1. U.S. Department of Energy Pacific Northwest National Laboratory Structural Materials R&D for ITER Test Blanket Modules R. J Kurtz 1 and S. J. Zinkle 2 1 Pacific Northwest National Laboratory 2 Oak Ridge National Laboratory ITER-TBM Meeting August 10-12, 2005 Idaho Falls, ID

2. DCLL PbLi Flow Schematic He inletHe outlet PbLi pump Cryo-Vacuum pump Vacuum Permeator 2000 Nb or Ta Tubes R i = 10 mm t w = 0.5 mm P op < 1 MPa P ac ~ 8 MPa Blanket Concentric pipes Heat Exchanger Nb or Ta Tubes ~20,000 m 2 R i = 10 mm t w = 1.0 mm P op = 8-10 MPa P ac = ? T 2 outlet Inter-coolerPre-coolerRecuperator Pressure boundary (90°C) Generator Turbo-compressor Power turbine Closed Brayton Cycle 700°C PbLi 460°C PbLi P T 2 in PbLi ~0.5 Pa (inlet) P T 2 in PbLi <0.03 Pa (outlet)

3. Possible Project Structure and Organization n Test Blanket Module (both HCSB and DCLL) R&D, fabrication, testing and qualification should be broken down into major subsystems (e.g.): In-vessel TBM Ex-vessel piping Tritium extraction system Heat exchanger system n This places the emphasis on identifying the elements needed to deliver major pieces of equipment. n Each subsystem then has an appropriate set of tasks designed to address the needs for that particular subsystem.

4. Structural Materials R&D Issues - I n In-Vessel TBM Structural materials will need to be code qualified which places stringent requirements on materials characterization and generation of an engineering database for design activities and licensing. Fabrication techniques must consider the possible need for thermo-mechanical treatments that will affect final microstructure and possibly impact in-service properties. Fabrication methods must also allow for possible pre-service and in-service nondestructive inspection. Given detailed design specifications TBM fabrication is an activity best accomplished by industry. High-temperature design rules need to be developed.

5. 300 200 Built-in Cooling Channels HIP and post HIP heat treatment conditions have been optimized.  HIP at 1150 ºC + PHHT at 930 ºC + Tempering As received 1040 o Cx2h HIPed 1150 o Cx0.5h Homogenized Homogenizing +920 o Cx0.5h Homogenizing +930 o Cx0.5h Homogenizing +940 o Cx0.5h 100  m Fabrication Technology of Blanket Modules F82H as recieved Grain Size # G ： 5 Grain Size ： 60  m 1040 ºC x 2hr x 150MPa Grain Size #G ： 2 Grain Size ： 170  m Akiba, TBWG-15, 2005

6. R.L. Klueh and D.R. Harries, High-Chromium Ferritic and Martensitic Steels for Nuclear Applications (2001) p. 73 As-welded After post weld heat treatment Effect of Heat Treatment on the Hardness Profile in a GTA Weld in a F/M Steel

7. Time-Temperature Transformation Curve for F82H Steel R.L. Klueh and D.R. Harries, High-Chromium Ferritic and Martensitic Steels for Nuclear Applications (2001) p. 33

8. Effect of Hardening on Stress Corrosion Cracking S.A. Shipilov, JOM (March 2005) p. 36

9.  Extend rules to all joining techniques and typical junctions foreseen in TBM concepts.  Extend rules to composites and multi-layers structures and materials with low ductility and pronounced anisotropy.  Application to complex loading and loading histories with multiple potential failure modes, in the presence of:  Multiaxial loading  Stress and temperature gradients  Interaction of thermal creep and fatigue with irradiation damage (swelling and irradiation creep) High-Temperature Design Rules

10. Analysis Results Assessment Benefit Structural Analysis Tool: Finite Element Analysis Prospects and Limitations Evaluate Loading Histories Temperature Fields Stress and Strain Fields Identify Critical Loads Input for Mock-Up Tests Design and Operation Development and Improvement of Concepts Define Loads for Verification Expts and Analysis Identify Critical Locations Close Coupling of Structural Analysis and Materials Development is Essential

11. Structural Materials R&D Issues - II n In-Vessel TBM For ITER the choice of structural material is limited to F82H and Eurofer since the U.S. needs to take advantage of the large international database on these steels. Development of joining technology of Be to ferritic steel (structural materials issue?). Effects of radiation to ~3 dpa at 100-550°C on the deformation and fracture properties of structural materials. The upcoming U.S./Japan HFIR 15J/16J irradiation experiment provides a good approximation of the TBM irradiation conditions (300/400°C, 2.5-5 dpa). New heat of Eurofer to be included. The irradiation performance of specific manufacturing processes and joining techniques such as HIPped and diffusion bonded materials needs to be determined (presently not nuclear qualified). Creep-fatigue interaction due to the high number of short operational pulses in ITER is a concern.

12. Low Temperature Radiation Hardening of RAFM Steels Robertson et al.

13. Slip plane: (110) and (011) Slip direction: [111] and [111] Dislocation channels Deformation band N. Hashimoto et al., Fus.Sci.Tech. 44 (2003)490 B ≈ [111] g = 110 110 500nm 100nm 110 Irradiated weld metal (lower radiation hardening) did not exhibit dislocation channeling after deformation 5 dpa F82H base metal F82H TIG weld Deformation Microstructures in Neutron- Irradiated F82H Base and Weld Metal

14.  y eueu Irradiation Hardening and Ductility Loss Odette, 2002

15. Temperature and Dose Dependence of Fracture Toughness for F82H and Eurofer Sokolov, 2000 Andreani et al., JNM 2004

16. MANET-I F82H mod EUROFER 97 OPTIFER V Effect of alloy composition Effect of irradiation In contrast to conventional FM steels (MANET-I), RAFM steels show favourable toughness and embrittlement properties R. Lindau et al., SOFT23, Fus. Eng. Des. (2005) in press Effect of Alloying and Neutron Irradiation on the Charpy Impact Properties of F/M Steels

17. Structural Materials R&D Issues - III n Ex-Vessel Piping Chemical compatibility of structural materials with PbLi to ~700°C. Aluminum bearing corrosion resistant alloys show promise of forming a protective alumina surface layer, lowering corrosion in PbLi. A critical need is to carry out tests in a PbLi loop with thermal gradients. n Tritium Extraction System To achieve high performance from DCLL concept may require use of refractory metals. The acceptable inventory of gaseous impurities and the kinetics of impurity pickup control mechanical behavior of these metals. The partial pressure of oxygen must be <10 -10 torr to limit unacceptable oxygen ingress. The compatibility of refractory metals with flowing, 700°C PbLi has not been demonstrated.

18. Kinetics of Oxygen Pickup in Nb n The observed oxygen concentration can be significantly lower than thermal equilibrium values. Protective scale formation (generally does not occur in refractory metals at high temperature and low oxygen partial pressure). Application of protective coating (e.g., Pd). The oxygen impingement flux is directly proportional to the oxygen partial pressure. n The oxygen pressure limit can be derived from the impingement flux and a limiting oxygen concentration in Nb. Assumes 3 mm wall thickness and oxygen ingress from one surface only T = 700°C

19. Maximum Estimated Interstitial Levels for Various Refractory Metals Ghoniem, 1998~200~150~100Cr, Mo, W Charlot and Westerman, 1974~300Mo-TZM Charlot and Westerman, 1974<4000Nb-1Zr (Weld) Charlot and Westerman, 1974~8000Nb-1Zr (Wrought) Zinkle and Ghoniem, 2000~1500V Ghoniem, 1998~10,000~4000~2000V, Nb, Ta Charlot and Westerman, 1974<2100~3000 Nb Reference CNO Material Contaminant Levels, wppm

20. Structural Materials R&D Issues - IV n Heat Exchanger System Refractory metals are also under consideration for the heat exchanger system. Impurity inventory in the He coolant largely controls the rate of impurity pickup (other sources from adsorbed gases and in- leakage may be important). To avoid excessive impurity ingress the He coolant must be highly purified. The level of purification needed will be dictated by the mass of He relative to the mass of refractory metal tubing and component outgassing. Other factors such as fabricability, weldability, fracture toughness, cost and the potential for dissimilar metal corrosion (refractory to ferritic steel transition) needs be considered in evaluating the feasibility of using refractory metals in these applications.

21. Comments n Will the lower performance DCLL TBM envisaged for ITER be sufficiently attractive to justify the expense for the U.S. to independently pursue this approach? n The advantages of the lower performance DCLL option relative to other liquid breeder concepts being developed for ITER needs to be highlighted in the mission needs statement. n Considerable R&D on refractory metals is needed to determine if the high-performance DCLL concept is viable. n If the low-performance DCLL concept is sufficiently attractive then the most cost-effective approach for structural materials development is to make maximal use of ongoing work in the EU and Japan - provided the design and operating conditions are not too different.