JPS6154194B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a seal plug used in a pressure tube of a pressure tube nuclear reactor, for example.

The seal plug is attached to the open end of a pressure pipe loaded with a fuel assembly to form a pressure boundary for the primary coolant of the nuclear reactor, and its attachment and detachment are performed by remote control using a fuel exchanger. Furthermore, since the seal plug is exposed to an atmosphere of high temperature, high pressure, and high radiation during operation of a nuclear reactor, it is required to be easy to install and remove, and to have high sealing performance. In addition, the seal parts installed in seal plugs are regularly replaced parts, and after a certain period of use, they are removed from the seal plug and disposed of as radioactive contaminants within the nuclear power plant, but the amount of waste is The amount (volume) of the seal parts should be as small as possible to avoid increasing the
It is desired that

By the way, the general structure of a conventional seal plug is as shown in FIGS. 1 and 2.
In the figure, 1 is a pressure pipe, and 2 is a seal plug attached to the pressure pipe. The seal plug 2 includes a cylindrical seal plug body 21 and a seal plug body 21.
a latch mechanism 22 for coupling and holding the seal in a predetermined position within the pressure pipe 1, a seal element 23 attached to the tip of the seal plug body, and a dome-shaped top located at the forefront end and loosely fitted into the seal plug body 21. It comprises a plate 24 and an initial tightening spring 25 that urges the top plate 24 downward. Of these, the latch mechanism 22 is a latch ball 22.
1, an operating sleeve 222, a spring 223 for urging the sleeve 222 to the lock position, and an operating rod 224 for pushing up the top plate. The sealing element 23 is made of a metal made of titanium alloy, for example, from the viewpoint of heat resistance and radiation resistance, and its shape is formed by a thick base 231 that covers and is fixed to the front surface of the seal plug body 21, and its outer periphery. A series of thin lip portions 23 stand diagonally upward.
2. Since the operation of the latch mechanism 22 in the above configuration is well known, the explanation will be omitted, and the sealing operation will be described here. When installing the seal plug 2, the entire seal plug is grasped by a grab of a fuel exchanger (not shown), and an operating force is applied to the operating rod 224 to push up the top plate 24 against the spring 25 through the rod. Therefore sealing element 2
The seal plug 2 can be inserted into the pressure pipe 1 without sliding onto the inner wall of the pressure pipe 1 while the lip portion 232 of the seal plug 3 remains free. When the seal plug 2 is connected to the pressure pipe 1 at a predetermined position, the operating rod 224 is released, and the top plate 24 is biased by the spring 25 to push the lip portion 232 from the inner circumferential side to the inner wall of the pressure pipe 1 over the entire circumference. The lip part itself is bent and pressed so as to be in close contact with each other, thereby sealing between the circumferential surface of the top plate 24 and the lip part 232, and between the lip part 232 and the inner wall surface of the pressure tube 1. Due to this spring bias, the seal plug 2 forms a pressure boundary for the static pressure of the primary coolant in the pipes when the reactor is stopped. When the reactor enters operation, the pressure inside the pressure pipe increases, and a large pressure based on the pressure difference between the inside and outside is applied to the sealing element 23 via the top plate 24.
The pressure is applied to the lip portion 232 of the lip 232, and the pressure becomes even stronger due to its self-tensioning action. When removing the seal plug 2 for fuel exchange, the top plate 24 is pushed up via the operating rod 224 in the same way as when it was installed, the lip portion 232 is freed, and the entire seal plug is pulled out from the pressure pipe 1.

By the way, as mentioned above, when attaching and detaching the seal plug 2, it is necessary to push up the top plate 24 against the initial tightening spring 25 by remote control using the fuel exchanger. In this case, the initial tightening force is basically determined so as to apply a sealing force to the lip portion 232 of the sealing element corresponding to the internal pressure of the pressure pipe at the time of shutdown of the reactor, but especially when the sealing element is made of metal. Therefore, the force required to give a sufficient amount of radial deflection to the lip portion 232 must also be determined. Considering the seal element 23 of the conventional structure from this point of view, the lip portion 232
is integral with the thick base 231, and the base 2
31 is fixed to the seal plug main body 21 and rigidly supported. For this reason, the bending rigidity of the lip portion 232 is large, and the tightening force by the spring 25 required to bend the lip portion toward the outer periphery is large, and therefore the operating force required on the fuel exchanger side is also large. .
However, from the perspective of a fuel exchanger, it is preferable to be able to attach and detach the seal plug with a small amount of operating force in terms of operating capability. Furthermore, as described above, expensive titanium alloy is often used for the sealing element 23 due to material restrictions based on radiation resistance.
The conventional type that is integrated with the radioactive material is not only expensive to manufacture, but also economically disadvantageous due to the large amount of waste that is disposed of as radioactively contaminated waste after parts are replaced. .

The present invention has been made in consideration of the above points, and aims to provide an advantageous seal plug that can be produced and disposed of at a lower cost than conventional products, and can exhibit sufficient sealing performance with a small tightening force. purpose.

According to the present invention, the sealing element is integrally provided with a donut-shaped mounting base having a substantially circular cross section by connecting the sealing element to a thin ring-shaped lip, and the mounting base is loosely inserted into the outer circumferential groove at the tip of the seal plug body. This is achieved by having a seal ring that is fitted into the seal plug body, and in addition, the seal ring is not firmly fixed to the seal plug body, but is loosely and loosely held.

The present invention will be described in detail below based on illustrated embodiments.

3 and 4, the sealing element is constructed according to the invention as a metal sealing ring 23' made of, for example, a titanium alloy and having a small cross-section as shown. In addition, its shape includes a ring-shaped thin lip part 233 with a thickness of about 2 mm, and a lip part 233 with a thickness of about 2 mm.
33 and a donut-shaped mounting base 234 having a substantially circular cross section. Further, the seal ring 23' loosely fits its mounting base 234 into a notched groove 211 formed on the outer periphery of the tip of the seal plug body 21, and is attached to the plug body 21 through a set screw 212.
It is held in place by a retaining plate 213 fixed to the retainer. In this held state, the mounting base 234 of the seal ring 23' is not rigidly supported with respect to the seal plug body 21 so as to restrict its movement, but is held loosely so that it can freely slide within the groove. ing.

The other structure of the seal plug 2 equipped with the seal ring 23' and the operation for attaching and detaching it to the pressure pipe 1 are the same as those of the conventional seal plug 2 described above. That is, when the reactor operation is stopped immediately after installation, the lip portion 233 of the seal ring 23' is bent in the radial direction by the spring force of the initial tightening spring 25 via the top plate 24, and is pressed against the inner wall of the pressure pipe. Further, when the furnace is in operation, in addition to the above-mentioned spring force, a large internal pressure of the pressure pipe 1 acts through the top plate 24.
The lip portion 233 is pressed more strongly to form a reliable pressure boundary.

By the way, in the conventional seal element, the lip part 232 of the seal element is rigidly supported by the seal plug body 21 via the thick base part 231, so the bending rigidity of the lip part is large, and the necessary radial deflection is However, according to the present invention, as in the embodiment, the sealing element is formed as a seal ring 23' having a small cross-section. , and by holding the mounting base 234 in the seal plug main body 21 with a loose fit, the mounting base 234 is not restrained even when bending the lip portion 233 and remains in the notch groove 211 of the seal plug main body 21. Can be tilted freely. As a result, the bending rigidity of the lip portion 233 is reduced, and a sufficient amount of deflection can be applied to the lip portion with a smaller tightening force than in the past, thereby achieving high sealing performance. This is advantageous in terms of equipment since the operating capacity of the fuel exchanger is small. Furthermore, the seal ring is extremely small compared to the overall size of the conventional sealing element, and even if expensive titanium alloy is used, manufacturing costs can be sufficiently reduced, and even when the sealing element is replaced and disposed of, the amount of waste generated can be reduced. This provides an economical advantage in the disposal of radioactive contaminants in nuclear reactor plants.

As described above, the present invention can be used as a sealing plug for pressure pipes in various devices in the nuclear power field, such as pressure tube nuclear reactors, and is practical in terms of manufacturing cost, ease of attachment/detachment, sealing function, parts replacement, and disposal. We can provide high value seal plugs.

[Brief explanation of the drawing]

FIGS. 1 and 2 are a cross-sectional view of a conventional seal plug and an enlarged cross-sectional view of the main parts, and FIGS. 3 and 4 are a cross-sectional view of the structure and an enlarged cross-sectional view of the main parts of an embodiment of the present invention, respectively. be. 1...Pressure pipe, 2...Seal plug, 21...
Seal plug body, 211...Tip outer peripheral notch groove of seal plug body, 22...Latch mechanism, 23'
... Seal ring, 233 ... Lip part, 234
...Mounting base, 24...Top plate, 25...
...Biasing spring.

Claims (1)

[Claims] 1. A seal plug body that is inserted into the pressure pipe from the open end, a latch mechanism that connects and holds the seal plug body to the pressure pipe, a metal sealing element attached to the tip of the seal plug body, and a spring biasing force or pressure pipe. A sealing plug for a pressure pipe, comprising a top plate that presses the sealing element tightly against the inner wall of the pressure pipe over the entire circumference by pressure inside the pipe, the sealing element being adapted to substantially fit the inner diameter of the pressure pipe. , a seal ring which is integrally provided with a donut-shaped mounting base having a substantially circular cross section connected to a thin ring-shaped lip part, and the mounting base is loosely fitted into the outer circumferential groove at the tip of the seal plug body. A pressure pipe characterized in that the seal ring is loosely fitted into the seal plug body so as not to restrict the deflection of the seal ring when the seal ring is pressed onto the pressure pipe via the top plate. seal plug.