Abstract
The rates of photolysis by sunlight of radioactive methly iodide released from a nuclear facility to the atmosphere were estimated theoretically. The photolysis rates of methyl iodide were also measured experimentally using stable methyl iodide gas which was irradiated by sunlight in the reaction vessel. The experimental values were compared with the calculated ones.
On a clear day in the low level of air pollution, the hourly maximum photolysis rate estimated is about 3.6%hr-1 at noon in the early of July and 1.5%hr-1 in winter. In annual variation of the daily photolysis rate on a clear day, the maximum (about 24% day-1) appears in July and the minimum (about 7% day-1) in December. The half life of methyl iodide by photolysis is estimated to be about 3 days in summer and 9 days in winter.
The calculated values are in agreement with the experimental ones within a factor of 2.
