Development of Hydrogen Treatment System in Severe Accident: Part 3 — Study of Reactant Diameter Effect on Hydrogen Treatment

Abstract

The hydrogen treatment system has been developed in order to prevent the overpressure of the primary containment vessel (PCV) caused by a large amount of hydrogen generated by the metal-water reaction in severe accidents (SAs) of Light Water Reactor. In previous studies, we evaluated the hydrogen treatment rate using a couple of metal oxides, and confirmed that MnO2, CuO, and Co3O4 were effective for the hydrogen oxidation under the oxygen-free condition, then we selected them as reactants[1]. Although the reactants were granulated with a diameter of 2 mm for application to the system, the hydrogen treatment rate has not been scarcely evaluated for the granulated MnO2 which is expected to treat the hydrogen around 120 °C [2]. Thus, we made the diameter of the granulated MnO2 smaller, and found that the hydrogen treatment was occurred by the granulated MnO2 with a diameter below 1.0 mm. The granules with a diameter below 1.0 mm were also acceptable for the system from the point of view of decreasing the differential pressure (DP). Moreover, the experiments using a test section simulating a reactor of the system had been conducted under the hydrogen condition simulating typical condition of a SA, by loading the granulated CuO with a diameter of 2mm onto the granulated MnO2 with a diameter of 1mm. As a result, the hydrogen treatment was markedly accelerated by supplying enough reaction heat from the granulated MnO2 to the granulated CuO.

Modeling of low-temperature reduction of metal oxide in hydrogen treatment system for severe accidents in nuclear power plants

“…A hydrogen treatment system that re-oxidizes hydrogen into water vapor is one of the methods under development to prevent hydrogen explosion without venting radioactive materials. One of the most prominent hydrogen oxidation methods uses a packed, fixed bed reactor with metal oxide pellets (Yamada, et al, 2017;. The performance of this method does not depend on the oxygen concentration of the atmosphere because the metal oxide pellets act as the oxygen donor.…”