2.22 SHORELINE EXTERNAL RADIATION
Proximity of individuals to shoreline soils contaminated
with radioactive surface water sediments may result in external dose. The
dose from this pathway is based on the average radionuclide concentration
in sediment over the exposure duration for the shoreline activities. Considerations
in evaluating this pathway are as follows.
- Transport Medium:
- radionuclide concentration in surface water at the shoreline location, Cswi, pCi/L, expressed
as a 70-year average value
- Special Process:
- loss of pollutants during transport in the surface water body by volatilization transfer of pollutant from water to shoreline sediment accumulation of pollutant in sediment over time presence of individuals near shoreline sediment dose rate eduction because shoreline is narrow
- Exposure Factors:
- shoreline event frequency, time per event, and exposure duration.
The loss of pollutants during transport in the surface
water body is evaluated using Equation (3). The transfer and accumulation
of pollutants in sediments is estimated using the same model describe for
dermal contact with shoreline sediments. The concentration to which individuals
are exposed is evaluated using Equation (76). This concentration is used
to estimate the total lifetime dose to radionuclide pollutants as follows:
(107)
where
Dhei = total lifetime dose for radionuclide pollutant i from external exposure to shoreline sediment (rem)
CSi = average concentration of radionuclide i in shoreline sediment over the shoreline exposure duration (pCi/m2)
Fhe = fraction of days per year that shoreline exposure occurs (dimensionless)
FEsl = shoreline use event frequency (events/d)
TEl = length of each shoreline exposure event (h/event)
SW = shoreline width factor for the exposure location (dimensionless)
DEgi = dose conversion factor for external exposure to radionuclides on a ground plane for radionuclide i (rem/h per pCi/m2)
EDhe = exposure duration for the shoreline external exposure pathway (yr)
The dose conversion factors are based on exposure to an infinitely large
plane source. Because the typical shoreline is better represented by a
long narrow source, the shore width factor is included to account for the
source being less than infinite.