Japan nuclear crisis deepens as radiation keeps crews at bay | World news | The Guardian

Japan nuclear crisis deepens as radiation keeps crews at bay | World news | The Guardian

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Japan earthquake and tsunami

Japan nuclear crisis deepens as radiation keeps crews at bay

Race is on to restart cooling systems with emergency power after dropping water on damaged reactors has little effect

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Ian Sample, science correspondent
guardian.co.uk, Thursday 17 March 2011 19.20 GMT
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Handout shows steam rising from the No. 3 reactor at the Fukushima Daiichi nuclear power complex An aerial view taken from a Japanese military helicopter shows part of the nuclear crisis scene: the ruined reactor 3 building at the Fukushima Daiichi power plant. Photograph: Reuters

Helicopter crews and teams of police officers in water cannon trucks are battling intense radiation at the crippled Fukushima power station in Japan in a desperate bid to douse overheating fuel rods with tonnes of water.

Authorities have drafted in extra workers and turned to ever more radical tactics as fears grow that pools used to cool down spent fuel rods have leaked, leaving the rods exposed and in danger of catching fire, which could release huge amounts of radiation into the air.

Tepco, the company that operates the plant, has increased its workforce at the power station from 180 to 322 and replaced those who have reached – or in some cases surpassed – the maximum allowed dose of radiation.

The emergency workers focused their efforts on the storage pool at reactor 3, the only unit at the site that runs on mixed oxide fuel, which contains reclaimed plutonium. The strategy appeared to conflict with comments made by US nuclear officials and Sir John Beddington, the UK government's chief science adviser, who are most concerned about the storage pool at reactor 4, which they say is now completely empty.

"The water is pretty much gone," Beddington said, adding that storage pools at reactors 5 and 6 were leaking. "We are extremely worried about that. The reason we are worried is that there is a substantial volume of material there and this, once it's open to the air and starting to heat up, can start to emit significant amounts of radiation."

The storage pools are supposed to be kept below 25C to keep the spent fuel rods from heating up, but temperature readings at the ponds in reactor buildings 4, 5 and 6 show temperatures have been rising this week, to around 60C in pools 5 and 6 and at least 84C at reactor 4.

The government has urged British citizens to move at least 50 miles from the Fukushima 1 plant, in line with an exclusion zone declared by the US Nuclear Regulatory Commission. Britain's Met Office said it had begun sophisticated modelling of the radiation plume and was passing that information to the Cobra emergency committee but not making it public. The Japanese authorities maintained that their 20km exclusion zone was sufficient, with those within 30km advised to seal their homes and stay indoors.

The concern with reactor 3 appears to stem from an explosion on Monday that is thought to have damaged the primary containment facility around the reactor's core. If the storage pool at the reactor runs dry, radiation levels could soar so high that engineers cannot approach the reactor to try and bring it under control. David Lochbaum, a nuclear physicist for the Union of Concerned Scientists and a former Nuclear Regulatory Commission safety instructor, said the level of radiation beside the exposed rods would deliver a fatal dose in 16 seconds.

The frantic attempts to refill the leaking storage pool came as engineers installed a kilometre-long power cable to replace those destroyed in last Friday's earthquake and reconnect the power plant to the grid. Engineers said the power supply would first provide electricity to reactor 2. Japan's Nuclear and Industrial Safety Agency (Nisa) said three of the plant's six reactors – numbers 1, 5 and 6 – were relatively stable.

The fresh power supply will be used to drive pumps that are needed at three of the reactors to circulate seawater and prevent their nuclear cores from going into meltdown. The water levels in all three reactors are dangerously low, exposing between 1.4m and 2.3m of the fuel rods, according to Nisa. The fuel rods should be covered with water at all times to prevent meltdown.

The UN nuclear watchdog said engineers were able to lay an external grid power cable to reactor 2 and would reconnect it "once the spraying of water on the unit 3 reactor building is completed". It said water cannons had temporarily stopped spraying reactor 2 at 1109 GMT.

Five teams of police officers in water cannon trucks have tried to get close enough to reactor 3 to douse the storage ponds but were forced back after an hour when radiation rose to a dangerous level.

Minutes later military helicopters flew overhead and dropped 30 tonnes of water, but from such a height much of it appeared to miss the target. The storage pools are located in the top level of the reactor buildings and are exposed at reactors 1 and 3 because hydrogen explosions have torn their roofs off. Hidehiko Nishiyama, deputy director general of Nisa, said it was unclear whether the strategy had succeeded in topping up the ponds.
Japanese helicopters drop water on nuclear reactor
Link to this video

Nishiyama added that radiation levels of 250 millisievert an hour had been detected 30 metres above the plant. On Tuesday Japan's health ministry raised the cumulative maximum level for nuclear workers from 100 millisievert to 250 millisievert. The US said it was using U-2 spy planes and a Global Hawk drone and using infrared cameras to assess the temperatures of reactors and storage pools.

"One of the problems with the ponds is that the water, as well as providing cooling, also provides shielding so workers can come up to the edge of the pool and see what state the fuel is in," said Richard Wakeford, an expert in epidemiology and radiation at the Dalton nuclear institute of Manchester University. "If the water goes you've got no shielding and it's like having a great gamma-ray searchlight shining into the sky and that is presumably what the helicopters are seeing. That makes life extremely difficult for those trying to deal with this.

"Even though they are in Chinooks they haven't got much in the way of shielding. They would need lead on the bottom to protect people who are operating it."

The intense gamma rays released by the exposed fuel rods are likely to hamper efforts to cool the storage pools by air, but the radiation is a problem for workers on the ground too because it reflects off the atmosphere and causes "skyshine", which can irradiate large areas of land.

More than 20 Tepco workers, subcontractors, police and firefighters have been reported to the International Atomic Energy Agency as having radiation contamination, according to Yukio Edano, the government's chief spokesman. Seventeen people had radioactive material on their faces but were not taken to hospital because the level was low. Two policemen were decontaminated after being exposed and one worker was taken offsite after receiving a dose of radiation while venting radioactive steam from one of the reactors. An undisclosed number of firefighters are said to be under observation after being exposed. At least 25 Tepco workers and subcontractors are being treated for injuries sustained in explosions at the plant and other accidents.

There are fears the site might soon become too radioactive for engineers to work there. "You can arrive at the stage where unless you want to receive a very serious dose of radiation, you are in such an intense field that by the time you've run to wherever you need to do the work, you have to run back again. And they may very well be getting to that stage," said Wakeford. At that point any hope of cooling the reactors or the storage pools would rest on being able to bring heavy lead shielding into the area or cooling the plant from the air.

Vincent de Rivaz, the chief executive of EDF in Britain, said the energy company was making arrangements to ship 100 tonnes of boric acid to Japan. The chemical helps slow down nuclear reactions by absorbing neutrons.

On Wednesday people in towns and villages yet to evacuate the 20km exclusion zone around the plant were advised to take potassium iodide pills as a precaution against thyroid cancer, which is caused by radioactive iodine.