Nuclear power remains an attractive base-load power source due to its affordability and low CO 2 intensity according to Japan’s S+3E strategy (Safety + Energy Security, Economic Efficiency, and Environment). That being said, the hazards due to severe accidents such as the Fukushima Daiichi NPS (Nuclear Power Station) should be mitigated. Therefore, several independent levels of defense in depth should be considered. At the Fukushima Daiichi NPS, zirconium in the fuel rod cladding pipes reacted with water vapor at elevated temperatures due to a loss of cooling water, resulting in the production of a large amount of hydrogen. This hydrogen leaked from the reactor vessel and accumulated in the top of reactor building, eventually leading to a disaster. A hydrogen treatment system that re-oxidize hydrogen and restore water vaper is one of the effective methods to prevent this explosion disaster. A prominent treatment method is hydrogen oxidation by a fixed bed reactor packed with metal oxide pellets. The advantages of this method are its relatively fast oxidation rate without external oxygen/air injection. This work aims to develop a method to predict the observed oxidation rate of hydrogen through a packed bed of copper oxide to design the hydrogen treatment system. As already reported in several papers, an induction period of tens of minutes is observed due to the reduction-oxidation reaction between copper oxide and hydrogen at temperatures below 250 °C. Modelling of this induction period is necessary for proper design and operation of the hydrogen treatment system and may provide insight into methods to reduce or eliminate the induction period. Although some of the papers discuss the cause of the induction period could be due to the hydrogen adsorption process, it is not well understood, and current models are unable to simulate the experimental result of induction period accurately. In this study, the oxidation of hydrogen by copper oxide is modeled by 5 interacting, elementary reactions consisting of 6 chemical species (i.e., H 2 , H, H 2 O, CuO, Cu 2 O, Cu 0 ). The reaction rate of each elementary reaction is based on measurements from microreactor testing using spherical pellets of copper oxide. Measurement of inlet/outlet gas composition and pre/post-analysis of solid composition were considered for numerical calculations to determine constants of the individual reaction rate. From these reaction constants, the temporal behavior of the outlet gas was predicted.&nbsp;


ICONE Competition - ICONE28-POWER2020-16450: Modeling of Low-Temperature Reduction of Metal Oxide in Hydrogen Treatment System for Severe Accidents in Nuclear Power Plants

Division / Sponsors: 
Power Division & Nuclear Engineering Division (NED)

Power Conference
Paper Proceedings: https://asmedigitalcollection.asme.org/POWER/POWER2020/volume/83747

International Conference on Nuclear Engineering
Paper Proceedings: https://asmedigitalcollection.asme.org/ICONE/ICONE2020/volume/83761

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