Izvestiya vuzov. Yadernaya Energetika

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

Hydrodynamics of Turbulent Coolant Flow at the Outlet of the Fuel Assembly of the RITM Reactor of a Low-Power Nuclear Power Plant

3/27/2026 2026 - #01 Thermal physics and thermal hydraulics

Dmitriev S.M. Demkina T.D. Dobrov A.A. Doronkov D.V. Pronin A.N. Ryazanov A.V. Karpuhov O.O. Samoilov O.B. Shipov D.L.

DOI: https://doi.org/10.26583/npe.2026.1.05

UDC: 621.039

The article presents the results of an experimental study and comparative analysis of the coolant hydrodynamics at the outlet of a fuel assembly with heads of three different designs. Fuel assemblies are designed for the core of the RITM reactor of a low-power nuclear power plant. The objective of the work was to study the axial flow velocity at the outlet of the fuel element bundle and behind heads of different designs, as well as to determine the areas of the fuel element bundle from which the flow is most likely to enter the selection pipe to the resistance thermometer. The experiments were carried out on a research bench with an air working environment on a model of the outlet section of the fuel assembly. The model consisted of a fragment of the fuel element bundle, as well as replaceable mock-ups of heads of three design options and a plate for installing the fuel assemblies. The pneumometric method was used to determine the axial flow velocity. The method of injection of a contrast admixture was used to identify the areas of the fuel element bundle from which the flow enters the selection pipe. The hydrodynamic pattern of the flow is presented by cartograms of the axial velocity and contrast admixture. The experimental results allowed us to detail the structure of the turbulent flow and draw the following conclusions. The shape of the flow section of the head confuser has little effect on the axial flow in front of the outlet spacer grid. The influence of the head geometry is manifested when the coolant flows out of the bundle of fuel elements. The shape of the flow section of the confuser has little effect on the axial flow velocity. The greatest contribution to the change in axial velocity is made by a decrease in the area of the flow section of the heads. The heterogeneity of the structure of flows from the head windows is determined by the selection pipe, which blocks part of the flow section. The flow flowing out of the head with three windows is the most heterogeneous. When the flow flows in the head confusers, the process of its mixing is recorded, expressed by the displacement of the impurity in the direction of the selection pipe. The greatest transverse displacement of the impurity occurs in the confuser of the head with three windows. To minimize the effect of flows with different temperatures on the resistance thermometer readings, it is necessary to use heads with three windows. The research results were used by specialists of JSC Afrikantov OKBM to substantiate engineering solutions when designing cores.

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core fuel assembly head extraction pipe coolant axial velocity contrast agent

Link for citing the article: Dmitriev S.M., Demkina T.D., Dobrov A.A., Doronkov D.V., Pronin A.N., Ryazanov A.V., Karpuhov O.O., Samoilov O.B., Shipov D.L. Hydrodynamics of Turbulent Coolant Flow at the Outlet of the Fuel Assembly of the RITM Reactor of a Low-Power Nuclear Power Plant. Izvestiya vuzov. Yadernaya Energetika. 2026, no. 1, pp. 52-70; DOI: https://doi.org/10.26583/npe.2026.1.05 (in Russian).

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