KR800000095B1 - Modular in-core flow filter for a nuclear reactor - Google Patents

Abstract

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Description

Modular core coolant filtration system for nuclear reactor

1 is a cross-sectional view of a reactor in which the present invention filtration apparatus is installed on a lower core plate.

2 is a perspective view of the upper part of the present invention filtration apparatus

3 is a perspective view of the bottom of the invention invention filter

4 is a partial perspective view of the lower core plate of the reactor.

TECHNICAL FIELD The present invention relates to a reactor, and more particularly, to a filtration device used to remove debris from a reactor and a primary coolant recycle loop during functional tests of cooling hydrostatic and high temperature conditions.

These debris, in the form of metal chips and chipping debris, small solid metal debris, etc., are residues from the manufacturing, assembly, and mounting of the reactor and its accessories. Although a sophisticated process for removing these residues is carried out, experience has shown that even when safety devices are used to remove these residues, small amounts of chips and metal particles still remain somewhere in the apparatus.

Several methods have been used to remove these residues. In small reactors, a screen assembly with adequate strength and characteristics is installed at the coolant inlet at the reactor core. As the coolant circulates during the reactor test, these foreign substances inside the reactor system are captured on the screen and removed after the test is completed. Although such a single screen assembly is effective for small reactors, in the case of large reactors, the constant flow pressure applied to the screen is so great that it cannot be used because part fragments of the screen will flow with the coolant in the reactor system. Alternatively, no screen is used because the geometry of the steam generator and the bottom of the reactor vessel acts as a vessel to trap these particles. However, small particles in the reactor system can cause operational disturbances if they are sandwiched between control rods and guide tubes or between moving parts and moving parts of the pump.

Accordingly, it is a primary object of the present invention to provide such a filtering means that captures debris remaining in the apparatus after assembly and installation of a large reactor and its accessories and is not ruptured by the coolant flow pressure during reactor operation.

The present invention relates to a reactor vessel in which a reactor vessel lid is secured in a fluid sealed manner, a coolant inlet and an outlet in the reactor vessel through which coolant passes, upper and lower core plates supported in the reactor vessel and having a coolant distribution hole, and Apparatus for removing harmful debris during a preliminary test from a reactor with an upper support plate installed adjacent to the top of the reactor vessel, the filter assembly having a filter element therein, the fuel assembly being disposed on the lower core plate and spaced apart from each other Dowel pins are installed in the lower core plate, and at least one dowel pin hole is formed in each filter assembly so that the filter assemblies are correctly placed on the lower core plate, and each filter assembly separates each filter assembly on the lower core plate. Cooperative with the lower core plate to possibly place Having a stage, the means designed to remove each filter assembly at the end of the preliminary test, and the filter elements so as to effectively capture the metal pieces and cutting pieces remaining in the reactor vessel and the primary cold system during assembly. It provides a modulus core core coolant filtration device for a reactor, characterized in that.

Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

In FIG. 1, a schematic of a reactor composed of a reactor vessel 10 with a reactor vessel lid 12 fluidly mounted by bolts 14 is shown.

The core 16, which is extended from the ledge 18 and supported by the upper support plate 20, is spaced apart from the reactor vessel wall to form an annular space 22 extending through the entire length of the reactor vessel. The lower core plate 24 and the upper core plate 26 are fixed to the cores and contain fuel assemblies (not shown) in the area 28 formed between the upper and lower plates of the core, and the fuel assemblies are arranged in operation and constitute the core of the reactor. do. A support adapter 30 is provided in the space between the upper support plate 20 and the core lower plate 26, and the control rod guide tube 32 surrounds the control rod 34 reciprocally driven in the fuel assembly by the control rod drive mechanism 36. At the bottom of the reactor is a lower support plate 38 with an opening 40. The coolant enters the reactor through the inlet nozzle 42 and flows through the annular space 22 to the bottom of the reactor vessel 10. Then, the flow direction is reversed and flows upward through the opening 40, the lower core plate 24 and the fuel assembly, and is discharged to the primary loop through the outlet nozzle 44. The primary loop typically consists of a pump and steamer (not shown). The above-described structure is well known, and it is described here to help understand the present invention.

As described above, modulus in-core coolant filtration is used to capture debris and prevent the debris from circulating through the reactor primary rope during cooling fluid static and high temperature functional testing of the reactor. Such tests are carried out before the fuel assembly is charged into the reactor.

The lower core plate 24 covers the entire area of the lower surface of the fuel assembly, and a plurality of holes are provided in the lower core plate, through which the coolant flows upward to exchange heat with the fuel rod of the fuel assembly in the reactor.

4 is a partial ablation perspective view of the lower core plate 24, the size of which is substantially the same as the size of the fuel assembly. As shown, a conventional dowel pin 46 is in a position to receive a fuel assembly, and four openings 48 are present below the fuel assembly through which the coolant flows upwardly in contact with the fuel assembly. Take away the heat generated.

Each filtration device of the type shown in FIGS. 2 and 3 is four squares about 8 inches (about 20.3 cm) square and about 2.5 inches (about 6.35 cm) high, which is the height of the top surface of several bolts, nuts and lower core plates. It is the height required to accommodate instrument guides that protrude above. Each filtration device has the same area as the planar area of the fuel assembly and also has axial holes 52, into which two pins 46 on the lower core plate are inserted.

This arrangement allows for precise orientation when the filtration device is installed. The filtering device has an axial opening 54 (FIG. 3) and has a flange 56 disposed adjacent its upper surface. A filter with a wire screen 58 made of a 300 series stainless steel square mesh is placed on the flange 56 and provides a mechanical support of the filter screen 58 and a back screen 60 made of the same material as the filter screen 58. It is provided in the opening 54 in contact with the filter screen 58. The mesh width of the filter screen 58 is 0.0603 inches (about 0.15 cm) and the wire diameter is 0.023 inches (about 0.058 cm), allowing 52% of the coolant flow to pass, making it suitable for testing purposes. Rear screen 60 has a mesh width of 0.375 inches (about 0.95 cm) and a wire diameter of 0.080 inches (about 0.203 cm). As shown, the screens are mounted on the upper surface of the filtration device and are firmly coupled to the flange by support rings 62, which are joined to the base 50.

A circular disk 64 bonded to the bottom of steel rod 66 to engage the upper surface of the rear screen 60 to provide support to the center of the filter and acts to restrict the screen from bending in the direction of coolant flow. Rod 66 is bonded to the upper surface, marked 68 at the filter base 50. In order to position the filter window on the lower core plate, a radial groove 70 is formed at the base of the filtering device, and a metal block 72 is provided in the groove.

A shaft 74 with threaded grooves 76 extends downwardly through holes 78 formed in the metal base and protrudes beyond the lower surface of the metal base. The lugs 80 bonded to the ends of the shaft 74 protruding below the lower surface of the filtration device are of sufficient size to rotate over the corresponding parts of the lower core plate to secure the filtration device to a designated position on the lower core plate. have. Dowel pins 82 inserted in the shaft prevent the shaft from falling out of the filtering device. Furthermore, slot 84 installed in each metal base is sized to accommodate dowel pins 82. This dowel pin has another function of aligning the knitted lugs on the bottom of the lower core plate and the bottom of the shaft.

In isolation of the filtration system, the screen and retaining ring 62 are held in place, the steel bar 66 is joined to the upper surface of the base 50, the metal block 70 is inserted into the recess 72, and the shaft 74 is filtered with this block. Insert into opening 78 at the base of the device. When these parts are in place, the shaft 74 is rotated to position the knitting lugs 80 under the lower core plate, where the alignment plate 82 is aligned with the slot 84 formed in block 72 and inserted into the slot. . Next, the fixing tab 86 and the nut 88 are rotated around the shaft 74 to pull the knitting lugs 80 under the lower core plate to fix the filtration device firmly to the lower core plate 24.

Since each filter occupies only four holes formed on the lower core plate, it can be seen that one filter device is provided in four holes to form a complete filter device in the cooling fluid energetic and high temperature operation test. When one or more human aisle covers are installed on the lower core plate to allow access to the lower part of the reactor vessel, a slightly modified filtration device should be used, in which the thickness of the core plate in the human passage holes is greater than the thickness of the core plate itself. For this reason, you can lengthen the axis.

If more coolant flow is required than normal, the screen may be conical or parabolic. Filters of this structure provide a larger flow area to handle larger amounts of coolant circulated during reactor testing.

Figures 2 and 3 show the top and bottom of only one of the filters designed to be placed on the lower core plate for filtration purposes, respectively, but the same area occupied by the fuel assembly when multiple filters are used and the fuel assembly is loaded into the reactor. It can be seen that the area occupies each filtration device.

The filtration device is installed on the lower core plate prior to the hydrostatic test and is separated from the core bottom plate after the hot operation test without removing or dismantling any parts of the lower part of the reactor. It is desirable to be able to capture all particles larger than 1/16 inch (about 1.6 mm) in diameter and to withstand the forces exerted on the filter element by the coolant flowing through the reactor at high pressure and high speed.

The structure must be strong enough to withstand the impact of objects as large as 1 / 4-1 / 2 inches (about 6.4 mm to 12.7 mm). However, the total flow pressure drop caused by the multiple screen assembly should be less than the pressure drop by the core. In order to achieve economical operation, it is important to make the filtration device portable and reusable from one plant to another.

Claims (1)

A reactor vessel with a reactor vessel lid secured in a fluid-tight manner, a coolant inlet and outlet in the reactor vessel through which coolant passes, upper and lower core plates supported in the reactor vessel and having a coolant outlet and adjacent to the top of the reactor vessel. A device for removing harmful debris during a preliminary test from a reactor with an upper support plate installed therein, the fuel assembly dosing pin having a filter element therein disposed on the lower core plate and spaced apart from the fuel assembly dosing pins. Installed in the core plate, at least one dowel pin hole is formed in each filter assembly such that the filter assemblies are placed on the lower core plate, and each filter assembly is detachably disposed on the lower core plate to allow for separation of each filter assembly on the lower core plate. Has a means of co-operation with judgment, Means for removing each filter assembly at the end of the preliminary test, and the filter elements being capable of effectively capturing metal pieces and cutting pieces remaining in the reactor vessel and primary cooling system during assembly. Modulus core coolant filtration system.

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