Analysis of experimental data on melting and relocation of a metal melt on a cylindrical surface
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DOI: 10.1134/S0869864320030142
Analysis of experimental data on melting and relocation of a metal melt on a cylindrical surface* P.D. Lobanov1,2, E.V. Usov1, A.I. Svetonosov1,2, and S.I. Lezhnin1,2 1
Nuclear Safety Institute RAS, Moscow, Russia
2
Kutateladze Institute of Thermophysics SB RAS, Novosibirsk, Russia
E-mail: [email protected] (Received November 25, 2019; revised December 26, 2019; accepted for publication February 10, 2020) The paper presents the results of experimental study on melting simulator of the fuel coating pin cladding made of alloy Pb (44.5 %)-Bi (55.5 %) and the flow of the melt on the surface of the heated rod. Experiments were conducted for different parameters: heat release, initial temperature, linear size, and the cladding thickness. All experiments provided the video of the process of formation and relocation of the melt, and the cladding temperature and mass loss rate were measured. The paper presents analysis of melt formation and relocation on the fuel rod imitator surface. Keywords: nuclear power, fuel element, severe incident, melt, film, rivulets.
Relevance of research Development of a severe accident at nuclear power plants is accompanied by heat misbalance in the reactor core, the growth of the coolant temperature, its boiling and dryout, and, therefore, melting of the cladding of fuel rods and relocation of the produced melt. The design of fuel rods in fast-neutron reactors assumes the active part with the major heat generation and a colder part of element comprising the depleted uranium (the blanket) with almost zero heat release. The existence of cold-blanket part can influence the molt evolution due to solidifying. Therefore, the study of laws of melting and melt motion over the fuel rods surface is a relevant problem. Objectives The research of accident-related processes in fuel rods of fast reactors was initiated in 1970–80s from the large-scale reactor experiments using the single fuel rods and model fuel assemblies (FA) comprising from 7 to 19 rods [1–9]. This kind of study was focused on destruction of cladding and fuel, and behavior of FA blanket during accidents with a decrease in the coolant flow rate and instant blockage of channel in the emergency FA. The objective of *
Research was financially supported by the Russian Science Foundation (Grant # 18-79-10013).
P.D. Lobanov, E.V. Usov, A.I. Svetonosov, and S.I. Lezhnin, 2020
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P.D. Lobanov, E.V. Usov, A.I. Svetonosov, and S.I. Lezhnin
experiments was the study of main laws of fuel rod and FA behavior in emergency situations. The experimental imitation of accident includes numerous processes: heat up of the coolant, fuel rod cladding, fuel, and FA blanket, heat transfer between the coolant and cladding surface, coolant boiling, dryout, melting and motion of the formed melt, and heat transfer between melt and coolant. The shortcoming of experiments is complicated procedure and lack of specific information on the development of separate processes that accompany the fuel rod destruction, for example, mel
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