Following the “highly likely” meltdown of the uranium rods at the Fukushima Daiichi nuclear power plant—after a drop in liquid levels caused by a lack of fuel in the water pumping machines—the Japanese government has raised the nuclear alert level to 5: “Accident with wider consequences.”According to the International Nuclear and Radiological Event Scale, this means:
Impact on People and Environment
• Limited release of radioactive material likely to require implementation of some planned countermeasures.
• Several deaths from radiation.
Impact on Radiological Barriers and Control
• Severe damage to reactor core.
• Release of large quantities of radioactive material within an installation with a high probability of significant public exposure. This could arise from a major criticality accident or fire.
An example of this accident was the March 28, 1979 Three Mile Island in Harrisburg, PA, where design and operation errors lead to partial exposure of nuclear fuel rods and partial meltdown. As a result, radioactive gases were released to the atmosphere.
Gizmodo has also posted this graphic of the possible alert levels.
The increase in the alert level comes on the heels news that nuclear fueling rods at the plant have been exposed twice today.
As the BBC reports:
Meltdown alert at Japan reactor
Technicians are battling to stabilise a third reactor at a quake-stricken Japanese nuclear plant, which has been rocked by a second blast in three days.
Sea water is being pumped into reactor 2 at the Fukushima Daiichi plant, after its fuel rods were fully exposed twice.
International nuclear watchdogs said there was no sign of a meltdown, although a cabinet minister said it was “highly likely” to be happening.
The crisis was sparked by Friday’s 9.0-magnitude quake and tsunami.
Thousands of people are believed to have died, and millions are spending a fourth night without water, food, electricity or gas. More than 500,000 people have been left homeless.
‘Not optimistic’On Monday a hydrogen blast at the Fukushima Daiichi’s reactor 3 injured 11 people and destroyed the building surrounding it. The explosion was felt 40km (25 miles) away and sent a huge column of smoke into the air.
It followed a blast at reactor 1 on Saturday.
Chief Cabinet Secretary Yukio Edano said there were signs that the fuel rods were melting in all three reactors.
“Although we cannot directly check it, it’s highly likely happening,” he told reporters.
But shortly after Monday’s blast, Tepco warned it had lost the ability to cool Fukushima Daiichi’s reactor 2.
Officials have battled all day to try to keep water levels up in order to cool the nuclear fuel rods, but on two occasions the rods have been fully exposed.
Exposure for too long a period of time can damage the rods and raise the risk of a meltdown.
Four of the five pumps used to administer cooling seawater were believed to have been damaged by the blast at reactor 3.
But the French Nuclear Safety Authority (ASN) cast doubt on Japan’s classification of the crisis at Fukushima as level 4 of 7 on the International Nuclear Event Scale. Chernobyl was classified as level 7.
“Level four is a serious level,” ASN chief Andre-Claude Lacoste said, but added: “We feel that we are at least at level five or even at level six.”
The news of the expanded nuclear alter also follows earlier news that the radioactive cloud from the plant has been blown by the wind 100 miles north of the nuclear reactor explosion zone.
Experts are also discussing the possibility that winds could blow radioactive fallout onto the US west coast.
Fore more on the possible radiation fallout projections see: Possible Fukushima Nuclear Fallout Projections For the U.S. Based on Wind Patterns