Radioactive Raman in situ

A new Raman system allows for materials undergoing irradiation to be studied in situ, exemplified by the analysis of simulated uranium dioxide spent fuel being irradiated by helium ions. Raman spectroscopy has begun to be used in harsh environments exposed to high temperatures and high pressures, but this is the first application in the nuclear industry which inspects materials in situ, rather than removing them for later analysis.

Aurélien Canizarès from the University of Orleans, France, and colleagues, wanted to examine the changes that take place at the surface of uranium dioxide spent fuel when reactive species such as hydrogen peroxide are formed in the storage water by α-irradiation emitted from the fuel. If the fuel is removed for analysis, it becomes difficult to differentiate between changes that occur before and after irradiation as well as during sample drying. Their solution, as described in the Journal of Raman Spectroscopy, was to couple a Raman device with the beam line of a cyclotron accelerator which allows the solid-liquid interface to be studied.

In their first experiments, they monitored the dissolution of uranium dioxide by hydrogen peroxide solution and in the second, they simulated radiation by studying the surface modifications on uranium dioxide in water upon irradiation with 5-MeV He²⁺ ions. In the former case, a layer of studtite [UO₂(O₂)-4H₂O] was formed on the surface, whereas in the latter, a layer of studtite and schoepite [(UO₃-2H₂O] was formed.