U.S. Department of EnergyPacific Northwest National Laboratory

Structural Materials R&D for ITER Test Blanket Modules

R. J Kurtz1 and S. J. Zinkle2

1Pacific Northwest National Laboratory2Oak Ridge National Laboratory

ITER-TBM MeetingAugust 10-12, 2005Idaho Falls, ID

DCLL PbLi Flow Schematic

He inletHe outlet

PbLipump

Cryo-Vacuum pumpVacuum Permeator2000 Nb or Ta Tubes

Ri = 10 mmtw = 0.5 mmPop < 1 MPaPac ~ 8 MPa

BlanketConcentric pipes

Heat ExchangerNb or Ta Tubes

~20,000 m2

Ri = 10 mmtw = 1.0 mm

Pop = 8-10 MPaPac = ?

T2 outlet

Inter-cooler Pre-cooler Recuperator

Pressure boundary (90°C)

Generator

Turbo-compressorPower turbine

Closed Brayton Cycle

700°C PbLi

460°C PbLiPT2 in PbLi ~0.5 Pa (inlet)

PT2 in PbLi <0.03 Pa (outlet)

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.

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.

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 1040oCx2hHIPed

1150oCx0.5hHomogenized

Homogenizing+920oCx0.5h

Homogenizing+930oCx0.5h

Homogenizing+940oCx0.5h

100 m

Fabrication Technology of Blanket Modules

F82H as recievedGrain Size # G ： 5Grain Size ： 60m

1040 ºC x 2hr x 150MPa Grain Size #G ： 2Grain Size ： 170m

Akiba, TBWG-15, 2005

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

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

Effect of Hardening on Stress Corrosion Cracking

S.A. Shipilov, JOM (March 2005) p. 36

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

Analysis

Results

Assessment

Benefit

Structural Analysis Tool: Finite Element Analysis

Prospects andLimitations

Evaluate Loading HistoriesTemperature Fields

Stress and Strain Fields

Identify CriticalLoads

Input for Mock-Up Tests Design and Operation

Development and Improvementof Concepts

Define Loads for Verification Expts and

Analysis

Identify CriticalLocations

Close Coupling of Structural Analysis and Materials Development is Essential

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.

Low Temperature Radiation Hardening of RAFM Steels

Robertson et al.

(a)

(b)

0

200

400

600

800

1000

0 5 10 15 20 25 30

F82H IEA Std.

Engineering Strain (%)

Irrad. at 573K

Tested at RT

Irrad. 773K

Tested at RT

Irrad. 773K

Tested at 773K

Irrad. at 573K

Tested at 573K

0

200

400

600

800

1000

0 5 10 15 20 25 30

F82H IEA TIG

Engineering Strain (%)

Irrad. at 573K

Tested at RT

Irrad. at 573K

Tested at 573K

Irrad. at 773K

Tested at 773K

Irrad. at 773K

Tested at RT

Fig. 1 Stress-strain curves of F82H BM (a) and TIG (b) irradiated at 573K and 773K in tests at RT

F82H BM

F82H TIG

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

500nm100nm

110

Irradiated weld metal (lower radiation hardening) did notexhibit dislocation channeling after deformation

5 dpa

5 dpa

F82H base metal

F82H TIG weld

Deformation Microstructures in Neutron-Irradiated F82H Base and Weld Metal

y

eu

Irradiation Hardening and Ductility Loss

Odette, 2002

Temperature and Dose Dependence of Fracture Toughness for F82H and Eurofer

Sokolov, 2000

Andreani et al., JNM 2004

0

2

4

6

8

10

12

-150 -100 -50 0 50 100

Test Temperature [°C]

Energy [J]

MANET-I

F82H modEUROFER 97

OPTIFER V

0

2

4

6

8

10

12

-200 -100 0 100 200 300 400 500

Test Temperature [°C]

Energy [J]

MANET-I

300°C/2.4 dpa

OPTIFER V

300°C/2.4 dpa

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

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.

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.

10-1

100

101

102

103

104

105

106

10-12 10-11 10-10 10-9 10-8 10-7 10-6

Oxygen Partial Pressure, torr

1000 h

1 y

10 y

Assumes 3 mm wall thickness and oxygen ingress from one surface only

€

Γ=P

2πmkT( )1

2

T = 700°C

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<2100~3000~3000Nb

ReferenceCNOMaterial

Contaminant Levels, wppm

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.

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.