Waterproof treatment process of strain gauge on guide tube of underwater fuel assembly

Abstract

The invention discloses a waterproof treatment technology for a strainmeter on an underwater fuel assembly guide pipe. The waterproof treatment technology comprises the following steps: pasting the strainmeter on the guide pipe and preparing strainmeter lead solidus; clearing and washing the surface of the guide pipe adhered with the strainmeter; preparing polyurethane waterproof glue; preparing surface waterproof layers of the strainmeter and the lead on the guide pipe; performing waterproof treatment on a strainmeter lead tail circuit in a water through body; and ending the waterproof treatment technology for the strainmeter on the underwater fuel assembly guide pipe. The waterproof protection in a narrow space is realized, and the total thickness of the strainmeter and the lead is extremely thin. Compared with a current waterproof strainmeter, the waterproof layer is thinned by 1.5 mm. The prepared surface waterproof layers of the strainmeter and the lead on the guide pipe are greatly thinned. A problem that a water outlet of the water through body cannot be provided with a large hole is solved. A double-component polyurethanes adhesive is used for preparing the surface waterproof layers of the strainmeter and the lead on the guide pipe on site, a forming speed of the waterproof layers is rapid, a volume after the formation is small, and the cost is low.

Description

technical field [0001] The invention belongs to the technical field of underwater fuel assembly experiments, and in particular relates to a waterproof treatment process for strain gauges on guide pipes of underwater fuel assemblies. Background technique [0002] A set of fuel assemblies consists of hundreds of fuel rods with a length of 4 meters and an outer diameter of 9 mm, 24 control rod guide tubes with the same length and an outer diameter of 12.45 mm, a multi-layer structure mixing grid, a multi-layer inter-span mixing grid, Composed of components such as the upper tube base and the lower tube base, hundreds of fuel rods and control rod guide tubes are arranged according to a certain interval of 15×15 or 17×17, and are mixed with a multi-layer structure and inter-span mixing grid. Fix into a bundle to become a set of fuel assemblies. [0003] The fuel assembly works in the harsh environment of the reactor, and its service life is generally 2 to 3 years. The working p...

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Problems solved by technology

[0005] Due to the compact structure of the fuel assembly used in the test and the large number of fuel rods, the fuel rods are closely arranged, and the distance between the rods is narrow, with a distance of 1.8 mm; in addition, there are waterproof strain gauges abroad, but there is no domestic one that can meet the requirements. Therefore, most of them add a waterproof epoxy adhesive layer on the surface of the waterproof strain gauge, so that the strain gauge is completely encapsulated in the thick adhesive layer, so that its overall size reaches 15mm × 10mm × 2mm, which cannot meet the requirements in a narrow space. The underwater mechanical strain test of the fuel assembly cannot be realized by sticking it on the guide pipe of the fuel assembly. Therefore, the waterproof treatment of the strain gauge has become a difficult point in the high-speed flow hydraulic test of the fuel assembly.

[0006] If the above-mentioned existing waterproof strain gauge is used to paste on the real fuel assembly guide pipe with narrow space, the following problems that cannot be implemented will be produced:

[0007] First, the size of the waterproof strain gauge is too large. The thickness of the traditional waterproof strain gauge is 2 mm, which cannot be pasted on the guide tube. Its height exceeds the maximum gap of 1.8 mm between the guide tube and the fuel rod inside the fuel assembly;

[0008] Second, after pasting, the water flow field between the fuel assembly guide pipe and the fuel rod will be completely blocked, causing the water flow to the space where the waterproof strain gauge is pasted, and the water flow will be redirected, thereby changing the water flow field of the fuel assembly flow caused by the hydraulic test , causing the experimental test data to lose the significance of the research;

[0009] Third, the outer diameter of the strain gauge lead wire is relatively thick, and the wiring after the strain gauge is pasted will also change the water flow field of the hydraulic test caused by the flow of the fuel assembly

These three fatal shortcomings determine that the existing waterproof strain gauge cannot be applied to the strain test of the underwater fuel assembly mechanical test

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