However, rather than resort to the method used to seal Chernobyl in 1986, they still hope to end the crisis by fixing a power cable to two reactors by some time today in order to restart water pumps needed to cool overheating nuclear fuel rods at the Fukushima plant.
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Meanwhile, water continues to be dumped on No 3 reactor, the most critically damaged of the plant’s four.
It was the first time the facility’s operator acknowledged that burying the 40-year-old complex was a possibility, and a sign that dumping water from military helicopters and attempts to restart cooling pumps may not work.
"It is not impossible to encase the reactors in concrete," said an official from plant operator, Tokyo Electric Power Company. "But our priority right now is to try and cool them down first."
Officials raised the severity rating of Japan’s nuclear crisis from level four to level five, putting it on a par with the US’s Three Mile Island accident in 1979, although some experts say it is more serious.
The Soviet Union’s Chernobyl disaster reached a maximum seven on the INES scale.
Tourists, expatriates and many Japanese people continue to leave Tokyo, fearing radioactive emissions from the Dai-ichi nuclear complex 150 miles to the north, despite reassurances from health officials and the UN’s atomic watchdog that radiation levels in the capital are not harmful.
Such reassurances offer little solace for around 300 nuclear plant technicians working shifts round the clock in the radioactive wreckage.
In a bid to minimise radiation exposure, they wear masks, goggles and protective suits with seams sealed off by duct tape.
"My eyes well with tears at the thought of the work they are doing," said Kazuya Aoki, an official at Japan’s Nuclear and Industrial Safety Agency. Even if they succeed in restoring power at the plant, the pumps may be too damaged to operate.
Japan is still reeling as it enters the second week since a 9.0-magnitude earthquake and 33-foot tsunami struck, flattening coastal cities and killing thousands in the north-east, and causing the world’s worst nuclear crisis since Chernobyl.
The first step for technicians at Dai-ichi is to restore power to pumps for reactors No 1 and No 2, and possibly No 4, by today, said Hidehiko Nishiyama, Japan’s nuclear safety agency spokesman. By tomorrow, the government expects to have connected power to pumps for reactor No 3, which uses mixed oxides containing uranium and toxic plutonium.
Asked about burying the reactors, Nishiyama said: "That solution is in the back of our minds, but we are focused on cooling the reactors down."
Burying the reactors would leave part of the country off-limits for decades.
"It’s just not that easy," said Murray Jennex, a San Diego State University professor, when asked about the "Chernobyl option".
He added: "But eventually, yes, you could build a concrete shield and be done with it."
Some 390,000 people, including many elderly, are homeless and battling near-freezing temperatures in makeshift shelters in north-east coastal areas.
Food, water, medicine and heating fuel are all in short supply.
The government signalled it could have moved faster in dealing with the multiple disasters.
"An unprecedented huge earthquake and huge tsunami hit Japan. As a result, things that had not been anticipated in terms of the general disaster response took place," said Chief Cabinet Secretary Yukio Edano.
The Japanese government said yesterday it was considering moving evacuees to parts of the country unaffected by the devastation.
Nearly 320,000 households in the north were without still electricity in near-freezing temperatures, and at least 1.6 million homes were without running water.
The government has advised everyone within 12 miles of Dai-ichi to evacuate, and advised those within 18 miles to stay indoors.
Evacuation of Britons from country gathers pace
THE process of evacuating Britons from Japan continued in earnest yesterday with buses and planes being used to ferry people to safety.
Some 24 British nationals left tsunami-flattened Sendai at 12pm local time on two coaches heading for Tokyo.
Last night, they were expected to leave the country by plane after the Foreign Office block-booked seats on commercial flights.
The move comes as Japanese authorities raised the severity level at the crippled Fukushima Dai-ichi plant from four to five on the seven-point scale for nuclear accidents.
A Cathay Pacific flight was set to leave the Japanese capital at around 9pm local time heading for Hong Kong with space for 200 Britons.
The Foreign Office said two other flights would be made available today -- a Hong Kong Airlines flight and an Orient Thai Airlines plane, both destined for Hong Kong.
Those directly affected by last week’s devastating earthquake and tsunami can fly free of charge.
But people who have not been directly affected will pay around £600 per seat.
English teacher Maddie Smith, from Suffolk, decided to leave Sendai.
The 23-year-old, from Burgh St Peter, near Beccles, who has been in Japan since December, said: "We are getting on an embassy bus that goes to Tokyo, then from there we are heading south of the country to keep away from the nuclear plant."
Meanwhile, the Queen is to make a personal donation to help Japan and New Zealand in the wake of the countries’ devastating earthquakes, Buckingham Palace said.
In Christchurch, on a tour of disaster-stricken areas in New Zealand and Australia on behalf of the Queen, Prince William urged the earthquake-stricken city to "be strong"
In a speech at a memorial service in the city, he told them they were an "inspiration to all people".