Technetium recovery

Goldberg [44], surprisingly high concentrations were detected for the former 16, 000 Bq/kg, for the latter 43,000-46,000 Bq/kg. All these data indicate that technetium should be carefully recovered in reprocessing plants. The systematic recovery of technetium together with elements of the platinum group from high level wastes have been discussed by Kubota [45],... 

In closing, recovery of technetium from waste solution should be touched upon. Studies of the base hydrolysis of technetium P-diketone complexes revealed that all of the complexes studied decompose in an alkaline solution even at room temperature, until technetium is finally oxidized to pertechnetate. These phenomena are very important for the management of technetium in waste solutions. Since most metal ions precipitate in alkaline solution, only technetium and some amphoteric metal ions can be present in the filtrate [29]. A further favorable property of pertechnetate is its high distribution coefficient to anion exchangers. Consequently, it is possible to concentrate and separate technetium with anion exchangers from a large volume of waste solution this is especially effective using an alkaline solution [54],... 

Thirdly, some obvious applications of coordination chemistry are omitted from this volume if they are better treated elsewhere. This is the case when a specific application is heavily associated with one particular element or group of elements, to the extent that the application is more appropriately discussed in the section on that element. Essentially all of the coordination chemistry of technetium, for example, relates to its use in radioimmunoimaging inclusion of this in Chapter 20 of this volume would have left the chapter on technetium in Volume 5 almost empty. For the same reason, the applications of actinide coordination complexes to purification, recovery,... 

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 %. 

Appreciable separation of pertechnetate from molybdate is achieved by pyridine as extracting agent However, the high boiling point of pyridine complicates the recovery of technetium by steam distillation of pyridine. Therefore, this method is rarely used. 

Recovery of technetium, present as pertechnetate in aqueous acidic solution, is of utmost importance because of its long half-life of 2.13 x 105 years and its relative mobility in the environment. The close relation between TCO4 and the isoelectronic perrhenate Re04 makes the latter a widely used model for artificially produced technetium, which only possesses radioactive isotopes. 

In addition, development studies have addressed the recovery of stable rhodium, xenon, technetium, and palladium because of their limited availability in nature. For palladium this would amount to about 40 kg per year from a 1000 MWe reactor. However, a... 

Modifications to this process can be made to effect recovery of neptunium, americium, curium, californium, strontium, cesium, technetium, and other nuclides. The efficient production of specific transuranic products requires consideration of the irradiation cycle in the reactor and separation of intermediate products for further irradiation. 

Morita et al. (1993) have applied ICP-MS to the determination of technetium-99 in environmental samples. The determination of eliminating the interfering element (Ru) before the ICP-MS measurements are made. Technetium-95m is used as the chemical recovery tracer. Compared with conventional methods, the method sensitivity is 10 to 100 times higher and the counting time is 300 to 10,(KX) times shorter. 

Matsunari I, Fujino S, Taki J, Senma J, Aoyama T, Wakasugi T, Hirai J-I, Saga T, Yamamoto S, To-nami N (1997) Quantitative rest technetium-99m tetrofosmin imaging in predicting functional recovery after revascidarization comparison with rest-redistribution thallium-201. J. Am Coll Cardiol 29 1226-1233... 

Finally, was elcclrodcposited from an oxalic acid medium onto a bronze disc and counted. The overall recovery was >90"/<) and the precision 0.2 pCi (7.4-10" Bq) at a technetium level of 0.6-1.0 pCi/1 seawater [11]. 

Each of these elements may be used for production of nuclear fuel or other purposes. The recovery efficiency for uranium is reported as 99.87% and for plutonium 99.36%-99.51% (NEA 2012). The extended PUREX includes separation of neptunium and technetium as well as recovery of americium and curium that are also separated from each other by additional extraction stages as given in detail in the flowsheet (NEA 2012). The advanced UREX-i-3 process generates six streams after separation uranium for re-enrichment Pu-U-Np for mixed oxide fuel c for managed disposal Am-Cm to be used as burnable poisons and for transmutation high-heat-generating products (Cs and Sr) and a composite vitrified waste with all other fission products. Some fuel types may require preliminary steps like grinding to enable their dissolution. 

In 1937 Perrier and Segre bombarded a molybdenum target with deuterons to produce technetium as the first man-made element [34]. This element has 31 known isotopes with mass numbers firom 86 to 117, and all are radioactive. The most readily available isotope is Tc = 2.1 X10 years), which can be isolated from spent nuclear fuel where it constitutes approximately 6% of the fission product yield of U. In the recovery process, the pertechnetate anion, [ TcO, ] , is extracted with pyridine firom aqueous solution and ultimately isolated as [NH j [TcO, ] with a purity of better than 99.9% [35]. The ammonium salt is readily available at a reasonable cost from Oak Ridge National Laboratory [36]. 

Batches of performance assessment samples (section 2.4) were analysed on different occasions. Results for unspiked previously characterised materials are presented in Figure 4 and all results summarised in Table 4. Recovery of technetium from spiked samples showed accuracy over the range 10 - 1000 Bq kg to be 94-104 % for soil, 100-108 % for silt, 97-99 % for sand and 101 - 109 % for sediment with precision (as % RSD) across all sample types between 4 and 24 %. Precision improved to <10 % where Tc activity concentrations were > 100 Bq kg. Detection limits estimated from the replicate analysis of blank soils, silts and sediments according to Currie (Ld = 2t-So) were typically 2Bq kg for a 2 g sample of soil, silt or sediment. 

---