Advanced Radioactive Material Removal System by Silver Zeolite (9) Performance Evaluation of Silver Zeolite AgX by High Temperature and Atmospheric Pressure Test Equipment

Abstract Severe accidents at nuclear power plants produce a variety of materials such as inorganic and organic iodine, noble gases, and aerosols. Removal filters are taken against these radioactive materials by installing filter venting systems such as FCVS. The FCVS consists of a scrubber pool, metal fiber filter, silver zeolite, etc. Radioactive materials generated during a severe accident, water-soluble materials such as inorganic iodine are removed by the scrubber pool, granular materials and solids are removed by the metal fiber, and gaseous organic iodine is removed by the silver zeolite. We have developed silver zeolite AgX as a radioactive iodine adsorbent produced during severe accidents, and it has been used in nuclear power plants in Japan. In response to requests for use in a variety of environments, we developed a radioiodine adsorbent AgR, which is different from AgX. AgR is a silver zeolite like AgX, but the difference is that AgX has strong ability to bind hydrogen and oxygen, while AgR has a weak ability. To evaluate these silver zeolites, we fabricated a high-temperature test facility equipped with a scrubber pool, metal fiber filter, and silver zeolite, which is the same configuration as the actual facility, and evaluated the methyl iodide removal performance of the silver zeolite. The test was conducted under the assumption that methyl iodide-containing steam flows through the silver zeolite at room temperature (cold start), simulating a severe accident. As a result, it was confirmed that AgX and AgR shoed high methyl iodide adsorption performance even at 100% steam.