Tritium fuel cycle and self-sufficiency - R&D for DEMO and required extrapolations beyond ITER
Christian Day, Project Leader of the EUROfusion TFV (Tritium-Matter Injection-Vacuum) Project 15-18 November 2016, KIT Outline
. Introduction . EU DEMO fuel cycle single technology developments . Fuel cycle integration aspects . Conclusions
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 2 EU DEMO Power Plant Definition
DEMO Mission Statement: “The DEMO power plant has to be a representative fusion power station in terms of predictable power production, fuel cycle self-sufficiency and plant performance thereby allowing an extrapolable assessment of the economic viability, safe operation as well as environmental sustainability for future commercial fusion power plants (FPP).” G. Federici, FED 2016. Hence, DEMO has to: . Be conceived as single step between ITER and a commercial FPP . Produce net electricity (several 100 MWe), safely and reliably . Be tritium self-sufficient and start up another reactor . Demonstrate all technologies for the construction of a commercial FPP Have a representative (extrapolable) performance: . Lifetime . Cost ..Hence, DEMO is not a . Availability and net efficiency large ITER, but different. . Waste
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 3 Tritium self sufficiency
Demonstration of tritium self-sufficiency is a central element in the fusion roadmap. To demonstrate tritium self-sufficiency successfully, we need to be successful in three aspects at the same time:
We need to have sufficient tritium to start and then to provide: Good tritium breeding ratio Breeding blanket / TBR Outer fuel Cycle
Efficient FCT fuel cycle technologies to reduce inventory BUF High burn-up fraction Particle exhaust at divertor
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 4 Central DEMO fuel cycle challenge – Inventory reduction
. In a simplistic way, one may think to just scale up the ITER fuel cycle. . What we found was that this will end in a number of issues: …operational complexity, facility size (cost), … but most of all: . The tritium inventory may act as a SHOWSTOPPER for DEMO: …in terms of the start-up inventory (may be too high) …in terms of the regulatory limit (may not be achievable) …in terms of excessive cycle times and correspondingly too large inertia of the system (tritium plant becoming a very very large chemical plant) . DEMO is a (pre-commercial) power plant, not a physics device designed for experimental flexibility . DEMO will be designed around one single operational target point (within an uncertainty margin due to control safety, stability and to meet unknowns, designed for a metal wall right from the start)….
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 5 Generic functional fuel cycle scheme
Water Inner part Detritiation Outer part DT Fuelling & D,T Storage & D, T Plasma T H,(T) Control Delivery Isotope
Separation Torus Q
Tritium 2 Blanket Tokamak Plant Tritium Recovery Q Q2 Primary Rough 2 Water, He Pumping Pumping Water, He Impurities Impurities
Tritium Tritium Q2 Extraction Accountancy Helium / Water Coolant Q = H,D,T Purification B. Bornschein, FED 2013.
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 6 Generic functional fuel cycle scheme (2)
M. Abdou, FED 2015.
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 7 Fuel cycle implementation CFETR
GC, CD, TCAP
ITER-style Cryopumps
C.A. Chen, Technical Exchange Meeting, Jan 2016
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 8 Design driver to advance the fuel cycle architecture
Target is - to reduce processing times - to increase fuelling efficiency - to increase burn-up fraction
M. Abdou, FED 2015.
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 9 Outline
. Introduction . EU DEMO fuel cycle single technology developments . Fuel cycle integration aspects . Conclusions
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 10 Innovative new fuel cycle concept - FBS
Derived with a rigorous systems engineering approach
, PEG
PEG,
PEG
Separation enables DIRECT INTERNAL RECYCLING Chr. Day, FED 2016.
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 11 Innovative new fuel cycle concept - FBS
+ Bypass to the Tokamak to allow easy ramp-up during dwell ´always´steady state
, PEG
PEG,
PEG
RESIDENCE TIMES TRITIUM CONTENT MINIMISED INVENTORY
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 12 Technology ranking results tritium
Rank Technology Impurity removal (85%) From the ranking we 1st Pd-Alloy Permeator derive which R&D has to 2nd Cryogenic Adsorption on Rank Technology be done with highest Molecular Sieve Impurity processing 1st Membrane Reactor priority 3rd Getter Bed (80%) (catalyst + permeator) 4th CryogenicRank Freezing Technology Primary loop protium removal and isotope sep. 2nd 1stHigh TemperatureThermal cycling Electrolysis absorption process 3rd Catalytic Oxidation (75%) Rank Technology Isotope re-balancing (75%) 2nd Plasma 1Separationst Plasma Process Separation Process 3rd Cryo-distillation2nd Thermal cycling absorption Rank Technology Storage (alt. U-Bed) 4th Gas chromatographyprocess Magnesium hydride catalysed ball (63%) 5th Electromagnetic3rd Cryo isotope1-stdistillation separation milled 4th Quantum Sieving 2nd DepletedRank uranium Technology Tritium 6th Quantum5th Sieving Laser Isotope Separation 3rd Zirconium1st cobalt Getter Beds recovery 7th Pressure6 thSwing AdsorptionGas chromatography 4th Super diamond2nd nanotubesMolecular Sieve Bed from helium 8th Laser Isotope7th SeparationPressure Swing Adsorption Ammonia3rd borane Cryogenic SBA 15 (mesoporous Molecular Sieve Bed coolant (70%) 9th Gaseous8 thDiffusion Electromagnetic 5th isotope Rank Technology silica scaffold)4th Pd-Ag Membrane 10th Molecular Laser separationIsotope Separation 1st Combined electrolysis and Tritiumcatalytic recovery 6th Sodium5 alanateth Water Gas Shift Reaction 9th Gaseous Diffusion exchange from water coolant 7th Lithium6 Borohydrideth Cold Trap 11th Kinetic Isotope10th EffectsKinetic Isotope Effects 2nd Liquid Phase catalytic exchange(67%) 8th Activated carbon Success of12th 30 Centrifugation11th Molecular laser isotope 3rd Direct electrolysis 9th MOF- 5 (metal organic frameworks) Accountancy (75%) year fusion separation 4th RankVapor Technologyphase catalytic exchange 10th Magnesium Borohydride5th Water distillation research 12th Centrifugation 1st BIXS and scintillation depending on detection case (13 cases altogether) Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 13 Main R&D headlines tritium
Exhaust Processing R&D – Technology Helium coolant detritiation R&D – similar to ITER, but operation conditions Need for performance improvement of different: existing technology in view of the huge - Significantly higher PEG concentration flowrates involved. reduces hydrogen partial pressure - PEG may be activated Water coolant detritiation R&D - - Scaling towards higher throughputs Similar technology as for ITER and also unclear applied in heavy water reactors. However, scaling to DEMO seems to Protium removal and isotope re-balancing have a significant impact on plant cost. R&D – TCAP is not used at ITER but has been Dynamic control of the loops R&D – advanced mainly in the defense Due to the continuous operation of the programmes (US, F, China). fuel cycle avoiding the use of - Own complementary work may be needed intermediate storage wherever to get full understanding possible, gas distribution, control and - Scaling towards DEMO throughputs and tritium accountancy become more resulting complexity must be assessed. important.
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 14 New requirement: PEG
A variety of plasma enhancement gases are needed for DEMO: For confinement recovery at a metal wall, for radiative seeding, … Different candidates have different activation progeny.
R. Walker, SOFT 2016
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 15 Translation into resource loaded R&D programmes
Considering the existing limitation of resources in the TFV project. At any time in the project the choice of projects to be funded can be re- adjusted immediately.
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 16 Technology review outcome BB interface
TRITIUM EXTRACTION from the breeder has to convert the breeder outlet (tritiated water, Q2, carrier species) to an input stream to the tritium plant.
Solid Breeder (HCPB) Cryo-batch Rank Technology concept retained as 1st Cold trap and adsorption 60% columns reference at 2nd Continuous catalytic 60% the moment membrane reactor 3rd Getter bed 50%
Liquid Breeder (HCLL, WCLL, DCLL) vacuum Rank Technology + tritium 1st Permeator against vacuum 87% PbLi in
2nd Vacuum sieve tray 75% c1 3rd Gas-liquid contactor PbLi out 50% c2 membrane
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 17 Technology review outcome matter injection (1)
Matter injection has to provide the function of FUELLING and PLASMA CONTROL.
Fuelling (ELM pacing ?) For core fuelling, we go for pellet injection, however have to advance this beyond Rank Technology 75% the ITER operational window. 1st Classical pellet injection
2nd Microwave, laser, railgun For gas injection (PEG, gas puffing, incl. 3rd Gas puffing, supersonic jets < 50% (with ´zeros´) massive gas injection) we rely much 4th Compact tori on ITER technology. 5th Unmagnetized plasma jet
Large ratio Pellet mass / Plasma mass Small ratio Pellet mass / . Large penetration Plasma mass deposition in the core . Shallow penetration . Moderate plasma deposition at the edge pressure . High plasma pressure limited drift large drift B. Pegourie, 2016 Can be fueled from the LFS HFS injection mandatory
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 18 Technology review outcome matter injection (2)
Pellet parameter Particle deposition Operational Parameters 20 -3 profile core ne = 0.9 x 10 m > nGw Pellet technology Pellet physics Fusion power
R&D pellet physics – Develop a self- P.T. Lang, FED 2015 consistent physics model that translates plasma parameters in Curved guide tube engineering requirements (workflow). ~ 1 km/s R&D pellet guiding tubes – We do have a need to increase launch speed (over what ITER requires) and effective guiding tube systems.
R&D technology demonstration – An EU pellet test bed is needed to develop all engineering features of the Free flight option DEMO pellet injector: rate, mass, (double stage gas gun) speed ~ 3 km/s B. Plöckl, FED 2015 Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 19 Technology review outcome matter injection (3)
Nowadays technology: The (unwanted) contribution of launch the pellet injection system to the ≈35%....65% machine throughput (SOL, (given by losses Vacuum system) is essential. In the guiding system and SOL curvature and speed, deposition depth)
P.T. Lang, 2015.
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 20 Technology review outcome vacuum (1)
PRIMARY PUMPING has to provide very high pumping speeds, but – different to conventional applications - due to large flowrates, not due to low pressures.
Chr. Day, IEEE Trans. Plasma Science 2014. R&D metal foil pump for separation and Primary pumping Pump with separation function Direct Internal recycling – The metal foil pump has never gone into commercial Rank Technology applications. Develop technology from 1st Vapor diffusion pump (continuous) 70% fundamental physics. 2nd Metal foil pump (continuous) 3rd Cryocondensation 50% R&D diffusion pump – Develop vapor 4th Cryosorption diffusion pumps for high throughputs 5th Cascaded cryosorption 6th Continuous cryosorption and pressures by integration of 7th Warm turbopump 30% additional jet stages. 8th Cold turbopump R&D cryopump – Develop multi-stage R&D topic divertor integration – cryopumps which – to some extent – Contribute to an integrated design of the would allow to implement a separation DEMO divertor by physics-based capability into cryopumping fall- modeling of the particle exhaust to back solution (for risk mitigation). extract the influence of pumping speed (workflow) Chr. Day, FED 2014
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 21 Technology review outcome vacuum (2)
The most challenging requirement for mechanical ROUGH PUMPING for DEMO is the required tritium compatibility at large throughputs (excluding most conventional solutions due to rotary feedhrough issues).
Rough pumping T. Giegerich, Fus. Sci. Technol. 2015 Rank Technology 1st Liquid ring pump 90% R&D ring pump – Integrate a tritium 2nd Roots pump 70% compatible liquid metal (mercury) 3rd Scroll pump into a liquid ring pump. 4th Rotary vane pump 5th Screw pump 40% 6th Diaphragm pump
R&D wall outgassing – To respond to one of the high-level requirements: Integrated modelling of DEMO pump- K. Battes, FED 2015 . down (dwell phase).
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 22 Technology choice vacuum (1)
. Metal foil pumping is a central part of the DIR concept . Allows continuous gas separation under vacuum, close to the machine . Works only as a pump for atomic hydrogen isotopes . Thermal or non-thermal atomizers for generating atomic hydrogen available . Experimental investigations currently ongoing in a small scale test set-up . Modelling method required for scaling HERMES Classical permeation ½ ½ ~ (p1 -p2 ) test facility @ KIT
Superpermeation
~ flux1
B. Peters, SOFT 2016.
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 23 Technology choice vacuum (2)
T. Giegerich, FED 2016. T. Giegerich, SOFT 2016. . Linear vapour diffusion pumps as . Liquid ring pumps with mercury as simple, reliable and tritium- operating fluid compatible primary pumps . A full scale tritium-compatible pump . Customized design for optimal will be built and utilized at JET DT pumping operation (2018). . Using mercury as operating fluid
Demonstration in JET DT campaign in 2018.
THESEUS test facility @ KIT
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 24 Direct Internal Recycling Process
KALPUREX©: Karlsruhe liquid metal based pumping process for reactor exhaust gases
T. Giegerich, FED 2014 .
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 25 DEMO fuel cycle chosen technologies
Dynamic control
Pellet injection U-bed
, PEG
CD TCAP
CECE
PEG
Metal foil Mercury based Membrane Water formation pumping vacuum reactor pumping
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 26 Current DEMO fuel cycle architecture
R. Lawless, TRITIUM 2016.
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 27 Outline
. Introduction . EU DEMO fuel cycle single technology developments . Fuel cycle integration aspects . Conclusions
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 28 Tritium migration issues ask for joint assessments
The tritium extraction from the blankets is an interface that sets how the tritium handling load is shared between the blankets and the tritium plant. Similarly is teh tritium recoveyr from teh breeder coolant. It consequentially has to be assessed by all stakeholders (system owners) together.
T production T releases ~ 360 g/d < 0.002 g/d
D. Demange, 2012
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 29 Example CPS interfaces
. The amount of tritium permeation from BB to Coolant loop is necessary
to define the αCPS (fraction of coolant treated inside CPS). . A correct assessment of the tritium permeation can derive only from an integrated approach.
• Cooling tubes area • T release
• Cooling tubes into env. • ηTES thickness T permeation T permeation PHTS BB Coolant & BOP • Anti-permeation • Anti-permeation barriers (PRF) barriers (PRF) • Oxide layers • Oxide layers CPS
BB Designers • ηCPS CPS efficiency and coolant chemistry T simulation • α Fraction of coolant to be treated in CPS PHTS & BOP Designers CPS Materials CPS Designers Safety • Tritium inventory in the cooling channels • Tritium inventory in the coolant (HT and HTO)
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 30 CPS requirements (1)
Input data 2 • Allawable T conc. in the F, c0 coolant (c ); 0 BB • Tritium permeation from BB αF, c0 αF, cu CPS SG to coolant (F ); FT, p T,p 3 4 PRF • CPS efficiency (ηCPS); 1 • Permeation Reduction F, ci F, c0 Factor (PRF)
Parametric Analysis Coolant fraction to be 퐹푇,푝 1-2 The calculations have been 퐹푐0 = 퐹푐푖 + treated inside CPS 푃푅퐹퐵퐵 performed considering 푐 − 푐 퐹푇,푝 0 푢 푃푅퐹 • c0= 5ppb; 3-4 휂퐶푃푆 = 훼 = 퐵퐵 푐0 퐹푐0휂퐶푃푆 • FT,p in Case#1 and #2
• ηCPS equal to 0.9 and 0.95 2-1 퐹푐푖 = (퐹 − 훼퐹)푐0 + 훼퐹푐푢 • PRF equal to 1, 10 and 100 A. Santucci, SOFT 2016
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 31 CPS requirements (2)
Amount of coolant to be treated inside the CPS for Amount of coolant to be treated inside the CPS for different CPS efficiencies and PRF values: HCPB different CPS efficiencies and PRF values: WCLL
α × F, α × F, η PRF α CPS η PRF α CPS CPS BB CPS kg s-1 CPS BB CPS kg s-1 1 0.00083333 2.000 1 0.00787037 37.77777 0.9 10 0.00008333 0.200 0.9 10 0.00078704 3.777778 100 0.00000833 0.020 100 0.00007870 0.377778 1 0.00078947 1.894737 1 0.00745614 35.78947 0.95 10 0.00007895 0.189474 0.95 10 0.00074561 3.578947 100 0.00000789 0.018947 100 0.00007456 0.357895
• In ITER // HCPB-TBM: 0.00372 kg s-1 • In ITER // entire WDS: 0.0166 kg s-1)
A. Ciampichetti, FED 2010 G. Piazza, F4E
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 32 Philosophy for Implementation of R&D work – Complement to experiments
. A unified fuel cycle simulator is being developed, which integrates the individual system blocks. This will be based on Aspen Custom Modeller, an equation oriented solver platform for dynamic process simulation, we work to do this in collaboration with ITER. . A predictive model is being elaborated for each system block. . The model is tested and deployed if working, or iteratively improved. . The model (and at a later stage the complete simulator) is a perfect tool to explore design space and conduct parametric variations of influential parameters.
Open, commercially available and fully documented chemical engineering plant software, no in-house codes
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 33 Fuel Cycle Simulator based on comm. software platform
Numerical implementation cross- check vs ABDOU, 1985
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 34 Philosophy for model preparation
. The model can be on various levels… . fundamental equations (such as diff. balance and conservation equations), . applicable difference equations (such as HTU, NTU, stage concepts,…), . correlation of representative experiments, zeroth order approaches. . …requiring largely different computational efforts… . …and providing largely different understanding for further system optimization.
. Once the model is there, it has to be tested. This requires to have a representative test case, which can be literature data or experiments. . Often, we will find that we miss input information. Then, one has to set up additional side-experiments to generate such input information (thermodynamic properties, transport coefficients, kinetics,...) needed to run the main model so that the results are quantitatively representative. . This is the only accepted driver for experiments (not scientific curiosity…), and even this only if it is known that the side-experiment result has a high impact on the model result.
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 35 Integrated Physics model of the (physics relevant) part of the fuel cycle Pellet injection engineering 10 Holistic approach: 8 Physics-Engineering Pellet deposition and 6 Integration is a must. ablation modelling
4
Core transport model2 SOL loads to exhaust
and burn control] m
[ 0 system Z
− 2
− 4 Detached Divertor modeling Sub-divertor neutral flow and recycling modelling − 8 Particle exhaust und − 10 2 4 6 8 10 12 14 16 R [mpumping] engineering
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 36 DT machine gas throughput
. For steady state DEMO operation fuel replenishment due to DT burn is rather small (~2.6 Pa m3/s) and corresponds to the low burn-up fraction (high T inventory)
. DT particle throughput due to plasma outflow strongly depends on the tungsten wall outgassing and pumping . Can be roughly estimated as 40 Pa m3/ s and is being fuelled by HFS pellets.
. DT replenishment due to He removal in DEMO will very much depend on He enrichment factor in divertor. For limited He concentration in core ≤ 5% one needs to inject about 180 Pa m3/s for enrichment factor value higher than 3%.
. LFS GP about 75 Pa m3/s will required for generation of sufficient neutral pressure and low power loading in the divertor (detachment).
. Pellet-induced ELMs remove DT particles and are replenished by injected HFS or LFS pellets ~19 Pa m3/s . N=1x1021/s = molecular gas throughput This sums up to minimum 300 Pam³/s DT + ELM pacing of 1.7 Pa∙m³/s gas load + PEG + SOL losses (mainly from pellet injection (referenced to T=273.15 K) pumping) Burn-up fraction of maximum 1 %.
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 37 DT machine gas throughput with high burn-up fraction
2 H. Zohm, 2015. n nV Concept to increase ß: fuel burn pump vV 4 t p t p b t p b a t E
burn τE nσv fb αβ fuel 4 αβ τE nσv With (via Lawson-criterion):
τEnσv 12T(0)/3.5MeV and T(0)=26 keV (PROCESS) Continuous Exhaust gas re-injection to artificially . for „clean“ wall b→1, ab ~ 1/3÷1/5 , fb ~ 0.5%, increase 3 fuel~ 490 Pa-m /s recycling R
. for fburn ≥ 10%, (ab ~ 2) tp* ~ 6÷10∙tp → 3 Compression due to re-injection fuel = burn / fb ≤ 26 Pa-m /s He enrichment due to atomic physics
In this case, the DT burn-up fraction can be as much as 10 %, and the DT machine throughput is significantly reduced.
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 38 Particle exhaust modelling
The neutral flow field in the sub-divertor which results from the plasma boundary, the exchange of particles via refluxes, and the vacuum pump capture coefficient, plays a role for the high density scenarios foreseen in DEMO. The EU DEMO divertor development for the first time will be an integrated effort, joining, physicists, material engineers and vacuum engineers. Particle transport to quantify fb is possible.
Pressure maps for two extreme virtual cases: With and without dome
Calculated with the Direct Simulation Monte Carlo (DSMC) code DIVGAS developed at KIT. Collisionless, x=0.3 Collisional, x=0.3 Collisional, x=1.0 S. Varoutis, 2016. Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 39 Summary and Conclusions
. A comprehensive programme is being implemented to advance the DEMO fuel cycle towards a conceptual design in the next 10 years. . This enterprise is following a system engineering approach to make all decisions fully traceable and more easily adaptable, if requirements change. . We propose a new inner fuel cycle architecture to be best fit-to- purpose, driven by the need to minimise inventory and increase burn- up fraction, characterized by 3+1 loops. . It is essential to implement an integrated and holistic view on the fuel cycle.
Chr. Day | IAEA DEMO WS, Karlsruhe | Nov 2016 | Page 40