Japan must cool and isolate the nuclear fuel at its crippled atomic power station before trying to encase the reactors in a Chernobyl-style concrete sarcophagus, nuclear experts believe.
Japanese authorities agree it is still too early to talk about long-term measures and cooling the six reactors and associated fuel-storage pools at the Fukushima Daiichi nuclear power complex comes first.
One of Japan's six tsunami-crippled nuclear reactors appeared to stabilise on Saturday but the country suffered another blow after discovering traces of radiation in food and water from near the stricken power plant.
Soviet authorities ordered a vast concrete shelter built over the wrecked No. 4 reactor at Chernobyl in a desperate attempt to stem the contamination of Europe.
“Sarcophagus? Isn't it a little early,” said Hans Blix, a former weapons inspector who was head of the United Nations nuclear watchdog at the time of the 1986 Chernobyl disaster.
“For the moment, all the attention will be directed to reducing the radiation. The whole world is watching and listening,” Blix told Reuters by telephone from Stockholm.
In 1986, 90,000 workers and soldiers braved perilous radiation levels at Chernobyl to build a massive sarcophagus that is now riddled with cracks and holes.
“I don't think this is the priority right now,” said Alexander Nikitin, a former Russian military nuclear safety inspector who became an environmentalist campaigning for better nuclear safety.
“The problem now is how to cool those spent fuel pools, but you don't need to do that with sand, but by cycling in cold water,” he told Reuters.
SARCOPHAGUS
The Chernobyl sarcophagus, built in just over six months on the orders of panicked Soviet authorities who had remained silent for days before even acknowledging the accident, was not designed to last more than 20 to 30 years.
Its roof was supported on one side by the wall of the old reactor building and the structure had to be reinforced in 2008.
“Holes and fissures in the structure now cover 100 square metres, some of which are large enough to drive a car through”, according to Chernobyl Children International, a UN-sponsored charity organisation.
Japan has raised the severity rating of its nuclear crisis from Level 4 to Level 5 on the seven-level International Nuclear Event Scale, putting it on a par with the Three Mile Island accident in the United States in 1979.
The Chernobyl disaster was ranked at 7 on that scale while the 1957 Kyshtym disaster at the Mayak nuclear fuel plant in Soviet Russia was ranked at 6 on the scale.
“There is already a feeling that they do not have a clearly-defined plan,” said Nikitin. “They are only reacting what is happening, but there is no clear plan how to put out the fires and stop everything.”
“The situation is being watched rather than controlled right now,”he said by telephone from Norway.
Vast swathes of European territory was contaminated by Chernobyl and hundreds of tons of nuclear material remains encased in the concrete sarcophagus, the centre of an exclusion zone with a radius of 30 km around the plant.
A new 29,000 tonne convex steel structure — called the New Safe Confinement — is being financed by the Chernobyl Shelter Fund.
The $1.4 bln structure, tall enough to house the Statue of Liberty, will completely cover the old sarcophagus and will allow the reactor to be eventually dismantled. It is designed to last for a century.
