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Japan:Hydrogen level falls at Fukushima plant +Related Articles

Monday, October 10, 2011

Laaska News Oct. 10,2011


The operator of the troubled Fukushima Daiichi nuclear power plant says the level of hydrogen in a pipe at the No. 1 reactor has become low enough to make an explosion unlikely.

Tokyo Electric Power Company, or TEPCO, on Sunday finished removing hydrogen from inside a pipe connected to the reactor’s containment vessel.

The utility had been injecting nitrogen into the pipe to remove hydrogen since Saturday.

Last month, the hydrogen levels inside the pipe were found to account for between 61 and 63 percent of the total gas present, posing a risk of explosion.

TEPCO says the hydrogen level is now low enough and even if it were to rise again, it would not exceed 4 percent — the lowest level that poses a risk of explosion.

On Sunday evening, TEPCO cut 2 points of the pipe to allow the installation of a device that filters radioactive substances inside the containment vessel.

The cutting operation was about 2 weeks behind the schedule the company set for its plan to contain the nuclear accident at the plant.

TEPCO says it wants to install and start operating the device as early as possible.




Removal of hydrogen continues at Fukushima plant

Tokyo Electric Power Company will try to remove more hydrogen from the troubled Fukushima Daiichi nuclear power plant on Sunday. The density of the gas increased in pipes connected to the No. 1 reactor after a significant drop on Saturday.

Last month, TEPCO found that hydrogen had built up inside pipes leading to the No. 1 reactor containment vessel and its density was between 61 and 63 percent of the total gas present.

This poses a problem because releasing high densities of hydrogen outside the reactor building could cause another explosion.

On Saturday, TEPCO spent one hour removing hydrogen, while at the same time injecting nitrogen to the pipes to reduce the risk of an explosion.

About half an hour later, the company found the percentage of hydrogen had dropped to nearly zero.

However 2 hours later, the density was measured at 3.9 percent. Even though TEPCO says an explosion is unlikely, hydrogen at a density of over 4 percent could cause a blast when mixed with oxygen.

TEPCO believes that the hydrogen level rose because gas accumulated in the upper part of the pipes may have redistributed internally.

Sunday, October 09, 2011

Japan:Temperatures drop at Fukushima damaged reactors

Japan:Removal of hydrogen starts at Fukushima plant
Laaska News.