#Fukushima I Nuke Plant: Hydrogen Gas in a Pipe Leading to Reactor 2 CV

The concentration is less than in the case of Reactor 1 pipe (63%), as it was only 6.5%.

From Yomiuri Shinbun (10/12/2011):

東京電力は１２日、福島第一原子力発電所２号機の格納容器につながる配管から、高濃度の水素が検出されたと発表した。

TEPCO announced on October 12 that the high concentration of hydrogen gas was detected from the pipe that connects to the Containment Vessel of Reactor 2 at Fukushima I Nuclear Power Plant.

　１号機の配管で検出された水素濃度６３％よりも低い６・５％だったが、東電は「格納容器の水素濃度は１％未満なので、配管の濃度は想定より高い」としている。事故直後に発生した水素が配管に押し込められていた可能性が高い。

The concentration was 6.5%, lower than 63% detected in the pipe in Reactor 1 the other day. Nonetheless, TEPCO says "Normally the concentration of hydrogen gas within the Containment Vessel is less than 1%. The concentration detected in the pipe is higher than expected". It is likely that hydrogen gas generated right after the accident remains in the pipe.

　この配管には、格納容器内のガスに含まれる放射性物質をフィルターで除去するシステムを新設する予定で、設置後に水素を抜く。空気中に４％以上の水素と５％以上の酸素が同時にあると爆発の危険性が高まる。

TEPCO plans to install a gas management system to filter out radioactive materials in the gas inside the Containment Vessel. After the installation TEPCO plans to remove hydrogen gas. If there are more than 4% hydrogen and more than 5% oxygen in the atmosphere, a chance of explosion increases.

After the installation?

However, looking at TEPCO's diagram (from press handout on 10/12/2011), this pipe is different from the one they found 63% concentration in Reactor 1. The Reactor 1 pipe was originally used for the core spray system - i.e. it was a pipe for water, so were the valves. But the Reactor 2 pipe and valves on the pipe are for the flammable gas, which I suspect has different specs.

It looks like the ever-incurious TEPCO decided to use the pipe for gas in Reactor 2, probably correctly assuming the valves would stop hydrogen gas from the CV better than the valves for the core spray system.

Tweet