JPH0685841B2 - Corrosive solution evaporator - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a corrosive solution evaporator, and in particular, it is used for maintenance in a high radiation environment such as a nuclear fuel reprocessing facility. The present invention relates to a corrosive solution evaporator that is required to be free and have a long life.

[Conventional technology]

As described in JP-A-58-36601, a conventional device is an inner tube type in which a heat transfer tube is immersed in a can liquid of an evaporator heating unit, or an evaporator heating unit is covered with a jacket, and heating fluid is put in the jacket. It was a jacket type that shed. Since all of these heat the can solution through the metal heat transfer surface, when the can solution is a corrosive fluid, the heat transfer surface was subjected to severe corrosive conditions. Further, since the can liquid is heated through the metal heat transfer surface, the scale easily adheres to the heat transfer surface, and the adhered scale remarkably lowers the heat transfer efficiency. Therefore, the scale removal maintenance is required.

[Problems to be Solved by the Invention]

In the above-mentioned conventional technique, no consideration was given to maintenance-free and long life. In particular, when used in a severe environment such as high radiation such as a high-level waste liquid evaporator in a nuclear fuel reprocessing facility, maintenance is difficult and high reliability is required. Only an evaporator that is insufficient in terms of maintainability was obtained.

An object of the present invention is to provide a corrosive solution evaporation method and an evaporation can which do not use a general metal heat transfer surface which is the most problematic in terms of corrosion conditions and scale adhesion.

[Means for Solving the Problems]

The present invention, in order to achieve the above object, in a corrosive solution evaporation can consisting of a heating unit for heating and evaporating a corrosive solution, and a fractionating tower for fractionating steam vaporized by heating in the heating unit, Provide a partition plate along the inside of the can wall of the heating unit,
An opening of a can liquid introducing pipe for introducing the solution from the outside is provided between the partition plate and the can wall, and the solution introduced between the can wall and the partition plate from the opening is While flowing into the can from below the partition plate, a window is provided in a portion of the heating unit upper portion which does not come into contact with the solution, and a laser oscillator for irradiating the solution with laser light to heat the solution is provided. To do.

Further, an optical system such as a reflecting mirror is provided between the laser oscillator and the window. Further, a reflecting plate that reflects the laser light incident on the solution may be provided in the solution.

[Action]

According to the above configuration, the high temperature corrosive can liquid heated by the laser beam is directly applied to the can wall by the partition plate and the solution continuously introduced from the outside between the can wall and the partition plate. Since they do not come into contact with each other, the can wall is kept at a relatively low temperature and the corrosion condition of the can wall is eased, so that the life of the evaporator can be extended. In this case, even if some scale is attached to the partition plate or a pinhole or the like is generated, it is not the can wall itself, so that no adverse effect on the outside occurs. Further, the laser oscillator emits visible to infrared laser light. The emitted laser light enters the evaporator through a window provided in a portion of the evaporator heating unit that does not come into contact with the can, and heats the can. By doing so, since the solution is directly heated without passing through the metal heat transfer surface, it is possible to eliminate the metal heat transfer surface that comes into contact with the hot corrosive can solution and is placed under severe corrosive conditions. In addition, as in the conventional case, when the can liquid is heated through the metal heat transfer surface, scale adheres to the heat transfer surface due to precipitation of the can liquid component or adhesion of insoluble components in the can liquid. However, maintenance was required to remove this, but the entire metal heat transfer surface disappeared, and scale removal became unnecessary.

Furthermore, if a reflecting mirror is installed between the evaporation can and the laser oscillator, the laser oscillator, which is considered to require the most maintenance, can be separated from the evaporation can main body and placed at a place where the maintenance is easy. Further, when the solution is transparent, the efficiency of heating and evaporation can be improved by installing a reflecting plate that makes the laser beam reciprocate a plurality of times in the solution.

〔Example〕

Next, one embodiment of the present invention will be described with reference to FIG. 1, taking as an example the case where the present invention is applied to a high-level waste liquid evaporator in a nuclear fuel reprocessing facility.

In a kettle-type high-level waste liquid evaporation can consisting of the heating unit 1 and the fractionating tower 2, a portion of the heating unit upper part that does not come into contact with the can liquid,
A window 4 made of quartz glass having high transparency and little energy absorption is provided. The reflecting mirror 5 and the EDL laser oscillator 3 are arranged so that the laser light enters the can through the window 4. EDL
The laser oscillator 3 is installed in the laser oscillator cell 7 that can be isolated from the cell 8 in which the high-level waste can is installed by the shield door 6 during maintenance, while avoiding the primary radiation from the high-level waste in the high-level waste evaporator during normal use. To do.

The present embodiment having the above-mentioned configuration operates as follows.

The high-level waste liquid that is the can liquid is emitted from the EDL laser oscillator 3, changes its direction by the reflecting mirror 5, and is irradiated with laser light that enters the can from the quartz glass window 4 without passing through the metal heat transfer surface. Directly heated by contact.

The EDL laser oscillator 3 is installed in the laser oscillator cell 7 by separating it from the high-level waste liquid evaporator having a high radiation dose rate by using the reflecting mirror 5, and is used in an optical system or electronic circuit having low radiation resistance during normal use. Avoid exposure to primary radiation. Further, at the time of maintenance of the EDL laser oscillator 3, the shielding door 6 is closed to isolate the laser oscillator cell 7 from the cell 8 in which the high-level waste liquid evaporating can is installed to block radiation and enhance the safety during maintenance. ing.

In the case of the present embodiment, the high-level waste liquid that is a can has a low transparency because it contains a large amount of fission products and a waste solvent, and the energy of the laser light is efficiently absorbed in the can. When the transparency is high, as shown in FIG. 2, a reflecting plate 11 is provided in the can solution, and laser light is reciprocated in the can solution so that the can solution absorbs energy and is heated.

Further, an embodiment having a function of keeping the temperature of the liquid contacting portion of the evaporator heating portion low will be described with reference to FIG.

In FIG. 3, the high-level waste liquid that is a can liquid is introduced by a can liquid introducing pipe 12 between a partition plate 13 provided inside the heating unit and the heating unit can wall, and flows between the partition plate 13 and the can wall. And flows into the can through the can liquid inlet at the center of the partition plate. The can liquid heated by the laser light from the EDL laser oscillator 3 is evaporated by the relatively low temperature high-level waste liquid continuously supplied from the partition plate 13 and the outside and flowing between the partition plate and the can wall. Since the heating section is separated from the can wall and does not come into direct contact with the can wall, the temperature of the can wall is kept almost the same as the temperature of the high-level waste liquid supplied from the outside. Therefore, the corrosion conditions of the can wall of the evaporator heating unit are alleviated, which contributes to the longer life of the evaporator. Meanwhile, the partition plate 13
Is in contact with hot can liquid and placed under severe corrosive conditions, but since it is not the primary partition wall that encloses the can wall, even if defects such as pinholes occur due to corrosion, the function of the evaporation can itself is impaired. Does not hinder.

Although laser light is used as the heating source in the above embodiments, microwaves can also be used as the heating source. In that case, it goes without saying that a waveguide is used instead of the reflecting mirror 5.

〔The invention's effect〕

According to the present invention, the can wall is protected by introducing the solution between the can wall and the partition plate of the evaporating can, and the can liquid is heated by the laser beam, without passing through the metal heat transfer surface. Since the corrosive solution can be directly heated, it comes into contact with the corrosive solution at high temperature, is placed under severe corrosive conditions, and eliminates the metal heat transfer surface itself, which is the most corrosive in conventional evaporators. , The corrosive solution evaporator itself can have a long life and be maintenance-free.

Specifically, when nitric acid concentration of 9.0 to 9.5 N, pressure of 155 to 170 Torr, and temperature of 70 to 75 ℃ are evaporated under reduced pressure, the corrosion rate of the heat transfer surface made of SUS304L is 0.02 to 0.05 mm / year. The corrosion rate is 0.01-0.04 mm / year. When a SUS304L evaporator is manufactured according to the present invention, since there is no heat transfer surface, the life of the evaporator due to corrosion is determined by the corrosion rate of the wetted part of the heating part (immersion surface), and Compared with having 1.
2 to 2 times longer.

Further, the scale does not adhere to the metal heat transfer surface due to the precipitation of the can component and the adhesion of the insoluble component in the can.
As a result, the maintenance for removing the scale that lowers the heat transfer efficiency becomes unnecessary, and the maintenance can be made free.

Furthermore, since the evaporator and the laser oscillator can be installed separately, the maintenance of the laser oscillator is easy, and the laser oscillator can be installed in a place where the environment of use is good, and the evaporative can main body is sufficiently maintenance-free. You can make use of it.

[Brief description of drawings]

FIG. 1 is a vertical cross-sectional view of an embodiment in which the present invention is applied to a high-level liquid waste evaporator of a nuclear fuel reprocessing facility, and FIG. 2 is a laser beam reflector in a can solution when the can solution has high transparency. FIG. 3 is a vertical cross-sectional view of the provided embodiment, and FIG. 3 is a vertical cross-sectional view of an embodiment in which a partition plate is provided along the can wall of the heating portion of the evaporator and a solution is externally supplied between the can wall and the partition plate. . 1 ... Evaporator heating part, 2 ... Evaporator fractionating tower, 3 ... EDL
Laser oscillator, 4 ... Quartz glass window, 5 ... Reflector, 6
…… Shield door, 7 …… Laser oscillator cell, 8 …… High level waste liquid evaporator installation cell, 9 …… Steam separator, 10 …… Valve cap tray, 11 …… Laser light reflector, 12 ・ ・ ・… Can liquid introduction pipe, 13 …… Partition plate.

Claims (3)

[Claims] 1. A corrosive solution evaporator comprising a heating part for containing a corrosive solution and heating and evaporating the same, and a fractionating column for fractionating vapors heated and evaporated in the heating part, the inside of a can wall of the heating part. A partition plate is provided along the opening, and an opening of a can liquid introducing pipe for introducing the solution from the outside is provided between the partition plate and the can wall, and the opening between the can wall and the partition plate is provided from the opening. The solution introduced into the can is introduced into the can from below the partition plate, and a window is provided in a portion of the heating section that does not come into contact with the solution, and the laser is irradiated with laser light to heat the solution from the window. A corrosive solution evaporator equipped with an oscillator. 2. The corrosive solution evaporation can according to claim 1, wherein an optical system such as a reflecting mirror is provided between the laser oscillator and the window. can. 3. The corrosive solution evaporation can according to claim 1 or 2, wherein a reflecting plate for reflecting the laser beam incident on the solution is provided in the solution. Evaporative solution can.