pB11-reactor: trends and physics issues!
S.Putvinski! For TAE team! OUTLINE!
!! New cross section for pB11! !! Optimization of plasma and device parameters! !! Physics issues for reactor! !! Gas/recycling control! !! Plasma fueling! !! Ash control requirements! !! Energy conversion!
Presenter: First Last! Privileged and Confidential! 2! TAE goal is development of pB11 fusion!
1H + 11B = 4He + 4He + 4He! ! !! Advantages:! !! No neutrons (almost), no neutron damage of the wall! !! No Tritium breeding is required! !! Fuel is benign and widely available (11B abundance 80%)! !! Low activation of plasma facing components! !! Difficulties:! !! High plasma temperature is required! !! The required n! is larger than for other fuels! !! Sensitive to He ash!
Presenter: First Last! Privileged and Confidential! 3! pB11 cross section and " spectrum has a long history!
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!! The most cited study is: H. Becker, C. Rolfs, H. Trautvetter, Z. Phys. A 327 (1987) 341.!
Presenter: First Last! Privileged and Confidential! 4! New pB11 cross sections from TUNL!
!"#"$%&'()&*+),+'-"+."+/01234+54)&67*+89::+ + $"$,';)*+),+'-"*+<=71"+>),"+?*+@A@B89::C8@+ + DE%F',)F+&)'GH34+&',)+G'-G0-'H341+3I+%?::?J*+ !"K"+$2(3&'*K"L"+M)--)&*+'()*"+,-.*/0-12"3,4"5+67!" .04)*+89:N+
!! pB11 cross section have been re-measured at TUNL facility (uncertainty 3.5%). It is higher than previously assumed! !! "-particle spectrum is also different from widely accepted (after H. Becker, et al., Z. Phys. A 327 (1987) 341)!
Presenter: First Last! Privileged and Confidential! 5! pB11 fuel has good reactivity!
11 !! Maximum fuel reactivity, <#v>*Efusion, of pB is high:! !! Only 3 times less than DT, ! !! Comparable with DHe3, ! !! 5 time higher than DD!
!! pB11 fuel requires higher temperature to achieve high reactivity!
Presenter: First Last! Privileged and Confidential! 6! pB11 can have higher Q than previously concluded!
!! Ignition of pB11 fuel is possible with new cross sections! !! Optimum ion temperature is in the range 200-400 keV!
Presenter: First Last! Privileged and Confidential! 7! Neutral Beam Driven Field Reversed Configuration!
! !! FRC opens a unique pass to high temperature plasma!
!! Very low magnetic field -> low synchrotron radiation!
!! Confinement scaling predicts plasma confinement time increases with plasma temperature!
n! ~ (rB)"T$
Presenter: First Last! Privileged and Confidential! 8! Two step optimization of design point!
!! Optimization of plasma parameters to estimate Q !
!! Optimization of device parameters!
Presenter: First Last! Privileged and Confidential! 9! 0D model !
!! Power balance equations for ions and electrons!
!! Total power balance to evaluate NB power:!
Pfus + PNB = Pbrem + Pconv
!! Electron power balance to evaluate Te:!
Pfus,e + Paux,e + Pie = Pbrem + Pconv,e!
!! Convective loss: Pconv = n!T/"p with !i = 1.5, !e = 5.5
Presenter: First Last! Privileged and Confidential! 10! Fusion gain, Q!
2 !! All powers ~ ni -> density drops from balance equations!
!! Essential plasma parameters! !! Ion temperature, Ti! !! Boron concentration, CB = nB/ni! !! He ash concentration, CHe = nHe/ni! !! ni!p! ! !! Ti and CB are optimized to maximize Q = Pfus/Paux!
!! Optimum values: Ti ~ 330 keV, CB ~ 0.12 -0.14.!
Presenter: First Last! Privileged and Confidential! 11! Maximum Q of pB11 fuel vs n!p and CHe!
!! There is lethal He concentration, CHe, for each Q! !! Ignition is possible but requires very high n!p
Presenter: First Last! Privileged and Confidential! 12! Q = Pfus/PNB > 3 is required for Plasma Energy Generator (PEG)!
K3,)-+-3'F+ Pel = PNB{(Q+1)!th -1/!NB – !hotel} !! To get net electrical power Q > 3 (at %th = 40%, %NB = 0.7, %hotel = 0.15)! Presenter: First Last! Privileged and Confidential! 13! Optimization of PEG device! #&731,',+S'--+ O)0,&34+1=2)-F246+ $#+G32-1+ T'G00P+;)11)-+ =' 4+ /2&1,+S'--+ !! 80% of fusion power in form of 100-200 keV photons from Bremstrahlung! !! 0.1% of fusion power in from of 1-2 MeV neutron from secondary reaction "(B11,n)N14! !! Constrain: & = shielding + other shells + gaps ~ 0.4-0.5 m! Presenter: First Last! Privileged and Confidential! 14! Optimization of PEG device! !! At fixed temperature n ~ B2 and fusion power scales as:! ! 2 3 2 4 3 Pfus ~ Vpln ~ rs n E ~ B rs E !! Increase of magnetic field improves economics! !! Field is limited by SC technology! !! Plasma radius, rs > 2#, for efficient use of magnetic field! Presenter: First Last! Privileged and Confidential! 15! Stability constrain S*/E! !! Traditional FRC’s have density limit S*/E < 3.5! 1/2 1/2 S*/E~ rs/$LE ~ rsB/ET ~ n /E ! 2 !! Economics drives to higher fusion power density, pfus ~ n , i.e. to density limit! !! TAE confinement scaling predicts n"p ~ rTB ~ S*T! ! !! The higher S* -> the larger n" , the larger power density -> the better economics !! Reactor shall operate close to the density limit. Plasmas with large elongation are preferable for the reactor! Presenter: First Last! Privileged and Confidential! 16! Plasma stability limit! !! Tilt mode stability S*/E < 3.5 !! Present database limited by E < 10, S* < 27 !! NB driven FRC’s with high pressure of beam ions are expected to be more stable. ! Presenter: First Last! Privileged and Confidential! 17! DEMO-lite, DEMO-E, and Commercial PEG! !! "#$%!&'()*! "#$%&#! +,#-! ,'./0.!1.2(3/4!1/!506! 9"U9+ :"89+ :"8N+ $.78*9:!;*'2!5<6! @"9+ @"9+ U"9+ =3/(>8!?>@*1!5$A6! BC! 899+ :999+ D! V+ N"89+ W"99+ EF!?>@*1!(8!?'./0.!5$A6! X9+ X9+ :X9+ E*)!*'*:)1(:.'!?>@*1!5$A6! OY+ GB! GHC! LK G I*J3(1*2!!8!?!5KC !/M0 6! :9+ V9+ X9+ +>8;8*0*8)!0.17(8!N>1! [C #34\4)P)4,+P'&624+]+!%B1G'-246C^!%+B&)_02&)FC+ Presenter: First Last! Privileged and Confidential! 18! DEMO-lite (ITER type)! !! Demonstration of Q > 1(3) with pB11 fuel at pulse length up to 500 s! !! No electrical power production! !! Does not require high efficiency of NB’s! ! !! Cold, water cooled wall! !! Assumed parallel development of efficient NB’s, hot wall technology, direct energy convertors, etc! Presenter: First Last! Privileged and Confidential! 19! DEMO-lite! K26=+)4)&67+`)'P1+ $#+P'64),1+ >3S+)4)&67+`)'P1+ #&731,',+ 5a%'4F)&+ Presenter: First Last! Privileged and Confidential! 20! DEMO-lite plasma parameters! R V : L)_02&)F++4!%+B1^PbVC :"95Q88 X"N5Q8: Y1=+G34G)4,&'H34+BcC! N! :9! ! ! ! d34+F)412,7*+42+B:9b89PeVC :"X8 :"XX /01234+%3S)&+B!MC ! XN! XX! L'F2'H34+%3S)&+B!MC ! XA ! XA ! #34;)GH;)+-311+B!MC! :8! VU! <&3,34+`)'P+%3S)&+B!MC! :9"U! 88"N! ?3&34+`)'P+%3S)&+B!MC! X"V! N"U! L/+%3S)&+B!MC ! 9 ! :N ! #34\4)P)4,+HP)+B1C ! :99! V:! #34\4)P)4,+P'&624! [C+ N"@! :U! $[^5 ! V ! V ! $[ ! XV! XV! ! ! ! [C !#34\4)P)4,+P'&624+]+!%B1G'-246C^! %+B&)_02&)FC+! Presenter: First Last! Privileged and Confidential! 21! Physics issues for the reactor! !! Gas/recycling control! !! Plasma fueling! !! Ash control requirements! !! Energy conversion! Presenter: First Last! Privileged and Confidential! 22! Core plasma fueling is required! !! Hydrogen can be fueled solely by NBs! !! Boron core fueling must to be developed. Viable candidates are! !! Injection of Compact Toroids (CT)! !! Boron ion beams (developed earlier by TAE)! !! Boron NB’s - 500-700 keV to penetrate into core (based positive ion technology)! !! Tests with two component plasmas at C-2W ! Presenter: First Last! Privileged and Confidential! 23! Gas handling is much easier in FTC! !! At T ~ 300 keV CX cross section is very small. No CX loss for NB or hot plasmas! !! Neutral ionization length is < 1 cm. No neutral can penetrate in SOL plasma! Presenter: First Last! Privileged and Confidential! 24! Gas handling in divertors! !! Fueling and exhaust composition! + /0)-246+BcC 5a='01,+BcC <&3,341 @W 8A ?3&341! VV ! N ! K) 9 @@ ! ! ! ! ! ! !! Total exhaust rate G ~ 1020 1/s! !! It is much easier to achieve required gas condition! !! The required pumping speed ~250 m3/s (compare with 2000 m3/s in C2W!)! !! Predominantly He with Hydrogen and Boron impurities! ! Presenter: First Last! Privileged and Confidential! 25! Ash control is critical for pB11! !! Without ash control: CHe ~ 70-80% resulting in a very low Q !! It takes about 100 s to build up ash! !! High Q requires very efficient ash control! !! Required ash concentration < 5%! Presenter: First Last! Privileged and Confidential! 26! Energy conversion! !! 80% of fusion energy goes to the side wall in form of x-rays (~150keV). Converted in electricity by a thermal cycle (50% efficiency)! !! Convective energy loss into expanders (20% of fusion power) can be converted electrostatically in expanders! !! Ions are accelerated by gradB and electric potential in the convertors to E|| ~ 1.2-1.5 MeV with Eperp < 10 keV! !! Technology developed for mirror machines in 70th (85% efficiency demonstrated) ! Presenter: First Last! Privileged and Confidential! 27! DEMO-lite! K26=+)4)&67+`)'P1+ $#+P'64),1+ >3S+)4)&67+`)'P1+ #&731,',+ 5a%'4F)&+ Presenter: First Last! Privileged and Confidential! 28! Summary! !! Higher Q ~ 6-8 is possible with new cross sections! !! Many physics and engineering challenges to address but no stoppers! !! C-2W will address some of the critical physics issues. A parallel R&D work is equally important! Presenter: First Last! Privileged and Confidential! 29!