JPH0475477B2 - - Google Patents

Description

BACKGROUND OF THE INVENTION Description of Related Patent Applications The United States patent application for this invention is a continuation-in-part of co-pending United States Patent Application No. 356,903, filed March 10, 1982. This prior application is incorporated by reference into this application and is made a part of this application.

FIELD OF THE INVENTION The present invention relates to nuclear reactor pressure vessel servicing tools, and more particularly to tools that enable the closure of fluid outlets normally submerged within a nuclear reactor pressure vessel. During refueling and maintenance outages of water-cooled nuclear reactors, there is a need to facilitate isolation and drainage of recirculation suction piping without draining the reactor vessel. In the past, recirculation intake piping maintenance and repair operations often required draining the reactor vessel to a level below the level of the recirculation outlet nozzle on the side of the reactor vessel. Because the outlet nozzle is generally located at some height below the radioactive core, the cooling fluid can only be removed after the entire core has been unloaded. This method is undesirable. This is because it is expensive, requires processing and storage of radioactive materials, and is time consuming.

Description of the Prior Art Traditionally, the outlet piping adjacent to the outlet nozzle of a recirculation circuit has been provided with a valve. However, such valves require periodic maintenance that cannot be performed while the valve is in use. Additionally, such valves have also been known to leak fluid if not maintained.

To date, the submersible inlet of the first valve has been unable to operate due to relatively high pressures and narrow sidewall tolerances at extreme depths within the reactor vessel, as well as irregularities in the nozzle throat that are believed to impede reliable sealing and occlusion. It was generally impractical to provide means for closing off.
One strategy used by the General Electric Company for steam lines in the reactor vessel was to insert a rigid tube as a plug deep into the steam line through a nozzle, and to connect the inserted tube and the line. and providing an inflatable toroidal gasket that is expandable to engage opposing surfaces of the gasket. The gasket was shaped to resemble a generally flat ribbon to accommodate pressure differentials that tend to shear the seal along the length of the steam line. As a result, the insertion tube had to be relatively long to accommodate the length of the seal. Even then, this structure could not withstand high shear pressures and special tooling was required to fit the device in place. Such a structure is unsuitable for the relatively small spatial tolerances and relatively high pressures near the recirculation nozzle located relatively deep within the reactor vessel.

Another strategy for remote, deep, high pressure sealing applications has been the use of gasket seals in the sidewalls around the nozzle. (1982 of Tokyo Shibaura Electric Co., Ltd.
(See the prior art described in Utility Model Application Publication No. 1983-47756 dated October 20, 2013). Although this strategy makes it possible to use fluid pressure within the container to reinforce the seal, there is often inadequate room for such a seal, or the shape of the container wall is often very irregular, so This seal is not suitable for general use. What is needed is a plug that is compact, reliable, and easily deployable deep within the reactor vessel.

SUMMARY OF THE INVENTION According to the present invention, a device is provided for occluding an outlet nozzle connected to a cooling fluid recirculation circuit deep within the reactor pressure vessel in order to isolate the cooling fluid recirculation circuit from the nuclear reactor. . This device consists of a plug having a right cylindrical male surface that engages with the nozzle bore of the outlet nozzle, a flange provided around the plug to support the plug, and a flange that seals the plug in the nozzle bore when the plug is inserted into the outlet nozzle. an inflatable gasket means attached to the male face of the plug, a means for remotely pressing and holding the plug in contact with the nozzle bore, and a means attached to the plug for remotely controlling the plug to face the nozzle. the flange has a surface that engages a wall of the pressure vessel to support static pressure of liquid on the plug when the plug is inserted into the outlet nozzle; The means for pressing and holding by remote control is a jacking means attached to the plug, and the jacking means is a structure in the pressure vessel facing the nozzle bore. The remote positioning means having abutting end pads includes two cables attached to different points on the plug, from which the plug is suspended and positioned adjacent the nozzle bore. In a particular embodiment, the gasket device comprises two textile reinforced O-rings;
Each O-ring is remotely inflatable and the pushing device is a compact hydraulic jack having an end pad that abuts a surface of structure in the reactor pressure vessel opposite the nozzle. The cylindrical plug has a diameter and shape (circular in section) with a small tolerance to the diameter and shape of the recirculation circuit. The device can be collapsed into a narrow space so that the device can be lowered into the cooling fluid and deployed within a relatively narrow space area adjacent to the nozzle. A cable is provided for suspending the device, and a fluid-filled control line is connected to the device to perform the functions of gasket inflation and jack extension. The device can withstand relatively high shear pressures because most of the static pressure of the fluid acts on the flange and only a small amount of the static pressure acts on the plug.

The invention will be better understood from the following detailed description taken in conjunction with the accompanying drawings.

DESCRIPTION OF SPECIFIC EMBODIMENTS FIG. 1 shows a typical boiling water nuclear reactor 10 in which the apparatus according to the invention may be used. Boiling water reactor 10
includes a pressure vessel 12 having a vessel head 14, which is shown in the figure in an open position for servicing. The container 12 is a steam outlet pipe 16
, a water supply inlet pipe 18 , and a recirculation circuit 20 . The nuclear fuel is stored in the steam separation device 2 in the shroud 28.
4 and in the core 22 below the steam drying device 26. The cooling fluid flows between the shroud 28 and the vessel wall 32.
Furnace shroud 2 at a radial position between
8 and flows in an annular manner around the core shroud.

Recirculation circuit 20 includes an outlet nozzle 34 connected to an outlet tube 36 , which is connected to a first valve 38 . The outlet of the first valve 38 is connected to a recirculation pump 40 , which is connected to a second valve 42 , which is connected to an inlet tube 44 , which is connected to an inlet nozzle 46 . . Inlet nozzle 46 is connected to a jet pump nozzle assembly 48 which forms part of jet pump assembly 30. According to the invention, the plug assembly 5
A device in the form of 0 is provided and the plug assembly can be lowered into the reactor vessel 12 and positioned to seal the recirculation circuit outlet nozzle 34.

2, 3, and 4 in conjunction with FIG. 1, the plug assembly 50 is shown in its collapsed position (FIG. 2), in which the plug assembly 50 is shallowly , and can be inserted deeply into the container and assume the deployed position (Figures 1, 3, 4). The plug assembly 50 includes two cables 52,
54, it is suspended from a high position via the open container 12. Plug assembly 50 may be completely removed from reactor vessel 12 when not needed.

Referring to FIGS. 2, 3, and 4, plug assembly 50 includes a plug member 56 formed as a right cylinder that is generally connected to a cylindrical interior wall or nozzle bore 60 downstream of nozzle 34 within conduit 36. Has a matching tapered outer or male surface. Plug assembly 50 also has one end attached to plug member 56 and the other end attached to jack pad 6.
4 and a hydraulic piston 66 for bending and extending the jack 62. Hydraulic piston 66 is typically a two-way retractable device with one end pivotally mounted within a cavity behind plug member 56 and the other end pivotally mounted on an arm of a scissor-shaped assembly comprising jack 62. good.
A flange 71 extends transversely to the central axis of the plug member 56, and the two flanges are connected to the nozzle 3.
It has surfaces 73, 75 for engaging the inner surface of the container wall 32 adjacent to the container wall 32. Surfaces 73, 75 support the main hydrostatic pressure of submersible plug assembly 50 when installed within nozzle 34. The folded plug assembly 50 is manipulated by two cables 52, 54 and can be positioned facing the nozzle 34 in the confined space between the vessel wall 32 and the jet pump assembly 30. In the extended position, the plug assembly 5
The zero plug member 56 is inserted through the nozzle 34 along the inner wall defining the bore 60 and is held in place by a jack pad 64 pressing against the core shroud 28 and a flange 71. The scissor-shaped part of the jack 62 is the jet pump assembly 30.
They are narrow enough to easily pass through narrow spaces between each other, and the jack pads 64 are also narrow enough to fit into the spaces between adjacent jet pump assemblies 30.

Nozzle bore 60 of nozzle 34 generally has a surface of unknown roughness. This surface may become irregular due to corrosion, for example. Means must be provided to provide a positive seal between the bore 60 and the face 58 of the plug member 56. To this end, the diameter and shape of the circumferential outer surface 58 of the plug member 56 is selected to provide a substantially tight fit with the inner wall along the bore 60. A 1/4 inch gap at any point is
Considered maximum for a design pressure differential of 70psi.
A gasket arrangement consisting of first and second inflatable O-rings, 72, 74, reinforced with fabric is provided around the face 58 along the clearance opposite the inner wall along the bore 60. O-rings 72, 74 are oval in shape and fit within narrow recesses in cylindrical surface 58. Both O-rings are made of a suitable commercially available textile reinforced elastomer, such as Prespray type.
Constructed from a PRS701 airtight O-ring, it is hollow for expansion and highly conformable to fit the abutment surface of the bore 60. More specifically, the O-rings 72, 74 are remotely inflatable by pneumatic lines in the controlled tube furnace 78. In the folded and uninflated state (Fig. 2), O
Rings 72, 74 are retained within parallel grooves in face 58 of plug portion 56. In the expanded state (FIG. 3), O-rings 72, 74 expand and form a seal against bore 60. Two rings face 5
8 ensures proper sealing in the case of irregularities such as seams or cavities in the bore 60.

Plug assembly 50 may be remotely controlled by a hydraulic control panel 76 (FIG. 2) external to reactor vessel 12. The control panel 76 is connected to a hydraulic pressure line of a control line 78, and the pressure of the compressed fluid is transmitted through this line to cause the O-rings 72 and 74 to expand and contract and the jack 6 to be adjusted.
2 expansion and contraction.

In hydraulic systems, the working fluid is preferably deionized water, although other working fluids may be used. A hydraulic pump driven by air is the power source for the hydraulic system. This may be housed in a control panel 76 to which the air pressure source is attached.

In use, the plug assembly 50 is lowered into a position opposite the nozzle 34 and the jack 62 is extended to compress the plug member 56 and open the bore 6.
O-rings 72, 74 are then expanded to seal bore 60. Thereafter, the fluid in the recirculation circuit 20 is transferred from the outlet tube 36 (FIG. 1) associated with the outlet nozzle 34, for example to the outlet tube 3.
6 can be removed from outlet 34 and drained. As fluid exits the recirculation circuit, the static pressure of the fluid within the reactor vessel 12 helps to hold the plug member 56 in place relative to the bore 60, thereby ensuring a positive seal. The first valve 38 may then be removed and adjusted in the recirculation circuit 20 without losing fluid within the reactor vessel.

Although specific embodiments of the invention have been described above, it will be appreciated that various modifications may be made within the scope of the invention.

[Brief explanation of the drawing]

1 is a cross-sectional side view of the reactor vessel; FIG. 2 is a partially sectional side view showing the device according to the invention in the folded position; and FIG. 3 is the device according to the invention in the extended position against the seat of the nozzle. FIG. 4 is a perspective view of the device according to the invention. Description of main symbols, 20...Cooling fluid recirculation circuit, 34...Outlet nozzle, 36...Outlet pipe, 50
...Plug assembly, 52, 54 ...Cable, 5
6... Plug member, 60... Nozzle bore, 62...
...Scissors-shaped jack, 64...Jacket pad,
66... Hydraulic piston, 71... Flange, 7
2, 74...O ring, 78...control conduit.

Claims (1)

Claims: 1. In a cooling fluid-filled reactor pressure vessel comprising an outlet nozzle connected to an outlet pipe of the cooling fluid recirculation circuit and having a nozzle bore adjacent thereto, for isolating said cooling fluid recirculation circuit. A device for closing the nozzle, the device comprising: a shallow plug having a right cylindrical male surface that engages the nozzle bore with a small tolerance; and a flange around the plug for supporting the plug from within the container. , mounted on the face for sealing the plug against the bore when the plug is inserted into the nozzle so that the face is juxtaposed with the bore, surrounding the periphery of the face and attached to the nozzle seating surface; an inflatable gasket means having a hollow elastomeric O-ring sealing means sufficiently compliant to form a seal against irregularities; and means for remotely pressing and retaining said plug against said nozzle bore; means attached to said plug for remotely positioning said plug facing said nozzle, said flange having a surface for engaging an inner surface of said container wall proximate said nozzle; supporting the static pressure of the reactor pressure vessel fluid on the submersible plug when installed in the submersible plug, said flange further having a beveled portion to enable said flange to extend into said nozzle, and said remote control The means for pressing and holding by the plug is a jacking means attached to the plug, the jacking means having an end pad that abuts a structure in the reactor pressure vessel facing the nozzle seating surface, The remote positioning means includes first and second cables attached to different locations on the plug for suspending the plug and positioning the plug face adjacent the nozzle seat. I made it seem like
Outlet nozzle closure device. 2. The gasket means comprises a first hollow elastomeric O-ring and a second hollow elastomeric O-ring, the first and second O-rings surrounding the face and sealing against irregularities in the nozzle seating surface. 2. A device according to claim 1, which is fully flexible. 3. Apparatus according to claim 1 or claim 2, wherein said gasket means is inflatable by remote control to provide a conformable seal between said face and said seating surface. 4. A device according to claim 1 or 2, wherein said plug is a right cylinder having a groove for retaining said gasket means. 5. The device of claim 1, wherein the jacking means comprises a scissor-shaped telescoping body and a hydraulically actuated piston. 6. The device of claim 5, wherein the actuating piston is extendable and retractable by remote actuation in response to a hydraulic signal.