ILE Osaka Activities on reactor design for fast ignition T. Norimatsu, H. Azechi, Y. Kozaki, Y. Fujimoto, T. Jitsuno, T. Kanabe, R. Kodama, K. Kondo, N. Miyanaga, H. Nagatomo, M. Nakatsuka, H. Shiraga, K. A. Tanaka, K. Tsubakimoto, M. Yamanaka, R. Yasuhara, and Y. Izawa, Institute of Laser Engineering, Osaka University, 2-6, Yamada-oka, Suita, Osaka , Japan, ; Presented at Japan-US workshop on Laser IFE March 21-23, 2005, GA. San Diego, USA

ILE Osaka Outline Introduction –IFE plant Design Committee –Roadmap Chamber concept –KOYO-F with a wet wall Protection scheme for the final optics Scenario for fuel loading and injection Summary

ILE Osaka IFE plant design committee was organized under collaboration of ILE, Osaka and IFE Forum. Chairman: K. TomabechiBlue; from company Vice chairman: Y. Kozaki, T. Norimatsu Black; form university Supervisor group K. Ueda, M. Nishikwam K. Okano, T. Yamanaka, A. Nosaka, Y. Ogawa, H. Kan, A. Koyama, T. Konishi, N. Tanaka, A. Sagara, Y. Hirooka, H. Nakazato, Y. Soman, H. Azechil K. Mima, S. Mori, Y. Nakao, N. Miyanaga, M. Nishikawa, K. Tanaka Plasma working group H. Azechi, H. Shiraga, K. Mima, R. Kodama, Y. Nakao, H. Nagatomo, S. Ishiguro, T. Jozaki Laser working group N. Miyanaga, Y. Suzuki, Y. Owadano, T. Jitsuno, M. Nakatsuka, H. Fujita, K. Yoshida, H. Nakano, T. Kanabe, H. Kubomura, Y. Fujimoto, T. Tsubakimoto, T. Kawashima, H. Furukawa, J. Nishimae Target working group T. Norimatsu, A. Iwamoto, M. Nishikawa, M. Nakai, H. Yoshida, T. Endo System working group Y. Kozaki, K. Okano, A. Sagara, Kunugi, T. Konishi, H. Furukawa, M. Nishikawa, Y. Sakawa, Y. Ueda, K. Hayashi, Y. Soman, M. Nakai

ILE Osaka Fast ignition can reduce the required laser energy because of the smaller PV work. rhrh  h <  c /4 rcrc rcrc r h < r c /4  h ~  c Fast heating needs petawatt laser. Critical issue is energy coupling.

ILE Osaka Actual energy and power of heating laser required for fast ignition after S. Atzeni, (Phy.Plasmas’99) Assuming high energy electron range ;  d = 0.6 g/cm 2 E h = 140{  /(100g/cc)} kJ P b = 2.6{  /(100g/cc)} -1.0 PW I b = 2.4X10 19 {  /(100g/cc)} 0.95 W/cm 2 r b = 60{  /(100g/cc)}  m E L = kJ

ILE Osaka Roadmap toward laser fusion power plant by fast ignition

ILE Osaka Outline Introduction –Reactor Design Committee –Roadmap Chamber concept –KOYO-F with a wet wall Protection scheme for the final optics Scenario for fuel loading and injection Summary

ILE Osaka Basic specification of KOYO-F with liquid wall Plant with 5 modular reactors –Electric output power1200 MW (250MW for laser) Laser1100kJ+100kJ Rep-rate4 Hz x 4 Operation power250 MW Target gain160 Blanket gain1.15 Thermal output power770 MW/reactor Conversion efficiency40 %

ILE Osaka Wet wall reactor for fast ignition scheme KOYO-F has 1.1 MJ, 32 beams for compression, 100kJ heating laser and two target injectors. Thermal out put 200 MJ/shot Rep-rate 4 Hz KOYO-F has vertically off- centered irradiation geometry to simplify the protection of ceiling.

ILE Osaka Layout of heating laser makes new issue. 30 compression beams + heating laser 32 compression beams + heating laser (0,0,0) (1,0,0) In the case of (0,0,0) layout, 80 % energy of neighboring 3 beams irradiates the cone. Power control is necessary.

ILE Osaka In the previous cascade reactor, chamber clearance would be the critical issue. Ten kg of LiPb will evaporate by a microexplosin. Top-open geometry will form an upward flow, which would make the clearance time longer.

ILE Osaka The first wall is pours metal plates that are saturated with liquid LiPb and are tilted to make a down flow after collisions at the center. Average gas pressure assuming pure laminar flow Y. Kozaki et al., IAEA, FEC Mixing of surface flow is necessary to reduce the vapor pressure before the next laser irradiation.

ILE Osaka To keep the surface wet, pours metal will be used. Pours metal allows penetration of Liquid LiPb, resulting the surface is always kept wet. This scheme can save the electric power to circulate the heavy liquid LiPb. 1MW for the surface flow 0.3 MW for blanket. Ferrite 1m 0.1m 400 o C 0.8m 3 /s 400 o C 2.1m 3 /s 500 o C 550 o C V av =0.4m/s V av =0.1m/s  t=1.3 o C/shot  t=0.5 o C/shot Average flow rate 0.1 m/s 0.2 m/s

ILE Osaka For laser and utilities 250 MWe Concept of cooling system For 1st wall Electric power 1450 MWe T -> E 41 ％ Electric output 1200MWe Turbin e By Sohman JNC Generator Steam generator Blanket 400 ℃ 550 ℃ 500 ℃ Blanket Liquid wall Reactor 4 reactors (LiPb) 3.1×10 ７ kg/h (0.83m ３ /s) 8.38×10 ７ kg/h (2.22m ３ /s) Fusion yield (with blanket) 770MWt (870MWt),750MWt,150MWt

ILE Osaka Outline Introduction –Reactor Design Committee Chamber concept –KOYO-F with a wet wall Protection scheme for the final optics Scenario for fuel loading and injection Summary

ILE Osaka P 1 Motion of ablated plume Reference H. Furukawa, Y. Kozaki, K. Yamamoto, T. Johzaki, and Kunioki Mima, ‘Simulation on Interactions of X-Ray and Charged Particles with First Wall for IFE Reactor ‘ Submitted to Fusion Engineering and Design (2004). Simulation result Initial condition for analytical model 140m/s

ILE Osaka P 4 Saturation and Quenching of Pb plume in spherical isothermal expansion A saturation wave, and a quenching wave propagate from outside to the center. When the saturation wave passed by, condensation starts. (The temperature decreases.) When the quenching wave passed by, condensation ends. ( The density is too low)

ILE Osaka Protection scheme of final optics by synchronized rotary shutters 0.05Torr Xe or D 2 The rotational speed of the 1st disk is ~1000 rpm.

ILE Osaka Simulation of liquid wall reactor started. LiPb in 2004

ILE Osaka No deposition of LiPb was observed on witness plate in 0.1 Torr H 2.

ILE Osaka Pb vapor whose initial speed of 100 m/s can not reach final optics in 0.1 Torr buffer gas. 0.5m 100m/s Pb get into the duct at the rage of 5 mg/shot. -> 473 kg/year !! Cleaning is necessary.

ILE Osaka If evaporated vapors collide at the center and lose the momentum, the rep-rate would be limited. Offset irradiation would be the solution. In the case of LFE reactor, the fire position is not necessary at the chamber center.

ILE Osaka Outline Introduction –Reactor Design Committee Chamber concept –KOYO-F with a wet wall Protection scheme for the final optics Scenario for fuel loading and injection Summary

ILE Osaka Two or three injector will be used because it seems difficult to load fragile foam targets into the sabots at 4 Hz Pneumatic acceleration with 80K He and fine adjustment by coils V=300+/-1m/s 2 Hz operation

ILE Osaka Model target Foam insulated Solid DT with LiPb cone whose inner surface is parabolic Shell Outer insulator 250mg/cc 200  m Gas barrier 2  m Solid DT 200  m Cone LiPb 0.5 ｇ Issue; Fabrication of cone with LiPb How to fill the fuel in short time?

ILE Osaka Thermal cavitation technique is the solution for fuel loading in batch process. Thermal cavitation method can fill liquid fuel into foam layer without feed-back control. Required condition is; Diameter of foam shell ＞＞ Vent port ＞ Feeder port ＞＞ Cell size of foam

ILE Osaka Demonstration of thermal cavitation with hemi foam shell Liquid D2 was evacuated by a heater outside the pot.

ILE Osaka Step 1 Saturation of foam with liquid DT

ILE Osaka Step 2 Evacuation by laser heating

ILE Osaka Step 3 Finish

ILE Osaka Extra fuel (5.4%) will be loaded due to the meniscus formed between cone and shell. Liquid fuel in outer meniscus will move to inside after stopping the laser irradiation. There is another extra liquid in the meniscus formed between the cone and inner surface of the foam layer. These extra fuel will compensate the shrinkage of hydrogen during freexing(15%)..

ILE Osaka Fuel loading system by thermal cavitation method. Not to scale Tritium inventory 100g

ILE Osaka When gun length is 10 m, residual gas pressure at the next injection is estimated to be 0.03 atm, which may disturb cryogenic layer. For simplification, the gas is initially stationary and pumping starts at both ends at t=0. P evac pressure in tube at the next injection t evac time needs for evacuation Our estimation indicated that the pressure of residual gas at the next injection is 0.03 atm. Thermal load for cryogenic target? Needs differential pumping system This work is supported by Dr. T. Endo of Hiroshima Univ..

ILE Osaka

The size of revolver needs about 60 cm in the diameter The thermal load due to propellant gas is ~1.2 kW. Heat exchange rate with liquid He is ~ 0.1 W/cm 2. The diameter of revolver is estimated to be 60 cm, which makes hard to obtain high rep- rate. 4 Hz -> 2 Hz x kW 60 cm Estimation of thermal load 1

ILE Osaka 1 MW of electric power will be consumed to operate a pneumatic injector. 280W 470W to cool the revolver ( x2)×100=120 kW 66 kW to cool thermal radiation 66 ×10=660 kW 160 kW to cool targets and egg plates 200kW In total 980kW / injector Estimation of thermal load 2

ILE Osaka

Summary Conceptual design of KOYO-F is continued basing on a wet wall. Critical issue of wet wall seems chamber clearance to achieve 4 Hz rep- rate. In a future laser fusion reactor, final optics at the end of 30m-long beam duct can be protected from metal vapor using a rotary shutter and 0.1 Torr hydrogen gas. The vapor (v=100m/s) will stop within 6m from the entrance of beam port. Fuel loading in mass production process will be carried out by thermal cavitation technique. Accuracy of fuel loading (goal, < 1%) is future issue.