JPS6312269B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to reactant containers such as poison tubes of fuel rods or control rods of liquid metal cooled fast breeder reactors.

In general, the poison tubes of nuclear reactor fuel rods and control rods are made with pressure resistance to prevent radioactive materials generated by nuclear reactions of fuel materials and neutron absorbing materials contained inside from diffusing to the outside. The cladding tube is filled with a fuel material or a neutron absorbing material, and then the end of the cladding tube is sealed to prevent leakage of generated radioactive materials. In addition, in the event that the cladding tube is damaged during reactor operation, the amount of radioactive materials in the coolant or cover gas is monitored to detect the damage early.
A device is provided to detect radioactive material leaked due to breakage of the cladding and detect the breakage.
Furthermore, when such a cladding tube is damaged, a device is provided to identify which fuel rod's cladding tube among the many loaded fuel rods has been damaged. For example, in a liquid metal-cooled fast breeder reactor that uses liquid sodium or the like as a coolant, a tag gas, which has a different composition for each fuel assembly, is sealed in the cladding of the fuel rods to prevent cladding damage. If such a problem occurs, the leaked tag gas will be analyzed to determine its composition, and from this composition it will be possible to detect in which fuel assembly the cladding has broken, making it easier to replace the fuel assembly. It is configured. By the way, when manufacturing fuel rods and poison tubes, it is necessary to fill them with tag gases of different compositions.
Manufacturing and management are troublesome, and if there is a leak in the cladding during manufacturing, there is a possibility that the tag gas will leak out before it is loaded into the reactor core. Even if this cladding tube breakage was detected after the furnace was in operation, there was a problem in that it was not possible to identify which fuel assembly it belonged to. 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 is released into the cladding tube for the first time after the reactor is operated, it is easier to manufacture fuel rods and poison tubes, and it is also easier to manage them until they are loaded into the reactor core. Become. However, in all of the tag gas enclosures developed to date, the opening temperature of the tag gas enclosure is 500°C, which is the reactor temperature during steady operation of the nuclear reactor.
It was set to be opened at temperatures between ℃ and 650℃.
For this reason, for example, if the cladding tube contains a defective one from the time of manufacture, it is conceivable that damage will occur immediately after the start of operation of the nuclear reactor. In such a case, of course, substances will leak out, which will be detected and the operation of the reactor will be stopped, but there is a possibility that the tag gas enclosure has not yet been opened in such a situation. In such a case, of course, the tag gas will not leak, so it will not be possible to identify which cladding tube has leaked.
It takes a lot of time to find damaged fuel rods and poison tubes, and there is a possibility that their replacement will be delayed significantly, resulting in a decrease in the reactor's work efficiency.

The present invention has been made based on the above circumstances, and its purpose is to house a tag gas enclosure, which is equipped with a tag gas enclosure and an opening mechanism, in a cladding tube, to facilitate manufacturing and management, and to facilitate the installation of a tag gas enclosure into a reactor core. To reliably identify the damaged cladding even in the case where the tag gas enclosure is opened immediately after loading and the tag gas is released into the cladding, and the cladding is damaged immediately after the reactor starts operating. The objective is to obtain a nuclear reactant container for a liquid metal cooled fast breeder reactor that can be used.

The present invention will be described below with reference to an embodiment shown in the drawings. In the figure, 1 is a nuclear reactant container, such as a fuel rod, of a liquid metal cooled fast breeder reactor, and 2 is a cladding tube thereof. The cladding tube 2 is filled with fuel pellets 3 containing fissile materials such as uranium-235 and plutonium-239. Also,
An upper end plug 4 and a lower end plug 5 are hermetically welded to both upper and lower ends of the cladding tube 2 to form a completely airtight structure, and radioactive materials such as fission products generated by the reaction or fission of the fuel material are It is constructed so that it does not leak to the outside. In addition, this cladding tube 2
A space or plenum 6 is formed in the upper part of the interior, and the gaseous fission products are transferred to this plenum 6.
It is designed to accumulate inside. Further, a spring 7 is provided in this plenum portion 6, and this spring 7 presses and fixes the fuel pellets 3. Further, a tag gas enclosure 8 is accommodated in the plenum portion 6 . This tag gas enclosure 8 is constructed as shown in FIG. In other words, 9 is a container containing tag gas.
It is made of austenitic stainless steel such as SUS304 and SUS316 and has a cylindrical shape, and a thin film portion 10 having a thickness in the range of 0.05 mm to 0.5 mm is formed on one end surface of the cylinder. Further, a sealing tube 11 is provided protruding from the other end surface of the tag gas sealing container 9, and the tag gas is sealed at a predetermined pressure into the tag gas sealing container 9 through the sealing tube 11. After the sealing, the sealing tube 11 is It is sealed and cut airtight. Further, a cylindrical opening mechanism case 12 is concentrically attached to one end of the tag gas filled container 9, and an opening mechanism 13 is provided inside the case 12. Reference numeral 14 denotes a sliding member, which is slidably fitted into the opening mechanism case 12. A piercing member 15 is protruded from the center of the sliding member 14 so as to face the thin film portion 10 of the tag gas filled container 9. This piercing member 15 has a hollow tubular shape, and its tip has a shape cut along a cutting surface 15a oblique to the central axis,
It is formed sharply and is configured to break through the thin film portion 10 and penetrate through the thin film portion 10 .
Furthermore, communication holes 16 communicating with the inside are formed in the peripheral wall of the proximal end of the piercing member 15.
The communication holes 16 and the hollow portion form a tag gas release path. Note that this piercing member 15 is
A stainless steel that can be hardened by heat treatment, such as SUS410, is used, and the angle between the cross-sectional view 15a of the tip and the center line (indicated by α in Fig. 4) is 15°~
It is set within a range of 60°. Communication holes 17 are formed in the peripheral wall of the unsealing mechanism case 12, so that when the piercing member 15 penetrates the thin film portion 10, the tag gas in the tag gas enclosure 9 flows into the piercing member 15. , the communication hole 16 . . . and the communication hole 17 . The piercing member 15 and the sliding member 14 are configured to be moved by the deformation of the bimetal plates 18. These bimetal plates 18 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 alternately arranged. A large number of 2 to 50 bimetal plates are stacked facing each other, and this bimetal plate 18 has a Mn-Cu-N alloy on the high expansion side and a 36Ni-Fe alloy on the low expansion side, and a high expansion side. Ni side
Mn-Fe alloy, low expansion side is 36Ni-Fe alloy, high expansion side is Ni-Mn-Fe alloy, low expansion side is 39Ni.
-Fe alloy, high expansion side is Ni-Mn-Fe alloy, low expansion side is 42Ni-Fe alloy, or high expansion side is Ni
-Mn-Fe alloy with Cr-Fe alloy on the low expansion side, with a thickness of 0.1 mm to 1.0 mm and an outer diameter of
Those in the range of 3.0 mm to 15.0 mm are used. Therefore, as the temperature rises, these bimetal plates 18 . It is composed of And, such an opening mechanism 1
3 is a coolant temperature at the time of fuel loading of the reactor to be loaded, that is, a temperature below the heating temperature for maintaining a metal coolant such as sodium in a liquid state, and at a temperature above room temperature, the piercing member 15 is formed into a thin film portion. 10 and is configured to be opened within a temperature range of, for example, 100° C. or higher and 300° C. or lower. Such settings are made, for example, by appropriately setting the thickness of the thin film portion 10, the structure and number of bimetal plates 18, etc. within the above ranges. For example, bimetal plate 18... is manufactured by Tokyo Shibaura Electric Co., Ltd.
Bimetal plates 18 with a diameter of 4.8 mm are made using 0.3 mm thick bimetal plates (equivalent to JIS TM2), and when 22 of these plates are stacked one on top of the other, the amount of displacement with respect to temperature is as shown in Figure 6. In the figure, a is a calculated value, and b is an actual measured value. If such a series of bimetal plates 18 cannot be freely displaced, a load proportional to the amount of displacement shown in FIG. Therefore, the piercing member 15 is the thin film portion 10
Pressed by On the other hand, when the piercing member 15 is pressed against the thin film portion 10, the opening load required for the piercing member 15 to break through the thin film portion 10 is as shown in FIG. Note that the thin film portion 10 in this case is
It is made of SUS304. Therefore, if the thickness of the thin film portion 10 is about 0.1 mm, the opening load will be about 4.4 kg, and the seal can be opened at a temperature of 200°C. Of course, the dimensions and material of the bimetal plates 18, the thickness of the thin film portion 10, etc. may be changed as appropriate depending on the setting conditions.

In one embodiment of the present invention configured as described above, the tag gas enclosure 8 is manufactured in advance,
When manufacturing the fuel rod 1, it is housed in a cladding tube 2. Therefore, manufacturing of the fuel rod 1 becomes easy. The manufactured fuel rods 1 are then stored under appropriate conditions until they are loaded into the reactor core. In this case, the opening temperature of the opening mechanism 13 of the tag gas enclosure 8 is 100°C.
Since the settings are set above, the package will not be opened at room temperature. Therefore, even if there is a leak in the cladding tube 2 from the beginning, the tag gas will not escape, and management will be easy. When the fuel rods 1 are loaded into the reactor core, the bimetal plate 1
8... is curved as shown in FIG.
is pressed against the thin film portion 10 and penetrates through it. Therefore, the tag gas in the tag gas enclosure 9 is released into the cladding tube 2 through the communication hole 16 of the piercing member 15 and the communication hole 17 of the opening mechanism case 12, and is also released into the cladding tube 2. It communicates with the inside of the tag gas enclosure 9. If the cladding tube 2 has a defect from the time of manufacture, the cladding tube 2 may be damaged in the early stages of operation of the reactor, but in this embodiment, the tag gas enclosure 8 is already damaged when fuel is loaded. When the cladding tube 2 is opened, tag gas is filled in the cladding tube 2, and as soon as the cladding tube 2 is broken, this tag gas leaks into the reactor cover gas, etc. By analyzing this, it is possible to detect which fuel is damaged. be able to. Therefore, even if the fuel cladding tube 2 is damaged before the reactor reaches steady operation, it is possible to reliably detect in which fuel assembly the damage has occurred. In addition, in this embodiment, since the disc-shaped bimetal plates 18 are stacked one on top of the other, the load generated when the temperature rises can be increased, and this load can be applied directly to the piercing portion 15. It can be constructed so as to penetrate through the thin film portion 10, and the structure is simple and the number of parts can be reduced. Therefore, the volume occupied by these parts is reduced, the reduction in the effective volume of the plenum portion 6 is reduced, and the decrease in the life of the fuel rod 1 can be reduced. That is, the plenum section 6 is for storing gas such as nuclear fission products, and when its effective volume is reduced, its effect is also diminished, and the life of the fuel rod 1 is also shortened, as shown in FIG. 8. However, since the structure of this embodiment is simple and the number of parts is small as described above, the volume of these parts is small and the reduction in the effective volume of the plenum part 6 is reduced accordingly, which reduces the life span of the fuel rod 1. can be made smaller. Further, in this embodiment, the piercing member 15
Since the distal end portion is shaped as if it were cut along the cutting surface 15a oblique to the central axis, the reliability of operation can be improved. That is, the bimetal plate 1
8... are deformed by heating, but the piercing member 15 comes into contact with the thin film part 10 and these bimetal plates 18...
... cannot be freely deformed and is in a compressed state,
The piercing member 15 is pressed by the elastic repulsion force. When the tip of this piercing member 15 begins to break through the thin film portion 10, this piercing member 15
moves forward, the bimetal plates 18... extend, and their elastic repulsive force decreases. Therefore, if the piercing member 15 is of a type whose resistance increases as it advances into the thin film portion 10, the piercing member will stop when only a small portion of its tip breaks through the thin film portion. I end up. Of course, if the amount of deformation and elastic force of the bimetal plates 18 are set sufficiently large, the piercing member 15 can be inserted to a sufficient depth. However, if this is done, the temperature rises to a certain extent, and the tip of the piercing member 15 begins to break through the thin film part 10 with the bimetal plates 18 deformed to some extent, and thereafter as the temperature rises, the bimetal plates 18... As the amount of deformation increases and the elastic repulsive force increases, the piercing member 15 gradually enters the thin film portion 10. Therefore, this piercing member 1
5 begins to break through the thin film portion 10 until it penetrates to a sufficient depth, the temperature range increases. By the way, the opening mechanism 13 of the present invention does not open at room temperature, but opens at a temperature below the preheating temperature of the metal coolant.
The package must be opened within a temperature range of ℃, and in actual products this temperature range is extremely narrow considering various errors. Therefore, as mentioned above, the piercing member 1
If the temperature range from when the needle 5 starts to break through the thin film part 10 until it fully penetrates is large, this temperature range will be larger than the above temperature range, and the piercing member 15 will break through the thin film part 10 at a temperature lower than the above temperature range. There may be cases where the piercing member 15 does not penetrate to a sufficient depth even if the temperature exceeds the above-mentioned temperature range, making it impossible to reliably open the seal within the predetermined temperature range. However, in this embodiment, since the tip of the piercing member 15 has a cutting surface 15a that is inclined with respect to the central axis, the edge 15b of this cutting surface 15a acts as a breaking blade to tear the thin film portion 10. to do. This edge 15b is the fifth
As shown in the figure, the direction at the tip is perpendicular to the central axis, so when the tip cuts through the thin film part 10, that is, when the piercing member 15 starts to break through the thin film part 10, the resistance is relatively large. On the other hand,
As shown in FIG.
When the edge 15b enters the thin film portion 1 to a certain extent, the edge 15b
The angle θ formed between the tangent of the portion P that cuts through the center line and the center line becomes smaller as the piercing member 15 advances, and the resistance force that cuts the thin film portion 10 also decreases. This kind of piercing member 1
5 has a characteristic that the resistance force is large when it starts to break through the thin film portion 10, and once it breaks through, the resistance force decreases as it penetrates or does not change much. Therefore, even if the piercing member 15 enters and the bimetal plates 18 extend and their elastic repulsion force decreases, the above characteristics compensate for the decrease in the elastic repulsion force. This kind of piercing member 1
When the tip of tip 5 starts to break through the thin film portion 10, it quickly penetrates to a sufficient depth, and the temperature range from the time it starts to break through until it penetrates to a sufficient depth becomes extremely small. Therefore, even if the opening temperature range is narrow, the seal can be opened accurately and reliably within this temperature range. Note that this characteristic applies to the cut surface 1
If the angle α exceeds 60, the effect will not be sufficient, and if it is less than 15, the tip will become too sharp and easily deform. The resistance force, that is, the opening load becomes unstable. In addition, this opening characteristic is influenced not only by the shape of the tip of the piercing member 15 but also by the thickness of the thin film portion 10, the thickness of the bimetal plate 18, the outer diameter, etc. In the case of a breeder reactor, these may be specifically set as appropriate within the range of the above-mentioned embodiment. Furthermore, in this embodiment, the tag gas enclosure 9, thin film portion 10, etc. are made of austenitic stainless steel, and this material is the same as that used for the cladding tube 2, poison tube, etc. Therefore, it does not affect the nuclear properties of fuel rod 1, etc.

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

For example, the configuration of the unsealing mechanism is not necessarily limited to the above-mentioned one, and various configurations can be envisaged for the tag gas release path of the piercing member, the communication hole of the unsealing mechanism case, and the like.

Furthermore, the present invention is applicable not only to fuel rods but also to other control rods containing nuclear reactants, such as poison tubes.

As described above, the present invention comprises a cladding tube containing a nuclear fuel material or a neutron absorbing material, a tag gas enclosure housed in a plenum section of the cladding tube and having a tag gas sealed therein, and a thin film part for sealing the tag gas enclosure container. , an opening mechanism case that is integrally attached to the tag gas-filled container via the thin film part;
This opening mechanism is housed in the case and is placed opposite to the thin film part, and the tip part has a shape cut along a cutting surface oblique to the axial direction, and the tip part breaks through the thin film part to allow the tag gas collection container. a piercing member for releasing the tag gas inside the container into the opening mechanism case through the tag gas release path; and a plurality of circles accommodated in the opening mechanism case and stacked one on top of the other with a low expansion side and a high expansion side facing each other alternately. It is composed of a plate-shaped bimetallic plate, and is deformed when heated to a temperature below room temperature but above room temperature to maintain the metal coolant in a liquid state, causing the piercing member to break through the thin film. The biasing bimetal plate part and the piercing member formed in the opening mechanism case penetrate the thin film part and release the tag gas from inside the tag gas sealed container into the opening mechanism case through the tag gas release path of the piercing member. It is characterized by having a communication hole for discharging into the cladding tube. Therefore, the production of fuel rods or poison chives;
In addition to being easy to store, once these fuel rods, poison tubes, etc. are loaded into the reactor core, the tag gas enclosure is immediately opened and the tag gas is filled into the cladding tube, preventing damage to the cladding tube in the early stages of reactor operation. Even in such a case, the tag gas is reliably released and the damaged fuel can be reliably identified. Furthermore, the tip of the piercing member of the present invention is
Since the shape is cut along a cut surface oblique to the axial direction, even if the opening temperature range is narrow, the thin film can be broken through and opened accurately and reliably. Furthermore, the opening mechanism case containing the piercing member and the bimetal plate part can be attached to the tag gas-filled container through the thin film part to form a tag gas-filled pair in advance, and this can be simply loaded into the cladding tube. Because I will finish,
The nuclear reactant container is easy to manufacture.

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention; FIG. 1 is a longitudinal sectional view, FIG. 2 is a longitudinal sectional view of the main part, FIG. 3 is a longitudinal sectional view of the main part to explain the action, and FIG. Fig. 5 is a perspective view of the tip of the member, Fig. 5 is a front view of the same, Fig. 6 is a diagram showing the characteristics of bimetal, Fig. 7 is a diagram showing the relationship between the thickness of the thin film part and opening load, and Fig. 8 is a diagram showing the plenum. FIG. 3 is a diagram showing the relationship between the effective volume of the fuel rod and the life of the fuel rod. 1... Fuel rod (nuclear reactant material container), 2... Cladding tube, 3... Fuel pellet (nuclear reactant material), 6...
...Plenum part, 8...Tag gas enclosure, 9...Tag gas enclosure, 10...Thin film part, 13...Opening mechanism, 15...Punching member, 18...Bimetal plate.

Claims (1)

[Scope of Claims] 1. A cladding tube containing a nuclear fuel material or a neutron absorbing material, a tag gas enclosure housed in a plenum part of the cladding tube, and having a tag gas sealed therein;
A thin film part that seals the tag gas sealed container, an opening mechanism case integrally attached to the tag gas sealed container via this thin film part, and a tip part housed in the opening mechanism case and placed opposite to the thin film part. has a shape cut along a cutting surface oblique to the axial direction, and the tip breaks through the thin film part to release the tag gas in the tag gas receiving container into the opening mechanism case through the tag gas release path. It is composed of a piercing member and a plurality of disc-shaped bimetal plates housed in the opening mechanism case and stacked one on top of the other with the low expansion side and the high expansion side facing each other alternately, and maintains the metal coolant in a liquid state. a bimetal plate portion that deforms when heated to a temperature below the heating temperature for storing and above room temperature and urges the piercing member in a direction to break through the thin film; and a bimetal plate portion formed on the opening mechanism case and the piercing member a communication hole that penetrates the thin film part and releases the tag gas released into the opening mechanism case from inside the tag gas sealed container through the tag gas release path of the piercing member into the cladding tube. Nuclear reactant container of a cooled fast breeder reactor. 2. The thin film portion of the tag gas enclosure is made of austenitic stainless steel and has a thickness in the range of 0.05 mm to 0.5 mm, and the angle between the cut surface of the tip of the piercing member and the center line is
15° to 60°, and the bimetallic plate has a thickness in the range of 0.1 mm to 1.0 mm and an outer diameter in the range of 3.0 mm to 15.0 mm. A nuclear reactant container for a liquid metal cooled fast breeder reactor according to item 1.