1. Design Study of Fusion DEMO Plant at JAERI Japan Atomic Energy Research Institute K. Tobita, S. Nishio, M. Enoeda, M. Sato, T. Isono, S. Sakurai, H. Nakamura,S. Sato, S. Suzuki, M. Ando, K. Ezato, T. Hayashi, T. Hayashi, T. Hirose, T. Inoue, Y. Kawamura, N. Koizumi, Y. Kudo, R. Kurihara, T. Kuroda*, K. Mouri, Y. Nakamura, M. Nishi, Y. Nomoto, J. Ohmori, N. Oyama, K. Sakamoto, T. Suzuki, M. Takechi, H. Tanigawa, K. Tsuchiya, D. Tsuru ( * Kawasaki Heavy Industries) ISFNT7, Tokyo, May 23-27, 2005 S6-14-O-02

2. OUTLINE 1.Background 2.Concept of DEMO 3.Features of DEMO plant 4.Next steps in design study 2

3. 1. Background IFMIF Commercial. Economy Tech.R&D Satellite tokamaks Satellite tokamaks ITER Situation of JA strategy for FE commercialization Middle of this century Technology 3 JA strategy still argued in AEC, not settled Point of argument: ONE or TWO steps to commercialization? Technology Economy 2 steps? 1 step? DEMO stage

4. Place of DEMO competitive Technology SSTR (1990) Tech. feasible as DEMO Not competitive in market (15 yen/kWh) VECTOR (2001) Commercial reactor with advanced tech. Compact & economic. 4 advanced conservative expensive Economy DEMO Seek a DEMO concept competitive in market with foreseeable tech.

5. Philosophy for DEMO design SSTR (1991) VECTOR (2001) Low-A DEMO Modify “VECTOR concept” to reduce tech. requirements without losing compactness Comparable in tech. level Design compromise of VECTOR, based on foreseeable technologies 5 Technology advanced conservative expensive Economy (Exp. in low-A scarce. Needs support by satellite tokamak) competitive ex. NCT

6. VECTOR concept: superconducting low-A w/o CS coils Aspect ratio Remove CS R TFC giving B max ( magnetic energy ) Slender TFC system (elongation ) High  Compact, low-A & high   with slender TFC A ~ 2-2.5 6

7. 2. Concept of DEMO 7 VECTOR Difficulties plasma shape control triangularity (HH, ELM contr) positions plasma current ramp-up Advantage very compact (light) (null point, div. hit point) CS-less

8. 2. Concept of DEMO VECTOR Difficulties plasma shape control triangularity (HH, ELM contr) positions plasma current ramp-up Advantage very compact (light) (null point, div. hit point) CS-less DEMO(J05) Slim CS reduced but still compact improved but still limited R cs = 0.7m,  cs = 38 Vsec resolved compromise induce 3.8 MA 7 I cs 10 MA/m

9. RcsshapingI p -ramp CS-less -limited- Slim CS 0.7mgood~ 3.8 MA Full CS 1.5mgoodflattop Impact of CS on reactor weight ~40Wb 170Wb Systems code analysis Conditions: TFC stress 800 MPa same ,  N margins, fusion output 3 GW, etc. to find the minimum reactor weight of the following cases DEMO weight ==> constr. cost DEMO(J05) 8 Considering tech. feasibility and weight, “Slim CS” is a good compromise.

10. 3. Features of DEMO plant  Nb 3 Al S.C. 12 TF coils, B max = 16.4 T  Blanket Li 2 TiO 3 / Be 12 Ti (pebble) F82H / pressurized water  Current drive NBI : 1.5 MeV ECRF : 170-190 GHz R p = 5.5m, a = 2.1m, A = 2.6 B T = 6T, I p = 16.7MA,  N = 4.3, P fus = 3 GW  Divertor W monoblock / F82H cooling tube  Maintenance Sector maintenance 9 Extrapolation of TBM(JA) Firm support of BLK / high availability

11. (1) Light reactor weight, leading to a reduction of construction cost Reactor weight : DEMO(J05) ~17,500 tons ARIES-RS, ARIES-ST SSTR,A-SSTR2, ITER > 22,000 tons 10

12. (2) Seemingly  N (=4.3) is high, but likely to have a large  N margin Theoretically, higher  N expected in lower A Margin to LL-S  N Margindesigns ~0% A-SSTR2 ~10% SSTR, PPCS(D) ~20% DEMO(J05), PPCS(C)  N limit for 100% BS-driven plasma ex., Lin-Liu / Stambaugh formulation 11 Tough constraint

13. (3) DEMO requires technologies comparable to SSTR difficult Magnet Plasma Vertical stability ballooning stability Confinement Density Maximum fieldTFC magnetic energy 12

14. 4. Next steps in design study Refine divertor concept – consistent solution of shape control (  ), radial build and heat/particle control study startup and shutdown scenarios – overdrive in startup / shutdown by impurity gas puff Provide feasible maintenance scheme – sector transport / hot cell maintenance Assess supercritical CO 2 as alternative coolant – Advantages : Compact turbines, compatible with Be, easy separation of T, etc. – Disadvantage : organic compounds by CO+T 2 reaction Major change from the ITER scheme 13

15. Presentations on DEMO MAY 23 (MON) M. Nishi S1-01-0-01 Tritium accountancy MAY 24 (TUE) H. Nakamura P2-20 Tritium penetration MAY 26 (THU) T. Isono P5-27 Magnet design M. Sato P5-30 Core and divertor concept S. Nishio P5-29 Reactor structure T. Inoue P5-32 NBI system K. Sakamoto P5-28 ECRF system 14

16. Summary  A compact low-A (A ~ 2.6) reactor is under consideration at JAERI as a DEMO concept.  DEMO has a slim CS for plasma shape control as a compromise of the CS-less VECTOR concept. Yet, the reactor weight is still light compared with other tokamak designs.  Required technologies seem comparable in difficulty level to those for SSTR. 15