JPH0664190B2 - Radionuclide-containing waste liquid treatment method - Google Patents

Description

Detailed Description of the Invention

 Purpose of the invention

[Industrial applications]

TECHNICAL FIELD The present invention relates to an improvement of a method for treating a waste liquid containing a radionuclide, particularly a waste liquid containing at least radioactive strontium, discharged from a nuclear facility such as a nuclear power plant.

[Prior art]

The BWR nuclear power plant Radwest facility, that is, the radioactive waste treatment facility, is roughly divided into a waste liquid treatment portion and a solidification treatment portion. The waste liquid to be treated in this equipment is the equipment drain waste liquid,
It is a floor drain waste liquid, an ion exchange resin regeneration waste liquid, and a laundry waste liquid. Of these, the equipment drain waste liquid is filtered, desalted, received in a condensate storage tank, and reused in the power plant. On the other hand, the floor drain waste liquid and the ion exchange resin regeneration waste liquid are
The condensed water is recovered by evaporation and reused, and the concentrated liquid in which the radionuclide substance is concentrated is solidified by means of cement solidification or plastic solidification to obtain low-level radioactive waste solidified. Not only does this evaporative concentration require a great deal of energy, but the solidified product generated must be disposed of as radioactive waste. Until now, all waste liquids containing radionuclides have been concentrated and reduced in volume as radioactive wastes and then solidified.However, by extracting only very small amounts of radionuclide substances from the waste liquids, If the residual liquid is harmless, the volume can be reduced fundamentally. Utilizing this idea, the radioactive nuclides in the waste liquid, particularly the floor drain waste liquid and the ion exchange resin recycling waste liquid that are subject to evaporative concentration and solidification treatment, are efficiently removed, and only the extracted radioactive nuclide substances are treated as radioactive waste. In addition, regarding the waste liquid after treatment in which the radioactivity has been removed, it is considered that the waste liquid with a very low radioactivity level is considered to be safe after disposal after it has been confirmed by monitoring and safety. Research was conducted in search of a means that can be treated as (for example, a solidified cement). Some of the inventors of the present invention, ⁶⁰ Co, ⁵⁴
Waste liquid containing radionuclides such as Mn, ¹³⁴ Cs, ¹³⁷ Cs, and ⁶⁵ Zn is contacted with activated carbon first and then with chelating ion-exchange resin (hereinafter abbreviated as “chelate resin”). The inventor has invented an effective method for adsorbing and removing radionuclides, and has already disclosed it (JP-A-57-48).
699 and JP-A-57-201899). Then, the waste liquid is filtered first, and then ⁶⁰ C is adsorbed on the chelate resin, zeolite inorganic adsorbent and activated carbon.
A process for removing radionuclides such as o and ¹³⁷ Cs was developed and proposed (Japanese Patent Application No. 60-36057). In the means using these adsorption treatment methods, the treatment operation is simplified by effectively utilizing the capacity of the adsorbent,
In order to reduce the treatment cost as well as to facilitate the disposal and storage of the radioactive adsorbent, a short-lived radionuclide with a rapid decrease in radioactivity, such as ⁵⁴ Mn, ⁶⁰ Co, ⁶⁵ Zn,
It is desirable to separate long-lived radionuclides that slow down, such as ¹³⁷ Cs and ⁹⁰ Sr, and fix them to the adsorbent.

[Problems to be Solved by the Invention]

The object of the present invention is to meet the above-mentioned needs and to provide at least radioactive strontium such as ⁹⁰ Sr and ⁶⁰ Co, ⁵⁴ Mn, ¹³⁴ C.
After the waste liquid containing radionuclides such as s and ¹³⁷ Cs is filtered, it is adsorbed with a chelate resin, the chelate resin bed with only radioactive strontium adsorbed is taken out, and this resin bed is adsorbed with an acid. An object of the present invention is to propose a technique in which radioactive strontium is eluted and desorbed, the eluate regeneration waste liquid is brought into contact with a zeolite inorganic adsorbent, and the radioactive strontium is adsorbed and fixed to the adsorbent. Structure of the invention

[Means for Solving the Problems]

The method for treating a waste liquid containing a radionuclide of the present invention is a method for removing insoluble substances by filtering a waste liquid containing radioactive strontium, and then contacting the waste liquid with a chelating resin to give ⁵⁴ Mn,
^In a treatment method of adsorbing and removing radioactive substances such as ⁶⁰ Co and radioactive strontium, and concentrating, at least two stages of the chelate resin bed (the first stage is "C ₁ ", the last stage is "Cf").
And The example shown in FIG. 1 has two stages, each of which is C
It is represented by ₁ and C ₂ . ), And in consideration of the case where Cs nuclide is present in the waste liquid, the zeolite bed has at least two stages (the first stage is “Z ₁ ”, the last stage is “Zf”. The illustrated example has 2 stages. _They are represented by Z ₁ and Z ₂ , respectively.) When a radioactive strontium leak occurs in the final Cf of the chelate resin bed, Cf adsorbing only radioactive strontium is treated with an acid for elution and desorption, and then treated with an alkali for regeneration. This eluate regeneration waste liquid is brought into contact with a zeolite inorganic adsorbent, particularly an A-4 type zeolite adsorbent,
The presence or absence of radioactive strontium was detected by chemical analysis of magnesium ions present in the liquid as a leak detection method for radioactive strontium in the above Cf effluent while adsorbing and fixing radioactive strontium including the long-lived nuclide ⁹⁰ Sr. Is determined. Also, in the zeolite bed, if Cs nuclide leaks in the final stage Zf, Z ₁ is removed and new Z (f + 1) is prepared.
The waste liquid is passed from Z ₂ toward Z (f + 1) (in the example shown, the zeolite of Z ₁ is replaced with a new _one , and the flow path is switched so that the waste liquid flows in the order of Z ₂ → Z ₃ ). The radionuclides to be treated by the method of the present invention are corrosion products derived from reactor equipment materials and fission products derived from nuclear fuel, ⁵¹ Cr, ⁵⁴ Mn, ⁵⁸ Co, ⁵⁹ Fe, ⁶⁰
Co, ⁶⁵ Zn, ^{110 m} Ag and ¹³⁴ Cs, ¹³⁷ Cs, ⁸⁵ Sr, ⁹⁰ Sr and the like. The above nuclides exist in various chemical forms, and in the waste liquid, they are generally roughly classified into an insoluble form and a dissolved ionic form. Insoluble forms of nuclides (mainly ⁵⁹ Fe, ^{110 m} Ag) are removed by filtering the effluent. A cartridge type filter, a membrane filter, or a non-auxiliary material backwash filter can be applied to the filtration device. Nuclides in dissolved ionic form, eg ⁶⁰ C
O, ⁵⁴ Mn, ⁹⁰ Sr and ¹³⁷ Cs are adsorbed and removed by chelating resin. Chelate resins that selectively adsorb radionuclides include phenol-based, styrene-based, epoxy-based, acrylic ester-based resin bases, and functional groups such as diethylenetriamine, triethylenetetramine, tetraethylenepentamine, and pentaethylenehexamine. Examples thereof include amines, aminocarboxylic acids such as iminodiacetic acid, alcohol amines such as dipropanolamine, and urea or thiourea. In particular, a phenolic chelate resin having an iminodiacetic acid group introduced into the phenol skeleton (commercially available under the registered trademark of "Uniselec") is suitable. Examples of the acid used for the elution treatment of the chelate resin having adsorbed radioactive strontium include sulfuric acid, hydrochloric acid and nitric acid, and hydrochloric acid is particularly suitable. Caustic soda is generally used as an alkali for regenerating the chelate resin. Radioactive strontium is concentrated in the eluate regeneration waste liquid of the chelate resin, but in order to make this radioactive strontium more stable form, it is fixed to an inorganic adsorbent. As the inorganic adsorbent, A-4 type zeolite is particularly suitable among the zeolite minerals in the case of waste liquid having high conductivity. However, unless the electric conductivity of the waste liquid is 10 mS / cm or less, radioactive strontium cannot be adsorbed and fixed on the zeolite.

[Action]

The radionuclide removed in each step is as shown in FIG. In the filter F, radioactive Fe, Ag and Co, Mn
Are partially removed as insoluble substances. If necessary, pH of the effluent prior to filtration to ensure insolubilization
Of course should be adjusted to the region of 6-9. In the next chelate resin bed, first, radionuclides such as Mn, Co and Zn are adsorbed, and then radioactive strontium is adsorbed. In other words, radioactive strontium belongs to the group of radionuclide in the form of dissolved ions that is adsorbed on the chelating resin, but it is difficult to be adsorbed among them, and when radioactive strontium leaks at the final stage of FIG. 1, C ₂ , radioactive Mn, Co , Zn and the like which are strongly adsorbed to the chelating resin are stably adsorbed and fixed to the chelating resin bed before reaching the final stage C ₂ , and radioactive strontium and other radioactive nuclides can be separated. Furthermore, radioactive strontium can be eluted only from the final stage Cf because there is a difference of more than 2 times in the chelate resin adsorption capacity of Co, Mn, Zn nuclides etc. and the radioactive strontium chelate resin adsorption capacity. It can be reused and used effectively. Since the feature of the present invention lies in that only radioactive strontium is adsorbed on the final stage Cf, the leakage of nuclides such as Co, Mn, and Zn in the C (f-1) stage or earlier stages is calculated or measured. , It is important to pay attention in advance. When a leak occurs, the eluate regeneration waste liquid at that stage may be returned to the original waste liquid and treated by this method. By the way, when radioactive strontium is ⁹⁰ Sr, since only β rays are emitted, it takes a long time to measure as compared with those emitting γ radiation such as ⁶⁰ Co and ¹³⁷ Cs,
General in-line measurement is difficult. Particularly in the present invention, it is important to detect easily and promptly that the Cf-treated solution does not leak radioactive strontium. The inventors of the present invention focused on the fact that magnesium ions and calcium ions coexist in the nuclear power plant effluent, although in a small amount, and examined the chelate resin selective adsorption performance of radioactive strontium and these ions. It was found that the ions always leaked earlier from the chelate bed than the radioactive strontium. In other words, radioactive strontium does not leak from Cf even when magnesium ions, which can be easily qualitatively and quantitatively determined by chemical analysis methods and instrumental analysis methods, are detected in the Cf-treated solution. In order to make the radioactive strontium in the radioactive waste strontium elution waste liquid of the chelate resin Cf into a more stable form, it is adsorbed and fixed on the inorganic adsorbent. The present inventors have paid attention to zeolite, which is a mineral containing silicic acid-alumina as a main component, as an inorganic adsorbent, studying its adsorbability, and adjusting the pH of the eluate regeneration waste liquid to 6 to 9 to obtain natural mordenite and A-4. Can be adsorbed on zeolites, especially 10mS / c
It has been found that A-4 type zeolite is preferable in terms of the high-conductivity waste liquid property of m or less. When a cesium nuclide coexists in the waste liquid, radioactive cesium is also adsorbed and removed by placing a zeolite inorganic adsorbent, preferably mordenite, after the cesium nuclide.

Example 1 A waste liquid treatment apparatus having the configuration shown in FIG. 1 was used as a non-auxiliary backwash filter of a hollow fiber filtration membrane, and a chelate resin tower with a phenolic resin “Uniselec” (registered trademark of Unitika Ltd.). UR
It was assembled with two towers packed with -10. The simulated waste liquids having the chemical and radioactive properties shown in Table 1 were prepared and passed through the device. The radionuclide concentrations of the exit treated liquids of the first column C ₁ and the second column C ₂ of the chelate resin column were measured, and the results shown in FIG. 2 were obtained. Comparing the results of these figures, it can be seen that even when radioactive strontium passes through the first tower C ₁ , radioactive cobalt, manganese, etc. do not leak, and radioactive strontium can be separated from these nuclides. Further, the radioactive strontium that has passed through the first tower C ₁ is adsorbed by the second tower C ₂ . On the other hand, radioactive cobalt, manganese in the first tower C ₁ ,
Zinc does not leak even when the treated amount is about 12,000 times.

Example 2 In the second tower chelating resin for adsorption of radioactive strontium
1N-HC was passed through a liquid amount equivalent to 1.5 times the resin amount, and further with pure water equivalent to 3.5 times, to elute 99% or more of radioactive strontium. The eluent was neutralized to pH 7 with NaOH. The electric conductivity of the waste liquid after neutralization was 23 mS / cm, so dilute it with demineralized water to 5 mS / cm.
The solution was passed through an A-4 type zeolite adsorption tower, and the concentration of radioactive strontium in the exit-treated solution was measured. As a result, as shown in FIG. 3, no leakage occurred at the outlet until the liquid flow rate reached 500 times. Furthermore, in order to investigate the conductivity dependence of the adsorption performance of A-4 type zeolite, the waste liquid conductivity was set to 2.5, 7.5, 10 and 15 mS / c.
It was adjusted to m and tested in the same manner, and the results shown in Table 2 were obtained. From this result, it can be seen that radioactive strontium is adsorbed on the A-4 type zeolite when the electric conductivity is 10 mS / cm or less. EFFECTS OF THE INVENTION According to the treatment method of the present invention, radioactive cobalt, manganese, strontium, etc. contained in the floor drain waste liquid or ion exchange resin regeneration waste liquid of a nuclear power plant are filtered and used by using a chelate resin adsorbent. It can be easily removed from the waste liquid, and the treated liquid can be safely released to the environment. Furthermore, utilizing the difference in selective adsorption performance of chelate resins,
Separation of short-lived and long-lived nuclides, especially radioactive strontium can be easily separated from short-lived nuclides such as radioactive cobalt, manganese, and zinc. After elution of radioactive strontium by acid treatment of chelating resin, safe disposal is required especially for a long period of time.
^{For 90} Sr, a more stable immobilization to an inorganic adsorbent can be achieved by adjusting the pH and conductivity of the eluate waste. When radioactive cesium is contained in the bed drain waste liquid or the like, a zeolite mineral is continuously added to the chelate resin adsorbent,
Preferably, after the mordenite is added, radioactive cesium can be separated from other nuclides, and the treated liquid can be safely released into the environment.

[Brief description of drawings]

FIG. 1 is a block diagram of an apparatus for explaining a treatment process of a radionuclide-containing waste liquid of the present invention. 2 to 4 are all graphs showing data of the examples of the present invention, and FIG. 2 is an adsorption curve of nuclides at the outlets of the chelate resin bed columns C ₁ and C ₂ , and FIG. Is the adsorption curve of Sr at the outlet of the A-4 type zeolite bed column, and FIG. 4 is the zeolite bed column outlet of the simulated bed drain waste liquid or the simulated regeneration waste liquid after the adsorption and removal of nuclides other than cesium nuclides by the chelate resin bed. Is an adsorption curve of a nuclide ( ¹³⁴ Cs) in.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (71) Applicant 999999999 Hokuriku Electric Power Co., Inc. 3-1, Sakurabashi, Toyama City, Toyama Prefecture (71) Applicant 999999999 Japan Nuclear Power Co., Ltd. 1-16-1 Otemachi, Chiyoda-ku, Tokyo ( 71) Applicant 999999999 JGC Co., Ltd. 2-2-1 Otemachi, Chiyoda-ku, Tokyo (71) Applicant 999999999 Unitika Co., Ltd. 1-50 Higashihonmachi, Amagasaki-shi, Hyogo (72) Inventor Ichiro Inomata Uchiyuki-cho, Chiyoda-ku, Tokyo 1-3 chome Tokyu Denryoku Co., Ltd. (72) Inventor Tadashi Ishibe 1 Higashishinmachi, Higashi-ku, Nagoya, Aichi Prefecture Chubu Denki Co., Ltd. (72) Masaaki Matsunaga 3-1-1 Sakurabashi-dori, Toyama, Toyama Hokuriku Electric Power Co., Inc. (72) Inventor Ryoichi Onuki 1-6-1, Otemachi, Chiyoda-ku, Tokyo Nihon Nuclear Power Co., Ltd. In-house (72) Inventor Kazunori Suzuki 2205 Narita-cho, Oarai-cho, Higashi-Ibaraki-gun, Ibaraki JGC Stock Company Inside Oarai Nuclear Technology Development Center (72) Inventor Minoru 2205 Narita-cho, Oarai-cho, Higashi-Ibaraki-gun, Ibaraki (72) Inventor Yukihiko Koshiba 2197-46 Shimonagaya-cho, Konan-ku, Yokohama-shi, Kanagawa (72) Inventor Fukuzo Todo 2205 Narita-cho, Oarai-cho, Higashi-Ibaraki-gun, Ibaraki JGC Corporation Orai Nuclear Power Technology Development In the center (72) Masahide Hirai, 23 Uji Kozakura, Uji-shi, Kyoto Prefecture, Central Research Institute of Unitika Co., Ltd. (72) Inventor, Shozo Tomoshige 23, Uji Kozakura, Uji-shi, Kyoto Unitika Research Center, Central Research Institute (72) Invention Kozo Kondo 23, Uji Kozakura, Uji City, Kyoto Prefecture Central Research Institute of Unitika Ltd. (56) References JP 62-161097 (JP, A) JP 62-262784 (JP, A) JP 61- 195400 (JP, A)

Claims (4)

[Claims] 1. A waste liquid containing at least a radionuclide is filtered to remove insoluble substances, and then the waste liquid is brought into contact with a chelating ion-exchange resin (hereinafter abbreviated as "chelate resin") to adsorb and remove the radionuclide. In the processing method to
A chelate resin adsorption tower is installed in at least two stages in series, and when a leak of radioactive strontium occurs in the final adsorption tower, this final adsorption tower is regenerated and reused, and the eluate regeneration waste liquid of this radioactive strontium is reused. A method for treating a radionuclide-containing waste liquid, which comprises adsorbing and fixing to an inorganic adsorbent. 2. The treatment method according to claim 1, wherein the leakage of radioactive strontium in the final stage adsorption tower is determined by detecting magnesium ions coexisting in the outlet liquid. 3. The treatment method according to claim 1, wherein the eluate regeneration waste liquid adsorbed by the inorganic adsorbent is adjusted to have a pH of 6 to 9 and an electric conductivity of 10 mS / cm or less. 4. The treatment method according to claim 1, which is carried out by using A-4 type zeolite as an inorganic adsorbent.