Efforts to stabilize ravaged reactor units at the Fukushima Daiichi nuclear complex were delayed again today by high levels of radiation in water from reactors that has collected in adjacent turbine buildings.

The International Atomic Energy Agency in its Sunday update said the condition at the plant remained "very serious."

It said the restoration of offsite electric power continues, providing lighting to the central control rooms of units 1, 2 and 3, and fresh water continues to be injected into the reactor pressure vessels of all three units in an effort to reduce concentrations of salt from seawater on fuel rods that could impede cooling efforts. There was no report from Tokyo Electric Power Co. (TEPCO) about the number of critical reactor systems that now are operating normally under electric power.

But TEPCO had not determined Sunday how to pump water from the turbine building for reactor No. 3 in order to reduce radiation levels there that threaten workers. On Thursday, three workers installing power cables in the building suffered severe radiation exposure after walking in water with high levels of radiation. The workers -- TEPCO contract employees -- had not been told that high levels of radioactivity had been found inside another turbine chamber, Asahi Shimbun reported.

Radioactivity at a pool of standing water inside the No. 2 turbine chamber exceeded 1,000 millisieverts per hour, Japan's Nuclear and Industrial Safety Agency said Sunday. Even with the raised exposure limit of 250 millisieverts, the recorded level on Sunday requires that workers can operate for only 15 minutes at a time before leaving the area, Asahi Shimbun reported.

The presence of highly contaminated water in the Unit 1 turbine building has delayed efforts to connect outside electrical power to cooling pumps servicing that reactor's pressure vessel, the newspaper said. Water pumped from fire trucks remains the backstop procedure.

Pumping out excess water

TEPCO said on Sunday it detected 100,000 times the normal density of radioactive substances in the leaked water in the No. 2 reactor's turbine building. The utility first reported readings of 10 million times normal levels at the No. 2 unit, but revised the report downward after the Nuclear and Industrial Safety Agency order it to review the calculation, the NHK World news service reported.

Michiaki Furukawa, a nuclear chemist and a board member of the Citizens' Nuclear Information Center, a Tokyo-based watchdog group, said exposure to 1,000 millisieverts of radiation would induce nausea and vomiting, while exposure to triple that amount could be lethal, The New York Times reported.

Naoki Sunoda, a spokesman for TEPCO, said that since the crisis began, 19 workers had been exposed to radiation levels of 100 millisieverts, the original safely limit, since raised to 250 millisieverts for the workers at the site, who now number about 1,000.

According to the Japanese Prime Minister's office on Sunday, TEPCO has started to remove water from the unit No. 1 turbine building to its main condenser and were making preparations to do the same at Unit 2. The condensers cool steam from the reactors that passes through the power-generating turbines and recovers water that is recycled into the reactor's pressure vessel to be heated into steam again. "Removal of water from the turbine buildings is an important step to continue power restoration to the plant.," the IAEA noted.

While TEPCO was able to accelerate transfer of contaminated water from the basement of the Unit 1 turbine building into the turbine condenser for storage after adding more pumps, it could not do the same at units 2 and 3 because the condenser pools were nearly full. TEPCO said it was considering pumping that water into adjacent pools to make space for removal of contaminated water from the turbine building basements in those units, NHK said.

Spent-fuel pools appear stabilized

In its latest update on the reactors' spent-fuel pools, on Monday, TEPCO reported that pools in units No. 2 and 4 appeared to be filled with water. The water temperature in the Unit 2 pool was 56 degrees Celsius on Sunday afternoon local time. TEPCO said it plans to begin pumping fresh water into spent fuel pools tomorrow.

High levels of radioactivity have been found in seawater outside the Fukushima plant, TEPCO said Levels of iodine-131 collected Sunday 30 meters from a water outlet from the plan were more than 1,000 times higher than the normal level.

But radioactivity levels in the air were reported to be decreasing at most observation points around the plant, NHK reported today. The reading in Fukushima City, 65 kilometers northwest of the nuclear power plant, was 3.84 microsieverts per hour at 1 a.m. The annual total limit of radiation exposure considered safe for humans is 1,000 microsieverts, according to the International Commission on Radiological Protection, NHK said.

David Lochbaum, nuclear safety director at the Union of Concerned Scientists said Friday the cause or causes of the contamination that injured the three workers at Unit 3 was uncertain.

"The turbine building is normally isolated from both the Unit 3 reactor core and the Unit 3 spent-fuel pool," he said. "There were reports of damage to fuel in the Unit 3 reactor core, and also to damage to fuel in the Unit 3 spent fuel pool. But it's not clear at the moment from the data we've seen how the water in the basement of the Unit 3 turbine building became contaminated. We haven't seen any clear signs whether it came from the reactor core or from the damaged fuel in the spent-fuel pool.

"They were adding water from above and from fire trucks to the spent-fuel pool in Unit 3 and it's possible that water drained from that location down to the turbine building. There are also pipes that connect the reactor vessel in the primary containment to the turbine building that were normally isolated in situations like this, but might have been a pathway for the radiation to get from the containment to the turbine building. We're just not sure from the data so far."

Inconsistent instrument readings also cloud the picture of conditions at the site, he said. At one point Friday, Japanese authorities expressed fears of a breach of the containment structure at Unit 3, but pressure instrument readings there indicate that wasn't the case, Lochbaum said. "There's not a lot of instrumentation available. There's not a lot of access available for workers to go through the facility and more accurately assess conditions in lieu of the instrumentation that's spotty at best. So, I think it's reflective of it's going to take a while to fully identify what's happened there."