RADIOLYTIC CORROSION OF GRAIN BOUNDARIES ONTO THE UO2 TRISO PARTICLE SURFACE

International audienceThis work is dealing with the understandingof the corrosion mechanisms at solid/solutioninterface and taking into account for the4He2+ions irradiation effects on these mechanisms.These corrosion and4He2+ions radiolysis phenomena append at solid/solution interface andwill be studied at a μmetric scale by the Raman spectroscopy. Moreover, a4He2+ionsirradiation appends onto a low volume and let usto control the irradiated area (solution, solidor interface). For the solid, the chemical species induced by4He2+ions radiolysis of water aresuch reactive and are involved in classical corrosion mechanisms of UO2. Moreover, we wantto study the impact of the4He2+ions radiolysis of water layers physisorbed into the surfaceonto corrosion mechanisms. That is the reason why we want to use a local irradiation, allowedby the4He2+ions ion beam provided by the ARRONAX cyclotron (E = 64.7 MeV). In thiswork an experimental apparatus will be performed in order to characterize solid/solutioninterface at μmetric scale by Raman spectroscopy under4He2+ions irradiation provided by thecyclotron ARRONAX facility. The leaching experiments under irradiation will be performedfor a short time in order to study the parametersduring the fast instantrelease step. The grainboundaries effect will be studied by the comparison between one TRISO particles set (solidswith grain boundaries) and oneTRISO particles set previously washed by one acid solution(solid without grain boundaries). The role of H2will be studied by the comparison betweenexperiments under Ar or Ar/H2atmosphere. The dose rate range will be between 0 and 100Gy/min by using the alpha ion beam which letus control the dose set down into the sample.For all these experiments, measurements will be performed by thein situRaman spectroscopyduring the irradiation in orderto follow the formation/consumption of the secondary phasesformed onto the solid. The SEM will be performed in order to characterize the grainboundaries and the secondary phases formed bythe leaching/irradiation experiments. TheμGC is used to measure the PH2into the irradiation cell tofollow the production/consumptionof this gaseous species formed by the water radiolysis and consumed by the leaching process