Modelling of the Release of Radiolysis Hydrogen Bubbles from Bituminized Waste Products (BWPs) Under External Thermal Stress - 23219

Sludge (hydrated salts and radionuclides) from the treatment of radioactive liquid effluents is encapsulated in bitumen to ensure its containment. The bitumen matrix also traps dihydrogen bubbles formed by radiolysis. An apparent swelling due to gas accumulation, is observed. Two main parameters govern bubble ascendent velocity: bubble size and fluid viscosity. Bitumen viscosity decreases strongly with increasing temperature. Under external thermal stress, when the material temperature reaches 100 deg. C, bubbles rise from the bottom to the top within a few hours or even a few minutes instead of years or tens of years in normal conditions. All are gone before exothermic reactions occur. (authors)