JPS6365901A - Evaporation of corrosive solution and evaporator - Google Patents

Abstract

PURPOSE:To prevent an evaporator from becoming corroded and adhence of scales by heating solution by mans of laser beam or microwave in a noncontacting manner and remote operation, not through heat transfer of the evaporator. CONSTITUTION:In a kettle-type high level waste liquor evaporator consisting of a heating section 1 and a fractional distillation column 2, a silica glass window 4 is provided on the section not contacting liquid in the upper part of the heating section of an evaporator, and from the window 4, incident laser beam is emitted to the evaporator to heat up the solution. Laser beam is protected from an EDL laser oscillator, with direction a modified by a reflector 5, and emitted into the evaporator through the silica glass window 4. The EDL laser oscillator 3 is separated from the evaporator having a high radiation does rate, being installed in a cell 7 for the laser oscillator. Since the solution is heated up through a metal heat transfer surface, the evaporator is prevented from becoming corroded, being provided with a life of 1.2-2 times longer than that of conventional evaporators.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a method for evaporating a corrosive solution and an evaporator;
In particular, the present invention relates to a heating method and apparatus for an evaporator, which is required to be maintenance-free and have a long service life because it is used in a high radiation environment such as in a nuclear fuel reprocessing facility.

[Conventional technology]

Conventional devices are of the inner tube type, in which the heat transfer tube is immersed in the liquid in the heating section of the evaporator, as described in JP-A No. 58-36601, or the heating section of the evaporator is covered with a jacket, and the heated fluid is poured into the jacket. It was a jacket type that could be worn.

Since all of these heat the can liquid through a metal heat transfer surface, if the can liquid is a corrosive fluid, the heat transfer surface is subjected to severe corrosive conditions. In addition, since the can liquid is heated through a metal heat transfer surface, scale easily adheres to the heat transfer surface, and the attached scale significantly reduces heat transfer efficiency, requiring maintenance to remove scale.

[The problem that the invention attempts to solve]

The above-mentioned conventional technology does not give consideration to maintenance-free design and long life. In particular, when used in harsh environments such as high radiation, such as high-level waste liquid evaporators in nuclear fuel reprocessing facilities, maintenance is difficult and high reliability is required, so corrosion resistance is also important. The result was an evaporator that was insufficient in terms of maintainability.

It is an object of the present invention to provide a method and an evaporator for evaporating corrosive solutions that do not use metal heat transfer surfaces, which are most problematic in terms of corrosive conditions and scaling.

[Means for solving problems]

In order to achieve the above object, the present invention proposes a method of heating a corrosive solution non-contact and remotely.

Heating is performed by irradiating laser light, microwaves, or the like through a window provided above the solution surface of the evaporator.

In the case of laser light, in order to protect the laser oscillation source, it is desirable to interpose an optical system such as a reflector between the oscillation source and the evaporator to separate the two.

Further, when the solution is transparent, a reflecting plate may be provided in the solution to cause the laser beam to reciprocate multiple times in the solution in order to increase the absorption rate of the laser beam.

Furthermore, a partition plate is provided along the inside of the can wall of the evaporator heating section, and a can liquid inlet pipe for supplying unheated solution from the outside is opened between the heating section can wall and the partition plate, and the can wall itself is It can also be protected.

[Effect]

The laser oscillator emits visible to infrared laser light.

The emitted laser beam enters the evaporator through a window provided in a portion of the evaporator heating section that does not come into contact with the can liquid, and heats the can liquid.

In this method, since heating is performed directly without passing through the metal heat transfer surface, it is possible to eliminate the gold heat transfer surface that comes into contact with the high temperature corrosive tank liquid and is subjected to severe corrosive conditions.

In addition, when heating the can liquid through a metal heat transfer surface, scale adheres to the heat transfer surface due to precipitation of can liquid components or adhesion of undissolved components in the can liquid, which must be removed. Maintenance was required, but the entire gold/[heat transfer surface is gone, and scale removal is no longer necessary.

Furthermore, by installing a reflector between the evaporator and the laser oscillator, the laser oscillator, which is considered to require the most maintenance among the components of the corrosive solution evaporator according to the present invention, can be separated from the evaporator body, making maintenance easier. Can be placed in an easy location.

In the case of microwave heating, a waveguide is used to connect the first oscillator and the window of the evaporator.

If the solution is transparent, installing a reflector in the solution that causes the laser beam to reciprocate multiple times will increase efficiency.

By providing a partition plate along the inside of the can wall of the evaporator and supplying the solution from between the can wall and the partition plate, the can wall is kept at a relatively low temperature and protected. In this case, even if some scale is crushed or pinholes are formed on the partition plate, there is no adverse effect on the outside because it is not the can wall itself.

〔Example〕

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

In a kettle-type high-level waste liquid evaporator consisting of a heating section 1 and a fractionator 2, a portion above the heating section that does not come into contact with the bottom liquid is
A window 4 made of quartz glass with high transparency and low energy absorption is provided. The 1 reflecting mirror 5 and the EDL laser oscillator 3 are arranged so that the laser beam enters into the can from this 14. The EDL laser oscillator 3 avoids primary radiation from the high-level waste liquid in the high-level waste liquid evaporator during normal use, and can be isolated from the cell 8 in which the high-level evaporator is installed by a shield W1 door 6 during maintenance. Place 112 on the dexterity self.

This embodiment with the above configuration operates as follows.

High-level waste liquid, which is can liquid, is emitted from the EDL laser oscillator 3 and reflected! ! The direction is changed at 5, and the laser beam enters the inside of the can through the quartz glass window 4, and the can is heated directly without contact, without passing through a metal heat transfer surface.

The EDL laser oscillator 3 is installed in the laser oscillator self, using a reflector 5, and separated from the high-level waste liquid evaporator with a high radiation dose rate, and is installed in the laser oscillator self-container using a reflector 5. Prevent primary radiation from being emitted. Furthermore, during maintenance of the EDL laser oscillator 3, the shielding door 6 is closed to isolate the laser oscillator self from the cell 8 in which the high-level waste liquid evaporator is installed, thereby blocking radiation.

Improves safety during maintenance.

In the case of this example, the high-level waste liquid, which is the can liquid, has low transparency because it contains a large amount of fission products and waste solvent, and the energy of the laser beam is efficiently absorbed by the can liquid. When the transparency is high, as shown in FIG. 2, a reflective plate 11 is provided in the can liquid.

Laser light is sent back and forth within the can liquid, causing the can liquid to absorb energy and heat it.

Furthermore, an embodiment in which the temperature of the liquid-contacted part of the evaporator heating section is kept low will be described with reference to FIG.

In FIG. 3, high-level waste liquid, which is can liquid, is introduced between a partition plate 13 provided inside the heating section and the heating section can wall through a can liquid introduction pipe 12, and flows between the partition plate 13 and the can wall. Then, the liquid flows into the can from the can liquid inlet in the center of the partition plate. The can liquid heated by the laser beam from the EDL laser oscillator 3 is heated by the relatively low-temperature high-level waste liquid that is continuously supplied from the partition plate 13 and the outside and flows between the partition plate and the can wall, to the evaporator heating section. The temperature of the can wall remains approximately the same as the temperature of the externally supplied high-level effluent. Therefore, the corrosion conditions on the wall of the evaporator heating section are alleviated, contributing to extending the life of the evaporator. On the other hand, the partition plate 13 comes into contact with the high-temperature tank liquid and is placed under severe corrosive conditions.

Since it is not a primary partition that encloses the can wall, even if defects such as bottle holes occur due to corrosion, the function of the evaporator itself will not be affected.

In the above embodiments, laser light was used as the heating source, but microwaves may also be used as the heating source. In that case, it goes without saying that a waveguide may be used in place of the reflecting mirror 5.

〔Effect of the invention〕

According to the present invention, it is possible to directly heat a corrosive solution without going through a metal heat transfer surface. Since the metal heat transfer surface itself, which was subject to severe corrosion, can be eliminated, the life of the corrosive solution evaporator itself can be extended and maintenance-free.

Specifically, the nitric acid concentration is 9.0 to 9.5N, the pressure is 155 to
When evaporating under reduced pressure at 170 Torr and a temperature of 70-75℃, the corrosion rate of the heat transfer surface of 5US304Ll is 0.02~
0.05m++*/year, and the corrosion rate of the immersed surface is 0.
01~0.041! l/year. According to the present invention, 5U
When manufacturing an evaporator made of S304L, there is no heat transfer surface, so the life of the evaporator due to corrosion is determined by the corrosion rate of the heated part (immersed surface), and it is different from a case with a conventional metal heat transfer surface. In comparison, it is 1.2 to 2 times longer.

In addition, scale adhesion to the metal heat transfer surface due to precipitation of can liquid components or adhesion of undissolved components in the can liquid does not occur.
As a result, there is no need for maintenance to remove scale that reduces heat transfer efficiency, making it maintenance-free.

Furthermore, since the evaporator and laser oscillator can be installed separately, maintenance of the laser oscillator is easy, and the laser oscillator can be installed in a location with a good usage environment, making it possible to fully enjoy the benefits of making the evaporator main body maintenance-free. You can make use of it.

[Brief explanation of the drawing]

Fig. 1 is a longitudinal cross-sectional view of an embodiment in which the present invention is applied to a high-level waste liquid evaporator in a nuclear fuel reprocessing facility, and Fig. 2 shows a laser beam reflector plate installed in the liquid in the liquid when the liquid is highly transparent. Fig. 3 is a longitudinal sectional view of an embodiment in which a partition plate is provided along the can wall of the evaporator heating section, and a solution is supplied from the outside between the can wall and the partition plate. be. 1... Evaporator heating section, 2... Evaporator fractionator, 3...
・EDL laser oscillator, 4...quartz glass window, 5...
·Reflector. 6... Shielding door, 7... Laser oscillator cell, 8...
・High-level waste liquid evaporator installation cell, 9... Steam water separator, 10... Valve cap tray, 11... Laser light reflector, 12... Bottle liquid inlet pipe, 13... Partition Board.

Claims (1)

[Claims] 1. A method for evaporating a corrosive solution contained in an evaporator comprising a heating section and a fractionating column, characterized in that the corrosive solution is heated non-contact and remotely. liquid solution evaporation method. 2. The corrosive solution evaporation method according to claim 1, wherein the heating is performed by laser light. 3. The method for evaporating a corrosive solution according to claim 1, wherein the heating is performed by microwaves. 4. In a corrosive solution evaporator consisting of a heating section for heating and evaporating a corrosive solution and a fractionating column for fractionating the evaporated vapor, a window is provided in a part of the upper part of the heating section that does not come into contact with the solution; A corrosive solution evaporator comprising a laser oscillator that irradiates the solution with a laser beam through the window to heat the solution. 5. The corrosive solution evaporator according to claim 4, characterized in that an optical system such as a reflecting mirror is provided between the laser oscillator and the window. 6. A corrosive solution evaporator according to claim 4 or 5, characterized in that a reflecting plate is provided in the solution to reflect a laser beam incident on the solution. 7. In any one of claims 4 to 6, a partition plate is provided along the inside of the can wall of the heating section, and the solution is disposed between the heating section can wall and the partition plate. A corrosive solution evaporator characterized in that a can liquid introduction pipe for supplying from the outside is opened.