JPS6214098A - Microwave heating evaporator - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is a method for reducing the volume and decontaminating radioactive liquid waste such as nitric acid used in the process of reprocessing spent nuclear reactor fuel. The present invention relates to a device for heating and evaporating , and particularly to a microwave heating evaporation device that uses microwaves as a heating source.

[Conventional technology]

As a heating evaporation apparatus for volume reduction and decontamination of radioactive liquid waste, one having the configuration shown in FIG. 2 has been known.

In FIG. 2, radioactive liquid waste is supplied into the evaporator 1 from the lower liquid supply port 4. A multi-tube heat exchanger 117 is installed in the evaporator 1, and the radioactive liquid waste is heated by exchanging heat with steam introduced from the steam port 8, and thereby evaporated. Condensed water generated during this heat exchange is discharged from the condensed water outlet 9.

The radioactive liquid waste heated and evaporated as described above in the evaporator 1 is transferred to the cylindrical flash chamber 2 via the connecting pipe 3.
where it is separated into a vapor phase and a liquid phase. The separated vapor phase is led to the next step through the steam outlet 6, and the liquid phase condensed water is recovered through the condensed water outlet 5. In addition,
A collision baffle plate 10!3 and a demister 11 are provided in the flash cavity 2.

[Problem that the invention seeks to solve]

In such a heating evaporator, if the radioactive liquid waste is nitric acid or the like, there is a problem of corrosion inside the evaporator 1. In particular, in conventional equipment, the multi-tubular heat exchanger 7 inside the evaporator 1 has many welded parts, which raises the possibility of corrosion, and there is a risk that radioactive liquid waste may leak through pinholes caused by corrosion. .

Furthermore, since the tubes of the multi-tubular heat exchanger 17 have a small inner diameter, there is also the problem of significant scale formation. Therefore, it is necessary to periodically remove the generated scale, making maintenance very complicated.

The present invention was made to solve these conventional problems, and its purpose is to provide a microwave heating evaporation device that is less likely to be corroded by radioactive liquid waste and that produces less scale. It is in.

[Means for Solving the Problems] The microwave heating evaporation device according to the present invention includes a spray tower that sprays supplied radioactive liquid waste into fine droplets, and a spray tower that sprays the radioactive liquid waste that is sprayed from the spray tower. an evaporator for heating and evaporating radioactive liquid waste; a flash chamber connected to the evaporator for separating a vapor phase and a liquid phase of the waste; and a flash chamber for heating the waste in the evaporator; The present invention is characterized by comprising a microwave generator for generating microwaves, and a means for guiding the microwaves generated by the microwave generator into the evaporator.

That is, the present invention uses a microwave generator as a heating source for the evaporation of radioactive liquid waste, and the radioactive liquid waste l! This device sprays substances into fine droplets and evaporates them using dielectric heating using microwaves.

(Operation) In the present invention, microwaves from a microwave generator are guided into the evaporator via a waveguide etc. On the other hand, radioactive liquid waste is atomized into the evaporator via a spray tower. The radioactive liquid waste is heated and evaporated by the dielectric heating effect when it is irradiated with microwaves in the evaporator.In this case, the radioactive liquid waste when irradiated with microwaves is in the form of a spray of minute droplets, and the surface area Not only is it large, but it is also highly permeable to microwaves, so it is heated and evaporated extremely efficiently.The evaporated radioactive liquid waste is then vaporized in a flash chamber as before. It is separated into a phase and a liquid phase.

〔Example〕

Hereinafter, the present invention will be explained in detail based on an embodiment shown in FIG.

As shown in FIG. 1, the evaporator 1 is not provided with a shell-and-tube heat exchanger like the conventional one (FIG. 2), but instead the microwave is transmitted from the microwave generator 12 through the waveguide 13. The configuration is such that microwaves are supplied into the evaporator 1 from a microwave transmission window 15 provided at the top of the evaporator 1. Note that a matching device 4 for impedance matching is attached to the waveguide 13 through which the microwave is propagated.

When microwaves are supplied into the evaporator 1 in this way, radioactive liquid waste such as nitric acid supplied into the evaporator 1 from the liquid supply port 4 via the spray tower 16 is dielectrically heated by the microwaves. It is heated and evaporates.

That is, the radioactive liquid waste supplied from the liquid supply port 4 is sprayed into the evaporator 1 as fine droplets by the spray tower 16, and in this state is irradiated with microwaves to be heated and evaporated. .

The evaporated radioactive liquid waste is led to a flash chamber 2 connected to an evaporator 1 via a connecting pipe 3, as in the conventional case.
It is separated into a vapor phase and a liquid phase. Inside flash chamber 2,
A collision baffle plate 10 and a demister 11 are provided.

The vapor phase separated in the flash seedling 2 is led to the next step through the steam outlet 6 provided at the upper part of the flash v2, and the liquid phase, that is, the condensate, is led to the next step through the condensate outlet 5 provided at the lower part of the flash chamber 2. more will be recovered. As mentioned above, radioactive liquid waste l! Materials are heated and evaporated.

〔Effect of the invention〕

As explained above, according to the present invention, dielectric heating using microwaves is used as a heating means for radioactive liquid waste, so it is not possible to use conventional heating evaporation II that uses a heat exchanger, especially a shell-and-tube heat exchanger. In comparison, not only is the structure inside the evaporator simpler, but there are no many welded parts in contact with high-temperature steam, which reduces the amount of liquid waste. j! This solves the problems of corrosion and holes in the evaporator caused by objects.

In addition, since microwaves are reflected by metal surfaces, the area to be heated in the evaporator is limited to radioactive liquid waste, and corrosion due to heating of the metal surface, which occurs when using the multi-tube heat exchanger I, is avoided. Problems can be avoided. Therefore, in the present invention, it is possible to completely eliminate the risk of leakage of radioactive liquid waste.

Furthermore, since there is no need to use thin tubes unlike the multi-tube heat exchanger, the generation of scale is significantly reduced, and maintenance for scale removal etc. is facilitated.

Furthermore, microwaves for heating can be efficiently supplied from the microwave generator to the evaporator using a waveguide, etc.
The microwave generator can be installed outside the tl1 secant control area, which is also advantageous in terms of maintenance. Also,
It is also possible to remotely control the entire heating evaporation device via the microwave generator.

In the present invention, in particular, radioactive liquid waste is irradiated with microwaves while being sprayed into the evaporator as fine droplets, so the surface area of the liquid phase in the state of microwave irradiation is large, and the microwave Because of its good permeability,
It has the advantage of high heating and evaporation efficiency.

[Brief explanation of drawings]

FIG. 1 is a longitudinal cross-sectional view showing an embodiment of the microwave heating evaporation device according to the present invention, and FIG.
FIG. 1... Evaporator, 2... Flash chamber, 3... Connecting pipe, 4... Liquid supply port, 5... Concentrate outlet, 6... Steam outlet, 10... Collision obstruction Board, 11...Demister,
12... Microwave generator, 13... Waveguide, 1
4... Matching box, 15... Microwave transmission window, 16.
...Spray tower.

Claims (1)

[Claims] a spray tower that sprays the supplied radioactive liquid waste into fine droplets; an evaporator that heats and evaporates the radioactive liquid waste that is sprayed from the spray tower; A flash chamber that separates the vapor phase and liquid phase of waste; a microwave generator that generates microwaves to heat the waste in the evaporator; and a microwave generator that generates microwaves that heat the waste in the evaporator. A microwave heating evaporation device characterized by comprising means for introducing the evaporator into the evaporator.