Method for determining the complete transformation of complex an-based nitrate solutions under a radioactive system

Abstract

The application discloses a method for determining complete transformation of complex Am-based nitrate solution under a radioactive system, and belongs to the technical field of radioactive waste liquid treatment. The method for transforming the radioactive Am-based nitrate solution comprises the following steps: concentrating the radioactive Am-based nitrate solution to obtain nitrate concentrate solid; and then calcining the nitrate concentrate solid at 700-750 DEG C. Meanwhile, the application also provides a method for determining complete transformation of complex Am-based nitrate solution under a radioactive system. The application solves the problem of how to transform the long-life and high-toxicity transuranium element stream into an oxide; the method is beneficial to temporary storage of the element, facilitates reuse of the element in the future, and provides a method for identifying whether the transformation of the element nitrate solution is complete or not.

Description

Technical Field

[0001] This invention relates to the field of radioactive waste treatment technology, specifically to a method for determining the complete transformation of complex americium nitrate solutions in a radioactive system. Background Technology

[0002] High-level waste (HLW) is one of the most difficult forms of nuclear waste to manage, primarily existing as liquid waste (wastewater). Although HLW accounts for less than 1% of the total volume of nuclear waste generated in the nuclear fuel cycle, it contains over 99% of the total radioactivity of the nuclear fuel cycle. After separation using TRPO, HLW yields transuranic nuclide solutions (Am, Np, Pu, and Cm). These transuranic nuclide solutions are long-lived, highly radioactive, highly toxic, and dilute nitrate solutions (as shown in Table 1).

[0003] Table 1. Composition of americium nitrate solution after separation of high-level radioactive waste from power reactor.

[0004] <![CDATA[Ce 3+ ]]> 234 <![CDATA[Eu 3+ ]]> 13.5 <![CDATA[Fe 3 ]]> 23.7 <![CDATA[Gd 3+ ]]> 19 <![CDATA[La 3+ ]]> 120 <![CDATA[Mo 6+ ]]> 44 <![CDATA[Nd 3+ ]]> 400.5 <![CDATA[Pd 2+ ]]> 148.47 <![CDATA[Pr 3+ ]]> 112 <![CDATA[Ru 6+ ]]> 45 <![CDATA[Sm 3+ ]]> 74 <![CDATA[Sn 2+ ]]> 8.5 Te 48 <![CDATA[Y 3+ ]]> 44.5 <![CDATA[Zr 4+ ]]> 71 <![CDATA[Np 4+ ]]> 58.37 <![CDATA[Pu 4+ ]]> 1.51 <![CDATA[Am 3+ ]]> 64.16 <![CDATA[Cm 3+ ]]> 7.69 <![CDATA[Tc 7+ ]]> 71.5 medium <![CDATA[2 mol / L HNO3 0.2 mol / L oxalic acid]]>

[0005] To facilitate temporary storage and subsequent extraction of useful nuclides, this solution needs to be completely converted into oxides (generally, an oxidation rate of 98% is considered complete conversion). However, the complex composition, low concentration, inconsistent conversion temperatures of nitrates for different elements, the tendency of some nitrates to volatilize upon calcination leading to radioactive loss, and the potential for explosion all impose stringent requirements on its enrichment conditions and conversion temperatures. How to achieve the conversion of complex transuranic nuclide streams and determine whether the conversion is complete is a pressing issue that needs to be addressed. Summary of the Invention

[0006] To facilitate the temporary storage of transuranic nuclide stream solutions after high-level radioactive waste separation and enable future reuse of the nuclides, they must be converted into stable oxides. This invention provides a method for determining the complete conversion of complex americium nitrate solutions in a radioactive system. This invention not only provides a method for converting radioactive americium nitrate solutions but also a method for determining whether the conversion is complete.

[0007] This invention first provides a method for converting radioactive americium nitrate solutions, comprising the following steps:

[0008] The radioactive americium nitrate solution was concentrated to obtain a nitrate concentrate solid; then it was calcined at 700-750℃.

[0009] In the above-mentioned method for converting radioactive americium nitrate solution, the concentration is carried out at 80-90°C.

[0010] In the above-mentioned method for converting radioactive americium nitrate solution, the calcination time is 1-3 hours; specifically, it can be 1 hour.

[0011] The calcination is carried out in an air atmosphere;

[0012] The heating rate for calcination is 5-10℃ / min.

[0013] In the above-mentioned method for converting radioactive americium nitrate solution, the metal ions in the radioactive americium nitrate solution include the following: Ce 3+ The concentration is 0-2000 mg / L, Eu 3+ The concentration is 10-100 mg / L, Fe 3+ The concentration is 0-100 mg / L, Gd 3+ The concentration is 0-100 mg / L, La 3+ The concentration is 0-500 mg / L, Mo 6+ The concentration is 0-200 mg / L, Nd 3+ The concentration of Pd is 0-2000 mg / L. 2+ The concentration is 0-1000 mg / L, Pr 3+ The concentration is 0-1000 mg / L, Ru 6+ The concentration is 0-1200 mg / L, Sm 3+ The concentration is 0-500 mg / L, Sn 2+ The concentration is 0-50 mg / L, Te 6+ The concentration is 0-300 mg / L, Y 2+ The concentration of Zr is 0-200 mg / L. 4+ The concentration is 0-500 mg / L, Np 4+ The concentration is 0-300 mg / L, Pu 4+ The concentration is 0-50 mg / L, Am 3+ The concentration is 0-300 mg / L, Cm 3+ The concentration is 0-30 mg / L, Tc 7+ The concentration is 0-500 mg / L.

[0014] This invention also provides a method for determining the complete transformation of complex americium nitrate solutions in a radioactive system, comprising the following steps:

[0015] (1) The radioactive americium nitrate solution was concentrated to obtain a nitrate concentrate solid; then it was calcined at 700℃ for 1 hour to obtain the mass of the sample after calcination at 700℃ for 1 hour, denoted as Δm. 700-1 ;

[0016] (2) The sample calcined in step (1) was calcined at 700℃ for 1 hour to obtain the mass of the sample after calcination at 700℃ for 2 hours, which is denoted as Δm. 700-2 ;

[0017] (3) The sample calcined in step (2) is calcined at 700℃ for another 1 hour to obtain the mass of the sample after calcination at 700℃ for 3 hours, which is denoted as Δm. 700-3 ;

[0018] (4) Continue calcining the sample after step (3) at 725℃ for 1 hour to obtain the mass of the sample after calcination at 725℃ for 1 hour, denoted as Δm. 725-1 ;

[0019] (5) Continue calcining the sample after step (4) at 750℃ for 1 hour to obtain the mass of the sample after calcination at 750℃ for 1 hour, denoted as Δm. 750-1 ;

[0020] (6) Δm 700-2 Divide by Δm 700-1 Multiply by 100% to obtain the conversion rate R of radioactive americium nitrate solution between calcination at 700℃ for 2 hours and calcination at 700℃ for 1 hour. 700-1 ;

[0021] Δm 700-3 Divide by Δm 700-1 Multiply by 100% to obtain the conversion rate R of radioactive americium nitrate solution between calcination at 700℃ for 3 hours and calcination at 700℃ for 1 hour. 700-2 ;

[0022] Δm 725-1 Divide by Δm 700-1 Multiply by 100% to obtain the conversion rate R of radioactive americium nitrate solution between calcination at 725℃ for 1 h and calcination at 700℃ for 1 h. 725-1 ;

[0023] Δm 750-1 Divide by Δm 700-1 Multiply by 100% to obtain the conversion rate R of radioactive americium nitrate solution between calcination at 750℃ for 1 h and calcination at 700℃ for 1 h. 750-1 .

[0024] In the above determination method, when R 700-1 R 700-2 R 725-1 R 750-1 If at least one of the values ​​reaches 99% or higher, it indicates that the radioactive americium nitrate solution is completely converted under these conditions.

[0025] In the above determination method, the concentration is concentrated at 80-90℃.

[0026] In the above-described determination method, the calcination is carried out in an air atmosphere.

[0027] In the above determination method, the heating rate of calcination is 5-10℃ / min, specifically 5℃ / min.

[0028] In the above-mentioned method for converting radioactive americium nitrate solution, the metal ions in the radioactive americium nitrate solution include the following: Ce 3+ The concentration is 0-2000 mg / L, Eu 3+ The concentration is 10-100 mg / L, Fe 3+ The concentration is 0-100 mg / L, Gd 3+ The concentration is 0-100 mg / L, La 3+ The concentration is 0-500 mg / L, Mo 6+ The concentration is 0-200 mg / L, Nd 3+ The concentration of Pd is 0-2000 mg / L. 2+ The concentration is 0-1000 mg / L, Pr 3+ The concentration is 0-1000 mg / L, Ru 6+ The concentration is 0-1200 mg / L, Sm 3+ The concentration is 0-500 mg / L, Sn 2+ The concentration is 0-50 mg / L, Te 6+ The concentration is 0-300 mg / L, Y 2+ The concentration of Zr is 0-200 mg / L. 4+ The concentration is 0-500 mg / L, Np 4+ The concentration is 0-300 mg / L, Pu 4+ The concentration is 0-50 mg / L, Am 3+ The concentration is 0-300 mg / L, Cm 3+ The concentration is 0-30 mg / L, Tc 7+ The concentration is 0-500 mg / L.

[0029] The present invention has the following beneficial effects:

[0030] This invention first provides a method for transforming complex americium nitrate solutions in a radioactive system, and uses multiple calcinations to identify whether the radioactive nitrate transformation is complete; this invention solves the problem of how to transform long-lived and highly toxic transuranic nuclides into oxides; the method of this invention facilitates the temporary storage of nuclides, making it convenient for future reuse of nuclides, and also provides a method for identifying whether the transformation of nuclides into nitric acid solutions is complete. Detailed Implementation

[0031] The present invention will be further described in detail below with reference to specific embodiments. The embodiments given are only for illustrating the present invention and are not intended to limit the scope of the present invention.

[0032] Unless otherwise specified, the experimental methods described in the following examples are conventional methods.

[0033] Unless otherwise specified, the quantitative experiments in the following examples are all repeated three times, and the results are averaged.

[0034] Unless otherwise specified, all materials and reagents used in the following examples are commercially available.

[0035] The composition of the simulated americium nitrate solution used in the following examples is shown in Table 2, and the composition of the radioactive americium nitrate solution is shown in Table 3.

[0036] Table 2. Composition and reagents of simulated americium nitrate solution

[0037] <![CDATA[Ce 3+ ]]> 936 <![CDATA[Ce(NO3)3·6H2O]]> <![CDATA[Eu 3+ ]]> 54 <![CDATA[Eu2O3]]> <![CDATA[Fe 3+ ]]> 94.8 <![CDATA[Fe(NO3)3·9H2O]]> <![CDATA[Gd 3+ ]]> 76 <![CDATA[Gd2O3]]> <![CDATA[La 3+ ]]> 480 <![CDATA[La2O3]]> <![CDATA[Mo 6+ ]]> 176 <![CDATA[(NH4)6Mo7O 24 ·4H2O]]> <![CDATA[Nd 3+ ]]> 1602 <![CDATA[Nd2O3]]> <![CDATA[Pd 2+ ]]> 593.88 92g / L.aq.Pd <![CDATA[Pr 3+ ]]> 448 <![CDATA[Pr6O 11 ]]> <![CDATA[Ru 6+ ]]> 180 13.11%.aq.Ru <![CDATA[Sm 3+ ]]> 296 <![CDATA[Sm2O3]]> <![CDATA[Sn 2+ ]]> 34 <![CDATA[Na2SnO3·3H2O]]> Te 192 <![CDATA[H6TeO6]]> <![CDATA[Y 3+ ]]> 178 <![CDATA[Y(NO3)3·6H2O]]> <![CDATA[Zr 4+ ]]> 284 <![CDATA[Zr(NO3)4·3H2O]]> medium 2 mol / L nitric acid + 0.2 mol / L oxalic acid

[0038] Table 3 Composition of radioactive americium nitrate solution

[0039] <![CDATA[Ce 3+ ]]> 1250 <![CDATA[Eu 3+ ]]> 77.2 <![CDATA[Fe 3+ ]]> 0 <![CDATA[Gd 3+ ]]> 57.9 <![CDATA[La 3+ ]]> 0 <![CDATA[Mo 6+ ]]> 0 <![CDATA[Nd 3+ ]]> 1953 <![CDATA[Pd 2+ ]]> 663 <![CDATA[Pr 3+ ]]> 565 <![CDATA[Ru 6+ ]]> 1007 <![CDATA[Sm 3+ ]]> 425 <![CDATA[Sn 2+ ]]> 0 Te 0 <![CDATA[Y 3+ ]]> 0 <![CDATA[Zr 4+ ]]> 0 <![CDATA[Np 4+ ]]> 222 <![CDATA[Pu 4+ ]]> 0 <![CDATA[Am 3+ ]]> 178 <![CDATA[Cm 3+ ]]> 14.6 <![CDATA[Tc 7+ ]]> 374

[0040] Example 1

[0041] (1) First, take two quartz crucibles and calcine them at 750℃. After cooling, repeat the calcine process twice. Weigh the crucibles and mark the mass as m. 1-0 m 2-0 Prepare 100 mL of a simulated americium nitrate solution according to the composition of Table 2; add 15 mL of the prepared simulated solution to each of the two crucibles, concentrate at 80°C until no liquid is visible, and obtain a nitrate concentrate solid; heat to 700°C at a rate of 5°C / min in air atmosphere, hold at this temperature for 1 hour, allow to cool naturally to room temperature, weigh, and mark the mass as m. 1-700-1 m 2-700-1 m 1-700-1 m 2-700-1 and m 1-0 m 2-0 The difference is the mass of the sample after calcination at 700℃ for 1 hour, denoted as Δm. 1-700-1 Δm 2-700-1 The results are shown in Table 4.

[0042] (2) The above sample was then calcined at 700℃ for another hour, cooled, and weighed. The mass was marked as m. 1-700-2 m 2-700-2 m 1-700-2 m 2-700-2 and m 1-0 m2-0 The difference is the mass of the sample after calcination at 700℃ for 2 hours, denoted as Δm. 1-700-2 Δm 2-700-2 The results are shown in Table 4.

[0043] (3) The above sample was calcined again at 700℃ for 1 hour, cooled and weighed, and the mass was marked as m. 1-700-3 m 2-700-3 m 1-700-3 m 2-700-3 and m 1-0 m 2-0 The difference is the mass of the sample after calcination at 700℃ for 3 hours, denoted as Δm. 1-700-3 Δm 2-700-3 The results are shown in Table 4.

[0044] (4) Continue to calcine the above sample at a higher temperature and observe whether its mass changes. The temperature is increased from room temperature to 725℃ at a rate of 5℃ / min in air atmosphere, held for 1 hour, and then allowed to cool naturally to room temperature. The mass is recorded as m. 1-725-1、 m 2-725-1 m 1-725-1、 m 2-725-1 and m 1-0 m 2-0 The difference is the mass of the sample after calcination at 725℃ for 1 hour, denoted as Δm. 1-725-1 ,Δm 2-725-1 The above sample was then further heated, and in an air atmosphere, the temperature was increased from room temperature to 750℃ at a rate of 5℃ / min, held at that temperature for 1 hour, and then allowed to cool naturally to room temperature. The sample was then weighed, and the mass was recorded as m. 1-750-1、 m 2-750-1 m 1-750-1、 m 2-750-1 and m 1-0 m 2-0 The difference is the mass of the sample after calcination at 750℃ for 1 hour, denoted as Δm. 1-750-1 Δm 2-750-1 The results are shown in Table 5.

[0045] Δm 1-700-2 Δm 2-700-2 respectively with Δm 1-700-1 Δm 2-700-1 Dividing by the ratio yields the transformation rate R of the simulated solution after calcination at 700℃ for 2 hours and 700℃ for 1 hour. 1-700-1、 R 2-700-1 ; will Δm 1-700-3 Δm 2-700-3 respectively with Δm 1-700-1 Δm 2-700-1 Dividing by the ratio yields the transformation rate R of the simulated solution after calcination at 700℃ for 3 hours and 700℃ for 1 hour. 1-700-2、 R2-700-2 ;Δm 1-725-1 Δm 2-725-1 respectively with Δm 1-700-1 Δm 2-700-1 Dividing by the ratio yields the transformation rate R of the simulated solution after calcination at 725℃ for 1 hour and at 700℃ for 1 hour. 1-725-1、 R 2-725-1 ; will Δm 1-750-1 Δm 2-750-1 respectively with Δm 1-700-1 Δm 2-700-1 Dividing by the ratio yields the transformation rate R of the simulated solution after calcination at 750℃ for 1 hour and at 700℃ for 1 hour. 1-750-1、 R 2-750-1 The corresponding results are shown in Tables 4 and 5, where samples 1 and 2 are parallel samples. As can be seen from the data in Tables 4 and 5, the parallelism between the two samples is excellent. Comparing the conversion rates using calcination at the same temperature for different times and calcination at different temperatures for different times, the conversion rates are almost consistently above 99.7%, fully meeting the requirements for stable temporary storage.

[0046]

[0047] Table 4 Comparison of transformation rates of simulated americium nitrate solution-converted samples after calcination at 700℃ for different times.

[0048]

[0049] Table 5 Comparison of transformation rates of simulated americium nitrate solution-transformed samples calcined at different temperatures for 1 hour.

[0050]

[0051] Example 2

[0052] First, take two quartz crucibles and calcine them at 750℃. After cooling, repeat the calcine process twice. Weigh the crucibles and mark the mass as m. 3-0 m 4-0 Prepare 50 mL of radioactive americium nitrate solution according to the composition of Table 3 (medium: 2 mol / L HNO3 and 0.2 mol / L oxalic acid); take 15 mL of each solution and place them in crucibles No. 3 and No. 4 respectively, and concentrate them at 80°C until no liquid is visible, obtaining nitrate concentrate solid; repeat the calcination process of Example 1, and the corresponding results are shown in Tables 6 and 7. The data in Tables 6 and 7 show that the parallel effect of the two radioactive samples is very good. Comparing the conversion rate using calcination at the same temperature for different times and calcination at different temperatures for different times, the conversion rate is almost consistent, both reaching over 99.6%, which fully meets the requirements for stable temporary storage.

[0053] Table 6 Comparison of conversion rates of radioactive americium nitrate solution-converted samples after calcination at 700℃ for different times.

[0054]

[0055] Table 7 Comparison of conversion rates of radioactive americium nitrate solution-converted samples after calcination at different temperatures for 1 hour.

[0056]

[0057] Comparative Example 1

[0058] This example is intended to illustrate the importance of calcination time.

[0059] (1) First, take two quartz crucibles and calcine them at 750℃. After cooling, repeat the calcine process twice. Weigh the crucibles and mark the mass as m. 5-0 m 6-0 Take 3 mL of the solution prepared in Example 1 and dilute it 5 times. Place it in crucibles No. 5 and No. 6 and concentrate it at 80°C until no liquid is visible to obtain nitrate concentrate solid. Heat it to 700°C at a rate of 5°C / min in air atmosphere, keep it at that temperature for 0.5 hours, cool it naturally to room temperature, and weigh it. The results are shown in Table 8.

[0060] (2) The above samples were calcined at 700℃ for another hour, cooled and weighed. The results are shown in Table 8.

[0061] (3) The above samples were calcined again at 700℃ for 1 hour, cooled and weighed. The results are shown in Table 8.

[0062] Table 8. Comparison of sample mass changes before and after calcination at different times after initial calcination of simulated americium nitrate solution-transformed samples at 700℃ for 0.5 hours.

[0063]

[0064] As can be seen from the results in Table 8, the transformation rate is only about 97.5%, which is less than the 98% transformation rate. Therefore, the initial calcination condition of holding the calcination at 700℃ for 0.5 hours cannot be considered as the process condition for complete transformation.

Claims

1. A method for determining the complete transformation of a complex americium nitrate solution in a radioactive system, comprising the following steps: (1) The radioactive americium nitrate solution was concentrated to obtain a nitrate concentrate solid; then it was calcined at 700℃ for 1 hour to obtain the mass of the sample after calcination at 700℃ for 1 hour, which is denoted as Δm. 700-1 ; (2) The sample calcined in step (1) is calcined at 700℃ for 1 hour to obtain the mass of the sample after calcination at 700℃ for 2 hours, which is denoted as Δm. 700-2 ; (3) The sample calcined in step (2) is calcined at 700℃ for 1 hour to obtain the mass of the sample after calcination at 700℃ for 3 hours, which is denoted as Δm. 700-3 ; (4) The sample calcined in step (3) is calcined at 725℃ for 1 hour to obtain the mass of the sample after calcination at 725℃ for 1 hour, which is denoted as Δm. 725-1 ; (5) Continue calcining the sample after step (4) at 750℃ for 1 hour to obtain the mass of the sample after calcination at 750℃ for 1 hour, denoted as Δm. 750-1 ; (6) Δm 700-2 Divide by Δm 700-1 Multiply by 100% to obtain the conversion rate R of radioactive americium nitrate solution between calcination at 700℃ for 2 hours and calcination at 700℃ for 1 hour. 700-1 ; Δm 700-3 Divide by Δm 700-1 Multiply by 100% to obtain the conversion rate R of radioactive americium nitrate solution between calcination at 700℃ for 3 hours and calcination at 700℃ for 1 hour. 700-2 ; Δm 725-1 Divide by Δm 700-1 Multiply by 100% to obtain the conversion rate R of radioactive americium nitrate solution between calcination at 725℃ for 1 h and calcination at 700℃ for 1 h. 725-1 ; Δm 750-1 Divide by Δm 700-1 Multiply by 100% to obtain the conversion rate R of radioactive americium nitrate solution between calcination at 750℃ for 1 h and calcination at 700℃ for 1 h. 750-1 ; When R 700-1 R 700-2 R 725-1 R 750-1 If at least one of the values ​​reaches 99% or higher, it indicates that the radioactive americium nitrate solution is completely converted under these conditions; The concentration is carried out at 80-90°C; The calcination is carried out in an air atmosphere; The heating rate for calcination is 5-10℃ / min; The metal ions in the radioactive americium nitrate solution include the following: Ce 3+ The concentration is 0-2000 mg / L, Eu 3+ The concentration is 10-100 mg / L, Fe 3+ The concentration is 0-100 mg / L, Gd 3+ The concentration is 0-100 mg / L, La 3+ The concentration is 0-500 mg / L, Mo 6+ The concentration is 0-200 mg / L, Nd 3+ The concentration of Pd is 0-2000 mg / L. 2+ The concentration is 0-1000 mg / L, Pr 3+ The concentration is 0-1000 mg / L, Ru 6+ The concentration is 0-1200 mg / L, Sm 3+ The concentration is 0-500 mg / L, Sn 2+ The concentration is 0-50 mg / L, Te 6+ The concentration is 0-300 mg / L, Y 2+ The concentration of Zr is 0-200 mg / L. 4+ The concentration is 0-500 mg / L, Np 4+ The concentration is 0-300 mg / L, Pu 4+ The concentration is 0-50 mg / L, Am 3+ The concentration is 0-300 mg / L, Cm 3+ The concentration is 0-30 mg / L, Tc 7+ The concentration is 0-500 mg / L.

Images