From Kyodo
Tokyo Electric Power Co. started Saturday to install enclosing materials in the sea to prevent a further spread of highly radioactive water that seeped from a crisis-hit nuclear power plant, while continuing other efforts to stabilize Japan's worst nuclear crisis.
A Cabinet minister visited the Fukushima Daiichi Nuclear Power Station in Fukushima Prefecture on the same day for the first time since it was rocked by explosions and began emitting radioactive materials shortly after the March 11 quake and tsunami.
During his roughly 45-minute stay, Economy, Trade and Industry Minister Banri Kaieda encouraged workers manning an operational center on the premises and surveyed damaged reactors from inside a bus.
Before his visit to the plant, Kaieda, whose ministry promotes and regulates the nuclear power industry, told reporters the situation was far from being brought under control and expressed his resolve to contain it as soon as possible.
TEPCO, as the company is known, tried to enclose a seawater intake for the No. 2 reactor at the six-reactor plant with seven steel sheets and a ''silt curtain,'' while planning similar curtains at other locations nearby, such as near the intakes for the Nos. 1, 3 and 4 reactors.
The power supplier stopped the leakage of water highly contaminated with radioactive materials from near the intake for the No. 2 reactor on Wednesday. But the company, facing mounting environmental concerns, hopes that the installation will help prevent contaminated water from spreading outside the plant's bay.
The radioactive iodine reading was 63,000 times the legal limit in seawater near the intake a day after contaminated water stopped leaking into the sea.
The utility is also close to finishing the release into the sea of 10,000 tons of water containing relatively low-level radioactive materials. The discharge is aimed at helping resume work to restore the plant's key cooling functions, with priority placed on the No. 2 among the damaged Nos. 1 to 3 reactors.
''We must move highly contaminated water at the No. 2 reactor and elsewhere to a radioactive waste processing facility as soon as possible without leaking it into the sea,'' Kaieda told reporters back in Tokyo after the visit. ''The plant chief said it must be given the priority right now and I agree with him.''
To free up room to pool highly contaminated water that has flooded the No. 2 reactor's turbine building and prevented the stabilization efforts, the company has dumped about 8,300 tons of low-level radioactive water into the sea from the plant's waste processing facility, with an estimated 800 tons of water left to be discharged.
It also pumped out into the sea 1,300 of the 1,500 tons of low-level contaminated groundwater from the Nos. 5 and 6 reactors, expecting to complete the work on Sunday.
For the tainted water filling a tunnel near the No. 2 reactor, the utility will begin channeling it to a 3,000-cubic-meter container inside the turbine building on Sunday to reduce the risk of it seeping into the sea, the government's nuclear safety agency said.
TEPCO also continued to pump nitrogen, an inert gas, into the No. 1 reactor to prevent hydrogen from causing another explosion, while enhancing the purity of the gas to reduce the amount of oxygen mixed in it.
The utility said it will fly a small unmanned helicopter to survey the plant, possibly starting on Sunday depending on the weather, expecting it to capture images of damaged installations at the Nos. 1 to 4 reactors that workers cannot approach due to elevated levels of radiation.
Asked if the working conditions for workers at the plant have improved, Kaieda said in Tokyo that they are hardly enough but have improved ''to a fair degree,'' noting that many people still sleep in the corridors of a two-story antiseismic building on the plant's premises.
In a sign that workers remain worried about high levels of radiation at the plant, companies dispatching workers to the troubled nuclear plant have refused to adopt the government's provisionally raised limit on radiation exposure for nuclear plant workers dealing with a crisis.
The ceiling was lifted from 100 millisieverts to 250 millisieverts in an announcement made on March 15 by the Ministry of Health, Labor and Welfare to enable workers at the plant to engage in longer hours of assignments and to secure more workers, but officials of the companies other than TEPCO say those at the site would not accept the elevated limit.
Before visiting the plant, Kaieda met with Fukushima Gov. Yuhei Sato in the city of Fukushima and inquired about what the localities want the central government to do, partly because the government has directed those living within a 20-kilometer radius of the plant to evacuate to ensure their safety.
On the nation's atomic energy policy, the minister told reporters afterward, ''While I can't say at this point, we need to review standards to enhance safety.''
Also Saturday, Tohoku Electric Power Co. said a human mistake apparently caused the only functioning diesel generator at the Higashidori nuclear power plant in Aomori Prefecture to leak fuel, forcing the utility to stop it at one point following the 7.1-magnitude aftershock late Thursday of the March 11 deadly earthquake.
The operational failure prompted the Nuclear and Industrial Safety Agency earlier in the day to call on the nation's power suppliers to have at least two backup diesel generators on standby even when a reactor is in a stable condition called ''cold shutdown'' or undergoing fuel replacement.
The agency's previous rule that required the suppliers to have just one diesel generator on standby in situations like the cold shutdown was ''not enough, I must say,'' agency spokesman Hidehiko Nishiyama said at a news conference.
Two other diesel generators at the one-reactor Higashidori plant were undergoing maintenance at the time of the aftershock, according to the utility serving northeastern Japan.
The nuclear crisis erupted after last month's 9.0-magnitude earthquake and tsunami knocked out external power supplies and backup generators for cooling systems at the Fukushima Daiichi plant and allowed reactors there to overheat.
The agency's Nishiyama displayed candor about the missteps and failures that precipitated the disaster, saying, ''We had said all along that (nuclear power) was absolutely secure thanks to its multiple layers of protection and five-layer barriers, and I believed this, but we brought this situation onto ourselves.''
''We need to review everything to ensure safety, regardless of precedents,'' he said.
==Kyodo
