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

5.84
Dilution Dilution
Element Factor Element Factor
H 2 Cs 100
C 2 Sm 100
Co 100 Eu 100
Ni 100 U 100
Sr 100 Np 100
Nb, Zr 100 Pu 100
Sb 2 Am 100
Sn 2 Cm 100
I 2
Saltwater bioaccumulation factors were used to estimate the concentration of radionu-
clides in the edible portion of marine foods (Soldat, Robinson and Baker 1974). The 70-yr
dose to the maximum individual from ingestion of mollusks (at a rate of 10 kg/yr) for
repository breaches at 1,000, 100,000 and 1,000,000 years after repository closure were
calculated. The largest of these, 7.2 x 10-2 rem to the whole-body, would add about 1% to
the dose the individual would have received from naturally occurring sources for the same
period and would not add significantly to the maximum individual's 70-year dose commitment.
The second scenario developed for the repository fracture and flooding assumes that
radionuclides are leached from the waste and carried beyond the boundaries of the host rock
and are then transported via moving (100 m/yr) ground water through the ground before enter-
ing the biosphere (the R river).
In this scenario a migration path length of 10 km was investigated, using sorption
equibrium constants (Kd values) measured or estimated under conditions at the Hanford Site,
Richland, Washington. While these parameters are believed to be representative of average
conditions to be expected at candidate sites, all factors could vary by several orders of
magnitude.
Based on inventories of radionuclides in repositories and the models and dose calcula-
tion methods according to Lester et al. (1975) and Burkholder et al. (1975), doses were cal-
culated for the maximum individual.(a) Total body doses are presented in Table 5.5.9 as a
function of time since disposal and for leach rates ranging from 0.1% to 0.01% of inventory
per year.(b)
The doses given in Table 5.5.9 were calculated to result from leaching of all wastes
from a 50,000 MTHM example repository in salt. These doses would be about 2.5 times higher
for the repositories in granite or basalt and about 1.3 times higher should the event occur
in a shale repository due to larger amounts of waste contained in those repositories. In
(a) A computer model called GETOUT for hydrologic transport (Lester et al. 1978) was used
in conjunction with a dose to biota model (Burkholder et al. 1975) as adjusted for parameters
developed for the midwest reference environment.
(b) Several commenters on the draft concluded that total release of inventory in one year
as presented in the draft Statement was out of the question. As a onsequence the 100%
removal per year case is omitted. The leach rates of 1 x 10-5 g/cm -day used in the
fracturing and stream flooding scenario amounts to about 1% of inventory removed per
year, using assumptions that maximize the area available to contact water.