Development of Evaluation System for Iodine Decontamination Factor in Filtered Containment Venting System

In this paper, the iodine measurement methods to evaluate the performance of FCVS at ARIEL is introduced. Experimental investigation for iodine retention performance were conducted. Decontamination factor for the FCVS is determined by two measurement methods which are ISEs and UV-vis. Modern filtered containment venting system (FCVS) can maintain the containment pressure by releasing the high temperature and pressurized gas from inside the containment to the environment during the severe accidents. During the releasing process, fission products are filtered simultaneously by FCVS to reduce the leakage of radioactive materials to the environment. So, in many countries the implementation of FCVS's is under discussion to mitigate fission product release not only in the short-term but also in the long-term view. Iodine is a major contributor to the potential source term to the environment, therefore, a good understanding of its behavior and validated calculation tools are required to perform meaningful risk analyses and make decisions in the field of accident management, mitigation measures and emergency procedures. The elemental and organic iodides are the main gaseous iodine species in the containment atmosphere. For the iodine retention, experimental programs have confirmed the existence of gaseous organic iodine in some cases in higher concentrations than for gaseous molecular iodine (I₂).