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Concept development of compact DEMO reactor

IEA/LT Workshop (W59) combined with DOE/JAERI Technical Planning of Tokamak Experiments (FP1-2) 'Shape and Aspect Ratio Optimization for High Beta Steady-State Tokamak'. Concept development of compact DEMO reactor. Kenji Tobita for DEMO Plant Design Team

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Concept development of compact DEMO reactor

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  1. IEA/LT Workshop (W59) combined with DOE/JAERI Technical Planning of Tokamak Experiments (FP1-2) 'Shape and Aspect Ratio Optimization for High Beta Steady-State Tokamak' Concept development of compact DEMO reactor Kenji Tobita for DEMO Plant Design Team Japan Atomic Energy Research Institute Special thanks: F. Najmabadi (UCSD), C.P.C. Wong (GA), K. Okano(CRIEPI)

  2. OUTLINE 1. ABC of Fusion Reactor Study 2. Compact reactor study at JAERI 3. DEMO design study at JAERI Started in 2003 Focus on the possibility of an economically attractive reactor in low-A (= 2-2.9), left behind in fusion reactor study previously - 2 -

  3. 1. ABC of Fusion Reactor Study • Direction of fusion reactor studies • Necessity to pursue economic fusion energy - 3 -

  4. (A) Reactor study seeks for an economic reactor concept Cost-of-Electricity of Fusion COE of other sources SSTR(16 ¥/kWh) CREST(12.5 ¥/kWh) COE (¢/kWh) ARIES-I [1992 JA price basis] ARIES-RS ARIES-AT Design Year - 4 -

  5. (B) In fusion energy, 60~70% of COE is capital cost Costs of CREST (discount rate 2%) To reduce COE 1) Capital cost 2) Thermal efficiency 3) Availability Fuel Operation & maintenance Capital Cc + CF + COM COE (¢/kWh) = Pe • 8760 (h/yr) • fav output Availability - 5 -

  6. (C) Much lower construction cost required for commercialization of FE Fusion share assessment in 2100 Tokimatsu (2003) 4% ~ 1,500 plants Share depends on • COE of other sources • CO2-emission standards, etc. The estimated fusion cost may not be competitive in market - 6 -

  7. Exploration of compact reactor USA JAERI SSTR (1990) Rp = 7 m Najmabadi (2000) A-SSTR2 (1999) Rp = 6.2 m - 7 -

  8. How to compensate for reduced Vp in compact reactor • low recirculating power by high bootstrap • higher thermal efficiency • higher N • higher Bmax ARIES High  to reduce Bmax JAERI Moderate  at high Bmax - 8 -

  9. 2. Compact reactor study at JAERI What led us to low-A compact reactor concept? - 9 -

  10. JAERI’s approach toward compact reactor Rp = 7 m Bmax = 16.5 T N = 3.5 Higher Bmax and N SSTR Rp = 6.2 m Bmax = 23 T N = 4 A-SSTR2 VECTOR - 10 -

  11. High BT can make it heavy SSTR A-SSTR2 TFC weight is significant part of reactor: ~ 45% in SSTR - 11 -

  12. JAERI’s approach toward compact reactor Rp = 7 m Bmax = 16.5 T N = 3.5 SSTR Rp = 3.5 m Bmax = 20 T N = 5.5 Rp = 6.2 m Bmax = 23 T N = 4 A-SSTR2 High Bmax with slim TFC VECTOR - 10 -

  13. Reduce WTFC by small RTF VECTOR Bmax= 19T WTFC = 10 GJ ITER Bmax= 13T WTFC = 41 GJ High WTFC Massive TFC RTF Low WTFC SSTR Bmax= 16.5T WTFC = 140 GJ Slender TFC - 12 -

  14. VECTOR Concept of VECTOR Remove CS to shorten RTF and reduce WTFC Slender CS Low-A 18.2m Physical features • CS-less • Low A (~2.3) high , high nGW, high q - 13 -

  15. Difference between VECTOR and ST Power reactor SC coil VECTOR CS removed A ~ 2.5 w. n-shield conventional Cu coil A = 3-4 VNS ST A ~ 1.5 w/o. n-shield - 14 -

  16. VECTOR, likely to have economical and environmental advantages Economical Power / Weight (kWth/t) Low const. cost Resource-saving Reactor weight (t) - 15 -

  17. Recycle 20,000 Be12Ti Reuse Li12TiO3 LiPb TiH2 10,000 Clearance 0 10,000 Low level Disposal waste (t) Medium level 20,000 SSTR DEMO2001 VECTOR Radwaste of VECTOR, ~4,000 t • LLW, vulnerable point of fusion (usually, ≥ 10,000 t) • PWR ~ 4,000 t Reuse Compactness Recycle Reinforced shield Reinforced shield Clearance Clearance Clearance Resources (t) - 16 -

  18. 8 ARIES-ST 6 CREST VECTOR-opt ARIES-AT N VECTOR ARIES-RS PPCS(D) PPCS(C) A-SSTR2 4 PPCS(A) SSTR PPCS(B) ARIES-I ST conventional 2 1 2 3 4 5 A Remarks on VECTOR What is sure VECTOR concept on TFC system breaks new ground of power reactor design in low-A Open question Is the optimal design point for cost-minimum really A ~ 2.3 for the VECTOR concept? Assumed parametric dependence of N(A) is uncertain. - 17 -

  19. 3. DEMO design study at JAERI • How to fit VECTOR concept to DEMO • Three DEMO options - 18 -

  20. 1 GWe output • Year-long continuous op. • Economical feasibility • DEMO must be compact and have high power density JA Strategy for FE commercialization Commercial. DEMO ITER IFMIF NCT Tech.R&D - 19 -

  21. Tradeoff between size and feasibility Remove CS Install Based on roles of CS, three DEMO options are under consideration Compact + Size Large Rp More feasible + plasma difficult small as possible to reduce WTFC VECTOR concept - 20 -

  22. JT-60U grassy ELM • Shaping triangularity is limited (x ~ 0.3) problematic in • confinement in high n/nGW • suppression of giant ELMs giant ELM Difficulties caused by CS-less will be resolved • Ip rise/control Ex) CS-less Ip ramp-up Exp. (JT-60U, etc) - 21 -

  23. Best effort to raise  w/o CS A far distance between plasma and PF coils makes the shaping difficult. - 22 -

  24. size CS shaping Ip ramp “CS-less” small  x ~ 0.3  Option A 0.7m (dia.) ~10 Vsec “Slim CS” medium x ~ 0.4 ~ 5 MA Option B 1.5 m (dia.) ~30 Vsec “Full CS” large x ~ 0.45 15 MA Option C Three DEMO options challenging conservative - 23 -

  25. Preliminary design parameters - 24 -

  26. Higher Bmax , N margin Adv. n-shield Comparison of Options Option A Option B Option C Full CS CS-less Slim CS Rp~5.1m Rp~ 5.5m Rp~6.4m shaping shaping, Ip ramp 300 Economical VECTOR 200 ARIES-RS A-SSTR2 Pfus / weight (kW/t) SSTR 100 ARIES-ST DREAM Low const. cost ITER 0 20,000 30,000 0 10,000 Reactor weight (t) - 25 -

  27. Key parameters in reactor design Four key parameters : Rp, Bmax, RTF, TF To use BT effectively, the inboard SOL width should be small CS TFC inboard SOL Gap BLK n-shield VV th-insulator Rp Rule of thumb TF 1.3 m RTF TF Bmax Minimum shield thickness enough to protect TFC from neutron damage - 27 -

  28. SOLin, expected to increase with A SOLout ~ defined by the width of heat flux in SOL (assumed to be 3 cm) SOLinusually assumed to be 10 cm but expected to decrease with A. Roughly, - 28 -

  29. Low-A requires a wide inboard clearance, especially for “CS-less” • For A~3 SOLin~ 10 cm, good approx. • For A < 2.5 must be careful about SOLin Determined from the flux surface corresponding toSOLout = 3cm - 29 -

  30. Separate TFC design Selection of design parameterｓ RCS Bmax RTF TF a RP CS TFC - 30 -

  31. 78% of N Wong’s formula (, N) 75% of  Separate TFC design Selection of design parameterｓ RCS Bmax RTF TF N, BT a RP CS TFC - 30 -

  32. Separate TFC design Selection of design parameterｓ 78% of N Wong’s formula (, N) 75% of  RCS Bmax RTF TF N, BT a RP HH (=1.3) CS Check consistency TFC - 30 - IP, qVP, Pfus, PCD, fGW, ….

  33. Optimal design point (“Slim CS”) slender TFC & low-A • Pfus = 3GW 　 ←Penet = 1 GWe • Weight minimum fat TFC & high-A optimal • Optimal range, rather wide –– less dependent on A (or RTF) - 31 -

  34. Breakdown of weight A= 2.8 A= 2.2 - 32 - Weight (t)

  35. Problem in parameter selection: N (A) is not sure Our systems code uses this Wong (based on Miller’s stab.DB) Kessel (ARIES-AT, -RS) 100% BS-driven plasma Our conditions A (A) • N vs  curve, depends on  • N, less dependent on  in our conditions N(A,) -dependence hidden - 33 -

  36. How does the optimal design point change when N is independent on ? Original assumption Alternative assumption to check an impact of N() Based on Wong’s formula Kessel-like (but not incl. dependence of N on A) - 34 -

  37. A ~ 3 optimum when N(A,) = const Original design Constant N N = 4 Optimal Slight increase in Rp optimal - 35 -

  38. Present understanding on DEMO 8 ARIES-ST • With slim CS, DEMO seems to succeed in adopting the VECTOR concept with plasma shaping capability. • At the optimum design point, DEMO can have low-A (= 2.5-3) which is unexplored A in previous power reactor study before VECTOR. 6 CREST VECTOR-opt ARIES-AT N VECTOR ARIES-RS PPCS(D) PPCS(C) A-SSTR2 4 PPCS(A) SSTR DEMO PPCS(B) ARIES-I ST conventional 2 1 2 3 4 5 A - 36 -

  39. Summary VECTOR concept Removes CS to shorten RTF and reduce WTFC , leading to slim TFC system compatible with high Bmax Suggests a possibility of power reactor with A = 2-3 DEMO • CS will be necessary for shaping. • “Slim CS”, i.e., modified VECTOR concept, enables us to envision DEMO with A = 2.5-3 To make the proper footing of DEMO, dependence of N on A and  should be investigated in the range of A = 2.5-4, hopefully through international cooperation - 37 -

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