Live: Japan disaster rating raised to equal Chernobyl

Japan raised the severity of its nuclear disaster to the highest level
on Tuesday, putting it on a par with the world's worst disaster
nuclear accident at Chernobyl after another major aftershock rattled
the quake-ravaged east. Refresh this page for live updates

12:30: pm: Kyodo News reports that a quake, pegged at magnitude 6.3,
rocked the Fukushima and Ibaraki prefectures in northeastern and
eastern Japan early this afternoon local time. The quake came in the
sake of another, magnitude 6.4, that rocked Chiba Prefecture, east of
Tokyo, and one of magnitude 5.6 quake that rocked Nagano Prefecture in
central, earlier this morning, local time.

12:15 pm: So what does it mean, to say that Japan has upgraded the
severity of its nuclear crisis to a seven, on par with Chernobyl? The
Sydney Morning Herald speaks to Prof Stephen Lincoln to find answers.
The relevant quote:

Chemistry and physics professor Stephen Lincoln, of Adelaide
University, said the main worry was the food stock in the ocean, where
much of the radioactive material was being released.
While one of the radioactive substances, iodine-131, had a half-life
of nine days, two others - caesium-137 and strontium-90 - could be
more harmful in the long term as they had half-lives of 30 years, he
said.
A half-life is the time taken for half of a sample of a radioactive
isotope to decay into other materials.
"[People] should not venture into the ocean [where the radioactive
materials are being released]; they should not eat any fish or seaweed
from the ocean.
"The living species likely to be most affected are shellfish because
they are stationary whereas fish that swim may pass through the area
and out again. The shellfish such as mussels, oysters and clams
certainly accumulate high levels of radioactivity.
"If they can stop the leaks, then the ocean can disperse the
radioactivity until it becomes no more than background."

11:45 am: Workers have been struggling to prevent a nuclear disaster
at Japan's Fukushima Daiichi nuclear plant. Here's a graphic
representation by the Wall Street Journal that explains the current
status of each of the six reactors.

11:30 am: Level 7 accidents on the International Nuclear Event Scale
correspond to the release into the external environment of radioactive
materials equal to more than tens of thousands of terabecquerels of
radioactive iodine 131. One terabecquerel equals 1 trillion
becquerels.

11:00 am: World's worst nuclear incidents
• Level 7: Chernobyl, Ukraine, 1986 - explosion and fire in
operational reactor, fallout over thousands of square kilometres,
possible 4,000 cancer cases
• Level 7: Fukushima, 2011 - tsunami and possibly earthquake damage
from seismic activity beyond plant design, leading to...?
• Level 6: Kyshtym, Russia, 1957 - explosion in waste tank leading to
hundreds of cancer cases, contamination over hundreds of square
kilometres
• Level 5: Windscale, UK, 1957 - fire in operating reactor, release of
contamination in local area, possible 240 cancer cases
• Level 5: Three Mile Island, US, 1979 - instrument fault leading to
large-scale meltdown, severe damage to reactor core

10:00 am: Although the Japanese incident now equates to Chernobyl on
the international scale, the two accidents are different in a number
of important ways. In Chernobyl it was the reactor core itself that
exploded, releasing a huge amount of radioactive material in a very
short space of time. Fukushima experienced a less critical hydrogen
explosion.
9:30 am: A month has elapsed since the emergency at Fukushima began.
But what exactly has gone on there and what are the priorities now?
BBC analyzes what needs to be done in Fukushima

9:00 am: It was the Cold War. Within days, the name 'Chernobyl' had
become a byword across the world for Soviet bungling -- and
callousness, since Moscow, obsessed by secrecy, did not come clean
about the disaster for nearly 36 hours. Postcard from Chernobyl:
vision of Apocalypse

8:30 am: A magnitude 6.3 earthquake occurred offshore near Chiba
prefecture in eastern Japan at 8.08 a.m. local time Tuesday, Xinhua
quoted Japan Meteorological Agency as stating.The epicentre of the
quake was located some 30 km under the sea of the eastern prefecture
in eastern Honshu, said the agency, however, adding the quake poses no
tsunami risk.
This film shows the terrifying images captured by the Russian
filmmaker Vladimir Shevchenko on scene at Chernobyl those dreadful
days in April 1986.
14,000 still missing one month after Japan's quake-tsunami

8:00 am: The rating of the accident at the Fukushima Daiichi nuclear
plant was raised to 7, the worst on an internationally recognised
scale, from a 5-rating. Japan said this reflects the initial severity
of the crisis and not the current situation.

"This is a preliminary assessment, and is subject to finalisation by
the International Atomic Energy Agency," said an official at the
Nuclear and Industrial Safety Agency (NISA), the government's nuclear
watchdog, which made the announcement with the Nuclear Safety
Commission.