Removal of Fission Products and Their Complexing Agents by Potassium Dichromate Method from Kerosene Degraded with Nitric Acids

A washing method using potassium dichromate as oxidizing reagent was applied to remove fission products and their complexing agents from kerosene degraded with nitric acid.

The fission products and their complexing agents were both effectively removed from the degraded kerosene, their removal percentage increasing with rising concentration of sulfuric acid and potassium dichromate. The removal percentage of fission products also increased slightly with shaking time of the mixture of degraded kerosene and acidic potassium dichromate solution. Change in volume ratio (O/A) however hardly affected the removal percentage.

Lowering of the absorption bands due to carboxylic acids, nitrate esters and nitro compounds were observed in the infrared spectra of the degraded kerosene treated with acidic solution of potassium dichromate.

Infrared analysis of TBP/kerosene treated with acidic potassium dichromate solution showed that no chemical degradation of the solvent had occurred to any extent.     

Chemical Degradation of Kerosene Diluent with Nitric Acid

Chemical degradation of kerosene diluent with nitric, acid was studied to clarify its effect on uranium distribution ratio and fission product retention in the presence of degradation products. The decontamination of fission products retained in degraded kerosene was also investigated.

From the results of infrared spectrometry, it was recognized that nitro compounds, carboxylic acids, nitrate esters and nitroso compounds were formed as the main degradation products. The uranium distribution ratio in the extraction with TBP/degraded kerosene decreased with increasing concentration of nitric acid above 5 N, with rising temperature, and with increasing concentration of olefinic and aromatic hydrocarbons in the kerosene. It is suggested that the decrease of uranium distribution ratio may be due to the formation of carboxylic acids caused by the kerosene degradation. Some fission products, in particular ⁹⁵Zr-⁹⁵Nb and ¹³¹I, were retained in the organic phase, but ¹⁰⁶Ru-¹⁰⁶Rh did not remain after scrubbing with 3 N HNO₃. Fission product retention caused a decrease of uranium distribution ratio. Usual acid-alkali washing could not remove ⁹⁵Zr-⁹⁵Nb and ¹³¹I into the aqueous phase, hut ⁹⁵Zr-⁹⁵Nb was eliminated by oxalic acid washing.     

On Fission Product Retention of Degraded Kerosene with Nitric Acid

Determination of strong complexing species contained degradation products formed by the reaction of nitric acid on kerosene diluent was performed through: (I) observation of change in the absorbancy of nitroparaffines (at 1563 cm^-1), of carboxylic acids (at 1694cm^-1) and of nitrate esters (al 1640cm^-1) against γ-activity of ⁹⁵Zr^-95Nb extracted into the degraded kerosenes; (2) separation of the main complexing species from the degraded kerosene by an acid-alkali treatment; and (3) nitration of oleic acid with nitrogen oxide gases and observation of change in its extractability for ⁹⁵Zr-⁹⁵Nb.

It was conclusively established that nitroparaffines were among the main complexing species, and exhibited a strong retaining power on fission products, especially ⁹⁵Zr-⁹⁵Nb. Some possible retention mechanisms for fission products are proposed and discussed on the basis of tautomeric equilibria of nitroparaffines.     

Changes to Plutonium Extraction Behavior of TBP and Alkylamines through Irradiation

Changes to plutonium extraction properties brought about through irradiation of 30v/o TBP (Tri-n-butyl phosphate)/kerosene and 5v/o alkylamines/kerosene modified with lauryl alcohol were studied in such respects as extraction, scrubbing and stripping characteristics in nitrate media.

The alkylamines examined were tri-n-octyl amine (TOA), N-cyclohexyl dilauryl amine (N-CHDLA) and Amberlite LA-2 (LA-2). These extractante were irradiated to the extent of 10⁸R by ⁶⁰Co γ-ray, prior to extraction.

Marked changes with irradiation were observed in plutonium extraction performance with the TBP system tending to bring losses of plutonium, but very little change was found to occur with amine systems.

Calculation of the single stage decontamination factors of fission products from plutonium proved that separation deteriorated with irradiation in the TBP system but hardly changed in the amine systems. From these findings, tertiary amines, especially N-CHDLA, can be judged superior to TBP for the direct recovery of plutonium from irradiated fuels, a process that has to be carried out under high irradiation.

The phase separation time after mixing in the extraction stage varied very little with irradiation, and no formation of emulsion occurred in the extraction of tracer plutonium with either irradiated TBP or amines.     

钍-铀燃料后处理中新萃取剂的研究——Ⅳ.N-正辛基己内酰胺对主要裂片元素的萃取及γ辐照对萃取行为的影响

研究了N-正辛基己内酰胺(OCLA)从硝酸介质中对主要裂片元素Zr、Nb、Ru及Cs的萃取性质并和相同条件下的TBP萃取性质作比较。结果表明,OCLA的萃取性质类似于TBP,但在相同条件下,OCLA萃取主要裂片元素的分配系数要比TBP高。还研究了辐照对OCLA及TBP萃取性质的影响。OCLA的辐照稳定性比TBP好,特别是辐照对萃取锆的影响比TBP萃取锆的影响小得多。     

ABSTRACTS OF JAPANESE ARTICLES

Radiation damage to 30v/0 TBP/kerosene was investigated to determine changes in the extraction behavior of uranium and thorium with the solvent irradiated up to 10⁸ R in nitrate system and similarly in the stripping behavior with 0.01 N nitric acid.

The effect on uranium and thorium was discernible only with irradiations reaching 10⁸ R.

Changes in the behavior of fission products present in company with uranium or thorium were found to be the similar to the case where they existed free of uranium or thorium. At irradiations below 10⁷ R, uranium and thorium manifested loading effect, but it disappeared when irradiation reached 10⁸R.

Calculation of one stage decontamination factors of fission products from uranium and thorium confirmed deterioration of the power of separation with irradiation, and the degree of deterioration was determined quantitatively. The decontamination factor for ⁹⁵Zr-⁹⁵Nb was decreased to 1/2,000 by irradiation to 10⁸ R, while the same dosage of irradiation had little effect for ¹⁰⁶Ru-¹⁰⁶Rh.

Physical properties such as density, viscosity, emulsification tendency and phase separation time were also observed to be effected by irradiation to 10⁸ R.     

保留钌的强络合辐解产物

通过简单蒸馏、萃取分离、硅胶柱分离等手段对TBP萃取体系进行分离,并对分离的各组分进行钌的萃取保留实验,最终得到保留钌的强络合辐解产物.对强络合辐解产物进行了红外分析、元素分析、气相色谱-质谱和液相色谱-质谱分析,得出强络合辐解产物是含有亚硝酸酯基团的中性磷酸酯,并得出强络合辐解产物中三种组分为:C12 H28 O8P...     

硫酸铀酰体系中混合萃取剂的研究

试验考察了以7301,TBP,P204和醋酸丁脂 煤油组成的混合萃取体系对硫酸铀酰的萃取情况,同时分别考察了7301,TBP,P204和醋酸丁脂各组分对铀纯化效果的影响。通过小型试验、台架试验和扩大试验,筛选出混合萃取体系的最佳组成,同时确定了以黄饼为原料制备核电级U3O8的工艺流程和工艺参数。试验结果表明:醋酸丁脂虽有助于两相的分离,但溶解损失过大,不宜用作相改良剂;阳离子萃取剂P204可萃取一定量的阳离子杂质,不宜加入;中性分子萃取剂TBP与三脂肪胺一同使用时,其相改良剂的作用优于传统的高碳醇,需要加入;阴离子萃取剂7301可以萃取硫酸铀酰溶液中呈阴离子状态的UO2(SO4)32-。最终确定新混合萃取体系为7301 TBP的煤油溶液。     

On the Identification of Hydroxamic Acids formed by Nitric Acid Degradation of Kerosene and i-Dodecane

Identification of hydroxamic acids in chemically degraded kerosene and i-dodecane with nitric acid has been carried out by ferric chloride test to characterize these acids, infrared spectroscopy, visible ray absorption spectroscopy, and extraction of fission products and zirconium nitrate.

It is concluded from the above analytical results that small amounts of hydroxamic acids exist without doubt in both the degraded diluents. Their presence has also been evidenced from an examination of the chemical behavior of long chain alkyl hydroxamic acids such as stearyl hydroxamic acid. It is furthermore suggested that some of the precursors to the hydroxamic acids are olefines originally contained and/or formed by radiolysis of paraffines, naphtenes and aromatics in the diluent. With the use of octene-2, the process of formation of hydroxamic acid from olefine has also been estimated and is discussed on the basis of the results obtained.     

DHDECMP-TBP/煤油从模拟高放废液中萃取回收Am-Gd的研究

研究了ＤＨＤＥＣＭＰ－ＴＢＰ／煤油萃取Ａｍ＾３＋、Ｇｄ＾３＋的各影响因素,在单级萃取实验的基础上,用０．６０ｍｏｌ／ＬＤＨＤＥＣＭＰ－１．４０ｍｏｌ／ＬＴＢＰ／煤油为有机相对模拟高放废液进行了逆流串级萃取实验降流串级反萃实验,成功地从模拟高放废液中分离回收了Ａｍ＾３＋和Ｇｄ＾３＋。     

Uranium (IV)-(VI) Electron Exchange Reactions in Anion Exchange Resin,Tri-n-Octyl Amine and Tri-Butyl Phosphate

A study has been made of the U(IV)-U(VI) electron exchange reactions taking place between natural U(IV) and depleted U(VI) in anion exchange resin, as well as in TnOA/benzene and TBP/benzene systems.

The exchange rate in the anion exchange resin was smaller than the corresponding rates in 8–10 M HCl, which might be explained by considering that the diffusion of the exchangeable species is much slower in the anion exchange resin than in 8–10 M HCl.

The exchange rates in TnOA/benzene and in TBP/benzene were accelerated by decreasing the concentration of TnOA or TBP in benzene. The reason may be that TnOA and TBP, including the exchangeable species, is more easily diffused in dilute than in concentrated solution.

Based on activation energy values, the mechanism of exchange in the anion exchange resin was estimated to be similar to that in 8–10 M HCl solution, and the corresponding mechanism for TBP/benzene similar to that for the cation exchange resin. In the case of TnOA/benzene, the exchange process was presumed to resemble that of the anion exchange resin, judging from the similarity of ionic species extracted thereinto.     

Pulsed Neutron Experiment in Fast Natural Uranium Systems

Separation of fission products was carried out by solvent extraction using tri-n-butyl phosphate (TBP). ^{144, 144}Ce, ⁹¹Y and ⁹⁵Zr and ⁹⁵Nb were extracted with TBP from a freshly prepared nitric acid-potassium bromate solution. These nuclides in TBP were successively back-extracted with various aqueous solutions: ^{144, 144}Ce with hydrogen peroxide and nitric acid solution, ⁹¹Y with hydrochloric acid solution, and ⁹⁵Zr-⁹⁵Nb with oxalic acid solution. The other nuclides were not extracted by the TBP and remained in the nitric acid and potassium bromate solutions.     

Low-Temperature Partitioning of Plutonium with High U(VI)-Loading for Fuel Reprocessing

Measurement of the distribution ratios of Pu(IV), U(VI) and HNO₃ at low temperatures and its treatment with DIST code revealed that a high U (VI)-loading of 30% TBP in n-dodecane splits Pu(IV) down to the aqueous phase more strongly than do at 25°C. Based on these findings, flowsheet conditions to separate Pu(IV) from U(VI) were investigated with EXTRA.M code including the distribution equations obtained above. And tentative flowsheets for non-reductive Pu-splitting process at a temperature of 5°C were proposed for fuel reprocessing mainly based on the effects of U (VI)-loading in the solvent and temperature on distribution ratios of Pu(IV) and U(VI). Distribution ratios of the fission products, Zr, Nb, Ru and Ce were also measured to assess their decontamination from U or Pu products in the above process. Finally behavior of Np, in the proposed partitioning process was discussed by analysis with EXTRA. M code and a redox reaction model.     

Compression and Decompression Waves in Steam-Water System

The ratio of the γactivities per fission from fission products of ²³⁹Pu and ²³⁵U, and its time dependence were measured by double fission chamber technique. The γ-activity from the fission products of ²³⁹Pu fission was lower than the corresponding activity relevant to ²³⁵U fissions. The ratio varied with the cooling time allowed after irradition.

This ratio was applied to power distribution measurements by γ-scanning method in multi-region cores composed of PuO₂-UO₂ and UO₂ fuels. To obtain the relative power, the measured γ-activities from the fission products in the fuel rods were corrected for the difference between the γ-activities per fission from the fission products.     

Solubility of Tributylphosphate in Plutonium Nitrate Solution and Highly Radioactive Liquid Waste Solution

Abstract

The solubility of tri-n-butylphosphate (TBP) in aqueous solutions of plutonium nitrate (PuN) and in highly radioactive liquid waste (HRLW) of PUREX nuclear fuel reprocessing was investigated. By an empirical formula the solubility of TBP in PuN solutions was described in the range of 0–0. 1 M Pu and 1–8M HNO₃ concentrations. The following items were elucidated:

(1) The logarithm of TBP solubility (S) in the solution of interest varies inversely in proportion to the concentration of Pu(IV) in the range of 0–0.1M PU(IV) at a constant concentration of HNO₃, indicating that Pu(IV) simply behaves as an electrolyte for the salting-out of TBP. Log S subsequently levels off with increasing Pu concentration, which would be due to a change in the principal dissolution form of TBP having an interaction with Pu (IV).

(2) The variation in S in PuN solutions (0–0.1M PU) with nitric acid concentration shows almost the same tendency as that in HNO₃ solution.

(3) A dependency of S on fission product metal ions in HNO₃ for HRLW similar to that for PuN was observed.

(4) The logarithm of the ratio of TBP solubility in water to that in solution of interest was nearly proportional to l/T for HRLW solution or for low concentration of PuN solution. That deviates from the linear relation at high temperature when the concentration of PuN is increased, which can be explained by the change in ionic form of Pu.     

DRDECMP-TBP/煤油萃取性能的研究Ⅱ.对锕系-镧系元素的萃取

研究并测定了DRDECMP TBP/煤油对Am3 、Gd3 、UO2 2 的萃取分配比。研究结果表明 ,分配比随DRDECMP浓度或水相中HNO3浓度的增大而增大 ,随水相中Gd3 浓度的增大或温度的升高而降低 ;当有机相中TBP浓度增大时 ,Am3 、Gd3 的分配比略有下降 ,UO2 2 的分配比略有升高 ;酸度低时 ,Am3 和Gd3 的分配比低 ,可实现低酸反萃取 ;而低酸下UO2 2 的分配比较高 ,采用H2 C2 O4 等配位剂可有效降低其分配比 ,实现配合反萃取。     

Solvent Extraction of Americium(VI) by Tri-n-Butyl Phosphate

Solvent extraction of Am(VI) by tri-n-butyl phosphate (TBP) from nitric acid solutions was investigated to develop a novel method for partitioning americium from high level liquid waste generated through spent nuclear fuel reprocessing. Am(VI) was prepared using ammonium peroxodisulfate and silver nitrate. The distribution coefficients of Am(VI) were determined for extraction systems of various concentrations of nitric acid and TBP. Sufficiently stable Am(VI) could be extracted and the extraction reaction of Am(VI) was found to be the same as for other hexavalent actinides. The apparent equilibrium constant varied with the concentration of peroxodisulfate used for the valence control, which was ascribed to the competitive reaction of the extraction of Am(VI) and the complex formation of Am(VI) with sulfate ion produced by the decomposition of peroxodisulfate. A distribution coefficient of Am(VI) above 1 was obtained with undiluted TBP and the separation factor between Am(VI) and Nd(III) was 87±9. TBP extraction of Am(VI), after implementing valence control, was proved to be an effective method for the partitioning of americium from fission products such as rare earth elements.     

Half-Life and Gamma-Ray Energies of Lanthanum-144

A procedure using a complexing agent (NTA) in paper electromigration has been devised to achieve rapid separation of fission product lanthanum. This technique permits direct observation of the decay of the 42 sec ¹⁴⁴La without interference from the radiation of other fission products. The γ-ray spectrum of ¹⁴⁴La has been measured with a high-resolution Ge(Li) detector, and the following r-transitions were observed: 397, 434, 541, 586, 704, 734, 845, 951 and l,292keV. Their relative intensities were also determined. From the decay plots of the two strong photopeaks at 397 and 541 keV, the half-life of the ¹⁴⁴La was determined as 42.4±0.6sec which is more accurate than that of 41±3sec previously reported.

It is concluded that the separation procedure used in the present study can be adapted to the isolation of other short-lived fission products as well whenever their metal ions from the complexes by different values of the equilibrium constant.     

TBP萃取色层法分离超钚元素的研究

在用堆照钚、镅靶生产超钚元素的化学流程中,首先要提取钚,接着进行超钚元素与镧系元素的分离。TBP萃取法可以实现这二个过程,简化提取超钚元素的化学流程。TBP萃取色层法可以分离钚与镅,也可用此法进行锕系元素与镧系元素的分离。我们在前文的基础上,研究了用含盐析剂的硝酸溶液为洗提液时TBP萃取色层法分离钚和镅、     

钚及其裂变产物钯 、银 、镉 、锡 、锑 、锆的系统分离方法

描述了钚及其6种裂变产物钯、银、镉、锡、锑、锆的系统分离方法：在强碱性阴离子交换树脂柱上将盐酸介质的辐照靶溶解液中的这些元素分为5组,然后再针对各组目标元素进行分离和纯化,可简便快速地从同一份靶溶解液中分离以上7种元素。采用辐照铀靶对分离方法进行了验证,结果表明,分离流程对6种裂变产物的化学回收率均大于70%,对γ谱仪测量干扰的主要核素去污因子均大于1.0×10³,可满足²³⁹Pu裂变谷区核素裂变产额测量对化学分离的要求。