Evaluation of pH dependence emission behavior for gaseous inorganic/organic iodine under irradiation

Abstract

When severe accident occurs in nuclear power plant, radioactive iodine would be emitted from reactor pressurized vessel to primary containment vessel (PCV). The emitted iodine is basically trapped into the suppression pool water in ionized condition. However, it is assumed that the gaseous iodine might be re-volatilized from the water in suppression pool chamber by the irradiation effect. The iodine volatilizing behavior is said to be affected by irradiation and pH control of the pool water. In this study, volatilizing behavior of inorganic/organic iodine with pH control under gamma-ray irradiation is evaluated, based on simulated actual plant environments. It is confirmed that the pH control to alkaline environment is effective to the inhibition of re-volatilization of inorganic/organic iodine. It is also confirmed that the emission behavior of organic iodine gas is mainly due to the reaction between the epoxy paint of gaseous phase in PCV inner wall and volatilized inorganic iodine gas with irradiation effect. Under non-irradiation, emission of inorganic iodine was extremely low, and almost no emission was detected in the inorganic iodine. Moreover, it is assumed that the existence of inorganic iodine and hydrocarbon radical compound emitted from epoxy paint component leads to the emission of organic iodine.

Keywords

• inorganic iodine
• organic iodine
• irrradiation
• ph
• epoxy paint
• emission