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

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DOSE CALCULATIONS
population density of 90 person per square km (230 persons per square mile). If this is a
weighted average, the weighting factors should be given so that their validity can be
evaluated. (208-NRC)
Response
2
The population density, 90 persons/km 2 , is a weighted average. Fifty percent of the
AFRs were assumed to be in the West (40/km 2 ) and 50% were assumed to be in the East
(130/km 2 ) for an average of about 90/km 2 . These are equivalent to the 330/mi 2 and
110/mi 2 given on draft p. D.5.
Draft p. D.8
Issue
The model used to estimate the population dose commitment from 14 C is too conserva-
tive (i.e., overestimates the impact). If dilution by the Suess effect is not considered
and the total number of health effects is integrated over all time, the release of 1.4 MCi
(from Table 3.1.68) would result in about 5 x 106 deaths, assuming a stable world popula-
tion of 6.4 x 10 people. A more realistic comparison might be to the natural production
of 14C and associated health risk. (113-EPA)
Response
Suess effect is dilution of 14C with increased CO 2 from fossil fuels. This could
dilute 14 C by a factor of 0.5 - 1.0. Certainly this small change is far less conservative
than integrating population dose out to time infinity like EPA suggests. Even 5 x 10 6
deaths are small by their method. For example, a constant population implies death rate =
birth rate = 1.9% per year, or (1.9 x 10-2/yr) x (6.4 x 109) = 120 million deaths each
year. This is 24 times the 5 x 106 value of EPA in the first year alone. The model use
was designed for reasonable times not infinite times, and the DOE feels that it works well
for the times for which it was used. If health effects were integrated to infinite time, a
model which took into account the sinks for 14C (such as the deep ocean), which remove it
from the human biosphere, would have been used.
Draft Appendix I
Issue
This appendix as well as Appendix G to DOE/ET-0029 present impacts at time periods of
102 years, 105 years, and 106 years. Sometimes 104 years is discussed. Since pre-
liminary versions of the EPA standard for high-level waste specifically reference the 10 4 -yr
period, presentation of cumulative dose calculations for this time period for all cases
studied would be prudent. (208-NRC)