Stable Cooling Achieved at Fukushima Daiichi NPS: TEPCO Turns ...

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Stable Cooling Achieved at Fukushima Daiichi NPS: TEPCO Turns ...

25 July 2011

Stable Cooling Achieved at Fukushima Daiichi NPS:

TEPCO Turns to Step 2 Target of Cold Shutdown

On July 19, a press conference was held by the response office that is in charge of

handling the March 11 accident at the Fukushima Daiichi Nuclear Power Station (NPS),

owned and operated by the Tokyo Electric Power Co., Inc. (TEPCO). The response

office is an integrated effort between the Japanese government and TEPCO.

At the conference, held at TEPCO’s head office, Goshi Hosono, Japan’s Minister for

Nuclear Accidents, joined others in reporting on the progress of the roadmap toward

the reactors’ restoration. He confirmed the achievement of the target set for the three

months in Step 1 of the roadmap, namely, a steady decline in radiation dosage.

During the period of Step 1, the maximum registered dosage exposure was

approximately 1.7 mSv/year at monitoring posts and other places around the periphery

of the plant premises (the Cs134 and Cs137 levels were slightly higher than the dose

limits for the general public). Considering the level at the beginning of the accident, that

was deemed a sufficient decline for the target for Step 1 to be considered achieved,

allowing a transition to Step 2. Assuming that radioactivity measured in the reactor

buildings has all been released, the level is now down to about 0.5 millionths what it

originally was when the accident occurred.

The target of stable cooling of the reactors has also been met, as follows:

-- The heat generated in the reactors is being steadily removed.

-- A facility is in operation to treat highly radioactive water, enabling the injection of

treated water into the reactors without increasing the amount of accumulated water.

-- Such water injection appears reliable.

-- Nitrogen is being injected into the containment vessels and hydrogen explosions

have been prevented.

The main goal of Step 2 is to bring the reactors to states of cold shutdown. However,

Minister Hosono noted, “We are not yet optimistic,” emphasizing that the government

would continue to prepare for the unexpected.

As for the accumulated highly radioactive wastewater, enough storage places have

been secured to prevent it from flowing out of the premises. The facility to treat it began

operating in June, with a total of 23,480 tons treated so far. Various efforts have been

made to prevent the contamination of the sea, including using zeolites to purify the

harbor into which the water flowed, as that material can absorb cesium. Step 2 will

include focusing on the stable operation of the facility so as to reduce the total amount

of accumulated wastewater.

Work to install a reactor-building cover began at Unit 1 on June 28, in an effort to

mitigate the scattering of radioactive substances, in addition to dispersing inhibitors and

removing debris. The environment for the approximately 1,000 workers at the site has

also been enhanced to improve their well-being and morale: a new facility to let them to

take breaks and rest, improved meals, and a newly-built temporary dormitory to let

them sleep.

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25 July 2011

The period set for Step 2 is unchanged, at about three to six months. During that time,

the government will work on completing safety guidelines to prepare for medium-range

issues. Also, TEPCO will issue a plan to manage the plant facilities based on the

government’s safety determinations, in preparation for the removal of fuel from spent

fuel storage pool and others.

On July 19, the government’s Nuclear Emergency Response Headquarters released a

report on progress in assisting residents affected by the nuclear accident. In zones

where residents were ordered to evacuate within a certain period, the vast majority of

residents in five designated municipalities have already done so, including 97% in

Iidate Village and 99% in Kawamata Town. Also, some 210,000 residents have

undergone screening tests to evaluate their radiation dosage, with no adverse health

effects found.

Source: Tepco

http://www.tepco.co.jp/en/press/corp-com/release/11071905-e.html

Editor: Hisako Sakurai, JAIF

All Rights Reserved by JAIF. The material contained herein can be used by subscribers for internal

purposes and by the media, provided JAIF is quoted as the source. Written permission is required to post

JAIF material on publicly-accessible electronic information systems. ©

Editorial Office: Department of Information & Communication, JAIF http://www.jaif.or.jp/english/

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