CN104004927A - Process for purifying zirconium in Purex flow plutonium purification cycle - Google Patents

Process for purifying zirconium in Purex flow plutonium purification cycle Download PDF

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CN104004927A
CN104004927A CN201410236283.XA CN201410236283A CN104004927A CN 104004927 A CN104004927 A CN 104004927A CN 201410236283 A CN201410236283 A CN 201410236283A CN 104004927 A CN104004927 A CN 104004927A
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plutonium
purification
zirconium
concentration
purification cycle
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CN104004927B (en
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肖松涛
罗方祥
刘协春
杨贺
兰天
孟照凯
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China Institute of Atomic of Energy
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China Institute of Atomic of Energy
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Abstract

The invention belongs to the technical field of spent fuel post-treatment, and discloses a process for purifying zirconium in a Purex flow plutonium purification cycle. 30% tri-butyl-phosphate (TBP)-kerosene is adopted as an extraction agent 2AX in a 2A extractor, so as to recover uranium and plutonium and purify fission fragments. The process comprises an extraction section and a washing section; and the concentration of a nitric acid in a 2AF feed liquid is 3.5-3.7mol/L, and 2AS is an HNO3 solution of which the concentration is 0.8-0.85mol/L. The process has the advantages that the plutonium yield is greater than 99.9%, and the purification coefficient of zirconium is greater than 100.

Description

The purification process of zirconium in Purex flow process plutonium purification cycle
Technical field
The invention belongs to spent fuel post-processing technology field, be specifically related to the purification process of zirconium in Purex flow process plutonium purification cycle.
Background technology
Spent fuel refers in nuclear reactor, and irradiation draws off after reaching the specific burn up of plan discharging from heap, and the nuclear fuel of use in this heap no longer.It is carried out to chemical treatment, to remove the impurity such as fission product and to reclaim fissile nuclide and fertile nuclide and some can be utilized the process of material, be called spent fuel aftertreatment.At present, various countries' spent fuel aftertreatment flow process mainly adopts Purex flow process or its improved flow process.It mainly comprises codecontamination partitioning cycle, plutonium purification cycle and three circulations of uranium purification cycle.
In the fission product of spent fuel, zirconium (Zr) yield is higher, account for gross activity than great, as 235u initial enrichment be 3.25% UO 2nuclear fuel element, when irradiation burnup is 33GWd/tU, cooling 3 years, the content of Zr was 3500g/tU.In spent fuel last handling process, after processing, codecontamination section (df of Zr is generally greater than to 10 3), a small amount of Zr is extracted by tributyl phosphate (TBP) together with plutonium with uranium, and in uranium plutonium separating technology, disperses to enter uranium purifying cycle and plutonium purification cycle.Because flow process is higher to the purity requirement of plutonium in final plutonium product, the whole process gross decontamination coefficient general requirement of the fission products such as Zr, Ru is greater than to 10 6.Therefore,, in plutonium purification cycle, on the basis of plutonium yield, need to further separate zirconium guaranteeing.
In current open source literature, relevant Zr is at HNO 3extraction behavior in solution has been reported, but is the experimental study of the above zirconium extraction process of gram liter level, research be the behavior of Zr in uranium plutonium coextraction process.And have not yet to see the report of Zr in plutonium purification cycle.
In the research work of plutonium purification cycle, find that Zr is difficult to reach the decontamination index (DF of expection zr>100).And in plutonium purification cycle and codecontamination cycle, the purification of Zr has some serious difference: 1) in codecontamination cycle, Zr concentration (0.35g/gPu) is far above the Zr concentration (0.22mg/gPu) in Pu purification cycle, and concentration differs approximately 1600 times; 2) organic phase uranium plutonium saturation ratio higher (saturation ratio approximately 75%) in codecontamination cycle, be beneficial to the purification of Zr, and organic phase uranium plutonium saturation ratio lower (saturation ratio is less than 15%) in Pu purification cycle is unfavorable for the purification of Zr; 3) there is Zr (NO in codecontamination cycle 3) 4, TcO 4-coextraction, there is not TcO in Pu purification cycle 4-.Therefore, in plutonium purification cycle, the purification difficulty of micro-Zr is also increased greatly.
Summary of the invention
(1) goal of the invention
According to the existing problem of prior art, the invention provides the purification process of trace zirconium in a kind of Purex flow process, this technique is for plutonium purification cycle, and has plutonium yield and be greater than 99.9% and the df of the zirconium feature that is greater than 100.
(2) technical scheme
In order to solve the existing problem of prior art, the present invention is achieved by the following technical solutions:
The purification process of zirconium in plutonium purification cycle, this technique is with 30%TBP-kerosene, as extraction agent 2AX, to realize the recovery of uranium plutonium and the purification of fission product in 2A extractor, it comprises extraction section and washing section, and key is, in 2AF feed liquid, the concentration of nitric acid is 3.5~3.7mol/L; 2AS is that concentration is the HNO of 0.8~0.85mol/L 3solution.
Preferably, the extraction progression of described extraction section is 8~10 grades, and the washing progression of washing section is 6~8 grades.
Preferably, in described extraction section, the stream ratio of 2AF:2AX is 4~6.
Preferably, this technique at room temperature operates.
(3) beneficial effect
The purification process of zirconium in plutonium purification cycle, this technique is difficult to meet the high uranium plutonium rate of recovery and high zirconium df simultaneously.Adopt the purification process of zirconium in plutonium purification cycle provided by the invention, its have plutonium yield higher than 99.9% and the df of zirconium higher than 100 feature, this be mainly due to:
(1) in 2AF feed liquid, the concentration of acid is chosen as 3.5~3.7mol/L, though the range of choice of this concentration is narrow, only in this concentration range, guarantee uranium plutonium yield and zirconium enter water.Because the high extraction that is conducive to plutonium and uranium of acid concentration in 2AF feed liquid, but can increase the reservation of zirconium in organic phase simultaneously, therefore, concentration is chosen as 3.5~3.7mol/L.
(2) concentration of 2AS nitric acid is 0.8~0.85mol/L, in this concentration range, concentration can guarantee the purification to fission products such as zirconium and rutheniums lower than 0.85mol/L on the one hand, also can not cause because concentration of nitric acid is too low on the other hand the hydrolysis of plutonium in washing section and follow-up 2B technique.
(3) the few and stream of washing progression than minor benefit in uranium plutonium extraction, but also can increase the reservation of zirconium in organic phase, therefore washing progression is chosen as 6~8 grades, the stream of 2AF:2AX is than 4~6.
Accompanying drawing explanation
Fig. 1 is Zr concentration profiles at different levels.
Embodiment
Below in conjunction with specification drawings and specific embodiments, the present invention is further elaborated.
Embodiment 1
In temperature, be under the condition of 25 ℃, adopt mixing section volume 12ml, the mixer-settler that clarifying chamber's volume is 18ml is as 2A extraction tank, and organic phase is about 2:1 with the ratio of water, simulation plutonium purification cycle.The Pu of consisting of of 2AF feed liquid: 6.28g/L wherein 4+, the UO2 of 0.74g/L 2+, the HNO of 3.5mol/L 3and the Zr of 0.3073mg/L (adding U target to facilitate the analysis of carrying out Zr); 2AX is 30%TBP-kerosene; 2AS is that concentration is the nitric acid of 0.8mol/L; Feed liquid is 1min in the mixing section residence time, and extraction progression is 8 grades, and washing progression is 7 grades, and the stream of 2AF:2AX:2AS is than being 4:1:0.45.
During experiment, first with not uranium-bearing, plutonium and zirconium feed liquid, fill groove two hours, then add the feed liquid of uranium-bearing, plutonium and zirconium, after operation 5.0h, each gets up-to-date style at a flash for 2 hours, after operation 16h, stops groove analysis.
After balance, the yield of plutonium is 99.96%, and the material balance of uranium is 97.4%, and the material balance of nitric acid is 105.8%, and the material balance of plutonium is 98.2%, shows experimentation operational excellence, and experimental result is reliable.
In the instantaneous sample of 2AW and 2AP, Zr concentration analysis, in Table 1, owing to containing uranium, plutonium in test, can not adopt ICP-MS to analyze, therefore sneak into radioactivity in Zr 95zr, counts and determines that Zr concentration in solution, its specific radioactivity are 251.67Bq/mg by measuring its γ.Material balance that after balance, instantaneous sample Zr is 90.6%, Zr in Table the material balance of 1, Zr is poor is that it is right due to the Pu that contains higher concentration in sample 95the accuracy tool that the gamma spectrum of Zr is measured has a certain impact, but according to the material balance of uranium, acid, plutonium, thinks that Zr approaches balance, data are reliable and have certain representativeness.
The instantaneous sample concentration of Zr after table 1 balance
The instantaneous sample of water c(Zr)/(μg/L) The instantaneous sample of organic phase c(Zr)/(μg/L)
2AW1 250.00 2AP1 5.24
2AW2 247.58 2AP2 6.24
2AW3 243.73 2AP3 6.20
2AW4 239.16 2AP4 6.16
2AW5 243.45 2AP5 7.15
2AW6 244.60 2AP6 8.38
Its concentration distribution at different levels are shown in Fig. 1, and as can be seen from Figure, few at organic phase exit end Zr content, these processing condition have realized the purification to sliver element zirconium preferably.And according to instantaneous sample zirconium concentration after balance, calculate the df DF of Zr zr=163.
By the thermal test of plutonium purification cycle stand, show: in the situation that guaranteeing that Pu yield is greater than 99.9%, the df of Zr is greater than 100, higher than design objective, meets the needs of spent fuel aftertreatment flow process.
Embodiment 2
Method, the step used with embodiment 1 are identical, and different is that in 2AF feed liquid, concentration of nitric acid is 3.7mol/L, and 2AS is that concentration is the nitric acid of 0.85mol/L; The extraction progression of extraction section is 10 grades, and the washing progression of washing section is 8 grades; The stream ratio of 2AF:2AX is 6.
The demonstration of plutonium purification cycle stand thermal test result, the df that Pu yield is 99.97%, Zr is 159.

Claims (4)

  1. The purification process of zirconium in 1.Purex flow process plutonium purification cycle, this technique is with 30%TBP-kerosene, as extraction agent 2AX, to realize the recovery of uranium plutonium and the purification of fission product in 2A extractor, it comprises extraction section and washing section, it is characterized in that, in 2AF feed liquid, the concentration of nitric acid is 3.5~3.7mol/L; 2AS is that concentration is the HNO of 0.8~0.85mol/L 3solution.
  2. 2. the purification process of zirconium in Purex flow process plutonium purification cycle according to claim 1, is characterized in that, the extraction progression of described extraction section is 8~10 grades, and the washing progression of washing section is 6~8 grades.
  3. 3. the purification process of zirconium in Purex flow process plutonium purification cycle according to claim 1, is characterized in that, in described extraction section, the stream of 2AF:2AX ratio is 4~6.
  4. 4. the purification process of zirconium in Purex flow process plutonium purification cycle according to claim 1, is characterized in that, the service temperature of this technique is room temperature.
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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106893878A (en) * 2017-03-02 2017-06-27 中国原子能科学研究院 A kind of method that plutonium is reclaimed in the spentnuclear fuel from radioactivity

Citations (3)

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CN1277725A (en) * 1997-10-31 2000-12-20 英国核燃料公共有限公司 Nuclear fuel reprocessing
CN101484226A (en) * 2006-07-03 2009-07-15 阿海珐核循环公司 Method for separating a chemical element from uranium (VI) using an aqueous nitric phase, in a uranium extraction cycle
CN103339269A (en) * 2010-11-25 2013-10-02 原子能和替代能源委员会 Process for separating americium from other metallic elements present in an acidic aqueous or organic phase and applications thereof

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN1277725A (en) * 1997-10-31 2000-12-20 英国核燃料公共有限公司 Nuclear fuel reprocessing
CN101484226A (en) * 2006-07-03 2009-07-15 阿海珐核循环公司 Method for separating a chemical element from uranium (VI) using an aqueous nitric phase, in a uranium extraction cycle
CN103339269A (en) * 2010-11-25 2013-10-02 原子能和替代能源委员会 Process for separating americium from other metallic elements present in an acidic aqueous or organic phase and applications thereof

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Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN106893878A (en) * 2017-03-02 2017-06-27 中国原子能科学研究院 A kind of method that plutonium is reclaimed in the spentnuclear fuel from radioactivity
CN106893878B (en) * 2017-03-02 2018-11-30 中国原子能科学研究院 A method of recycling plutonium from radioactivity spentnuclear fuel

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