FUNFI Fusion for Neutrons and Sub-critical Nuclear Fission

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FUNFI Fusion for Neutrons and Sub-critical
Nuclear Fission Villa Monastero, Varenna Italy
September 12-15 2011 What we should do for
transition from current tokamaks to
fusion-fission reactor (From fusion romance to
reality) S. Mirnov GNC RF TRINITY 142 190
Troitsk Moscow Reg. RUSSIA 2011
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Introduction. Requirements shown by Russian
atomic engineers to the parameters
FNS-1 1.Decision of steady state tokamak
operations. The superconductor and warm magnets
systems Current drive. 2.The problem of
plasma-wall interaction Phenomenological limit
of power load on tokamak first wall. The neutron
flux limits in FNS-1. Lithium as a tokamak PFC
protector 3.Creation of hot plasma zone with
high neutron emission The control of plasma
density Impurity control in the center of tokamak
plasma 4. Other candidates on the role of fusion
neutron source type of FNS-1 The mirror traps
(GDT) Stellarators (LHD) Superconductor tokamaks
(Tor Supra, EAST, KSTAR) Spherical torus. (NSTX,
MAST) Conclusions
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Fusion-Fission roots in Russia 1956 Sakharov
A. Memoirs Vintage Books, New York (1990) 142
I.N.Golovin, V.I.Pistunovich, G.E.Schatalov
Preprint IAE 1973 Physical basis of
tokamak-reactor with NBI (First hybrid
FF) I.N.Golovin, G.E.Schatalov, B.N.Kolbasov.
Isvestiya AS USSR 1975 Energy and transport ?
6 p28-34. . USA/USSR Symposium on
Fusion-Fission Reactors, Lawrence Livermore
Laboratory CONF-760733 July 13-16 1976. USSR/USA
Seminar 14March-1April 1977 M Atomisdat 1978
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tE, 98 0,0365.I? 0,97.B? 0,08.PH
-0,63.n0,41.M0,20.R1,93.(a/R)0,23.k0,67 sec
ITER Physics basis. Nuclear Fusion v39 N12
1999 Progress in ITER Physics basis. Nuclear
Fusion v47 N6 2007
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Potential using of fusion-fission in the
electricity production (for Russia)
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Joint commission of 2009Y Plasma physicists
(TRINITI, KURCHATOV, IOFFE Inst.) and Atomic
engineers (DOLLEJAL, KURCHATOV Inst. suggested
the three steps scheme of Russian FNS
development
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• Creation of the hydrogen TNS prototype TNS-0 on
  the T-15 basis for the investigation of steady
  state tokamak physics
• 2. Creation of the tokamak- breeder prototype
  TNS-1 - with neutron power 20-50MW and fuel
  production equal 20-100 kg p/y
• (2020-2025yy)
• 3.Creation of the commercial tokamak- breeder
  prototype TNS-2 with neutron power 100-200MW
  and fuel production up to 1000 kg p/y
• (2025-2035yy)

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• The Russian fission community has made special
  requirements to the fusion neutron source FNS-1
  for the first step of investigation.
• quasi-steady state (with availability Kt gt80)
  DT fusion reactor operation
• surface neutron load pn not lower 1017n/m2sec
  (0.2MW/m2)
• total neutron output not lower Pn20MW.
• The main aims of FNS-1
• demonstration of industrial probabilities of such
  neutron source, with ability of nuclear fuel
  producing on the level 100kg for the test of
  different versions of experimental blanket
  modules.
• (So called Lopatkins requirements at name of
  deputy director of Dollejal institute
  A.V.Lopatkin )
• Middle-scale device with the total cost not
  higher than 1bn.
• No activity in direction of sub-critical Nuclear
  Fission from safety problem.

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What we should do for transition from current
fusion devices to FNS-1?
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Comparison of the total neutron energy
production Qn per day for FNS-1, ITER (project),
JET (should be multiplied up to 2000 times dotted
array proposal steady state operational regime),
and NIF (proposal regime, should be multiplied up
to 200000 times )
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The superconductor or warm magnets systems?
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The creation of FNS-1 on the basis of a warm
magnets system (Cu, Al) is considered with
superconductor if one takes into account that a
limited time period (about 1 year ) will be
sufficient for the FNS-1main task production of
100kg of fuel by a steady- state fast neutron
source with the total neutron power not lower
than 20MW and density 0.2MW/m2. Within this
time the system will accumulate in its units the
relatively low neutron fluency (3 1024n/m2). The
30 of such neutron fluency will be enough for
production of the planned 100 kg of fuel
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Magnet (Cu) system of VNS-1 project
(TRINITI-Kurchatov 1993Y) 1-poloidal, 2-toroidal
Cu coils. 3-concret tank a/R0.7/2 m, B0 3.5T,
Jp 4MA P300MW
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The problem of plasma-wall interaction
Phenomenological limit of power load on the
tokamak first wall
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A-dynamics of neutron production- Pfus B-PH
in linear scale, crosses and PH,

- PH/S.
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The tokamak praxis shows the existence of rather
hard phenomenological limit of power load on the
tokamak first wall qc 0.20.1?W/m2 What
happened after the violation of this limit?
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TFTR . Evolution of DT fusion power and plasma
stored energy for a series of plasmas with mixed
D and T NBI. One or two lithium pellets were
injected into the plasma prior to NBI.
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This limit will confine the maximum value of
the neutron flux density pn on the first wall of
the tokamak-reactor. In the most favorable case
of burning tokamak the relation between the total
power of neutron production Qn to the plasma
heating power by a-particles PH (as is known) is
equal to 4. It means that for the burning
reactor type DEMO limit qc 0.2?W/m2 is
equivalent to limit pn0.8?W/m2 This limit
seems too low for a pure fusion reactor, but not
for a fusion-fission one. For example, the
fusion-fission burning tokamak scale ITER with
natural uranium blanket can produce up to 3GW
electric power and at the same time produce the
fuel for fission reactors needed for generation
additional 10GW of electricity.
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The neutron flux limit in FNS-1
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In FNS-1 case the situation is complicated by the
fact that two sources of fast neutrons should be
used in it (as in burning tokamak). The FNS-1
has two neutron producers one part of neutron
output should be generated during the direct
interaction of high energy ion beam (100-300keV)
with the target - DT (11) tokamak plasma (QBF)
The second part should be the result of DT
fusion in the hottest target plasma (QTF). In
real prototypes of FNS-1 TFTR and JET both
these fusion sources were considerable.
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In the steady state conditions the total heat
flux to the first wall will be the summary
results of both sources of fusion a-particles and
NBI power. If we write QBF as a?? , where a is
function, connected NB power PH with fusion
output from direct interaction of ion beam with
target plasma, the summary neutron output can be
written, as Qn 0.8(a?? QTF) and power
of total heat flux as ?? 0.2 (a??
QTF). That means pn/q 0.8(a QTF/??)/ (1
0.2 (a QTF/ ??)) For burning tokamak
(PH0) we have again pn/q 4. For the opposite
case QTF 0 (case of pure target) pn/q 0.8a
/ 1 0.2a
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The calculated a values as function of electron
temperature Te for different energies of injected
D-atoms to the clean (Zeff 1) DT (11) target
plasma (V.I. Pistunovich 1976)
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The achievement of values a 1 in average-scale
tokamaks seems realistic. In this case pn/q
from can be 0.67 and if we take into account the
limit qc 0.2?W/m2, the pn value should be equal
0.13 ?W/m2, which is lower of neutron density
requirements 0.2?W/m2 for FNS-1. It is obvious
that in order to increase the neutron load
tokamak with visible QTF output should be chosen.
In particular, with QTF/?? 1 the pn value can
be increased up to 0.26 ?W/m2.
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Another possible way is increasing qc by
mitigation of heat contact plasma-wall effect.
It is known that the most aggressive form of
such contact is the first wall bombardment by hot
plasma during development of plasma boundary
instabilities (ELMs, Blobs) with high local
energy loads and, as a result, with active
erosion of the first wall materials. To smooth
the local energy loads some experimentalists try
to reradiate plasma energy flux by injecting
radiated impurities into the plasma periphery.
The role of such kind impurity can play Li. It
should be pointed out that Li pellet injection
was actively used in TFTR
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Lithium as a tokamak PFC protector
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J.Bohdansky and J.Roth Temperature dependence
of sputtering behavior of Cu-Li alloysNucl.
Instr.and Methods in Physics Research B23 (1987)
518
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The main surprise of numerous tokamak lithium
experiments was the discovery of the poor lithium
penetration to the hot core from plasma periphery
(lithium screening). The effective ion charge
in plasma center - Zeff(0) which had been equal
to 2 or higher (TFTR, T-11M, FTU, T-10, CDX-U,)
dropped down to 1 after first wall lithiaton.
The mechanism of lithium screening is not fully
clear. Probably that is consequence of deep gap
between lithium first (5.8eV) and second (75eV)
ionization potentials. The lithium screening
effect can be served as a basis of concept of
permanent lithium circulation close the tokamak
first wall for their protection from the direct
plasma bombardment
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FTU-experiment (M.L.Apicella et al. 2005)
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Lithium splashing problem
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Capillary Porous Structure with (A) and
without Li (?)
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Scheme of Li circulation emitter-collector
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FTU experiment. Li CPS limiter after plasma
exposition
No Surface Damage
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Li migration
by CPS
W
CPS
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Creation of hot plasma zone with high neutron
emissionThe control of plasma density
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The record TFTR DT shot with NBI PH 40MW (
PH/Sq 0.5MW/m2, pnmax 0.12MW/m2)
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In steady state tokamak all fluxes of neutral
atoms in the plasma column should be balanced by
their outward diffusion, neutralization and
pumping. The atoms of NBI and He should be
removed by the divertor with expanded divertor
plates (for example, by snowflake type)
probably with lithium coating. For the He
pumping and creation of Li-circulation in
divertor SOL a mushroom like pump limiter shown
in could be used.
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The mushroom like pump limiter for the He
pumping and creation of Li-circulation in
divertor or limiter SOL
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Impurity control in the center of tokamak plasma
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As is shown by the experience of ECRH use in
small and average scale tokamaks, the local
ECRH permits not only increasing Te, which
increases the fast ion relaxation time but also
promoting impurity removal from plasma center and
increasing the diffusion of DT ions. It is
supposed to stabilize Zeff in plasma center on
the level of 1-1.2, which is needed for
achievement of a1. The next way of the a
increase (Fig.5) can be bringing up the energy of
the injected atoms from 110-120keV (TFTR, JET) up
to 150keV.
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Other candidates on the role of fusion neutron
source type of FNS-1The mirror traps
(GDT)Stellarators (LHD)Superconductor tokamaks
(Tor Supra, EAST, KSTAR)Spherical torus. (NSTX,
MAST)
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The comparison of different types of magnetic
fusion devices as candidates on the role of FNS-1
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Spherical torus.
Jp(5eaB0/q?(95))1k2(12d2-1.2d3) (1.17-
0.65e)/(1-e2)2 /2,
The formal substitution in this equation e
0.7-0.8 and best parameters of high performers
classical (elt0.4) tokamaks - q?(95)3, k3,
d0.8 3, k3, -gives the above mentioned profit
in Jp up to 3-5 times. That is a mistake. The
right side of this equation consists of two kinds
of parameters. Their first part seems
independent, hard determined by experimentalist.
That is e, a, B0, which are the material
condition of experiment defined its scale and
cost. The second group of plasma connected
parameters - q?(95), k and d seems as internal
depended.
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. Really each experimentalist should find an
optimal combination of these parameters with the
main goal to obtain the maximal plasma current.
If this combination is universal, the maximal
Jpm?? should be proportional eaB0(1.17-
0.65e)/(1-e2)2,
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The maximal values of Jp, received on 4 leaded
spherical torus as function of eaB0 (1.17-
0.65e)/(1-e2)2 14-19, cross NSTXnew (B00.3T,
Jp1MA) private communication
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The next serious disillusion was brought by the
unexpected effect of spontaneous breaking of
discharges in spherical torus, which was observed
simultaneously in both leaded devices NSTX and
MAST. The nature of this effect is not yet
clear today. Probably that is effect, connected
with too high ß? in spherical torus. As a
result, the shot duration was limited in these
devices by 1-1.8 sec instead of 5sec, proposed by
projects. That means the spherical torus with e
0.7-0.8 lost the main advantage of tokamaks
the potential ability of steady state operations.

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NSTX and MAST- effect of discharge interruption
J.E.Menard, M.G.Bell,e.a. Proc.21st IAEA Fusion
Energy Conf., Chengdu, China, 2006 OV/2-4.
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The f(e) (1.17- 0.65e)/(1-e2)2 function v.s.
e and R/a. (For consistency with a classical
tokamak region it is divided into1.17). Few
classical tokamaks, spherical torus and some
FNS projects are shown by arrows.
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Conclusions The FNS program, developed parallel
to ITER activity, can essential approach the
entry DT-fusion in the commercial power The
initial technology requirements (p0.2MW/m2,
P20MW/m2, Kt0.8), shown by Russian atomic
engineers to the parameters of the first stage of
fusion neutron source FNS-1, can be met under
condition of successful improvement of the
existing middle-scale tokamaks parameters in the
following main directions
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• development of steady state (or quasi-steady
  state) tokamak operations by learning to use non
  ohmic current drive methods with a simultaneous
  organization of a closed D,T- loop circulation
  and He removal,
• 2. increase of energy NBI up to 150 and more
  keV,
• 3. lower level Zeff up to 1-1.2
• (with possible use of Li technologies),
• 4. active use of ECRH for
• a) control of plasma density,
• b) control of a impurity level,
• c) heating of electrons and weakening of ion
  beams relaxation,