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

5.83
TABLE 5.5.8. 70-Year Whole-Body Dose Commitment to
the Regional Population--Repository
Breach by Faulting and Flooding
Time of Event Man-rem
Closure + 1,000 Years
Spent Fuel 8.8 x 104
Reprocessing waste 1.7 x 10 5
Closure + 1,000,000 Years
Spent Fuel 1.4 x 105(*)
Reprocessing waste 2.8 x 104
Closure + 1,000,000 Years
Spent Fuel 7.1 x 104
Reprocessing waste 1.0 x 104
(*) The increase in dose between breaches at
+1,000 and +100,000 years is due principally
to the ingestion of 22 6 Ra from the
decay chain of 2 38 pu.
4 x 10- 11 /yr. The frequency that a high pressure aquifer exists with canister and surface
access is 0.005 (DOE/ET-0028, Sec. 7.4.9). A total probability for release to the biosphere
is 2 x 10-13 per year.
Using the probability estimate of 2 x 10- 13 /yr and the largest number of health effects
calculated, 140 (Table 5.5.8), the mathematical expectation of societal risk would be at most
3 x 10-11/yr or 3 x 10 -7 health effects over 10,000 yr.(a)
The population dose to the regional population from naturally occurring sources would
amount to about 1.4 x 107 man-rem over the same time period. Even in the maximum case, that
of 1.7 x 105 man-rem associated with release of radioactive material from nonsalt repositories,
the doses are on the order of 1% of that from naturally occurring sources.
One of the potential long-term effects of release of radionuclides to the river would
include the movement of these radionuclides to the ocean, where accumulation in mollusks may
occur resulting in another pathway to human exposure. It was assumed that the following
dilution factors(b) were appropriate for concentrations of elements in an estuary; e.g.,
concentration of cobalt nuclides in estuary water would be 0.01 of their concenrations in the
river.
(a) EPA commented that the calculation of probability was incorrect (see EPA Itr. comment
#86; Vol. 3 App C. p 34). The EPA estimate of the probability of a faulting and water
intrusion event was 4 x 10 -7 over a 10,000-year period compared to 2 x 10 - (2
x 10- 13 /yr x 1 x 104 yr) used in this Statement. EPA concluded that once a fault
intersected the repository that the probability of water intrusion in the long term
would likely be one. DOE believes the EPA argument has merit, however using the EPA
figures increases the societal risk to only 6 x 10 -5 over the 10,000 year period,
which is still an insignificant societal risk.
(b) Dilution factors are highly dependent on the specific river system and estuary of
interest. The dilution factors presented here were developed for movement of radionuclides
from reactor effluent water at the Hanford Project in Eastern Washington via
the Columbia River to Willapa Bay, Washington, where oysters are harvested.