Technetium from ruthenium

Partial separation of technetium and rhenium is possible by distillation from perchloric acid since the first fraction is enriched by technetium. However, ruthenium is oxidized by perchloric acid to RuO and volatilized together with technetium. 

Some precipitation methods have been applied to the separation of technetium from molybdenum when the former occurs as a radio-active daughter-product of the latter. The separation of technetium is performed by co-precipitation with tetraphenylarsonium perrhenate from an alkaline molybdate solution . In this way, also ruthenium remains in solution. Molybdate may be precipitated away from pertechnetate using 8-hydroxyquinoline " or a-benzoinoxim Pb or Ag" ions can also be used . Kuzina and Spitsyn have developed a method for concentrating technetium from ammoniacal molybdate solutions by co-precipitat-ing pertechnetate with the slightly soluble crystalline MgNH PO. ... 

The optical emission spectrum of technetium is uniquely characteristic of the element " with a few strong lines relatively widely spaced as in the spectra of manganese, molybdenum and rhenium. Twenty-five lines are observed in the arc and spark spectra between 2200 and 9000 A. Many of these lines are free from ruthenium or rhenium interferences and are therefore useful analytically. Using the resonance lines of Tc-I at 4297.06, 4262.26, 4238.19, and 4031.63 A as little as 0.1 ng of technetium can be reliably determined. 

Behavior of Technetium and Ruthenium A pilot plant test was conducted to study the behavior of technetium and ruthenium in the uranium calcination process. The U0- product from these tests was used i subsequent fluorination studies. The UNH feed was spiked with xc (as ammonium pertechnetate) and nonradioac-tive ruthenium (as ruthenium nitrate), and then denitrated under normal run conditions. As expected, most of the technetium was found in the UO product as technetium oxide. Over half of the ruthenium (RuO )° was volatilized and found in the condensate from the off-gas. 

Stable binary metal carbonyls, negatively charged or uncharged, exist for all the elements of the 3d, 4d, and 5d transition series from CSroup 4 to Group 10, with the exception of palladium. As shown in Table 1, some of the elements (Ti, Zr, Hf, Nb, Ta, and Pt) have anionic carbonylmetalates only and no stable uncharged derivatives have so far been reported. Of the known metal carbonyls, only those of Group 6, Group 7 (with the exclusion of technetium), iron, ruthenium, cobalt and nickel have been used much in catalytic processes. 

From the above discussion it follows that tetravalent and hexavalent thorium, uranium, and plutonium can be separated from the trivalent rare-earth fission products by taking advantage of differences in complexing properties. More highly charged cation fission products, such as tetravalent cerium and the fifth-period transition elements zirconium, niobium, molybdenum, technetium, and ruthenium, complex more easily than the trivalent rare-earths and are more difficult to separate from uranium and plutonium by processes involving complex formation. 

The property of pcrtcchnctate to be reduced by hydrochloric acid can be used for separating Re04 from reduced TcOj by distillation in a mixture of H2SO4 and HCl at 180 °C [8]. Under these conditions most of rhenium passes into the distillate, but almost all the technetium remains in solution. Another distillation procedure involves reduction of 1 c04 by hydroxylamine. Perrhcnic acid is distilled with steam from sulphuric acid. Up to 10 mg of rhenium can be separated quantitatively from traces of technetium [105]. Partial separation of TcOj from ReO.i is achieved by distillation from perchloric acid, because the first fraction is enriched by technetium. However, ruthenium is oxidized by perchloric acid to RUO4 and volatilizes together with technetium [104]. Due to considerable differences in vapor pressures of H l c04 and HRe04, technetium may be almost quantitatively separated from rhenium by alternate evaporation with nitric and hydrochloric acid [106]. 

Other high-melting metals tend to be located near tungsten—zirconium, hafnium, molybdenum, technetium, rhenium, ruthenium, osmium, rhodium, iridium, and platinum—and have a melting point that ranges from 1,772°C to 3,180°C (3,222°F to 5,756°F). 

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. 

The extraction of TcO with methyl ethyl ketone, acetone, and pyridine results in a ruthenium decontamination factor of about 10 . Another effective separation method is based on the extraction of technetium as triphenylguanidinium pertechnetate from sulfuric acid by means of chlorex ()S-chloroethyl ether). Pertechnetate can be re-extracted with 3 N NH OH solution . 

FP-4 (zirconium, niobium, molybdenum, technetium, ruthenium, rhodium, palladium, silver, cadmium, indium, tin, antimony)—are only slightly soluble (<1 wt %) in the process alloy, thus will partition between both product streams. The process, as presented, offers no method of FP-4 removal and possibly an unwanted increase in these products would occur if the fuel were to be recycled. However, it would be possible to separate the FP-4 from the plutonium/thorium stream by recovering the plutonium/thorium by hydriding. The FP-4 do not form stable hydrides and would remain in solution. 

Redox-type waste contains considerable mercury, which must be removed. Advantage is taken of the presence of mercury to use it as a carrier for the ruthenium and technetium when this group is precipitated as the sulfides. This involves fairly corrosive chemical solutions, but they can be handled in equipment fabricated with special grades of stainless steel. The filtrate contains only the alkaline and rare earths which are then precipitated as carbonates, the same as the Purex-type procedure. The waste from this step is treated separately. 

The reason that nuclear wastes must be isolated from the environment for a very long time is that they contain relatively long-lived radioactive nuclides, such as technetium-99 with a half-life of over 2.1 x 10 years. One proposed solution is to bombard the waste with neutrons so as to convert the long lived nuclides into nuclides that decay more quickly. When technetium-99 absorbs a neutron, it forms technetium-100, which has a half-life of 16 seconds and forms stable ruthenium-100 by emitting a beta particle. Write the nuclear equations for these two changes. 

Dry distillation and gas phase separation of technetium oxides from oxides of rhenium, osmium, iridium, and ruthenium by temperature-programmed gas chromatography using O2 as reactive gas was reported [109]. Furthermore, the separation of technetium chloride (TeCU) from volatile chlorides of numerous elements by thermo-chromatography combined with complex formation was investigated. The separation tube had a temperature gradient from 600 to 25 °C and was coated with KCl, CsCI, NaCl, and BaClj [HOj. 

The above-cited reactions are used to separate Tc for measurement. Rhenium is a common nonisotopic carrier for precipitation or yield measurement. The shorter-lived Tc (60 days) has been used as isotopic tracer for yield measurement (Anders 1960). Technetium can be separated from rhenium by coprecipitating the +4 state with ferric hydroxide while rhenium remains in solution. Technetium is separated from the fission-produced radionuclides ° Ru and ° Ruby distillation with Re207 from sulfuric acid while ruthenium remains behind because it is volatile only in its... 

LS counters are suitable for measuring radionuclides that emit only very low-energy beta particles or electrons, notably tritium (Emax = 18.6 keV). When tritium is measured as tritiated water and its activity is reported relative to water weight or volume, no yield measurement is needed. Liquid samples, e.g., water from the environment, process streams, urine, or dissolved solids, can be counted directly or purified by distillation. Results for purified samples are more reliable to the extent that the radioelement can be identified, quenching is stabilized, and luminescent contaminants are removed. Reagents may have to be added to the distillation flask to hold back other potentially volatile radionuclides, such as radioactive iodine, carbon, ruthenium, or technetium. 

The steps and missteps in the process of discovering new elements led to caution in accepting a previously unidentified spectroscopic feature as evidence for a new element (Boyd 1959). Chemical characterization was required. For example, masurium was proposed for element 43, and illium and fiorentium were proposed for element 61 based on atomic spectroscopy of extracts from minerals. In retrospect, it is clear that there was evidence for unusual conditions for these elements. For example, above 7N the only mass numbers of stable isotopes of elements with odd atomic number are also odd, and there is only one stable isobar for each odd A. Molybdenum (Mo) has stable isotopes 92, 94—98, and 100. Ruthenium has 96, 98-102, and 104. Niobium has 93, and rhodium 103. Nothing is left for technetium, which would have the best chance for stability at mass numbers 97 and 99. Similarly, either neodymium or samarium has a 3-stable isotope fi om 142 to 150 nothing is left for promethium. 

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