'Suicide squad' struggles to cool reactors as radiation levels rise

 

Tokyo

Japan yesterday deployed army helicopters and police water cannon manned by what the media are calling "suicide squads" in a frantic attempt to cool overheating fuel rods and prevent meltdown at a nuclear power plant ravaged by an earthquake and tsunami one week ago.

Operations were hampered by dangerously high radioactivity around the Fukushima Daiichi complex, which forced the authorities to evacuate the heavily protected workers periodically throughout the day. The plant's operator, Tokyo Electric Power (Tepco), admitted last night that the tactics had so far failed to cut radiation levels, which were about 3,600 microseiverts per hour, nearly four times the exposure considered safe in a year.

Tepco has been sending a rotating team of about 180 workers into the plant to prevent more contamination leaking from its six reactors, after a series of explosions tore away the buildings housing them. The cores of at least three reactors are believed to have partially melted since diesel-fuelled cooling systems were knocked out by last Friday's earthquake and tsunami.

Fuel pods in reactors 3 and 4 are thought to be dangerously short of water, meaning they are overheating and leaking radioactivity. A team from the US Nuclear Regulatory Commission warned yesterday that the cooling pond for the most troubled reactor 4 is completely dry, exposing fuel rods inside to air and increasing the risk of overheating. Tepco has not ruled out the possibility of a nuclear fission chain reaction.

Throughout the day television showed army Chinook helicopters dumping tons of sea water onto the Fukushima plant, about 150 miles from Tokyo, to try and refill the damaged pond in reactor 3. But state broadcaster NHK said the plan had to be abandoned because the pilots were exposed to gamma rays from the crippled complex. Riot police were also deployed yesterday with water canons to spray through holes in the number 3 reactor building. The Sankei newspaper dubbed the police team "Kesshitai", meaning a "unit that expects to die". The UN said engineers had connected a power line to reactor 2. This would allow the restart of pumps to cool the reactor.

The crisis at the plant's six reactors forced the government last night to warn that a Tokyo-wide blackout could occur following a surge in energy demand caused by the use of heaters in unseasonably cold weather, which is already adding to the misery of hundreds of thousands of people left homeless by the twin disasters.

Growing concern about the status of the plant has also led to a series of stark warnings by embassies in the country. France advised its citizens to leave Tokyo. Britain, Ireland and many other countries have recommended its nationals reconsider travelling to Tokyo.

The US State Department has chartered planes to fly families of military and government personnel well away from the complex. Temple University's Japan campus announced yesterday that it is evacuating 200 students from the capital because of radiation fears.

Officials and experts have said that the levels of radiation detected in Tokyo are so far not harmful to human health, but thousands of foreigners have put their families on trains to the west or south of the country, or on planes to Asia, Europe or America. Many have quietly taken holidays from work.

The exodus of foreigners contrasts with the stoic resignation of millions of Japanese around them. Despite the supposed threat of nuclear Armageddon, black-suited salarymen can be seen going to work every day as usual. Housewives calmly queue for bread, water and petrol around the city.

The ongoing crisis has also forced two Japanese companies to halt plans to build new nuclear complexes. Tokyo Electric Power Co., operator of the stricken Fukushima complex, announced yesterday it had suspended the construction of a 1,380-megawatt complex – the country's largest – in Aomori Prefecture. Another huge plant in the same prefecture was shelved yesterday, three years into construction.

The desperate fight to prevent nuclear catastrophe in Fukushima has overshadowed the plight of nearly half a million people sheltering in refugee centres in the north-east of the country. Snow and freezing weather has hampered the delivery of relief to the worst affected areas. Fukushima's governor, Yuhei Sato, said that frustration at the lack of hot food, medicine and petrol had reached "boiling point".

Drained storage ponds present greatest danger

A chemical reaction that generates enough heat to melt the zirconium rods containing highly radioactive nuclear fuel is the biggest problem facing the stricken Fukushima nuclear plant, a British nuclear expert said yesterday.

It is likely that the water in one or more of the swimming-pool sized storage ponds used to keep nuclear fuel safe when it is stored outside the reactors has leaked to dangerously low levels, exposing the zirconium cladding of the fuel rods to steam and air, said Professor Andrew Sherry. This causes rapid oxidation and the generation of heat which can raise temperatures to 800C – high enough to start a fire or cause an explosion. This would send radioactive material directly into the air as the containment buildings have lost their roofs, said Professor Sherry.

"I think the storage ponds is the most serious issue, and the reason for that is that we have the possibility of radioactive release straight up, because there is no roof on the buildings," said Professor Sherry, director of the Dalton Nuclear Institute at Manchester University. "As the water level drops down and the zirconium oxidises, it oxidises more rapidly as the temperature goes up and it is exposed to steam. That reaction generates heat."

"The explosion in Reactor 3 seems to have damaged the two fuel storage ponds at the top of Reactor 3 and Reactor 4. We think this has probably meant that water has started to drain away," he added.

The storage pond in the building housing Reactor 4 may have drained totally, setting off a reaction that would raise temperatures to a point where a fire is almost inevitable, said Professor Sherry.

Steve Connor

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