JPS61195400A - Method of treating waste liquor containing radioactive nuclide - 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 The present invention relates to a method for treating waste liquid containing radionuclides discharged from a nuclear power plant or nuclear facility.

The Radwest facility, ie, the radioactive waste processing facility, at the BWR nuclear power plant is roughly divided into a waste liquid processing section and a solidification processing section. The waste liquids to be treated with this equipment are equipment drain waste liquid, floor drain waste liquid, ion exchange regeneration waste liquid, and laundry waste liquid. Of these, equipment drain waste is filtered and desalted, collected in a condensate storage tank, and reused within the power plant.

On the other hand, floor drain waste liquid and ion-exchange recycled waste liquid are evaporated and their condensed water is recovered and reused, and concentrated liquid containing radioactive nuclides is assimilated by cement assimilation or plastic solidification to reduce the The level of radioactive waste is assimilated.

Not only does this evaporative concentration require a large amount of energy, but the resulting assimilate must be disposed of as radioactive waste.

Up until now, all waste fluid containing radioactive materials has been treated as radioactive waste by concentrating and reducing its volume and solidifying it, but by treating only the radioactive materials from the waste fluid, the remaining fluid can be rendered harmless. Sure.

If so, a fundamental volume reduction can be achieved.

Utilizing this idea, we can efficiently remove radionuclides from waste liquid, especially from floor drain waste liquid and ion-exchange regenerated waste liquid, which are subject to solidification treatment, and only the extracted radioactive substances are treated as radioactive waste, and the radioactivity is Regarding the waste liquid after treatment, research was conducted to find a way to either release it after monitoring or treat it as extremely low-level radioactive waste.

Some of the present inventors and their collaborators first contacted waste liquid containing radionuclides, particularly complex-forming substances, with activated carbon and then with a chelating ion exchange resin, thereby adsorbing and removing radionuclides. Invent an effective method to
Already disclosed.

(Japanese Unexamined Patent Publication No. 57-48699) The present inventors have continued their research and have established a method for treating waste liquid containing tIL radioactive nuclides, which further enhances the effects of the above-mentioned invention, and so we hereby propose it. .

The method for treating waste liquid containing radionuclides of the present invention involves first filtering the waste liquid to remove floating suspended substances, adjusting the liquid property as necessary to pi-13 to 10, and then chelating the waste liquid. The radionuclides are removed by adsorption to these adsorbents. It is characterized by

The waste liquid after treatment can be monitored and, if it is confirmed that the radioactivity is below the permissible value, it can be discharged or it can be assimilated as waste.

The radionuclides to be treated by the system of the present invention are Cr, which is a corrosion product of equipment and a fission product.
-5L Mn-54, Co-58, Fe-59, Co-
60, Zn-65, Ag-110m, Cs-134,
C5-137, etc., and they exist mainly in the bed drain waste liquid and ion exchange regeneration liquid in ionic, colloidal and complex states.

Although the above-mentioned nuclides exist in various chemical forms, first, floating suspended solids are removed by filtration. For the filtration device, use a non-auxiliary backwash type filtration device. In this step, among the radionuclides mentioned above, Fe-59, Ag-110m, etc. are removed. The filtrate contains ionic, colloidal, and complex nuclides, which are adsorbed.

As the adsorbent, one is used that has the ability to selectively adsorb only radionuclides without being affected by the large amount of Na ions coexisting in the waste liquid.

Cr-5L Mn-54, Co-58, Fe-59,
Ionic nuclides such as Co-60 and Zn-65 are well adsorbed on chelating ion exchange resins.

Chelating ion exchange resins used for this purpose include diethylenetriamine, triethylenetetramine, tetraethylenepentamine, pentaethylenehexazine, etc. as functional groups in a phenolic, styrene, epoxy, or acrylic ester resin matrix. amines, aminocarboxylic acids such as iminodiacetic acid, alcohol amines such as dibrobanolamine, or those into which urea or thiourea is introduced. In particular, a phenolic chelating ion exchange resin in which two iminodiacetic acid groups have been introduced into the phenol skeleton (disclosed in JP-A-53-106789 and commercially available under the registered trademark "UNISELECT") has been found to be useful for radionuclides. It is preferable because it has excellent metal ion removal ability. The functional group end of this type of ion exchange resin is N
Any of the alkali metal types such as a, alkaline earth metals such as Ca, heavy metal types such as Fe, and H types may be used.

Co-58 prone to colloidal and organic complex states
, Go-60 and anionic Cr-51 are adsorbed on activated carbon. Activated carbon can be any of the commonly used coal-based, coconut shell-based, or pitch-based types, and the shape can be selected from granulated, crushed, or powdered coal, but for the convenience of processing liquids, coal-based Alternatively, coconut shell-based granulated charcoal or crushed charcoal is better.

What remains without being removed by the above chelating ion exchange resin and activated carbon are C5-134 and O3-137, and these nuclides are completely removed by zeolite adsorption treatment. The zeolites used here are commercially available as adsorbents, including mordenite, clinoptilite, vermiculite, faujalite, and zara, which are commercially available as natural zeolites and synthetic zeolites, and are generally commercially available as molecular sieves. There are synthetic zeolites, etc.

The precipitates of the crud removed by the filtration process of the system of the present invention and the adsorbent subjected to the adsorption process have radionuclides adsorbed and fixed and are concentrated, so they are treated by assimilation process or the like.

In general, chelating ion exchange resins after use can be subjected to oxidative decomposition using hydrogen peroxide, high-pressure oxidative decomposition using oxygen, and incineration, and there are no problems with exhaust gas treatment because organic gases such as 5O1NOx are not generated. , significant volume reduction is possible.

Activated carbon can also be incinerated. Zeolite, which adsorbs and solidifies cesium nuclides, has a mineral adsorbent itself (mainly AI
, Na, and Ca) and is chemically extremely stable, so it can be disposed of by filling it into a double-walled container (for example, a lined cement drum).
It is also possible to compress it with a hot press to reduce its volume and dispose of it.

An example of a system to which the treatment method of the present invention is applied will be described with reference to the drawings. As shown in FIG. Filter with a non-auxiliary backwash filter. Crud generated during filter backwashing is transferred to a settling tank.

The filtered waste liquid is passed through a chelating ion exchange resin packed column,
It passes through an activated carbon-packed tower and a zeolite-packed tower in order to adsorb and remove radionuclides therein.

The waste liquid from which radionuclides have been completely removed is stored in a sample tank, monitored, and then released into the environment.

There is no radioactivity problem, but if the chemical properties make it inappropriate to release it, it can be evaporated and concentrated, then solidified into cement to become an extremely low-level assimilation product. The used chelating ion exchange resin can be solidified, such as plastic solidification, as described above, but if it is treated by oxidative decomposition, especially wet oxidative decomposition, it will mainly decompose into water and carbon dioxide.
Only the adsorbed metal elements and radionuclides remain as residue, resulting in a high degree of volume reduction. The used activated carbon and zeolite are also in a stable chemical form as mentioned above, and are therefore treated in a radioactive waste assimilation treatment system along with the crud produced in the backwashing of the filter.

The treatment method of the present invention removes and concentrates the radioactive waste in the waste liquid and targets only it for solidification treatment, and is safe as it can be operated at room temperature and pressure.

Compared to conventional technology that evaporates and concentrates all of the waste liquid, it can save a lot of energy and also reduce the amount of radioactive waste assimilate.

Example 1 Cr-51, Mn-54, Fe-59, Co-60
, Zn-65, Ag-110m, Cs-134 and Cs-137 (conductivity 30-1
50μs/cm, at-16~7), 0.04μ
Filtration treatment was performed using a non-auxiliary type backwash filter equipped with a precision filter. Next, the filtrate is treated with phenolic chelate resin "UNISELEX" (registered trademark of Unitika Co., Ltd.) UR.
-10250d in a column packed with space velocity (SV)
= 5 Hr' downward flow, then 5 V = 5 Hr-1 into a column packed with 250 d of coconut shell-based crushed activated carbon.
With a downward flow of 5 V = 5
The liquid was passed in a downward flow at a speed of Hr-1.

At each stage, the liquid to be treated was periodically sampled and its radioactivity concentration was measured for each nuclide. The results are shown in FIG. In this figure, the nuclide concentration is shown as a value relative to the release allowable value, but the effect of the treatment according to the present invention can be clearly seen.

The radionuclides coexisting in the floor drain waste liquid are first removed by filter filtration to remove Fe-59 and ACI-110m, then treated by UR-10 to remove Mrl-54 and Zr1-65, and activated carbon treatment to remove Cr-51 and ACI-110m. Co-
60, and Cs-134 and Cs by zeolite
5-137 was adsorbed and became below the detection limit. This waste liquid can be released into the environment.

X dust cloud 2 Mn-54, Co-60, Zn-65, Ag-110m
, Cs-134 and Cs-137 (conductivity: 13 ms/cm).

pH 6>, the filter and each packed column used in Example 1 were used, and the subsequent treatment was carried out under the same conditions and procedures as in Example 1.

The results are shown in FIG. As in Example 1, all radionuclides in the ion exchange regeneration waste liquid could be removed to a concentration below the detection limit.

[Brief explanation of drawings]

FIG. 1 is a flowchart showing a treatment system for waste liquid containing radionuclides that incorporates the method of the present invention. FIGS. 2 and 3 are graphs showing the effects of the embodiments of the present invention, and show how radionuclides are removed through filtration and adsorption. Patent Applicant: Tokyo Electric Power Company, Inc. JGC Corporation Agent, Patent Attorney: So Suga Cannon Tube 1, Figure 2

Claims (3)

[Claims] (1) The waste liquid containing radionuclides is first filtered to remove suspended solids, and then the waste liquid is brought into contact with a chelating ion exchange resin, activated carbon, and zeolite in this order to adsorb and remove the radionuclides. A method for treating waste liquid containing radionuclides, characterized by: (2) The treatment method according to claim 1, wherein the waste liquid containing radionuclides is a bed drain waste liquid or an ion exchange regeneration waste liquid. (3) The treatment method according to claim 1 or 2, wherein the filtration treatment is performed using a non-auxiliary material type backwash filter.