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Estimating the Output Characteristics of f Nuclear-Laser Facility
A.P. Barzilov, A.V. Gulevich, P.P. Dyachenko,
B.V. Kachanov, S.G. Kolyada, O.F. Kukharchuk,
E.A. Pashin, V.N. Smolsky, A.V. Zrodnikov
Institute for Physics and Power Engineering, Bondarenko Sq.1,
249020 Obninsk, Kaluga reg., RUSSIA
Abstract. The main results of mathematical simulation of the power model processes of a
laser system pumped by a twin-core fast burst reactor are presented. Neutronics, kinetics
and thermal dynamics problems are discussed. Mathematical simulation of energy
deposition by fission fragments into the laser medium as well as thermal and gas dynamic
processes in the laser element have been carried out. The optical scheme and output laser
beam parameters have been estimated.
INTRODUCTION
A prospective concept for a power laser system is a one based on a optical quantum
amplifier pumped by a nuclear reactor. Such a system combining the high-energy pulses of
laser radiation with the short pulse duration’s of a nuclear fission reactor would provide a
simple and very space-time concentrated source of energy. At the present time a
demonstration mock-up of a reactor-pumped laser system (RPLS) is been developed at the
Institute of Physics and Power Engineering nuclear-laser facility «B» [1].
The numerical simulation of the power characteristics of an RPLS is one of the
important problems to be solved on the path to creating a pilot system. This report presents the
most interesting results of neutronic, thermal, gas dynamic and optical studies of the power
mock-up of a twin-core RPLS, which were obtained using special mathematical methods and
codes [2].
RPLS POWER MODEL
The power model of the quantum nuclear pumped amplifier (See Fig1) consists of two
blocks which are essentially different in terms of neutron activity: a critical reactor (source of
neutrons) and a subcritical laser block (multiplication factor less than 0.9).
The twin-core fast burst reactor BARS-6 (analogous to the BARS-5 reactor [3])
produces 5·1017 fission in the two cores with a pulse duration of 40 s (for the case of reactor
system without laser block). The cores are covered with boron coatings.
The laser block (LB or the pumping block) is a cylinder 2.5 m long and having a
diameter of 1.7 m with rectangular cavity for insertion of the BARS-6 reactor cores. The LB
consists of laser-active elements imitators (in the physics sense), a neutron moderator and
outside reflector elements. To increase the pumping efficiency an internal polyethylene
reflector neutron moderator may be placed in the rectangular cavity between the reactor cores
and the LB. Seven laser-active elements (LAELs) are inserted into the top of the LB area.
Proc. Intern. Conf. ICENES'96, Obninsk, 1996
 - 1996 Institute for Physics and Power Engineering, Technical Physics Laboratory
http://www-tpl.ippe.obninsk.ru
E-mail: kuh@ippe.obninsk.ru
2
LAEL is a thin-walled pipe of corrosion-proof steel (Dext=49 mm, Dint=48 mm, length=2500
mm) with an internal metal uranium-235 coating (thickness - 6 m), filled with an Ar-Xe
mixture at an initial pressure of 0.5 atm.
Figure 1.
Power model of reactor pumped laser system:
1-burst reactor, 2-laser block, 3-outside neutron reflector,
4-laser element imitators, 5-laser-active elements.
NUMERICAL SIMULATION OF RPLS POWER CHARECTERISTICS
Neutronics, gas dynamics, and optic characteristics of the RPLS were computed using
especially elaborated methods and codes. The dynamic and power characteristics of the RPLS
were also estimated.
Numerical Simulation of RPLS Neutronics
From the point neutron physic the twin-core reactor with LB is a coupled reactor
system. Mathematical simulations of the neutronics for this system were made using the
Monte-Carlo method. The basic neutron physical characteristics (coupled coefficients, neutron
lifetimes , multiplication factors) were estimated and are shown in Table 1, where Kbl is the
multiplication factor of the LB; Kbl-r is the coefficient of interaction «reactor coreLB»; Kr-bl
is the coefficient of interaction «LBreactor core»; Kr-r is the coefficient of interaction
«reactor corereactor core»; bl is the prompt neutron lifetime in LB; and  is the internal
neutron reflector thickness.
Proc. Intern. Conf. ICENES'96, Obninsk, 1996
 - 1996 Institute for Physics and Power Engineering, Technical Physics Laboratory
http://www-tpl.ippe.obninsk.ru
E-mail: kuh@ippe.obninsk.ru
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Table 1. Neutron-physical characteristics of the «B» nuclear-laser facility
Parameter
Value
=0 cm
0.78
0.0049
0.24
0.0015
311
Kbl
Kr-bl
Kbl-r
Kr-r
bl, s
=7 cm
0.72
0.0008
0.126
0.0015
310
The time-space behavior of the neutron flux in transient processes for the pumping
block was investigated. Neutron powers of the burst reactor and the LB for the case of =0 cm
are shown in Fig.2. The fission space distributions into the LB have been estimated. As a
result, the amplitudes of non-uniformities (max/min) are as follows: on radial coordinate 2,
on longitudinal coordinate 3, on azimuth 2. It should be noted that global non-uniformities
in the block determine the amplitude of local non-uniformities. The longitudinal distributions
of pumping energy (normalized to the average value in LB) in the top area of the LB for =7
cm are shown in Fig.3.
power, W
3.0E+8
- laser block
2.5E+8
- reactor core
2.0E+8
1.5E+8
1.0E+8
5.0E+7
0.0E+0
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0.45
0.50
time, s
Figure 2. Time behavior of demonstration mock-up of a reactor-pumped laser system.
Proc. Intern. Conf. ICENES'96, Obninsk, 1996
 - 1996 Institute for Physics and Power Engineering, Technical Physics Laboratory
http://www-tpl.ippe.obninsk.ru
E-mail: kuh@ippe.obninsk.ru
4
Figure 3. Space distribution of fission in LB top area (normalized on the average value in
LB).
Gas dynamics. Energy deposition into gas medium. Optics
Numerical simulations of temperature distributions and gas dynamic characteristics
have been made for the laser-active element under consideration. Using data on the nonuniformity of fission density distribution shown in Fig.3 (for the case of 6 MJ energy released
in the laser block during a pulse), non-uniformities in the energy deposition of fission
fragments into the gas medium of LAEL, as well as the gas temperature and density, were
analyzed.
Three-dimensional distributions of gas density and fission fragments energy deposition
in the LAEL are presented in Fig.4a-b. The results of this simulations are used to evaluate the
output beam quality, done on the basis geometric optic theory. The index of refraction has
been estimated using the Lorenz-Lorenz relationship for the neutral gas, because the electron
density is very low. Fig.5 illustrates the lensing effect in the LAEL to the moment of the
pumping pulse end.
Thus, some of the important power characteristics for laser-active elements are
presented in Table 2, where:
 is the internal neutron reflector thickens; E is the LB fission energy;  is the time duration
of the pumping pulse; T is the average laser medium temperature at the pulse maximum; W
is the average density of energy deposition; w is the average maximal energy deposition;  is
the expected output laser energy (for seven LAELs) with an efficiency coefficient 2%.
Proc. Intern. Conf. ICENES'96, Obninsk, 1996
 - 1996 Institute for Physics and Power Engineering, Technical Physics Laboratory
http://www-tpl.ippe.obninsk.ru
E-mail: kuh@ippe.obninsk.ru
5
3
a
b
Figure 4. Three-dimensional distribution of (a) gas density and (b) energy deposition in
LAELs located in top LB area (initial gas pressure is 0.5 atmosphere).
Proc. Intern. Conf. ICENES'96, Obninsk, 1996
 - 1996 Institute for Physics and Power Engineering, Technical Physics Laboratory
http://www-tpl.ippe.obninsk.ru
E-mail: kuh@ippe.obninsk.ru
6
radius, m
0.025
0.020
0.015
0.010
0.005
0.000
-1.0
-0.005
-0.5
0.0
0.5
1.0
-0.010
-0.015
-0.020
-0.025
length, m
Figure 5. Ray path in LAELs located in top LB area.
Table 2. Power characteristics of laser-active elements
Parameter
E, MJ
, ms
T,K
W , J/cm3
w , W/cm3
, J
Value
=0 cm
20
50
780
0.7
25
420
=7 cm
6
5
520
0.3
37
170
REFERENCES
[1] P.P. Dyachenko et al. Energy model of a pulse nuclear reactor-pumped laser system // in
Proceedings of the Conference on ICENES’93, Makuhari, Chiba, Japan.
[2] A.V. Gulevich et al. Mathematical models and codes for calculation of dynamic
characteristics of NPL’s systems // in Proceedings of the Conference on Physics of
nuclear induced plasmas and problems of nuclear pumped laser, 26-29.05.92, Obninsk,
Russia.
[3] A.A. Snopkov et al. Neutron source based on twin-core burst reactor BARS-5 // in
Proceedings of the Conference on Physics of nuclear induced plasmas and problems of
nuclear pumped laser, 26-29.05.92, Obninsk, Russia.
Proc. Intern. Conf. ICENES'96, Obninsk, 1996
 - 1996 Institute for Physics and Power Engineering, Technical Physics Laboratory
http://www-tpl.ippe.obninsk.ru
E-mail: kuh@ippe.obninsk.ru