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Fusion chain reaction cycles in p + 6Li fuel
Nuclear Instruments and Methods in Physics Research A271 (1988) 5-6 North-Holland, Amsterdam
FUSION CHAIN REACTION CYCLES IN J. Rand McNALLY Jr. Aneutronic Energy
Laboratories, United Services
5
Li FUEL
p+6
Inc., P.O. Box 3037, Princeton NJ 08543, USA
Propagation chain and chain branching reactions are discussed for p+ 6 Li fueled fusion reactors. Safety measures are suggested for potential runaway fusion reactors. Fusion chain reaction cycles in p + 6 Li fuel have been previously published [1,2]. They include the cycle p+ 6 Li_ ,3 He+a +4.020 MeV,
(1)
3 He + 6
(2)
Li -~ p + 2a + 16.880 MeV,
with a net cycle result p+2 6 Li -gyp+3a +20 .900 MeV, and represent an easier way to burn 6 Li to three alpha particles than the direct 6 Li + 6 Li reaction because of the latter's higher Coulomb barrier. Table 1 Some Maxwellian av values for 6 Li fueled fusion: reactors Reaction
Q (MeV)
p +'5 Li -- 3 He+ a 3 He + 3 He --~ 2p+ a
--> d+ 7 Be -> p + 8 Be(G S) --} p + 8Be(2.94) p+ßBe(16.6) - p+ s Be(16.9) - p+2a -+ 2p + 7 Li - p+n+7Be d+3He -+ p+ a 3He+7Be - 2p+2a 6 Li+ 6 Li -> p+ 11B a+n+ 7 Be --> 3a
3He+ 6Li
_, .,1 11 1aa wr
X+6 Li
a+ 6Li a) b)
-~ d lUB -~ t + 9 B - 2a+n+3He -~ x' +d+ a -~ p+9Be
4.020 12.860 0.113 16.880 h) 16.880 b) 16.880 b) 16.880 b) 16.880 -0.467 -2.052 18.351 11.274 12.218 1 .908 20.901 i .T.r .a
uncz
2.987 0.808 0.332 -1 .474 -2.124
Reactions (1) and (2) represent a fusion propagation chain cycle inasmuch as one proton is regenerated in the complete cycle for each one input [2] . The loss of either the final proton or the intermediate 3 He chain center, either through too much slowing down out of the high reaction cross section region or direct loss from the plasma, means that one must promote other protons or 3 He ions into the high cross section region by nuclear elastic or Coulomb collisions to replenish the chain centers. Additionally, the plasma may undergo other reaction
a>
(10-22 M3/S) T = 200 keV 0.445 0.041 0.202 0.007 0.023 0.016 0.006 0.088 ? ? 2.52 0.042 0.002 0.010 0.005
aV
MI) v.vva.
n
0.004 < 0.001 ? ? < 0.001
T = 500 keV 1.30 0.278 1.43 0.049 0.187 0.083 0.044 0.439
T=1 MeV 2 .13 1 .25 3.17 , 0.101 0.427 0.169 , 0.094 0.840
? 2.42 1.71 0.041 0.230 0.179
? 2.07 13.3 0.144 0.861 0.739
0 .124 0.003
0.497 0.012
? 0.001
? 0.018
Q and áv values from J. Rand McNally Jr. and K.E. Rothe, Oak Ridge National Laboratory, unpublished (October 1980) except a + 6 Li, which is from M. MacGregor and R.J. Howerton, Lawrence Livermore National Laboratory, personal communication (April 1987). Taking into account 8 Be* excitation energy --> 2a + Q'.
0168-9002/88/$03 .50 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
1. NUCLEONICS/ENERGETICS
J.K McNally Jr. / Fusion chain reaction cycles in p + 6Lifuel
Li6 +He3
ALPHAS
90°, 0.9MeV Hé
ïn z
W z W
g W
PROTONS
eodO~
n
2
4
10 6 8 ENERGY (MeV)
12
e~0 14
1~
Fig. 1 . Spectra of alphas and protons from 3 Fe + 6 Li -+ p = 2a and p + s Be *. The excited states of 8 Be * decay into two alphas in <10 -15 s161.
steps (see table 1) which involve chain center branching, i.e., chain center multiplication [2], as in the endothermic reaction 3He + 6 Li - 2p + 7 Li - 0.467 MeV .
(4)
This reaction can occur whenever the center of mass collisional energy exceeds 0.467 MeV. Combining reactions (1) and (4), one has p+2 6Li-2p+a+ 7 Li+3 .552MeV,
and there is a doubling of the proton chain centers whenever the complete cycle occurs. Thus, a chain-thermonuclear plasma burn occurs inasmuch as both chain centers and thermonuclear reactions play a role in the nuclear fire. Another branching or multiplying reaction, since the alphas of reaction (2) have energies up to about 8 MeV plus some contribution from the available center of mass energy (see fig . 1), is the endothermic reaction a+ 6 Li-->p+ 9 Be-2.124MeV,
(6)
introduction of pure 6 Li fuel without the necessity of providing any hydrogen fuel input . The nuclear dynamo configuration would be ideally suited to this type of fueling along the axis since 6Li+ ions would be accelerated to the negative core of the plasma where increased ionization and scatter events would ensure irreversible trapping of 6Li3+ ions in the negative core of the reactor [ Previous evaluations of the ,+6 Li cycle (3) including 6Li +6 Li thermonuclear reactions but without the chain branching features of cycles (5) and (7) did not permit ignition of p +6 Li furl even with high ß to reduce synchrotron radiation losses [4] . Perhaps the inclusion of these new chain branching features with that of the nuclear dynamo configuration [3] with E x B drive of W; >,> We [5] may permit steady state burns of 6Li fuel (cold 6Li fuel feed, and hot ash and unburned plasma exhaust). It seems desirable to evaluate the 6Li fusion burn prospects in more detail inasmuch as 6Li is one choice of T-breeding blanket prospects in D + T tokamak or other D + T reactor blankets. A fault in the operation may lead to a leak of 6Li into a nuclear dynamo configuration formed upon ignition in a single canted minor section. A 6Li fueled fusion reactor, in contrast, would have grams of 6Li fuel available compared to the tons in a blanket region of any D + T reactor. The nuclear dynamo reactor configuration [3], if realizable, operates such that ions and electrons are partially charge-separated in the axial exhaust direction leading to the prospect of some direct electrical conversion or possibly thrust, especially if one magnet coil is operated at stronger field than the other coil. This should be a distinct advantage over toroidal confinement types of reactor configurations . As a precautionary measure in the operation of any fusion reactor, at least for the first time operation, .one should have accessible krypton purge gas to quench the reaction if needed, or a magnetic blowout prospect, to ensure rapid quench of any runaway fusion reactor .
References
where the center of mass collisional energy of a + 6 Li must eceeed 2.12-4 MeYr. C..olnbuling reactions (2) and (6), one has the chain branching cycle
[1) J. Rand McNally Jr., Nucl. Fusion 11 (1971) 187.
3 He+2 e Li- 2p+ a+ 9 Be+14 .756 MeV, and one chain center, 3 He, generates two proton chain centers and possibly another alpha chain center. The two chain branching reaction cycles (5) and (7), plus thermonuclear reactions between 6 Li + 6 Li which generate proton and 3He chain centers, may permit the
[3]
r i..., Fus- via, AT ucte..- I_ ycto__de .. Rgnd McNoliy va -ua.lcaa, Sraabyt4lt)~JG I of Chemistry, 3rd ed., eds. C.A . Hampel and G.G. Hawley (Van Nostrand Reinhold, 973). J. Rand McNally Jr., Atomkernenergie-KemTechnik 44 (1984) 70. J. Rand McNally Jr., Nucl . Tech ./Fusion 2 (1980) 9. J. Rand McNally Jr ., Fusion Tech . 12 (1987) 166, 320. D.A. Bromley and E. Almqvist, CRP 881, AECL 950, Atomic Energy of Canada Limited, Chalk River, Ontario, Canada (1959).
f71 T
[4] (51 [61
FUSION CHAIN REACTION CYCLES IN J. Rand McNALLY Jr. Aneutronic Energy
Laboratories, United Services
5
Li FUEL
p+6
Inc., P.O. Box 3037, Princeton NJ 08543, USA
Propagation chain and chain branching reactions are discussed for p+ 6 Li fueled fusion reactors. Safety measures are suggested for potential runaway fusion reactors. Fusion chain reaction cycles in p + 6 Li fuel have been previously published [1,2]. They include the cycle p+ 6 Li_ ,3 He+a +4.020 MeV,
(1)
3 He + 6
(2)
Li -~ p + 2a + 16.880 MeV,
with a net cycle result p+2 6 Li -gyp+3a +20 .900 MeV, and represent an easier way to burn 6 Li to three alpha particles than the direct 6 Li + 6 Li reaction because of the latter's higher Coulomb barrier. Table 1 Some Maxwellian av values for 6 Li fueled fusion: reactors Reaction
Q (MeV)
p +'5 Li -- 3 He+ a 3 He + 3 He --~ 2p+ a
--> d+ 7 Be -> p + 8 Be(G S) --} p + 8Be(2.94) p+ßBe(16.6) - p+ s Be(16.9) - p+2a -+ 2p + 7 Li - p+n+7Be d+3He -+ p+ a 3He+7Be - 2p+2a 6 Li+ 6 Li -> p+ 11B a+n+ 7 Be --> 3a
3He+ 6Li
_, .,1 11 1aa wr
X+6 Li
a+ 6Li a) b)
-~ d lUB -~ t + 9 B - 2a+n+3He -~ x' +d+ a -~ p+9Be
4.020 12.860 0.113 16.880 h) 16.880 b) 16.880 b) 16.880 b) 16.880 -0.467 -2.052 18.351 11.274 12.218 1 .908 20.901 i .T.r .a
uncz
2.987 0.808 0.332 -1 .474 -2.124
Reactions (1) and (2) represent a fusion propagation chain cycle inasmuch as one proton is regenerated in the complete cycle for each one input [2] . The loss of either the final proton or the intermediate 3 He chain center, either through too much slowing down out of the high reaction cross section region or direct loss from the plasma, means that one must promote other protons or 3 He ions into the high cross section region by nuclear elastic or Coulomb collisions to replenish the chain centers. Additionally, the plasma may undergo other reaction
a>
(10-22 M3/S) T = 200 keV 0.445 0.041 0.202 0.007 0.023 0.016 0.006 0.088 ? ? 2.52 0.042 0.002 0.010 0.005
aV
MI) v.vva.
n
0.004 < 0.001 ? ? < 0.001
T = 500 keV 1.30 0.278 1.43 0.049 0.187 0.083 0.044 0.439
T=1 MeV 2 .13 1 .25 3.17 , 0.101 0.427 0.169 , 0.094 0.840
? 2.42 1.71 0.041 0.230 0.179
? 2.07 13.3 0.144 0.861 0.739
0 .124 0.003
0.497 0.012
? 0.001
? 0.018
Q and áv values from J. Rand McNally Jr. and K.E. Rothe, Oak Ridge National Laboratory, unpublished (October 1980) except a + 6 Li, which is from M. MacGregor and R.J. Howerton, Lawrence Livermore National Laboratory, personal communication (April 1987). Taking into account 8 Be* excitation energy --> 2a + Q'.
0168-9002/88/$03 .50 © Elsevier Science Publishers B.V. (North-Holland Physics Publishing Division)
1. NUCLEONICS/ENERGETICS
J.K McNally Jr. / Fusion chain reaction cycles in p + 6Lifuel
Li6 +He3
ALPHAS
90°, 0.9MeV Hé
ïn z
W z W
g W
PROTONS
eodO~
n
2
4
10 6 8 ENERGY (MeV)
12
e~0 14
1~
Fig. 1 . Spectra of alphas and protons from 3 Fe + 6 Li -+ p = 2a and p + s Be *. The excited states of 8 Be * decay into two alphas in <10 -15 s161.
steps (see table 1) which involve chain center branching, i.e., chain center multiplication [2], as in the endothermic reaction 3He + 6 Li - 2p + 7 Li - 0.467 MeV .
(4)
This reaction can occur whenever the center of mass collisional energy exceeds 0.467 MeV. Combining reactions (1) and (4), one has p+2 6Li-2p+a+ 7 Li+3 .552MeV,
and there is a doubling of the proton chain centers whenever the complete cycle occurs. Thus, a chain-thermonuclear plasma burn occurs inasmuch as both chain centers and thermonuclear reactions play a role in the nuclear fire. Another branching or multiplying reaction, since the alphas of reaction (2) have energies up to about 8 MeV plus some contribution from the available center of mass energy (see fig . 1), is the endothermic reaction a+ 6 Li-->p+ 9 Be-2.124MeV,
(6)
introduction of pure 6 Li fuel without the necessity of providing any hydrogen fuel input . The nuclear dynamo configuration would be ideally suited to this type of fueling along the axis since 6Li+ ions would be accelerated to the negative core of the plasma where increased ionization and scatter events would ensure irreversible trapping of 6Li3+ ions in the negative core of the reactor [ Previous evaluations of the ,+6 Li cycle (3) including 6Li +6 Li thermonuclear reactions but without the chain branching features of cycles (5) and (7) did not permit ignition of p +6 Li furl even with high ß to reduce synchrotron radiation losses [4] . Perhaps the inclusion of these new chain branching features with that of the nuclear dynamo configuration [3] with E x B drive of W; >,> We [5] may permit steady state burns of 6Li fuel (cold 6Li fuel feed, and hot ash and unburned plasma exhaust). It seems desirable to evaluate the 6Li fusion burn prospects in more detail inasmuch as 6Li is one choice of T-breeding blanket prospects in D + T tokamak or other D + T reactor blankets. A fault in the operation may lead to a leak of 6Li into a nuclear dynamo configuration formed upon ignition in a single canted minor section. A 6Li fueled fusion reactor, in contrast, would have grams of 6Li fuel available compared to the tons in a blanket region of any D + T reactor. The nuclear dynamo reactor configuration [3], if realizable, operates such that ions and electrons are partially charge-separated in the axial exhaust direction leading to the prospect of some direct electrical conversion or possibly thrust, especially if one magnet coil is operated at stronger field than the other coil. This should be a distinct advantage over toroidal confinement types of reactor configurations . As a precautionary measure in the operation of any fusion reactor, at least for the first time operation, .one should have accessible krypton purge gas to quench the reaction if needed, or a magnetic blowout prospect, to ensure rapid quench of any runaway fusion reactor .
References
where the center of mass collisional energy of a + 6 Li must eceeed 2.12-4 MeYr. C..olnbuling reactions (2) and (6), one has the chain branching cycle
[1) J. Rand McNally Jr., Nucl. Fusion 11 (1971) 187.
3 He+2 e Li- 2p+ a+ 9 Be+14 .756 MeV, and one chain center, 3 He, generates two proton chain centers and possibly another alpha chain center. The two chain branching reaction cycles (5) and (7), plus thermonuclear reactions between 6 Li + 6 Li which generate proton and 3He chain centers, may permit the
[3]
r i..., Fus- via, AT ucte..- I_ ycto__de .. Rgnd McNoliy va -ua.lcaa, Sraabyt4lt)~JG I of Chemistry, 3rd ed., eds. C.A . Hampel and G.G. Hawley (Van Nostrand Reinhold, 973). J. Rand McNally Jr., Atomkernenergie-KemTechnik 44 (1984) 70. J. Rand McNally Jr., Nucl . Tech ./Fusion 2 (1980) 9. J. Rand McNally Jr ., Fusion Tech . 12 (1987) 166, 320. D.A. Bromley and E. Almqvist, CRP 881, AECL 950, Atomic Energy of Canada Limited, Chalk River, Ontario, Canada (1959).
f71 T
[4] (51 [61