The Effects of Nuclear War

Fallout Shelters

In the United States, fallout shelters have been identified predominantly in urban areas (by the Defense Civil Preparedness Agency (DCPA) shelter survey), to protect against fallout from distant explosions, e.g., a Soviet attack on U.S. intercontinental ballistic missiles (ICBMs). On the other hand, Soviet fallout shelters are primarily intended for the rural population and an evacuated urban population.

Fallout protection is relatively easy to achieve. Any shielding material reduces the radiation intensity. Different materials reduce the intensity by differing amounts. For example, the thickness (in inches) of various substances needed to reduce gamma radiation by a factor of 10 is: steel, 3.7; concrete, 12; earth, 18; water, 26; wood, 50. Consider an average home basement that provides a protection factor (PF) of 10 (reduces the inside level of radiation to one-tenth of that outside). Without additional protection, a family sheltered here could still be exposed to dangerous levels of radiation over time. For example, after 7 days an accumulated dose of almost 400 rems inside the basement would occur if the radiation outside totaled 4,000 roentgens. This could be attenuated to a relatively safe accumulation of 40 rems, if about 18 inches of dirt could be piled against windows and exposed walls before the fallout begins. Thirty-six inches of dirt would reduce the dose to a negligible level of 4 rems (400 100). Thus, as DCPA notes, “fallout protection is as cheap as dirt.” Moving dry, unfrozen earth to increase the protection in a fallout shelter requires considerable time and effort, if done by hand. A cubic foot of earth weighs about 100 lbs; a cubic yard about 2,700 lbs. Given time, adequate instructions, and the required materials, unskilled people can convert home basements into effective fallout shelters.

The overall effectiveness of fallout shelters, therefore, depends on: (a) having an adequate shelter—or enough time, information, and materials to build or improve an expedient shelter; (b) having sufficient food, water, and other supplies to enable shelterers to stay sheltered until the outside fallout decays to a safe level (they may need to remain in shelters for periods ranging from a few days to over 1 month, depending on fallout intensity); and (c) entering the shelter promptly before absorbing much radiation. (An individual caught by fallout before reaching shelter could have difficulty entering a shelter without contaminating it. )

Over the years, home fallout shelters have received considerable attention, with the Government distributing plans that could be used to make home basements better shelters. Such plans typically involve piling dirt against windows and (if possible) on floors above the shelter area, stocking provisions, obtaining radios and batteries, building makeshift toilets, and so forth. Such simple actions can substantially increase protection against radiation and may slightly improve protection against blast. However, few homes in the South and West have basements.

With adequate time, instructions, and materials, an “expedient” shelter offering reasonable radiation protection can be constructed. This is a buried or semi-buried structure, shielded from radiation by dirt and other common materials. Expedient shelter construction figures prominently in Soviet civil defense planning.

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