Help kill the ignorance, common Nuke terms expalined

it seems to me that a lot of terms being used about the disaster in Japan are being misused by folks that do not understand what they are saying, so here are a few terms explained...
please feel free to add to the list and post refrence to back up your definition.

Half-life:::

is the period of time it takes for a substance undergoing decay to decrease by half. (ie the radiation of the substance is decreased by 50%)
Plutonium-239's half-life is 24,110yrs for example, its radiation levels will decrease by 1/2 in 24,110 years. and still be unsafe... Plutonium-239 would have to go through 8 half-lives to eliminate all radiation from that particular source... that's 192,880years.

Fallout:::

Fallout is the residual radiation hazard from a nuclear explosion, so called because it "falls out" of the atmosphere after the explosion.
Fallout, worldwide:::
After an air burst, fission products, un-fissioned nuclear material, and weapon residues vaporized by the heat of the fireball condense into a fine suspension of small particles 10 nm to 20 µm in diameter. These particles may be quickly drawn up into the stratosphere, particularly if the explosive yield exceeds 10 kt.
Atmospheric nuclear weapon tests almost doubled the concentration of radioactive 14C in the Northern Hemisphere, before levels slowly declined following the Partial Test Ban Treaty.

Initially little was known about the dispersion of nuclear fallout on a global scale. The AEC assumed that fallout would be dispersed evenly across the globe by atmospheric winds and gradually settle to the Earth's surface after weeks, months, and even years as worldwide fallout. Nuclear products were deposited in the Northern Hemisphere becoming "far more dangerous than they had originally been estimated[citation needed]."

The radio-biological hazard of worldwide fallout is essentially a long-term one because of the potential accumulation of long-lived radioisotopes (such as strontium-90 and cesium-137) in the body as a result of ingestion of foods containing the radioactive materials. This hazard is less pertinent than local fallout, which is of much greater immediate operational concern.

Fallout can also refer to nuclear accidents, although a nuclear reactor does not explode like a nuclear weapon. The isotopic signature of bomb fallout is very different from the fallout from a serious power reactor accident (such as Chernobyl). The key differences are in volatility and half-life.

all definitions referenced from en.wikipedia.org...

Corium Wiki

Corium, also called fuel containing material (FCM) or lava-like fuel containing material (LFCM), is a lava-like molten mixture of portions of nuclear reactor core, formed during a nuclear meltdown, the most severe class of a nuclear reactor accident.

Notice how it's referred to as "lava-like"?

And what is inside this "Corium"?

It consists of nuclear fuel, control rods, structural materials from the affected parts of the reactor, products of their chemical reaction with air, water and steam, and, in case the reactor vessel is breached, molten concrete from the floor of the reactor room.

Please review the link for further information.

Potassium iodide:::

is an inorganic compound with formula KI
In 1982, the US FDA approved potassium iodide to protect thyroid glands from radioactive iodine involving accidents or fission emergencies. In an accidental event or attack on a nuclear power plant, or in nuclear bomb fallout, volatile fission product radionuclides may be released. Of these products, 131I is one of the most common and is particularly dangerous to the thyroid gland because it may lead to thyroid cancer. By saturating the body with a source of stable iodide prior to exposure, inhaled or ingested 131I tends to be excreted, which prevents radioiodine uptake by the thyroid. The protective effect of KI lasts approximately 24 hours. For optimal prophylaxis, KI must be dosed daily until a risk of significant exposure to radioiodine by either inhalation or ingestion no longer exists. Emergency 130 milligrams iodide doses are roughly 700 times larger than the normal nutritional need for iodine, which is 150 micrograms (0.15 mg) per day for an adult.

en.wikipedia.org...