Technetium Purex process

Long-lived ty = 2.1 x 10 years) Tc, present as TCO4 in Purex process HNO3 feed solutions, is partially coextracted with uranium and plutonium in the first cycle. Unless separated in the Purex process, Tc contaminates the uranium product subsequent processing of the U02(N03)2 solution to UO2 can release some of the technetium to the environment. The presence of technetium in the purification steps as well as in the uranium product causes several other complications. Thus it is desirable to route all Tc into the high-level waste. Efforts in this direction have been described in some recent flow sheets [37]. 

Kanellakopulos, B., Konig, C.P. 1983. On the extraction behavior of technetium with respect to the Purex process. Radiochim. Acta 33 169-175. 

Uchiyama, G., Asakura, T., Hotoku, S., Fujine, S. 1998. The separation of neptunium and technetium in an advanced PUREX process. Solvent Extr. Ion Exch, 16 (5) 1191-1213. 

The flowsheet of the UREX process, developed in the United States, includes the following extraction cycles (1) separation of uranium and technetium, (2) separation of plutonium, (3) separation of cesium and strontium, (4) separation of MAs and Rare Earth Elements (REE), and (5) group separation of MA from REE metals.9,10 Flowsheet development in Europe11 includes a modified PUREX process and, after that, the DIAMEX process for separation of MAs and lanthanides, the SANEX process for separation of MAs from lanthanides, and a special cycle for Am/Cm separation. Cesium and strontium will be in the raffinate of the DIAMEX process, and this raffinate will be vitrified, or cesium can be preliminarily extracted.12... 

In summary, potential improvements could be made to the PUREX process in the following areas (1) separation of Np from U and Pu prior to the U/Pu split and (2) in the requirement to use a large excess of U(IV) reductant to reduce Pu(IV) to Pu(III). The majority of published work on the applications of photo catalysis in actinide redox chemistry has concentrated on solving the first of these difficulties through Np valence control. A smaller volume of literature exists on the applications of photocatalysis in valence state control of U and the radioactive d block metal, technetium. This section will review both of these aspects. 

UREX [URanium Extraction] A solvent extraction process for extracting uranium and technetium from used nuclear fuel, while rejecting all the transuranic elements. Based on the Purex process, which uses tributyl phosphate in a hydrocarbon mixture, but incorporating acetohydroxamic acid, which complexes the Pu and Np and thereby prevents them from being extracted. Developed by the Westinghouse Savannah River Company in 2003. Associated processes are NPEX, TRUEX, and Cyanex 301. 

The classical Purex process was designed to produce nearly pure uranium and plutonium. The Chemical Engineering Division of Argonne National Laboratory has demonstrated UREX+, an advanced aqueous process with five extraction trains that split commercial reactor spent fuel into five streams 1) a nearly pure uranium stream (95.5% of the heavy metal in the spent fuel) 2) technetium sent to transmutation (0.08 /o) 3) Pu/Np converted to MOX fuel for LWR fuel and Am/Cm for transmutation or fast-flux reactor fuel (0.962 /o) 4) Cs/Sb decay heat producers sent to interim decay storage (0.017 /o) and 5) a mixed fission product stream (3.44 /o) composed of gases and solids incorporated into a waste form for geological repository disposal.f The percentages shown are computed from Table 1. 

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... 

Concerning the wet separation methods, the possibility to separate neptunium, the soluble part of technetium and perhaps zirconium directly during the PUREX process is being studied. 

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. 

---