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Thursday, March 31, 2011

Ideas floated to stanch leak of radiation

Storing tainted water in tankers, draping reactors with fabric eyed


By KAZUAKI NAGATA and KANAKO TAKAHARA
Staff writers

With operations to pump out massive amounts of contaminated water at the crippled Fukushima No. 1 nuclear plant running into trouble, new ideas surfaced Wednesday to move the effort forward, including storing the tainted water in tankers and covering the reactor sites with fabric shrouds.

News photo
Seeking your understanding: Tokyo Electric Power Co. Chairman Tsunehisa Katsumata (center), flanked by Vice Presidents Takashi Fujimoto (left) and Sakae Muto, apologize at Tepco's Tokyo headquarters Wednesday. KYODO PHOTO

"To stabilize the situation at the plant and keep radioactive contamination at a minimum, we are asking experts to consider various" methods, Chief Cabinet Secretary Yukio Edano told a news conference.

While many ideas are under consideration, no concrete decisions have been made, he said.

One of the ideas being mulled would be to cover the walls and ceilings of the reactor buildings damaged in explosions with special fabric capable of containing radiation.

However, the feasibility of the proposed ideas had yet to be studied.

Hidehiko Nishiyama of the Nuclear and Industrial Safety Agency said various options to remove the contaminated water are being discussed, but the work will continue based on what is available at the site.

Tokyo Electric Power Co. Chairman Tsunehisa Katsumata, appearing for the first time since the crisis began, told a news conference that although it will probably be hard to bring tankers near the reactors, "if there are good ideas, we would like to examine them."

Katsumata said scrapping the plant's four troubled reactors is inevitable, and Tepco will face a heavy nuclear disaster compensation tab.

His comment suggested that reactors 5 and 6, which are less damaged, may be able to fire up again in the future.

Edano, however, quickly ruled out this possibility.

"I believe (scrapping all six reactors) is very clear from the viewpoint of society. That is my perception," he said.

Tepco has been trying to pump out the accumulated toxic water in the basements of turbine buildings for reactors 1 through 4, as well as from the trenches below the turbine buildings of reactors 1, 2 and 3.

As for the water in the No. 1 building, Tepco had been pumping it into a storage tank since March 24 but stopped work Tuesday after it became full. The depth of the water in the basement has decreased to about 20 cm from an earlier 40 cm, the NISA said.

But work to remove the water at reactors 2 and 3 has yet to start because the storage tanks for those reactors are full. The water in the basement of the No. 2 turbine building and in its trench contains especially high-level radiation, with 1,000 millisieverts per hour detected.

The limit for total radiation exposure per year set by the health ministry for each nuclear plant worker is 100 millisieverts, although the level has been raised to 250 millisieverts for the Fukushima plant workers, given the graveness and urgency of the crisis.

The high level of contamination indicates the water may have come in contact with the partially melted fuel rods inside the No. 2 reactor's pressure vessel and leaked from an unknown location, although NISA has said the essential components of the reactor, its core and containment vessel, are probably still intact.

Radioactivity levels found in the environment around the Fukushima plant appeared to be rising.

The monitoring data collected at 1:55 p.m. Tuesday 330 meters south of the drain outlets for the No. 1 and 4 reactor buildings detected radioactive iodine-131 levels in the seawater 3,355 times above the government standard — the highest ever detected.

The level had actually declined several days ago, to some 250 times above the standard, according to data from Sunday, indicating the current levels detected were flowing to the sea from unknown routes.

"The level has been increasing . . . it is important to find out where (radioactive materials) are coming from and prevent the figure from rising," Nishiyama said.

In a related development, Tepco said its president, Masataka Shimizu, who hasn't appeared since March 13, was hospitalized Tuesday for hypertension and dizziness while tackling the crisis.

Shimizu has not appeared in public since attending a news conference on March 13, prompting a public backlash. Katsumata's Wednesday appearance was his first.

Information from Kyodo added



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