Preparation method of radioactive strontium cesium glass ceramic solidified body

Abstract

The invention relates to a preparation method of a radioactive strontium cesium glass ceramic solidified body, which comprises the following steps: 1) uniformly mixing pollucite, granite, radioactive strontium and radioactive cesium in a solvent to obtain a mixture; 2) carrying out compression molding on the mixture to obtain a cured precursor; and 3) sintering the solidified body precursor to obtain the radioactive strontium cesium glass ceramic solidified body. By adopting the preparation method disclosed by the invention, the problems of fixation, volatilization and loss of cesium can be solved, and meanwhile, the obtained radioactive strontium-cesium glass ceramic solidified body can be applied to preparation of a cesium source core and improvement of reutilization of nuclear wastes, and also can be used for permanent treatment of strontium and cesium.

Description

Technical Field

[0001] The invention relates to a method for preparing a radioactive strontium-cesium glass ceramic solidified body, belonging to the technical field of industrial treatment and application of nuclear waste. Background Art

[0002] High-level waste (HLW) is one of the most difficult forms of nuclear waste to handle, and it mainly exists in the form of waste liquid (wastewater). Although the volume of HLW is less than 1% of the volume of nuclear waste produced by the nuclear fuel cycle, the radioactivity it contains exceeds 99% of the total radioactivity of the nuclear fuel cycle. Due to the complex composition and high volatility of HLW, it puts forward more stringent requirements on the adaptability (multi-nuclide, multi-component), inclusiveness (high solid solubility) and stability (mechanical, thermal and irradiation stability, etc.) of its solidification matrix.

[0003] For high-level radioactive waste, there are generally two solidification methods: glass and ceramic. Ceramic solidification bodies have high chemical stability, good thermal stability, high mechanical strength, and strong radiation resistance, but their preparation costs are high and the process is complicated. Glass solidification bodies have a simple solidification process, are easy to operate remotely, and have a wide range of tolerance, but their thermal stability and chemical durability are inferior to those of ceramic solidification bodies.

[0004] For radioactive elements in high-level waste, such as cesium and strontium, the existing ceramic solidification method is to add rocks, alkaline manganese ore, etc., grind and press them into shape, and generally need to be calcined in air at 1100℃-1500℃; cesium belongs to Group 1A and is difficult to fix. It generally exists in the form of cesium garnet in nature; however, cesium is generally easy to volatilize at temperatures exceeding 1000℃, causing radionuclide leakage. Therefore, there is an urgent need for a method that can both reduce the volatilization of cesium and obtain a more stable solidified body of cesium and strontium radioactive elements. Summary of the invention

[0005] Problem that the invention aims to solve

[0006] In order to solve the problems existing in the prior art, the present invention provides a method for preparing a radioactive strontium-cesium glass-ceramic solid body, which can solve the problems of fixation, volatilization and loss of cesium. At the same time, the obtained radioactive strontium-cesium glass-ceramic solid body can be used for the preparation of cesium source cores, improve the recycling of nuclear waste, and can also be used for the permanent disposal of strontium and cesium.

[0007] Solutions for solving problems

[0008] The present invention provides a method for preparing a radioactive strontium-cesium glass-ceramic solid body, comprising the following steps:

[0009] 1) mixing cesium garnet, granite, radioactive strontium and radioactive cesium in a solvent to obtain a mixture;

[0010] 2) pressing the mixture into a shape to obtain a solidified body precursor;

[0011] 3) Sintering the solidified body precursor to obtain a radioactive strontium-cesium glass-ceramic solidified body.

[0012] According to the preparation method of the present invention, in step 1), the mass ratio of the cesium garnet and the granite is cesium garnet:granite=1-2:8-9.

[0013] According to the preparation method of the present invention, the solvent in step 1) is ethanol.

[0014] According to the preparation method of the present invention, in step 2), the pressure of the pressing molding is 8-10 MPa, and the holding time is 5-10 minutes.

[0015] According to the preparation method of the present invention, in step 3), the sintering temperature is 1000-1200° C., and the holding time is 1-2 hours.

[0016] According to the preparation method of the present invention, in step 3), the sintering is performed under an inert atmosphere.

[0017] According to the preparation method of the present invention, in step 3), the heating rate of the sintering is 5-10° C. / min.

[0018] Effects of the Invention

[0019] The preparation method of the radioactive strontium-cesium glass-ceramic solid body of the present invention uses artificially synthesized cesium garnet and granite as a base material to solidify strontium and cesium radioactive substances under relatively mild conditions; the present invention solves the problem of volatilization of radioactive cesium under high temperature conditions, and at the same time, the obtained radioactive strontium-cesium glass-ceramic solid body has good chemical stability, which is a good solution to the separation of high-level waste liquid. 137 Cs, 90 This laid the foundation for the solidification problem of Sr. BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Figure 1 XRD diffraction test pattern of the solidified body-I prepared in Example 1. DETAILED DESCRIPTION

[0021] Various exemplary embodiments, features and aspects of the present invention will be described in detail below. The word "exemplary" used here means "used as an example, embodiment or illustrative". Any embodiment described here as "exemplary" is not necessarily interpreted as being superior or better than other embodiments.

[0022] In addition, in order to better illustrate the present invention, numerous specific details are provided in the following specific embodiments. It should be understood by those skilled in the art that the present invention can be implemented without certain specific details. In other examples, methods, means, equipment and steps well known to those skilled in the art are not described in detail in order to highlight the subject matter of the present invention.

[0023] Unless otherwise stated, the units used in this specification are all international standard units, and the numerical values ​​and numerical ranges appearing in the present invention should be understood to include the inevitable systematic errors in industrial production.

[0024] In this specification, the word "may" includes both performing a certain process and not performing a certain process.

[0025] In this specification, the references to "some specific / preferred embodiments", "other specific / preferred embodiments", "embodiments", etc., mean that the specific elements (e.g., features, structures, properties and / or characteristics) described in connection with the embodiments are included in at least one embodiment described herein, and may or may not exist in other embodiments. In addition, it should be understood that the elements may be combined in various embodiments in any suitable manner.

[0026] In this specification, the numerical range expressed using "a numerical value A to a numerical value B" means a range including the endpoints numerical values ​​A and B.

[0027] In this specification, "room temperature" or "normal temperature" means "10-40°C".

[0028] The present invention provides a method for preparing a radioactive strontium-cesium glass-ceramic solid body, comprising the following steps:

[0029] 1) mixing cesium garnet, granite, radioactive strontium and radioactive cesium in a solvent to obtain a mixture;

[0030] 2) pressing the mixture into a shape to obtain a solidified body precursor;

[0031] 3) Sintering the solidified body precursor to obtain a radioactive strontium-cesium glass-ceramic solidified body.

[0032] Due to its inherent spatial pore structure, cesium and strontium are both alkali metals that can solidify synergistically. Granite is one of the most stable rocks in nature, and its main components are aluminum oxide and silicon oxide. The two combine to form a glass-ceramic phase structure.

[0033] The glass-ceramic phase structure of the present invention combines the excellent thermal and chemical stability of the ceramic phase with the high inclusiveness of the glass phase.

[0034] According to the preparation method of the present invention, in step 1), the mass ratio of the cesium garnet and the granite is cesium garnet:granite=1-2:8-9.

[0035] According to the preparation method of the present invention, the solvent in step 1) is ethanol.

[0036] According to the preparation method of the present invention, in step 2), the pressure of the pressing molding is 8-10 MPa, and the holding time is 5-10 minutes, preferably the pressure is 8 MPa, and the holding time is 10 minutes.

[0037] According to the preparation method of the present invention, in step 3), the sintering temperature is 1000-1200° C., and the holding time is 1-2 hours.

[0038] According to the preparation method of the present invention, in step 3), the sintering is performed under an inert atmosphere.

[0039] According to the preparation method of the present invention, in step 3), the heating rate of sintering is 5-10°C / min, preferably 5°C / min.

[0040] Example

[0041] Preparation Example 1

[0042] 5 liters of simulated strontium-cesium high-level waste liquid was prepared according to the contents in Table 1, and then evaporated to dryness, and dried at 100° C. for 6 h to obtain simulated strontium-cesium nitrate solid.

[0043] Table 1 Simulated strontium-cesium high-level waste liquid (where the anion is NO3 - )

[0044] element Simulated liquid mg / L <![CDATA[Ba 2+ ]]> 379 <![CDATA[Cs + ]]> 449 <![CDATA[Fe 3+ ]]> 0.19 <![CDATA[Mo 6+ ]]> 27 <![CDATA[Na + ]]> 11.4 <![CDATA[Pd 2+ ]]> 0.606 <![CDATA[Rb 2+ ]]> 69 <![CDATA[Sr 2+ ]]> 142 <![CDATA[HNO3]]> 0.3mol / L

[0045] Preparation Example 2

[0046] Alumina-silicate molecular sieve (the molecular sieve is a sodium-type aluminosilicate produced by Tianjin Nanhua Catalyst Co., Ltd., and the SiO2 / Al2O3 molar ratio in the molecular sieve is 5.2:1) and simulated strontium cesium nitrate solid are mixed uniformly in a mass ratio of 70:30, heated to 700°C at a heating rate of 5°C / min in an air atmosphere, kept warm for 1 hour, and naturally cooled to room temperature to obtain cesium garnet.

[0047] Example 1

[0048] Weigh 0.1 g of the dried cesium garnet obtained in Preparation Example 2 and 0.9 g of granite; add 1×10 6 Bq Cs and 2×10 6 Bq Sr, add 1.5 ml of anhydrous ethanol, mix well to obtain a mixture;

[0049] The mixture was pressed at 8 MPa for 10 minutes to obtain a solidified precursor;

[0050] The solidified body precursor was placed in a graphite crucible, and then placed in a quartz tube furnace, and heated to 1200°C at a rate of 5°C / min under an inert atmosphere, kept warm for 1 hour, and naturally cooled to room temperature to obtain a radioactive strontium-cesium glass ceramic solidified body, which was recorded as solidified body-1. During the calcination process, the tail gas was absorbed with 0.5 mol / L nitric acid, and then the quartz tube was cleaned 3 times with 0.5 mol / L nitric acid to obtain the final absorption liquid, which was recorded as absorption liquid-I.

[0051] Example 2

[0052] Weigh 0.2 g of the dried cesium garnet obtained in Preparation Example 2 and 0.8 g of granite, add 1×10 6 Bq Cs and 2×10 6 Bq Sr, add 1.5 ml of anhydrous ethanol, mix well to obtain a mixture;

[0053] The mixture was pressed at 10 MPa for 5 minutes to obtain a solidified precursor;

[0054] The solidified body precursor was placed in a graphite crucible, and then placed in a quartz tube furnace, and heated to 1000°C at a rate of 10°C / min under an inert atmosphere, kept warm for 2 hours, and naturally cooled to room temperature to obtain a radioactive strontium-cesium glass ceramic solidified body, which was recorded as solidified body-II. During the calcination process, the tail gas was absorbed with 0.5 mol / L nitric acid, and then the quartz tube was cleaned 3 times with 0.5 mol / L nitric acid to obtain the final absorption liquid, which was recorded as absorption liquid-II.

[0055] Example 3

[0056] Weigh 0.15 g of the dried cesium garnet obtained in Preparation Example 2 and 0.85 g of granite, add 1×10 6 Bq Cs and 2×10 6 Bq Sr, add 1.5 ml of anhydrous ethanol, mix well to obtain a mixture;

[0057] The mixture was pressed at 8 MPa for 10 minutes to obtain a solidified precursor;

[0058] The solidified body precursor was placed in a graphite crucible, and then placed in a quartz tube furnace, and heated to 1100°C at a rate of 8°C / min under an inert atmosphere, kept warm for 2 hours, and naturally cooled to room temperature to obtain a radioactive strontium-cesium glass ceramic solidified body, which was recorded as solidified body-III. During the calcination process, the tail gas was absorbed with 0.5 mol / L nitric acid, and then the quartz tube was cleaned 3 times with 0.5 mol / L nitric acid to obtain the final absorption liquid, which was recorded as absorption liquid-III.

[0059] XRD test

[0060] The crystal structure of the solid body was tested using Japanese Rigaku model miniflex600, using CuKa rays (wavelength ), step size 0.02°, test range 2theta 10°-80°. Figure 1 is the crystal structure diagram of Example 1, Figure 1 It can be seen that the material structure of the solidified body-I is a glass-ceramic structure, which has a glass amorphous phase structure and sharp diffraction peaks of crystals.

[0061] Chemical stability test

[0062] According to the American ASTM C1220-2017 standard, the name of the standard is "Standard Test Method for Static Leaching of Single Waste Body for Radioactive Waste Treatment", the method is summarized as follows: a sample with a known geometric surface area (S) is immersed in a leaching container containing a known volume (V) of leaching agent, and the container is sealed and placed in a constant temperature box, and kept static at a set temperature for a specified time. After reaching the specified time, the container is taken out of the constant temperature box, cooled to room temperature, opened, sampled, acidified, and radioactivity tested; this patent is leached at 90°C for 14 days to examine the chemical stability. The normalized leaching rates of strontium and cesium are shown in the following table, and the test results of the volatilization rates of strontium and cesium in absorption liquid-I, absorption liquid-II, and absorption liquid-III are shown in the following table.

[0063] Normalized leaching rate of strontium Normalized leaching rate of cesium Volatility of Strontium The volatility of cesium Example 1 <![CDATA[6.036×10 -4 g / m 2 .d]]> <![CDATA[5.271×10 -4 g / m 2 .d]]> 0.05％ 0.25％ Example 2 <![CDATA[7.216×10 -4 g / m 2 .d]]> <![CDATA[5.316×10 -4 g / m 2 .d]]> 0.05％ 0.24％ Example 3 <![CDATA[8.418×10 -4 g / m 2 .d]]> <![CDATA[3.905×10 -4 g / m 2 .d]]> 0.05％ 0.25％

[0064] It should be noted that, although the technical solution of the present invention is introduced with specific examples, those skilled in the art will appreciate that the present invention should not be limited thereto.

[0065] The embodiments of the present invention have been described above, and the above description is exemplary, not exhaustive, and is not limited to the disclosed embodiments. Many modifications and variations will be apparent to those of ordinary skill in the art without departing from the scope and spirit of the described embodiments. The selection of terms used herein is intended to best explain the principles of the embodiments, practical applications, or technical improvements in the market, or to enable other persons of ordinary skill in the art to understand the embodiments disclosed herein.

Claims

1. A method for preparing a radioactive strontium-cesium glass-ceramic solid body, characterized in that: The steps include: 1) mixing cesium garnet, granite, radioactive strontium and radioactive cesium in a solvent to obtain a mixture; 2) pressing the mixture into a shape to obtain a solidified body precursor; 3) Sintering the solidified body precursor to obtain a radioactive strontium-cesium glass-ceramic solidified body.

2. The preparation method according to claim 1, characterized in that: In step 1), the mass ratio of the cesium garnet and the granite is cesium garnet:granite=1-2:8-9.

3. The preparation method according to claim 1 or 2, characterized in that: The solvent in step 1) is ethanol.

4. The preparation method according to claim 1 or 2, characterized in that: In step 2), the pressure of the pressing process is 8-10 MPa, and the holding time is 5-10 minutes.

5. The preparation method according to claim 1 or 2, characterized in that: In step 3), the sintering temperature is 1000-1200° C., and the holding time is 1-2 hours.

6. The preparation method according to claim 1 or 2, characterized in that: In step 3), the sintering is performed under an inert atmosphere.

7. The preparation method according to claim 1 or 2, characterized in that: In step 3), the heating rate of sintering is 5-10°C / min.

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