Overview of Reactor Design Studies at JAERI K. Tobita Japan Atomic Energy Research Institute Japan-US WS 2005 JAN 11-13, Tokyo

Outline 1. Low-A Compact Reactor, VECTOR 2. DEMO Plant Design 3. Reduction of Waste

1. Low-A Compact Reactor, VECTOR References: [1] S. Nishio et al., 19th Fusion Energy Conf., Sorrento, IAEA-CN- 94/FT/P1-21 (2002). [2] S. Nishio et al., 20th Fusion Energy Conf., Vilamoura, IAEA-CN- FT/P7-35 (2004). [3] K. Tobita et al., Plasma Phys Contr. Fusion 46 (2004) S95. [4] K. Tokimatsu et al., WEC 2004, Sydney.

Reactor Design Studies at JAERI = SSTR series = Low-A approach

SSTR series aimed at higher power density with high B max, yet this does not always make the reactors compact SSTR 16.5 T A-SSTR 19 T A-SSTR2 23 T SSTRA-SSTR2 P fus (GW) R p (m) B max / B T (T)16.5 / 923 / 11 W TFC (GJ) TFC Weight (t)11,20014,640 Coil system of A-SSTR2

TF Coils of “VECTOR” concept Small R leads to a reduction in W s of TFC. ITER B max = 13T W s = 41 GJ SSTR B max = 16.5T W s = 140 GJ VECTOR B max = 19T W s = 10 GJ Slim TF coil system reducing supporting structure material stabilizing material R

Parameters of VECTOR No CS Structural material: SiC/SiC Breeding material: LiPb Superconductor: Bi-HTS 18.2m RpRp 3.2 mIpIp 14 MA a1.4 m NN 5.5 A2.3HH1.3  2.35n/n GW 0.9 B max 19 TP fus 2.5 GW BTBT 5 TPnPn 5 MW/m 2 VEry Compact Tokamak Reactor

Considerations on A  Low-A Advantages : high  n GW = I p /  a 2 high   To adopt superconducting TF Space needed to install shield, leading to A =  A NN Plot of Wong’s formula VECTOR

( A~4 ) CS-less ( A~ 1.5 ) ( A~ ) Copper coil SC coil ST Nishio, IAEA2004 Difference between VECTOR and ST No shield required Because of Joule loss, HOPELESS as power source VECTOR PROMISING as power source Shield required Conventional

Features of VECTOR Likely to have economical and environmental advantages Reactor weight (t) Power / Weight (kW th /t) Low const. cost Resource-saving Economical

Strategy on Waste of VECTOR Introduce “clearance” “Clearance” waste, regarded to have negligible waste hazard, would be treated as industrial waste. Can be put in recycle market Radwaste, less dependent on reactor size. To take advantage of “compactness”, we must treat the radwaste as useful resource. “Reuse” “Recycling” Remote precision machining, installation, Impurities in recycle materials, cost. Use again in next reactors for the same purpose w/o recycle processes difficult Neutron shield (TiH 2 ) Liquid breeder (LiPb) favorable Reusable after several year-cooling

Impact of Reuse 12,100 tons clearance reuse radwaste Disposal in land Resource Weight (t) LiPb TiH 2 Clearance Reuse Reuse of part of radwaste can reduce the amount of disposal waste to as low as ~4,000 t (PWR level).

Other features of VECTOR  Excellent  -particle confinement expected due to strong TF ripple damping  Extremely low CO 2 emission in life cycle : 3.2 g-CO 2 /kWh (cf. DEMO2001: 5 g-CO 2 /kWh) Critical issues Shaping (low  ) Controllability (I p, separatrix) Related with CS-less

2. DEMO Plant Design References: To appear in ISFNT-7 (Tokyo, 2005 May) [1] K. Tobita et al., Overview [2] M. Sato et al., Core and divertor [3] T. Isono et al., Magnet [4] S. Nishio et al., Blancket and maintenance [5] K. Sakamoto et al., ECH/ECCD [6] T. Inoue et al., NBI [7] H. Nakamura et al., In-vessel tritium inventory [8] M. Nishi et at., Tritium accountancy [9] T. Hayashi et al., Advanced shield materials

Requirements on DEMO TBR > 1 P e net ~ 1 GWe (P fus ~ 3 GW) One-year continuous operation Power core as small as ITER’s ~1 GWe power generation in 2030’s Show a way for economical power production Technical requirements –– Discussions in subcommittee of AEC –– Strategic requirements

VECTOR can be a key concept of DEMO but …  Reconsider pros and cons of CS-less  Available materials: Needs compromises in technologies Ferritic steel (F82H) Pebble bed breeder Nb 3 Al superconductor CS-less plasma, unexplored experimentally

CS-less, seems problematic I p ramp / control Unproven but the technology developing (JT-60U, etc.) Plasma shaping, low  (~0.1) Problematic in HH in high f GW and ELM control Giant ELM Grassy ELM Div. Heat (MW/m 2 ) 0.5 s JETJT-60U n/n GW HH Shinya, this WS Y. Nakamura, this WS

Tradeoff on CS Based on the roles of CS, three DEMO options are under consideration CS RemoveInstall Compact Large R p More feasible + difficult + Size plasma

Design Options Power / Weight (kW th /t) Reactor weight (t) “Full CS” R p ~ 6.4m, A ~ 2.8 Option C CS: 30 Vsec “Slim CS” R p ~ 5.5m, A ~ 2.4 Option B 10 Vsec,  ~ 0.4 Option A “CS-less” R p ~ 5.1m, A ~ 2.3  ~ 0.1

Parameter Selection CS-less Slim CS Full CS  Assumes conservative  78% of Wong’s  N (A,k)  Gives B max (R TF ) Determined for Nb 3 Al  Systems code analysis changing R TF and R p Slim CS case Sato, this WS

Tentative Parameters Option AOption BOption C R p (m) a (m) A   ~ B T /B max (T)4.6 / / / 13.3 I p (MA) q NN HH1.3 n/n GW P fus (GW) P n (MW/m 2 ) Q Weight (tons)15,80017,30022,700 CS-lessSlim CSFull CS

Key Issues in DEMO Design Study TFC design based on the VECTOR concept BLK design to withstand EM force of fast disruptions Reduction of T permeation in PFC Maintenance scheme to foresee high availability Achieve high current density by reducing structural and stabilizing materials Assembly of small BLK casings to withstand ~30ms disruption TBR expected to be critical W coating on all over the BLK surface Sector transport and hot cell maintenance –– challenging to adopt in DEMO H. Nakamura, this WS Nishio, this WS

3. Reduction of Waste References: [1] K. Tobita et al., J. Nucl. Mater (2004) [2] K. Tobita et al., SOFT 2004, Venice.

Why Waste Reduction? Fission (1.1GWe PWR) Fusion Catch phrase Low environmental load Environmentally more favorable than fission High level waste200 tons/30y Nothing Low level waste4,100 tons ~9,000 tons (DEMO 2001) metal Fusion is vulnerable to LLW.

Waste Assessment at JAERI Not systematic, but various waste assessments carried out SSTRIntroduced “clearance” to reduce radwaste A-SSTR2 Investigated an impact of “reinforced shield” to reduce further DEMO-2001 Assessed possible tailoring of chemical composition and impurity content of F82H to avoid deep land burial VECTOR Studied an impact of “compactness” of reactor and “reuse of radwaste” D 3 He Compared disposal waste between DT and D 3 He reactors

Shallow land burial Deep land burial Waste Management Scenario Decommission 50y cool Classification Clearance waste Radwaste Low level Medium level Recycle market or disposal as industrial waste Potential resources Reusable waste Reuse in next generation reactors Shield, breeder Disposal waste

Summary of Waste Assessment 0 10,000 20,000 Clearance Low level Medium level SSTR DEMO2001VECTOR Clearance Reinforced shield Recycle Reuse Compactness Disposal waste (t) Resources (t) Reuse LiPb TiH 2 Recycle Be 12 Ti Li 12 TiO 3 Waste from fusion can be as low as ~4,000 t, being the same as that from PWR

Strategies/Technologies for Waste Reduction  Reinforced shield Conventional shield Minimum shield thickness to provide adequate TFC operation radwaste Clearance, potentially Reinforced shield Shield thickness enough to clear the ex-shield components  Separation technique of TF and PF coils TFC of VECTOR Inhomogeneous waste such as TFC does not qualify for clearance. This is to avoid an accumulation of a particular material contained in the waste beyond the clearance level in the recycle process.  Reuse of radwaste Fusion reactor produces about 10,000 t of LLW. Reuse/recycle of radwaste will be necessary to improve PA. Shield and liquid breeding material, reusable.

Comparison of waste from D 3 He and DT reactors Ｄ 3 He Reactor DT Reactor 2.3 GW HH = 2  N = GW HH = 1.3  N = 5.5

Summary  VECTOR has economical and environmental advantage over conventional reactors.  DEMO design study at JAERI is in progress. Prime option : “Slim CS” R p = 5.5m, A= 2.4…  Waste reduction assessed for different JAERI reactor designs. Waste could be as low as ~4000 t (PWR level) for VECTOR.