The apparent lack of understanding, shown by Tokyo Electric Power Company (TEPCO), of the dangers of hydrogen explosions in a nuclear power plant has to be pointed out when considering the explosion which occurred at the Fukushima Dai-Ichi nuclear power plant. If TEPCO had understood the significant risks involved in the running of a nuclear power plant, such a major accident could have been avoided.
Even in the government report, written by the Investigation Committee on the Accident at the Fukushima Nuclear Power Stations of TEPCO, this lack of understanding is evident. In the minutes of the meeting, which was held to discuss the report, the secretary of the committee states, "An unexpected hydrogen explosion has occurred." Furthermore, the report gave the amount of hydrogen generated by the water-zirconium reaction as 900 kg. This was an amount taken from the TEPCO report on the incident and not independently verified. In contrast, after the Three-Mile-Island disaster, the NRC estimated the resultant amount of hydrogen produced in the reaction by themselves.
The key factor in any hydrogen explosion is temperature. In my last paper, where I discussed the Three-Mile-Island incident, I stated that when simulating a hydrogen explosion at a higher temperature this results in a significantly shorter reaction time. For example, at 1000°C the time is 100 hours, whereas at 1500°C it is two hours. Therefore, in the case of the Fukushima accident, all attention should have been first focused on the cooling of the reactor to avoid the generation of hydrogen which would, and did, ultimately lead to an explosion.
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