The reactors at the Fukushima Daiichi nuclear power plant in Japan were overflowed by a tsunami following the Tohaku earthquake of 2011. Consequently, a power outage at the station disabled the cooling system, which lead to core melts in three reactors.

The reactors type BWR/3 were equipped with Isolation Condensors, a system that should cool the hot cores without any need for power. According to documentation, such a system could cool a reactor for days and such avoid core melt. This does not appear to have worked in the end. What was the problem?

(edited:)

Did human error contribute to the Condensors not working?

But seven minutes later, the operator decided to turn off Isolation Condenser system A by closing valve 3A for three reasons, TEPCO said:

1. steam evaporation had ceased, suggesting that valves 1A and 4A had shut because of the isolation signal; 2. there might not be sufficient water in the IC tank to run the system; 3. IC was not working, and there was no water injection line set up to supply coolant to the IC.

Source

The reactors at the Fukushima Daiichi nuclear power plant in Japan were overflowed by a tsunami following the Tohaku earthquake of 2011. Consequently, a power outage at the station disabled the cooling system, which lead to core melts in three reactors.

The reactors type BWR/3 were equipped with Isolation Condensors, a system that should cool the hot cores without any need for power. According to documentation, such a system could cool a reactor for days and such avoid core melt. This does not appear to have worked in the end. What was the problem?

(edited:)

Did human error contribute to the Condensors not working?

But seven minutes later, the operator decided to turn off Isolation Condenser system A by closing valve 3A for three reasons, TEPCO said:

1. steam evaporation had ceased, suggesting that valves 1A and 4A had shut because of the isolation signal; 2. there might not be sufficient water in the IC tank to run the system; 3. IC was not working, and there was no water injection line set up to supply coolant to the IC.

Source

(Edited again:)

Why did the workers not turn on the IC's manually (by handwheels)? Is there any reason to believe they would not have prevented the damage from happening?

The reactors at the Fukushima Daiichi nuclear power plant in Japan were overflowed by a tsunami following the Tohaku earthquake of 2011. Consequently, a power outage at the station disabled the cooling system, which lead to core melts in four reactors.

The reactors type BWR/3 were equipped with Isolation Condensors, a system that should cool the hot cores without any need for power. According to documentation, such a system could cool a reactor for days and such avoid core melt. This does not appear to have worked in the end. What was the problem?

(edited:)

Did human error contribute to the Condensors not working?

But seven minutes later, the operator decided to turn off Isolation Condenser system A by closing valve 3A for three reasons, TEPCO said:

1. steam evaporation had ceased, suggesting that valves 1A and 4A had shut because of the isolation signal; 2. there might not be sufficient water in the IC tank to run the system; 3. IC was not working, and there was no water injection line set up to supply coolant to the IC.

Source

The reactors at the Fukushima Daiichi nuclear power plant in Japan were overflowed by a tsunami following the Tohaku earthquake of 2011. Consequently, a power outage at the station disabled the cooling system, which lead to core melts in three reactors.

The reactors type BWR/3 were equipped with Isolation Condensors, a system that should cool the hot cores without any need for power. According to documentation, such a system could cool a reactor for days and such avoid core melt. This does not appear to have worked in the end. What was the problem?

(edited:)

Did human error contribute to the Condensors not working?

But seven minutes later, the operator decided to turn off Isolation Condenser system A by closing valve 3A for three reasons, TEPCO said:

1. steam evaporation had ceased, suggesting that valves 1A and 4A had shut because of the isolation signal; 2. there might not be sufficient water in the IC tank to run the system; 3. IC was not working, and there was no water injection line set up to supply coolant to the IC.

Source