Radiation fallout

These coefficients must be multiplied by the density of air and tissue, respectively. Figure 15.7.2-1 depicts a radiation fallout field. Let C be the curie activity/m. The radiation into a unit area receptor at z = 1 m above the ground. The area is emitting C r dr d0 gammas/s. These are attenuated in the air as exp(-p, R) and geometrically as l/(4 7t R). The radiation received by the receptor is given by equation 15.7.2-1 which becomes 15.7.2-2 by a change of... 

If the initial distribution of radioactive debris is known spatially, Equations 1 and 2 suffice to define the partition of radioactive debris between local and long range fallout, the decay rate of radioactive debris in a given size interval, and other properties of the radiation fallout field. 

These scientists position on the topic of chemical mutagens framed a distinctly minority opinion within the postwar genetics community. Despite Muller s and Lederberg s authority as Nobel laureates and the tendency of both to use their awards as bully pulpits, early attempts to raise public and scientific awareness must have been too distant from the practical and theoretical interests of mainstream genetics to elicit much response, vocal or otherwise.4 Viewed within the context of the radiation fallout controversy, these were modest and sporadic efforts by concerned individuals and not, as would later become the case, collective organizational responses. 

Disinterestedness has been a common theme for geneticists, for example, in their movements to oppose Lysenko, radiation fallout, and even racism. 

Problem 10.56. One of the products of radiation fallout from atmospheric bomb testing or nuclear accidents as at Chernobyl is iodine-131. People living in a region where iodine-131 was known to have been deposited were encouraged to use salt enriched with nonradioactive iodine-127. What was the basis of this treatment ... 

Radiation Therapeutic Radioiodine Atomic fallout infections Rubella virus Cytomegalovirus Herpes virus homlnis Toxoplasmosis... 

The radiation hazard associated with fallout from nuclear weapons testing arises from radioactive isotopes such as these. One of the most dangerous is strontium-90. In the form of strontium carbonate, SrC03, it is incorporated into the bones of animals and human beings, where it remains far a lifetime. 

Half-lives span a very wide range (Table 17.5). Consider strontium-90, for which the half-life is 28 a. This nuclide is present in nuclear fallout, the fine dust that settles from clouds of airborne particles after the explosion of a nuclear bomb, and may also be present in the accidental release of radioactive materials into the air. Because it is chemically very similar to calcium, strontium may accompany that element through the environment and become incorporated into bones once there, it continues to emit radiation for many years. About 10 half-lives (for strontium-90, 280 a) must pass before the activity of a sample has fallen to 1/1000 of its initial value. Iodine-131, which was released in the accidental fire at the Chernobyl nuclear power plant, has a half-life of only 8.05 d, but it accumulates in the thyroid gland. Several cases of thyroid cancer have been linked to iodine-131 exposure from the accident. Plutonium-239 has a half-life of 24 ka (24000 years). Consequently, very long term storage facilities are required for plutonium waste, and land contaminated with plutonium cannot be inhabited again for thousands of years without expensive remediation efforts. 

Variations in radiation doses to individuals within exposed populations also occur. Based upon previous exposures of people to Pu and Sr in fallout and exposures of laboratory animals to Ce, the dispersion of individual doses in a population is expected to be significant and should be considered in the formulation of population exposure guidelines. 

Concentratons of Sr in people living in New York City between 1953 and 1959 who were exposed to nuclear weapons fallout were reported by Kulp and Schulert (1962). They suggested that the distribution of observed values was well fit by a log-normal distribution that had a geometric standard deviation of about 1.7. The Federal Radiation Council (FRC, 1961), after review of the accumulated data on Sr in human bone, concluded that a log-normal distribution was the appropriate description of the distribution of this age-controlled, exposuretime controlled population. The main exposure to Sr from fallout was by way of ingestion. 

Larson, K. H., Neel, J, W., Hawthorne, H. A., Mork, H. M., Rowland, R. H., Baurmash, L., Lindberg, R. G., Olafson, J. H. and Kowalewsky, B. W. (1966). Distribution, Characteristics and Biotic Availability of Fallout, Operation Plumbbob, Report No. WT-1488 (Laboratory of Nuclear Medicine and Radiation Biology, University of California, Los Angeles, also National Technical Information Service, Springfield, Virginia). 

The final column presents the radius of 50% mortality from fallout 1 hour after the explosion. Of all of the threats described, fallout is the hardest to predict because of the influence of local, regional, or even global weather patterns. The mushroom cloud can rise into the atmosphere as far as 80,000 feet, where wind and rain influence the time and location for fallout to occur.2 Individuals several miles from ground zero and well outside any radius presented in Table 5.1 can receive significant or even lethal radiation doses from fallout. However, while the air blast, thermal burns, and initial radiation are threats in all directions, fallout is a threat downwind from ground zero. Wind speed and direction vary at different altitudes, and it is safest to assume that fallout is a potential threat in all directions from ground zero. Individuals outside the blast zone generally will have several minutes to an hour or more to seek shelter before fallout arrives. 

Radiation levels from fallout decrease with time in a relationship described by the 7/10 rule for every seven-fold increase in the hours after a nuclear explosion, the radiation levels in fallout drop by a factor of 10.3 The relative drop in fallout radiation levels using the 7/10 rule is shown in Table 5.3. 

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