JPS5822996B2 - A device that detects leaks in the cladding of fuel rods located inside the pressure vessel of a nuclear reactor. - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a detection system for detecting leaks in the cladding of fuel rods located in a nuclear reactor pressure vessel in which the pressure vessel cover has been removed and water radiation protection has been established. The apparatus includes a plurality of fuel assemblies in the pressure vessel and a plurality of fuel rods in each fuel assembly, the fuel assemblies being positioned at their upper ends by a core grid, and the sensing The apparatus includes a test hood, the test hood having a lower end resting on the soil of the portion of the core grid and in hydraulic communication with the fuel assemblies belonging to the portion of the core grid; The device further relates to a sensing device in which there is a water transport device adapted to transport the water contained in the fuel assembly to a water separator arranged above the radiation-protecting water.

A detection device of the above type is known from Japanese Patent Application Laid-Open No. 48-14995.

In known detection devices, the investigation of leaks in the cladding of a fuel rod is carried out by interrupting the flow of cooling water in the fuel assembly to be inspected.

In these fuel assemblies, the interruption of cooling water causes a temperature increase that causes fission gas to be expelled from the leaking fuel rod, and this gas to accommodate one or more leaking fuel rods. It dissolves in the water enclosed in the fuel assembly.

Fuel assemblies such as MiJ can be detected by sampling water from multiple fuel assemblies.

Each sample of water is taken from a corresponding fuel assembly by a suction tube and sent to a corresponding sump.

Each glass pan is made of a material that can absorb and concentrate certain fission products.

Once the water in each sample of water has flowed through its corresponding vial, the vials are manually removed and manually inserted into a gamma scanner in which the vials are removed. The radioactivity of the contents is measured.

These known sensing devices have the disadvantage of requiring special protective equipment.

The reason for this is that there is always a possibility that at least one of the glass bottles has strong radioactivity, so all glass bottles must be treated as objects that emit radioactivity.

These protection devices complicate the detection equipment and its operation, and also prolong the time required for inspection.

Furthermore, inert gases are almost impossible to detect.

The known detector devices are intended for the absorption and concentration of iodine.

Filters can efficiently absorb iodine, but they cannot absorb inert gases dissolved in water.

Fission products produced in fuel rods during normal operation are
It consists of iodine gas and almost the same amount of inert dregs as the iodine gas.

However, since iodine readily chemically combines with the homogeneous material of the fuel rod, it can be assumed that the gases that collect within the fuel rod confinements are primarily inert gases.

One advantage of the present invention is that the above-mentioned protection device can be virtually eliminated, and that inspection of fuel assemblies in the pressure vessel of a nuclear reactor can be carried out quickly and with great sensitivity. The object of the present invention is to further develop known detection devices.

The features of the invention are as described in the claims, and the invention will now be described with reference to the accompanying drawings.

In the figure, 1 indicates the pressure vessel in the reactor, 2 indicates the core grid of the reactor, and 3 indicates the positioning at a desired position on the core grid by an extendable grip 4 attached to a workbench 5. A suction hood or test hood is shown.

The suction hood 3 stands on the core grid by guide legs 3γ.

A bundle 6 of liquid 1t=cable and electric cable is suspended as a rope γ, and connects the suction hood 1-'3 with a plurality of operation cabinets 8 provided in the apparatus.

Above the pressure vessel 1, there is a certain amount of water 61 that protects against radiation.

The suction hood 3 shown in FIG. 2 consists of four structural units ( (hereinafter referred to as food composition unit)9
, each component 9 having a unit 10 constituting a corresponding gripping device.

Each unit 10 of the gripping device has a plurality of gripping arms 10' oriented approximately vertically, which gripping arms can be inserted into the upper part of the casing of the fuel assembly.

The lowermost part of the gripping arm 10' can be forced to swing horizontally by means of the actuating bar 14, so that it can be brought into engagement with a corresponding opening in the casing of the fuel assembly.

The mechanical connection between the component 10 of the gripping device and the fuel assembly can be secured by moving the operating rod 14 in one vertical direction and released by moving the operating rod 14 in the other vertical direction. I can do it.

The above-mentioned movement of the operating rod 14 can be effected by means of four gripping cylinders 15 which are moved by compressed air.

Each cylinder 15 has a piston (not shown) that is mechanically coupled to a corresponding operating rod 14 .

The four cylinders 12, which are moved vertically by compressed air, are attached at their F ends to the top of the suction hood 3, and at their upper ends are seated on an elongated force transmitting member 3'. is equipped with a hanging ring 18 for the extendable grip 4 at its upper end.

Each of the cylinders 12, which are moved in the vertical force direction by said compressed air, is provided with a piston (not shown) and a hollow piston rod 13, which extends vertically through the cylinder 12. There is.

One end of the hollow piston rod 13 is the component 10 of the gripping device.
is rigidly connected to the outer part of and thus to the component 10, so that the fuel assembly 20 can be lifted by a cylinder 12 operated with compressed air.

The above-mentioned operating rod 14 is coaxially arranged inside the hollow piston rod 13, and the gripping cylinder 15 is supported by the piston rod 13 and attached to the upper end of the piston rod 13.

The piston rod 13 and the operating rod 14 are provided with electrically actuated level indicators 16 and 17, respectively, at their upper ends.

Dashed line 19 indicates the upper edge of the fuel assembly in the initial position, while 20 indicates the fuel assembly in the test position.

The banking ring 22 is compressed between the two flanges 21 and 23, and when the fuel assembly 20 is lifted to its test position by the corresponding compressed air actuated cylinder 12, the fuel assembly The sealing of the casing of the body 20 is ensured, so that a hydraulic connection is established between said casing and the corresponding component 9 of the hood.

Compressed air is then supplied to the water-filled hood component 9, so that a certain amount of water is drained, i.e. forced through the end of the fuel assembly and This creates an air cushion surrounded by the hood unit 9.

This air cushion prevents water circulation through the raised fuel assembly.

However, if the hydraulic connection between the hood component 9 and the corresponding fuel assembly casing is so tight that substantially no water can flow through the fuel assembly. , the air cushion described above can be dispensed with.

If the flow of water through the fuel assembly is interrupted for any period of time, natural collapse forces will increase the temperature within the fuel assembly.

If the cladding of any of the fuel rods in a fuel assembly were to leak, fission ganuses could pass through the damaged cladding wall and dissolve into the stagnant, immobile water of the fuel assembly. Probably.

If the gas content of this stationary water is to be tested, it is preferable to vent the air enclosed in the hood component 9 - if present.

A particular working ganu is then circulated in a closed circuit through the stationary water marked υ1■.

The equipment required for this process is described below with reference to FIGS. 3 and 4.

The hood 3 includes a flange 24 and a lid 5 that seals the flange.

The lid 25 has an opening 26 to which the hose 2γ is connected.

The opening 26 communicates via a passage 28 formed in the flange 24 and extending horizontally along the lid 25 into the space surrounded by the component 9 of the hood.

A nozzle 29 is attached to the flange 24 and is arranged substantially coaxially with the opening 26 in the lid.

The nozzle 29 is connected to a compressed air hose 30, which communicates via a valve 32 to the high pressure side of an air compressor 31.

When valve 32 is opened, compressed air is ejected through nozzle 29 which, together with horizontally extending passage 28 and hose 21, acts as an air lift pump.

The mixture of water and Ganu passes through the hose 2γ and collects in a water separator 33 located in the operating cabinet 8 close to the surface of the water 61, which protects against radiation.

From the hose 21, the working scum with the addition of possible fission ganuses passes through a water separator 33 to a measuring chamber 34 intended for the measurement of radioactivity in the gas, and then passes through this chamber further to an air compressor 31. is pumped to the low pressure side of the gas circuit, completing all of the circulation within the gas circulation system.

Furthermore, there is a connection part for a sample bottle 35 for Ganu analysis and a connection part for a sample bottle 36 for water analysis.

The working gas is returned from the measurement chamber 34 to the air compressor 31.

If the air cushion is used as a device for interrupting the water circulation, it is of course possible to provide each of the components 9 of the hood with a specific air cushion for the above purpose, but during the final water absorption It is also possible to use the same openings used to supply the water collected in the water separator 33 by the pump to the near rift 1.

According to FIG.
This means that γ is used.

However, during the final water intake, a two-stage valve (two-
stage va Ive ) 32 should not be located at the position shown in FIG. 2, but at another position,
This means that a compressed gas container 38, e.g.
This means that it is supplied from the suction foot 3 to the suction foot 3.

The contact between the water and the working gas becomes very effective by producing the effect of an air lift pump.

In addition to this, the water is subjected to a significant pressure reduction during its movement.

This means that fission gases dissolved in water will easily dissipate.

The action of the pump is based on the same pump enclosed in a sealed system.
O is always carried out by an actuating force in the amount of

[Brief Description of the Drawings] Figure 1 is a vertical sectional view showing the soil section of a nuclear reactor where leakage detection is being carried out by the device of the present invention; A vertical sectional view of part of the device according to the invention and a schematic representation of other parts of the detection device; FIG. The figure shown in Fig. 4 is a 1' @ side view taken along the line IV-IV in Fig. 3. 1... Pressure vessel, 2... Core grid, 3. ... Suction hood, 4 ... Telescopic grip, 5 ... Workbench, 6 ... Bunch,
γ...Lobe, 8-...Operation cabinet, 9--...Constituent unit of two 1', 10...
・Constituent unit of gripping device, 26, 2γ, 29...
・Near lit pump, 31...Pongee machine for waste, 3
3...Water separator, 34...Measurement chamber.

Claims (1)

[Scope of Claims] 1. A detection device for detecting leakage in the cladding of a fuel rod placed in a pressure vessel of a nuclear reactor in which the cover of the pressure vessel has been removed and radiation protection from water has been established. ,
The pressure vessel has a plurality of fuel assemblies, each fuel assembly has a plurality of fuel rods, and the fuel assemblies are positioned by the core grid 2 at their -F ends. , the detection device has a test hood 3, the lower end of which is placed on the soil of a part of the core grid, and the part of the core grids 1 to ′ (・′1) is connected to the fuel assembly to which it belongs. The sensing device 1 further transports the water contained in the fuel assembly to a water separator disposed in the radiation-protecting water tank. 1) - In a certain detection device such as a black water ring device, the water device was added to the test 7 test food 3. 29, the air lift pump's gas nozzle 29 is connected to the two sides of the gas compressor 31, and a measurement chamber 34 for measuring radioactivity is connected to the water separator 33 of the gas compressor 31. The gas compressor 3
1. A detection device characterized in that the detection device is connected to the low pressure side of the battery. 2. The detection device according to claim 1, wherein the test hood 3 has a flange 24 disposed at the -L end thereof, and a cover disposed in mechanical contact with this flange. 25, and a horizontally extending passageway 28 is disposed between the flange 24 and the cover 25, and the passageway communicates with the interior of the test node; Further, the entry nozzle 29 of the air lift pump is fitted over the flange 24 and arranged so as to cross the front passage 28 and share an axis with the hole 26 provided in the cover 25. A detection device characterized in that a horn 21 is arranged to connect the hole and the water separator 33. 3. In the detection device according to claim 1, the test tool l-' 3 comprises several hood structural units 9.
What is claimed is: 1. A detection device characterized in that each hood component unit is paired with a corresponding fuel assembly. 4. In the arrow inspection apparatus described in claim 1, a test hood 3 is attached to the wall of the test 1@hood and is configured to seal around several fuel assemblies. A detection device characterized in that it is equipped with a banking blade ring 22.