GB2523965A

GB2523965A - Grid structure with flow hybrid coordination function in nuclear fuel assembly

Info

Publication number: GB2523965A
Application number: GB1512370.6A
Authority: GB
Inventors: Tao Lei; Jie Chen; Yuan Peng; Huayang Cheng; Shiquan Zhang; Hong Zhang; Qing Lu; Zhong Xiao; Lin Zhang; Jing Yong
Original assignee: Nuclear Power Institute of China
Current assignee: Nuclear Power Institute of China
Priority date: 2012-12-20
Filing date: 2013-12-12
Publication date: 2015-09-09
Anticipated expiration: 2033-12-12
Also published as: AR094172A1; CN103021478A; GB201512370D0; WO2014094566A1; CN103021478B; GB2523965B; ZA201505214B

Abstract

A grid structure with a flow mixing coordination function in a nuclear fuel assembly comprises grids formed by vertically interlacing multiple stripes (3), a pair of mixing wings (5) being respectively provided at two sides of the top of each intersection of the stripes (3), and each stripe (3) concaving inwardly to form a convex structure (2) with a U-shaped cross-section on the stripe. Coordination between a clamping system and a mixing system is realized by using the convex structure, and the mixing performance of the grid structure is enhanced, thereby improving the critical heat flux of the fuel assembly. The paired convex structures in the form of an access ramp effectively rectify the flow inside the grid structure, thereby reducing the pressure loss.

Description

SDecification Grid Structure With Flow Hybrid Coordination Function in Nuclear Fuel Assembly $

Teihuical Field

The present invention relates to a grid structure with a flow hybrid coordination function in a nuclear fuel assembly and belongs to the design of grid structure of fuel assemblies for pressurized water reactor nuclear power plant.

Jo Background Art

The common fuel assembly for pressurized water reactor nuclear power plant is composed of multiple fuel rods, guide tubes, spacer grids, upper and bottom tube seats and so on. As an important part of the skeleton, the spacer grid mainly functions to hold and locate the fuel rods first and then to mix the liquid to is increase the critical heat flux of the fuel assembly. The typical grid structure design is further provided with a hybrid system based on the clamping system in order to achieve the above two functions of the spacer grid.

According to thematic and patent document retrieval, the grid structures of Framatome AFA series are similar to the present invention, the grid structures of Framatome MA series are also provided with a clamping system and a hybrid system. The clamping system consisting of a three-arc spring and a bridge-shaped rigid convex structure is used for holding and positioning the fuel rods. The hybrid system consisting of tearing mixing wings commonly used in international scope. is used for mixing the i.uid. However, this design does riot consider the coordination between the clamping system and the hybrid system. The interference from the clamping system (threearc spring and hridgeshaped rigid convex structure) results in flow disturbance, and especially the upper rigid convex structure has serious interference effect on the mixing of the downstream hybrid system.. resulting in a weakened mixing performance of the grid structure.

Summary of the invention

The present invention aims to provide a grid structure with a flow hybrid 0 coordination function in a nuclear the! assembly to overcome the drawbacks and deficiencies of the prior art, The grid structure is of a rigid convex structure with a tishaped cross-section to form a passage for lateral flow at the two sides of the inner stripe an.d combine the flow to be mixed by the dowtstream mixing wing so that the mixing wing can more eflbctively guide the flow direction, amplify the hybrid function of the hybrid system and achieve the coordination of the clamping system and the hybrid system on the hybrid of flow, The object of the present invention is achieved by the following technical solution: a grid structure with a flow hybrid coordination function in a nuclear fuel assembly, comprising grids formed by vertically interlacing multiple inner stripes, wherein a pair of mixing wings are provided at the two sides of the top of the intersection of the inner stripes, and each inner stripe is concaved inwardly to form a rigid convex structure I with Ushaped cross-section, Of the rigid convex structure with a Ushaped crosssection, wherein the rigid, convex structure I and the rigid convex structure H are symmetrically arranged with the point of the imier stripe as the center to form the passage for lateral flow at the two sides of the inner stripe so that the mixing wing can more effectively guide the flow direction for the amplification of hybrid thnction of the hybrid system.

Further, the opening end of the rigid convex structure with a Ushaped crosssection I faces towards the bending direction o'f the corresponding mixing wing. The rigid convex structure I is of Ushaped crosssection. The coolant flows in the area formed by the inner stripes at its own rate arid, flows out of the opening end of the rigid convex structure I, wherein the opening end of the of a rigid convex structure with a Ushaped crosssection I faces towards the bending direction of the corresponding mixing wing so that the opening end can guide the coolant to flow into the bending direction of corresponding mixing wing. As a result, under the Junction of a plurality of rigid convex structures, a lateral flow passage is formed at the two sides of the inner stripes so that the mixing wing can more effectively guide the fl direction, amplify the hybrid function of the hybrid system and achieve the coordination of the clamping system and the hybrid.

system on the hybrid., of flow, Further, the inner stripes provided with the rigid convex structure I are concaved inwardly to form a rigid convex structure II; and the rigid convex structure H is of Ushaped crosssection; the opening direction and concave direction of the rigid convex structure H are respeclively opposite to the direction of the rigid convex structure I. Further, the rigid convex structure I and. the rigid convex structure II are arranged between the adjacent paralleled inner stripes.

Further, an end far away from the opening end of the rigid convex structure I is provided with a spring eye, the spring eye. is connected with the bottom of the rigid convex structure I, and the spring eye passes through the corresponding inner stripe. If the rigid convex structure 1 of Uh..aped crosssection with the opening upwards interferes with the spring assembly due to the limit of height of the inner stripes, openings can be arranged at the arc root of the rigid convex structure L Further, each pair of mixing wings are synimel.rically arranged with the intersection of corresponding inner stripes as the center.

In summary, the beneficial effects of the present invention are as follows: (1) The rigid convex structure with a Ushaped crosssed:ion achieves the 1 coordination between the clamping system and the hybrid system and enhances the mixing performance of the grid structure, thereby improving the critical heat flux of the Fuel assembly; (2) The inclined rigid convex structure with a Ushaped crosssection can effectively rectiI' the flow in the grid structure to reduce the pressure loss to some extent.

Brief Description of Drawings

Figure 1 is the schematic view of the present invention; Figure 2 is cooperation schematic view of the rigid convex structure with a U-shaped cross-section and the mixing wing; Figure 3 is the overall schematic view of the present invention.

Names of the parts labeled in the figures, 1 -rigid convex structure II; 2 -rigid convex structure!; 3 -inner stripe; 4-spring eye; 5-mixing wing.

$ Embodiments The present invention will be fbrther detailed in combination with the following embodiments and drawings, but the embodiments of the present invention are not limited thereto.

Embodiment to As shown in Figure 1, Figure 2 and Figure 3, a grid structure with a flow hybrid coordination function in a nuclear fuel assembly comprises grids formed by vertically interlacing multiple inner stripes 3, wherein a pair of mixing wings 5 are provided at the two sides of the top of the intersection of the inner stripes 3, and each inner stripe 3 is concaved inwardly to form a rigid convex structure with a U-shaped cross-section I 2, and the opening end of the rigid convex structure with a U-shaped cross-section I 2 faces towards the bending direction of the corresponding mixing wing 5. A U-shaped structure is formed on rigid convex stmctureof the inner stripe 3 in the bending direction of the mixing wing 5 at the top of the inner stripe 3 of the grid structure, wherein the upward opening of the U-shaped cross-section faces towards the bending direction of the mixing wing, and cross-direction mixing wings are formed at the intersection of the inner stripes 3.

The inner stripes provided with the rigid convex structure 12 are concaved inwardly to form a rigid convex structure II 1; and the rigid convex structure II I is of U-shaped cross-section; the opening direction and concave direction of the rigid convex structure II I are respectively opposite to that of the rigid convex S structure 12. The rigid convex structure 12 and the rigid convex structure if I are formed by stamping. During the stamping process, the structural features are guaranteed by a mold to succeed at the first attempt and avoid change of the internal structure due to application of force by multiple times. The inner stripe 3 is separately provided with the rigid convex structure 1 2, with its bottom arc surface provided with a spring eye 4.

The rigid convex structure 12 and the rigid convex structure II 1 are arranged between the adjacent paralleled inner stripes 3. In each unit grid composed of inner stripes 3, multiple unit grids constitute a grid structure, wherein the rigid convex structure 1 2 and the rigid convex structure II 1 are arranged on the inner stripes 3 of the unit grid.

An end far from the opening end of the rigid convex structure 12 is provided with a spring eye 4, and the spring eye 4 is connected with the bottom of the rigid convex structure I 2, and the spring eye 4 passes through the corresponding inner stripe 3. In order to avoid interference between the rigid convex structure I 2 and its corresponding spring at the time of assembly, a spring eye 4 should be arranged at the root of the rigid convex structure 12, wherein the spring is a single spring and is clamped in the rigid convex structure. According to the design -6'-parameters, the spring of different type of spring strength is selected.

Each pair of mixing wings 5 are symmetrically arranged with the intersection of corresponding inner stripes 3 as the center. The mixing wing 5 ftmctions in mixing the flow to improve the critical heat flux of the grid structure and fuel assembly.

The grid structure of the present invention is applicable to a variety of specifications, such as 12*12, 15* 15, 17*17, etc.. Such grid structure can improve the vortex factor (FSM) used for evaluation of the mixing performance of the grid stmcture, thereby improving vortex mixing ratio (SM) and enhancing io the mixing factor (FCM) of the lateral flow. The strength and operating distance of the vortex and lateral flow are larger than that of the existing grid structure.

Meanwhile, it improves the mixing uniformity used to evaluate the hybrid function and improves temperature uniformity. Further, mass mixing performance and heat mixing performance of the grid structure are improved to a certain extent.

is Taking the size of 17 * 7 grid for example, according to calculation, its improvement effects are as follows: In the 17 * 17 grid structure, compared with spacer grid of Framatome AFA3Q the spacer grid of the embodiments above improves the vortex factor (FSM) used to assess the mixing performance by 17.7%, the vortex mixing rate (SM) by 29% and the lateral flow mixing factor (FCM) by 20.82%. The strength and operating distance of the lateral flow and vortex flow are greater than that of AFA3G spacer grid. The mixing uniformity used to evaluate the mixing effect is improved by 15%, and the temperature unithnnity is improved by 292%. The mass mixing performance and heat mixing perfonnance of the grid structure are improved to a certain extent.

The 17 * 17 grid structure is provided with over 400 pices of mixing wings 5, s wherein the upstream coolant of about half of the mixing wings 5 are affected by the shape of rigid convex structure. in the ernbodimeiits, the opening end of the rigid convex structure with a U-shaped cross-section 1 2 faces towards the bending direction of the corresponding mixing wing 5, which can effectively decrease the adverse elect of upstream rigid convex structure shape on the o mixing wing S and guide more coolant to flow towards the mixing wing 5.

Compared with the grid structure of Framatome APA series, the matching arrangement of the rigid ccmvex structure 1 2 and the mixing wing 5 in the embodiments can dramatically improve the mixing performance of the spacer grid, thereby strengthening the mixing performance of th.e grid structure.

The grid structure adopts a rigid convex structure with a thshaped cross-section, which does not affect the positioning function of the original clamping system and has no additional requirements for the production process hut strengthens the mixing function of the grid structure and reduces pressure loss, thereby helping improve the thermal-hydraulic performance of the grid structure and. even the thel assembly.

The present invention can be well achieved in the embodiments above.