# On feasibility of optimizing the neutronic performance of a laser system pumped by a pulsed reactor

10/02/2016 2016 - #03 Physics and technology of nuclear reactors

Gulevich A.V. Kukharchuk O.F. Brezhnev A.I. Suvorov A.A.

### UDC: 621.039.5

The paper examines the calculated feasibility of improving the energy characteristics of power pulses in a system consisting of a reactor and a subcritical block (thermal in neutronic terms). A BARS-type fast neutron reactor is used as a self quenching pulsed reactor.

The subcritical block is a tubular structure comprising laseractive components, moderator components and two reflectors (internal and external). The internal reflector material is zirconium hydride, and the external reflector material is beryllium. The pumping area containing the laseractive components consists of zirconium hydride moderator, aluminum and uraniummolybdenum fuel (95% enriched uranium).

The system operates in a pulsed mode. Fast neutrons are generated in the nuclear reactor at the pulse moment, many of which are leakage neutrons entering the subcritical block, slowing down there and inducing fissions of uranium nuclei in the laseractive components. After the pulse terminates, the reactor changes to a deeply subcritical state, and the laser pulse generation stops.

The neutron kinetics in the system under consideration is modeled based on a modified integral model.

The pulse maximum power and energy in the system’s subcritical block, as well as its weight and energytoweight ratio are selected as functionals for the optimization. The fissile material and moderator weight and the thickness of the subcritical block’s internal and external reflectors are adopted as variables.

The calculations have shown that it is possible to improve the energy characteristics of a reactorlaser system by increasing the amount of the fissile material in the block, not using the moderator in the block and fixing the thickness of the internal zirconium hydride reflector at a level of 3.1 cm. It has been shown that a change in the external beryllium reflector thickness leads to a highly multidirectional behavior of the functionals (energy and maximum power, as well as the block weight and energytoweight ratio).

### References

- Mel’nikov S.P., Sizov A.N., Sinyanskij A.A. Nuclear Pumped Lasers. Sarov. RFYAC-VNIIEF Publ., 2008, 440 p. (in Russian).
- Gulevich A.V., D’yachenko P.P., Zrodnikov A.V., Kuharchuk O.F. Pulsed Coupled Reactor System. Moscow. Energoatomizdat Publ., 2003, 360 p. (in Russian).
- Bell D., Glasstone S. Nuclear Reactor Theory. Moscow. Atomizdat Publ., 1974, 493 p. (in Russian).
- Avery R. Theory of Coupled Reactors. 1958, Proc. of 2nd Int. Conf. on Peaceful Uses of Atomic Energy. Report #1858.
- Coupled Reactor Kinetics. Proc. of National Topical Meeting American Nuclear Society. Ed. C.Chezem, W.Kohler, Texas, 1967.
- Komata M. On the Derivation of Avery’s Coupled Reactor Kinetics Equations. Nucl. Sci. and Eng., 1968, v, 38, p. 193.
- Stevenson M., Gage S. Application of a Coupled Fission Mode Approach to Modular Reactor Kinetics. J. of Nucl. Ener., 1970, v. 24, no. 1,.p. 1.
- Thayer G., Miley G., Jones B. Experimental Studies of Large Amplitude Transients in Weakly Coupled Cores. Trans. of Amer. Nucl. Soc., 1972, v, 15, no. 2, p. 925.
- Thayer G., Miley G., Jones B. An Experimental Study of Two Coupled Reactors. Nucl. Techn., 1975, v. 25, no. 1, р. 56.
- Difilippo F., Waldman R. The Kinetics of a Coupled TwoCore Nuclear reactor. Nucl. Sci. and Eng., 1976, v. 61, no. 1, p. 60.
- Kouvshinov M.I., Cherednik P.F., Ignatov I.I. Experimental Investigation of Coupled Systems Containing Pulsed Reactor BIR and Subcritical Assembly. Voprosy Atomnoi Nayki i Techniki. Ser. Physics of Nuclear Reactors, 1988, v. 2, p. 3 (in Russian).
- Takezawa H., Obara T., Gulevich A., Kukharchuk O. Criticality Analysis of Pulse Core and Laser Module Coupled Small Reactor with Low Enriched Uranium. Progress in Nuclear Energy, 2008, v. 50, no. 26, p. 304.
- Shabalin E.P. Pulsed Fast Neutron Reactors. Moscow. Atomizdat Publ., 1976, 248 p. (in Russian).
- Lomidze V.L. Pulsed Nuclear Reactors. Moscow. Znanie Publ., 1982, 63 p. (in Russian).
- Kolesov V.F. Aperiodic Pulsed Reactors. V.1, 2. Sarov. RFNC-VNIIEF Publ., 2007, 553 p. (in Russian).
- Levakov B.G., Lukin A.V., Magda E.P. Pulsed Nuclear Reactors of RFNC VNIITF. Snezhinsk. RFNC VNIITF Publ., 2002, 608 p. (in Russian).
- Gulevich A.V., Kuharchuk O.F., Pashin E.A., Polevoj V.B. A Modified Model of Neutron Kinetics of the Reactor Laser Facility. Preprint FEI2264, Obninsk, 1992, 20 p. (in Russian).
- Takezawa H., Obara T. New approach to spacedependent kinetic analysis by the integral kinetic model. Nucl. Sci. Eng., 2012, 171, p. 1.
- Gulevich A.V., Kukharchuk O.F. Analytical Estimates of Neutron Pulse Parameters in a Laser System Pumped by a Pulsed Reactor. Izvestyia vuzov. Yadernaya Energetika. 1996, no. 1, p. 37 (in Russian).
- Gulevich A.V., Kuharchuk O.F., Brezhnev A.I. Analytical Estimates of Pulse Parameters in a Modified Integral Neutron Kinetics Model for a Pulsed Reactor and a Subcritical Block. Izvestia vuzov. Yadernaya Energetika. 2016, no. 2, pp. 87-98 (in Russian).
- Polevoj V.B., Leont’ev V.V., Ovchinnikov A.V. Tarasova O.B. MMKFK2 Base Program Package for Solution of Neutron Transport Problems in Reactor Physics (MMKFK2BASE). OFAP YAR, №00371. Moscow. 1996, 78 p. (in Russian).
- MCNP – A General Monte Carlo Nparticle Transport Code, Version 4B. Ed. J. Briesmeister LANL LA12625M. 1997, 741 p.
- Berezhnoj K.V., Kuharchuk O.F. Use of the MCNP Code for Calculating the Neutronic Performance of Coupled Reactor Systems. Preprint FEI2961. Obninsk, 2002, 28 p. (in Russian).

neutron kinetics laser system pumped by nuclear reactor pulse energy and maximum power