Mathematical modeling of development of beyond design basis accident in integral fast-neuron reactors vessel

The process of nonstationary deformation of construction of the fast reactor with liquid metal coolant under postulated ULOF beyond design basis accident is examined. This type of accident includes core melting caused by disconnection of the main circulation pump arrangements of the primary circuit with the associated failure of the emergency protection. As a result of core melting, the area with a high energy level pressure is created. It is filled with sodium vapor. The progressive expansion of the energy area in the coolant leads to an increase of stress-strain state level of the reactor vessel and may lead to its destruction. The reactor facility must save integrity, provide localization of consequences of beyond design basis accident inside of the pressure vessel and avoid dangerous radiation effects on personnel of nuclear power station and the environment in these conditions. Current Lagrangian formulation is used for the description of coolant motion and structural elements of the reactor. The equation of motion derives from the balance of virtual capacity. Equations of the theory plastic flow are used in physical relations for metals. Deviatoric stress components are assumed to be equal to zero in the coolant; and the equation between hydrostatic pressure and density is taken as a state equation of quasiacoustic type. The contact between the coolant with structural elements of the reactor is simulated by the conditions of non-penetration. The problem solution is based on the method of moment schema of FEM and explicit finite-difference time integration scheme of the “cross” which are implemented in the computing system “Dynamics 3”. The deformation of the fast reactor vessel is investigated numerically in the ULOF beyond design basis accident. The possibility of localizing effects consequences of beyond design basis accident inside of the pressure vessel of the reactor is analyzed.