Technetium from nuclear fuel waste

The technetium isotope of interest for nuclear fuel waste disposal is Tc. It is a pure 3-emitter (E = 0.293 MeV) with a half-life of 2.13x10 years. Its high fission yield of 6% accounts for the relatively high concentration 0.02% by weight) (1) in fuel discharged from a CANDU (CANada Deuterium Uranium) reactor (burnup 650 GJ/kg U). 

Several X-ray fluorescence speclromelric delerminations of lechnelium were reported. Hie lines X.,2=0.67927 A, X,i=0.67493 A, X, i=0.6()141 A, and X,(2= 0.59018 A can be used for detection and determination of the element 30,31]. From neutron irradiated molybdenum milligram quantities of Tc could be isolated and detected by the Ka and Kjn lines [46]. Because of its simplicity and selectivity, an X-ray fluorescence method was developed for the determination of technetium in solution. At concentrations of less than 1.0 mg Tc per ml no interelcment effects were observed. Therefore, it is possible to ascertain technetium in its compounds without their prior decomposition, provided the compounds are soluble in water or dioxane. The detection limit is about 4- lO g Tc [47. For the determination of Tc in nuclear fuel processing wastes by X-ray fluorescence, a rapid, simple, and accurate method was reported [48]. 

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. 

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