Comparison of the powderization effect of non-equilibrium plasma oxidation and thermochemical oxidation powders of uranium dioxide solids for actinide analysis

In order to facilitate the dissolution of these insoluble nuclear debris from the Fukushima accident, it is necessary to investigate methods of pulverizing them to increase their surface area. Although solid uranium dioxide is known to become powder through volume changes caused by oxidation, thermal oxidation can lead to the volatilization of quasi-volatile radioactive materials, so it is desirable to cause reaction under the milder conditions. We therefore developed non-equilibrium plasma oxidation device to verify the powderization of uranium dioxide solids and to compare the results with thermochemical oxidation. For the results of the plasma oxidation experiment, Uranium dioxide solid (42mg) can be partly converted to powder by plasma oxidation (6.5h, O2:0.4 L/min) with a low temperature (less than 200 ℃). And Partial oxidation of the powder, uranium dioxide to triuranium oxtoxide was confirmed by XRD. Small uneven bumps of 1µm or less appears on the surface of powders produced by oxidation using non-equilibrium plasma, thus increasing the surface area required for dissolution or chemical conversion to soluble compounds can be expected.