JPH07122680B2 - Main structure of continuous reactor for nuclear fuel - Google Patents

Description

TECHNICAL FIELD The present invention relates to a continuous melting and treating apparatus for spent nuclear fuel,
In particular, the present invention relates to a main body structure of a nuclear fuel continuous dissolution treatment apparatus suitable for improving airtightness inside a dissolution tank.

[Conventional technology]

Generally, spent nuclear fuel melting treatment apparatuses can be roughly classified into three types: (i) batch type melting apparatus, (ii) semi-continuous melting apparatus, and (iii) continuous melting apparatus.

However, in the batch type dissolution apparatus of the above (i), the dissolution apparatus holding the dissolution solution is loaded with one batch of shear fragments and dissolved, and after the dissolution is completed, the dissolution solution is extracted and the coating material (hull) is rinsed, The operation is completed by taking it out from the melting device. The feature of this device is that the structure of the device is simple, but on the other hand, there is a drawback that the device becomes large for its capacity.

On the other hand, in the semi-continuous dissolution apparatus (ii), a shear fragment is loaded at a constant rate on the dissolution apparatus holding the dissolution solution, and at the same time, the dissolution solution is replaced with a new dissolution solution and discharged to remove one fragment of the previous fragment. After the loading is completed and the melting is completed, the hull is rinsed, taken out from the melting device, and the operation is finished. The advantage of this apparatus is that the apparatus has a more complicated structure than the batch-type dissolving apparatus, but can be downsized.

Further, in the continuous dissolution apparatus of (iii) above, the sheared fragment and the dissolution liquid are continuously loaded into the dissolution device, and the dissolution liquid and the hull are continuously taken out. This device has an advantage that it is possible to prevent a rapid dissolution reaction at the initial stage of dissolution that is seen in a batch system, and to make the device more compact.

By the way, a conventional example of this continuous melting apparatus is disclosed in Japanese Patent Publication No. 60-41318. There is known a continuous treatment device for treating substances in a corrosive liquid. This apparatus uses an upright annular vessel, and arranges a plurality of nuclear fuel-loaded cages along the inner circumference of the vessel and sequentially rotates them in one direction so that the cages below are immersed in the dissolution treatment solution.

[Problems to be Solved by the Invention]

However, in the conventional continuous melting apparatus configured as described above, when driving, contact between the metal parts of the drive part occurs in the solution (nitric acid), and as a result, the drive part is corroded. Moreover, since it has been an upright type in the past, it is disadvantageous in terms of earthquake resistance.

Incidentally, the continuous dissolution apparatus described in JP-A-61-169798,
Due to lack of consideration for demonstrable corrosive treatment solution, the drive part is exposed to the atmosphere of corrosive treatment solution, and the gasket inside and outside of the annular container is hermetically sealed. There was a risk of leaking out of the container.

The present invention has been made in view of the above-mentioned problems, and it is possible to reliably prevent the drive unit from coming into contact with the atmosphere of the volatile corrosive treatment solution, and the corrosive gas may leak out of the container. It is an object of the present invention to provide a main body structure of a nuclear fuel continuous melting apparatus which is excellent in safety and maintenance.

[Means for Solving the Problems]

In order to achieve the above-mentioned object, the present invention holds a corrosive dissolution treatment solution, and a plurality of annular wall-shaped suspension plates driven and supported by rollers inside a horizontal annular container having an upper lid on the top. While arranging individual nuclear fuel loaded cars in a suspended manner, and immersing a fixed height of the car on which the nuclear fuel is mounted in the dissolution treatment solution, the cars are sequentially moved in one direction by circular movement of the suspension plate. In the main body structure of the nuclear fuel continuous melting apparatus for moving the nuclear fuel to dissolve the nuclear fuel, between the lower portion of the suspension plate and the annular container, and
First and second movable airtight suspension plates are provided between the upper portion of the suspension plate and the upper lid, respectively, while maintaining airtightness.
The water seal is provided, and at the contact portion with the upper lid on the inner peripheral side and outer peripheral side of the annular container, a concave portion is fitted on the annular container side and a convex portion is fitted on the upper lid side. Third and fourth portions that are provided with air-tightness on the inner peripheral side and the outer peripheral side respectively.
Water seal is provided, and the upper lid that closes the upper portion of the annular container has an integral structure, and the bolt tightening and fixing portion of the annular container and the upper lid is provided on the outer peripheral side of the fourth water seal. It is characterized by that.

[Action]

According to the above configuration, since the suspension plate that moves by suspending the nuclear fuel-loaded basket retains airtightness, the roller that drives and supports the suspension plate is airtightly isolated from the atmosphere of the corrosive solution. It is possible to prevent wear and damage of the roller. Further, between the inside and the outside of the annular container is double-sealed by the first and second water seals of the hanging plate and the fourth water seal on the outer peripheral side of the annular container, so that the airtightness is more maintained. The structure is further improved because the height of the unevenness of the seal portion can be alleviated as well as further improved. In addition, the airtightness can be easily maintained by the integral structure of the upper lid, and by making the bolt tightening and fixing portion of the upper lid the outermost periphery, it is advantageous to prevent the corrosion of the bolt portion and to maintain the airtightness.

〔Example〕

The present invention will be described in detail below with reference to the embodiments shown in the drawings.

FIG. 1 is an overall configuration diagram showing an embodiment of a nuclear fuel continuous dissolution treatment apparatus according to the present invention, FIG. 2 is an enlarged cross-sectional view of an essential part of a main body of the apparatus of FIG. 1, and FIG. 3 is of FIG. It is a principal part expansion perspective view of the main-body part of an apparatus. The horizontal annular container 1 is filled with a liquid level 4 at a level at which nitric acid as a solution 3 is present. Fuel-loading basket 2 for loading spent fuel shears 8
Is suspended on a fuel-carrying car suspension plate 14 so that it can be immersed in the solution 3 up to a certain height. This hanging plate 14
Is supported by the hanging plate support roller 15, and the arrow y
Is configured to rotate in a direction. In the annular vessel 1, the FP (fission products) and nitric acid, which are active, come out in the gas phase due to the dissolution of the fuel by the solution 3 which is nitric acid, so that the upper lid 5 is sealed. There is. This top lid 5
Is fixed to the annular container 1 with bolts 6,
Negative pressure is applied inside the container to prevent nitric acid from leaking to the outside.

Here, in order to further increase the airtightness, the water seal 16,17
To use. Further, in order to prevent mechanical parts such as the hanging plate supporting roller 15 from being corroded or deteriorated in a nitric acid atmosphere,
A roller protection water seal 18 is used. At this time, it is not necessary to increase the pressure difference between the inside (driving portion) and the outside of the fuel-loaded car suspension plate 14. That is, the water seals 16 and 17 are present even if the differential pressure is small. Therefore, if the pressure is 10 to 20 mmHg, the water seal for roller protection 18
The height of the uneven portion of about 10 cm is enough to maintain the differential pressure. The pressure difference between the inside and outside of the annular container 1 may reach around 100 mmHg, so the inner water seal 16 is necessary, and the outer water seal 17 has a height of 20 cm.
It is enough.

The water seals 16, 17, 18 are replenished with water by the water replenishing pipe 19 so that the sealed portions are immersed in the water 20, and therefore, long-term operation is also possible.

A plurality of fuel-loaded cages 2 having the same shape are loaded inside the annular container 1, and a spent fuel shearing piece 8 is loaded into the cage 2. There is. The fuel loaded car 2 is held by a fuel loaded car suspension plate 14, the suspension plate 14 is supported by a suspension plate support roller 15, and is configured to rotate counterclockwise by a rotation drive device. However, the spent fuel dissolves in the solution 3 and the dissolved fuel-loaded basket 2
Is configured to stop at a portion of the annular container 1 where the fuel loading car extraction door 10 is located. Here, the take-out door 10 is opened, the fuel-loaded car 2 is taken out from the solution 3 into the cleaning chamber 21 by the lifting device 9, and then the take-out door 10 is closed again.
In the cleaning chamber 21, the spray nozzle 11 sprays water to clean the fuel-loaded car 2. Further, the washed fuel-loaded car 2 is carried out of the continuous dissolution processing device by the carry-in / carry-out device 12, and the hull is discarded in the hull collection container 13.

By the way, in the melting apparatus, in order to dissolve the spent fuel, the shear pieces 8 of the fuel rod are loaded and melted by the dissolving liquid (nitric acid) 3. Most of the radioactivity of spent fuel is FP
Since it is a fission product and has an order of 10 ⁶ ci / t even after about 1 year has passed since the reactor was taken out, the radioactivity level inside the device is extremely high and it is negative so that FP does not leak outside. Keep pressure. Therefore, if the airtightness is poor, air will enter from the outside, and the load on the exhaust equipment in the apparatus will be significantly increased.

Therefore, if the upper lid of the main body of the apparatus is configured to be separable, more parts will be sealed when assembled and the airtightness will deteriorate.
Therefore, if the upper lid 5 is formed into an integrated structure as in the present embodiment, the portion requiring sealing is limited to the contact portion between the annular container 1 and the upper lid 5, and the airtightness can be easily maintained. Even during maintenance, it requires a larger work space than the split type, but on the other hand, work efficiency is improved.

Also, since it is highly corrosive in a nitric acid atmosphere, in order to maintain airtightness, the seal must be resistant to high radioactivity, corrosion and thermal deformation, and easy to maintain. Therefore, the solid seal made of polymer resin, rubber or the like is not easy to replace when it is broken or deteriorated, which increases the amount of radioactive solid waste generated.

On the other hand, the water seal is structurally easy to use if the decompression inside the melting device is around 100 mmHg, has radiation resistance and corrosion resistance, and since it is liquid, there is no possibility of damage and deterioration like a solid seal, It is also possible to seal the moving parts. Also,
Maintenance is easy, and if water is supplied through the supply pipe 19, it has the effect that it can withstand long-term use.

In addition, the present invention equipment adopts the horizontal annular container 1, which is a so-called horizontal type as compared with the conventional upright type.
It has a structure that is advantageous in terms of earthquake resistance.

〔The invention's effect〕

As described above, according to the structure of the main body of the nuclear fuel continuous melting apparatus of the present invention, the assembly of the hanging plate of the moving nuclear fuel loading basket with the annular container and the upper lid is sealed, so that the drive unit is It is possible to reliably prevent contact with the atmosphere of the corrosive treatment solution, and because the seal between the inside and outside of the annular container is doubled, it is possible to prevent leakage of corrosive gas to the outside of the container, and safety and It has an excellent effect that the main body structure of the nuclear fuel continuous melting apparatus excellent in maintenance can be provided.

[Brief description of drawings]

FIG. 1 is an overall configuration diagram showing an embodiment of a nuclear fuel continuous dissolution treatment apparatus according to the present invention, FIG. 2 is an enlarged cross-sectional view of an essential part of a main body of the apparatus of FIG. 1, and FIG. 3 is of FIG. It is a principal part expansion perspective view of the main-body part of an apparatus. 1 ... Annular container, 2 ... Fuel loading basket, 3 ... Dissolved liquid,
5 ... Top lid, 9 ... Lifting device, 10 ... Extraction door, 14 ...
Fuel loading basket suspension plate, 16,17,18 …… Water seal, 19 ……
Water supply piping.

Claims (1)

[Claims] 1. A plurality of nuclear fuel loading baskets are mounted on an annular wall-shaped hanging plate which is driven and supported by rollers inside a horizontal annular container which holds a corrosive dissolution treatment liquid and has an upper lid on the upper part thereof. While suspending and arranging, while immersing a certain height of the car loaded with the nuclear fuel in the dissolution treatment liquid, the annular movement of the suspension plate sequentially moves the car in one direction to dissolve the nuclear fuel. In the main body structure of the nuclear fuel continuous melting apparatus, the suspension is performed while maintaining airtightness between the lower portion of the suspension plate and the annular container and between the upper portion of the suspension plate and the upper lid. The first and second water seals in which the lower plate is movable are provided, and a contact portion with the upper lid on the inner peripheral side and the outer peripheral side of the annular container has a concave portion on the annular container side, and A convex portion that fits into the concave portion on the upper lid side The third and fourth water seals that maintain airtightness are provided on the respective concave and convex portions on the inner peripheral side and the outer peripheral side, and the upper lid that closes the upper portion of the annular container is integrally structured, A main body structure of a nuclear fuel continuous melting apparatus, characterized in that a bolted fixing portion between the annular container and the upper lid is provided on the outer peripheral side of the fourth water seal.