Izvestiya vuzov. Yadernaya Energetika

The peer-reviewed scientific and technology journal. ISSN: 0204-3327

Heterogeneous effects in simulating a fast nuclear reactor on the BFS facility

6/24/2019 2019 - #02 Physics and technology of nuclear reactors

Kazansky Yu.A. Karpovich G.V.

DOI: https://doi.org/10.26583/npe.2019.2.09

UDC: 53.088.4:621.039.7

The simulation of fast neutron reactors are modeled to compare experimental and calculated data on the neutron-physical characteristics on the zero power stands. This article discusses the BFS facility, which is in operation in Russia (Obninsk). The geometrical arrangement of materials in the actual design of reactors (fuel elements, fuel assemblies, coolant geometry) differs from the design on the BFS. This can cause differences in the experimental results at the BFS from theoretical calculations even in the case of careful observance of homogeneous concentrations of all materials of the reactor. Differences of neutron-physical parameters due to the geometry of the location of materials with the same homogeneous concentrations are called heterogeneous effect. Heterogeneous effects tend to increase with increasing reactor power and its size which is mainly due to changes in the neutron spectra.

The calculations of a number of functional values are carried out to assess the heterogeneous effects for different spatial arrangements of the reactor’ materials. The calculations were carried out for: a) heterogeneous distribution of materials in accordance with the design of a fast neutron reactor; b) heterogeneous arrangement of materials in accordance with the capabilities and design features of the BFS facility; c) a homogeneous presentation of core materials and reproduction zones.

The basic version of the calculations, in relation to which the effect called the heterogeneous shift of the functional value (HSF), was calculated and adopted by the layout of materials in accordance with the design data of the BN-1200 reactors type.

The effect of neutron leakage on the HSF as a result of calculations with different boundary conditions was estimated. All calculations were carried out at the same homogeneous concentrations of all materials for all three compositions. Calculations were also carried out when using metallic plutonium on the BFS.

The values of the following functionals were calculated for different arrangements of materials: the effective multiplication factor (reactivity), the sodium void reactivity effect, the average neutron energy causing fission, and the ratios of the radioactive capture to the fission cross sections for 239Pu.

The calculations were performed using the Monte Carlo software package for neutron physics modeling Serpent 2.1.30 (VTT, Finland) and the libraries of the evaluated nuclear data ENDF/B-VII.0 and JEFF-3.1.1. The effect of various methods of materials replacing on the values of keff was greatest when replacing the dioxide of fissile material with metal of the same materials (about 1.6%). The homogeneous composition reduces the keff by about 0.4%.

The average neutron energy causing fission significantly depends on the leakage of neutrons and the presence of sodium (the average energy of the neutrons increases when sodium reaches about 100 keV, that is, by about 11 – 13%). Replacing fissile metallic materials with their dioxide on the BFS facility (while maintaining homogeneous concentrations, including oxygen) reduces the average energy of the neutrons causing fission by about 60 keV.

The highest values of HSF, reaching 65%, are observed when calculating the sodium void reactivity effect with a homogeneous arrangement of materials, but when calculating the model of the reactor at BFS it is 1.5%. In the absence of neutron leakage (infinitely extended medium), the sodium void reactivity effect becomes positive and the HSF is 4 – 7%.

The heterogeneous effect of α for 239Pu significantly depends (6 – 8%) only on the replacement of metallic plutonium with its dioxide (naturally, while maintaining homogeneous concentrations).

References

  1. Lell R.M., Morman J.A., Schaefer R.W., McKnight R.D. ZPR36 assembly 7 experiments: a fast reactor core with mixed (Pu,U)3oxide fuel and sodium with a thick depleted uranium reflector. ZPR-LMFR-EXP-001. International Handbook of Evaluated Reactor Physics Benchmark Experiments, NEA OECD, 2013.
  2. Ishikawa M., McKnight R.D. ZPPR310A experiment: a 650 MWe3class sodium3cooled MOX3 fueled FBR homogeneous core mock3up critical experiment with two enrichment zones and nineteen control rod positions. ZPPR-LMFR-EXP-001. International Handbook of Evaluated Reactor Physics Benchmark Experiments, NEA OECD, 2013
  3. Rozhikhin Y., Semenov M. BFS361 assemblies: critical experiments of mixed plutonium, depleted uranium, graphite and lead with different reflectors. BFS1-LMFR-EXP-002. International Handbook of Evaluated Reactor Physics Benchmark Experiments, NEA-OECD, 2013.
  4. Leipunsky A.I., Orlov V.V., Kazansky Yu.A., Zinoviev V.P., Ukraintsev F.I., Shapar A.V., Klintsov N.A. Complex BFS-1 – microtron for studying the neutron spectra of fast reactors. Atomnaya Energiya. 1974, v. 36, no.1, pp.3-5 (in Russian).
  5. Bouget Y., Hammer P., Periot R., Kazansky Yu. Etude d’interaction de barre dans les assemblages critiques BFS324316 (Obninsk) et MASURKA (Kadarache). Fast Reactor Physics, (IAEA), 1980, pp. 21-38.
  6. Bickel W., Engelmann P., Wittek G. Safety report for the fast zero3power arrangement Karlsruhe SNEAK. Nuclear Research Center Karlsruhe, 1965, 353 p.
  7. Hirota J, Nomoto S, Hirakawa N, Nakano M. Studies of the criticality of 20% enriched uranium fast critical assemblies (FCA-I). Nuclear Science and Technology. 1969, v. 6, pp. 35-42.
  8. Rowlands J., Zukeran A. The ZEBRA MOZART Programme. ZEBRA-LMFR-EXP-002. International Handbook of Evaluated Reactor Physics Benchmark Experiments, NEA OECD, 2013.
  9. Kusters H., Pilati S. The present accuracy of physics characteristics ofunirradiated fast reactor cores. Progress in Nuclear Energy. 1985, v. 16, no. 3, pp. 201-229.
  10. Le Sage L.G., Lineberry M.J., McFarlane H.F. Current status of fast reactor physics reactivity coefficients. Progress in Nuclear Energy. 1985, v. 16, no. 3, pp. 231-250.
  11. Bednyakov S.M., Golubev B.N., Dulin V.A., Kozlovtsev V.G., Mamontov V.F. Experimental justification of methods for assessing the critical perturbations of fast assemblies with small samples. Atomnaya Energiya. 1988, v. 65, no. 6, pp. 426-430 (in Russian).
  12. Belov S.P., Dulin V.A., Zhukov A.V., Kuzin E.N., Mozhaev E.K., Sitnikov N.I., Tsibulya A.M., Shapar A.N., Seifert E., Kuntsman B., Heinzelman B. Effects of small heterogeneity of fast critical assemblies.. Atomnaya Energiya. 1989, v. 66, no. 1, pp. 13-17 (in Russian).
  13. Leppaanen J. Serpent – a Continuous3Energy Monte Carlo Reactor Physics Burnup Calculation Code. User’s Manual. VTT Technical Research Centre of Finland, 2015.
  14. Leppaanen J., Viitanen T. Cross section libraries for Serpent 1.1.7., Espoo, VTT Technical Research Centre of Finland, 2013, 58 p.
  15. Orlov V.V., Smirnov V.S., Filin A.I. Deterministic safety of BREST reactors. Energiya, Ekonomika, Tekhnologiya, Ecologiya. 2003, no. 10, pp. 13-20 (in Russian).
  16. Hammel G., Okrent D. Reactivity Coefficients in Large Fast Nuclear Reactors. Moscow. Atomizdat Publ., 1975, pp.69-106 (in Russian).
  17. Available at: https://www.ippe.ru/nuclear-power/fast-neutron-reactors/122-bn1200-reactor (accessed May 21, 2019) (in Russian).
  18. Available at: http://www.innov-rosatom.ru/files/articles/b4589ee208b5b20af9c07c28921d4891.pdf (accessed May 21, 2019) (in Russian).

heterogeneous effect simulation of nuclear reactors critical test benches fast neutron reactor BN sodium void reactivity effect neutron physical calculation Monte Carlo

Link for citing the article: Kazansky Yu.A., Karpovich G.V. Heterogeneous effects in simulating a fast nuclear reactor on the BFS facility. Izvestiya vuzov. Yadernaya Energetika. 2019, no. 2, pp. 105-116; DOI: https://doi.org/10.26583/npe.2019.2.09 (in Russian).

Open PDF file