Structural Materials R&D for ITER Test Blanket Modules

1. Structural Materials R&D for ITER Test Blanket Modules R. J Kurtz1 and S. J. Zinkle2 1Pacific Northwest National Laboratory 2Oak Ridge National Laboratory ITER-TBM Meeting August 10-12, 2005 Idaho Falls, ID

2. Vacuum Permeator 2000 Nb or Ta Tubes Ri = 10 mm tw = 0.5 mm Pop < 1 MPa Pac ~ 8 MPa Cryo-Vacuum pump T2 outlet Blanket Concentric pipes 700°C PbLi 460°C PbLi Generator Closed Brayton Cycle Heat Exchanger Nb or Ta Tubes ~20,000 m2 Ri = 10 mm tw = 1.0 mm Pop = 8-10 MPa Pac = ? Pressure boundary (90°C) Power turbine Turbo-compressor PbLi pump He outlet He inlet Inter-cooler Pre-cooler Recuperator DCLL PbLi Flow Schematic PT2 in PbLi <0.03 Pa (outlet) PT2 in PbLi ~0.5 Pa (inlet)

3. Possible Project Structure and Organization • 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 • This places the emphasis on identifying the elements needed to deliver major pieces of equipment. • 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 • 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. As received 1040oCx2h HIPed 1150oCx0.5h Homogenized 200 Built-in Cooling Channels 300 Homogenizing +930oCx0.5h Homogenizing +940oCx0.5h Homogenizing +920oCx0.5h 100 mm F82H as recieved Grain Size # G：5 Grain Size：60mm 1040 ºC x 2hr x 150MPa Grain Size #G：2 Grain Size：170mm Fabrication Technology of Blanket Modules Akiba, TBWG-15, 2005 HIP and post HIP heat treatment conditions have been optimized.  HIP at 1150 ºC + PHHT at 930 ºC + Tempering

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

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. High-Temperature Design Rules • 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)

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

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

14. Irradiation Hardening and Ductility Loss Odette, 2002 Dsy Deu

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

16. F82H mod EUROFER 97 OPTIFER V MANET-I Effect of Alloying and Neutron Irradiation on the Charpy Impact Properties of F/M Steels 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 irradiation Effect of alloy composition

17. Structural Materials R&D Issues - III • 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. • 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 • 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. • 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. Material Contaminant Levels, wppm Reference O N C Nb ~3000 ~3000 <2100 Charlot and Westerman, 1974 V, Nb, Ta ~2000 ~4000 ~10,000 Ghoniem, 1998 V ~1500 Zinkle and Ghoniem, 2000 Nb-1Zr (Wrought) ~8000 Charlot and Westerman, 1974 Nb-1Zr (Weld) <4000 Charlot and Westerman, 1974 Mo-TZM ~300 Charlot and Westerman, 1974 Cr, Mo, W ~100 ~150 ~200 Ghoniem, 1998 Maximum Estimated Interstitial Levels for Various Refractory Metals

20. Structural Materials R&D Issues - IV • 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 • 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? • 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. • Considerable R&D on refractory metals is needed to determine if the high-performance DCLL concept is viable. • 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.