Presentation on theme: "Divertor Design Considerations for CFETR"— Presentation transcript:
1 Divertor Design Considerations for CFETR Minyou YeUniversity of Science and Technology of ChinaHouyang Guoand Institute of Plasma Physics, Chinese Academy of Sciences2nd International Workshop on CFTER May 30 – June 1, Hefei, China
2 OUTLINE Key PSI issues for CFTER Approaches to CFTER Divertor Design Alternative target concepts
3 OUTLINE Key PSI issues for CFTER Approaches to CFTER Divertor Design Alternative target concepts
4 CFETR-main parameters (CFETR-00-00-03) CFETRITERMajor radius (m)5.56.2Minor radius (m)1.62.0Elongation1.81.85Plasma current (MA)12/10/715 (17)Toroidal field (T)5.3/4.55.3Central density (1020/m3)(1.0)1.0Central temperature (keV)(15)20Confinement time (s)(1.5)3.7Heating Power (MW)50/8073Fusion power (MW)50~200500 (700)Plasma volume (m3)500830Plasma surface area (m2)1-1.6∙1074.0∙105
5 Integral Approach Is Mandatory for the Design of Plasma-Wall Interface Long pulse / steady state / high betaHigh density operationDisrup-tionsCombination of first principles and reactor codesIn vessel compo-nentsFuel cycleSafety & Licensing
7 Main Challenges for Divertor Exhaust the major part of the plasma thermal power, reducing heat flux below limitation of target materials.Remove the fusion reaction helium ash from core plasma while screening impurities from wall.Maintain acceptable erosion rate in terms of reactor lifetime.
8 Selection of High Heat Flux Materials for DEMO Divertor Target Melting Point >2000 KThermal Conductivity >50 W/mKAvailability, CostB. Unterberg, 20th PSI Conf. 2012, GermanyLow/Medium ActivationIrradiatione.g. TRC
9 Major Problem for W is Melting under Transient Heat Load R. Haange, ITER STAC-12,/2012, CadaracheW melting parameter: emelt 50 MJm-2s-1/2Ip (MA)PIN (MW)Stored energy (MJ)Etransient (MJ)lq||omp (m)qtarget(MJ m-2)e (MJ m-2s-1/2)Type7.5407525 380.010.83 8.315.2 213Disruption155035088 1750.0055.78 76.9105 19846.4 8.01.39 1.7477 123Type I ELMDisruptions and unmitigated ELMs are predicted to melt W target for ITER (above).This will also apply to CFTER Disruption & ELM mitigation are mandatory.W Melting detection and RH are required to repair W damage.
10 Time in diverted Phase (hr) Outer divertor ion fluence CFETR Faces Much Greater Challenges than ITER due to Larger Duty Cycle ≥ 0.3 ~ 0.5General migration pattern seen in today’s devices: main wall erosion, convection into divertor depositionR. Pitts, 2012 KSTAR MeetingNo. Pulses (Y )Time in diverted Phase (hr)Outer divertor ion fluenceJET1346640.5~5x1027ITER10.15~1.5x10279 years JET operation ~ 3 ITER QDT = 10 pulses in terms of divertor fluence, important for target erosion and T-retention Much more serious for CFETR
11 OUTLINE Key PSI issues for CFTER Approaches to CFTER Divertor Design Alternative target concepts
12 ITER-Like Vertical Target Structure Inner verticaltarget (W)full W divertorOuter verticaltarget (W)detachment near strike points.Reducing peak heat fluxes near strike pointsDome (W)Pumping slotReflector plates (W)Cassette body (SS)
13 ITER-Like Vertical Target Structure Subsystems to Integrate in lower part of vacuum vessel:divertor cassettes with plasma facing components- cooling system to exhaust plasma and neutronic heat depositioncryopumps to exhaust neutralized gasdiagnostics to monitor plasma re-attachmentFuelling system to promote plasma detachment / mitigate re-attachmentRH equipment to maintain components and maintenance operationsSystem integration : bring together all the component subsystems into one system ensuring that the subsystems function together as a system
14 SD or DN ? Advantages of DN: Larger plasma-wetted area, facilitating power exhaustAllowing pumping via both top and bottom, facilitating particle exhaustNaturally large triangularity, facilitating advanced tokamak operationAdvantages of SN:Accommodating large plasma volumeMaximizing TBR
15 OUTLINE Key PSI issues for CFTER Approaches to CFTER Divertor Design Alternative target concepts
16 Snow-Fake Divertor to Reduce Peak Heat Load “SNOWFALKE”: USING SECOND-ORDER NULL OF POLOIDAL FIELD TO IMPROVE DIVERTOR PERFORMANCEFeatures of snowflake divertors• Larger flux-expansion near the PF null• Increased connection length• Increased magnetic shear in the pedestal region (ELM suppression)• Modified blob transport (stronger flux-tube squeezing near the null-point)• Possibility to create this configuration with existing set of PF coils on the existing devices(TCV, NSTX, DIII-D….)• Possibility to create “snowflake” in ITER-scale machines with PFcoils situated outside TF coilsD. D. Ryutov, PoP 14,DIII-D
17 Snow-Fake Divertor to Reduce Peak Heat Load NSTX Snowflake Divertor V.A. Soukhanovskii, NSTX-PAC 31, PPPL, April 17-19, 2012Reduction from 3-7 MW/m2 to MW/m2 between ELMs; Reduction from ~20 MW/m2 to 2-8 MW/m2 at ELM peak.
18 Snow-Fake Divertor to Reduce Peak Heat Load NSTX Snowflake Divertor V.A. Soukhanovskii, NSTX-PAC 31, PPPL, April 17-19, 2012Reduction from 3-7 MW/m2 to MW/m2 between ELMs; Reduction from ~20 MW/m2 to 2-8 MW/m2 at ELM peak.
20 He-cooled modular divertor with jet cooling (finger concept, KIT) High Temperature Operation?[P. Norajitra et al., Fus. Eng. Des. 83 (2008) 893.]He-cooled modular divertor with jet cooling (finger concept, KIT)
21 Approaches to CFETR Divertor Design Optimize Magnetic configurations and target geometry :1. Optimize Magnetic configurations --- physics design group2. Design target geometry3. Calculate distributions of particles and heat using SOLPS code4. Optimize target geometryStart engineering conceptual design:1. Preliminary design on target, heat sink, support structure, cooling structure and cassette body…2. Electromagnetic analysis of the divertor components (DINA/MIT+ANSYS)3. Neutron volumetric heating calculations (code?)4. Thermo-mechanical analysis and structure analysis (ANSYS)5. Optimize divertor structure design
22 SummaryStart to design ITER-like divertor; further look into other new divertor configurations, e.g., snowflake, isolated divertor configurations.Start to design single null divertor; examine impact of DN on fusion gain and TBR