The generation of hydrogen gas from metallic waste in corrosive disposalenvironment is an important issue for the safety analysis of low-levelradioactive waste disposal facilities in Japan. In particular iron andaluminum are the possibly important elements regarding the gas generation.However, the corrosion behavior of these metals has not been sufficientlyinvestigated under the highly alkaline non-oxidizing disposal conditionsyet.
We studied the corrosion behavior of iron and aluminum under simulateddisposal environments. The quantity of hydrogen gas generated from iron wasmeasured in a closed cell under highly alkaline non-oxidizing conditions.The observed corrosion rate of iron in the initial period of immersion was 4nm/year at 15 °C, 20 nm/year at 30 °C, and 200 nm/year at 45 °C. Theactivation energy was found to be 100 kJ/mol from Arrhenius plotting of theabove corrosion rates.
The corrosion behavior of aluminum was studied under an environmentsimulating conditions in which aluminum was solidified with mortar. In theinitial period aluminum corroded rapidly with a corrosion rate of 20mm/year. However, the corrosion rate decreased with time, and after 1,000hours the rate reached 0.001 to 0.01 mm/year.
Thus we obtained data on hydrogen gas generation from iron and aluminumunder the disposal environment relevant to the safety analysis of low-levelradioactive disposal facilities in Japan.