The concept of a research fusion reactor
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України
2000
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| Цитувати: | The concept of a research fusion reactor / V.G. Kotenko, V.I. Lapshin, G.G. Lesnyakov, S.S. Romanov, E.D. Volkov // Вопросы атомной науки и техники. — 2000. — № 3. — С. 70-72. — Бібліогр.: 16 назв. — англ. |
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irk-123456789-823882015-05-30T03:01:42Z The concept of a research fusion reactor Kotenko, V.G. Lapshin, V.I. Lesnyakov, G.G. Romanov, S.S. Volkov, E.D. Magnetic confinement 2000 Article The concept of a research fusion reactor / V.G. Kotenko, V.I. Lapshin, G.G. Lesnyakov, S.S. Romanov, E.D. Volkov // Вопросы атомной науки и техники. — 2000. — № 3. — С. 70-72. — Бібліогр.: 16 назв. — англ. 1562-6016 http://dspace.nbuv.gov.ua/handle/123456789/82388 533.9 en Вопросы атомной науки и техники Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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Magnetic confinement Magnetic confinement |
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Magnetic confinement Magnetic confinement Kotenko, V.G. Lapshin, V.I. Lesnyakov, G.G. Romanov, S.S. Volkov, E.D. The concept of a research fusion reactor Вопросы атомной науки и техники |
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Article |
| author |
Kotenko, V.G. Lapshin, V.I. Lesnyakov, G.G. Romanov, S.S. Volkov, E.D. |
| author_facet |
Kotenko, V.G. Lapshin, V.I. Lesnyakov, G.G. Romanov, S.S. Volkov, E.D. |
| author_sort |
Kotenko, V.G. |
| title |
The concept of a research fusion reactor |
| title_short |
The concept of a research fusion reactor |
| title_full |
The concept of a research fusion reactor |
| title_fullStr |
The concept of a research fusion reactor |
| title_full_unstemmed |
The concept of a research fusion reactor |
| title_sort |
concept of a research fusion reactor |
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Національний науковий центр «Харківський фізико-технічний інститут» НАН України |
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2000 |
| topic_facet |
Magnetic confinement |
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http://dspace.nbuv.gov.ua/handle/123456789/82388 |
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The concept of a research fusion reactor / V.G. Kotenko, V.I. Lapshin, G.G. Lesnyakov, S.S. Romanov, E.D. Volkov // Вопросы атомной науки и техники. — 2000. — № 3. — С. 70-72. — Бібліогр.: 16 назв. — англ. |
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Вопросы атомной науки и техники |
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2025-07-06T08:53:34Z |
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| fulltext |
UDC 533.9
Problems of Atomic Science and Technology. 2000. N 3. Series: Plasma Physics (5). p. 70-72 70
THE CONCEPT OF A RESEARCH FUSION REACTOR
V. G. Kotenko, V. I. Lapshin, G. G. Lesnyakov, S. S. Romanov, E. D. Volkov
Institute of Plasma Physics, National Science Center “Kharkov Institute of Physics and
Technology”, Kharkov 61108, Ukraine
In existing magnetic confinement fusion reactor
designs the plasma radius rpl is usually comparable
with the radius rw of the 1-st wall, rpl/rw≤1. It is well
known that the realization of these designs entails a
number of unsettled problems, including the 1-st wall
problem. According to different kinds of estimates, the
interaction of plasma-generated high-intensity energy
flows with the 1-st wall leads to a limitation in the
service life of the 1st wall to 2-5 years. These
estimates should be considered as optimistic, because
they rely on taking into account the impact of individual
components of the above-mentioned flows. The
replacement procedure of the 1st wall, even if it
appears technically feasible under conditions of high
induced radioactivity, will be extremely expensive and
will involve the necessity of disposal of radioactive
wastes in great amounts. At a rated 30- to 50-year
normal operation of a fusion power plant, the
replacement procedure should be repeated no less than
10 times, and the threat for this plant to be transformed
into an unprecedented-power factory of radioactive
refuse production becomes quite real. To minimize the
number of these replacements is the problem, the
solution of which is of crucial importance for the
commercial fusion reactor. Great hopes for the
required increase in the 1st wall service life are pinned
on the creation of low activation materials showing a
high resistance to the simultaneous and combine (i.e.,
with due account for the synergy effects) action of the
whole totality of fusion plasma radiations . This issue
has not been resolved so far by force of disproportion
between the reactor conditions and the present-day
conditions, taking place in every sort of simulation
experiments. Its resolution very much depends on the
possibility of conducting long-term materials science
experiments at full-scale conditions of self-sustained
fusion reactions, i. e., in a fusion reactor now in
operation. So, the present-day situation looks like a
vicious closed circle, and one should find a way to get
out of it.
rw
rpl
2
1 3
Fig.1 Fusion reactor configuration: 1 - existing
designs; 2 – in proposed research fusion reactor
(RFR); 3 - future commercial design.
It is evident that at a given fusion plasma radius this
way may consist in an essential reduction of specific
loads on the 1st wall at the expense of increasing its
surface area, i. e., by realizing configuration 2 (see
Fig.1), where rpl/rw<<1 [1, 2]. As a result, the course
of fusion investigations may be as follows:
- at the present stage efforts should go into the design
and creation of a steady-state ( to prevent a swing in the
1st wall temperature) deuterium-tritium fusion reactor
based on configuration 2. This is to be a reactor with all
attributes of a fusion power plant operating for long and
reliably, because with an appropriate choice of rw the
design loads on the 1st wall, the blanket and on the
superconducting magnetic system are reduced to a
value providing their long-term normal operation.
However, no economic goals can be pursued with this
reactor because of an essential reduction in the neutron
flow density on the 1st wall. This will be a research
fusion reactor (RFR) of independent importance,
assigned for the widest range of issues related not only
to fusion power engineering. Apart from the mentioned
materials science problem, possible RFR applications
may also include nuclear fuel production for fission
reactors, the transmutation of long-lived radionuclides
as a radical means to reduce radioactivity of fusion
reactor wastes, production of useful isotopes, etc.;
- at the next stage, with gaining information about the
operation of this reactor and with associated scientific-
technical progress it would be possible to achieve the
transition to reactors of considerably smaller sizes
(configuration 3, Fig.1).
Are there any magnetic systems enabling one to
realize configuration 2? Among a great many known
magnetic systems of plasma traps, we note the
stellarator-type magnetic systems [3], namely, classical
stellarators and torsatrons. Using the available
literature data for straight stellarators and torsatrons an
analysis [4] was made to determine the ratio of the
radius of separatrix edge rs to the radius a of the
circular cylinder, where the helical currents I flow, rs/a
(as an analogue of the rpl/rw ratio). The main results of
this analysis are presented below in a graphical form.
For the polarity l=1,2,3,4 straight classical
stellarators, Fig.2 presents the ratio rs/a (and ro/a -
magnetic axis radius in l=1 stellarator) as function of
the parameter η=2πεaBo/µoI [5, 6]. Here Bo is the
longitudinal magnetic field, µo is the magnetic
constant, I is the helical current, ε=2πa/L<<1, L is the
pitch of helical coils. At a given ε, the η value can be
varied within rather wide ranges by changing the Bo/I
ratio; that gives an opportunity to control in situ the
71
rs/a value throughout the experiment. For the l=1
stellarator the upper part of curve 1 specifies the
position of the separatrix edge rs/a, and the lower part
gives the position of the magnetic axis ro/a. It is seen
that with a decreasing η→5 the region of closed
magnetic surface existence diminishes ((rs/a)-(ro/a)→
0). In spite of this, one fails to significantly move away
the separatrix edge from the cylinder surface in the l=1
stellarator (rs/a cannot be lower than ∼0.58). In the l>1
systems, where the magnetic axis radius is ro/a=0, the
region of closed magnetic surface existence is
centered, and the maximum dimension of this region
is ∼ rs/a. In l=2
0 1 2 3 4 5 6 7 8
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
r
/
a,
r
/
a
23
4
s
1
r /ao
r /as
o
Fig.2 Separatrix edge radius rs/a (and magnetic axis
ro/a in l=1 stellarator) as function of η in l=1,2,3,4
straight stellarators (curves 1-4, respectively).
stellarator, curve 2 in Fig.2 suggests that at rs/a<0.5
the radius of the separatrix edge is very sensitive to
variations in the parameter η, whose values are close to
the critical value. So, the creation of the l=2 magnetic
system with rs/a<0.5 will demand high precision in
manufachering and current control system. The l=3
stellarator (curve 3) is characterized by the lowest rs/a
values at one and the same η and a linear dependence.
This peculiarity of classical stellarator is not lost in
the
0.0 0.5 1.0
I (arb. units)
0.0
0.1
0.2
r
/
R
-1
h
lc
o
Fig.3 Dependence of the last closed magnetic surface
radius rcl/Ro on the helical current I value in the l=3,
m=3 stellarator model with a/Ro=0.3 (l is the
polarity, m is the number of helical pitches, a is the
minor radius of the torus, Ro is the major radius of
the torus).
transition to the toroidal case. The calculations of a
modular classical-stellarator version [7] with a
considerable toroidicity have demonstrated that a
three-fold enhancement of current I in helical coils at a
constant longitudinal magnetic field value brings about
nearly the same decrease in the largest radius of the
region of closed magnetic surface existence , see
Fig.3.
In the classical torsatron, the longitudinal and
helical magnetic-field components are generated by
helical conductors, where the currents are coincident in
direction. Therefore, the position of separatrix edges in
these systems can be controlled only by choosing in
advance rigorous design parameters ε and the number
of helical windings l, invariable in the course of
experiments. In the l=1 torsatron, the positions of the
separatrix edge and the magnetic axis are determined by
the equation [8]: r/a≈0.5(1±(1-4/ε2)0.5). Curve 1
(Fig.4) shows the corresponding dependence. Similarly
to the case of l=1 stellarator, rs/a<0.5 cannot be
achieved in this torsatron. However, here the separatrix
edge lies in the sector free of the helical conductor. In
principle, this allows one to move the material wall
being within this sector away at a distance exceeding
the radius a of the cylinder. In the l=2 torsatron the
sought-for dependence (solid curve 2, Fig.4) has the
form [10]: rs/a≈(1-ε-2)1/4. Similarly to l=2
stellarator, the essential detachment of the separatrix
edge (rs/a<0.5) meets the same technical difficulties.
For the torsatrons with l=3,4, where ε<1, one can
obtain from [11]: rs/a≈ε2/(l-2) (solid curves 3,4,
Fig.4). Some of the numerical calculation results for
the low-toroidicity systems are also shown in Fig.4. It
is seen that from the standpoint of configuration 2
creation, the torsatrons with l=3,4, where at ε=0.3-0.5
the separatrix edges can be moved far away from the
cylinder surface, seem most attractive.
0.0 0.5 1.0 1.5
0.0
0.1
0.2
0.3
0.4
0.5
0.6
0.7
0.8
0.9
r
/ a
,
r
/a
2
34
s
2.0 2.5
1
r /as
r /ao
o
Fig.4 Separatrix edge radius rs/a (and magnetic axis
ro/a in l=1 torsatron) as function of ε in l=1,2,3,4
straight torsatrons (curves 1-4, respectively): solid
lines - analytical expressions [4, 10]; (o) [9]; (+)
a/Ro=0.0833, numerical calculation [10, 11]; (•)
a/Ro=0.03, our numerical calculation.
72
It should be noted that in toroidal torsatrons the
dimensions of the closed magnetic surface existence
region within rather moderate ranges can be controlled
in situ with the help of other means (application of a
transverse controlling magnetic field, variation of its
distribution, subtraction of the longitudinal magnetic
field, etc.).
So, there are a number of magnetic systems which
provide a deep detachment (controllable in situ in
some instances) of the plasma core from the wall, and
it is conceivable that this property is inherent not only
in stellarators. For example, in local mirror traps of the
electric-discharge device-type magnetic system [12,
13] a plasma core with a diameter an order of
magnitude smaller than the characteristic size of the
system can be realized. In principle, a deep detachment
of the plasma core from the wall can be realized in the
device with a current-carrying plasma at a steady-state
stage of discharge. It remains only to carefully choose
the most suitable magnetic system and to determine the
rpl/rw ratio to be close to optimum. There are some
reasons to believe that it will not be too small. At
rpl/rw∼0.3 the overall dimensions of the reactor will
be within the limits of certain known designs [14, 15],
and the service life of the first wall made from a
common austenitic stainless steel can presumably be
increased to a few tens of years [3]. If the service life
of the 1st wall is required to be ∼10 years and the RFR
power value is put minimum then the RFR overall
dimensions can appear more acceptable. As a result, the
RFR will demonstrate the possibility of long steady-
state burning of self-sustained fusion reactions at
already existing technological level. The transition to
smaller-size reactors, i. e., to commercial reactors,
calls for a significant rise of this level, this being
perhaps doubtful to fulfill in the absence of RFR.
Thus, for advancement towards a commercial fusion
reactor, we have proposed here as a next step a steady-
state operated RFR with an increased plasma-wall
detachment so as to further guarantee not only the
production but also a long-term (for many years)
confinement of a self-sustained plasma at the existing
technology level. In such a reactor one can expect
some decreasing in plasma contamination, this
conclusion being not only from general considerations.
For example, the investigations of prompt and non-
prompt fluxes of high-energy fusion reaction products
at the 1st wall have revealed [16], that a ∼20%
increases in the 1-st wall radius (plasma radius is
fixed) reduces blistering-induced impurities to a
permissible level. We consider the primary goal of the
RFR is the provision of full-scale conditions for
carrying out materials science experiments to create
and test 1st wall materials for the commercial fusion
reactor. The information level needed for that must be
reached before the RFR 1st wall service life comes to
an end, because the replacement of the 1st wall is the
next problem to be solved. The estimates, resulting
from the analysis carried out here point to the
existence of a wide variety of magnetic systems which
might provide a deep plasma core detachment from the
wall. For a successful choice of the RFR magnetic
system it is necessary that a more extensive and deep
analysis of all well known magnetic systems should be
carried out from the viewpoint of practical realization
of the configuration 2 (Fig.1). The task to optimize the
ratio rpl/rw is of great importance for the reduction of
the size and, accordingly, cost of RFR. However, the
RFR cost should not be an insurmountable barrier on
the way of creating this reactor. An example can be
found in the expensive APOLLON Program of landing
the man on the Moon, which had not had such a strong
motivation as gaining practically an inexhaustible
power source by the mankind.
References
1. V. G. Kotenko, G. G. Lesnyakov, S. S. Romanov. 7th
Ukraine Conf. on Controlled Nuclear Fusion and
Plasma Physics, Kiev, September 20-21, 1999.
Book of abstracts, p. 32 (in Ukraine).
2. V. G. Kotenko, V. I. Lapshin, G. G. Lesnyakov, S. S.
Romanov, E. D. Volkov. 10th Intern. Toki Conf. on
Plasma Physics and Controlled Nuclear Fusion
(ITC-10), January 18-21, 2000. Abstracts, PII-57, p.
172.
3. E. D. Volkov, V. A. Suprunenko, A. A. Shishkin,
Stellarator, (Kiev, Naukova Dumka, 1983, in
Russian).
4. V. G. Kotenko, S. S. Romanov. Preprint KhFTI 83-8,
(Kharkov, 1983, in Russian).
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217, (Kharkov, 1968, in Russian).
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1980, in Russian).
8. V. V. Demchenko, S. S. Romanov. Preprint KhFTI
76-13, (Kharkov, 1980, in Russian).
9. A. Mohri, J. Phys. Soc. Jpn., 28, 1549 (1970).
10. D. Marty et al., Nucl. Fus. 12, 367 (1972).
11. C. Gourdon et al., Nucl. Fus. 11, 140 (1971).
12. A. I. Bugrova et al., Fiz. Plazmy 19, 972 (1993).
13. V. G. Kotenko, Fiz. Plazmy 25, 972 (1999).
14. F. Tenney and G. Levin. A Fusion Power Plant.
MATT 1050, (PPPL, 1974).
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Nuclear Fusion Research 1974 (Proc. 5th Int.
Conf. Tokyo, 1974) Vol. 3, IAEA, Vienna, (1975)
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16. L. M. Hively, G. N. Miley. Nucl. Fus. 20, 969
(1980).
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