Fission product technetium

Subsequently, solvent extraction was applied to recover the fission product technetium from the residue remaining after the fluorination of irradiated uranium fuel elements . The residue was leached with concentrated aluminum nitrate solution, which was extracted by 0.3 M trilaurylamine in a hydrocarbon diluent. After separation of uranium, neptunium, and aluminum nitrate, technetium was back extracted into a 4 N sodium hydroxide solution. 

For example, the fission products technetium and promethium are unique, in that they do not have any stable isotopes and do not occur in nature in measureable amounts. While promethium has a number of chemical analogues in the other rare-earth elements, this is not the case for technetium, and it is thus difficult to predict its behaviour in the geosphere. 

The RWMC assigned a high priority to the critical review of relevant chemical thermodynamic data of inorganic species and compounds of the actinides uranium, neptunium, plutonium and americium, as well as the fission product technetium. The first four books in this series on the chemical thermodynamics of uranium, americium, neptunium and plutonium, and technetium originated from this initiative. 

Modifications to the traditional PUREX process can also lead to the separation of two of the long-lived fission products, technetium and iodine. During dissolution, 10-20% of the... 

To estimate the environmental impact caused by nuclear fuel cycle of the SVBR-75/100, the value of specific radiotoxicity of the produced transuranic elements (neptunium, plutonium, americium and curium) and long-lived fission products (technetium-99, iodine-129 and caesium-135) was taken as a criterion, as a function of the electric energy produced. When this value decreases with energy production, the environmental impact of the nuclear fuel cycle can be considered friendly . The radiotoxicity characteristic adopted was the volume of water necessary to dilute some quantity of radionuclides to the concentrations for which the specific radioactivity of the solution meets the sanitary requirements for drinking water. 

Gr. technetos, artificial) Element 43 was predicted on the basis of the periodic table, and was erroneously reported as having been discovered in 1925, at which time it was named masurium. The element was actually discovered by Perrier and Segre in Italy in 1937. It was found in a sample of molybdenum, which was bombarded by deuterons in the Berkeley cyclotron, and which E. Eawrence sent to these investigators. Technetium was the first element to be produced artificially. Since its discovery, searches for the element in terrestrial material have been made. Finally in 1962, technetium-99 was isolated and identified in African pitchblende (a uranium rich ore) in extremely minute quantities as a spontaneous fission product of uranium-238 by B.T. Kenna and P.K. Kuroda. If it does exist, the concentration must be very small. Technetium has been found in the spectrum of S-, M-, and N-type stars, and its presence in stellar matter is leading to new theories of the production of heavy elements in the stars. 

Technetium, a fission product, also, can be separated by distillation of the oxide in its purification (91). 

TEA chloride See tetraethylammonium chloride., te,e a klorjd ) technetium chem A transition element, symbol Tc, atomic number 43 derived from uranium and plutonium fission products chemically similar to rhenium and manganese isotope Tc has a half-life of 200,000 years used to absorb slow neutrons in reactor technology. tek ne-she-om ... 

Separation of Technetium from Uranium Fission Products.114... 

Among the long-lived isotopes of technetium, only Tc can be obtained in weigh-able amounts. It may be produced by either neutron irradiation of highly purified molybdenum or neutron-induced fission of uraniimi-235. The nuclides Tc and Tc are exclusively produced in traces by nuclear reations. Because of the high fission yield of more than 6%, appreciable quantities of technetimn-99 are isolated from uranium fission product mixtures. Nuclear reactors with a power of 100 MW produce about 2.5 g of Tc per day . 

During recycling of the fuel technetium follows the majority of the other fission products into the waste solutions. After storage for several years, the level of the radioactivity in the waste solutions has fallen sufficiently to allow the extraction... 

Campbell has studied the separation of technetium by extraction with tributyl phosphate from a mixture of fission products cooled for 200 days. Nearly complete separation of pertechnetate is achieved by extraction from 2 N sulfuric acid using a 45 % solution of tributyl phosphate in kerosene. Ruthenium interferes with the separation and is difficult to remove without loss of technetium other radioisotopes can be removed by a cation-exchange process. However, this separation procedure has not been widely applied because of the adverse influence of nitrate. 

Goishi and Libby have investigated the extraction of pertechnetate from alkali solutions with pyridine. Later work showed that a better extraction is obtained using a mixture of sodium hydroxide and sodium carbonate as the aqueous phase. Since the uranyl carbonate complex is not extracted into pyridine, this system may be used for the separation of technetium from uranium. Distribution coefficients of fission products in pyridine are given in Table 4. Substituted pyridine such as 2,4-dimethylpyridine or 4-(5-nonyl)pyridine ) are useful for separating technetium from solutions containing appreciable amounts of aluminum nitrate. 

The solvent extraction of pertechnetate with cyclohexanone has proved to be an efficient and selective method which can be applied to the separation of Tc from long-lived fission products in the bum-up analysis . The recovery of technetium from the fission products is about 93 %. 

Chromatographic methods for the separation of technetium from fission products are based on the strong sorption of pertechnetate from weakly acidic, neutral, and... 

A radiochemical procedure is proposed for the determination of technetium activities from mixed fission products of uranium and thorium. The chief decontamination step is the extraction of TcO into a tetrapropylammonium hydroxide-bromoform mixture from 4.0 M NaOH solutions. Decontamination factors of 10 with chemical yields of 50-70% have been obtained. 

Tucker et al. have separated " Tc from the fission product Mo using chromatographic aluminum oxide washed by dilute nitric acid at pH 1.5. Mo dissolved in the same dilute HNO3 of pH 1.5 is passed through the column which is then eluted with 0.1 M HNO3. Tc is only slightly adsorbed and can easily be eluted while molybdenum is retained on the column. The purity of technetium is 99.99%. 

A method has been developed for the determination of technetium-99 in mixed fission products by neutron activation analysis Tc is separated from most fission products by a cyclohexanone extraction from carbonate solution, the stripping into water by addition of CCI4 to the cylohexanone phase, and the adsorption on an anion exchange column. Induced Tc radioactivity is determined using X-ray spectrometry to measure the 540 and 591 keV lines. The sensitivity of the analysis under these conditions is approximately 5 ng. The method has been successfully applied to reactor fuel solutions. 

Suitable conditions for the quantitative polarographic determination of technetium as pertechnetate are given by Miller et al. who propose a 0.1 M KCl solution of pH 10 or a phosphate buffer solution of pH 7. Since in pH 7 buffer the current is directly proportional to the concentration of technetium over the range of 0.1 to 1.1 ppm, this medium has been used for the determination of low concentrations of technetium in solutions of fission products by the standard addition technique. The half-wave potential of the used wave is —0.68 V vs. SCE. The reaction appears to be irreversible (Fig. 13). It has been found that neither rhenium, ruthenium nor other fission products interfere. However, tetraphenyl-arsonium chloride is reduced at a more positive potential than is pertechnetate therefore, (QH5) AsCl, if present, must be separated. 

For the rapid determination of Tc in a mixture of uranium fission products. Love and Greendale have used the method of amalgam polarography. It consists in a selective reduction of technetium at a dropping mercury electrode at a potential of —1.55 V vs. SCE in a medium of 1 M sodium citrate and 0.1 M NaOH. Under these conditions, technetium is reduced to an oxidation state which is soluble in mercury. The amalgam is removed from the solution of fission fragments and the amount of Tc determined in nitric acid solution of the amalgam by a y count. For Tc the measurement accuracy is within 1 %, and the decontamination factor from other fission products 10 . 

The major characteristic of technetium is that it is the only element within the 29 transition metal-to-nonmetal elements that is artificially produced as a uranium-fission product in nuclear power plants. It is also the tightest (in atomic weight) of all elements with no stable isotopes. Since all of technetiums isotopes emit harmful radiation, they are stored for some time before being processed by solvent extraction and ion-exchange techniques. The two long-lived radioactive isotopes, Tc-98 and Tc-99, are relatively safe to handle in a well-equipped laboratory. 

Heat capacity data for ions in aqueous solution over the temperature range 25-200°C. Such data for ionic species of uranium, plutonium, other actinides and various fission products such as cesium, strontium, iodine, technetium, and others are of foremost interest. 

Technetium has not been found to exist on earth. However, it has been detected in certain stars. Long-hved technetium-99 isotope of half-life 2.15x10 years is found in relatively significant quantities in fission products of uranium-235. Every Ig of uranium-235 yields about 0.027g of technetium-99 from its fission. 

C. Perrier and E. G. Segre discover technetium (element 43) among the fission products of molybdenum which has been bombarded with deuterons in the Berkeley cyclotron. 

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