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

5.86
this conversion, a regional population dose of about 2 x 105 man-rem is obtained.(a) By
comparison the dose to this population from naturally occurring sources over the same
period would be about 1.4 x 107 man-rem.
Unlike some of the other scenarios the contamination in this event could be expected to
reach the environment continuously over a long period of time. For example, the 70-year
dose to the maximum individual decreased from 1 rem to 0.5 rem between 2000 and 10,000 years
after disposal (a factor of 2 would be lost in the imprecision of the estimate). The total
dose to replicate regional populations over 10,000 years would be on the order of 3 x 10
man-rem (143-70 yr generations). The total regional population dose for this same period
from naturally occurring sources would be about 2 x 109 man-rem. As noted earlier the prob-
11 -13
ability of this event occurring is estimated to be between 4 x 10-11 and 2 x 10 13/yr. The
probability that it would occur sometime within a 10,000-yr period would be on the order of
4 x 10 -7 to 2 x 10 -9 . The mathematical expectation of societal risk would be less than one
fatality over 10,000 years.
5.5.3 Faulting and Ground-water Intrusion to a Domestic Well
In this scenario a fault intersects a repository (non-salt) and water from an aquifer
beneath the repository flows in small quantity through the repository to an overlying aqui-
fer that is tapped by a domestic well. The domestic well is postulated to be located about
3 km down gradient from the fault and is capable of producing about 20 liters of potable
water per minute.
In order to estimate the maximum consequences that might occur from the interaction
with the buried waste, the assumption is made that all water flowing through the fault
enters the domestic well. This suggests that the upper aquifer is of low permeability.
Most domestic production wells are not drilled in aquifers of low permeability. Thus, for
more usual permeabilities encountered, a much smaller fraction of the waste nuclides would
arrive at the well. The water travel time from the fault in the repository to the domestic
well would vary from 1000 to 2500 years depending on the streamline the water followed
between the source and the well, while transport times for radionuclides could vary from a
thousand to millions of years depending on the nature of the radionuclides and the sorption
characteristics of the medium through which the water was flowing.
Doses were calculated from the rupture and leaching of 1320 BWR fuel assemblies and
1230 PWR fuel assemblies for the spent fuel repository; and 210 high-level waste canisters,
30 RH-TRU waste canisters and 480 barrels of RH-TRU waste for the reprocessing waste repos-
itory. All of the stated radioactive content is leached out over a 10,000-yr period.
The maximum 70-yr accumulated whole-body doses to the maximum individual from specific
long-lived waste radionuclides that may be of interest and the time after connection with
(a) In reviewing the Draft EIS, EPA criticized this approach to population dose. At best,
the method is a crude approximation of the population dose; but this approximation was
made in lieu of reprogramming an existing dose code solely for this purpose. In any
event the population dose could not exceed the dose of the maximum individual times the
regional population (2 x 106 man-rem) and would likely be substantially less. (As in
the previous scenario of a stream through repository, most of the population resides
down stream from the entry of contaminated water.)