Effects of environmental factor on gas evolution behavior from Al in simulating mortar environments

Dry Low-Level Radioactive Wastes (LLW) which mean incombustible solid LLW generated from nuclear power stations are scheduled to be packed in steel drums followed by solidification with mortar. The solidified dry LLW is then to be disposed to shallow under-ground at Rokkasho LLW Disposal Center. Dry LLW includes some amphoteric metals among which aluminum is the most corrosive with gas evolution in high alkaline media such as mortar. The evolved gas may accelerate the leaching of solidified dry LLW with mortar. Despite the planned removal of aluminum from dry LLW, small inclusion of aluminum is unavoidable. The present study focuses on the effect of environmental factors such as pH and temperature on gas evolution behavior caused by aluminum corrosion. Large effects of pH and temperature on corrosion rate of aluminum and gas evolution were recognized. Principal corrosion product of aluminum was calcium aluminate compound when it was immersed in simulated mortar environments. It is demonstrated that 1.5 mol hydrogen gas evolves with the corrosion of 1 mol aluminum in environments of 12 < pH < 13 at temperatures below 60degC. (author)