Presented by

Scott Willms (LANL)

Harnessing Fusion Power Workshop

UCLA

March 2, 2009

Renew Fuel Cycle Panel

Fuel Cycle Panel Members

– Scott Willms (LANL)– Jim Klein (SRNL)– Alice Ying (UCLA)– Larry Baylor (ORNL)– Martin Peng (ORNL)– Dai-Kai Sze (UCSD)

Approach: Tie Fuel Cycle back to original Greenwald questions

1. “What R&D thrusts are needed to build DEMO.”

1.1 “What is needed to be able to properly supply and handle tritium for DEMO?”

1.1 How do we close the fusion fuel cycle?

Seven sub-questions

Q 1-4

• 1.1.1 What is needed to adequately process fusion fuel for DEMO?

• 1.1.2 What is needed to provide torus vacuum and fueling for DEMO?

• 1.1.3 What is needed to adequately contain and handle tritium for DEMO?

• 1.1.4 What is needed to adequately perform tritium accountability and nuclear facility operations for DEMO?

Q 5-7

• 1.1.5 What is needed to breed tritium for DEMO?

• 1.1.6 What is needed to extract tritium from the breeding system for DEMO?

• 1.1.7 What is needed to characterize, recover and handle in-vessel tritium for DEMO?

Backdrop

State-of-the-art6 liters/minTime requirement 24 hr100 gm inventoryDuty cycle: 15%“Power”: 1000 MW

Need for ITER120 liters/minTime requirement 1 hr4000 gm inventoryDuty cycle: 5%Power: 400 MW

DEMO

Need for DEMO500 liters/min?Time requirement 1 hr6000 gm inventoryDuty cycle: 50%Power: 2000 MW

Detail under each question

1.1.1 What is needed to adequately process fusion fuel for DEMO?

• Fuel cleanup• Isotope separation• Tritium storage and delivery• Water detritiation• Tritium pumping• Effluent detritiation

Process

Glovebox

Air• Gas analysis• Process control

1.1.2 What is needed to provide torus vacuum and fueling for DEMO?

• Torus Vacuum pumps • Roughing pumps• Gas puffing• Pellet fueling• Disruption mitigation• ELM pacing

Snail pump under test at LANL.

1.1.3 What is needed to adequately contain and handle tritium for DEMO?

• Primary, secondary and tertiary containment 

• Permeation barriers• Occupational and environmental

tritium monitoring• Maintenance systems• Waste handling, characterization and

processing• Decontamination and

decommissioning• Personnel protection equipment

1.1.4 What is needed to adequately perform tritium accountability and nuclear facility operations for DEMO?

• Tritium accountability measurement techniques 

• Tritium accountability methodology and procedures

• Non-Proliferation approaches• Systems and approaches to ensure

worker and public safety (authorization basis)

• Tritium transportation technology and approaches

• Waste repository• Tritium supply

1.1.5 What is needed to breed tritium for DEMO?

• Tritium breeding blanket materials and configurations• Blanket structural materials• Blanket operations and control• Blanket maintenance and disposal• Blanket diagnostics

0.6 – 0.8 mm Li2TiO3 pebbles (CEA)0.2- 0.4 mm Li4SiO4 pebbles (FZK)

1.1.6 What is needed to extract tritium from the breeding system for DEMO?

• Tritium extraction from breeding materials• Tritium extraction from blanket coolants• Tritium extraction diagnostics• Blanket systems tritium handling and containment

1.1.7 What is needed to characterize, recover and handle in-vessel tritium for DEMO?

• In-vessel tritium characterization• In-vessel tritium control and removal• In-vessel component waste handling• Mitigation of in-vessel off-normal

effects on tritium systems

Backdrop

State-of-the-art6 liters/minTime requirement 24 hr100 gm inventoryDuty cycle: 15%“Power”: 1000 MW

Need for ITER120 liters/minTime requirement 1 hr4000 gm inventoryDuty cycle: 5%Power: 400 MW

DEMO

Need for DEMO500 liters/min?Time requirement 1 hr6000 gm inventoryDuty cycle: 50%Power: 2000 MW

1.1.1 Process Fusion Fuel

State-of-the-Art

• Systems developed at TSTA, JAERI, FzK, JET, SRNL, TFTR, Chalk River and other facilities define the state-of-the-art. These systems were typically tested at 1/20th scale (or less) of ITER.

• ITER will be a major technological challenge and much will be learned from ITER. The ITER tritium systems will largely be a production system with little opportunity for experimentation.

• DEMO will higher throughput (4x ITER) and duty factor (10x ITER)

Gaps

• Fuel Cleanup: Technology improvement• Isotope Separation: Tritium inventory and technology improvement• Tritium Storage and Delivery: Technology and assaying

improvement• Water Detritiation: Technology improvement. Need low-level

tritiated water processing system.• Pumping: Need larger capacity pumps• Effluent Detritiation: Would benefit from system which does not

produce water• Gas Analysis: Technology improvement• Process Control: Duty cycle and flowrate will require better control• Modeling: Accurate, easy-to-use models will be essential

1.2 Provide vacuum and fueling

Torus Vacuum Pumping

• Function: The torus vacuum pumping must maintain low divertor pressure (~10 Pa) while removing helium ash that will be generated by the fusion burn.

• State-of-the-art: The pumping system for ITER consists of 8 cryosorption pumps that are regenerated every 5 minutes in a cyclic fashion. These pumps are backed by tritium compatible roughing pumps (still under development). Frequent regeneration will be challenging.

• DEMO requirements: 4x ITER on flowrate and 10x on duty cycle.

• Gaps: Roughing pumps and torus cryopumps. Pumps that separate species have advantages.

21

Fueling

• Function: The fueling system must provide DT fuel to the burning plasma and also provide gas to the SOL and divertor to minimize impurity generation and sweep impurities to the divertor.

• State-of-the-art: The pellet fueling system for ITER will be the state-of-the art.

• DEMO requirements: 4x ITER on flowrate and 10x on duty cycle. Pellet penetration requirement may be increased.

• Gaps: TBD based on fueling penetration requirements, feed rate, tokamak/not tokamak, etc.

22State-of-the-art pellet injector

Disruption and ELM Mitigation

• Function: Provide massive gas injection(?) for disruption mitigation and rapid small pellets for ELM pacing

• State-of-the-art:

– For disruption mitigation gas jets.

– ELM mitigation with pellet pacing is not well developed at all. The next few years will hopefully answer the question of whether or not this could be employed.

• DEMO Requirements: The requirements for disruption and ELM mitigation in DEMO are completely unknown at this point. These requirements could have a significant effect on the fueling and pumping systems as well as the overall fuel cycle design.

• Gaps: TBD at this point

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1.1.3 Contain and handle tritium

Tritium containment and handling

• State-of-the-art: Experience at recent tritium facilities. ITER will be challenged in this area.

• Demo requirement: Operation of high-temperature machine with useful power extraction and high duty factor.

• Gaps– Control of tritium through non-traditional equipment (heat

exchangers; large, high-temperature components; long high-temperature pipe runs)

– Primary, secondary and tertiary containment . Room processing systems.

– Permeation barrier would help (but development has not been successful, and the barrier factor degrades under irradiation)

1.1.4 Tritium accountability and nuclear facility operations

Tritium Accountability Measurements

• State-of-the-Art– Dedicated/custom calorimeters: ± 0.25% in 6-8 hours

– P-V-T-Composition tank measurements: 2% or less

– In-bed accountability: 1-2% of full bed inventory

• Demo Requirements– Accuracy of ± 2 grams T2 out of “kilograms being processed”

• Gaps– ITER “inventory-by-difference” errors propagate quickly. Direct

methods of “estimating” tritium inventory need to be developed .

Tritium Accountability Methodology and Procedures. Non-Proliferation.

• State-of-the-Art– Periodic reconciliation between “book” inventory versus “physical”

inventory

– Attractiveness level defined by DOE Orders. Tritium is less attractive than special nuclear materials, but still requires safeguards

– “Gates, Guards, and Guns” with access restrictions

• Demo Requirements– Ensure no surreptitious diversion of tritium

• Gaps– Method to meet requirements (measurement or protection)

– Address political concerns

Tritium Safety (Authorization Basis/Licensing)

• State-of-the-Art– DOE, NRC, Fusion Safety Code and ITER requirements

– Risk-based assessments used for calculation of dose to the public

– “Agreements” made between contractors and DOE for chronic emission limits from facilities

• Demo Function/Requirements– Some type of licensing/regulations will be required

• Gaps– Agreement to arbitrarily “low” emission requirements may be cost

prohibitive for Demo

– Permits required for discharge above drinking water standard

Tritium Waste Disposal

• State-of-the-Art– (see Safety and Environmental presentation)

• Demo Function/Requirements– Some type of on-site or permitted disposal site will be needed

• Gaps– Assurance that fusion will not suffer from “Yucca Mountain

syndrome”

– Recycle option from “Safety and Environmental” presentation needs to include tritium recovery functionality in project scope

1.1.5 Breed tritium

Blanket HCPB (Solid Breeder) HCLL (Pb-17Li breeder)

Struct. material EUROFER EUROFER

Coolant He He

0per. pressure 8 MPa 8 MPa

T inlet-outlet 300-500°C 300-500°C

Breeder Pebble beds;Li4SiO4 [63% PF, 40% 6Li]Li2TiO3 [63% PF, 70% 6Li]

PbLi [90% 6Li]

Multiplier Pebble beds: Be [63% PF] -

Lifetime 7.5 MWa/m2 7.5 MWa/m2

T extraction from blanket

Low pressure (1bar)He purge loop

PbLi slowly re-circulatingat geodetic pressure

Operation mode Continuous (or altern. 1h-pulses)

Segmentation large modulesmax. dim. 2.0x2.0 m

Fusion / Electric Power 1800 / 750 MW

Net efficiency 40.5 %

Surface heating (av/peak) 0.4 / 0.5 MW/m2

Neutron wall load (av/peak) 2.0 / 2.4 MW/m2

EU DEMO Breeding Blankets Parameters

Blanket systems are complex and have many integrated functions, materials, and interfaces

Tritium BreederLi2TiO3 (<2mm)

First Wall(RAFS, F82H)

Neutron MultiplierBe, Be12Ti (<2mm)

Surface Heat FluxNeutron Wall Load

[18-54] mm/s

PbLi flow scheme

[0.5-1.5] mm/sHCLL

HCSB

Solid Breeder Blanket utilizes immobile solid Solid Breeder Blanket utilizes immobile solid lithium ceramic breeder and Be multiplier for lithium ceramic breeder and Be multiplier for tritium self-sufficiencytritium self-sufficiency

US DCLL Blanket The Dual Coolant Lead Lithium (DCLL) TBM Concept provides a pathway to high outlet temperature with RAFS and SiC Flow Channel Inserts (FCI) to thermally and electrically isolate PbLi breeder/coolant

PbLi Flow Channels

He-cooledFirst Wall

PbLi

He

He

SiC FCI

2 mm gap484 mm

NGK Be-pebble

State-of-the-art R&D on solid breederState-of-the-art R&D on solid breeder

In-pile pebble bed assembly tests

Out-of-pile tests (ENEA)

Li4SiO4 pebbles in filling

NRG

Unit: mm

Tritium breeding summary

• State-of-the-art: Multiple solid and liquid breed concepts. Parts of these concepts have been tested. No realistic, integrates tests have been performed.

• Demo requirement: Demo must breed all of its own tritium.• Gap: Integrated testing, demonstration and qualification of

Demo breeder needed prior to Demo construction– Example sub-gaps:

• For DCLL, what characterizes the flow channel inserts (FCI) made of SiCf/SiC composite for the dual coolant lead lithium (DCLL) blanket application, and how will such a component maintain its function throughout blanket lifetime?

• For solid breeder: What radiation resistant properties should the solid breeder pebble have in order to maintain good tritium release properties throughout blanket lifetime?

1.1.6 Recovery of bred tritium

Bred tritium extraction summary

• State-of-the-art: Data-to-date suggest that tritium recovery from the breeding material with acceptable tritium inventory is feasible. However, only preliminary tests have been performed.

• Demo requirement: Recover tritium so that inventory and tritium migration is acceptable

• Gap:– Select and test tritium extraction methods

– Demonstrate that tritium can be reduced to levels which will not challenge containment systems. Include extraction from Be.

– Testing in concert with 14 MeV neutrons, high burn up and high flux are needed.

1.1.7 Characterize, recover and handle in-vessel tritium

In-Vessel Tritium Holdup – Function & State-of-Art

• State-of-the-Art

– Full W and/or Be wall test planned on JET and Asdex-Ug

– ITER design includes C (strike point) and W for divertor, and Be wall

– Data from deuterium-fueled toroidal and linear experiments indicate difficulties for using C and Be in Demo (erosion, co-deposition, migration etc.)

– Infiltration and damage by He in W plasma facing component observed under non-Demo-like environment

• Demo Function/Requirements

– Relatively low burn fraction results in high fueling rates

– Presently assume W PFC and first walls with only limited erosion, re-deposition, and co-deposition.

– Will have much higher temperature than ITER

In-Vessel Tritium Holdup – Gaps & Research Thrust

• Gaps– Presently there is no W PFC testing data in Demo-like nuclear

environment

– Tritium hold-up issues can be drastically reduced if (burn up fraction) / (recycling coefficient) could be substantially reduced

• Needed Research– Test Tritium Hold-up on W divertor and First Wall under Demo-

relevant conditions

– Test and develop knowledge needed to increase (burn up fraction) / (recycling coefficient) under relevant toroidal plasma conditions ( Themes I, II, III)

Additional Issues

• Tritium recovery in waste components– ITER: high temperature bake out in tritium controlled hot cell

• Hold-up in hidden and cooler areas (gaps, ducts, behind in-vessel components such as RF launchers, etc.)– Maintain similar temperature in these components

• Wall conditioning produced tritium stream– ITER: use available tritium exhaust and recovery system

• Impurities introduced into vessel due to abnormal or accidental conditions including from auxiliary systems such as NBI (SF6 insulator)– Limit material choices for in-vessel and auxiliary systems

Gap Summary

Area Gap

Fuel processing Major scale-up may require new/different technologies or approaches

Vac & FuelMajor scale-up may require new/different

technologies or approaches

T HandlingMajor scale-up may require new/different

technologies or approaches

Nuc FacMajor scale-up may require new/different

technologies or approaches

T BreedingMust develop and demonstrate Demo-

relevant technology

Extraction of bred T Must develop and demonstrate Demo-relevant technology

In-vessel TMust develop and demonstrate Demo-

relevant technology

Fuel Processing Thrusts

• Tritium processing facility• CTF• Heated loop• ITER TBM• Neutron-irradiated permeation experiment• Tritium extraction from breeder• Modeling

Thrust notes

• CTF and ITER TBM from a tritium standpoint will likely be “production” facilities and will afford little opportunity for experimentation

• The other thrusts will provide much opportunity for experimentation

Initial ideas for fuel cycle thrusts

How do we close the fusion fuel cycle?

Area

Tritium Processing

Facility CTFHeated

Loop ITER TBM

Neut-irr Permeation

BarrierExtract. Exper. Modeling

Fuel processing xx xx X x x

Vac & Fuel xx xx x

T Handling x x Xx xx x x

Nuc Fac xx xx X X x

T Breeding Xx xx x

Extraction of bred T xx Xx xx xx x

In-vessel T x X X x x