Analysis of Cancer Risks in Populations Near Nuclear Facilities Phase 1 (2012) / Chapter Skim
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Appendix I: Radiation Dose Assessment
Appendix I: Radiation Dose Assessment
Pages 371-388
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From page 371... ...
For example: • The immersion of an individual in a cloud of radioactive iodine generates an exposure pattern characteristic of external radiation -- namely, absorbed doses delivered at various depths in tissues from penetrating radiation (e.g., gamma rays) as well as skin exposure due to finite-range charged particles (e.g., electrons from beta de cay)
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From page 372... ...
licensing activities for nuclear plants are based on the very simplistic dosimetry model reported in ICRP Publication 2 (1959)
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From page 373... ...
However, because of the shorter half-lives of these radioisotopes, their relative contribution to doses to persons living farther downwind will be somewhat less than the relative effective dose factors shown in Table I.1. I.1.2 Doses from Deposited Radionuclides Calculations of external exposure and organ doses from particulate radioactive materials deposited on the ground are based on the same transport model used for estimating noble gas concentrations downwind and models for calculating dry and wet deposition and the dose rate per unit TABLE I.1 Exposure Rate Dose Conversion Factors Effective Dose Factor (Sv Bq–1 s m–3)
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From page 374... ...
The exposure rates for a given activity concentration in the soil will decrease as the activity moves down into the soil profile over time as a result of rainfall and human activity. Because of the very low effluent rates and the diffusion of the airborne activity over a large area, only the longerlived nuclides such as cesium-137 and cobolt-60 can potentially build up to activity levels high enough for the exposure rate to be distinguishable from even the temporal variations in terrestrial background levels at any site.
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From page 375... ...
was developed primarily for providing radiation protection guidance for occupational environments, although recommendations for members of the public living in the neighborhood of controlled areas are also provided. However, the ICRP recommendations for the public did not take into account differences in dose limits between workers and members of the public, nor did they use different biokinetic models; thus, the differences in maximum permissible concentrations only reflect different exposure periods, that is, 40-hour weeks for workers versus 168-hour weeks for the public.
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From page 376... ...
. Although it was recognized that the retention of particulate matter depends on many factors, such as the size, shape, and density of the particles, as well as their chemical form and whether the person is a nose or mouth breather, ICRP indicated that specific data were lacking, and therefore the distribution and fate of inhaled particles could adequately be described as in Table I.5.
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From page 377... ...
To calculate the absorbed doses, the retention and fate of a radionuclide taken into the body by ingestion or inhalation had to be described for individual radionuclides once they reached the blood. To do this for most of the radionuclides, particularly those for which the bone and GI tract were
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From page 378... ...
These systemic models are coupled with the appropriate intake model (ingestion, inhalation) and a dosimetric model that calculates the dose to all target organs and tissues per radionuclide decay to obtain exposure-specific dose coefficients.
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From page 379... ...
, which may be most applicable for calculating doses for an epidemiologic study, is described below. Over the past 50 years, a substantial increase in knowledge about radionuclide metabolism and biokinetics in humans and experimental animal models has occurred and has provided a basis for the development of more realistic biokinetic models of radionuclide uptake and retention, particularly at the organ and tissue level.
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From page 380... ...
Different levels of subcompartments within a tissue compartment can also be used when multicomponent retention patterns are needed. For example, multiple compartments have been employed for the liver in the plutonium systemic biokinetic model of ICRP publication 67 (1992)
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From page 381... ...
I.2.1.1 Human Respiratory Tract Model The HRTM is actually a second-generation replacement of the simple respiratory tract model published in ICRP 2 (1960) ; it replaced the intermediate model published in ICRP Publication 30 (1979)
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From page 382... ...
The HRTM is an age-dependent dosimetry model whose morphometric and physiologic characteristics have been defined for reference ages of 3 months; 1, 5, 10, and 15 years; adult; and all for both genders. As such, age-dependent dose coefficients (dose per unit intake)
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From page 383... ...
is a biokinetic and dosimetric model of the human alimentary tract that replaces the previous GI tract model of ICRP Publication 30 (1979)
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From page 384... ...
This is due to the fact that most of the cancers linked to radiation in the alimentary tract are epithelial in origin. Transit time parameter values have been provided for different types of ingested materials (solids, caloric and noncaloric liquids, and total diet)
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From page 385... ...
Additionally equivalent doses have been provided in electronic form by ICRP on CD. I.2.1.4 Comparison of USNRC and Recent ICRP Dose Coefficients In Table I.6, the inhalation dose coefficients from USNRC Regulatory Guides are compared with those derived from recent ICRP publications (ICRP, 1995b)
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From page 386... ...
. Permissible Dose for Internal Radiation, ICRP Publication 2 1959 Superseded by ICRP Publication 30.
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From page 387... ...
. Human Alimentary Tract Model for Radiological Protection.
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