JPS6358299A - Pyrolytic processing method and pyrolytic processor for radioactive chemically decontaminated waste liquor - Google Patents

Abstract

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

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Industrial Application Field) The present invention relates to a thermal decomposition treatment method and a thermal decomposition treatment apparatus for radioactive chemical decontamination waste liquid used in nuclear facilities.

(Prior art) In nuclear power facilities such as nuclear power plants, free-range substances are incorporated into the iron oxide film that forms on the surfaces of equipment, piping, etc., and become a source of radiation exposure. Chemical decontamination treatment is performed to dissolve and remove this iron oxide film adhering to the surfaces of pipes and the like using a chemical decontamination agent. In such chemical decontamination treatment at nuclear power plants, chemical acids such as citric acid, oxalic acid, and formic acid and EDTA are generally used because they cause less corrosion and are easier to handle. Chemical decontamination agents based on decontaminants are used.

At present, there is no technology available to treat such large amounts of waste fluid containing chelating agents and chelate compounds in nuclear power plant radioactive waste treatment equipment, so chemical decontamination is necessary. tI generated by using the agent
I-regulated chemical decontamination fluid is assimilated separately from other waste in a temporary assimilation device.

(Problem to be solved by the invention) However, when large-scale chemical decontamination is carried out, a large amount of removed radioactive substances will be contained in the radioactive chemical decontamination waste liquid, and this assimilation work will be difficult. At the same time, there is a risk of being exposed to a large amount of radiation, and it is also necessary to store and store a large amount of assimilated radioactive chemical decontamination waste liquid with high ω radiation.
This was a huge burden on waste disposal.

The present invention provides a special solidification device and a special solidification device for treating radioactive chemical decontamination waste liquid by decomposing organic acids, chelating agents, and chelate compounds in radioactive chemical decontamination waste liquid so that they can be treated with existing radioactive waste treatment equipment. An object of the present invention is to provide a thermal decomposition treatment method d3 for radioactive chemical decontamination waste liquid and a thermal decomposition treatment apparatus that eliminate the need for assimilate storage equipment and facilitate the assimilation process of radioactive chemical decontamination waste liquid that is likely to cause radiation exposure. shall be.

[Structure of the Invention] (Means for Solving the Problems) The thermal decomposition treatment method for radioactive chemical decontamination waste liquid of the present invention is a method for thermally decomposing radioactive chemical decontamination waste liquid, which uses organic acids, chelating agents, and chelating agents generated in the nuclear 1M stage.
1. Radioactive chemical decontamination waste liquid containing compounds is heated in an oxidizing atmosphere to thermally decompose it, and the generated water vapor and thermal decomposition gas are each treated in a scientific system and discharged outside the system. The remaining radioactive metal oxide is stored in a storage container, and the thermal decomposition treatment apparatus for radioactive chemical decontamination waste liquid of the present invention includes a thermal decomposition column containing a fluidized bed forming material, and this thermal decomposition column. A heated gas supply system that supplies heated gas into the tower from the bottom of the pyrolysis tower, and a waste liquid supply system that supplies radioactive chemical decontamination waste liquid containing organic acid, chelating agents, and chelate compounds generated at nuclear facilities into this pyrolysis tower. , an exhaust treatment system for treating water vapor and pyrolysis gas generated in the pyrolysis tower, and a decomposition residue treatment system for discharging radioactive metal oxides remaining in the pyrolysis tower and filling them into a storage container. It is characterized by having the following.

(Function) In the thermal decomposition treatment method of the present invention, organic acids such as citric acid, oxalic acid, and formic acid, which are the main components of the chemical decontamination agent, and chelating agents such as EDTA J5. The J and chelate compounds are thermally decomposed by heating in an oxidizing atmosphere, generating water vapor and thermal decomposition gases such as Co, CO2, No, and N02.1-12. Then, the metal, free metal ions, metal hydroxide, etc. in the chelate compound are oxidized to become metal oxides.

The steam and pyrolysis gas generated here are treated in an exhaust treatment system that includes a condenser. Meanwhile, the decomposition residue metal oxide sludge containing most of the radioactivity in the radioactive chemical decontamination waste liquid is transferred and stored in a sludge storage container.

(Example) Hereinafter, an example of the present invention will be described with reference to the drawings. - FIG. 1 is a diagram schematically showing the configuration of a thermal decomposition treatment apparatus for radioactive chemical decontamination waste liquid according to an embodiment of the present invention.

As shown in FIG. 1, the pyrolysis treatment apparatus of this embodiment has the following features:
It is mainly composed of a thermal decomposition tower 10, a heated gas supply system 20, a radioactive chemical decontamination waste liquid supply system 30, an exhaust treatment system 40, and a decomposition residue treatment system 50.

The pyrolysis tower 10 is a vertical container divided into two upper and lower chambers by a screen 11, and the upper chamber 12 is filled with heat carrier particles 13 made of iron powder or iron oxide powder with a particle size of several μm to several hundred μm. has been done.

The heated gas supply system 20 is connected to the top of the pyrolysis column 10.
A circulation pipe p2 is connected at one end to the steam/exhaust gas discharge pipe β1 and the other end is connected to the lower chamber 14 of the pyrolysis tower 10, and a circulation return valve 2 connected in the middle of this circulation pipe 22.
1, a blower 22, a heater 23Lt3, and a circulation valve 24.

The radioactive chemical decontamination waste liquid supply system 30 includes a waste liquid link 31 containing radioactive chemical decontamination waste liquid containing an organic acid, a chelating agent, and a chelate compound generated in the atomic htii facility, this waste liquid tank 31, and the top of the pyrolysis tower 10. It consists of a waste liquid supply pipe J:13 connecting the waste liquid supply pipe J:13, a waste liquid supply pump 32, and a waste liquid supply valve 33 connected in the middle of this waste liquid supply pipe J23.

The exhaust treatment system 40 includes a condenser 43 connected to the water vapor/exhaust gas discharge pipe λ1 via an exhaust valve 41 and an exhaust flow rate adjustment valve 42, and a vent valve 44 in the gas phase of the condenser 43.
A cooling water injection pipe β5 is connected to the condenser 43 via a cooling water valve 45, and a condensed water transfer pipe β6 is connected to the condenser 43 via a condensed water valve 46. There is.

Further, the decomposition residue discharge system 50 includes a transfer water injection pipe 7 equipped with a transfer water valve 51, an air injection pipe β8 equipped with an air injection valve 52, and a sludge transfer valve 53, which are connected to the pyrolysis tower 10, respectively. It is composed of a sludge transfer pipe 9 equipped with a sludge transfer pipe 9.

Next, a method for treating radioactive chemical decontamination waste liquid using this apparatus will be explained with reference to FIGS. 2 and 3.

Of the various valves shown in FIGS. 2 and 3, valves without parentheses indicate that they are in an open state, and valves with symbols indicate that they are in a closed state.

When carrying out thermal decomposition treatment of radioactive chemical decontamination waste liquid, as shown in FIG.
is activated to send hot air from the lower part of the pyrolysis tower 10 to heat the heat carrier particles 13 to 200° C. or higher, while also forming a fluidized bed.

Next, the radioactive chemical decontamination waste liquid is transferred from the waste liquid tank 31 by the liquid supply pump 32 through the waste liquid main valve 33 to the thermal decomposition tower 10.
and spray from the top.

The radioactive chemical decontamination waste liquid that has fallen onto the fluidized bed made of heat transfer particles 13 has its water evaporated due to heat transfer from the heat transfer particles 13, and dissolved organic acids such as citric acid, oxalic acid, and formic acid. , chelating agents and chelate compounds such as EDTA are thermally decomposed to produce water vapor and Co, CO2, NO.
, NO2, and 12 are generated, and the metal components become metal oxides. Of these, steam and pyrolysis gas are discharged from the -F section of the pyrolysis tower 10 through the steam/waste discharge pipe J2.1, enter the circulation pipe β2 via the circulation source valve 21, and are heated by the heater 23. The radioactive chemical decontamination waste liquid is heated and decomposed by circulating between the pyrolysis tower 10 and the steam/exhaust gas discharge pipe β1.

When the internal pressure of the heated gas supply system rises by 2' due to the increase in water vapor and pyrolysis gas generated during the pyrolysis treatment of radioactive chemical decontamination waste liquid, the exhaust valve 41 and the exhaust flow rate adjustment valve 42 are turned on and a portion of the circulating gas is removed. is sent to the capacitor 43.

Part of this circulating gas can be exhausted by keeping the exhaust valve 41 and the exhaust flow rate control valve 42 open at all times to avoid exhausting the gas continuously during the thermal decomposition process.
The metal oxide sludge and heat medium particles 13 mixed in the circulating heating fluid may be prevented from flowing out by stopping the heating circulation and exhausting the heating fluid alternately.

Water vapor in the circulating gas sent to the condenser 43 is cooled and becomes condensed water, and air and pyrolysis gas are sent to the vent valve 44.
is discharged through the existing exhaust system. The condenser 43 is cooled with cooling water supplied through the cooling water valve 45, and the cooling water that has absorbed the heat of the steam and pyrolysis gas and the condensed water of the steam are converted into condensed water through the condensed water valve 46. Transfer pipe β
6, the waste is sent to the existing radioactive waste disposal facility 11 for treatment.

On the other hand, metals, free metal ions, metal hydroxides, etc. in the chelate compound generated by thermal decomposition in the pyrolysis tower 10 are oxidized and remain as metal oxides, and this metal oxide sludge is dried and solidified. It becomes a fine powder and becomes heat carrier particles 13.
Together with these particles, they form part of the fluidized bed particles.

In this way, only metal oxide sludge is accumulated in the tower, and when a predetermined amount has been accumulated, the blower 22 and heater 23 are stopped, and the waste liquid supply valve 33 and circulation source valve 21 are stopped, as shown in FIG. and circulation valve 24, and instead open the transfer water valve 51, air source valve 52, and sludge transfer valve 53 to inject transfer water and air into the pyrolysis tower 10.
The heat transfer medium particles 13 and metal oxide sludge in the transfer water are suspended in the transfer water through an agitation tube V, and discharged together with the transfer water to a sludge storage tank (not shown). Note that the injected air is discharged from the water/air/exhaust gas discharge pipe β1 to the exhaust equipment υ1.

In the above embodiments, an example was described in which thermal decomposition was performed using only the heater 23 as a heat source. The column 10 may also be heated externally.

[Effects of the Invention] As explained above, according to the present invention, bt'J'J chemical decontamination waste liquid is thermally decomposed to thermally decompose organic acids, chelating agents, and chelate compounds in the radioactive chemical decontamination waste liquid. Since the water vapor, pyrolysis gas and metal oxide were
J! It can be easily disposed of using radioactive waste treatment equipment.

According to the present invention, there is no need for a dedicated solidification device for tiJIQ old biochemical decontamination waste liquid or a storage facility for storing assimilated radioactive chemical decontamination waste liquid containing high concentration radioactivity.
A high volume reduction rate can be achieved.

In addition, solidification of radioactive chemical decontamination waste liquid and handling of solidified waste, which are often exposed to radiation from radiation, are no longer necessary, and equipment costs and exposure to radiation from radiation caused by decontamination are significantly reduced, and nuclear power generation This makes it easier to carry out chemical decontamination treatment at nuclear facilities such as nuclear facilities.

[Brief explanation of the drawing]

Figure 1 shows the thermal pretreatment of radioactive chemical decontamination waste liquid according to the present invention]! I
l! A diagram schematically showing a drawing of the apparatus, FIG. 2 is a diagram for explaining the pyrolysis step of the method of the present invention, and FIG. 3 is a diagram for explaining the sludge transfer step of the method of the present invention. . 10...Pyrolysis tower 11...Screen 12...Upper chamber 13...Heat carrier particles 14 ...... Lower chamber 20 ... Heated gas supply system 21 ...
...Circulation source valve 22...Blower 23...Heater 24...Circulation valve 30...・Waste liquid supply system 31... Waste liquid tank 32... Waste liquid supply pump 33...
... Waste liquid supply valve 40 ... Exhaust condensing system 41 ... Exhaust valve 42 ... Exhaust flow rate adjustment valve 43 ...・・・
...Condenser 44...Vent valve 45...Cooling water valve 46...Condensed water valve 47 50... ... Decomposition residue discharge device 51 ...
・・・・・・Transfer water valve 52・・・・・・・・・Air source valve 53・・・・・・・・・Sludge transfer valve agent Patent attorney Nori Chika Ken Shu Kanshu Hirofumi Mitsumata

Claims (2)

[Claims] (1) Radioactive chemical decontamination waste liquid containing organic acids, chelating agents, and chelate compounds generated at nuclear facilities is heated in an oxidizing atmosphere to thermally decompose it, and the generated water vapor and thermal decomposition gas are treated in an exhaust treatment system. and discharge it out of the system,
A method for thermally decomposing radioactive chemical decontamination waste liquid, the method comprising storing residual radioactive metal oxides in a storage container. (2) A pyrolysis tower containing a fluidized bed forming material, a heated gas supply system that supplies heated gas from the lower part of the pyrolysis tower into the tower, and an organic acid generated at a nuclear facility into the pyrolysis tower.
a waste liquid supply system that supplies a radioactive chemical decontamination waste liquid containing a chelating agent and a chelate compound; an exhaust treatment system that processes water vapor and pyrolysis gas generated in the pyrolysis tower; 1. A thermal decomposition treatment apparatus for radioactive chemical decontamination waste liquid, comprising a decomposition residue treatment system for discharging radioactive metal oxides and filling them into a storage container.