TOKYO, March 12 (Reuters) - Tokyo Electric Power Co plans to fill a leaking reactor at the Fukushima Daiichi power plant with sea water to cool it down and reduce pressure in the unit, Japan's top government spokesman said on Saturday.
"The nuclear reactor is surrounded by a steel reactor container, which is then surrounded by a concrete building," Chief Cabinet Secretary Yukio Edano said.
"The concrete building collapsed. We found out that the reactor container inside didn't explode."
Japan earlier in the day warned of a meltdown at the reactor at the plant, damaged when a massive earthquake and tsunami struck the northeast coast, but said the risk of radiation contamination was small.
"We've confirmed that the reactor container was not damaged. The explosion didn't occur inside the reactor container. As such there was no large amount of radiation leakage outside," he said.
"At this point, there has been no major change to the level of radiation leakage outside (from before and after the explosion), so we'd like everyone to respond calmly," Edano said.
"We've decided to fill the reactor container with sea water. Trade minister Kaieda has instructed us to do so. By doing this, we will use boric acid to prevent criticality."
Edano said it would take about five to 10 hours to fill the reactor core with sea water and around 10 days to complete the process.
Edano said due to the falling level of cooling water, hydrogen was generated and that leaked to the space between the building and the container and the explosion happened when the hydrogen mixed with oxygen there.
(Reporting by Leika Kihara, Kiyoshi Takenaka; Editing by Joseph Radford)
1340 CET 12 March 2011 Japan's Nuclear and Industrial Safety Agency (NISA) has informed the IAEA's Incident and Emergency Centre (IEC) that there has been an explosion at the Unit 1 reactor at the Fukushima Daiichi plant, and that they are assessing the condition of the reactor core.
The explosion was reported to NISA by the plant operator, Tokyo Electric Power Company (TEPCO), at 0730 CET. Further details were not immediately available.
Japanese authorities have extended the evacuation zone around the Fukushima Daiichi plant to a 20-kilometre radius from the previous 10 kilometres. At the nearby Fukushima Daini nuclear power plant, the evacuation zone has been extended to a 10-kilometre radius from the previous three kilometres.
The authorities also say they are making preparations to distribute iodine to residents in the area of both the plants.
The IAEA has reiterated its offer of technical assistance to Japan, should the government request this. The IAEA continues to liaise with the Japanese authorities, and is in full response mode to monitor the situation closely around the clock as it evolves.
Note - iodine is used as a for protection against radiation.
Snippets...
Nuclear safety agency rates the incident a 4 on the 1 to 7 International Nuclear and Radiological Event Scale, less serious than Three Mile Island, which was a 5, and Chernobyl at 7.
Toyota Motor Co says it will suspend operations at all 12 factories on Monday. Total insured loss could be up to US$15 billion (NZ$20.2 billion), equity analysts covering the industry say.
Tokyo Stock Exchange plans to open for trading as normal on Monday.
Around 10,000 residents are missing from the Japanese town of Minamisanriku, according to reports.
