Izvestiya vuzov. Yadernaya Energetika

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

Hydrodynamic Characteristics of Flow in a Fuel Rod Bundle of a Fuel Assembly for the RITM Reactor of a Low-Power Nuclear Power Plant

9/17/2026 2026 - #03 Thermal physics and thermal hydraulics

Dmitriev S.M. Demkina T.D. Dobrov A.A. Doronkov D.V. Pronin A.N. Ryazanov A.V.

DOI: https://doi.org/10.26583/npe.2026.3.06

UDC: 621.039

The article presents the results of an experimental study of the hydrodynamic characteristics of flow in a fuel rod bundle of a fuel assembly (FA) intended for the core of the RITM reactor of a low-power nuclear power plant (LNPP, SMR). The experiments were carried out on a research test bench with an air working medium using the theory of hydrodynamic modeling. The experimental model is a set of rods with a complex, irregular arrangement pattern, simulating a fuel rod bundle of a standard FA. The assessment of the intensity of secondary flows behind a spacer grid (SG) was carried out based on the analysis of the values and topology of the velocity vector components obtained by applying a pneumometric measurement method using a five-channel probe, and the overall direction of the secondary flows was determined by the method of injecting a contrast tracer. The experimental data were presented in the form of cartograms and graphical dependences of dimensionless quantities of velocity and tracer concentration. The experimental results made it possible to reveal the heterogeneity of the axial flow velocity field structure in the fuel rod bundle, as well as the direction and intensity of its secondary flows. At the periphery of the fuel rod bundle, areas of low axial flow velocity are recorded, retaining their structure behind the SG at a distance of more than L/dh ≈ 10. The difference in axial velocity values in the field of regular cells averaged 10 – 15%. Behind the SG at a distance of L/dh ≈ 10, at the periphery and near the central displacer, low-intensity secondary transverse flows persist, the value of the dimensionless transverse velocity being ≈ 0.08, and their direction is influenced by the degree of crowding of cells by the SG plates. The overall structure of the secondary transverse flows and the structure of the axial velocity field are mainly due to the irregular pitch of the rods in the bundle, which makes the gaps between them uneven and significantly changes the direction of secondary flows; the central displacer, which creates two types of secondary flows: along its surface and away from it into the field of regular cells; as well as the use of a shroud in the FA design, which caused a decrease in the axial flow velocity at the periphery and intensified the displacement of part of the flow from the periphery into the regular cells. The research results have been used by specialists of JSC “Afrikantov OKBM” to substantiate engineering solutions in the design of cores.

References

  1. Petrunin V.V. Reactor Units for Small Nuclear Power Plants. Herald of the Russian Academy of Sciences. 2021;91(3):335–346. DOI: https://doi.org/10.1134/S1019331621030126
  2. Belyaev V.M., Bol’shukhin M.A., Pakhomov A.N., Khizbullin A.M., Lepekhin A.N., Polunichev V.I., Veshnyakov K.B., Sokolov A.N., Turusov A.Y. The World’s First Floating NPP: Origination and Direction of Future Development. Atomic Energy. 2020;129(1):27–34. DOI: https://doi.org/10.1007/s10512-021-00707-w
  3. Petrunin V.V., Sheshina N.V., Fateev S.A., Kurachenkov A.V., Shchekin D.V., Brykalov S.M., Bezrukov A.A. Scientific and technical aspects of developing a RITM-200N innovative reactor for SNPPS. Atomic Energy. 2023;134(1-2):1–10. DOI: https://doi.org/10.1007/s10512-023-01020-4
  4. Samoilov O.B., Romanov A.I., Galitskikh V.Y., Zakharychev A.A., Morozov O.A, Mitrofanov A.V., Silaev V.Y. Analysis of operating experience of first generation nuclear icebreaker cores. Database in support of development of new nuclear icebreakers and floating nuclear power units. Nuclear propulsion reactor plants. Life cycle management technologies. 2023;3:16–24. EDN: BLTGBW.
  5. Zverev D.L., Fadeev Y.P., Pakhomov A.N., Galitskikh V.Y., Polunichev V.I., Veshnyakov K.B., Kabin S.V., Turusov A.Y. Reactor installations for nuclear icebreakers: origination experience and current status. Atomic Energy. 2020;129(1):18–26. DOI: https://doi.org/10.1007/s10512-021-00706-x
  6. Romanov A.I., Papotin V.Y., Tuturkin M.Y. Reactor core development for SNPP and FPU current status and development trends. PAST. Ser.: Materials technology and new materials. 2023;5:86–111 (in Russian).
  7. Zverev D.L., Samoilov O.B., Morozov O.A., Zakharychev A.A., Silaev V.Y., Matyash P.B., Vishnev A.Yu., Kashka M.M., Darbinyan O.E. The cores of operating nuclear icebreakers. Sudostroenie. 2020;1:13–16 (in Russian).
  8. Kulakov G.V., Vatulin A.V., Ershov S.A., Konovalov Y.V., Morozov A.V., Savchenko A.M., Sorokin V.I., Romanov A.I., Morozov O.A., Shishin V.Y., Sheldyakov A.A. Development of fuel for low power reactors and floating power units. Status and prospects. PAST. Ser.: Materials technology and new materials. 2020;1:116–128 (in Russian).
  9. Zakharychev A.A., Iksanova G.S., Kupriyanov A.V., Osin A.B., Petrunin V.V., Samoilov O.B., Shipov D.L. Methodological issues and results of experimental and computational studies of critical heat flows in RITM-200 reactor fuel assemblies for small NPP. Atomic Energy. 2021;130(2):63–68. DOI: https://doi.org/10.1007/s10512-021-00775-y
  10. Dmitriev S.M., Gerasimov A.V., Dobrov A.A., Doronkov D.V., Pronin A.N., Ryazanov A.V., Solntsev D.N., Khrobostov A.E., Noskov A.S., Samoilov O.B., Shvetsov Yu.K., Shipov D.L. Experimental investigation of the coolant flow in the VVER reactor core with TVSA fuel assemblies. Izvestiya vuzov. Yadernaya Energetika. 2020;4:25–36. DOI: https://doi.org/10.26583/npe.2020.4.03 (in Russian).
  11. Dmitriev S.M., Gerasimov A.V., Dobrov A.A., Doronkov D.V., Pronin A.N., Solntsev D.N., Khrobostov A.E., Shvetsov Y.K., Shipov D.L. Hydrodynamics and mixing of a coolant in the core of the VVER with fuel assemblies of different designs. Thermophysics and Aeromechanics. 2019;26(6):845–860. DOI: https://doi.org/10.1134/S0869864319060064
  12. Gukhman A.A. Introduction to the theory of similarity. Moscow, High School Publ., 1973, 296 p.
  13. Gukhman A.A. Application of similarity theory to the study of heat and mass transfer processes (transfer processes in a moving medium). Moscow, High School Publ., 1974, 328 p.

core fuel assembly fuel rod flow axial velocity transverse velocity contrast tracer secondary flows

Link for citing the article: Dmitriev S.M., Demkina T.D., Dobrov A.A., Doronkov D.V., Pronin A.N., Ryazanov A.V. Hydrodynamic Characteristics of Flow in a Fuel Rod Bundle of a Fuel Assembly for the RITM Reactor of a Low-Power Nuclear Power Plant. Izvestiya vuzov. Yadernaya Energetika. 2026, no. 3, pp. 80-94; DOI: https://doi.org/10.26583/npe.2026.3.06 (in Russian).

Open PDF file