close attention to the hairy parts of your body,body creases, and fingernails, where dirt tends togather.NUCLEAR RADIATIONNuclear radiation presents a threat to ournaval forces. The effects of this threat can becontrolled if the basic facts of nuclear radiationare understood. The following paragraphsdescribe the phenomena of initial radiation,radioactive fallout, and types of radiation emittedby contamination.Initial RadiationInitial nuclear radiation consists of gammarays and neutrons and is emitted at the time ofa nuclear detonation. This radiation is emitted inthe first minute after burst; however, most of itis emitted in the first few seconds. This radiationcauses no damage to material, but it can be veryinjurious to ship’s personnel and produce manycasualties. The casualty range of initial radiationof a normal kiloton burst is over 1 mile. Initialradiation can readily penetrate the surface layersof targets. However, dense material, such as steel,can appreciably reduce radiation.Radioactive FalloutRadioactive fallout is a delayed phenomenonof a nuclear detonation. Most of the falloutoccurs minutes to hours after the burst. Surfaceand subsurface (underwater and underground)nuclear bursts deposit large amounts of falloutin localized areas. An airbursr in which the fireballdoes not contact the surface usually does not resultin fallout of military significance. This is becausethere is less radioactive material, and it is dispersedover a great area before reaching the surface.Within a few seconds after the burst, theradioactive products primarily are in the atomiccloud (fig. 7-6) along with a much larger amountof nonradioactive material, such as seawater orsurface material. Radioactive elements mixedwith nonradioactive material form the totalcontaminant produced by the burst. This radio-active mixture falls back to the earth’s surface asradioactive fallout.Heavier particles in the cloud fall out aroundsurface zero soon after the burst. The prevailingwinds carry finer and lighter particles over a largearea many miles from surface zero. A megatonburst carries significant amounts of fallout severalhundred miles and disperses it over thousands ofsquare miles. The time when fallout reaches agiven location may be from a fraction of a minuteto as much as 24 hours.Types of RadiationEmitted by ContaminationRadioactive contamination can emit threetypes of ionizing nuclear radiation: alpha, beta,and gamma. A single particle of contaminant maybe the source of one or more of these types. Theseradiations are not detectable by the human senses;however, electronic instruments (radiacs) candetect the presence of radiation, differentiateamong the three types, and measure theirrespective amounts and intensities. The followingparagraphs discuss the three types of radiation.ALPHA. —You can stop alpha radiation byalmost any barrier, including 1 to 2 inches of air.7-23Figure 7-6.—Relative sizes and altitudes of radioactive fallout clouds.
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