Authors & Affiliations
Ashurko Yu.M., Kascheev M.V.
A.I. Leypunsky Institute for Physics and Power Engineering, Obninsk, Russia
Ashurko Yu.M. – Head of Laboratory, Cand. Sci. (Tech.), A.I. Leypunsky Institute for Physics and Power Engineering.
A complete mathematical model has been developed for the first time for numerical analysisof severe off-design accidents in sodium cooled fast reactors. The developed model enables one to answer the question of the possibility of containment of molten fuel in the reactor vessel. The computational domain under consideration is multiply connected. The mathematical simulation of sub-domains as porous bodies is performed using the laws of conservation of mass, momentum, and energy, written in the form of equations of continuity, motion, and energy in two-dimensional cylindrical coordinates. The problem of formation of heat-generated layer on the lower end shield has been solved. There was obtained solution of the problem on the movement ofvariable mass vapor bubble in liquid. The result have been used to describe the heat sources originated due to vapor condensation above heatgenerated layer.
The developed numerical model is implemented in the form of BRUT computer code. Verification of the code’s individual blocks has revealed anadequate agreement of the calculation results and available experimental data as well as analytical solution. Using BRUT code there was performed calculation analysis of fast reactor severe accident wherein complete melting of fuel subassemblies in the center of the reactor core and partial melting of peripheral subassemblies are considered. Thereby, in accordance with the calculation results on the considered above accident melted fuel is retained inside of the reactor vessel. The BRUT codewas used for calculation of the postulated severe accident wherein occurs complete melting of fuel subassemblies of reactor core at low power reactor BN.
To effectuate fast evaluations of parameters and,foremost, time of melt-through of designs there was developed mathematical model in which the taskis solved in one-dimensional approach. By the BRUT-O code, developed on the basis of one-dimensionalmathematical model, calculation of accident wherein occurs complete melting of fuel subassemblies in the center of the reactor core and partial melting of peripheral fuel subassemblies is carriedout. It is shown that time for melt contact with the pressure-header upper plate calculated by the BRUT-O code is less than the similar time obtained by the BRUT code to 10%.
fast reactor, mathematical model, vessel of reactor, heat-generated layer, molten fuel, heat sinks, severe accident, computational domain, vapor bubble, vapor condensation
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