Complex geometry channels in the coolant circuits of the nuclear power installations (NPI) causes the generation of stable vortices. Infra- and sound frequency oscillations of elements in the transport NPI thermo-hydraulic systems are created by large vortex structures. Matching oscillation frequencies of the coolant and natural oscillation frequency of the vessel can lead to vibration processes. Whereas vibration processes have an impact on the transport NPIs reliability and safety.
The first circuit coolant flow through the downtake header is considered as the first problem, which consists of the three computational experiments series: 1 — without fluid swirling in the inlet; 2 — with fluid swirling in the inlet along with centrifugal pumps impact; 3 — with non-equal coolant flow rate in the inlets. Results of the 2nd and 3rd cases of the first problem show that large scale vortex structures occur in the downtake headers of the NPI. Large vortex structures in the nuclear reactor active zone can lead to the decreasing of flow rate in center of the active zone, which can cause the non-equal coolant and energy distribution.
Large scale vortices are typical also for coolant flow through the pipe systems with elbows. Typical geometric primitives of the pressurizer pipe systems were considered to analyze this problem.
The second problem represents the coolant flow process through the pipeline section with horizontal and vertical bended parts. Two cases of the problem were considered: 1 — the “hot” problem, considering the coolant flow process from reactor to pressurizer; 2 — the “cold” problem, considering the coolant flow process from pressurizer to reactor through the curved pipeline. The obtained results of the velocity fields, pressure and temperature contours determines the correlation between temperature and velocity fields. Both in “cold” and “hot” cases in the initial section of the pipeline the coolant moves quicker along the outer side of the bend, creating the local temperature difference about 200 °C. The non-uniform temperature distribution in the cross section of the pipe can lead to the thermocycling processes, which impact to the pipe systems reliability and operation life.
Coolant flow in the more complex pipeline was considered in the third problem. The pipeline consisted of the five various direction bends. The main purpose of this problem was investigation of the various direction bends impact to the large-scale flow vortex generations in the cross sections of the pipeline. The computation experiment results showed that vortex structure, which was formed by the first two bends saved at the 20D length straight0line section. The single horizontal bends cause to the classic Dean vortices, whereas the combination of the opposite bends significantly complicated the flow structure. The combination of the horizontal and vertical bends can lead to the large-scale one-directional swirling flow.
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Gusev B.D., Kalinin R.I., Blogovecshenskiy A.Y. Gidrodinamicheskie aspekty nadezhnosti sovremennykh ehnergeticheskikh ustanovok [Hydrodynamic issues of the modern nuclear power facility safety]. Leningrad: Energoatomizdat, 1989. 216 p. In Russ
Mitrofanova O.V. Gidrodinamika i teploobmen zakruchennykh potokov v kanalakh yaderno-ehnergeticheskikh ustanovok [Hydrodynamics and heat transfer of swirling flows in the channels of nuclear power plants]. Moscow: FIZMАTLIT, 2010. 288 p. In Russ.
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