Process for integrated extraction of strontium and americium from high-level liquid waste

Abstract

The present application relates to the nuclear chemical technology field, especially to the integrated process for extracting strontium and americium from high-level liquid waste, which uses N, N, N'N'-tetraoctyl-3-oxypentanediamide (TODGA) as an extractant, and provides a new liquid-liquid extraction process with two cycles, which includes a strontium extraction cycle and an americium extraction cycle, and can extract strontium and americium from high-level liquid waste at the same time. The process of the present application includes two process links of the americium extraction cycle and the strontium extraction cycle; the americium extraction cycle includes three process steps of extracting americium, washing americium and stripping americium in sequence; the strontium extraction cycle includes three process steps of extracting strontium, washing strontium and stripping strontium in sequence.

Description

Technical Field

[0001] This invention relates to the field of nuclear chemical technology, and in particular to a process for the integrated extraction of strontium and americium from high-level radioactive waste. Background Technology

[0002] Spent fuel, after being processed through the PUREX process, produces highly radioactive and acidic high-level radioactive waste (HLLW). Its composition is complex, containing minor actinides (americium and curium, etc.) and fragmented elements (strontium, cesium, lanthanides, zirconium, molybdenum, palladium, iron, etc.). However, some radionuclides contained in HLLW have high application value and can be used in military, medical, and other fields. Strontium-90 (90Sr) is a pure beta radionuclide nuclide, and its decay product yttrium-90 is an important radioactive source for medical treatment. Strontium-90 is also a high-temperature test nuclide, serving as a heat source for nuclear batteries, providing energy for nuclear batteries in deep-sea exploration and harsh environments. Americium-241 / 243 is an alpha source and can be used in thickness gauges, level gauges, thermometers, ionization smoke detectors, and artificial element target materials. Extracting Strontium-90 and Americium-241 / 243 from HLLW is a prerequisite for fully utilizing their economic value. However, due to the complex composition of high-level radioactive waste liquid, it is extremely difficult to separate and extract strontium and americium from it.

[0003] Americium extraction is a technology of interest to many countries. France uses DMDBTDMA or DMDOHEMA as extractants to develop the DIAMX extraction process; the United States uses T2EHDGA to extract lanthanides and actinides, and then uses DTPA to extract lanthanides and actinides to obtain americium products; Japan, India, and the United States are researching the use of N,N,N'N'-tetraoctyl-3-oxopramethylenediamide (TODGA) as an extractant to obtain americium. Strontium extraction technology research mainly focuses on the extraction and separation using crown ether extractants and diamide podyl ether extractants. Although there is currently a large amount of research on strontium and americium extraction, most technologies remain at the basic research stage and have not yet been successfully industrialized.

[0004] To achieve the extraction of strontium and americium, it is necessary to design and invent a process that is simple, uses readily available reagents, and is highly feasible for industrialization. This process should simultaneously extract strontium and americium, reducing the complexity of reagents and lowering the difficulty of engineering. This is of great significance for the current extraction of strontium and americium. Summary of the Invention

[0005] To address the aforementioned problems, the present invention aims to provide a process for the integrated extraction of strontium and americium from high-level radioactive waste. This invention uses N,N,N'N'-tetraoctyl-3-oxopramethylenediamide (TODGA) as the extractant, providing a novel liquid-liquid extraction process with two cycles. This process includes a strontium extraction cycle and an americium extraction cycle, enabling the simultaneous extraction of strontium and americium from high-level radioactive waste. The process of this invention comprises two steps: an americium extraction cycle and a strontium extraction cycle. The americium extraction cycle sequentially includes three steps: americium extraction, americium washing, and americium back-extraction. The strontium extraction cycle sequentially includes three steps: strontium extraction, strontium washing, and strontium back-extraction.

[0006] The objective of this invention can be achieved through the following technical solutions:

[0007] This invention provides a process for the integrated extraction of strontium and americium from high-level radioactive waste liquid, comprising the following steps:

[0008] (S1) The high-level radioactive waste liquid was extracted using the TODGA-TBP-kerosene extraction system to obtain the first organic phase and the first aqueous phase;

[0009] The first organic phase contains americium, lanthanides, and some fragmented elements, while the first aqueous phase contains strontium, cesium, iron, ruthenium, and molybdenum.

[0010] (S2) The first organic phase obtained in step (S1) is washed sequentially with a high-acid solution containing oxalic acid and a low-acid solution to remove some lanthanide elements and fragment impurity elements. Then, the first organic phase is back-extracted with SO3-Ph-BTP to obtain the second organic phase and the second aqueous phase.

[0011] In this process, americium is back-extracted to the second aqueous phase, while lanthanides remain in the second organic phase, thus achieving the extraction of americium.

[0012] (S3) The second aqueous phase was extracted using the TODGA-TBP-kerosene extraction system to obtain a third organic phase containing strontium and a third aqueous phase containing fragmented impurity elements;

[0013] (S4) The third organic phase obtained in step (S3) is washed with nitric acid, and then the third organic phase is back-extracted with a back-extracting agent to obtain a strontium-containing extract, thereby achieving the extraction of strontium.

[0014] In one embodiment of the present invention, the TODGA-TBP-kerosene extraction system is obtained by mixing TODGA, TBP and kerosene.

[0015] In one embodiment of the present invention, in the TODGA-TBP-kerosene extraction system, the concentration of TODGA is 0.03 mol / L to 0.08 mol / L, and the concentration of TBP is 0.3 mol / L to 0.6 mol / L.

[0016] In one embodiment of the present invention, in step (S1), the high-level radioactive waste liquid is the high-level radioactive waste liquid generated in the PUREX process of spent fuel reprocessing, and contains nitric acid with a concentration of 2.5 mol / L to 4 mol / L.

[0017] In one embodiment of the present invention, in step (S1), the volume ratio of the TODGA-TBP-kerosene extraction system to the high-level radioactive waste liquid is 1:1 to 1:3.

[0018] In one embodiment of the present invention, in step (S2), the composition of the highly acidic solution containing oxalic acid is 0.1 mol / L to 0.5 mol / L oxalic acid and 2 mol / L to 3 mol / L nitric acid;

[0019] The low-acid solution is a nitric acid solution with a concentration of 0.4 mol / L to 0.8 mol / L.

[0020] The concentration of SO3-Ph-BTP is 0.01 mol / L to 0.05 mol / L, and the environmental nitric acid concentration of SO3-Ph-BTP is 0.2 mol / L to 0.8 mol / L.

[0021] In one embodiment of the present invention, in step (S2), the volume ratio of the highly acidic solution containing oxalic acid to the first organic phase is 1:1 to 3:1;

[0022] The volume ratio of the low-acid solution to the first organic phase is 1:1 to 3:1;

[0023] The volume ratio of SO3-Ph-BTP to the first organic phase is 1:1 to 1:1.5.

[0024] In one embodiment of the present invention, in step (S3), the concentration of TODGA in the TODGA-TBP-kerosene extraction system is 0.2 mol / L to 0.35 mol / L, and the concentration of TBP is 0.4 mol / L to 0.6 mol / L.

[0025] The volume ratio of the TODGA-TBP-kerosene extraction system to the first aqueous phase is 1:1 to 1:3.

[0026] In one embodiment of the present invention, in step (S4), the concentration of the nitric acid is 0.8 mol / L to 1.0 mol / L;

[0027] The volume ratio of nitric acid to the third organic phase is 1:1 to 1:3.

[0028] In one embodiment of the present invention, in step (S4), the stripping agent is selected from one of disodium ethylenediaminetetraacetate (EDTA-2Na), citric acid, or diethyltriaminepentaacetic acid (DTPA);

[0029] When the stripping agent is disodium ethylenediaminetetraacetate, its concentration is 0.01 mol / L to 0.03 mol / L; when the stripping agent is citric acid, its concentration is 0.01 mol / L to 0.03 mol / L; when the stripping agent is diethyltriaminepentaacetic acid, its concentration is 0.01 mol / L to 0.02 mol / L.

[0030] The volume ratio of the stripping agent to the third organic phase is 1:1 to 1:3.

[0031] Compared with the prior art, the present invention has the following beneficial effects:

[0032] The process provided by this invention can simultaneously extract strontium and americium in one process. The extractant system is simple and it is a completely new process. The process of this invention contains only two extraction cycles (strontium and americium), which is simple and conducive to industrialization. This invention uses SO3-Ph-BTP as the back-extraction agent for the americium extraction cycle, which can achieve the separation of lanthanides and actinides in one cycle. Attached Figure Description

[0033] Figure 1 This is a process flow diagram of the integrated extraction of strontium and americium from high-level radioactive waste liquid according to the present invention;

[0034] Figure 2 This is a process flow diagram of the integrated extraction of strontium and americium from high-level radioactive waste liquid in Example 1. Detailed Implementation

[0035] This invention provides a process for the integrated extraction of strontium and americium from high-level radioactive waste liquid, comprising the following steps:

[0036] (S1) The high-level radioactive waste liquid was extracted using the TODGA-TBP-kerosene extraction system to obtain the first organic phase and the first aqueous phase;

[0037] The first organic phase contains americium, lanthanides, and some fragmented elements, while the first aqueous phase contains strontium, cesium, iron, ruthenium, and molybdenum.

[0038] (S2) The first organic phase obtained in step (S1) is washed sequentially with a high-acid solution containing oxalic acid and a low-acid solution to remove some lanthanide elements and fragment impurity elements. Then, the first organic phase is back-extracted with SO3-Ph-BTP to obtain the second organic phase and the second aqueous phase.

[0039] In this process, americium is back-extracted to the second aqueous phase, while lanthanides remain in the second organic phase, thus achieving the extraction of americium.

[0040] (S3) The second aqueous phase was extracted using the TODGA-TBP-kerosene extraction system to obtain a third organic phase containing strontium and a third aqueous phase containing fragmented impurity elements;

[0041] (S4) The third organic phase obtained in step (S3) is washed with nitric acid, and then the third organic phase is back-extracted with a back-extracting agent to obtain a strontium-containing extract, thereby achieving the extraction of strontium.

[0042] In one embodiment of the present invention, the TODGA-TBP-kerosene extraction system is obtained by mixing TODGA, TBP and kerosene.

[0043] In one embodiment of the present invention, in the TODGA-TBP-kerosene extraction system, the concentration of TODGA is 0.03 mol / L to 0.08 mol / L, and the concentration of TBP is 0.3 mol / L to 0.6 mol / L.

[0044] In one embodiment of the present invention, in step (S1), the high-level radioactive waste liquid is the high-level radioactive waste liquid generated in the PUREX process of spent fuel reprocessing, and contains nitric acid with a concentration of 2.5 mol / L to 4 mol / L.

[0045] In one embodiment of the present invention, in step (S1), the volume ratio of the TODGA-TBP-kerosene extraction system to the high-level radioactive waste liquid is 1:1 to 1:3.

[0046] In one embodiment of the present invention, in step (S2), the composition of the highly acidic solution containing oxalic acid is 0.1 mol / L to 0.5 mol / L oxalic acid and 2 mol / L to 3 mol / L nitric acid;

[0047] The low-acid solution is a nitric acid solution with a concentration of 0.4 mol / L to 0.8 mol / L.

[0048] The concentration of SO3-Ph-BTP is 0.01 mol / L to 0.05 mol / L, and the environmental nitric acid concentration of SO3-Ph-BTP is 0.2 mol / L to 0.8 mol / L.

[0049] In one embodiment of the present invention, in step (S2), the volume ratio of the highly acidic solution containing oxalic acid to the first organic phase is 1:1 to 3:1;

[0050] The volume ratio of the low-acid solution to the first organic phase is 1:1 to 3:1;

[0051] The volume ratio of SO3-Ph-BTP to the first organic phase is 1:1 to 1:1.5.

[0052] In one embodiment of the present invention, in step (S3), the concentration of TODGA in the TODGA-TBP-kerosene extraction system is 0.2 mol / L to 0.35 mol / L, and the concentration of TBP is 0.4 mol / L to 0.6 mol / L.

[0053] The volume ratio of the TODGA-TBP-kerosene extraction system to the first aqueous phase is 1:1 to 1:3.

[0054] In one embodiment of the present invention, in step (S4), the concentration of the nitric acid is 0.8 mol / L to 1.0 mol / L;

[0055] The volume ratio of nitric acid to the third organic phase is 1:1 to 1:3.

[0056] In one embodiment of the present invention, in step (S4), the stripping agent is selected from one of disodium ethylenediaminetetraacetate (EDTA-2Na), citric acid, or diethyltriaminepentaacetic acid (DTPA);

[0057] When the stripping agent is disodium ethylenediaminetetraacetate, its concentration is 0.01 mol / L to 0.03 mol / L; when the stripping agent is citric acid, its concentration is 0.01 mol / L to 0.03 mol / L; when the stripping agent is diethyltriaminepentaacetic acid, its concentration is 0.01 mol / L to 0.02 mol / L.

[0058] The volume ratio of the stripping agent to the third organic phase is 1:1 to 1:3.

[0059] The present invention will now be described in detail with reference to the accompanying drawings and specific embodiments.

[0060] Unless otherwise specified, all reagents used in the following embodiments are commercially available reagents, and all detection methods and techniques used are conventional detection methods and techniques in the art.

[0061] Example 1

[0062] This embodiment provides a process flow for the integrated extraction of strontium and americium from high-level radioactive waste liquid, such as... Figure 1 and Figure 2 As shown, the specific steps include:

[0063] (S1) Extraction of americium: The high-level radioactive waste liquid generated by the spent fuel reprocessing plant was extracted using a TODGA-TBP-kerosene extraction system (TODGA concentration of 0.08 mol / L and TBP concentration of 0.5 mol / L) to obtain the first organic phase and the first aqueous phase.

[0064] Americium, along with lanthanides and some fragmented elements, are extracted into the first organic phase, while strontium, cesium, iron, ruthenium, molybdenum, and other elements enter the extraction residue (the first aqueous phase). The ratio of the two phases is 1:1.

[0065] (S2) Washing americium: The first organic phase obtained in step (S1) is washed sequentially with an oxalic acid solution containing 3 mol / L nitric acid (oxalic acid concentration is 0.5 mol / L) and a 0.5 mol / L dilute nitric acid solution to remove some lanthanide elements (including lanthanum, cerium, praseodymium and neodymium) and some fragmented elements (including zirconium, strontium and molybdenum); wherein the ratio of the two phases in the two washes is 1:1.

[0066] (S3) Back-extraction of americium: Then, the first organic phase washed by back-extraction step (S2) is obtained using 0.015 mol / L SO3-Ph-BTP (the ambient nitric acid concentration of SO3-Ph-BTP is 0.5 mol / L) to obtain the second organic phase and the second aqueous phase;

[0067] In this process, americium is back-extracted to the second aqueous phase (labeled as americium product), while heavy lanthanide elements (including promethium, samarium, europium, gadolinium, terbium, etc.) remain in the second organic phase, thus achieving the extraction of americium.

[0068] Steps (S1), (S2) and (S3) are the americium extraction cycle.

[0069] (S4) Extraction of strontium: The first aqueous phase obtained in step (S1) was extracted using a TODGA-TBP-kerosene extraction system (TODGA concentration of 0.3 mol / L and TBP concentration of 0.5 mol / L), resulting in a third organic phase and a third aqueous phase.

[0070] Strontium is extracted into the third organic phase, while a large number of fragmented impurity elements (including cesium, iron, molybdenum, ruthenium, sodium, etc.) enter the third aqueous phase.

[0071] (S5) Washing strontium: Wash the third organic phase obtained in step (S4) with 1.0 mol / L nitric acid; wherein the ratio of the two phases is 1:1.

[0072] (S6) Strontium back-extraction: The third organic phase after washing in step (S5) is back-extracted using 0.015 mol / L EDTA-2Na back-extraction agent to obtain a strontium-containing extract (strontium product), thus achieving the extraction of strontium;

[0073] The ratio of the two is 1:1.

[0074] Steps (S1), (S2) and (S3) are the strontium extraction cycle.

[0075] The composition of the products at each stage is shown in Table 1.

[0076] Table 1 Elemental Content Table

[0077]

[0078]

[0079] As can be seen from Table 1, the process flow of this implementation can achieve integrated extraction of strontium and americium from high-level radioactive waste liquid.

[0080] The above description of the embodiments is provided to enable those skilled in the art to understand and use the invention. It will be apparent to those skilled in the art that various modifications can be made to these embodiments, and the general principles described herein can be applied to other embodiments without inventive effort. Therefore, the present invention is not limited to the above embodiments, and any improvements and modifications made by those skilled in the art based on the interpretation of the present invention, without departing from the scope of the invention, should be within the protection scope of the present invention.

Claims

1. A process for the integrated extraction of strontium and americium from high-level radioactive waste liquid, characterized in that, Includes the following steps: (S1) The high-level radioactive waste liquid was extracted using the TODGA-TBP-kerosene extraction system to obtain the first organic phase and the first aqueous phase; The first organic phase contains americium, lanthanides, and some fragmented elements, while the first aqueous phase contains strontium, cesium, iron, ruthenium, and molybdenum. (S2) The first organic phase obtained in step (S1) is washed sequentially with a high-acid solution containing oxalic acid and a low-acid solution to remove some lanthanide elements and fragment impurity elements. Then, the first organic phase is back-extracted with SO3-Ph-BTP to obtain the second organic phase and the second aqueous phase. In this process, americium is back-extracted to the second aqueous phase, while lanthanides remain in the second organic phase, thus achieving the extraction of americium. (S3) The first aqueous phase was extracted using the TODGA-TBP-kerosene extraction system to obtain a third organic phase containing strontium and a third aqueous phase containing fragmented impurity elements; (S4) Wash the third organic phase obtained in step (S3) with nitric acid, and then back-extract the third organic phase with a back-extracting agent to obtain a strontium-containing extract, thereby achieving the extraction of strontium; The TODGA-TBP-kerosene extraction system is obtained by mixing TODGA, TBP and kerosene. In step (S1), the concentration of TODGA in the TODGA-TBP-kerosene extraction system is 0.03 mol / L to 0.08 mol / L, and the concentration of TBP is 0.3 mol / L to 0.6 mol / L; the volume ratio of the TODGA-TBP-kerosene extraction system to the high-level radioactive waste liquid is 1:1 to 1:

3. In step (S2), the volume ratio of the highly acidic solution containing oxalic acid to the first organic phase is 1:1 to 3:1; the volume ratio of the low acidic solution to the first organic phase is 1:1 to 3:1; and the volume ratio of SO3-Ph-BTP to the first organic phase is 1:1 to 1:1.

5. In step (S3), the concentration of TODGA in the TODGA-TBP-kerosene extraction system is 0.2 mol / L to 0.35 mol / L, and the concentration of TBP is 0.4 mol / L to 0.6 mol / L; the volume ratio of the TODGA-TBP-kerosene extraction system to the first aqueous phase is 1:1 to 1:

3. In step (S4), the stripping agent is selected from one of disodium ethylenediaminetetraacetate, citric acid, or diethyltriaminepentaacetic acid; the volume ratio of the stripping agent to the third organic phase is 1:1 to 1:

3.

2. The process for integrated extraction of strontium and americium from high-level radioactive waste liquid according to claim 1, characterized in that, In step (S1), the high-level radioactive waste liquid is the high-level radioactive waste liquid generated in the PUREX process of spent fuel reprocessing, and contains nitric acid with a concentration of 2.5 mol / L to 4 mol / L.

3. The process for integrated extraction of strontium and americium from high-level radioactive waste liquid according to claim 1, characterized in that, In step (S2), the highly acidic solution containing oxalic acid consists of 0.1 mol / L to 0.5 mol / L oxalic acid and 2 mol / L to 3 mol / L nitric acid. The low-acid solution is a nitric acid solution with a concentration of 0.4 mol / L to 0.8 mol / L. The concentration of SO3-Ph-BTP is 0.01 mol / L to 0.05 mol / L, and the environmental nitric acid concentration of SO3-Ph-BTP is 0.2 mol / L to 0.8 mol / L.

4. The process for integrated extraction of strontium and americium from high-level radioactive waste liquid according to claim 1, characterized in that, In step (S4), the concentration of the nitric acid is 0.8 mol / L to 1.0 mol / L; The volume ratio of nitric acid to the third organic phase is 1:1 to 1:3.

Images