* Astronomy

Blobrana · L

Fukushima Daiichi

Blobrana · L

RE: Fukushima No.1 nuclear plant

Blobrana · L

Greg Jaczko, chairman of the US Nuclear Regulatory Commission (NRC), said attempts to cool reactors with sea water and prevent them from melting down appeared to be failing.
Emergency workers in the vicinity could be exposed to "potentially lethal" radiation doses, he said.
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Blobrana · L

Information: Critical and supercritical mass

A critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction. The critical mass of a fissionable material depends upon its nuclear properties, its density, its shape, its enrichment, its purity, its temperature and its surroundings.
When a nuclear chain reaction in a mass of fissile material is self-sustaining, the mass is said to be in a critical state in which there is no increase or decrease in power, temperature or neutron population.

A supercritical mass is one where there is an increasing rate of fission.
Source

Blobrana · L

Public Health Risks from Japanese Radiation

Airborne radiation from a meltdown at Japanese nuclear plants poses no immediate risk to the continental United States, say University of Maryland public health and atmospheric scientists.
Drawing on research from the Chernobyl meltdown in 1986, they add that for most Japanese, the long term risk may lie in ingestion of milk, water or food, as well as direct exposure to contaminated soil.
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Blobrana · L

Nuclear crisis: 'Chain reaction could restart'

The situation at Japan's Fukushima Daiichi nuclear power plant has become extremely unnerving. The Tokyo Electric Power Company has now admitted that the spent fuel rods could go critical - that is, a nuclear chain reaction could restart.
We have known since yesterday that the reactors themselves were coming under control, and that the biggest threat came from the spent fuel ponds, where the water level has fallen and temperatures have risen. That could lead to the stored fuel rods breaking open, releasing their radioactive contents.
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Ed ~ The original BBC article has some perceptive insights on why this incident is still on going.

Blobrana · L

Fukushima incident is out of control

At this stage, there may be little that can be done to stop the chain of events slowly destroying the reactors. Peak radiation levels at the site are now solidly in the millisievert (mSv) per hour range - dangerous enough to require minimal crews and frequent shift changes for workers. Water coolant dumped from helicopters may be able to provide some aid, but today at least, radiation levels above the plant were too high for the aircraft to fly.
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Ed ~ Just a passing thought; but as time goes by, and the more information is revealed about this incident, the worse it seems to gets - strangely similar to the Chernobyl incident.

Blobrana · L

IAEA chief: Japan's nuclear situation is 'very serious'

The head of the International Atomic Energy Agency, Yukiya Amano, has said that the nuclear situation in Japan is "very serious".
Engineers are racing to avert a nuclear catastrophe at Fukushima Daiichi, badly damaged by Friday's quake and tsunami.
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Blobrana · L

Over the days of the Fukushima crisis, attention has switched from reactor 1 to reactor 3, to 2, back to 3 - and now, to 4.
This is a surprise.
Reactors 4, 5 and 6 were shut down at the time of Friday's earthquake, with some or all of their fuel rods extracted and left in cooling ponds that each reactor building has under its roof.
Once a reactor is turned off, radioactivity and heat generation in the rods die away quickly; down to 7% of the original power within a second of switch-off, 5% within a minute, 0.5% within a day.
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Blobrana · L

White vapour billows from earthquake-hit nuclear plant

Japanese workers have been evacuated from a nuclear plant that has been hit by several explosions following the earthquake and tsunami that hit Japan on Friday. White vapour has been seen billowing from the plant.
Officials have also warned people within 20-30km of the site to either leave the area or stay indoors.
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