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Japan:Hydrogen concentrations prevented in Fukushima reactors + Related Articles

Friday, December 2, 2011

Laaska news  Dec. 2, 2011
TEPCO injects nitrogen into pressure vessels
TEPCO: Cooling stoppage info was not shared

Photo: EPA  

Nitrogen is being pumped into the crippled Fukushima reactors to prevent growth in hydrogen concentrations and likely subsequent explosions.

According to the nuclear plant operator company, the Tokyo Electric Power Company, a minor increase in the concentration of hydrogen had been detected in the pipe works of power generating units by the middle of October.

Although the probability of a blast is insignificant, experts decided to remain on the safe side and pump nitrogen into the internal reactor area, to prevent further growth in hydrogen concentrations.

The Fukushima hydrogen blasts as a result of the March earthquake did major damage to the power generating units and destroyed the buildings of three reactors.    



TEPCO injects nitrogen into pressure vessels

The operator of the Fukushima Daiichi nuclear power plant has started injecting nitrogen, an inert gas, into the pressure vessels of the crippled reactors to prevent another hydrogen explosion.

In late October, Tokyo Electric Power Company began extracting gases from the containment vessel of the No.2 reactor to remove radioactive substances. During the work, TEPCO found hydrogen accumulating in parts of the reactor at a density of up to 2.9 percent.

TEPCO started pumping nitrogen into the pressure vessels of the No.1, 2, 3 reactors on Thursday to lessen the concentration of hydrogen.

The density of hydrogen accumulating in the containment and pressure vessels is thought to be below 4 percent, the level where an explosion could occur.

TEPCO says the nitrogen injection will push out hydrogen and reduce its concentration.

Keeping hydrogen density low is an indispensible condition in the second step of the process decided upon by the government and TEPCO to resolve the nuclear accident. They are aiming to achieve a state of cold shutdown for the reactors by the end of the year.

The Nuclear and Industrial Safety Agency plans to assess how well TEPCO can manage hydrogen levels.


TEPCO: Cooling stoppage info was not shared

A miscommunication between workers at the Fukushima Daiichi nuclear plant could have delayed a response to the accident on March 11th.

The operator says the plant’s chief did not know for several hours that the only backup cooling system for the Number 1 reactor was manually shut down on the day of the earthquake and tsunami.

NHK has obtained Tokyo Electric Power Company’s interim report on the accident to be released on Friday.

The report says workers in the reactor’s control room stopped an emergency cooling system shortly after 6 PM. It says the plant chief, Masao Yoshida, and others in the facility’s office building were unaware of the manual shut-down.

TEPCO says it was not until around midnight that the plant chief noticed the system was not working. A rise in the radiation levels at the reactor building alerted him to the possibility of damaged fuel rods.

The emergency system uses steam to cool down a reactor when there is no electricity supply. It was the only workable cooling system at the reactor after the plant lost its major power sources.

The report says the misunderstanding occurred because a malfunctioning gauge failed to show that the water level had dropped, exposing the fuel rods.

TEPCO estimates that damage to the exposed fuel rods occurred about 4 hours after the quake. It says this generated large amounts of hydrogen that caused the first explosion at the plant on the following day.


Laaska News.