The area of severe destruction resulting from blast, 

 heat, and initial radiation will vary with the size of 

 the nuclear weapon, the height of the explosion, and 

 to some extent, with the terrain and atmospheric con- 

 ditions. The size of the weapon is measured in terms 

 of the amount of energy released, compared with the 

 energy released by TNT. For instance, a one-kiloton 

 nuclear bomb produces the same amount of energv' as 

 the explosion of 1,000 tons of TNT. A one-megaton 

 bomb has explosive power equivalent to 1,000,000 tons 

 of TNT. 



Earlier nuclear weapons were measured in kilotons, 

 but the power of weapons now goes to bombs of many 

 megatons. A five-megaton weapon exploded on the 

 ground would cause severe destruction to residential 

 buildings for a radius of 6 miles from the point of 

 detonation. Similar destruction from a 20-megaton 

 weapon would extend to a radius of nearly 10 miles. 

 The heat from a ten-megaton bomb exploded on the 

 ground might set fire to easily-ignitable materials within 

 a radius of 15 to 20 miles on a clear day. If the bomb 

 exploded several miles above the surface, the area of 

 fire damage would be somewhat greater. 



A five-megaton weapwn exploded on the ground 

 would leave a crater about half a mile across and 200 

 feet deep. As the fireball rises, it draws up the thou- 

 sands of tons of pulverized and some vaporized mat- 

 ter which has been contaminated by the radioactive 

 residue of the explosion. As this material reaches 

 the cold upper air, the vaporized portion condenses, 

 just as rain or snow, and starts falling back to earth 

 along with the dust-like material. It is called fallout. 



From the ground one cannot tell which way the fall- 

 out will be blown from the point of explosion. The 

 contaminated area will be determined by the high- 

 altitude winds which may be moving in a different 

 direction from ground-level winds. The heavier par- 

 ticles of fallout will reach the ground a few miles from 

 the explosion about half an hour after it occurs. Fall- 

 out will begin on an area 20 miles away in about an 

 hour, and 100 miles away probably in 4 to 6 hours. A 

 food plant's distance from the point of nuclear explo- 

 sion therefore determines to a great extent the amount 

 of time its employees have in which to take protective 

 action. 



The early fallout, which contains the major radia- 

 tion danger, descends in less than 24 hours. Less dan- 

 gerous lighter particles, called delayed fallout, will sift 

 down at a diminishing rate for years. Those who can 

 remain in adequately protected shelter areas until the 

 early, heavy fallout has lost its strength — at least for 

 a period of 2 days to 2 wrecks or longer — will survive. 



Fallout loses about 90 percent of its strength in the 

 first 2 days. 



Fallout particles emit several types of radiation, but 

 the most dangerous ones are gamma rays, like X-rays. 

 Gamma rays have greater penetration pwwer than other 

 types, and over-exj>osure to them can cause sickness 

 or death. 



Radiation exposure is measured in units called 

 roentgens. During the average lifetime, every human 

 being receives about 10 roentgens of nuclear radiation 

 from natural sources. Exposure to more than 300 

 roentgens over a period of a few days — a dose which 

 unprotected persons might receive after a nuclear 

 attack — would cause sickness in the form of nausea, 

 and fxjssibly death. Death would be certain if a per- 

 son were to receive an exposure of 1,000 roentgens over 

 a period of a few days. 



The purfKDse of fallout shelters is to provide shielding 

 against gamma radiation. Since the rays do have an 

 enormous penetration ability, the most practical way 

 to protect against them is to place a sufl5cient amount 

 of mass between the fallout and the people to be pro- 

 tected. This shielding may be furnished by any type 

 of material that places mass between the source of 

 radiation and the people, but the more dense the mate- 

 rial the better its protection. The Office of Civil De- 

 fense, Department of Defense, recommends planned 

 fallout shelters which furnish a protection factor of at 

 least 40. This means that a person in such a shelter 

 would be exposed at a maximum to crdy ^40^ of the 

 fallout intensity outside the shelter. Even without 

 planned fallout shelters, however, there are many ways 

 to improvise shelter, especially in industrial buildings. 



One principle should be kept in mind regarding pro- 

 tection against fallout: Any protection is better than 

 none. 



Raw and finished foods are especially susceptible to 

 radiation hazards during processing and storage. 

 X^Tiile they are not damaged by radioactive rays, as 

 human cells are, they may be rendered inedible — at 

 least temporarily — if the radioactive fallout particles 

 actually become mixed in with them. Food contain- 

 ing a high concentration of fallout particles should 

 not be eaten until the radioactivity has decreased to 

 tolerable limits. 



Food plant managers should start thinking about 

 fallout protection immediately, for their people and 

 their food and food products. Detailed information 

 on the types of protective measures they can take may 

 be obtained from local, State or Federal civil defense 

 officials, or from U.S. Department of Agriculture State 

 and County Defense Boards. 



4 



