wt 184 RADIOLOGICAL CLEANUP OF ENEWETAKATOLL radioactive) which ultimately becomes stable again through radioactive decay. The only induced radioactive isotope of significance remaining at the time of cleanup was cobalt-60 (Co-60). Normally, cobalt is found in small quantities in metals such as steel and iron; thus, the Co-60 on the islands was generally associated with the metallic debris. Co-60 decays by emission of energetic gamma rays accompaniedby beta particles. The biological effects of all types of ionizing radiation are similar, However, the probability that damage to the body may occur from radiation varies among the types of ionizing radiation because of the physical characteristics of each form. In addition, the degree of damage that may occur depends upon factors such as the amountoftissue exposed (whole-body versus partial-body), the quality and quantity of radiation received (dose), and the time over whichit is received (dose rate). Alphaparticles are relatively large and heavy and thus have a very short range over which they can travel—about 3 cm in air, and fractions of a millimeter in tissue. Thus, they ordinarily do not constitute an external hazard to people because normal clothing and thé outer layers of skin prevent the irradiation of any vital internal tissues. However, if alphaemitting material is deposited within the body in vital tissues (through inhalation, ingestion, or entry into an open wound), the ensuing alpha radiation can cause considerable localized cellular damage (within the organ where located) becauseall the energy is dissipated over a very short distance. For this reason, alpha-emitting materials such as the transuranic elements are classed as internal hazards. Beta particles are much smaller than alpha particles. They also can travel over a greater range—tens of centimeters in air and a few millimeters in © tissue. Because of this, beta particles can be a moderate external hazard in that the outer layer of skin can be penetrated and living tissues can be exposed, resulting in ‘‘beta burns.’’ The burn produced is similar to the burn caused by thermal energy (sun, fire) or chemicals, but it is not accompanied by immediate pain. When deposited internally, beta-emitting materials can also cause damageto the tissue in which they are located. This damageis less localized than that caused by alpha particles because of the greater range over which the energyis dissipated. Gammaradiation, since it is a wave form with no mass, has great range andis able to penetrate to all tissues of the body. It thus constitutes both an external and internal hazard for the whole body. This is in contrast to alpha andbeta particles, which are primarily partial-body or specific organ hazards. The characterization and extent of the potential problems at Enewetak were well defined, both because of the extensive knowledge and detailed records of the test period and because of the surveys done to characterize ra, the radiological environment. Based upon this understanding of the asd aA: CNRMT Rims 4 byt 8