Cracks in perforated heat-releasing nuclear fuel

What is it about?

The conditions of limit equilibrium of a crack with end zone are formulated with regard to criterion of ultimate stretching of material’s bonds. This condition enables to evaluate the critical intensity of internal heat sources and fracture toughness of the nuclear fuel material. A model of a crack with end prefracture zones with bonds between the faces enables to study regularities of distribution of forces in bonds for different laws of deformation, carry out analysis of limit equilibrium of the material with regard to deformational fracture criterion; to determine conditions of equilibrium and increase of the sizes of the end prefracture zones. Analysis of limit-equilibrium state of the heat-releasing material, at which the growth of a crack happens, is reduced to parametric investigation of the combined system of algebraic system and the fracture criterion at different thermal-physical and mechanical characteristics of the nuclear fuel parameters. The solution of the obtained system enables to determine the critical value of intensity of the internal heat sources, the sizes of end prefracture zones and forces in bonds in the limit equilibrium state under which cracks grow in the material of nuclear fuel. The strength reduction degree of nuclear fuel penetrated by cylindrical channels, whose axes are parallel, depends on the channel’s size, length of surface cracks and the value of the heat release intensity. Reduction of the hole’s radius leads to the drop of strength material of nuclear fuel.

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Why is it important?

The numerical realization of the obtained equations allows to solve the following practically important design problems: to estimate the guaranteed resource of the nuclear fuel material with regard to expected defects and loading conditions; to establish the admissible presence of defects and maximal value of heat release intensity providing sufficient reliability reserve; to choose nuclear fuel material with necessary complex of static and cyclic crack resistance characteristics.