Graded buffering high-shock-resistance bending-resistance pipe-in-pipe type guide pipe and fuel assembly

Abstract

The invention belongs to the technical field of nuclear fuel assemblies of nuclear power stations, and particularly relates to a graded buffering high-shock-resistance bending-resistance pipe-in-pipe type guide pipe and a fuel assembly. The guide pipe is composed of an outer pipe, an inner pipe and an end plug, the inner pipe is sleeved with the outer pipe, the bottom end of the inner pipe and the bottom end of the outer pipe are fixedly connected with the end plug, overflow holes are formed in the outer pipe and located at the upward position of the upper end of the inner pipe, and a plurality of bypass flow holes are formed in the position, close to the bottom, of the outer pipe in the radial direction. A plurality of buffer holes are formed in the inner pipe in the radial direction; the inner pipe is connected with the outer pipe through a plurality of connecting parts in the length direction. The overflow hole is formed in the outer pipe and located at the upward position of the upper end of the inner pipe, so that water in the guide pipe rapidly overflows when rod falling begins, and rapid rod falling is achieved; a plurality of drain holes formed in the inner pipe in the radial direction are matched with drain holes in the bottom of the end plug to achieve hydraulic buffering; crevice corrosion is relieved through an outer pipe bypass flow hole; the equivalent stiffness and the bearing capacity are improved through the multiple connecting parts, and the shock resistance and the bending resistance under high fuel consumption of the fuel assembly are improved.

Description

technical field [0001] The invention belongs to the technical field of nuclear fuel assemblies of nuclear power plants, and in particular relates to a pipe-in-pipe guide pipe and a fuel assembly with graded buffering, high shock resistance and bending resistance. Background technique [0002] The nuclear fuel assembly is composed of a number of fuel rods, guide tube parts, positioning grids, upper and lower tube seats, etc. As the fuel assembly bearing structure, the guide tube part has the following basic functions: providing continuity for the fuel assembly structure; providing insertion channels for fuel-related components; providing hydraulic buffer for the falling of control rods during reactor emergency shutdown; providing cooling for fuel-related component rods agent flow. Operating experience shows that with the deepening of the fuel consumption, the guide tube bends, which leads to poor rod drop. At the same time, the improvement of nuclear safety requirements requ...

AI Technical Summary

Problems solved by technology

The integrated reduced-diameter structure is simple, but the mechanical properties of the reduced-diameter section are poor, and it is difficult to meet the seismic requirements of the third-generation nuclear power plant with 0.3g limit earthquake motion, and the guide tube is difficult to manufacture; The connection at both ends, the sleeve connection of the casing structure is its mechanical weak link, and its mechanical properties have not been fully utilized; at the same time, both the pipe-in-pipe structure and the casing structure are prone to form dead water in the gap between the inner and outer pipes , it is easy to cause crevice corrosion, which in turn affects the bearing capacity of the guide tube

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