Residents queue to be tested, but experts say this is not Chernobyl

Japan was battling a mounting nuclear crisis yesterday as officials desperately tried to ensure that fuel rods in damaged reactors did not overheat, risking an explosion that could release more radioactive material into the air.

Some officials fear that the fuel rods could melt the containers that house the reactor cores. By last night there were concerns over four separate nuclear plants, one of them just 75 miles from Tokyo.

At the Fukushima No 1 power plant, where the roof of one building was blown off by a blast last week, workers were last night pumping sea water into a third reactor to release a buildup of pressure. Officials were also monitoring the Fukushima No 2 plant nearby.

Meanwhile a spokesman for Japan Atomic Power Company said the cooling system at the Tokai nuclear power plant near Tokyo had failed, although other systems were ensuring that the temperature of the reactor was still falling.

In another dispiriting sign, authorities in Tokyo told the UN nuclear watchdog that the lowest state of emergency has been reported by the operator at the Onagawa nuclear power plant. The International Atomic Energy Agency (IAEA) said in a statement: "The alert was declared as a consequence of radioactivity readings exceeding allowed levels in the area surrounding the plant. Japanese authorities are investigating the source of radiation." Prime Minister Naoto Kan was at pains to emphasise that "this is fundamentally different from the Chernobyl accident".

As workers race to control the potential overheating, anywhere between 170,000 and 200,000 people living close to a number of damaged reactors north of Tokyo have already been evacuated. Some were taken to Koriyama, where crews from the local fire brigade, dressed in white "haz-mat" suits, were carrying out radiation testing at an emergency centre set up outside a gymnasium.

Across this part of the country, hundreds of emergency shelters have been set up for those who have nowhere else to go. Hundreds of thousands of people have been left without water, electricity or proper food. While the government doubled the number of soldiers deployed in the aid effort to 100,000 and sent 120,000 blankets, 120,000 bottles of water and 29,000 gallons of petrol, the prime minister said it would take days to restore electricity supplies. In the meantime, it is to be rationed with rolling blackouts in several cities, including Tokyo.

At the Sogu Gym in Koriyama, men and women, the elderly and babies carried by their parents were led one by one towards the crews clad in white suits and masks. Everyone wanted to know just two things: had they been exposed to radiation, and if so by how much?

The answers were delivered after a measurement was taken using a Geiger counter, and if a reading was found above the safe limits – measured in microsieverts – the person was put under a shower of hot water and soap and then taken to a nearby hospital for further checks. Periodically, ambulances sped off into the streets of the quiet, empty city.

Reports said the Japanese Nuclear and Industrial Safety Agency had confirmed that 160 people living close to the Fukushima Daiichi plant may have been exposed while local media said three plant workers had showed signs of radiation sickness.

"I am worried about the radiation. My house is around 20km from one of the plants," said Tomoko Karaki, a 29-year-old English teacher from Minamisoma, as she waited her turn to be tested. Like everyone in the queue, Ms Karaki may have been concerned and inwardly frightened but she refused to display any outward sign of panic. "My mother, father and brother are all worried," she added. "The government told us to leave the town. We trust the government but some of the information has been slow to come."

Among those waiting to be checked was Kensuke Kano, a teacher at a secondary school in the coastal city of Soma, also close to one of the damaged reactors. "The earthquake caused a lot of damage. I helped people when they created an evacuation centre but I could not find some of my students. Some are still missing," he said. "Now the radiation is the big worry. We are very scared about the possible radiation."

The nuclear accident, the worst since Chernobyl in 1986, has triggered criticism that authorities were ill-prepared to tackle the threat caused by such a massive quake. Chief Cabinet Secretary Yukio Edano said there might have been a partial meltdown of the fuel rods at the No 1 reactor at Fukushima. Engineers were pumping in sea water, trying to prevent the same happening at the No 3 reactor – a tacit acknowledgement that they had moved too slowly on Saturday. "Unlike the No 1 reactor, we ventilated and injected water at an early stage," he said in Tokyo.

In Koriyama, one of the fire brigade members at the radiation testing centre said up to 1,500 people had come to be checked. The man, who declined to be named, said 200 or 300 of the people had been subsequently sent to a local hospital, although that figure could not be immediately confirmed. "If we get a reading [above the safe limit] we are showering people down. We then wait for the reading to drop and then we send them to the hospital," he said. Asked how bad he believed the situation was, he replied: "It is as the government says. This is not Chernobyl."

That, of course, is the great fear. But last night, the opinion of experts appeared to be that – despite the advice given to French citizens to leave even Tokyo – the crisis, although serious, would likely not become a catastrophe.

Robin Grimes, the director of the Centre for Nuclear Engineering at London's Imperial College, told Reuters: "There's no risk of an extensive radiation leak into the surrounding areas. The worst-case scenario is it's just going to be more difficult to clean up. What's clear because of the incidental radiation being released at the moment, which is significant but not overwhelming, is that the structure of the core is probably still intact. So it's not as bad as Three Mile Island", a reference to the partial meltdown of a reactor core in Pennsylvania in 1979.