Technetium Metal and Pyrometallurgically Formed Sediments Study and Speciation by Tc-NMR and EXAFS/XANES
Description
EXAFS and NMR are promising methods to enable us with speciation of radioactive nuclides. It is important to use them for Tc speciation in pyrometallurgy which is now considered the most probable alternative approach to reprocessing of spent nuclear fuel. During pyrometallurgical spent fuel reprocessing, technetium can remain in the fused salt or enter (depending on the applied temperatures, reagents and potentials) either the sedimented phase contaminating Pu enriched phase, or electrodeposited U phase. Neither in sediment nor in deposit Tc phase could be detected by means of X-ray diffraction, Tc phase being finely dispersed and X-ray amorphous. Our preliminary results show that under such conditions Tc can also form several oxydes, oxychlorides and chlorides of different but rather high volatility, turning on an important polluting risk allied to gas-off . As the data on EXAF and NMR spectra of technetium are now very fragmentary and do not present the whole of the species possible in the pyrometallurgy conditions, it is of high importance to carry synthetic work to supply a large set of technetium compounds in the closed containers which will meet the security and quality demands, radioactivity level, special requirements on sample size, thickness, sample homogeneity.
|