ICONE23-1044 Development of Hydrogen Treatment System in Severe Accident : (1) Study of the Hydrogen Treatment with Metal Oxides

Abstract

A large amount of hydrogen is generated in the event of a severe accident in a light water reactor. It is difficult to reduce the hydrogen concentration in the low oxygen concentration environment in a Boiling Water Reactor (BWR) condition. In order to deplete hydrogen under such conditions, we have been studying the application of metal oxides as a source of oxygen atoms. The reaction of hydrogen and a metal oxide produces steam, and the metal oxide changes to metal. We considered that this newly formed solid metal inhibits a rapid reaction between the hydrogen and metal oxide by increasing the hydrogen diffusion distance to the metal oxide. We conducted some experiments to select effective metal oxides. The weight loss of the metal oxide in the experiment was used as a measure of the efficacy of hydrogen treatment. From the results, CuO and MnO2 were selected as promising metal oxides. Furthermore, we observed a change in their crystalline structure with in-situ X-ray diffraction analysis (XRD) at a hydrogen concentration of 3% and a temperature of 523 K. CuO peaks were observed in the XRD profile in the initial stage of the reaction, and then Cu peaks appeared after 10 minutes, from which it was verified that the CuO reacted with the hydrogen. We confirmed that the Cu formed by the reaction of CuO with hydrogen acted as an inhibitor to a rapid reaction. We also conducted experiments to clarify the effects of the hydrogen and water vapor concentrations and the temperature on the reaction rate of hydrogen and CuO. It was confirmed that the reaction rate increased with increasing hydrogen concentration and temperature. On the other hand, the reaction rate of hydrogen decreased with increasing vapor concentration.