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

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D.5<br />

from ingested radionuclides on natural aquatic or terrestrial populations. The most recent<br />

and pertinent studies point out that, while the existence <strong>of</strong> extremely radiosensitive biota<br />

is possible and while increased radiosensitivity in organisms may result from environmental<br />

interactions, no biota have yet been discovered that show a sensitivity to radiation expo-<br />

sures as low as those anticipated in the area surrounding fuel cycle plants. The BEIR<br />

Report (NAS-NRC 1972) states in summary that evidence to date indicates that no other living<br />

organisms are very much more radiosensitive than man. Therefore, no detectable radiological<br />

impact is expected on the aquatic biota or terrestrial mammals as a result <strong>of</strong> the quantity<br />

<strong>of</strong> radionuclides to be released into the River R and into the air by fuel cycle plants.<br />

D.1.4 Direct Radiation from Transportation<br />

The method used to calculate the dose to persons along the shipping route from a<br />

vehicle containing radioactive material follows that developed in WASH-1238 (USAEC 1972).<br />

The equation used to estimate population doses incorporates several factors that inte-<br />

grate the dose to an individual as the radiation source passes his location. The formula<br />

then integrates the dose to all persons within a designated population distribution. The<br />

factors considered are radiation source strength, velocity <strong>of</strong> the transport vehicle, popula-<br />

tion density in areas <strong>of</strong> exposure to passing source, attenuation factors due to gamma inter-<br />

actions with air, and buildup factor to account for the contribution <strong>of</strong> scattered radiation.<br />

The Department <strong>of</strong> Transportation's regulations limit the radiation level allowable out-<br />

side the transport container rather than restrict the container's contents. However, there<br />

is still a radioactivity content limit for each kind <strong>of</strong> packaging and for each toxicity<br />

grouping <strong>of</strong> radionuclides. Consequently, the shipping containers are designed and loaded<br />

with that regulatory limit in mind. For this calculation, based on the regulatory limit <strong>of</strong><br />

10 mrem/hr at 6 ft from the surface <strong>of</strong> the vehicle, the maximum radiation dose rate at 10 ft<br />

from the apparent center <strong>of</strong> the source was estimated to be 10 mrem/hr (USAEC 1972). The<br />

radioactive shipment. on the vehicle was considered to be a point source for distances from<br />

the source <strong>of</strong> 100 ft or more.<br />

The length <strong>of</strong> time an individual spends near a source is a determining factor in the<br />

total dose received; thus the velocity <strong>of</strong> the source is important. It was assumed that a<br />

long-haul, maximum-weight motor carrier shipment averages 720 miles per day and that a car-<br />

load rail shipment averages 200 miles per day. Based on a uniform distance traveled each<br />

day and uniform distribution <strong>of</strong> persons along the route, the cumulative radiation dose to<br />

the population is the same whether the vehicle is always moving at a constant rate <strong>of</strong> speed<br />

or is standing still part <strong>of</strong> the day. (Movement or lack <strong>of</strong> movement <strong>of</strong> the vehicle<br />

obviously will have an effect on the dose distribution among individuals within the exposed<br />

population.)<br />

It was assumed that the average population density is 330 persons per square mile in<br />

the United States east <strong>of</strong> the Mississippi River and in California, and 110 persons per<br />

square mile in the other midwestern and western states. It is further assumed that no<br />

people live within 100 ft <strong>of</strong> the railroad or highway right-<strong>of</strong>-way. The dose to persons

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