COMPARISON OF NEUTRON SPECTRUM IN THE WWR-K REACTOR WITH LEU FUEL AGAINST HEU ONE

WWR-K is the research tank-type light-water heterogeneous reactor. Reactor operation started in 1967 with enrichment36 % in uranium-235. In 2016 reactor conversion to low-enriched uranium fuel (19.7 % in uranium-235) was implemented with the VVR-KN-type fuel assemblies (FA). In view of reactor operation, compact configuration of the core was chosen, where, following fuel burning up, side water reflector is gradually changed by beryllium one. Besides, an amount of work elements of the reactor control and protection system is increased in the new reactor core.
Following results of measurement of the thermal neutron flux density, carried out in the core center in course of reactor physical startup, it has increased up to 2·10¹⁴ cm^-2s^-1. Thus, in terms of experimental capacities, reactor has gained after conversion in attractiveness.
As is known, uranium fission is accompanied by generation of neutrons, which energies obey the Watt’s spectrum, that is, the spectrum peak is associated with the neutrons having the energy 0.7 MeV, whereas the neutron average energy comprises 2 MeV. Due to an enhanced amount of uranium-238 in the new low-enriched uranium fuel FA, neutron spectrum is making «harder».
In the presented paper, neutron spectra in the core irradiation channels of re calculated by means of the computer code MCNP, and comparison of neutron spectra in the WWR-K reactor core with high-enriched uranium fuel against lowenriched fuel is conducted.

1. Аринкин Ф.М., Шаймерденов А.А., Гизатулин Ш.Х., Дюсамбаев Д.С., Колточник С.Н., Чакров П.В., Чекушина Л.В. Конверсия активной зоны исследовательского реактора ВВР-К. – Атомная энергия, 2017, т. 123, № 1 – с. 15–20.

2. Возобновление эксплуатации реактора ВВР-К. Сборник статей. Алматы, ИАЭ НЯЦ РК, 1998 – 248 с.

3. MCNP – A General Monte Carlo N-Particle Transport Code, Version 5. - Los Alamos National Laboratory, LA-UR-03-1987, 2008.

4. MCNP6 User’s Manual - Los Alamos National Laboratory, LA-CP-13-00634, 2013

5. M.B. Chadwick, M. Herman, P. Obložinský, M.E. Dunn, Y. Danon, A.C. Kahler, D.L. Smith, B. Pritychenko, G. Arbanas, R. Arcilla, R. Brewer, D.A. Brown, R. Capote, A.D. Carlson, Y.S. Cho, H. Derrien, K. Guber, G.M. Hale, S. Hoblit, S. Holloway, T.D. Johnson, T. Kawano, B.C. Kiedrowski, H. Kim, S. Kunieda, N.M. Larson, L. Leal, J.P. Lestone, R.C. Little, E.A. McCutchan, R.E. MacFarlane, M. MacInnes, C.M. Mattoon, R.D. McKnight, S.F. Mughabghab, G.P.A. Nobre, G. Palmiotti, A. Palumbo, M.T. Pigni, V.G. Pronyaev, R.O. Sayer, A.A. Sonzogni, N.C. Summers, P. Talou, I.J. Thompson, A. Trkov, R.L. Vogt, S.C. van der Marck, A. Wallner, M.C. White, D. Wiarda, P.G. Young, "ENDF/B-VII.1: Nuclear Data for Science and Technology: Cross Sections, Covariances, Fission Product Yields and Decay Data", Nucl. Data Sheets 112(2011)2887.