Table 4 Summary of the parameters used for the calculations of effective doses expected for each exposure scenario. For external exposure from gamma radiation, the specific activity depends on Ra-226, whereas the exposure to dust has to integrate the specific activity of each nuclide that is contained in the dust fraction.
Exposure pathway | Transport | Production | ||||
|---|---|---|---|---|---|---|
External exposure from nodules in cargo hold | External exposure from stored nodules | External exposure from stored slag | Inhalation of dust from nodules | Inhalation of dust from slag | Inhalation of dust during maintenance of dust filters | |
Specific activity [Bq/g] | 2.3 | 2.3 | 5.1 | See Table 3, column “Nodules” | See Table 3, column “Slag” | See Table 3, column „Filter Dust“ |
Working time [h/a] | 2000 | 400 | 400 | 1000 | 1000 | 24 |
Proportionality factor between specific activity and ambient dose rate (ADR) [µSv/h per Bq/g Ra-226] | 0.5 | 0.4 | 0.07 | - | - | - |
ADR H*(10) [µSv/h] | 1.16 | 0.93 | 0.36 | - | - | - |
Conversion factor H*(10) to effective dose | 0.6 | 0.6 | 0.6 | - | - | - |
Reduction factor through shielding/dust protection | 0.5 | no shielding | no shielding | no mask | no mask | no mask |
Unit dose of dust [µSv/mg] | - | - | - | 0.06 | 0.13 | 0.04 |
Dust concentration [mg/m3] 1 | - | - | - | 1.25 | 1.25 | 3 |
Dose factors for inhalation [µSv/Bq] | - | - | - | see Table 2 | see Table 2 | see Table 2 |
Respiration rate [m3/h] | - | - | - | 1.2 | 1.2 | 1.2 |
Effective dose [mSv/a] | 0.7 | 0.22 | 0.08 | 0.09 | 0.2 | 0.003 |
