Tritium in ITER.ppttritium.nifs.ac.jp/project/20/pdf/t2.pdf · Tritium in ITER Presented by Scott Willms ITER Fuel Cycle Integrated Product Team Co-Lead Los Alamos National Laboratory

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Fusion Reactor Fuel Cycle Manfred Glugla, Lecture INSTN Page 1

Manfred Glugla

Fuel Cycle Engineering DivisionCentral Engineering Department

ITER Organization

Tritium in ITER

Presented by Scott Willms

ITER Fuel Cycle Integrated Product Team Co-LeadLos Alamos National Laboratory

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Outline of the Lecture

• Properties of tritium

• Introduction to the fusion fuel cycle

• Selected systems of the fusion fuel cycle using ITER as an example– Hydrogen isotope storage and delivery– Exhaust gas processing– Isotope separation and water detritiation– Fueling System configuration and Pellet Injection– Torus Cryo-pumping– Safe handling of tritium and confinement strategies at ITER

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Historical Aspects and Background

• Deuterium was discovered about 80 years ago by H. Urey 1931

• Tritium synthesized by M. Oliphant, P. Harteck, E. Rutherford 1934

• Tritium is continuously produced in the upper earth atmosphere

– Amount produced negligible compared to anthropogenic tritium• Emissions from nuclear reactors and reprocessing plants• “Natural” global atmosphere inventory estimations between 4 to 7 kg

– Significant residual inventory from atmospheric nuclear weapons tests• Today’s total tritium atmosphere inventory estimated to about 40 kg

• Tritium has never been seen in space (but deuterium has)

HHHH 11

31

21

21

CHnN 126

31

10

147

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Technical Tritium Production

• Tritium is produced by neutron irradiation of lithium-6

– Lithium aluminate or lithium silicates are irradiated in nuclear reactors• Natural lithium contains only 7.42% of lithium-6, the remaining is lithium-7

• Neutron capture of helium-3 produces tritium– Neutrons from proton accelerators (spallation)

• 100 to 150 g tritium per operational year isgenerated by a 600 MW CANDU reactor

– CANDU reactors are heavy water moderated and employ natural uranium as fuel

• 56 kg tritium is required per GW(thermal) year of DT fusion power

HeHnLi 43

31

10

63

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Some Tritium Properties

• Tritium is the heaviest hydrogen isotope, radioactive (pure β emitter)– Half life t1/2 = 12.323 + 0.004 years

• about 100 g tritium per year is lost at an inventory of 1800 g

– Energetically almost weakest natural beta emitter Emax = 18.6 keV• 187Re has Emax = 2.5 keV, however at t1/2 = 5 * 1010 years is practically stable

– Maximum range of tritium decay electrons• Air : 6 mm• Metals: < 1 µm

– 1 g tritium• 324 mW decay heat• Activity 355.7 TBq or 9615 Ci• Volume 3.72 Liter (standard temperature / pressure)

– Largest known gyro magnetic ratio• Most sensitive nucleus for NMR spectroscopic investigations

tritium

helium-3

electron anti-neutrino

-

+ +

+

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Areas of Tritium Handling and Usage

• Gaseous Tritium Light Sources (GTLS)– Usually hermetically sealed glass vials

• Contain between 1 Ci / 1 mg (exit lights) and1000 Ci / 0.1 g (aviation landing aids)

– Tritium watches (still on the market) contain about 0.1 Ci

• Neutron generators– Tritium in titanium (Cu substrate) as target for deuterons (50 to 400 keV)

• Tritium is used as tracer in many areas of science and medicine

• Tritium is a practical ionization source– Nuclear batteries (“betavoltaics”) employing porous silicon diodes– Ionization detectors in gas chromatography

• Meta-stable excited helium ionizes gases to be detected in the carrier gas

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Radiochemistry of Tritium (1/2)

• Self-radiolysis of T2

• Self-radiolysis of T2O (liquid T2O is self heating)– β - radiation causes the formation of T2O+ ions, T3O+ ions, T• radicals, OT•

radicals, and T2O2 via consecutive chemical reactions• Due to the primary self-radiolysis products of T2O it is highly corrosive

– Gas phase above T2O becomes pressurized• Radiochemical equilibrium above T2O at 159 kPa

– Rate of gas production balanced by rate of (radiochemical) recombination

TeT 33

othersTT 22

TTTT 322

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Radiochemistry of Tritium (2/2)

• Reaction of T2 with oxygen, nitrogen and air

– Reaction products are subject to (self-) radiolysis– Radiochemical equilibrium composition depends on tritium concentration

(ratio of T/ΣH) and presence of metal catalysts (especially precious metals such as Pt, Pd)

• Reaction of T2 with methane

– If deuterium is present 15 different labeled methanes appear in gas phase4322342 CTCHTTCHTCHCHT

OTOT 222 22

322 23 NHNT

22222 NONOOTOTairT

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Hydrogen Isotope (Physical) Chemistry

• Hydrogen is ubiquitous and the most abundant element in space– Element with the largest number of chemical compounds– No other chemical element can react in such a diversity by either giving

or taking an electron to make a chemical bond– Hydrogen can interact with most metals

• Hydrogen atoms are occupying interstitial places of the metal lattice forming an interstitial alloy

– Only low activation energies are required to move a hydrogen atom to the next nearest neighbor place in the host lattice, leading to fast diffusion of hydrogen

• Exchange of protium with tritium “contaminates” material

• Largest relative mass difference between the hydrogen isotopes protium, deuterium and tritium

– Large isotope effects for chemical reactions• Significant differences in chemical equilibriums and in reaction kinetics

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Periodic Table of Binary Hydrides

• Electropositivemetals aremost reactive

• Inter-metalliccompoundsform metalhydrides

• Metal hydridesstoichiometryMeHn oftennot simple(n ≠ 1,2,3)

• “Hydride gap”

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H - Isotopes Gas Metal Interactions (1/3)

• No energybarrier for tritiumto become physisorbed

– Physisorptionis molecular

– Surfaces easilyget contaminatedwith tritium

• Chemisorption isassociated withactivation energies AEChem

– Chemisorptionis dissociative

AE = Activation Energy

Surface

Solid Phase Gas Phase

Chemisorption Physisorption

T-T

T

Ediss

AEdes

AEChem

Potential Energy

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• No energybarrier for tritiumto become physisorbed

– Physisorptionis molecular

– Surfaces easilyget contaminatedwith tritium

• Chemisorption isassociated withactivation energies AEChem

– Chemisorptionis dissociative

– AEChem can be < EPhys


Surface



T-T

T

Ediss

AEdes

AEChem

Potential Energy

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Surface



T-T

T

Ediss

AEdes

AEChem

AEChem AESolEsol

Solution

Potential Energy• OncechemisorbedH isotope atoms canbecome dissolved

– AEChem for H isotopes tobecome dissolved

– Electronjoins theconductionband

– Screenedprotons(tritons) oninterstitial latticeplaces

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Diffusion of Hydrogen Isotopes inFace Centered Cubic Metals

• Hydrogen isotopes occupy octahedral interstitial sites– MeH1 is limiting

stoichiometry– Diffusion from

one octahedralsite to anadjacent site isthrough thetetrahedral site

– Diffusivity ofH isotopes canbe very high

• Up to about10-5 cm2s-1 at ambient temperature

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Hydrogen, Deuterium & Tritium in Metals

22

21TT KpC

• Hydrogen isotopes are dissolved in metals (α-phase) before metal hydride (β-phase) formation (reversible absorption / desorption)

– β-phase change often leading to metal disintegration into hydride powder– Metal hydrides (MeHs) show very interesting physical properties

• Superconductivity at relativelyhigh temperatures(still cryogenic levels)

• hydrogen density in certainMeHs higher than inliquid hydrogen

• Order-disorder transitionsand phase transitions

• Etc.

• “Sieverts” law

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Tritium and ITER

• ITER is the first fusion machine fully designed for operation with DT– Tokamak vessel will be fuelled through gas puffing and Pellet Injection– Neutral Beam heating system will introduce deuterium into the machine

• Employing DT as fusion fuel has quite a number of consequences– Alpha heating of the plasma, fusion reaction eventually provides energy– Closed DT loop is required (small burn-up fraction in the vacuum vessel)

• Primary tritium systems for processing of tritiated fluids • Auxiliary systems necessary for the safe handling of tritium

– Multiple barriers vital for DT confinement in its process components• Atmosphere & Vent Detritiation Systems are crucial elements in the concept

After all a rather complex chemical plant, i.e. the Tritium Plant of ITER is needed for deuterium-tritium fuel processing

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Plasma

Li

Be

Li

PlasmaExhaust

DT FuelSupply

DeuteriumSupply

Clean-up and DTFuel Recovery

TritiumRe-

covery

Vacuum Pumps

Helium to Stack

BreedingBlanket

He Purge Gas+ Tritium fromBlanket

TritiumSupply

Blower

Inner/Outer Fuel Cycle of Fusion Reactors

• Technically most suitable fusion reactionis the one between deuterium and tritium

D + T→ 4He (3.5 MeV) + n (14.1 MeV)

• Deuterium can be extracted fromnatural water (SMOW 0.016%)

• Tritium must be imported (very limited)or bred internally from lithium

– Import from heavy water moderatedfission reactors (CANDU type)

• T from neutron capture by D • Waste product to be removed from D2O

– Breeding reactions in a fusion reactorn + 6Li → T + 4He or n + 7Li → T + 4He + n

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Simplified ITER Fuel Cycle

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ITER fuel cycle block diagram

14 highly interconnected, multi-functional systems

Will occupy 7-story building

~5 kg tritium inventory

19

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The ITER Closed Tritium Deuterium Loop

Plasma

Tritium (T2)Deuterium (D2)

Fuelling

IsotopeSeparation

TokamakExhaust

Processing

HTO, CT4, ...He, N2, CO, CO2, ...T2, D2, H2, DT, HT, HD

T2, D2

He, N2, CO, CO2, ...H2O, CH4, ...


Storage

DT, HT, HD,T2, D2, H2

T2, D2

TritiumRecycling

with 1

Plasma


Fuelling

IsotopeSeparation

TokamakExhaust

Processing


T2, D2

He, N2, CO, CO2, ...H2O, CH4, ...


Storage


Detritiation Systems

T2, D2

TritiumRecycling

with 1

H2O, HDO, HTO

Water-Detritiiation

IsotopeSeparation

H2, D2,HD, O2

H2, HT(HD)H2

H2, HT

Plasma


Fuelling

IsotopeSeparation

TokamakExhaust

Processing


T2, D2

He, N2, CO, CO2, ...H2O, CH4, ...


Storage


Detritiation Systems

T2, D2

TritiumRecycling

with 1

TritiumRecycling

with 2

> 100 kg tritium per year20,000 $ per g> 1 billion €

< 2 kg tritium per yearburned in ITER

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Deuterium Tritium Fuel Cycle Block Diagram of ITER

Torus

Cryostat Cryo Pumps

Fuelling Gas Distribution

Pellet Injection

Neutral Beam Injection

Neutral Beam Cryo Pumps

Roughing Pumps

Isotope Separation

Storage and Delivery

Tokamak Exhaust Processing

Analytical System

Atmosphere and Vent Detritiation

Water Detritiation

Tritium Depot

Torus Cryo Pumps

Disruption Mitigation System Gas Puffing

Leak Detection

Service Vacuum Systems

Glow DischargeCleaning

Hydrogen (Protium) Release

Off Gas Release

Fusion Power Shutdown System

Automated Control System, Interlock System, Security

Cryostat

External Supplies

MBA 2

Tritium PlantBuilding

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Main Functions of ITER Tritium Systems

• Handling of incoming and outgoing tritium shipments

• Storage / delivery of tritium & deuterium to / from fuel cycle– Determination of nuclear inventories

• Torus vacuum pumping and off gas transfer to processing systems

• Processing of tritium containing fluid streams– Tokamak exhaust / other tritiated off-gases for DT recycling

• Decontamination of gases prior to controlled release into the environment

– Extraction / recovery of tritium from Test breeding Blanket Modules– Separation of hydrogen into specific isotopic species for refueling– Detritiation of water and recovery of the tritium

• Atmosphere and ventilation detritiation

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Torus

Cryostat Cryo Pumps


Pellet Injection



Roughing Pumps

Isotope Separation



Analytical System


Water Detritiation

Tritium Depot

Torus Cryo Pumps


Leak Detection




Off Gas Release



Cryostat

External Supplies

MBA 2


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ITER Tritium / Deuterium Storage & Supply

• Criteria for technical applications of metal tritides– Low equilibrium pressure of hydrogen isotopes at room temperature

• Metal hydride acts as a highly effective pump / Save storage of tritium

– Low temperature for hydrogen equilibrium pressures around atmospheric• Liberation of H isotopes from the metal hydride under moderate conditions

– Flat plateau for the α-phase (dissolution) to β-phase (MeH) transition• H isotope pressure remains constant during release at constant temperature

• Metal hydride bed design– Effective heating and power dissipation

to allow fast hydrogen release• Hydrogen release reaction is

strongly endothermic• Thermal insulation to allow calorimetry• Decay heat is a measure for the tritium content of the bed

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ZrCoHx (log scale) and UHx (lin) Isotherms

0

1

2

3

4

5

6

0 0.5 1.0 1.5 2.0 2.5 3.0

log

p/P

a

x in ZrCoHx

130 °C

Sorption

Desorption

365 °C

300 °C

250 °C

200 °C

160 °C

400 °C

0

4

8

12

16

20

24

28

0 0.30 0.60 0.90 1.20 1.50 1.80 2.10 2.40 2.70 3.00

PRE

SSU

RE

- A

TM

HYDROGEN COMPOSITION - ATOM RATIO H/U

450 °C

500 °C

550 °C

600 °C

650 °C

DesorptionSorption

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ITER 1:1 MeH Storage Bed (Karlsruhe)

• Essential ITER requirements– Safe storage of tritium (ZrCo or U as hydride?)– Inventory measurement by calorimetry– Inherent inventory limitation– Fast, flat top tritium delivery

• Dissipation of a few kW into powder packing

GB-y-3x00y-3x02

y-3x91 y-3x90

TIR

FIR

FIRCA±

FIRy-3x01

y-3x00

y-3x92

PIRA+S++

TIR

to SafetyBuffer Vessel

Tritium Supply toTokamak

He CalorimetryLoop

Tritium fromIsotope Separation He

Supply

High Vacuum

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The “Ash” of Fusion Reactors

Deuterium Tritium Helium

• Gas from plasma / first wall (carbon, beryllium, tungsten) interactions – Carbon oxides (CO, CO2)– Water (Q2O with Q=H,D,T; 6 isotopically different species)– Hydrocarbons (CQ4 (15 isotopically different species), CxQy with x < 8)

• Helium and other gases need to be continuously removed– Plasma confinement strongly dependent upon “impurity” content

A closed deuterium tritium fuel cycle is necessary

++ + + + + + 17.6 MeV

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Torus

Cryostat Cryo Pumps


Pellet Injection



Roughing Pumps

Isotope Separation



Analytical System


Water Detritiation

Tritium Depot

Torus Cryo Pumps


Leak Detection




Off Gas Release



Cryostat

External Supplies

MBA 2


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The CAPER Facility at TLK

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Deuterium Tritium Fuel Cycle of Block Diagram ITER

Torus

Cryostat Cryo Pumps


Pellet Injection



Roughing Pumps

Isotope Separation



Analytical System


Water Detritiation

Tritium Depot

Torus Cryo Pumps


Leak Detection




Off Gas Release



Cryostat

External Supplies

MBA 2


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Separation by Multi Stage Distillation• Mixtures of liquids with different

volatility can be separated by distillation

– Distillate is enriched in the more volatile component

– Residue is depleted in the more volatile component

– Composition of the distillate and residue obviously changes with time

Residue

Boiler

Condenser

Distillate

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Separation by Multi Stage Distillation• Mixtures of liquids with different

volatility can be separated by distillation

– Distillate is enriched in the more volatile component

– Residue is depleted in the more volatile component

– Composition of the distillate and residue obviously changes with time

• Process can be made continuous in a multi stage arrangement

– Feed at a certain stage– Withdrawal of distillate and residue– Counter current vapor-liquid contacting

column instead of multiple boilers

Boiler

Residue

Feed

Boiler

Boiler

Boiler

Condenser

Condenser

Condenser

Condenser

Distillate

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Cryogenic Separation of H Isotopomeres

• Six molecular hydrogen isotopomeres with different boiling points

• H isotopomere separation requires cryogenic temperature distillation

• Separation between HT and D2 is particularly difficult

• Side streams must be withdrawn, heated, equilibrated on a catalyst to split the heterogeneous isotopomeres and returned into the column

2 HD ↔ H2+D2

2 HT ↔ H2+T2

2 DT ↔ D2+T2

Isotopomere H2 HD HT D2 DT T2

Boiling Point [K] 20.7 22.1 23.5 23.8 25.0 25.5

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Isotope Separation Part at ITER (1/2)• ITER cryogenic Isotope Separation

System comprises 4 interlinked columns– Two feed streams

• Tritiated hydrogen and deuterium from the Water Detritiation System mixed with tritiated deuterium from Neutral Beam injection and fed into column (1)

• Deuterium - Tritium design feed flow rate into column (4) from Tokamak Exhaust Processing (TEP) system is about 7 m3h-1

– Four product streams• Tritium (90% purity)• Deuterium contaminated with tritium

(refueling)• Deuterium at high purity

(Neutral Beam injection)• Hydrogen (protium) for return to

Water Detritiation System

ISSColumn-1

Protium Return

Eq-2

Eq-3

Eq-5

ISSColumn-2

ISSColumn-3

ISSColumn-4

Eq-6

Eq-1

D2 (NBInjection)

From Plasma Exhaust

Eq-4

H2 (D, T) Feed

D2 (T) Product to SDS

T2 (90 %) Product to SDS

Eq-7

DT (50 %) Product to SDS

DT Feed

H2 (T) from Neutral Beam

H2O Protium Reject

H2O (D, T)

WDSLPCE

Column

Electrolyzer

H2(D, T)

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Isotope Separation Part at ITER (2/2)• ITER cryogenic Isotope Separation

System comprises 4 interlinked columns– ISS operation is characterized by

transients and non-steady states• ITER is a pulsed machine• Protium from Isotope Separation System is

returned to the Water Detritiation System for decontamination

– Complex operation of two interlinked systems

• Cryogenic Isotope Separation Systems have large tritium inventories

– Liquid tritium handling • Loss of refrigerant (cooled helium)

evaporates large amounts of liquid hydrogen (and tritium)

ISSColumn-1

Protium Return

Eq-2

Eq-3

Eq-5

ISSColumn-2

ISSColumn-3

ISSColumn-4

Eq-6

Eq-1

D2 (NBInjection)

From Plasma Exhaust

Eq-4

H2 (D, T) Feed

D2 (T) Product to SDS

T2 (90 %) Product to SDS

Eq-7

DT (50 %) Product to SDS

DT Feed

H2 (T) from Neutral Beam

H2O Protium Reject

H2O (D, T)

WDSLPCE

Column

Electrolyzer

H2(D, T)

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Torus

Cryostat Cryo Pumps


Pellet Injection



Roughing Pumps

Isotope Separation



Analytical System


Water Detritiation

Tritium Depot

Torus Cryo Pumps


Leak Detection




Off Gas Release



Cryostat

External Supplies

MBA 2


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Water Detritiation by the Liquid Phase Catalytic Exchange Process (1/2)

• Counter current isotopic exchange– Tritiated water is fed into an electrolyzer, H2

(HT) sent through a boiler into the column– Fresh water introduced at column top (flow

rate roughly same as for tritiated water)– Water is condensed at the top of the

column, flows back (and is electrolyzed)– ITER Liquid Phase Catalytic Exchange

• requires decontamination factor of ≈ 108

– tritium feed concentration about 1011 Bqkg-1

– hydrogen with a tritium concentration of only 700 Bqm-3 will be stacked

• will employ a solid polymer electrolyzer– low tritiated water inventory

Condenser

Scrubbing Section:

Catalytic Section:

Boiler

HT, H2

H2

(H2O)l

(HTO)v + (H2O)l (H2O)v + (HTO)l

HT + (H2O)v (HTO)v + H2

Solid Polymer Electrolyzer

(H2O)l + (HTO)lHT, H2 to

Isotope Separation

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Water Detritiation by the Liquid Phase Catalytic Exchange Process (2/2)

• Isotope exchange takes place in two sections– Catalytic section: HT + (H2O)v → (HTO)v + H2

– Scrubbing section (HTO)v + (H2O)l → (H2O)v + (HTO)l

Condenser

Scrubbing Section:

Catalytic Section:

Boiler

HT, H2

H2

(H2O)l

(HTO)v + (H2O)l (H2O)v + (HTO)l

HT + (H2O)v (HTO)v + H2

Solid Polymer Electrolyzer

(H2O)l + (HTO)lHT, H2 to

Isotope Separation

0.004 0.006 0.008 0.010 0.012 0.014 0.016 0.018 0.020 0.022 0.024 0.026 0.0280.0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

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Torus

Cryostat Cryo Pumps


Pellet Injection



Roughing Pumps

Isotope Separation



Analytical System


Water Detritiation

Tritium Depot

Torus Cryo Pumps


Leak Detection




Off Gas Release



Cryostat

External Supplies

MBA 2


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Calorimetry as aSelective Analytical Method for Tritium

• Thermal power produced by tritium ß-decay is used to measure the amount of tritium

• Calorimetry is a non-destructive method and can be used to determine tritium in gases, liquids and solids such as

– Tritium in gases or water– Tritium in structure materials– Tritium in waste for disposal

• Limitations of Calorimetry– No other heat-producing

components should be present– Sample size is restricted to the

measurement calorimeter volume

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Principles of Calorimetry

• Two types of calorimeters– Isothermal system

• T(outside) = const.• T(inside) = const.• Heat flux detected to

provide a measurefor the tritium amountTritium amount= f (heat fluxthrough surface )

– Adiabatic system • T(outside) = const.• T(inside) detected to provide a

measure for the tritium amountTritium amount = f (T(inside) – T(outside))

T(inside)

T(outside)

Insulation

Calorimeter Cup

outercylinder

middlecylinder

innercylinder

Calorimeter Cup

Peltier Cooler

insulation

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Torus

Cryostat Cryo Pumps


Pellet Injection



Roughing Pumps

Isotope Separation



Analytical System


Water Detritiation

Tritium Depot

Torus Cryo Pumps


Leak Detection




Off Gas Release



Cryostat

External Supplies

MBA 2


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Fueling System Configuration

• Gas Injection System (GIS)– Upper port level GIS : 4 ports– Divertor port level GIS : 3 ports

• Pellet Injection System (PIS)– 3 divertor ports (2 injectors each)

• 2 injectors at start-up• 6 injectors after up-grade

• Disruption Mitigation System (DMS)– Two locations at upper port level

• Fusion Power Shutdown System– Two locations at upper port level

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Conceptual Design of ITER Pellet Injector(Pneumatic Accelerator)

Roots + Screw BlowerPropellant Compressor

Pellet Injector

V1

V2Cryocooler

Compressor

MicrowaveCavity

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Fusion Plasma Fuelling Through Pellet Injection

• ITER plasma is fuelled by gas puffing andby Pellet Injection (PI)

– Twin screw extruder to producepellets of D and T ice(frozen deuterium and tritium)

– Typical pellet is a 6 mm by 6 mm cylinder– Pellets are injected through a gas gun

• Compressed deuterium employed as propellant

– Pellet speed is 1300 km per hour• Faster than the speed of sound in air

– Up to 20 pellets per second from a singlepellet injector

Pellet in ASDEX plasma

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Flight Tube Layout

Cryopump housing

Divertor port

LFS flight tube

HFS flight tubeCryostat

DIIID Pellet Injection movie

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Torus

Cryostat Cryo Pumps


Pellet Injection



Roughing Pumps

Isotope Separation



Analytical System


Water Detritiation

Tritium Depot

Torus Cryo Pumps


Leak Detection




Off Gas Release



Cryostat

External Supplies

MBA 2


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ITER torus exhaust vacuum system

Torus exhausthigh vacuum pumping system

Duct double bellows

Pumping duct

Entrance from the plasma

Installation points for torus cryopumps

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Vacuum Systems Requirements and Design Basis

• Helium (the fusion reaction “ash”) need to be continuously removed– Continuous removal of helium together with unburned DT & other gases

• Plasma density control through fuelling and vacuum• Broad spectrum of gases will have to be pumped

• ITER vacuum pumping systems employscryo-panels forced cooled bysupercritical helium at 4.5 K and 0.4 MPa

– Helium & hydrogen isotopes pumpingassured via cryo-sorption

• Cryo-condensation for heavier gases

– Cryo-panels with micro porousactivated coconut charcoal

• Glued to the cryo panels by means of atritium compatible inorganic cement

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1:2 Torus model cryopump (Karlsruhe)with outside valve (DN 700, 400 mm stroke)

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Tritium Confinement Philosophy

• Confinement of tritium within its respective fuel cycle processing systems / components is in effect the most important safety objective

– Basic targets of confinement• Prevent spreading of radioactive material in normal operation

– Maintain contamination level as low as reasonably achievable (ALARA principle)• Keep radiological consequences for operators, public and environment in off-

normal conditions within acceptable levels

– Confinement function is achieved by a coherent set of physical barriersand / or auxiliary techniques intended to confine radioactive substances

• IAEA practice is to use the term “containment” for physical barriers– Term “confinement” is more general, refers to function of confining radioactive

material within a certain volume and includes filtering and atmosphere processing• Primary confinement system is designed to prevent releases of radioactive

materials into the accessible working areas• Secondary confinement system prevents releases to working areas accessible

by non-authorized radiological workers, general public and the environment

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ITER Ventilation & Confinement Concept

• Secondary confinementcomprises sub-atmosphericpressure control andatmosphere detritiation

– Heating, Ventilation,Atmosphere Conditioning(HVAC) not categorized to beSafety Important Class (SIC)

– Vent detritiation is SIC

• Primary confinement caninclude more than one barrier

– Glove box (GB) formaintenance purposes

– GB atmosphere detritiation

PrimarySystem

HVACSupply

Fresh Air

(Glove Box)

ReleasePoint

ISS Cold Box

HVAC Exhaust

Glove BoxDetritiation

System (GDS)

VentDetritiation

AtmosphereDetritiation

ISS

Building Sector

Surrounding Barrier(Glove Box)

PrimarySystem

Surrounding Barrier

SecondaryConfinement

Building Sector/ Tritium Spill

PrimaryConfinement

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Tritium Plant Building Systems Layout• 7 Stores

– 2 belowgrade

• L = 80 m

• W = 25 m

• H = 35 m

• Releasepoint elevation:60 m

– Tokamak building height: 57 m

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Summary

• Deuterium / tritium fusion reactors require a closed fuel cycle– Low burn-up fraction leads to high DT throughputs within Tritium Plant

• Unprecedented tritium flow rates and tritium processing requirements

– ITER relies on pellet injection for plasma density control– Distributed Vacuum System with cryo-pumps and roughing pumps

• Deuterium / tritium processes cover wide range in physical chemistry– Variety of overlapping effects when dealing with all 3 hydrogen isotopes

• Hydrogen isotopes in metals– Permeation of hydrogen isotopes, dissolution and hydride formation

• Heterogeneous catalysis, chemical reaction kinetics and chemical equilibria• Separation techniques in fluid systems• Analytical tools such as calorimetry

• Safe handling of tritium achieved by multiple confinement strategies

Documents

Tritium in ITER.ppttritium.nifs.ac.jp/project/20/pdf/t2.pdf · Tritium in ITER Presented by Scott Willms ITER Fuel Cycle Integrated Product Team Co-Lead Los Alamos National Laboratory