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Management of Commercially Generated Radioactive Waste - U.S. ...

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D.1<br />

APPENDIX D<br />

MODELS USED IN DOSE CALCULATIONS(a)<br />

Calculational models and parameters were used in evaluating the radiological dose to<br />

both regional and world populations. The regional dose calculations are discussed for<br />

chronic and accidental releases. The worldwide dose considers the distribution <strong>of</strong> tritium,<br />

carbon-14 and krypton-85.<br />

D.1 DOSE TO REGIONAL POPULATION<br />

The doses caused by chronic and accidental releases <strong>of</strong> gaseous and liquid effluents<br />

from the facilities and processes investigated in this study were estimated using several<br />

calculational models. The models and parameters used were selected to give a realistic but<br />

conservative appraisal.<br />

D.1.1.1 Air Concentration<br />

D.1.1 Chronic Releases<br />

The concentrations <strong>of</strong> radionuclides released in the atmosphere from these facilities<br />

were estimated using a Gaussian model (Slade 1968). Meteorological data on the joint fre-<br />

quency <strong>of</strong> occurrence <strong>of</strong> wind speed, wind direction, atmospheric stability and release para-<br />

meters such as height and velocity for a particular plant were taken from the reference<br />

environment. The horizontal and vertical dispersion parameters, ay and oz, were taken<br />

from curves derived from the work <strong>of</strong> Pasquill and modified by Gifford (1977).<br />

D.1.1.2 Air Submersion Dose<br />

Air concentrations were estimated as outlined above for each <strong>of</strong> 16 sectors. For these<br />

sectors the centerline ground level dose was calculated for ten downwind distances from 1<br />

to 80 km. Radiation doses to skin and to whole body were estimated from these air<br />

concentrations.<br />

Both photons and beta particles can contribute significantly to the external dose to<br />

skin. The beta dose contribution is easily calculated using a semi-infinite cloud model.<br />

This model can be used because the range <strong>of</strong> beta particles in air is short compared to the<br />

dimensions <strong>of</strong> plumes considered. The gamma dose calculation is more complicated because <strong>of</strong><br />

the relatively long range <strong>of</strong> photons in air. To properly determine the gamma contribution<br />

it is necessary to perform a space integration over the plume volume. The integration tech-<br />

nique used in the reactor accident analysis computer program SUBDOSA (Strenge et al. 1975 is<br />

(a) In accordance with common practice, the term "dose," when applied to individuals and populations,<br />

is used in this report instead <strong>of</strong> the more precise term "dose equivalent" as<br />

defined by the International Commission on Radiation Units and Measurements (ICRU).

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