JPS6333674B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is a fuel rod, a poison tube, or the like that is housed in a nuclear reactant container, and after these are loaded into a reactor core, the seal is opened and the tag gas sealed inside is released into the nuclear reactant container. The present invention relates to a tag gas enclosure that releases gas to

In general, nuclear reactor fuel rods, poison tubes, and the like are configured to contain and seal reactants such as nuclear fuel and neutron absorbers in cladding tubes to prevent radioactive materials such as fission products from leaking outside. In addition, in the event that the cladding is damaged during reactor operation, the amount of radioactive materials in the coolant or cover gas is monitored to detect the damage early, and the amount of radioactive materials in the coolant or cover gas is monitored and leaked due to damage to the cladding. The facility is equipped with equipment that detects radioactive materials and detects their damage. Furthermore, when such a cladding tube breakage occurs, a device is provided to identify which fuel rod's cladding tube out of the many loaded fuel rods has been damaged.
For example, in liquid metal-cooled fast breeder reactors that use liquid sodium as a coolant, etc., a tag gas, which has a different composition for each fuel assembly, is sealed in the cladding of the fuel rods, which prevents damage to the cladding. When a leak occurs, the leaked tag gas is analyzed to determine its composition, and from this composition it is possible to detect in which fuel assembly the cladding has broken, making it easier to replace the fuel assembly. It is composed of By the way, when manufacturing fuel rods and poison tubes, it is necessary to fill them with tag gases of different compositions, which is cumbersome to manufacture and manage, and in the unlikely event that a leak occurs in the cladding tube during manufacture. In such cases, there is a possibility that tag gas leaks before loading into the reactor core, and in such cases, even if a break in the cladding is detected after the reactor is operating, it is not possible to identify which fuel assembly it is. There was a problem where it was not possible to identify the item. In order to prevent such problems, tag gas enclosures are manufactured in advance that are equipped with tag gas enclosures filled with tag gases of various compositions and an opening mechanism that unseals the tag gas enclosures by heating them to a predetermined temperature. A system was developed in which these were stored in the plenum of the fuel rod or poison tube cladding tube, and when the reactor started operating, these tag gas enclosures were opened and the tag gas was released into the cladding tube. has been done. Since tag gas of this kind is released into the cladding tube only after the reactor is operated, it is easy to manufacture fuel rods and poison tubes, and it is also easy to manage them until they are loaded into the reactor core. Become. Conventionally, such a tag gas enclosure has been constructed as shown in FIGS. 1 and 2. Namely, numeral 1 denotes a tag gas enclosure, which is made of stainless steel and has a cylindrical shape, and both ends thereof are closed with end plugs 2 and 3. A thin film portion 8 having a thickness in the range of 0.05 to 0.5 mm is formed on one end plug 2. Further, a sealing tube 4 is protruded from the other end plug 3, and the tag gas is sealed in the tag gas sealing container 1 at a predetermined pressure through the sealing tube 4, and after filling, the sealing tube 4 is airtight. It has been sealed and cut. Further, a cylindrical opening mechanism case 5 is concentrically attached to one end of the tag gas sealed container 1, and an opening mechanism 6 is provided inside the case 5. Reference numeral 7 denotes an unsealing member, which is slidably fitted into the unsealing mechanism case 12. A piercing portion 9 is provided protruding from the center of the unsealing member 7 so as to face the thin film portion 8 of the tag gas filled container 1 .
This piercing portion 9 has a hollow tubular shape, and its tip portion is cut along a cutting surface oblique to the central axis, and is sharply formed, and pierces the thin film portion 8. It is configured to penetrate. A hollow end plug 10 is attached to the end of the opening mechanism case 5. and,
The piercing portion 9 and the unsealing member 7 described above are configured to be moved by a drive mechanism 12 consisting of a large number of bimetal plates 11 . These bimetal plates 11 are made by laminating a low expansion coefficient metal plate and a high expansion coefficient metal plate, each having a disk shape or a plate shape, and the high expansion coefficient side and the low expansion coefficient side are arranged alternately. Many objects are stacked one on top of the other so that they face each other. And as the temperature rises, the second
As shown in the figure, these bimetal plates 11 are bent, and as a result, the unsealing member 7 and the piercing part 9 are pressed toward the thin film part 18, and the piercing part 9 penetrates the thin film part 8, and the tag gas inside the tag gas enclosure container 1 is pushed. is configured to discharge into the cladding tube. However, such a device has a complicated structure, and there are many welding points between the tag gas filled container 1, the end plugs 2, 3, the opening mechanism case 5, and the end plugs 2, 10, making it difficult to manufacture and not suitable for mass production. There was an undesirable problem. Furthermore, when such a tag gas enclosure is housed in the plenum, after opening, the effective volume of the plenum decreases by the volume of the parts that make up the tag gas enclosure. 3,1
Since the volume of the 0 etc. was large, there were problems such as a large reduction in the effective volume of the plenum section.

The present invention has been made based on the above circumstances, and aims to be simple in structure, easy to manufacture, suitable for mass production, have small volume of constituent parts, and be suitable for fuel rods and poison tubes. An object of the present invention is to obtain a tag gas enclosure that can reduce the reduction in effective volume of a plenum part.

The present invention will be explained below with reference to an embodiment shown in FIGS. 3 to 6. In the figure, 101 is, for example, a fuel rod, and 102 is its cladding tube. The cladding tube 2 is filled with fuel pellets 103 containing fissile materials such as uranium 235 and plutonium 239. In addition, this cladding tube 1
An upper end plug 104 and a lower end plug 105 are hermetically welded to the upper and lower sides of 02 to form a completely airtight structure, which prevents radioactive materials such as fission products produced by nuclear reactions or fission of nuclear fuel materials from leaking outside. It is configured not to. In addition, this cladding tube 1
In the upper part of 02, there is a space part, that is, a plenum part 10.
6 is formed, and gaseous fission products are configured to collect within this plenum section 106. A spring 107 is also provided in this plenum portion 106.
is provided, and the fuel pellets 103 are pressed and fixed by this spring 107. moreover,
This plenum part 106 has a tag gas enclosure 108.
is accommodated. This tag gas enclosure 108 is constructed as shown in FIG. That is, 109 is the container body, for example
It is composed of a thin-walled tube made of stainless steel such as SUS316 or SUS304 with an outer diameter of 4 mm to 10 mm and a wall thickness of about 0.1 mm to 0.2 mm. And this container body 1
09 is closed by a closing member 110. This closing member 110 is SUS316,
It is press-molded from a thin plate of stainless steel such as SUS304 with a thickness of 0.1 mm to 0.2 mm, and has a cylindrical shape with a bottom. This closing member 110 is connected to the container body 10.
The edge of the closing member 110 and the edge of the container body 109 are hermetically welded together. Further, a thin film portion 111 having a thickness of 0.05 mm to 0.15 mm is formed on the bottom wall portion of the closing member 110. Further, the other end of the container body 109 is reduced in diameter to an outer diameter of approximately 1 mm to 3 mm by drawing or the like to form an enclosure tube portion 112. A tag gas, which is a mixture of one or more of rare gases such as argon, xenon, and neon, is sealed at a predetermined pressure into the container body 109 via this sealing tube section 112.
The tip is cut and sealed. An opening mechanism 113 is provided within the container body 109. Reference numeral 114 denotes an unsealing member thereof, and this unsealing member 114 is provided within the container body 109 so as to be movable in the axial direction thereof. And this unsealing member 1
14 has a protruding portion 115 protruding from the inner surface of the thin film portion 111 of the closing member 110. This piercing portion 115 has a hollow tubular shape, and its tip is cut diagonally to form a sharp point. Also,
Three protrusions 116 arranged in the circumferential direction are formed on the inner peripheral surface of the container body 109. These protrusions 116 are formed by recessing a part of the peripheral wall of the container body 109 inward, and the protruding height of the inner surface thereof is 0.2 mm to 2.0 mm. And this protrusion 1
16... and the unsealing member 114, a drive mechanism 117 is provided. This drive mechanism 117 is made up of a large number of disc-shaped bimetal plates 118 stacked one on top of the other so that their high-expansion side surfaces and low-expansion side surfaces face each other. Projection 116... and unsealing member 1
14, respectively.

In one embodiment of the present invention configured as described above, a fuel rod 101 containing this tag gas enclosure 108 is provided.
When loaded into the reactor core, the bimetal plates 118 are heated by the heat of preheated coolant such as liquid sodium or by the heat of the nuclear reaction at the start of operation of the reactor, and are bent as shown in Fig. 6. Unsealing member 1
Press 14. And this bimetal plate 118
The piercing portion 115 is pushed into the thin film portion 1 by the pressing force caused by...
11 and the tag gas sealed in the container body 109 is released into the plenum part 106 in the cladding tube 102 through the hollow piercing part 115. After opening, the inside of the container body 109 and the plenum part 106 communicate through the piercing part 115, so the effective volume of the plenum part 106 is reduced by the volume of the parts constituting the tag gas enclosure 108. . And this tag gas inclusion body 1
In 08, the drive mechanism 117 and the opening mechanism 113 such as the opening member 114 are housed in the container body 109, so there is no need for an opening mechanism case like in the conventional case, and the number of end plugs such as the closing member 110 is also reduced. Since the number of welds is small, the structure is simple, and there are few welding points, so it is suitable for mass production. Further, since the number of constituent parts is small and the volume thereof is small, the reduction in the effective volume of the plenum section 106 is also small. Further, in this embodiment, the closing member 110 is a pressed thin plate, and its volume is extremely small.
6... is simply formed by recessing a part of the peripheral wall of the container body 109 inward, and there is no increase in volume due to the provision of these protrusions 116...
Therefore, the reduction in the effective volume of the plenum portion 106 can be further reduced. Furthermore, the container body 109
Since the enclosing tube part 112 is formed by reducing the diameter of the other end, it is easy to manufacture and suitable for mass production, and there is no need to provide an end plug at the other end of the container main body 109, which makes the plenum part 106 more effective. The volume reduction is also smaller.

Note that the present invention is not necessarily limited to the above embodiment.

For example, the drive mechanism is not necessarily limited to the one described above, but may also be one using a shape memory alloy or the like.

Furthermore, the closing member that closes one end of the container body is not necessarily limited to that of the above-mentioned embodiment.

Further, the protrusion that presses the drive mechanism does not necessarily have to be formed as described above.

Furthermore, the present invention is applicable not only to tag gas enclosures housed in fuel rods but also to other tag gas enclosures housed in nuclear reactant containment bodies such as poison tubes.

As described above, in the present invention, a thin film portion is formed at the end of a container body made of a thin-walled tube, and an opening member and a drive mechanism for driving the opening member are housed within the container body. Therefore, the main container can double as an opening member and a guide case for the drive mechanism, and the structure is simple, with fewer end plugs and fewer welding points, making it easy to manufacture and suitable for mass production.
Furthermore, since the number of parts is small and the volume is small, the reduction in the effective volume of the plenum can be minimized.
Furthermore, in the present invention, the diameter of the other end of the container main body is reduced to form a tag gas filling tube.
It is easy to manufacture and suitable for mass production, and
Since there is no need to provide an end plug at the other end of the container body, the effective volume of the plenum can be more effectively prevented from decreasing. Further, since the protrusions of the present invention are formed at equal intervals in the circumferential direction, the support of the drive mechanism is evenly distributed, and no uneven force is applied to the unsealing member.

[Brief explanation of drawings]

1 and 2 show a conventional example, with FIG. 1 being a longitudinal sectional view and FIG. 2 being a longitudinal sectional view in an unsealed state.
3 to 6 show an embodiment of the present invention,
Fig. 3 is a longitudinal sectional view of the fuel rod, Fig. 4 is a longitudinal sectional view of the tag gas enclosure, Fig. 5 is a sectional view taken along line V-V in Fig. 4, and Fig. 6 is the tag gas enclosure in an unsealed state. FIG. 109... Container body, 110... Closure body, 11
1... Thin film part, 112... Sealing tube part, 114...
Unsealing member, 115... protrusion, 116... protrusion,
117... Drive mechanism, 118... Bimetal plate.

Claims (1)

[Claims] 1. The container body consists of a thin-walled tube with both ends closed and a tag gas sealed inside, a thin-walled portion formed at one end of the container body, and the other end of the container body reduced in diameter. a tag gas filling tube portion sealed after sealing tag gas in the main body; an opening member that is housed movably in the axial direction in the container main body and has a sharp tip and a piercing portion that penetrates the thin film portion; A plurality of protrusions are formed by recessing a part of the container body inward and are formed at equal intervals in the circumferential direction. The protrusions are inserted between the protrusions and the unsealing member, and are deformed due to temperature rise, and the unsealing member is opened by the thin film. A tag gas-filled body characterized by comprising a drive mechanism that presses the tag gas toward the target.