Japan Earthquake/Tsunami

A BATTLE to prevent a ­Chernobyl-style nuclear disaster was being fought last night after an explosion hit a power station already damaged by the quake.

Debris spewed over hundreds of metres in the blast and a cloud ­enveloped the area, where 170,000 residents have been evacuated.

Four workers were injured in the explosion at the Fukushima plant’s No 1 reactor, and three were later taken to hospital with ­radiation exposure. Fears were ­growing last night that up 160 people may have been exposed.

The plant has also lost its ­emergency cooling system at a second reactor, Japan’s nuclear power safety agency said last night. The emergency ­system is no longer functioning at the No 3 reactor, and workers were trying to pump water up to the site.

Experts last night flooded the ­first reactor with sea water and boric acid to try to stop any more radiation ­leaking into the ­atmosphere. The blast followed efforts to lower heat and ­pressure around fuel rods after the quake ­disabled ­emergency cooling ­generators.

As temperatures in one ­reactor in the Fukushima plant approached 1000°C, ­radiation 1,000 times normal was ­detected in the control room. At one point the 40-year-old plant was releasing the amount of radiation a person normally absorbs in a year every hour, said the Japanese Nuclear ­Safety Panel. Caesium and iodine were detected – indicating damage to nuclear fuel rods.

The blast blew off the reactor roof and demolished walls. But casing round the nuclear fuel survived, preventing a full-scale leak, officials said. ­Government spokesman Yukio Edano said tests indicated radiation levels and pressure in the reactor had ­decreased after the blast. He said: “The reactor container was not damaged. The explosion didn’t occur inside it.

“There was no large radiation ­leakage outside. We’ve decided to fill the reactor container with sea ­water.”

In London, nuclear expert Malcolm Grimston said the flooding would prevent disaster.

He said: “The sea water will cause irreparable damage to the plant but they have obviously decided that it is an old facility. Early indications are that there should not be much lasting ­contamination.”

As a precaution the authorities doubled the exclusion zone around the plant from six miles to 12 ­yesterday and continued the massive evacuation. The wind was blowing radioactive material north, away from densely populated central Japan

Reiko Takaji, waiting at a local cab office, said: “Everyone wants to get away but the roads are terrible. It is too dangerous to go anywhere – but we are afraid the wind may change.”

A state of nuclear emergency ­remained in place yesterday at the Fukushima plant and its sister Daini installation. The plant is 150 miles north of Tokyo.

Japanese TV advised people in the radiation zone to cover their noses and mouths with wet towels, wash after going outdoors and to avoid fresh fruit, vegetables and tap water because of the risk. Japan’s nuclear safety agency declared that the ­accident rated a four on the seven-point ­International ­Nuclear and ­Radiological Event Scale.

John Large of the British Nuclear Engineering society, who has visited the stricken plant, said he feared the ­accident could be much worse than admitted.

He warned: “No one will die instantly but we may see an increase in cancers in the ­surrounding towns in the months and years ahead.”