TW459250B - Co-solidification of low level radioactive wet wastes of BWR nuclear power plants - Google Patents

Abstract

This invention discloses a method for the co-solidification of low-level radioactive wet wastes of BWR nuclear power plants, including concentrate waste, spent ion exchange resins and sludge wastes etc., with very high volume efficiency. In this invention, for promoting the stability of the solidified waste, sodium sulfate in the concentrate solution is converted to sodium hydroxide and barium sulfate by reacting with barium hydroxide. The conversion product barium sulfate possessing high density and stability is insoluble and used as a fine aggregate material in the solidified waste. Sodium hydroxide is used to stabilize ion exchange resins and to form a highly water-durable solidified waste form with silicates and phosphates in the solidification agent mixture. The solidification agent mixture. The solidification agent used in this invention is a formulated powder mixture completely made from inorganic materials. Therefore, there is no aging problem of the solidified waste. In this invention, the waste loading of the solidified waste is highly increased due to the conversion of sodium sulfate and the co-solidification of wastes. Thus, the solidification volume efficiency of the present invention is about three times of the solidification of the wastes separately.

Description

^ 592δ〇 5. Description of the invention (1) The operation of the Foshui-type nuclear power plant will produce wet waste materials such as sodium sulfate powdery ion exchange resin and sludge. Because it is radioactive, it must be cured to make it a physical stable solid ’, and then it is finalized to ensure safety. At present, there are often cement solid, solid waste, plastic curing, and asphalt curing methods for curing these wet and radioactive waste materials. The most effective method is the lowest volume stability of the cement curing method. For the sake of simplicity, a good cement solidified body is also praised as 'brother ^ 疋' at the end of the radioactive waste solidified body. The cement solidification method has become the most costly plastic solidified & 1HER & 1 chemical method and asphalt Organic materials are used in the curing method to achieve high volumetric efficiency, but cypresses are very low in strength. There have been examples of cypresses in Germany. In Japan, serious nuclear accidents occurred even a few years ago. As a result, many European countries have consolidated other advanced countries in the law, with the exception of the earlier established Panasonic continuing use, and the addition of new systems to the output of less advanced countries. Asphalt curing method is being phased out and determined. ^ The use of plastic curing method is a very controversial system. You continue to add it, but the negative view is that it will be aging. The use of plastic by humans is only about fifty. It is determined that the plastic solidified material of the temple's material can stabilize the concentrated waste liquid for more than three hundred years. These waste materials have a chemical method (final method). There are three main methods. Of these three, although the cost of the long-term method is increasing, The material is solidified, the oil solidified body has an oil solidified operation, the solidified system has exploded, and the use of the asphalt solidified system is still prohibited. It is no longer available, and it is a problem. Although the newcomers believe that the history of the year is shaped by Quality but not quality

Fifth, the description of the invention (2) changes. As a result, plastic-cured radioactive waste is no longer used in many European countries. Generally speaking, the future of plastic curing methods depends on whether the curing volume efficiency of inorganic curing agents can be improved. Otherwise, under high pressure of final disposal costs, plastic curing methods may still be questioned, relying on their excellent The solidification volume efficiency is used continuously. . In the current situation, research to improve the solidification volumetric efficiency of inorganic curing agents, under the existing basis of ensuring the long-term stability of the quality of the inorganic solidified body, reduce the volume of the solidified body, so that the inorganic solidification method also has the advantage of volumetric efficiency, It is the main research direction of the solidification of low-level radioactive waste. The traditional cement curing method is also an inorganic curing method, but when used in the curing of sulfate waste, sulfate will interact with tri calcium alum inate (C3A) in the cement, and gradually generate a low density I bow. Stones (ettringite), cause deformation of the solidified body structure, and even swell and crack. In order to solve this problem, in addition to reducing the content of sulphate waste added to the cement slurry, cement with low tricalcium aluminate content can also be used. However, the former will increase the volume of the solidified waste solidified by the solidification and increase the final disposal cost; the latter is not easy to obtain due to the low content of tricalcium aluminate, and because the formation of calinite is very slow, the quality of the solidified body changes. It is not easy to detect in a short period of time, but in the long run, it will eventually cause deformation and deterioration of the structure of the solidified body, which will cause a serious problem in the quality of the solidified body. The above problems of solidification of sodium sulfate waste are mainly due to the high reactivity of sodium sulfate. Sodium sulfate is not only easy to dissolve, but also easy to react. In order to avoid these disadvantages in the curing of sodium sulfate, U.S. Patent No. 4,804,498 has proposed the conversion of sodium sulfate from barium hydroxide to barium sulfate and

459250 V. Description of the invention (3) Sodium hydroxide, then the two are separated, sodium argon oxide is recycled and reused, and barium sulfate is solidified. Because barium sulfate has high stability 'and extremely low solubility, the cured body of this method is completely free from the disadvantages of sodium sulfate curing, and the quality is very stable. However, the separation of atmospheric sodium oxide will accompany most of the field radioactive nucleus' and must be processed afterwards to be recycled. The result of recycling will also increase the content of impurities and affect the quality of recycling. Finally, it must be cured. Therefore, the law does not solve the problem. In Japanese Patent Application Laid-Open No. 6 2, 1 2 6, 400, it has been proposed that the sodium sulphate waste liquid is dried into a powder and then mixed with barium hydroxide with crystal water to form water and insoluble sulfates and argon. Oxide steel, and then add hard dioxide and hardener to solidify. This method not only requires the use of evaporative drying equipment that consumes a lot of energy, but also has engineering problems such as solid-solid reaction, stirring, and heat transfer that need to be overcome. Although in Japanese Patent Publication No. 04, 128, 699, it is proposed to convert sodium sulfate with barium hydroxide into barium sulfate and sodium hydroxide without separating the two. After heating and concentrating, add silicon dioxide and cement to solidify Methods. However, the quality of the cement solidified body is greatly affected by the amount of sodium hydroxide. The reaction between sodium dioxide and sodium hydroxide will generate sodium silicate or water glass, and water glass will react with calcium ions released from the hydration reaction of cement to form silica-calcium colloid. Therefore, the quality of the solidified body has a clear relationship with the silicon dioxide raw material, the type and amount of cement. Therefore, in Japanese Laid-Open Patent Publication No. 62, 278, 499, it is proposed that when water glass is used to solidify radioactive waste, its amount must be maintained within the range of Si / Na = 0.5 ~ 1. When the content of sodium hydroxide exceeds 8 wt%, the compressive strength of the cured body drops below 50 kg / cm2.

V. Description of the invention (4) It is stated that even if the sodium sulfate waste is converted into barium sulfate and sodium hydroxide, a good solidified body quality still depends on the type, amount of the curing agent and suitable curing conditions. For the solidification of powdery ion exchange resin waste, most nuclear power plants currently use cement to solidify, and the weight of wet ion exchange resin waste accounts for about 20% of the weight of the solidified body. In this publication, No. 62,238, 499, Cao proposed a method for curing waste ion exchange resin by treating with NaO 加 and then adding blast furnace stone powder, wherein the weight of the ion exchange resin in the solidified body can reach 30%, and the solidified body also has high pressure resistance. strength. Although some of the above-mentioned curing methods can obtain ideal compressive strength, the curing methods they adopt are only for a single waste material, so they do not exert the best volumetric efficiency. The volume of the waste body after curing is still not effective. reduce. The solidification method of the present invention adopts a strategy of solidifying wastes with waste materials. The sodium sulfate waste liquid and the ion exchange resin waste are co-solidified and solidified. The steps and principles of curing are as follows: (1) reacting the sodium sulfate waste liquid with barium hydroxide, The sodium sulphate waste liquid is converted into a slurry containing barium sulfate and sodium hydroxide; (2) The ion exchange resin waste is added to the above slurry of barium sulfate and sodium hydroxide, so that the sodium hydroxide and the ion exchange resin waste are separated first To reduce the ion-exchange activity of the ion-exchange resin and increase its stability; (c) solidification formulated with cement, silica particles, pozzolanic materials such as furnace stone powder and fly ash, and silicates, phosphates, etc. The agent is fully stirred with the mixed slurry of barium sulfate, sodium hydroxide, and ion exchange resin produced in step (2), and is solidified.

Page 10 V. Description of the invention (5) The above method makes the sodium sulfate waste liquid and the ion exchange resin waste solidify together, and exerts the following effects. It is a completely innovative curing method: (1) Low stability sodium sulfate Conversion to extremely stable barium sulfate, not only completely eliminates the problem of instability of the solidified body that may be caused when the sodium sulfate is solidified alone, but also because the density of barium sulfate is extremely high (the specific gravity is 4.5), which can effectively reduce the solidified body Volume; (2) Barium sulfate can be used as a fine aggregate during curing, which can increase the strength of the cured body; (3) After the action of sodium hydroxide and the waste ion exchange resin, the exchange activity of the ion exchange resin can be reduced, and curing can be avoided The bulk expansion phenomenon improves the stability and quality of the solidified body, and improves the volumetric efficiency; (4) All the conversion products are solidified, no second waste is generated, and there are no difficult problems caused by the need to recycle the conversion products; (5) Through the preparation technology of curing agent, sodium hydroxide can form an insoluble cured substance with the curing agent for embedding and curing waste. , The amount of curing agent to reduce the circumference, an effect cure waste to waste. The following inventors will exemplify the curing and curing agent preparation methods of the present invention by experiments. These experiments are only some examples of the present invention and do not represent the full scope of the present invention. Therefore, they cannot be used to limit the scope of the present invention. Example 1: Take 9200 parts (by weight, the same below) of 98% sodium hydroxide and 2760 parts of barium sulfate, and slowly add 2 300 parts of deionized water under stirring; wait for the sodium hydroxide to completely dissolve After that, it was cooled and maintained at 30 oC. Before adding the curing agent, the solution was re-weighed and the same weight of water was used to replace the weight of water lost during evaporation.

Page 11 459? V. Description of the invention (6) Take the type 2 A sludge hardener produced by Taiwan Cement Company, and bl as t furnace slag powder from pozzo lani c mater i al s. 14% 、 A1203 6 After mixing with fly ash, and calcium, silicon, magnesium and other powders of phosphoric acid, grinding to prepare a uniform curing agent powder. After analysis, the main components are as follows: Si02 27. 14%, A1203 6 86%, CaO 46. 29%, Fe203 1.7.1%, MgO 2. 14%, P205 7, 7 1%, S03 5 '5 7%. Slowly add this solidifying agent powder to the prepared mixed solution of sodium hydroxide and barium sulfate, and at the same time, vigorously stir and mix to form a homogeneous slurry. The curing agent / slurry weight ratio used was 0.5 4. Stirring was stopped ten minutes after the curing agent was added, and then the slurry was poured into a cylindrical polyethylene plastic model having an inner diameter of 5 cm and a height of 11 cm, and then sealed and placed at room temperature. Thirty days later, the mold was demolded, and five samples were taken and cut into cylindrical samples of 10 cm ’, and then in accordance with the U.S. Nucl ear

Regulatory Commission (USN3RC) quality specifications require compressive strength testing in accordance with ASTM C39 procedures. The test results showed that the average compressive strength of 5 samples was 50 kg / cm2. In addition, in accordance with China's low-level radioactive waste quality standards, the water-resistant compressive strength (ie, the compressive strength after 90 days of immersion in water) was measured to be 81 kg / cra2, and the weathering compressive strength (after being placed at a temperature of ~ 1) The compressive strength after 30 cycles between 0 ° C to + 60 ° C and 60% to 95% relative humidity was 48 kg / cm2. Example 2: Take 373 parts of 98% sodium hydroxide and dissolve them in 2038 parts of water, add 1167 parts of powdered resin (P0W (iex)) and stir thoroughly for 30 minutes, and mix into a homogeneous slurry. Prepare and solidify as in the procedure of Example 1. Powder, the curing agent prepared

.Page 12 4 ^ 925〇-„„,… ·, _ _ 丨 V. Description of the Invention (7)

The analysis shows that the main ingredients are as follows: Si〇ii 23. 2%, A1203 4. 59%, CaO 61. 19%, Fe: ^ 3. 79%, MgO 2. 88%, p205 2. 2%, S03 is 1.58% ° and is cured in the same manner as in Example 1. The curing agent / slurry weight ratio used is 0.887. The cured samples were demoulded after being left for 30 days in the same manner, and a test was also performed on five samples. The results showed that the compressive strength was 5 9 kg / cm2 'the weather resistance compressive strength was 72 kg / cm2 and the water-resistant compressive strength was It is 11 3 kg / cna2. Example 3: Take 482 parts of sodium hydroxide dissolved in 1800 parts of water, add 1418 parts of barium sulfate and 1 3 5 4 parts of powdered resin, and mix by stirring. The curing agent powder was prepared according to the procedure of Example 1. The analysis of the prepared curing agent showed that its main components were as follows: Si02 36. 05%, Al2 03. 72¾, CaO 38. 61%, Fe2〇a 1 '43%. , MgO 1.79%, P205 61%, $ 〇3 4.65%. The curing was performed in the same manner as in Example 1. The weight ratio of the curing agent / slurry used was 0. 25. After 30 days of curing, the average compressive strength of the cured body was 58 kg / cin2, and the weathering compressive strength. It is 64 kg / cm2 and the compressive strength of water resistance is i 丄 kg / cm2. Example 4: Take 580 parts of sodium hydroxide dissolved in 2346 parts of water, add 1285 parts of barium sulfate and 1 449 parts of powdery resin , Stir well and mix. The curing agent powder was prepared according to the procedure of Example 1. The analysis of the prepared curing agent showed the following components: Si 02 30. 72%, Al2 03. 08%, CaO 41.0%, Fe203 2. 5 4 %, MgO 1. 9 3%, P205 1 9. 2 8%, S03 1.0 0 6% 〇 and curing as in Example 1, the curing agent / slurry weight ratio used is

Page 13 V. Description of the invention (8) 0,389. After 30 days, the average measured compressive strength of the cured body was 39 kg / cIfl2, and the weathering compressive strength was 56 kg / cm2. 'The water compressive strength was 53 kg / c. ®2. Example 5: Take 2765 parts of radioactive sodium sulfate waste liquid (20wt%) from the Second Nuclear Plant of Taiwan Company and put it into a beaker, and add barium hydroxide (Ba (OH) z · 8H2〇) powder 1 2 2 6 under stirring. After the conversion to form a mixed solution of barium sulfate and sodium hydroxide, 1745 parts of water were evaporated by heating, and 864 parts of powdered resin was added to prepare a mixed slurry, followed by stirring at room temperature and cooling to 3 ( After pc, the same curing agent as in Example 3 was added, and the weight ratio of curing agent / slurry used was 0 '389. After 30 days, the average compressive strength of five cured bodies was measured to be 43 kg / cm2. The compressive strength is 46 kg / cm2, and the water-resistant compressive strength is 46 kg / cm2. The leaching indexes of c0_60, Cs-134, and Cs ~ 137 measured according to the method specified in ANSI 16 · 1 are 8. 34, 6, 27 and 6. 32.

Page 14

Claims (1)

6. Jingjing Patent Scope 1'—A method for co-curing a sodium sulfate solution with a waste ion exchange resin 'The procedure includes (1) converting the sodium sulfate solution into a slurry of sodium hydroxide and barium hydroxide; (2) The above slurry is mixed with the ion exchange resin to form mixed waste; (3) The cement and the borosol materials such as blast furnace slag powder, fly ash and oxides of metals of two or more valences are used. One or several kinds of formulated powder curing agent such as salt or the like, 'this curing agent powder is mixed with the mixed waste of step (2) uniformly' and left to solidify. 2 ‘The method as claimed in the scope of the first patent application, wherein the water content of the slurry obtained in step (1) is less than 50%. 3'The method as claimed in the scope of the 1st or 2nd patent application, wherein the metal salt in the curing agent used is a compound such as a borate, a silicate, a phosphate, or a silicon phosphate. 4. The method as claimed in the scope of the 1st or 2nd patent application, wherein the metal oxide or salt in the curing agent component used is an oxide of calcium, silicon, magnesium, aluminum, iron, titanium, zirconium or the like Salt. 5. The method as claimed in the scope of the first or second patent application, wherein the pozzolanic materials in the curing agent component are silica fume, blast furnace slag powders, or Fly ash. 6. The method as claimed in the scope of the fifth patent application, wherein the weight ratio of the curing agent / waste solution used is 1 or less. 7. The method as claimed in the scope of the fifth patent application, wherein the temperature when the waste is mixed with the curing agent is below 90 ° C. Page 15