Thermodynamic Assessment of UO&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Pellet Oxidation in Mixture Atmospheres under Spent Fuel Pool Accident

Dong-Joo Kim,Jong Hun Kim,Sun Ki Kim,Yang-Hyun Koo,Jae Ho Yang,Keon Sik Kim

doi:10.4236/wjnst.2015.52009

Thermodynamic Assessment of UO&lt;sub&gt;2&lt;/sub&gt; Pellet Oxidation in Mixture Atmospheres under Spent Fuel Pool Accident

Dong-Joo Kim, Jong Hun Kim + Show 4 more

Open Access

https://doi.org/10.4236/wjnst.2015.52009

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Abstract

For an analysis of the oxidation behavior of UO2 nuclear fuel pellet under a loss of water coolant accident in a spent nuclear fuel pool of an LWR, thermodynamic assessments of UO2 oxidation were carried out under various atmospheric conditions. In a steam atmosphere, it was assessed that UO2 would not be fully oxidized into U3O8 due to the relatively lower oxygen partial pressure, while UO2 will be fully oxidized into U3O8 in an air atmosphere. In an air and steam mixture atmosphere, the UO2 oxidation was dominantly affected by the air volumetric fraction, because of the relatively higher oxygen partial pressure of air. In addition, the effect of H2 volumetric fraction on the oxygen partial pressure under a mixture atmosphere was calculated, and it was revealed that UO2 pellet oxidation could be reduced above the critical value of H2 volumetric fraction.

Highlights

Since the Fukushima Daiichi nuclear disaster on March 2011 [1], an accident in the spent nuclear fuel pool of an LWR has been extensively regarded an important concern [2] [3]
If a loss of water coolant accident in a spent nuclear fuel pool occurs, it can bring about a massive failure owing to a drastic increase in the temperature of the spent nuclear fuel
It can be thought that the equilibrium oxygen-to-uranium ratio of uranium oxide pellets in an air and steam mixture atmosphere is similar with that in an air atmosphere

Summary

Introduction

Since the Fukushima Daiichi nuclear disaster on March 2011 [1], an accident in the spent nuclear fuel pool of an LWR has been extensively regarded an important concern [2] [3]. If a loss of water coolant accident in a spent nuclear fuel pool occurs, it can bring about a massive failure owing to a drastic increase in the temperature of the spent nuclear fuel. The temperature of the spent nuclear fuel can increase by the loss of water coolant, and a steam atmosphere will be gradually generated. The hydrogen atmosphere can be generated by the reaction of the spent nuclear fuel clad-ding (Zr-based alloy) with air, steam or water (Zr oxidation). For analysis of the oxidation behavior of UO2 nuclear fuel pellet under a loss of water coolant accident in a spent nuclear fuel pool of an LWR, the thermodynamic assessments of UO2 oxidation were carried out under various atmospheric conditions

Thermodynamic Calculations

Results and Discussion

Summary