¶¶Òõ´«Ã½ÔÚÏß

UPDATE 8: 9.48pm GMTÌý

Ìý

Nuclear reactors shut down during today's massive earthquake in Japan. Work to stabilise three reactors at Fukushima Daiichi continues into the morning.Ìý

Ìý

The magnitude 8.9 quake hit at 2.46pm, centred offshore of the city of SendaiÌýon the eastern cost of Honshu island. Serious secondary effects followed including a significant tsunami causing widespread destruction. The quake comes just two days after one of magnitude 7.3 also offshore in the same general region.

Ìý

The Japan Atomic Industry Forum (JAIF)Ìýissued a notice saying all reactors in the north-eastern part of Japan had shut down automatically. Japanese prime minister Naoto Kan made a statement on television in which he noted that there had been no early indication of any radioactive release.Ìý

Ìý

Tohoku Electric Power Company's Onogawa 1 suffered a fire in the non-nuclear turbine building which took eight hours to extinguish. A minor fire burned in a non-nuclear service building of Tepco's Fukushima Daini 1 but this was extinguished within two hours.

Ìý

A tsunami warning was issued for most of the Pacific Ocean, including Taiwan, but reactors there operated normally throughout. There was no tsunami concern for nuclear power plants in South Korea or China.

Ìý

At Tokyo Electric Power Company's (Tepco's) Fukushima Daini 1, an increase in reactor containment pressure wasÌýnoted around 6pm, and "assumed to be caused by leakage of reactor coolant in the reactor containment" this ledÌýTepco to notify government of another emergency status.ÌýAs of 11pm Tepco said it had not detected additional radiation, making a coolant leak seem less likely.

Ìý

Fukushima DaiichiÌý

Ìý

A more serious situation emerged at Tepco's nearby Fukushima Daiichi power plant, after the sudden stoppage of emergency diesel generators. These had started as expected upon automatic reactor shutdown, but stopped after one hour leaving units 1, 2 and 3 with no power for important cooling functions.

Ìý

This led the company to notify the government of an 'emergency' situation, which allows local authorities to take additional precautionary measures.ÌýAn evacuation was subsequently ordered of over 1000 people living within three kilometres while engineers worked to restore power.

Ìý

Almost nine hours later, an announcement from the Ministry of Economy, Trade and Industry said that three of four mobile power supplies had arrived at Fukushima Daiichi and cables were being set up to supply emergency power. Other power modules were in transit by air.

Ìý

However, pressure inside the containment of unit 1 had been steadily increasing over the time that emergency core cooling systems had not been active. Tepco reported at 2am that pressure had increasedÌýto around 600 kPa, compared to normal operating levels of 400 kPa.

Ìý

The company then announced a decision to reduce the pressure within containment "for those units that cannot confirm certain levels of water injection" by the safety systems. "We will endeavor to restore the units and continue monitoring the environment of the site periphery."

Ìý

An International Atomic ¶¶Òõ´«Ã½ÔÚÏß Agency announcement at 4.20am confirmed the work to restore power using mobile power supplies. It noted the increase in pressure at unit 1 and said that this would be relieved by a controlled venting operation, "which will be filtered to retain radiation within containment."

Ìý

Ìý

Ìý

Researched and written

by ¶¶Òõ´«Ã½ÔÚÏß Nuclear News

Ìý