Japan's chief cabinet secretary says a hydrogen explosion has occurred at Unit 3 of Japan's stricken Fukushima Dai-ichi nuclear plant. The blast was similar to an earlier one at a different unit of the facility.
Yukio Edano says people within a 20-kilometre radius were ordered inside following Monday's. AP journalists felt the explosion 50 kilometres away.
A massive column of smoke was seen belching from the plant's No. 3 unit Monday. The No. 3 Unit reactor had been under emergency watch for a possible explosion as pressure built up there following a hydrogen blast Saturday in the facility's Unit 1.
Meanwhile, soldiers and officials in northeastern Japan are warning residents that the area could be hit by another tsunami and are ordering residents to higher ground.
Sirens around the town of Soma went off late Monday morning and public address systems ordered residents to higher ground.
Kyodo News Agency said the tsunami could be 3 metres high, citing Fukushima prefectural officials.
On Sunday, Japanese officials had warned of a possible second explosion at a nuclear plant crippled by the earthquake and tsunami as they raced to stave off multiple reactor meltdowns, but they provided few details about whether they were making progress. More than 180,000 people have evacuated the area, and up to 160 may have been exposed to radiation.
Four nuclear plants in northeastern Japan have reported damage, but the danger appeared to be greatest at the Fukushima Dai-ichi nuclear complex, where one explosion occurred Saturday and a second was feared. Operators have lost the ability to cool three reactors at Dai-ichi and three more at another nearby complex using usual procedures, after the quake knocked out power and the tsunami swamped backup generators.
Chief Cabinet Secretary Yukio Edano said Sunday that a hydrogen explosion could occur at Dai-ichi's Unit 3, the latest reactor to face a possible meltdown. That would follow a hydrogen blast Saturday in the plant's Unit 1.
“At the risk of raising further public concern, we cannot rule out the possibility of an explosion,” Mr. Edano said. “If there is an explosion, however, there would be no significant impact on human health.”
Operators have been dumping seawater into units 1 and 3 in a last-ditch measure to cool the reactors. They were getting water into the other four reactors with cooling problems without resorting to corrosive sea water, which likely makes the reactors unusable.
Mr. Edano said residents within about 20 kilometres of the Dai-ichi plant were ordered to evacuate as a precaution, and the radioactivity released into the environment so far was so small it didn't pose any health threats.
Such statements, though, did little to ease public worries.