EXPERIMENTAL STUDY OF LOCAL HYDRODYNAMICS AND MASS EXCHANGE PROCESSES OF COOLANT IN FUEL ASSEMBLIES OF PRESSURIZED WATER REACTORS

The results of experimental studies of local hydrodynamics and mass exchange of coolant flow behind spacer and mixing grids of different structural versions that were developed for fuel assemblies of domestic and foreign nuclear reactors are presented in the article. In order to carry out the study the models of the following fuel assemblies have been fabricated: FA for VVER and VBER, FA-KVADRAT for PWR-reactor and FA for KLT-40C reactor. All the models have been fabricated with a full geometrical similarity with full-scale fuel assemblies. The study was carried out by simulating the flow of coolant in a core by air on an aerodynamic test rig. In order to measure local hydrodynamic characteristics of coolant flow five-channel Pitot probes were used that enable to measure the velocity vector in a point by its three components. The tracerpropane method was used for studying mass transfer processes. Flow hydrodynamics was studied by measuring cross-section velocities of coolant flow and coolant rates according to the model cells. The investigation of mass exchange processes consisted of a study of concentration distribution for tracer in experimental model, in determination of attenuation lengths of mass transfer processes behind mixing grids, in calculating of inter-cellar mass exchange coefficient. The database on coolant flow in fuel assemblies for different types of reactors had been accumulated that formed the basis of the engineering substantiation of reactor cores designs. The recommendations on choice of optimal versions of mixing grids have been taken into consideration by implementers of the JSC “OKBM Afrikantov” when creating commissioned fuel assemblies. The results of the study are used for verification of CFD-codes and CFD programs of detailed cell-by-cell calculation of reactor cores in order to decrease conservatism for substantiation of thermal-mechanical reliability.

1. Dmitriev S. M., Barinov A. A., Borodina V. E., Khrobostov A. E. (2014) Towards the Methodology of Thermotechnical Reliability of Active Zones of Water Power Reactors. Trudy Nizhegorodskogo Gosudarstvennogo Tekhnicheskogo Universiteta Imeni R. E. Alekseeva [Proceedings of the Nizhny Novgorod State Technical University n. a. R. E. Alekseev], (2), 98–108 (in Russian).

2. Dmitriev S. M., Zverev D. L., Bykh O. A., Panov Iu. K., Sorokin N. M. (2013) Basic Equipment of a Shell-Type Thermal Neutron Reactor Nuclear Power Plant. Moscow, Mashinostroyeniye. 415 (in Russian).

3. Zhukov A. V., Sorokin A. P., Matyukhin N. M. (1989) Interchannel Exchange in Fuel Assemblies of Fast Reactors: Theoretical Fundamentals and the Physics. Moscow, Energoatomizdat. 130 (in Russian).

4. Gukhman ?. ?. (1973) Introduction into the Theory of Similarity. 2nd ed. Moscow, Vysshaya Shkola. 296 (in Russian).

5. Borodin S. S., Dmitriev S. M. (2006) Specific Features of Hydrodynamics of the Coolant in Alternative Fuel Assemblies of the VVER-1000 Reactors by Using of Mixing Grids. Izvestia Vysshikh Uchebnykh Zawedeniy. Yadernaya Energetika[Nuclear Power Production. Proceedings of Higher Educational Institutions], (4), 70–76 (in Russian).

6. Dmitriev S. M., Borodin S. S., Legchanov M. A., Solntsev D. N., Sorokin V. D., Khrobostov A. E. (2012) Experimental Studies of Hydrodynamic and Mass-Transfer Properties of Coolant Flow in VVER Fuel Assemblies TVSA. Atomic Energy, 113 (5), 252–257. DOI: 10. 1007/s10512-013-9638-6.

7. Borodin S. S., Dmitriev S. M., Legchanov M. A., Novikova O. Iu., Solntsev D. N., Khrobostov A. E. (2010) Study of the Mass Transfer Characteristics and Efficiency of Mixing Grids of FA-ALFA of VVER Reactors. Trudy Piatoi Ros. Nats. Konf. po Teploobmenu. T. 1 [Proceedings of the Fifth Russian National Conference on Heat Exchange. Vol. 1]. Moscow, Publishing House MEI, 177–180 (in Russian).

8. Borodin S. S., Dmitriev S. M., Legchanov M. A., Solntsev D. N., Sorokin V. D., Khrobostov A. E. (2013) Specific Features of Local Hydrodynamics and Mass Exchange Processes of Coolant in Fuel Assemblies of VVER and PWR Reactors with Mixing Grids. Teplovye Protsessy v Tekhnike [Thermal Processes in Engineering], 5 (3), 98–107 (in Russian).

9. Dmitriev S. M., Khrobostov A. E., Varentsov A. V., Dobrov A. A., Doronkov D. V., Sorokin V. D., Samoilov O. B. (2014) Combined Numerical and Experimental Investigations of Local Hydrodynamics and Coolant Flow Mass Transfer in Kvadrat-Type Fuel Assemblies of PWR Reactors with Mixing Grids. Teploenergetika [Thermal Engineering], 61 (8), 558–565. DOI: 10.1134/S0040363614080050.

10. Varentsov A. V., Doronkov D. V., Kupricheva E. S., Solntsev D. N., Sorokin V. D. (2012) Investigation of Local Mass Transfer and Efficiency of Spacer Grids of Fuel Assembly of Reactors KLT-40?. Trudy Nizhegorodskogo Gosudarstvennogo Tekhnicheskogo Universiteta Imeni R. E. Alekseeva [Proceedings of the Nizhny Novgorod State Technical University

11. n. a. R. E. Alekseev], (1), 107–113 (in Russian).

12. Varentsov A. V., Ziablitsev D. V., Solntsev D. N., Pronin A. N., Morozkin O. N. (2012) Experimental Study of Local Hydrodynamic Characteristics of the Flow in Fuel Assemblies of the Reactor Installation of Floating Nuclear Power Plant. Trudy Nizhegorodskogo Gosudarstvennogo Tekhnicheskogo Universiteta Imeni R. E. Alekseeva [Proceedings of the Nizhny Novgorod State Technical University n. a. R. E. Alekseev], (3), 118–125 (in Russian).

13. Varentsov A. V., Dmitriev S. M., Dobrov A. A., Solntsev D. N., Khrobostov A. E. (2013) Experimental and Numerical Researches of Hydrodynamics and Mass Transfer of Coolant Flow in Experimental Model of KLT-40? Reactor Fuel Assembly. Nauchno-Tekhnicheskiy Vestnik Povolzhya [Scientific and Technical Volga Region Bulletin], (3), 114–119 (in Russian).