Fukushima : Risques d’explosion dans les conteneurs contenant les boues radioactives stockées

By HIROMI KUMAI , Traduction Par

23/05/2015

Source : http://ajw.asahi.com

Fukushima Governor Masao Uchibori, right, is briefed on the ALPS system that removes radioactive substances from contaminated water at the Fukushima No. 1 nuclear power plant in November. (Pool)

Fukushima Governor Masao Uchibori, right, is briefed on the ALPS system that removes radioactive substances from contaminated water at the Fukushima No. 1 nuclear power plant in November. (Pool)

Les 1300 citernes en polyéthylène de 1,80m de haut sur 1,50m de diamètre où sont stockées les boues contaminées résiduelles après filtrage de l’eau (par le système ALPS) posent un risque d’EXPLOSION d’hydrogène. En effet, des gaz, dont de l’hydrogène, se forment au fond de ces citernes sous l’action des radionucléides ; le volume augmente et des fuites se produisent, au niveau des couvercles ou par des fissures. Les couvercles devaient être prévus pour laisser échapper les gaz, mais TEPCO vient de se rendre compte que ça n’était pas le cas pour toutes les citernes.


TEPCO a initialement trouvé des fuites sur 26 citernes puis sur 278, enfin sur 333, soit environ 1/4 ou un peu plus de l’ensemble des conteneurs. L’électricité statique pourrait suffire à provoquer une explosion. Ces boues résiduelles sont extrêmement radioactives.
 

 

Risk of hydrogen explosion from leaking containers at Fukushima plant

By HIROMI KUMAI/ Staff Writer

Inspections of containers holding contaminated water at the Fukushima No. 1 nuclear power plant found that at least 10 percent have leaks, which could trigger a hydrogen explosion.

Tokyo Electric Power Co., the plant’s operator, reported its findings at a meeting with a study group from the Nuclear Regulation Authority on May 22. It said no radioactive water was found to have escaped outside the concrete structures that encase the containers.

According to TEPCO, there were about 1,300 such containers at the plant as of May 20.

They store waste water from the ALPS (advanced liquid processing system) equipment that removes radioactive substances from contaminated water.

The containers, which are made of polyethylene, are 1.8 meters high and have diameters of 1.5 meters.

The first leak was discovered in a lid on April 2.

TEPCO began inspecting others to see if they had similar problems. Of the 278 it had examined by May 20, it found 26 had some sort of leak or were bleeding from their lids.

The operator said the leaks and bleeding were likely caused by hydrogen and other types of gases that resulted from the water’s exposure to high levels of radiation.

Such gases appear to have accumulated in sediment at the bottom of the containers, expanding the volume of the liquid.

An NRA official said the accumulating hydrogen poses a potential danger.

“If the concentration level is high, a spark caused by static electricity could cause a container to explode,” the official said.

Although all the lids of the containers were supposed to be fitted with pressure-release valves to allow gasses to escape, TEPCO’s survey found that one did not have the mechanism.

Further review of the delivery records for the containers showed there may be as many as 333 that are also defective, a TEPCO official said.

By HIROMI KUMAI/ Staff Writer
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