Japan put its top priority on Wednesday on efforts to cool down a plutonium-fuelled nuclear reactor, attempting at one stage to water-bomb the facility without success amid fears that authorities were running out of options to avert disaster.
The No.3 reactor is the only one of the quake-stricken Fukushima Daiichi plant's six reactor units to be powered with plutonium, which is far more hazardous to health than uranium, which is used to power the other five reactors.
High radiation levels had stopped a military helicopter from dumping water on the No.3 reactor, local media said. The plant's owner, Tokyo Electric Power , declined to comment.
It was not clear if the helicopter was trying to pour water on the reactor vessel or on an associated spent-fuel pool, a deep reservoir where spent nuclear fuel rods are kept. Public broadcaster NHK said the water was for the spent-fuel pool.
Later, Kyodo news agency quoted a government taskforce as saying it was unlikely the No.3 reactor had sustained major damage.
The number of workers at the complex has increased to 180, up from 50 a day earlier but still far less than the 800 that were deployed there immediately after Friday's devastating 9.0 magnitude quake and tsunami.
Debris on roads has hampering efforts to bring in equipment, and there are plans to bulldoze a road into another part of the complex, the No.4 reactor, which is the second priority.
"The situation at the No.4 reactor is not exactly a good situation but the No.3 reactor is a higher priority," a Tokyo Electric Power official told a media briefing.
On Tuesday, an explosion blew two holes in the wall of a building housing the No.4 reactor unit's spent-fuel pool, exposing it to the atmosphere.
Tokyo Electric also said it was not sure what was happening at the No.2 reactor, which saw a sudden drop in pressure.
The company said this might indicate it was being cooled or it could also be an ominous sign that there was a hole in the core container. Or it might just be a faulty pressure reading.
"We cannot with certainty say whether or not the core container is airtight," the company official said.
The company also said it was pouring water at the reactors No.5 and No. 6, but it was also not immediately clear into which parts of those two reactor units.
It did say, however, that temperatures at the spent-fuel pools in those reactors had risen slightly since Wednesday morning. There was water in the pools but it was having trouble circulating the water because of cooling-system problems.
There was no new data on temperatures of the spent- fuel pools at reactors No.1 to No.4.
Kashmir dispute can be resolved diplomatically, not militarily, Muhammet Balta says
Archaeologists have said that a design of clay warriors suggests close contact between east and west 1,500 years before Marco Polo
Claim mass starvation of Myanmar's Rohingya Muslim community is taking place under current lockdown
A communique issued by top party leaders after a four-day meeting in Beijing called on all its members to "closely unite around the CPC Central Committee with Comrade Xi Jinping as the core", Xinhua said.
New Delhi police said the official had been recruiting Indian nationals for two and a half years to spy for Pakistan's powerful Inter-Services Intelligence (ISI) in return for cash.
ISIL linked group shifted priorities from abducting foreigners based in Philippines to foreign-flagged tugboat crews
Technical hitch leads PNG's highest court to dismiss application from asylum seekers to be taken to Australia
South Korean gov’t to risk public wrath by reigniting talks on sharing military intelligence with former colonial ruler
Senior diplomats agree to work together in considering unilateral sanctions after Pyongyang’s 2nd nuclear test this year
2 Pakistani civilians killed by exchange of fire along border with India
More than 103,300 have lived in 9 camps along Thai-Myanmar border for over 20 years
Investigation team to decide if prosecution be carried out by country of one of those involved or at international level
Local officials believe abducted civilians were killed by fighters who support Syria-based extremist group ISIL
Immigration department directive bans airlines from bringing Cambodia National Rescue Party leader Sam Rainsy home
Philippines president tells Tokyo economic forum that visit to China focused on economic cooperation, not military matters
Shen Jui-chang, among 26 hostages freed from the crew of Naham 3 seized south of the Seychelles in March 2012, added he had constantly had a gun pointed at his head during his ordeal.