u.s. background in iter fueling systems and future...

OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY

U.S. BACKGROUND IN ITER FUELING SYSTEMSAND FUTURE CONTRIBUTIONS

S.K. Combs,1 L.R. Baylor,1 B.E. Chapman,2 P.W. Fisher,1 M.J. Gouge,1M. Greenwald,3 T.J. Jernigan,1 W.A. Houlberg,1 P.B. Parks,4

J.M. Pfotenhauer,2 G.L. Schmidt,5 and D.A. Rasmussen1

1Oak Ridge National Laboratory2University of Wisconsin

3Massachusetts Institute of Technology4General Atomics

5Princeton Plasma Physics Laboratory

U.S. ITER FORUMMay 8-9, 2003

University of Maryland University CollegeAldelphi, Maryland USA

2OAK RIDGE NATIONAL LABORATORYU.S. DEPARTMENT OF ENERGY

Outline

• Brief description of ITER fueling system and schedule

• Why pellet fueling is crucial for ITER

• Background of U.S. in fueling R&D and experiments

• Contributions of U.S. during ITER CDA and EDA

• New technical challenges

• Benefits to U.S. Fusion Program

• Summary


ITER Fueling Systems Requirements and Present Design

Up to 3000Pulse length (s)

750 (375 for 90%T/10%D)Pellet Fueling Rate (torr-L/s)

Up to 3000Gas Fueling Rate (torr-L/s)

UnknownDT Burn Rate

Pellet (90%T/10%D)Fuel Isotope

0.4 - 1Plasma Density(nGW)

• Gas injection system– Supplies H2, D2, T2, DT, Ar, Ne, and He via a gas manifold– Makes use of conventional gas handling hardware and requires minimal R&D

• Pellet injection system– Supplies H2, D2, and DT pellets: 3 to 6 mm diam (50 to 7 Hz, respectively)– Only at pre-conceptual design level and significant R&D support still needed


ITER Fueling System Diagram and Pellet Injection System Design Criteria

Pellet Injection System

• Two centrifuge injectors forredundancy (also supportscoincident impurity injection)

• Steady-state operation

• Screw extruders for pelletproduction and supply

• Each injector assembly housed incask (~6 m L x 4 m H x 3 m W)

• Pellets delivered through singleguide tube connected through adivertor port to plasma chamber

• Includes a diagnostic/control anddata acquisition system


1 2 3 4 5 6 7 8 92005 2006 2007 2008 2009 2010 2011 2012 2013

DesignConceptual DesignPrelim. DesignPDRFinal DesignFDR

Direct R&DExtruder MockupCentrifuge rotor prototypeGuide/Capture tube prototype

FabricationLet contractsFabricate injector partsAssemble injectorLaboratory TestReady to install on ITER

Tentative Schedule & Cost for ITER Pellet Injector

• Costs shown are recent U.S. estimates and have lots of assumptions– Costs are if U.S. does it all, but this could be an international

collaborate effort• R&D will have general benefits to U.S.


Pellet Injection Will Be Crucial for Effective Core Fueling in ITER as Shown inFueling Source Profile Comparison with DIII-D (Gas and Pellets in H-mode)

r0.0 0.2 0.4 0.6 0.8 1.0

1

10

100

1000

HFS PelletLFS PelletV+1 PelletRecycle Gas

D+ 1

019 m

-3 s

-1

0.0 0.2 0.4 0.6 0.8 1.00.001

0.01

0.1

1

10

100

1000

HFS PelletLFS PelletGas

r

DIII-D ITER

• Gas puff fueling in ITER will be much less effective in core fueling thanin DIII-D; the pellet profiles are from PRL (P. Parks) calculations usinga 10-mm pellet extrapolated to 1 Hz operation; a gas fueling rate of~1000 torr-L/s is used in the ITER case using a B2-Eirene slabcalculation (L. Owen and A. Kukushkin)

Gas FuelingEfficiency< 1%


U.S. DOE Office of Fusion Energy Science Has Sponsored Plasma Fueling R&DProgram for Over 25 Years – Developing Technology for Fusion Experiments


Pellet Sizes Tested in U.S. Program Are Relevant for Fueling Applications onAny Present Experimental Fusion Device and Future Fusion Reactors


• Three-barrel repeating pneumaticinjector (machine gun like)

• Straight guide tubes (≈4 m)

– Three independent standard low-field-side(LFS) injection tubes: 135º port

• Curved guide tubes (≈12.5 m)

– Two independent vertical injection tubes:0º (V+3) and 60º (V+1) ports

– Two independent HFS injection tubes oninner wall: 45º upper and lower ports

• Great flexibility in injection ports andrange of possible experiments

DIII-D Pellet Injection System Developed/Supported in the U.S. FuelingProgram and Used to Study Improved Mass Deposition with HFS Injection

Massive gas puff system for disruption mitigation studies has been developed andsuccessfully tested on DIII-D, and this technique appears scalable to ITER and isclosely related to the fueling system


During the ITER CDA and EDA (1989 – 1998), the U.S. WasResponsible for ITER Fueling System Design and R&D

• Technology Highlights

– Tritium injector design and testing with ITER-size (up to 8 mm) DT and Tpellets and cumulative T amounts of a few 10s of grams

– Development of innovative high-field-side launch technology andexperiments (experimental studies for DIII-D, JET, LHD, and FIRE)

– Demonstration of high-throughput/steady-state hydrogen ice supplyapproaching the full ITER pellet fueling design value

• Physics Highlights (Supported by U.S. Theory Program)

– Developed isotopic tailoring concept with DT pellets – key to operating ITERwith minimal tritium inventory (Gouge et al.)

– Significant progress on international pellet injection database to betterunderstand the physics of pellet penetration and ablation (Baylor et al.); thisis being extended to alternative injection locations as part of the ITPA effort

Russian Federation (R.F.) is the other ITER participant that has expressed stronginterest in the pellet fueling subsystem, and an arrangement where responsibilitywould be shared between the U.S. and R.F. is an option


In Tritium Pellet Experiments at TSTA, U.S. Obtained Unique Data andExperience with T2 & DT Directly Relevant for ITER Design and Operations

TritiumExtrusion(≈8 mm)


New Technical Challenges• Systems must be able to operate reliably in tritium environment and be

readily maintained

• Throughput requirements are significantly greater than achieved inexperiments to date

– Continuous screw extruders (I. Viniar, R.F.) are assumed in the ITERbaseline design, but these have only achieved flow rates that are afactor of ~5-10 lower than that required

– Highest ice flow rates to date (~67% of ITER design value) wereachieved at ORNL using a prototype with three large volume extrudersoperating in sequence (Combs et al.)

• Centrifuges in the ITER design have not achieved the overall reliabilityobjective (~100% intact pellets); pneumatic injectors can more easily meetreliability requirements, but have a gas load issue

• Significant R&D effort still required before final design; development andtesting program will be needed to validate proposed ITER pellet injectordesign and to modify it as needed

• Evolution of the system may permit new technologies such as supersonicgas jet, high-speed vertical injector, and inner bore injector


Benefits to the U.S. Fusion Program

• U.S. has been recognized as world leader in pellet fueling fordecades, and key role in ITER fueling activity would help maintainR&D capabilities in this unique scientific field/technology

• Lead to improved fueling systems for present and planned U.S.experiments

• Result in better understanding of the details of fueling physics

• Increased international collaboration opportunities (e. g., on JETand DIII-D) for testing of advanced or prototypical pellet injectors

• Major U.S. participation in fueling physics experiments on ITERwill be much more likely if the U.S. is responsible for the fuelingsystem

• Increased opportunities for graduate students; for example,collaboration with J.M. Pfotenhauer at University of Wisconsin onadvanced cryogenic cooling systems for pellet injectors


SUMMARY

• U.S. had the lead role in ITER fueling during the CDA and EDA and isin an excellent position to resume that role, with a particularly stronginterest in the pellet fueling system

• U.S. has the proven capability to develop, design, and construct theentire ITER fueling system as a turnkey item

• U.S. could share responsibility for ITER fueling with R.F. and possiblyother international collaborators

• ITER fueling tasks will be relatively low cost compared to other majorsystems, and U.S. can realize a fairly low cost/benefit ratio

Success of ITER relies largely on the ability to operate the plasma athigh density with good confinement; pellet fueling is the primarymechanism to provide the necessary deep fueling

u.s. background in iter fueling systems and future...

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