Process for decontaminating gas containing radioactive iodine
AssigneeHitachi, Ltd.
InventorsMikio Hirano, Masaki Takeshima, Toru Saito, Atou Shimozato
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Abstract
A vent gas containing radioactive iodine and methyliodide is effectively decontaminated by chemically adsorbing the iodine contained in the vent gas onto an activated carbon layer at first, then physically adsorbing the methyl iodide contained in the vent gas onto another activated carbon layer separately disposed from the former activated carbon layer, and retaining the radioactive iodine and radioactive methyl iodide on the respective activated carbon layers for a definite period of radioactive decay.
Claims15
A process for decontaminating a vent gas containing radioactive iodine and radioactive methyl iodide, which comprises (1) chemically adsorbing iodine onto an activated carbon layer, (2) retaining the adsorbed iodine in a tightly sealed state for a predetermined period of time after the adsorption of iodine reaches a saturated state thereby decaying the radioactivity of the adsorbed iodine, (3) desorbing the adsorbed iodine by heating when decay of the radioactivity is completed thereby regenerating the activated carbon, (4) heating the vent gas passing out of said activated carbon layer during iodine adsorption, and (5) passing the heated vent gas through another activated carbon packed layer thereby decaying the radioactivity of the methyl iodide.
A process for removing radioactive iodine and radioactive methyl iodide from a vent gas having a relative humidity higher than 40% and containing radioactive iodine and radioactive methyl iodide, said process comprising (1) passing the vent gas through a first activated carbon adsorption bed to adsorb radioactive iodine thereon and produce a partially purified vent gas substantially free of radioactive iodine, (2) heating said partially purified vent gas to a temperature high enough so that the relative humidity of said partially purified vent gas is less than 40% and (3) passing the heated partially purified vent gas through another activated carbon adsorption bed to adsorb radioactive methyl iodide therein by physical adsorption and produce a purified vent gas.
A process for decontaminating a vent gas having a relative humidity of at least 40% and containing radioactive iodine and radioactive methyl iodide, said process comprising passing said vent gas into a series of separate adsorption beds to remove radioactive iodine from said vent gas and produce a partially purified vent gas substantially free of radioactive iodine, said series of separate adsorption beds including at least 3 separate activated carbon adsorption beds operated in series, each adsorption bed in said series repeatedly (1) adsorbing radioactive iodine for a predetermined period of time, (2) retaining adsorbed radioactive iodine therein until the radioactivity of the iodine has decayed, and (3) desorbing the adsorbed iodine, one of said separate activated carbon adsorption beds being desorbed and a second of said activated carbon adsorption beds retaining iodine therein for decay of the radioactivity thereof while a third of said adsorption beds adsorbs iodine therein, said process further comprising heating said partially purified vent gas to a temperature high enough so that the relative humidity of said partially purified vent gas is less than 40% and passing the heated partially purified vent gas through another activated carbon adsorption bed to physically adsorb radioactive methyl iodide therein and produce a purified vent gas, said another activated carbon adsorption bed having a size sufficient so that radioactive methyl iodide is retained therein until the radioactivity of said radioactive iodide is substantially completely decayed.
Dependencies are inferred from the claim text.