Detroit Example: Radiation & Fallout

Short Term Radioactive Fallout Pattern Overpressure and REM Table

Radioactive Fallout

Fallout from the stem starts building after about 10 minutes. This is the prime threat to rescue crews. The affected area would have a radius of about 6.5 miles with a hot spot a distance downwind that depends on the wind velocity. If there is a 15-mph wind from the southwest, an area of about 1 square mile-the solid ellipse shown-would cause an average exposure of 300 rems in the first hour. The larger toned ellipse shows an area of 150 rems in the first hour.

Because of the dirty nature of this blast, fallout will be an especially important effect to consider. This blast will likely deposit measurable, if not harmful, amounts of radioactive debris across much of the U.S., in the form of delayed fallout over the next several months. Even more important are the localized effects that the early fallout, defined as all the fallout occurring in the first 24 hours, will have on the survivors, rescue workers and those not directly affected by the blast but living in the vicinity of Detroit.

Surface blasts generally produce more early fallout since the average size of the fallout particles are larger and thus fall back to earth faster. Over 300 species of radioactive materials are produced in a blast. Each has its own half life and some interact in particular ways with the human body.

After the first 24 hours, when most of the early fallout has settled, the radiation level decreases roughly in proportion to elapsed time. Reducing exposure by leaving the area or remaining in a fallout shelter will greatly reduce the radiation effects on people

Significant levels of radiation (greater than 200 rads will cause radiation sickness) will extend out much farther than other effects such as blast overpressure. Radioactive contamination will hamper rescue, cleanup and recovery efforts as most of the city will have dangerously high levels of radiation for many weeks to come.

The radiation given off by fallout is dangerous because of the way it interacts with the body's cells. There are three basic types of radiation given off by radioactive fallout: gamma, beta and alpha. The gamma rays are high energy photons that penetrate deeply into tissue and cause damage by scattering off of, and knocking loose, electrons that are a part of the body's cells. The beta rays (electrons) only penetrate shallowly but can cause severe burns. The alpha rays (helium nuclei) are the most massive and do the most damage when they interact with the body's cells, ionizing elements they contact. Neutrons interact with the nuclei to lock out protons that then ionize other elements.

In addition to the direct effect that radiation has, some elements can be absorbed into the body causing greater internal damage to specific organs. Strontium 90 (created in the fission process) is similar in chemical composition to calcium and lodges in the bones, especially in children. Iodine 131 is absorbed by the thyroid gland and can result in cancer of the thyroid or hypothyroidism. Cesium 137 is taken into the body much like potassium and is distributed fairly evenly.

Fallout Effects

Dose-rem Effects
5-20 Possible late effects; possible chromosomal damage.
20-100 Temporary reduction in white blood cells.
100-200 Mild radiation sickness within a few hours: vomiting, diarrhea, fatigue; reduction in resistance to infection.
200-300 Serious radiation sickness effects as in 100-200 rem and hemorrhage; exposure is a Lethal Dose to 10-35% of the population after 30 days (LD 10-35/30).
300-400 Serious radiation sickness; also marrow and intestine destruction; LD 50-70/30.
400-1000 Acute illness, early death; LD 60-95/30.
1000-5000 Acute illness, early death in days; LD 100/10.
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