Atomic Energy Society of Japan

The No.1 reactor of Fuku-Ichi experienced a hydrogen gas explosion on 3/12/2011, resulting in a severe nuclear catastrophe. It was due to the same cause as No. 3 reactor, in which hydrogen gas was produced from zirconium cover of the fuel rod by oxidation reaction. However, the time of gas production remains uncertain because of the absence of temperature calculation on the reactor core. The authors set up a simple model approximating the fuel core by 10 consecutive spherical shells. A numerical analysis of radiative heat transfer under the condition of decay heat 1% indicated that the core temperature reached in 41 minutes 3000 Celsius