MANAGEMENT OF NORM IN THE PETROLEUM INDUSTRY Akpojevwa Tega Naomi, october 2016 | Page 37

2.2.2 Effective Dose Rate
The SI unit for absorbed (energy) dose is the Gray (Gy). One Gray equals 1
J/kg. The unit for the effective dose is the same as for absorbed dose, J/kg, and
its special name is sievert (Sv). Sieverts are frequently expressed per unit time
such as per hour (Sv/hr) or per year (Sv/a).
Effective dose is of particular importance in radiation protection since:
• It applies to all kind of radiation exposition (X-rays, γ-rays, electron, α,
etc.)
• Legal limits and ‘attention levels’ are usually expressed in terms of
effective dose
• Radiation protection for a generic exposure scenario or a specific task is
essentially connected to the corresponding effective dose.
Clearly, both the type of radiation and type of exposure play a role in
determining effective dose, with α particles representing a greater dose
equivalent than Beta-β particles and Gamma-γ-rays and where exposure to the
colon or lungs resulting in a greater effective dose than exposure to the skin
(where the dead cells of the outer skin absorb some of the radiation).
However, the effective dose cannot be directly measured. It is necessary to use
methods and quantities that enable an estimation of the effective dose
conservatively. These methods differ primarily in relation doses resulting from
external or internal sources.
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