JPH04204199A - Fuel breakage detector - Google Patents

Abstract

PURPOSE:To detect breakage of a fuel as early as possible without providing a dedicated equipment separately by making a coolant sodium flow into a sodium pot to send a gas to a radiation detector as generated by bubbling the sodium with the blowing of an argon gas thereinto. CONSTITUTION:A radioactive fission product FP released into a coolant sodium 7 from a fuel pin broken flows to an upper guide pipe 34 of a control rod from a fuel assembly outlet directly or through a sodium introduction pipe and reaches a control rod 15 and a clipper or an electromagnet 29 on a flow of the sodium 7. Moreover, the FP rises through a sodium passage pipe 43 to a sodium pot 42 within an extension shaft 31 on an ascending current of the sodium 7. In the pot, the FP shifts to a slight argon gas space 45 of the pot 42 forcibly without being diluted so much from the sodium 7 with a forcible bubbling of an argon gas from an argon gas supply pipe 44. Then, it is carried to a radiation detector within a argon gas transfer pipe 46 by a gas pressure to measure a radioactivity level of the FP.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fuel damage detection device for a fast breeder reactor (hereinafter abbreviated as FBR).

[Conventional technology]

When the core fuel is damaged during reactor operation, radioactive fission products (hereinafter abbreviated as FP) accumulated in the fuel bottle are released into the coolant sodium. FP released
When the damage is as small as a pinhole, rare gases such as Xe and Kr migrate into the cover gas space, and when the damage becomes larger, volatile or non-volatile gases such as Br, I, Cs and Sr are released. Sexual FP is released. In other words, the released FP is not only dispersed in the primary cooling system along with the flow of coolant sodium, but also migrates from the coolant sodium to the cover gas space, so the atomic couplant can be used over a wide range of l2. There is a possibility of contamination by crossing FP. In order to prevent the spread of contamination due to plant FP, it is necessary to detect fuel damage early, understand the scale of the damage, and quickly shut down the reactor if necessary.

In addition, in order to prevent a drop in plant availability, it is necessary to identify the location of damaged fuel at an early stage and quickly remove the damaged fuel from the reactor due to fuel damage. In general, detection of fuel damage, understanding of the scale of the damage, and identification of the location of the damaged fuel are carried out by installing a dedicated device in the plant to detect the FP released into the coolant sodium during the above-mentioned fuel failure. ing.

FIG. 9 shows a schematic diagram of a general loop type FBR, and the prior art will be explained below with reference to FIG. In FIG. 9, the furnace vessel 2 is closed off by a shielding plug l.
The heat generated in the fuel 4 loaded in the core 3 is transported to the intermediate heat exchanger 8 by the flow of coolant sodium 7 flowing in the piping 6 of the primary cooling system by the driving force of the pump 5. Found out,
Here, heat is transferred to a secondary cooling system (not shown).

If fuel damage occurs in Figure 9, two steps are required to detect it.
Two methods have been adopted. One is called the cover gas method, in which the gamma rays of the rare gas FP and the rare gas F that are released into the coolant sodium 7 and then transferred to the cover gas space 9 are used.
This method involves electrically collecting ionic nuclides such as Rb and Cs generated by the radioactive decay of P (also known as the precivitator method), and detecting the β rays emitted by the radiation detector 10.

Another method is called the delayed neutron (hereinafter abbreviated as DN) method, in which DN emitted by FPs such as Br and I carried by the flow of the coolant sodium 7 is transferred to the primary cooling system piping 5.
This is a method of detection using a DN detection device 1i1i) 11 provided in close proximity to the DN detection device 1i1i). When FP is detected by these methods and the determination device [12 determines that the radioactivity concentration exceeds or has exceeded the set limit value, the atoms in the upper reactor mechanism 13 located directly above the reactor core 3 An instruction is given to the reactor shutdown device 14, and the control rod 1 containing the neutron absorbing material is
5 will be dropped into the reactor core 3, and the operation of the reactor will be stopped.

On the other hand, one method for identifying damaged fuel is the shipping method as disclosed in Japanese Patent Application Laid-Open No. 58-5696. conduct.

This method involves installing a shipping port of the shipping device 16 at the top of the fuel assembly 17 containing a fuel bottle 18 that is suspected of being damaged due to changes in the burnup of the core fuel or the temperature at which the fuel assembly 17 exits during reactor operation. 19, and bring the lower ends of the parts into close contact.

Next, the coolant sodium 7 in the fuel assembly 17 is led to the sodium bot 21 through the sampling pipe 20, and argon gas is blown into the sodium through the argon gas supply pipe 22 to bubble it to remove FP contained in the sodium. The gas transfer pipe 2 is forcibly moved to the gas space 23.
4, the FP transferred to the radiation detector 10 is sent to the radiation detector 10, its radioactivity concentration is measured, and the presence or absence of damage is determined. The argon gas containing the FT' gas that has exited the radiation detector 10 is sent to a waste gas treatment device (not shown), or is returned to the internal bar gas space 9 of the furnace vessel 2 through a return gas pipe 25 as shown in FIG. , the shipping boat 19 is driven by the shipping device 16.
This is done by the drive mechanism 26 of.

Another identification method is called the tag gas method.

In this method, "Kr" which is not generated by a nuclear fission reaction in the internal space of the fuel bottle 18 is prepared in advance.

Position indicating gas (tag gas) that is a combination of various stable isotopes such as IOK r, ""X e, ""X e, etc.
In this method, when a fuel failure occurs, the tag gas that migrates to the cover gas space 9 is sampled, concentrated, and analyzed by a mass spectrometer, and the location of the damaged fuel is identified from the gas composition of the tag gas. .

[Problem to be solved by the invention]

However, the above conventional technology has the following drawbacks. First, in the cover gas method, which is one of the fuel failure detection methods, the rate at which FP, which is the measurement target of the radiation detection tube, is transferred from the coolant sodium 7 to the cover gas (transfer rate)
(Also, since it is carried along with the flow of the cover gas to the detector, it has to be diluted with the cover gas, which has the disadvantage of lowering the detection sensitivity. The argon gas filling the cover gas space 9 is exposed to high-density neutrons in the reactor and becomes activated, emitting strong gamma rays.
Since Ar is generated in large quantities in the cover gas, there is a problem in that it becomes a strong source of interference in gamma ray measurement of rare gas FP.

In the DN method, which is another detection method, neutrons from the core 3, where a large amount of strong neutrons are present, leak into the installation part of the DN detector 11. Since it is quite difficult to shield this, the background of neutrons will be high due to leaked neutrons at the installation location of the DN detector 11, and unless a very large fuel damage occurs, it will be difficult to distinguish between the DN signal and the pack land due to leaked neutrons. There was a problem that it didn't stick.

On the other hand, in the method of identifying the location of damaged fuel, the shipping method, which is the prior art described above, is limited to use during reactor shutdown or very low-power operation, and one-by-one
Because the actual fuel assembly must be inspected, installation of the device takes a considerable amount of time, including time for removal. In addition, when carrying out identification work, in the case of micro-damages such as hair cracks, it is important to note that the damaged hole in the fuel bottle will naturally close due to the reduction in temperature of the fuel bottle cladding due to the furnace shutdown or reduction in furnace output. , FP may not be released during the identification process. For this reason, there was a problem in that it was difficult to find damaged fuel.

Next, in the tag gas method, the number of fuel assemblies used, that is, the number of fuel bottles, increases as the size of the nuclear reactor increases, but on the other hand, the number of tag gas combinations of Kr and Xe is limited. That is, as the furnace becomes larger, it becomes impossible to contain a unique combination of tag gases in each fuel bottle, and tag gases of the same composition must be used simultaneously in a plurality of fuel bottles. For this reason, it is difficult to identify damaged fuel only by tag gas composition analysis. In addition, the amount of tag gas contained in each fuel bottle is small, and analysis requires a large-scale tag gas concentrator, high-precision mass spectrometry, and a dedicated analysis code to quickly identify damaged fuel. The drawback is that the cost is quite high due to the above.

In order to solve this problem, the purpose of the present invention is to quickly detect fuel damage without the need for separate dedicated equipment, in any operating state of the reactor, such as when the reactor is operating at its rated power or when it is shut down, and to detect the scale of the damage. detection, identification of damaged fuel,
Alternatively, it is an object of the present invention to provide a fuel failure detection device that can quickly push a control rod into a reactor core and bring the reactor to an emergency stop, if necessary.

[Means to solve the problem]

The above objective can be achieved as follows.

(1) Permanent equipment in the upper reactor mechanism located directly above the reactor core in a fuel failure detection system for fast breeder reactors that detects fuel failure by measuring fission products present in the coolant or cover gas. Coolant sampling line and sodium pot installed inside, inert gas supply that bubbles the sampled coolant with inert gas and forcibly transfers fission products contained in the coolant into the cover gas. a transfer pipe for sending the inert gas containing the transferred fission products to the radiation detector, a radiation detector, and a return pipe for the inert gas containing the fission products in the radiation detector.

(2) In (1), a control rod is provided with each arm for lifting the control rod on both sides of the upper end of the control rod, and each person near the base of the six arms through which coolant flows into the gap between each arm. The magnetic body and electromagnet placed on the top of the six arms of the rod, the extension shaft that connects the electromagnet and the inside of the drive mechanism of the control rod, the sodium pot installed in the extension shaft, and the one end that passes through the extension shaft and the electromagnet. have a sampling line leading to the sodium pot and the other end to the air gap between each arm of the control rod.

(3) In (1), a control rod is provided with each arm for lifting the control rod on both sides of the upper end of the control rod, and each person near the base of the six arms through which coolant flows into the gap between each arm. The magnetic body and electromagnet placed on the top of the six arms of the rod, the extension shaft that connects the electromagnet and the inside of the drive mechanism of the control rod, the sodium pot installed in the extension shaft, and the sodium pot that passes through the extension shaft and has one end attached to it. The other end shall have a sampling line leading to the side of the extension shaft.

(4) In (1), a control rod is provided with each arm for lifting the control rod on both sides of the upper end of the control rod, and one person near the base of each piece through which coolant flows into the gap between each arm. The magnetic body and electromagnet placed on the top of each piece of the rod, the extension shaft connecting the electromagnet and the inside of the drive mechanism of the control rod, the sodium pot installed in the extension shaft, the extension shaft passing through the inside of the extension shaft and the inside of the electromagnet, and one end The sodium pot shall have a sampling line at the other end leading to the gap between each arm of the control rod, and one end leading to the sodium pot and the other end leading to the side of the extension shaft.

(5) In (1), a control rod is provided with each arm for lifting the control rod on both sides of the upper end of the control rod, and each member near the base of each piece through which coolant flows into the gap between each arm. The magnetic body and electromagnet placed on the top of each piece, the extension shaft connecting the electromagnet and the inside of the control rod drive mechanism, the sodium pot installed in the extension shaft, and the extension shaft passing through the extension shaft with one end connected to the sodium pot and the other end. shall be provided on the side of the extension shaft, and the inlet at the other end shall have a sampling line with a coolant intake pipe installed toward the coolant rising along the side of the extension shaft.

(6) In <1), a control rod is provided with each arm for lifting the control rod on both sides of the upper end of the control rod, and each member near the base of each piece through which coolant flows into the gap between each arm. The magnetic body and electromagnet arranged on the top of each piece, the extension shaft connecting the electromagnet and the inside of the control rod drive mechanism, the sodium pot installed in the extension shaft, the inside of the extension shaft and the electromagnet passing through, and one end of the sodium pot. The other end of the pot is connected to a sampling line that leads to the gap between each arm of the control rod, and the extension shaft is connected to one end of the sodium pot, and the other end is provided on the side of the extension shaft. shall have a sampling line with a coolant intake pipe installed towards the rising coolant along the side of the pipe.

(7) In (1), the gripper-type control rod holding device has a sampling line that penetrates inside the drive rod of the gripper.

(8) In (1), the control rod holding device of the gripper type has a sampling line provided on the side of the drive rod of the gripper.

(9) In a fast breeder reactor fuel failure detection device that detects fuel failure by measuring fission products present in the coolant, each piece for lifting the control rod installed on both sides of the upper end of the control rod. The control rod has a large hole near the base of the piece that allows the coolant to flow into the gap between each arm, the magnetic body and electromagnet are placed at the top of each piece of the control rod, and the lower end is directly above the electromagnet. An extension shaft that is connected to the electromagnet and whose upper end is fixed with a shielding plug, and a sodium flow pipe that has an entrance facing the gap between each piece of the control rod and passes through the electromagnet and the extension shaft to reach the radiation measuring device. , a radiation measuring device, and a sodium return pipe.

[Effect]

The present invention is achieved by equipping a nuclear reactor shutdown device, which is always installed in a nuclear reactor, with a function of a fuel damage detection method using a shipping method. That is, the 11th
As shown in the figure, a conventional general FBR reactor has a thermometer 27 for measuring the outlet temperature of the fuel assembly 17 in the upper reactor mechanism 13 located directly above the reactor core, as well as a gripper 28 or an electromagnet 29 ( A nuclear reactor shutdown device for holding the control rods 15 is incorporated according to Japanese Patent Application Laid-Open No. 1-155295.

In FIG. 11, 30 is a control rod drive mechanism, 31 is an extension shaft connecting the control rod 15 and the drive mechanism 30, and 32 is a control rod 15
A sodium inlet pipe is provided for directing the flow of coolant sodium 7 passing through the fuel assembly 17 located around the lower guide pipe 33 of the fuel assembly 17 to the control rod 15 and electromagnet 29 side in the upper guide pipe 34. It shows. FIG. 12 shows a schematic diagram of the gripper system, and FIGS. 13 and 14 show schematic diagrams of the electromagnet system. In Figures 12 to 14,
35 is a gripper, 41 is a gripper drive rod, 36 is a magnetic body provided on the upper part of the control rod 15, 37 is a coil, 38 and 39 are sodium inflow and outflow holes, and 40 is a power cable. In such a configuration, a sodium pot is provided in the extension shaft 31, and the coolant sodium 7 that has flowed into the upper guide pipe 34 through the reactor core is transferred to the gripper 2.
A sodium inlet pipe 32 is provided which is a line through which sodium flows into the sodium bot from the 8th section or the electromagnet 29th section and flows out into the upper guide tube 34 again through this. Furthermore, by providing an argon gas supply pipe for bubbling the sodium by blowing argon gas into the sodium flowing in the sodium pot, and a transfer pipe for sending the bubbling gas released into the space inside the sodium pot to the radiation detector, The objective is achieved by equipping the nuclear reactor shutdown system with the function of a conventional shipping type fuel damage detection system.

According to the above configuration, FP released from the damaged fuel bottle 18 into the coolant sodium 7 flows from the outlet of the fuel assembly 17 into the upper guide pipe 34 of the control rod directly or via the sodium introduction pipe 32, Control rod 15 and gripper 28 or electromagnet 2 located above along the flow of sodium
It reaches 9. (In the conventional technology, the electromagnet 29 and the magnetic body 3
Sodium inflow hole 3 for efficient heat transfer to 6
8 and a sodium outflow hole 39 are provided. )Furthermore, the FP rises in the sodium flow pipe along with the upward flow of sodium up to the sodium bottle provided in the extension pipe 3I, where a small amount of gas in the sodium pot is removed from the sodium by forced bubbling of argon gas. It is forcibly transferred into space without being diluted much, and is carried by gas pressure inside the transfer pipe to the radiation detector.

Here, the radioactivity concentration of FP is measured. That is, in the configuration according to the present invention, the fuel damage device is installed directly above the reactor core, and the positional relationship from the fuel damage part to the sodium pot is almost vertical. As a result, the released FP can be transferred without going against the flow of the coolant sodium 7, and the radioactivity of the FP can be inspected in the shortest time at the location closest to the damaged fuel. Compared to conventional technology, this eliminates most concerns about the delay in FP transition time and the drop in detection sensitivity caused by the gas transferred to the detector, allowing fuel damage to be detected quickly and accurately. . Further, according to the above configuration, when the control rod is held by an electromagnet, for example, the sodium inlet pipe 32 allows sodium to flow in from the outlet of the fuel assembly 17, which is limited in its circumference, and the position where the FP is detected, In other words, this indicates that damage has occurred in the fuel assembly 17 located around the control rod where the FP was detected. This makes it possible to squeeze out fuel that is suspected of being damaged from the beginning. This means that even if the number of fuels increases as the size of the reactor increases, the number of control rods will also increase accordingly, and since these control rods have a fuel damage detection function, no matter where fuel damage occurs, it can be detected early. The identification function will not deteriorate, that is, the detection, identification, and removal of damaged fuel will be possible even when the size is increased.
[Embodiment] An embodiment of the present invention is shown in FIG. 1, and other embodiments to which this embodiment is applied are shown below. According to Figures 2 to 5,
An application example in which a gripper system is used to hold a control rod will be described with reference to FIG. 6.7, and another embodiment of the present invention will be described with reference to FIG. 8. Note that the same reference numerals are used in the embodiments when they are the same as those explained in the conventional example.

FIG. 1 is a longitudinal sectional view showing the configuration of one embodiment, in which a control rod 15, which is the most basic of the present invention, is connected to an electromagnet 29 and a magnetic body 3.
6 is held by magnetic adsorption and lifted into the upper guide tube 34 located directly above the reactor core 3. 1st
In the figure, a sodium pot 42 is provided in an extension shaft 31 that connects an electromagnet 29 and a control rod drive mechanism 30 (not shown), and sodium passes through the electromagnet 29 from the upper part of the control rod 15, and the sodium pot 42 A sodium flow tube 43 is provided for passage through and back to the upper guide tube 34. Further, the sodium pot 42 is provided with an argon gas supply pipe 44 for bubbling sodium passing through the interior thereof. Sodium pot 42 is
It is installed at the same level as the sodium liquid level or below the sodium liquid level, and when sodium flows inside the sodium pot 42, the sodium pot 4
An argon gas space 45 is created in the upper part of the chamber 2. An argon gas transfer pipe 46 is provided from the argon gas space 45 to the radiation detector IO located at the top. An argon gas return pipe 47 is provided that returns from the radiation detector lO to the upper guide pipe 34, but the outlet of the return pipe is located above the sodium liquid level or at the argon gas transfer pressure (i.e., the argon gas in the sodium pot). Depending on the balance between the gas pressure in the gas space 45 and the gas pressure in the cover gas space 9 in the furnace vessel 2, it is provided below the sodium liquid level. In the configuration of this embodiment, when fuel damage occurs in the core 3, the coolant sodium 7 is removed from the damaged fuel bottle 18.
The released FP flows from the outlet of the fuel assembly 17 into the upper guide tube 34 of the control rod via the sodium introduction tube 32 and reaches the control rod 15 along with the flow of sodium. Here, the control rod 15 is
It enters the sodium flow pipe 43 through the magnetic body 36, rises along with the upward flow of sodium, and reaches the sodium pot 42. The FP in the sodium is forcibly transferred from the sodium to the argon gas space 45 by bubbling of the sodium with the argon gas sent from the argon gas supply pipe 44, and then passed through the gas transfer pipe 46. After reaching the radiation detector 10 and having the radioactive concentration of the FP measured, it is returned to the upper guide pipe 34 through the argon gas return pipe 47.

According to the configuration of this embodiment, the FP carried by the flow of the coolant sodium 7 is stored in the upper guide pipe 34 closest to the position where the coolant sodium 7 is released, and the in-furnace sodium does not come out into the cover gas space. Since sampling is performed inside the reactor (in this example, at the reactor shutdown equipment) and the radioactivity concentration is measured, the transfer rate and time of FP from sodium to cover gas is delayed compared to conventional technology. The dilution effect caused by the coolant sodium 7 and the cover gas can be almost ignored. As a result, the problem of reduced detection sensitivity is almost eliminated, fuel damage can be detected quickly and accurately, and if necessary, the reactor can be quickly shut down by disconnecting the control rod that is the shortest distance away. It will be possible. Further, according to the configuration of this embodiment, the sodium flowing into the upper guide pipe 34 is transferred to the sodium introduction pipe 34.
2 indicates that sodium is coming from the outlet of the fuel assembly 17 in a fairly limited area around it, indicating that damage has occurred in the fuel assembly 17 around the position where FP was detected, that is, the control rod position, and the fuel When damage is detected, it is possible to squeeze out fuel that is suspected of being damaged from the beginning. A reactor shutdown device is always installed in a nuclear reactor, and as the reactor becomes larger, the number of control rods increases, and since it has a fuel damage detection function, it is possible to detect fuel damage at any location in the reactor core. Even if this occurs, the early detection and identification functions will not deteriorate.

FIG. 2 shows another embodiment to which the embodiment shown in FIG. 1 is applied. The difference from the embodiment shown in FIG. It was established in This is the result of considering two things.
First, it can be applied when there is a concern that the magnetic force of the electromagnet 29 may be weakened depending on the material of the electromagnet 29 when there is a penetrating portion such as the sodium flow pipe 43. The second is control rod 1
5. Even when the sodium inflow hole 38 and the sodium outflow hole 39 cannot be opened very large on the upper magnetic body 36 and electromagnet 29 side in consideration of sodium thermal efficiency, the required amount of sodium can be ensured to flow into the sodium pot 42. It is.

FIG. 3 shows another embodiment to which the embodiment shown in FIG. 1 is applied, and is a combination of FIGS. The amount of sodium required in the sodium bot 42 is supplemented by the sodium taken in from the side surface of the extension shaft 31.

FIG. 4 shows another embodiment that is the same as the embodiment shown in FIG. By attaching the extension shaft 31 to face the rising flow of sodium, the efficiency of sodium flowing into the sodium bot 42 can be increased.

FIG. 5 shows another embodiment to which the embodiment shown in FIG. 1 is applied, and is a combination of FIG. 1 and FIG.
This is the result of combining each to utilize the above-mentioned characteristics.

FIG. 6 shows a case in which the present invention is applied to a nuclear reactor shutdown device that uses a gripper method for holding control rods. In this embodiment, a sodium flow pipe 43 is installed inside the gripper drive rod 41 of the gripper 28. The upper part of the sodium flow pipe 43 includes the same structure as in the case of FIG. 1 described above for the sodium pot 42, etc., and its function and operation are also the same as in the above case. Even in the case of the gripper method, it can function as a fuel damage detection device by installing a sodium pot 42 or the like in the upper part of the gripper drive rod 41 or the upper part of the extension shaft 31 connected via a bellows (not shown) or the like. can be added.

FIG. 7 shows another embodiment of the main part of the embodiment shown in FIG. 6, in which a sodium flow pipe 43 is provided on the side surface of the gripper drive rod 41.

This embodiment also shows that the function as the fuel damage detection device described above is added.

FIG. 8 shows an embodiment of the damaged fuel detection device according to the present invention in which the sodium flow pipe 43 is guided to the upper part of the reactor through the shielding plug 1 and FP in the sodium is directly measured by the radiation detection device 48. It is something. According to this example, FP from sodium to argon cover gas
There is no need to perform forced migration operations, and non-volatile F
It is possible to measure FP that does not migrate into argon gas such as P.9 In this example, the sodium flow pipe 4
3, the return pipe 49, the radiation detection device, etc., by heating the entire system with a heater or the like, so that blockage of sodium in the sodium distribution pipe 43, etc. can be avoided.

In addition, in the configuration according to the present invention described above, there is no factor that strongly interferes structurally with the original reactor shutdown device or obstructs its function, and there is no factor that would interfere strongly with the original reactor shutdown device or interfere with its function, and the reactor shutdown device using only control rods is not affected. Needless to say, it can be made to work just as well.

Conversely, even if the control rods for shutting down the reactor have fallen into the reactor core, the openings of the sodium flow holes 43 remain in their original positions, so it goes without saying that any abnormalities in the reactor can always be dealt with.

As described above, the present invention has been described for the case where it is applied to a fast breeder reactor that uses fluid metal as a coolant, but it can also be applied to other types of reactor shutdown devices that use water or gas as a coolant to detect fuel damage. It is of course possible to make it function as a device, and although the present invention has been explained using the above-mentioned embodiments, the present invention is not limited to the above-mentioned embodiments.

〔Effect of the invention〕

According to the present invention, fuel damage can be quickly detected in any operating state such as when the reactor is operating at its rated power or when it is stopped, and the scale of the damage can be detected, the damaged fuel can be identified, or control rods can be quickly moved to the core as needed. It is possible to provide a fuel damage detection device that can be inserted into a reactor to make an emergency shutdown of the reactor, and an effect that greatly contributes to the safety of the reactor can be obtained.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional view of an embodiment of a fuel failure detection device that holds a control rod by an electromagnet according to an embodiment of the present invention, and FIG. 2 is a longitudinal sectional view of another embodiment of the main part shown in FIG. 1. 3 is a vertical cross-sectional view of an embodiment in which the main parts shown in Figs. FIG. 5 is a longitudinal sectional view of an embodiment in which the main parts shown in FIGS. 1 and 4 are combined, and FIG. 6 is a part of a fuel failure detection device that holds a control rod with a gripper. FIG. 7 is a vertical cross-sectional view of another embodiment of the main part shown in FIG. 6, and FIG. 8 is a diagram of a fuel failure detection device that directly measures radiation of sodium passing through the core. FIG. 9 is an explanatory diagram showing the overall configuration of a nuclear reactor according to the prior art, and FIG. 10 is a schematic cross-sectional view showing an embodiment of a damaged fuel identification device using the shipping method according to the prior art. 11 is a longitudinal cross-sectional view showing an outline of a reactor shutdown device according to the prior art, and FIGS. 12 to 14 are an explanation showing an outline of a control rod holding method used in the reactor shutdown device shown in FIG. 11. 12, 13, and 14 are cross-sectional perspective views of a gripper type, an electromagnetic type, and the type shown in FIG. 13, respectively. 15... Control rod, 28... Gripper, 29... Electromagnet, 31... Extension shaft, 34... Upper guide tube, 36
...Magnetic material, 41...Gripper drive rod, 42...
Sodium pot, 43... Sodium distribution pipe, 44
...Argon gas supply pipe, 45...Argon gas space, 46...Argon gas transfer pipe, 47...Argon gas return pipe.

Claims (1)

[Claims] 1. In a fuel failure detection device for a fast breeder reactor that detects fuel failure by measuring nuclear fission products present in the coolant or cover gas, an upper part of the reactor located directly above the reactor core. The coolant sampling line and sodium pot are installed in permanent equipment in the mechanism, and the sampled coolant is bubbled with an inert gas to forcibly remove the fission products contained in the coolant. an inert gas supply pipe that transfers the inert gas containing the transferred fission products into the gas; a transfer pipe that sends the inert gas containing the transferred fission products to a radiation detector; the radiation detector; and the inert gas containing the fission products in the radiation detector. A fuel failure detection device for a fast breeder reactor, characterized by having a gas return pipe. 2. The control rod is provided with arms for lifting the control rod on both sides of the upper end of the control rod, and holes near the bases of the arms through which the coolant flows into the gaps between the arms; A magnetic body and an electromagnet arranged at the upper part of each arm of the control rod, an extension shaft connecting the electromagnet and the inside of the drive mechanism of the control rod, a sodium pot provided in the extension shaft, and a sodium pot provided in the extension shaft. 2. The fuel failure detection device for a fast breeder reactor according to claim 1, further comprising the sampling line that passes through the electromagnet and has one end communicating with the sodium pot and the other end communicating with a gap between each arm of the control rod. 3. The control rod is provided with arms for lifting the control rod on both sides of the upper end of the control rod, and holes near the bases of the arms through which the coolant flows into the gaps between the arms; A magnetic body and an electromagnet disposed at the upper part of each arm of the control rod, an extension shaft connecting the electromagnet and the inside of the drive mechanism of the control rod, a sodium pot provided within the extension shaft, and a sodium pot disposed within the extension shaft. penetrate,
2. The fuel failure detection device for a fast breeder reactor according to claim 1, wherein the sampling line has one end connected to the sodium pot and the other end connected to a side surface of the extension shaft. 4. The control rod is provided with arms for lifting the control rod on both sides of the upper end of the control rod, and holes near the bases of the arms through which the coolant flows into the gaps between the arms. A magnetic body and an electromagnet arranged at the upper part of each arm of the control rod, an extension shaft connecting the electromagnet and the inside of the drive mechanism of the control rod, a sodium pot provided in the extension shaft, and a sodium pot provided in the extension shaft. The sampling line passes through the electromagnet and has one end leading to the sodium pot and the other end to a gap between each arm of the control rod, and one end to the sodium pot and the other end to a side surface of the extension shaft. 2. The fuel failure detection device for a fast breeder reactor according to claim 1, further comprising a sampling line consisting of: 5. The control rod is provided with arms for lifting the control rod on both sides of the upper end of the control rod, and holes near the bases of the arms through which the coolant flows into the gaps between the arms. A magnetic body and an electromagnet disposed at the upper part of each arm of the control rod, an extension shaft connecting the electromagnet and the inside of the drive mechanism of the control rod, a sodium pot provided within the extension shaft, and a sodium pot disposed within the extension shaft. penetrate,
One end is provided in the sodium pot and the other end is provided on the side surface of the extension shaft, and the inlet of the other end is provided with the coolant installed facing the coolant rising along the side surface of the extension shaft. The fuel failure detection device for a fast breeder reactor according to claim 1, wherein the sampling line is provided with an intake pipe. 6. The control rod, which is provided with arms for lifting the control rod on both sides of the upper end of the control rod, and holes near the bases of the arms through which the coolant flows into the gaps between the arms; A magnetic body and an electromagnet arranged at the upper part of each arm of the control rod, an extension shaft connecting the electromagnet and the inside of the drive mechanism of the control rod, a sodium pot provided in the extension shaft, and a sodium pot provided in the extension shaft. a sampling line passing through the electromagnet and having one end connected to the sodium pot and the other end communicating with a gap between each arm of the control rod; is provided on a side surface inside the extension shaft, and an inlet of the other end is provided with an intake pipe for the coolant that is attached to face the coolant rising along the side surface of the extension shaft. The fuel failure detection device for a fast breeder reactor according to claim 1, further comprising a sampling line. 7. The fuel failure detection device for a fast breeder reactor according to claim 1, comprising a gripper-type control rod holding device, and the sampling line penetrating the inside of the drive rod of the gripper. 8. The fuel failure detection device for a fast breeder reactor according to claim 1, comprising a gripper-type control rod holding device and the sampling line provided on a side surface of the drive rod of the gripper. 9. In a fuel failure detection device for a fast breeder reactor that detects fuel failure by measuring nuclear fission products present in the coolant, each of the control rod lifting arms provided on both sides of the upper end of the control rod; The control rod is provided with holes near the base of each arm through which the coolant flows into the gaps between the arms, and a magnetic body and an electromagnet are disposed at the upper part of each arm of the control rod. , an extension shaft located directly above the electromagnet, whose lower end is connected to the electromagnet and whose upper end is fixed with a shielding plug; A fuel failure detection device for a fast breeder reactor, comprising: a sodium flow pipe passing through the extension shaft to reach a radiation measuring device, the radiation measuring device, and a sodium return pipe.