The following is posted on the National Terror Alert Resource Center website:

Suitcase Nuclear Device
A "suitcase" bomb is a very compact and portable nuclear weapon and could have the dimensions of 60 x 40 x 20 centimeters or 24 x 16 x 8 inches. The smallest possible bomb-like object would be a single critical mass of plutonium (or U-233) at maximum density under normal conditions. The Pu-239 weighs 10.5 kg and is 10.1 cm across. It doesn't take much more than a single critical mass to cause significant explosions ranging from 10-20 tons. These types of weapons can also be as big as two footlockers. The warhead consists of a tube with two pieces of uranium, which, when rammed together, would cause a blast. Some sort of firing unit and a device that would need to be decoded to cause detonation may be included in the "suitcase."

Another portable weapon is a "backpack" bomb. The Soviet nuclear backpack system was made in the 1960s for use against NATO targets in time of war and consists of three "coffee can-sized" aluminum canisters in a bag. All three must be connected to make a single unit in order to explode. The detonator is about 6 inches long. It has a 3-to-5 kiloton yield, depending on the efficiency of the explosion. It's kept powered during storage by a battery line connected to the canisters.

Effects

External radiation — occurs when either part of or all of the body is exposed from an external source, such as when a person is standing near the site of where a radiological device is set off and he or she is exposed to radiation, which can be absorbed by the body or can pass completely through it.

Contamination — occurs when radioactive materials in the form of solids, liquids or gases are released into the air and contaminate people externally, internally or both. This happens when body parts such as the skin become contaminated and/or if the harmful material gets inside the body via the lungs, gut or wounds.

Incorporation of radioactive material — occurs when body cells, tissues and organs such as bone, liver, thyroid or kidney, are contaminated.

Gamma radiation can travel many meters in the air and many centimeters once in human tissue; therefore they represent a major external threat. Dense material is needed as a shield. Beta radiation can travel meters in air and can moderately penetrate human skin, but clothing and some protection can help. Alpha radiation travels a very short distance through the air and can't penetrate the skin, but can be harmful if inhaled, swallowed or absorbed through open wounds.

Radiation in the first hour after an explosion is about 90 percent, with it going down to about 1 percent of the original level after two days. Radiation only drops to trace levels after 300 hours.

Symptoms

People in the immediate vicinity would likely die from the force of the conventional explosion itself. Some survivors of the blast might die of radiation poisoning in the weeks afterward. Those farther away from the explosion might suffer radiation sickness in the days and weeks afterward, but recover. Over time, risks of cancer in the affected area would rise, but perhaps only slightly.

A mix of physical symptoms must be used to judge the seriousness of exposure. Impact of radiation poisoning also changes if the body has experienced burns or physical trauma. In the case of treatable victims, extensive medical treatment may be needed for more than two months after exposure.

Some symptoms may include vomiting, headache, fatigue, weakness, diarrhea, thermal burn-like skin effects, secondary infections, reoccurring bleeding and hair loss.

Treatment

If detection and decontamination occurs soon after exposure, about 95 percent of external radioactive material can be removed by taking off the victim's clothing and shoes and washing with water. Further decontamination may require the use of bleaches or other mild abrasives.

Treatment of a victim within the first six weeks to two months after exposure is vital and is determined by what types of radioactive isotopes to which the victim was exposed.

Medical personnel will treat victims for hemorrhage and shock. Open wounds are usually irrigated to cleanse them of any radioactive traces. Amputation of limbs may occur if a wound is highly contaminated and functional recovery isn't likely.

If radioactive material is ingested, treatment is given to reduce absorption and enhance excretion and elimination. It includes stomach pumping or giving the victim laxatives or aluminum antacids, among other things.

If radioactive material has gotten into a victim's internal organs and tissues, treatment includes giving the patient various blocking and diluting agents, such as potassium iodide, to decrease absorption. Mobilizing agents such as ammonium chloride, diuretics, expectorants and inhalants are given to a patient to force the tissues to release the harmful isotopes. Other treatments involve chelating agents. When ingested, these agents bind with some metals more strongly than others to form a stable complex that, when soluble, are more easily excreted through the kidneys.