Radiolysis and Ageing of C2-BTP in Cinnamaldehyde/Hexanol Mixtures
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0985-NN03-20
Radiolysis and Ageing of C2-BTP in Cinnamaldehyde/Hexanol Mixtures Anna Fermvik, Christian Ekberg, Teodora Retegan, and Gunnar Skarnemark Nuclear Chemistry, Chalmers University of Technology, Kemiv. 4, Gothenburg, SE-412 96, Sweden
ABSTRACT The separation of actinides from lanthanides is an important step in the alternative methods for nuclear waste treatment currently under development. Polycyclic molecules containing nitrogen are synthesised and used for solvent extraction. A potential problem in the separation process is the degradation of the molecule due to irradiation or ageing. An addition of nitrobenzene has proved to have an inhibitory effect on degradation when added to a system containing C2-BTP in hexanol before irradiation. In this study, 2,6-di(5,6-diethyl-1,2,4-triazin-3-yl)pyridine (C2-BTP) was dissolved in different mixtures of cinnamaldehyde and hexanol and the effects on extraction after ageing and irradiation were investigated. Similar to nitrobenzene, cinnamaldehyde contains an aromatic ring which generally has a relatively high resistance towards radiolysis. Both C2-BTP in cinnamaldehyde and C2-BTP in hexanol seem to degrade with time. The system with C2-BTP in pure hexanol is relatively stable up to 17 days but then starts slowly to degrade. The solution with pure cinnamaldehyde as diluent started to degrade after only ~20 hours. The opposite is true for degradation caused by radiolysis; hexanol systems are more sensitive to radiolysis than cinnamaldehyde systems. Most of the radiolytic degradation took place during the first days of irradiation, up to a dose of 4 kGy.
INTRODUCTION The 443 nuclear power reactors in operation in the world (2005) [1] generate waste that must be stored for very long periods of time to render it harmless, e.g. 100,000 years [2]. One reason for these long storage times is the presence of some actinides such as neptunium, americium and curium, with very long half lives and hence long radiotoxicity. By exposing actinides to a neutron flux, the elements can fission and form stable or more short lived isotopes. Lanthanides, another constituent in the spent fuel, have a much larger neutron cross section than actinides and it is therefore important to separate these two groups of elements. The separation of actinides from lanthanides poses a difficulty due to their similarity in physical and chemical properties and one technique that is considered for this separation is solvent extraction. It is currently used in the PUREX process for separating plutonium and uranium from the rest of the spent fuel [3]. A potential problem in the separation process can be the degradation of the extracting ligand due to ageing, exposure to ionizing radiation etcetera. The ligand is dissolved in an organic system and the choice of diluent in this system may have a considerable effect on the degradation since it for example can make the system more or less resistant towards radiolysis. One type of extractant used for this selective separation is polydentate nitrogen-containi
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