Workers try to trap water from reactors Compiled from Kyodo news, AP

Steel plates, silt fence go up in bid to enclose toxic seawater.

Workers trying to stabilize the Fukushima No. 1 nuclear plant Saturday started installing an offshore enclosure behind the facility to prevent radioactive runoff produced by emergency cooling operations from further contaminating the Pacific Ocean.

AP Photo/Wally Santana

Fukushima Governor Yuhei Sato explains the government's plans at an evacuee center for leaked radiation from the damaged Fukushima nuclear facilities, Monday, March 21, 2011, in Fukushima.

Japanese Trade Minister Banri Kaieda

Trade minister Banri Kaieda meanwhile met with Fukushima Gov. Yuhei Sato in the city of Fukushima in the morning and had plans to visit the crisis-hit power plant later in the day. The visit, aimed at encouraging the crisis-response efforts and checking on the plant's damaged reactors, would be the first by a Cabinet minister since the six-reactor plant was rocked by a historic quake and tsunami that led to hydrogen explosions and radiation leaks in mid-March.

Tokyo Electric Power Co. plans to enclose the seawater intake for reactor 2 with seven steel sheets and to deploy three 120-meter-wide "silt fences" near it and two other places to contain the toxic water being created by the emergency reactor-cooling strategy.

In a minor victory Wednesday, the beleaguered utility managed to plug a cracked pit in the same area that was leaking tons of deadly radioactive water from underneath the reactor into the sea.

But with little warning, it also began dumping about 9,000 tons of less radioactive water into the sea to free up space to store the highly toxic water that has flooded reactor No. 2's turbine building and a tunnel outside it. The water must be pumped out in order to repair its vital cooling systems.

The level of radioactive iodine-131 in seawater near the intake plunged from 7.5 million times the legal limit on April 2 to 63,000 times the limit a day after the pit leak was plugged.

There was no mention, however, of what happened to the more worrisome levels of cesium. On April 2, there were 2 million times the permissible amount of cesium-134 and 1.3 million times the allowable amount of cesium-137 in that water. Cesium has a much longer half-life of 30 years.

Tepco is now pumping nitrogen, an inert gas, into the No. 1 reactor to purge it of hydrogen, which may accumulate and explode if mixed with oxygen. It also is enhancing the purity of the gas to reduce the amount of oxygen mixed in it.

Tepco said it will use a small unmanned helicopter to survey damage at the plant as early as Sunday, depending on the weather. The drone is needed to view the damage in all four of the reactors still in danger because the radiation levels are too high for humans to approach.

Also Saturday, the Japanese nuclear safety agency called on the nation's power utilities to have at least two backup diesel generators on standby for all reactors, even stable reactors that have undergone "cold shutdowns" or are undergoing fuel replacement.

The move was ordered after all three diesel generators failed at the Higashidori power plant in Aomori Prefecture when Thursday's 7.1-magnitude aftershock automatically caused its reactors to shut down.

The agency's previous rule, which required utilities to have just one diesel generator on standby in situations including cold shutdowns, was "not enough, I must say," said Hidehiko Nishiyama, the main spokesman for the Nuclear and Industry Safety Agency.

The nuclear crisis erupted after last month's 9.0-magnitude earthquake and tsunami knocked out external power and the backup generators at the Fukushima No. 1 power plant, crippling its cooling systems and allowing the reactors to overheat.

Nishiyama also displayed candor about the missteps and failures that led to the disaster.

"We'd 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 upon ourselves.

"We need to review everything to ensure safety, regardless of precedents," he said.

Adding to concerns on food safety, the government announced it will ban farmers from planting rice in soil contaminated by radiation.

The ban will apply to any soil found to contain cesium exceeding 5,000 becquerels per kilogram, and farmers prevented from growing rice will be compensated, the farm ministry said Friday.

So far, soil exceeding the new limit has been found in only two places in the village of Iitate, Fukushima Prefecture, which is about 40 km from the stricken power plant.

Meanwhile, at the U.S. Yokota Air Base in western Tokyo, a special U.S. Marine Corps unit trained to rescue people in chemical, biological or nuclear emergencies held a joint drill with its Self-Defense Forces counterparts Saturday and said it stood ready to help out if needed around the crippled Fukushima plant.

The 145-member Chemical Biological Incident Response Force flew in last week from the United States. It is the unit's first overseas deployment, but does not signal heightened alarm in Washington about Fukushima No. 1, CBIRF members said. It also has no plans to go north, closer to the nuclear plant.