1. Materials – Status Report TAC-10 Yongjoong Lee Group Leader – Materials Target Division www.europeanspallationsource.se November 5, 2014

2. Materials WBS Materials Management Materials Database and Engineering Support Irradiated Materials R&D Spallation Materials Moderator Reflector Structural Materials Proton Beam Window Materials Materials R&D Infrastructure Materials Chemistry Ortho-Para Conversion Future Moderator Materials 2

3. Materials Collaborations 3 ESS: Materials PSI PIE of STIP Specimen RaDIATE Collaboratio n LTH Metallurgy and Solid Mechanics

4. Components receiving high dose Target wheel – Spallation material – Target vessel Moderator-reflector system – Aluminum structures – Beryllium reflector Proton beam window 4

5. Spallation Material Pure tungsten – Lower DBTT than W-10%Re for DPA > 0.3 [H. Ullmaier, F. Carsughi, NIM-B 101, 1995] – Higher thermal conductivity than other W-alloys [M. Rieth et al, Tech- Rep.-KIT] – Tantalum has a higher volumetric decay heat and lower neutron production density. 5

6. Spallation Material: Fatigue Tungsten undergoes a 100°C thermal cycle every 2.4 seconds (7·10 6 cycles per year) Fatigue: – Endurance limit: 137.5 Mpa [J. Habainy et al, IWSMT-12, 2014] – Recommended mean stress in the tungsten slab: 100 MPa – Recommended stress pulse amplitude: 50 MPa 6 plate 2 plate 7

7. Spallation Material: Oxidation 7 Oxidation observed in He atmosphere with small partial pressure of oxygen above 500°C [J. Habainy et al. IWSMT-12, 2014] Reactive vaporization of the hydrated oxide layer is observed in steam above 700°C [G. Greene, C. Frinfrock, Exp. Therm. Fluid Sci. 25 (2001)] Temperature limits: – 500°C for normal operation – 700°C for off-normal conditions (e.g., design basis accidents)

8. Spallation Materials: PIE A damage rate of 1.2 dpa/GW-d (1 GW-d equals the one year operation at 5 MW) in the ESS tungsten STIP-V: Two 60 x 8 x 1 mm^3 tungsten bars – Irradiation period: 2007-2008 for total 9.83 Ah p-charge. – Irradiation condition: 5-28 DPA at 100-800 C – Planned tests: Thermal conductivity and thermal expansion Bending tests, small punch tests, hardness tests, SEM and TEM – Milestones Start: 2015.06.30 Publication of the results: 2016.06.30 PIE of the STIP-VI and STIP-VII tungsten specimens in the plan. 8

9. Target Vessel: Materials Choice Primary choice: Stainless steel 316L(N) – Fracture mode is still ductile up to 17 DPA – Operational experiences at SNS and ISIS – The DBTT of BCC-steel (e.g. T91) increases with dpa. Candidate Material: SA- Inconel 718 – Operational experience at LANSCE, ISIS, SNS – Solution annealed alloy 718 shows a good ductility to 18 dpa 9 Y. Dai, et al., JNM 377 (2008) 109

10. Target Vessel: Lifetime estimates A maximum damage rate of 1.4 dpa/GW-d in the beam entrance window of the ESS target. – Lifetime limit guide: 10 dpa of accumulated dose: SNS – The nominal lifetime of the target wheel limited by the radiation damage of the target vessel is 7 years. – Thermal fatigue might impose more conservative lifetime limits 10

11. Moderator-Reflector Canisters: Materials Choice Primary choice: Al-6061- T6: – Used by SNS, J-PARC, LANSCE – Higher strength and radiation resistance Candidate Material: Al- 5XXX – Used by ISIS, PSI – Better welding properties 11

12. Moderator Canister: Lifetime Estimates Lifetime limit guide: – Thermal neutron flux and silicon transmutation – DPA limit for HFIR: 40 dpa 12 Maximum production rates Al@20KAl@300K H (appm/GW-d) 7751067 He (appm/GW-d) 195310 Si (a%/GW-d) 0.850.25 Displacement rate (dpa/GW-d) 9.328.8 Thermal neutron fluence (n/cm 2 /GW-d) 2.4×10 22 1.2×10 22 Proposed MR-plug lifetime: One operational year with total proton energy of 1.0 GW-d.

13. Moderator Canister: PIE-Prospect ISIS-TS1 LH-moderator – Collaboration of ISIS, PSI and ESS – Al-5083 20 years of irradiation Nominal O(100) uA beam current Dose roughly equivalent to O(1) GW-d Milestones - Preliminary – Plan: 2015.03.31 – Approval: 2015.06.30 – Publication of the results: 2016.12.31 13

14. Reflector: Beryllium swelling and hydrogen reaction Swelling rate is correlated to helium production rate [ITER-EDA, ITER materials properties handbook (1998)] 14

15. Reflector: Beryllium swelling and hydrogen reaction Peak heat load: 5.9 W/cm 3 Peak He production rate = 520 appm/GW-d – It takes more than 10 years to reach the maximum 1% volumetric swelling. Peak displacement rate = 1.3 dpa/GW-d – Beryllium is non-structural Beryllium steam reaction: – Be + H 2 O -> BeO + H 2 + 370 kJ/mol – Below 600 C, the hydrogen production rate and the associated exothermic heat generation are manageable. 15

16. Proton Beam Window: Materials Choice Baseline: Al-6061-T6 – No proton irradiation data – SNS plans Al-6061-T6 for the near-future proton beam window installations Candidate Materials: – AlMg3: PSI experience with AlMg3 safety hull (SINQ Target 9) taken to 2000 He-appm and 7 dpa, with peak temperature in the window 60 C. The PBW#2 at JSNS is made of AlMg3 and awaiting PIE in 2014, which has been irradiated 2.0 GW-h (~0.08 GW-d) of accumulated beam power. – Inconel 718: Experiences at LANSCE and SNS 16

17. Proton Beam Window: Lifetime estimates Lifetime limit guide: 2000 appm helium production – Nominally adopting this limit implies a PBW lifetime of 0.5 GW-d. PIE Prospect: – The PIE of AlMg3 window of SINQ in 2015. – The PIE of STIP-VII Al- 6061 specimen in 2017. 17 QuantityPBW H production rate (appm/GW-d) 22000 He production rate (appm/GW-d) 3900 Displacement rate (dpa/GW-d) 7.1 Volumetric heating (W/cm 3 ) 510

18. Summary The materials activities for the ESS target project are based on well-founded and being-explored collaborations: – Short Term: Engineering materials support and database management. – Mid Term: PIE of irradiated materials of high-dose components of target station. – Long Term: Feasibility study for materials research infrastructure and future moderator materials. The lifetimes of the high-dose target station components are reasoned based on existing irradiation data: – Target Wheel: 7 GW-d – Moderator Canisters: 1 GW-d – Proton Beam Window: 0.5 GW-d – Beryllium: 10 GW-d 18