By the CNN Wire Staff

April 4, 2011 8:05 a.m. EDT
A Tokyo Electric Power Company picture from April 2 shows water gushing from the cracked concrete shaft.
A Tokyo Electric Power Company picture from April 2 shows water gushing from the cracked concrete shaft.
STORY HIGHLIGHTS
  • NEW: Water from a treatment facility and around four reactors being dumped
  • Officials say this is to create space for radioactive water from near the No. 2 unit
  • The official calls the step “unavoidable,” saying it’s needed to ensure safety
  • Basement water threatens “stability” of the Nos. 5 and 6 units’ cooling systems

Tokyo (CNN) — The dumping of tons of radioactive water from a waste treatment facility at the crippled Fukushima Daiichi nuclear facility into the ocean has started, Tokyo Electric Power Company officials said Monday. The additional dumping of water from reactors Nos. 5 and 6 will begin within hours, they said.

In all, about 11,500 tons of radioactive water that has collected at the nuclear facility will be dumped into the Pacific Ocean, officials said Monday, as workers also work to deal with a crack that has been a conduit for contamination.

These are the latest, but hardly the only challenges facing workers at the embattled power plant and its six reactors, which have been in constant crisis since last month’s ruinous earthquake and tsunami.

Officials with the Tokyo Electric, which runs the plant, proposed Monday afternoon releasing excess water that has pooled in and around the Nos. 3, 4, 5 and 6 reactors into the sea. But most of the dumped water — 10,000 tons — will come from the plant’s central waste treatment facility, which will then be used to store highly radioactive water from the No. 2 unit, an official with the power company said.

Japanese Chief Cabinet Secretary Yukio Edano called the dumping “unavoidable,” even though this liquid was most likely contaminated in the process of trying to cool nuclear fuel rods.

The build-up of water could cause problems around the nuclear facility, which is 240 kilometers (150 miles) north of Tokyo, Edano said Monday.

Authorities have made a priority of dealing with water from the No. 2 unit, some of which has been gushing into the sea through a crack in a concrete shaft.

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We need to stop the release into the seawater as soon as possible
–Japanese Chief Cabinet Secretary Yukio Edano

“The radioactivity level is very high near the No. 2 reactor, and we know this. We have to stop the leak as early as possible to prevent this from going into the sea,” said Edano. “The radioactivity level is much less in the water from the Nos. 3 and 4 units.”

“For the safety of the (No. 2) reactor, we have no choice,” he added.

Neither attempt to fill the 20-centimeter (8-inch) crack outside the No. 2 reactor’s turbine building — on Saturday by pouring in concrete, then Sunday by using a chemical compound mixed with sawdust and newspaper — was successful.

As they mull other ways to cut off the leak at its source, workers will install a silt fence along a damaged sea wall surrounding the plant, Nishiyama said. The aim of this screening, usually used to halt erosion at construction sites, is to prohibit the spread of radioactive particles into the sea.

Workers also have injected a dye tracer into the water to allow them to track the dispersal of such particles, the spokesman added.

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Addressing the issue quickly is critical because officials believe it is a source of alarmingly high radiation levels in seawater near the plant, as well as in nearby groundwater.

Complicating the situation is the fact that, in some cases, authorities don’t even know how much radiation is getting out.

After some high-profile errors, little new information on water, ground and air radiation has been released since Thursday. One reason is that the dosimeters being used don’t go above 1,000 millisieverts per hour, said Junichi Matsumoto, an executive with Tokyo Electric.

Authorities know the water in the cracked concrete shaft is emitting at least that much radiation — which equates, at a minimum, to more than 330 times the dose an average resident of an industrialized country naturally receives in a year.

Plugging the external leak is job one, in order to prevent the outflow of radiation into the Pacific. But it may not be the most difficult, or important, task ahead.

Authorities still have to figure out how the tainted water got into the concrete shaft in the first place. The water had to come from somewhere, potentially traveling across melted-down nuclear fuel in the reactor’s core before somehow reaching the outside.

“We were assuming and hoping (that water) would stay in the containment vessel as vapor after being cooled,” Nishiyama, the nuclear safety official, said Sunday. “However, it may have flowed into the building, and then the trench.”

Determining why and how that happened — and what to do about it — may be “exceptionally challenging,” said physicist James Acton, with the Washington-based Carnegie Endowment think tank. Officials may have to inspect a complex array of pipes inside the dangerous radioactive environment inside the containment buildings.

The state of the Nos. 5 and 6 units is another new problem. Water in their turbine buildings’ basements threatens the power supply for the system used to cool nuclear material in these units spent fuel pools, said Edano. This makes it imperative to pump out that water, which will end up into the sea like that from around the Nos. 3 and 4 units.

“Though those reactors are stable at the moment, the growing water level in the turbine houses may disturb their stability,” said Edano.

The effort to keep the Nos. 1, 2 and 3 reactor cores and spent fuel pools cool took a step forward Sunday, when the electricity source powering those three units’ cooling systems was switched from a temporary diesel generator to a more permanent, external power supply, according to the International Atomic Energy Agency’s website.

Authorities hope this step, as well as preventing damage to the Nos. 5 and 6 units’ power supply, will help to minimize the prospect of any more radiation that might contaminate tap water or food.

Farmers have pushed for lower standards on radiation in food, calling them unnecessarily stringent. On Monday, Edano said these limits would not change, even as he outlined a process in which sales restrictions on certain crops, in certain areas, would be lifted if they test safe three times in a row.

In the long run, utility and government officials want to make sure the nuclear fuel, and the potentially cancerous materials it can release, never poses a threat again.

One option being considered, a Tokyo Electric spokesman said Monday, is to wrap some or all of the reactors’ containment buildings in massive amounts of sheeting. But for now, the aim is to make sure that the nuclear fuel rods do not overheat — and release more radiation into the air, water and ground.

“Finally, we (need to) establish a long-term policy to cool the reactors,” said Nishiyama, while acknowledging that much work needs to be done in the meantime.

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