour still exceed 2 mSv/h after 100 years: Dominant nuclides arise from Pb and W isotopes, hence impurity control not very useful in this case!  isotopic separation needed.

13. Results: recycling - impurities • W and LiPb PPCS specifications contain many impurities: (a) manufacturer limits, (b) detection limits. Co, Ni, Nb, Mo, Eu, Sm, Gd, Tb, Pt, Ir, Pb, U, Th, Bi, Ag, Cd, Ba, Tl, Co, Nb

14. Results: recycling - impurities • PPCS-B results: • In-vessel: again, (nearly) all Eurofer and LTS neutron shield (ZrH) show < 2 mSv/h in ~75 years. • In-vessel: Li4SiO4, Be and W armour, however, do not meet this target  Li4SiO4and Be dose entirely due toimpurities: Co, Ni, Nb, Mo, Eu, Sm, Gd, Tb, Pt, Ir, Pb, U, Th, Bi, Ag, Cd, Ba, Tl, Co, Nb

15. Results: decay times

16. Summary • Upgrading PPCS work on PPCS-AB and PPCS-B radioactive waste analysis using recent regulations, new nuclear data, improved modelling and realistic recycling scenarios. • Assess clearance/refurbishment/recycling potential and interim decay times. • Results: • new IAEA levels increase amount of material to recycle; • clearance is achieved within few years (OB) or few decades (IB); • most recycling material below 2 mSv/h after ~75y of decay; • are these acceptable time scales?

17. Summary • Three key issues to optimise fusion recycling strategy by reducing amount of material, secondary wastes and/or radiological levels: • Segregation of materials • Refurbishment • Impurity control • Further work: • Shielding issues, particularly in PPCS-B • Transport requirements? • New categorisation? • Radioactivity build-up due to (a) impurities and (b) reuse. www.fourmilab.ch/earthscr/

18. Fusion materials strategy – open

19. Fusion materials strategy – closed

20. Fusion materials strategy: radiological levels and classification criteria? – simple transport RHR – complex transport