JPH0875894A - Burnup of spent fuel measuring facility - Google Patents

Abstract

PURPOSE: To make maintenance and inspection work easy by installing a water gate between a first pool to store spent fuel and a second pool communicated with the first pool and installed in a burnup measuring facility. CONSTITUTION: At the time of a normal burnup measurement, a water gate 4 is opened and a spent fuel assembly 5 is moved to a burnup measuring pit from a fuel temporarily storing pit and further put in an operation part 7 by a crane 15 and the radiation intensity is measured by radiation detectors 10, 14 and burnup, remaining concentration, etc., are examined. Then, at the time of maintenance and inspection of the fuel burnup measuring facility, at first the water gate 4 is closed and a drain hole 9 is opened to discharge water in a burnup measuring pit 3, so that clads adhering to the operation part 7 due to water discharge are cleaned. On the completion of the cleaning, an operator for maintenance and inspection enters the pit 3 and carries out maintenance and inspection work for the driving part of the operation part 7, the detector 10, the burnup measuring facility, and other parts. After the maintenance and inspection work is finished, water is poured to the pit 3 and when the water level becomes the same as that of the temporarily storing pit, the water gate 4 is opened and thus an assembly 5 can be transported to the operation part 7 from the temporarily storing pit.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spent fuel burnup measuring facility provided in a spent fuel receiving facility or a storage facility in a nuclear power plant or a nuclear fuel reprocessing plant.

[0002]

2. Description of the Related Art Spent fuel from a nuclear power plant or the like is stored or carried out after being subjected to various measurements by a burnup measuring facility provided in a facility for receiving or storing the spent fuel.

This burnup measuring facility derives burnup, residual enrichment, etc. of a spent fuel assembly from radiation measurement values of the fuel assembly, and various measurement results are used to judge whether fuel can be accepted or not, and to store it. It is used for criticality control and confirmation of burnup in the shearing-melting process.

FIG. 3 is a plan view showing the structure of a conventional spent fuel burnup measurement facility provided in a facility for receiving or storing spent fuel, and FIG. 4 is a detailed view of the conventional burnup measurement facility. It is a side cross-sectional view showing another configuration.

In FIG. 3, the spent fuel burnup measuring facility is installed in a burnup measuring pit 32 which is continuously connected from a fuel temporary storage pit 31 which is a pool filled with water.

In FIG. 4, the spent fuel burnup measurement facility is installed in a burnup measurement pit 32 and has a mechanism portion 35 loaded with a spent fuel assembly 33 and a first radiation detector 34. And a measurement unit 37 that is installed from the first radiation detector 34 via the cable 36 to the outside of the pit 32 for measuring the burnup and that measures a signal from the radiation detector.

The cable 36 also transmits a control signal from a control unit that controls a drive unit in the mechanism unit 35 that moves the fuel assembly 33 to a predetermined measurement position. Furthermore, the spent fuel burnup measurement facility has a pit 32 for burnup measurement.
Collimator 38 embedded in the wall of the
And a second radiation detector 39, which is, for example, a germanium semiconductor detector, which measures the radiation from the spent fuel assembly 33 via the sensor 8.

The depth of the burnup measuring pit 32 in which the mechanism portion 35 is installed is about 15 m. In the spent fuel burnup measurement facility configured as described above, the maintenance and inspection of the mechanism portion 35 should be carried out by lifting the mechanism portion 35 from a pool under water about 15 m by a crane and moving it to the place for maintenance and inspection. Done by After being moved to a place for maintenance / inspection, the deposits from the spent fuel assemblies 33 on the mechanism part 35 such as the clad are decontaminated, and the drive part and the first radiation stored in the mechanism part 35 are decontaminated. The detector 34 is maintained and inspected. After the completion of maintenance and inspection, the mechanism unit 35 is suspended again by the crane and installed in its original position. Here, the clad is a radioactive contaminant that is made of an insoluble metal oxide and mediates various kinds of radioactive migration.

[0009]

However, in the conventional spent fuel burnup measuring facility, the following problems are involved in lifting and lowering the mechanism unit 35 for maintenance and inspection, and for other reasons. Such problems are occurring. (1) It is necessary to lift the mechanism unit 35 from the pool about 15 m under water each time maintenance and inspection are performed, which requires a great deal of labor. (2) The clad or the like adhering to the mechanism portion 35 is removed by washing during or after pulling from water. For this reason, it is necessary to provide a special facility in order to remove it by washing after pulling it up. On the other hand, if the clad is removed in water, there is a risk that the clad will be accumulated in the burnup measurement pit 32 during the measurement of a large number of fuel assemblies and the entire pit 32 will be activated. Further, the clad will drop to some extent when the mechanism portion 35 is lifted up even if it is not actively removed in water. (3) When the mechanism unit 35 is installed again after maintenance and inspection, the alignment between the collimator 38 that focuses the radiation from the spent fuel assembly 33 onto the second radiation detector 39 and the mechanism unit is strictly performed. Need to do. This is the collimator 3
This is because the height direction width of 8 is about 10 mm, and the measurement window of the mechanism unit 35 is also about the same size because the drive unit and the first radiation detector 34 are installed. Therefore, the mechanism unit 35 needs to be installed with high accuracy of positioning accuracy of ± 1 mm or less. However, this is extremely difficult, and it is virtually impossible to secure highly accurate position reproducibility during installation. (4) Mechanical part 35 installed in a pool under water about 15 m
About 50 cables 36 connecting the measurement unit installed outside the pool with the measurement unit need to be uniformly movable so as not to be caught when the mechanism unit 35 is lifted or hung. This is a laborious and difficult task. (5) In addition to the above-mentioned problems, in such a facility, if there is a case where the mechanical unit 35 falls due to a mistake in hoisting the mechanical unit 35, an earthquake, etc. As a result, the fuel assembly temporarily placed in the temporary fuel placement pit 31 may fall or be damaged.

The present invention has been made in view of the above circumstances, and a first object thereof is to maintain and maintain burnup measuring equipment.
It is an object of the present invention to provide a spent fuel burnup measurement facility that does not require the mechanical part to be suspended from underwater at the time of inspection, and the installation position does not change and maintenance and inspection are easy.

A second object of the present invention is to provide a spent fuel burnup measurement facility in which each facility can be easily cleaned. On the other hand, a third object of the present invention is to provide a spent fuel burnup measurement facility that does not affect the floor surface of the temporary fuel storage pit even if the mechanical unit falls over. Furthermore, a fourth object of the present invention is to provide a spent fuel burnup measurement facility that minimizes the accumulation of radioactive materials in the burnup measurement pit.

[0012]

In order to solve the above problems, the invention according to claim 1 relates to a first pool for accommodating spent fuel of a nuclear reactor in water, and to communicate with this first pool. However, the second pool provided with burnup measuring equipment for measuring the burnup of the spent fuel in water, the first pool and the second pool.
It is a spent fuel burnup measurement facility equipped with a sluice provided between the pool and the pool.

According to the second aspect of the invention, a first pool for accommodating the spent fuel of the nuclear reactor in water and the first pool are communicated with each other, and the burnup of the spent fuel is measured underwater. A second pool provided with burnup measuring equipment, a drainage hole provided in the lower part of the second pool, and a sluice provided between the first pool and the second pool. This is the spent fuel burnup measurement facility.

Further, the invention according to claim 3 is the invention according to claim 1 or 2, wherein the sluice is provided between the first pool and the second pool, and from the bottom to the water surface. Is a spent fuel burnup measurement facility in which the spent fuel does not come out of the water when the spent fuel is moved from the first pool to the second pool.

Furthermore, the invention corresponding to claim 4 is
In the invention corresponding to claim 2, the drain hole is a spent fuel burnup measurement facility formed at a lower end of a recess having a tapered surface formed on the bottom surface of the second pool.

[0016]

Therefore, first, in the facility for receiving or storing the spent fuel of the invention according to claim 1, it is possible to separate the first pool and the second pool by the water gate.

Therefore, the sluice is normally open,
The spent fuel is moved from the first pool to the second pool, and the burnup measurement is performed in the second pool having a facility capable of measuring the burnup of the spent fuel in water.

Further, when the facility capable of measuring the burnup of the spent fuel in water is maintained and inspected, the first pool and the second pool are separated by closing the water gate. Then, by draining water from the second pool with, for example, a pump,
A maintenance / inspector can directly enter the second pool after draining water to perform maintenance / inspection of each facility.

Therefore, it is not necessary to suspend a part of the above equipment from the water by a crane for maintenance and inspection. Further, in the facility for receiving or storing the spent fuel of the invention corresponding to claim 2, the same operation as in the invention corresponding to claim 1 is performed, and water is easily drained by the drain hole after the water gate is closed. be able to.

Further, the equipment capable of measuring the burnup of the spent fuel in water can be washed by spraying a liquid or the like from the outside, and the washed liquid or the like can be discharged from the drain hole.

Therefore, the above-mentioned equipment can be easily cleaned and decontaminated. Furthermore, in the facility for receiving or storing spent fuel of the invention according to claim 3, the same operation as the invention according to claim 1 or 2 is performed, and the height from the bottom of the floodgate to the water surface is When moving the spent fuel from the 1st pool to the 2nd pool, the spent fuel is set so that it does not come out of the water, so this height should be set to a level just enough to allow the spent fuel to pass. Even if a part of the burnup measurement equipment should fall down, the effect is hardly transmitted to the first pool.

Therefore, even in such a case, the spent fuel placed in the first pool will not fall or be damaged. Further, in the spent fuel burnup measuring facility of the invention corresponding to claim 4, the drain hole is formed at the lower end of the recess having the tapered surface formed on the bottom surface of the second pool. Therefore, for example, the clad and the like can be easily removed by draining water, and the clad and the like will not be accumulated in the second pool.

[0023]

An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a plan view of the spent fuel burnup measurement facility of this embodiment seen from above, and FIG. 2 is a side sectional view showing the configuration of the spent fuel burnup measurement facility of this embodiment.

In FIG. 1, the spent fuel burnup measuring facility has a temporary fuel storage pit 1 which is a pool filled with water and is connected to a facility for receiving or storing spent fuel (not shown). .

A pit 3 for measuring burnup is provided in the fuel temporary storage pit 1 with a water channel 2 interposed therebetween.
A water gate 4 for partitioning the temporary fuel storage pit 1 and the burnup measurement pit 3 is provided therein.

The floor surface 2a of the water channel 2, that is, the lower end position of the sluice gate 4, is a condition under which the spent fuel assembly 5, which is the object of burnup measurement, can move in water and be carried into the pit 3 for burnup measurement. In, the fuel temporary storage pit 1 is set at a position as high as possible compared to the height of the floor surface.

In FIG. 2, the mechanism portion 7 in the spent fuel burnup measurement facility is the floor surface 6 of the burnup measurement pit 3.
It is fixedly installed on the top. The depth of the burn-up measuring pit 3 in which the mechanism portion 7 is fixedly installed is, for example, about 15 m, a recess 8 having a taper is provided just below the mechanism portion 7 on the floor surface 6, and the water is further provided in the center thereof. A hole 9 is provided.

The mechanical section 7 is constructed so that the fuel assembly 5 can be inserted therein. The drive section (not shown) for positioning the fuel assembly 5 and the ion chamber and neutron detection which must be provided in the vicinity of the fuel assembly. Radiation detector 1 such as a detector
0 is loaded.

A cable 11 for transmitting various measurement data and control signals is connected to the first radiation detector 10 and the drive unit, and the cable 11 is a radiation installed outside the pit 3 for burnup measurement. Is connected to a measuring unit 12 for measuring the value and a drive unit control device (not shown). The measurement unit 12 is further connected to a data processing device (not shown).

Further, as a spent fuel burnup measuring facility, it comprises a collimator 13 embedded in the wall of the pit 3 for burnup measurement, and a germanium semiconductor detector for measuring the radiation focused on the collimator 13, for example. A second radiation detector 14 is provided. The second radiation detector 14 is installed in a measurement room outside the pit, such as the pit 3 for burnup measurement.

On the other hand, the spent fuel burnup measuring facility is provided with a crane 15 for moving the fuel assembly 5. Next, the operation of the spent fuel burnup measurement facility of the present embodiment configured as described above will be described.

First, at the time of normal burnup measurement, the water gate 4 is opened, the spent fuel assembly 5 is moved from the temporary fuel storage pit 1 to the burnup measurement pit 3, and the mechanism portion 7 is moved by the crane 15. Radiation is installed inside the chamber and radiation is measured by the first and second radiation detectors 10 and 14, and burnup, residual enrichment, etc. are investigated. Then, these various measurement results are used for determination of acceptability of fuel, criticality control during storage, confirmation of burnup in the shearing to melting process, and the like.

Next, maintenance and maintenance of the spent fuel burnup measurement facility
The case of inspection will be described. First, the water gate 4 is closed, and then the water drain hole 9 is opened to drain the water from the burnup measurement pit 3.

At this time, the flow of the water discharged in the pit 3 is utilized to wash away the clad adhering to the mechanism portion 7 and discharge it together with the water. Furthermore, water is also sprayed from the outside into the burn-up measuring pit 3 and the mechanism portion 7 to completely remove and clean the clad and the like. Since the tapered recess 8 is provided from the floor surface 6 to the drain hole 9,
The clad and the like are smoothly discharged along the taper.

After the cleaning is completed, the maintenance / inspector enters the pit 3 for measuring the burnup and drives the drive unit provided in the mechanism unit 7, the first radiation detector 10, and the fuel level measuring equipment. Maintain and inspect other parts.

After completion of maintenance and inspection, the drain hole 9 is closed again, and water is injected into the pit 3 for measuring burnup from an external water source. When the water level reaches the same level as the temporary fuel storage pit 1, the water gate is opened so that the fuel assembly 5 can be carried into the mechanism section 7 from the temporary fuel storage pit 1.

The function and effect of the spent fuel burnup measuring facility of this embodiment having the above-mentioned structure will be described. (1) A sluice gate 4 is provided between the temporary fuel storage pit 1 and the burnup measurement pit 3, and a partition is provided between the fuel temporary storage pit 1 and the fuel temporary storage pit 1 regardless of the state of the temporary fuel storage pit 1, for example, by pumping to burn. Since the water can be discharged from the pit 3 for measuring the degree of fuel, the mechanism 7 remains fixed, and the weight of the crane is about 2 to 3 every time the maintenance and inspection of the burnup measuring equipment is performed.
There is no need to lift and suspend the ton mechanism section 7, which facilitates maintenance and inspection.

Further, since the mechanical section 7 can be maintained and inspected in a state of being installed, the maintenance and inspection equipment of the mechanical section 7 which has been conventionally provided is unnecessary. Further, since the cable 11 connecting the mechanism unit 7 and the measuring unit 12 does not need to be moved, a cable that is lower in cost than the conventional one based on lifting and hanging can be used.

Further, since the mechanical section 7 is fixedly installed, high-precision positioning among the mechanical section 7-collimator 13-germanium semiconductor detector 14 can always be ensured, and measurement with good reproducibility can be performed. (2) Further, the drainage hole 9 is provided in the floor surface 6 of the burnup measurement pit 3 so that the water in the burnup measurement pit 3 can be drained from the bottom without moving the mechanism portion 7. The mechanical part 7 and other equipment can be washed when draining water.
Furthermore, by spraying water, the clad and the like can be removed more efficiently and the water can be discharged from the water drain hole 9. (3) Furthermore, the height from the bottom of the sluice gate 4 to the water surface is set to a range where the spent fuel does not come out of the water when the spent fuel is moved from the first pool to the second pool. For example, if the height is set to a height just enough to allow spent fuel to pass, for example, the floor surface 2a of the water channel 2
If the position is set higher than the upper end of the mechanism unit 7, even if the mechanism unit 7 should fall down, the influence thereof is hardly transmitted to the temporary fuel storage pit 1.

Therefore, the fuel assembly temporarily placed in the temporary fuel placement pit 31 is hardly fallen over or damaged. (4) Furthermore, from the floor surface 6 to the drain hole 9,
Since the tapered recess 8 is provided, the clad and the like are smoothly discharged along the taper. Therefore, it is possible to prevent the clad or the like from accumulating in the pit 3 for burnup measurement as much as possible.

In the above embodiment, the floor of the water channel 2 is located at a position where the fuel assembly 5 can move in water and be carried into the pit 3 for burnup measurement, and the fuel temporary storage pit 1 It was installed at a position as high as possible compared to the floor height of. However, the water channel 2 or the water gate 4 is not limited to such a configuration. Further, other modified examples can be considered for the drain hole and the like.

For example, (a) The water channel 2 is not provided, and the temporary fuel storage pit 1 and the burnup measurement pit 3 are directly connected, and the water gate 4 is provided between them.
May be provided. This simplifies the structure. (B) The width of the water channel 2 and the water gate 4 is set to a width at which the fuel assembly 5 can pass. At this time, the mechanism portion 7 becomes more difficult to fall down, and the influence caused by the occurrence of the burnup measurement pit 3 side is further difficult to be transmitted to the fuel temporary storage pit 1 side. (C) Plural drain holes 9 and tapered recesses 8 may be received. Further, the shape of the recess 8 may be curved. In addition, the present invention can be modified in various ways without departing from the scope of the invention.

[0043]

As described above, the present invention has the following effects. The invention of claim 1 makes it unnecessary to hang and suspend the mechanism part from the water during maintenance and inspection,
In addition, it is possible to provide a spent fuel burnup measurement facility that can be easily maintained and inspected without changing the installation position.

The invention according to claim 2 can provide a spent fuel burnup measuring facility having burnup measuring equipment which makes it easy to clean each equipment. The invention according to claim 3 can provide a spent fuel burnup measurement facility that does not affect the floor surface of the temporary fuel storage pit even if the mechanism unit falls over. The invention of claim 4 can provide a spent fuel burnup measurement facility that minimizes the accumulation of radioactive substances in the burnup measurement pit.

[Brief description of drawings]

FIG. 1 is a plan view of a spent fuel burnup measurement facility according to an embodiment of the present invention as seen from above.

FIG. 2 is a side sectional view showing a configuration of a spent fuel burnup measurement facility of the same embodiment.

FIG. 3 is a plan view showing the configuration of a conventional spent fuel burnup measurement facility.

FIG. 4 is a side sectional view showing a detailed configuration of a conventional spent fuel burnup measurement facility.

[Explanation of symbols]

1 ... Fuel temporary storage pit, 3 ... Burnup measurement pit, 4
... water gate, 5 ... fuel assembly, 7 ... mechanical part, 9 ... drainage hole,
11 ... Cable.

Claims (4)

[Claims] 1. A first pool for accommodating spent fuel of a nuclear reactor in water, and a burnup measuring facility communicating with the first pool for measuring the burnup of the spent fuel in water are provided. A spent fuel burnup measurement facility, comprising: a second pool; and a sluice provided between the first pool and the second pool. 2. A first pool for accommodating spent fuel of a nuclear reactor in water, and a burnup measuring facility for communicating the burnup of the spent fuel in water, which is connected to the first pool. A second pool, a drainage hole provided in a lower portion of the second pool, and a sluice provided between the first pool and the second pool. Used fuel burnup measurement facility. 3. The sluice is provided between the first pool and the second pool, and the height from the bottom to the water surface is changed from the first pool to the second pool. The spent fuel burnup measuring facility according to claim 1 or 2, wherein the spent fuel is set in a range such that the spent fuel does not come out of the water when the spent fuel is moved. 4. The spent fuel combustion according to claim 1, wherein the drain hole is formed at a lower end of a recess having a tapered surface formed on the bottom surface of the second pool. Degree measurement facility.