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The definition was refined in 1950 as "that dose of any ionizing radiation which produces a relevant biological effect equal to that produced by one roentgen of high-voltage x-radiation." [19] Using data available at the time, the rem was variously evaluated as 83, 93, or 95 erg/gram. [20]
That model calculates an effective radiation dose, measured in units of rem, which is more representative of the stochastic risk than the absorbed dose in rad. In most power plant scenarios, where the radiation environment is dominated by X-or gamma rays applied uniformly to the whole body, 1 rad of absorbed dose gives 1 rem of effective dose. [5]
A dose rate is quantity of radiation absorbed or delivered per unit time. It is often indicated in micrograys per hour (μGy/h) [ 1 ] or as an equivalent dose rate Ḣ T in rems per hour (rem/hr) or sieverts per hour (Sv/h).
By definition, 1 Gy = 100 rad and 1 Sv = 100 rem. The fundamental quantity is the absorbed dose (D), which is defined as the mean energy imparted [by ionising radiation] (dE) per unit mass (dm) of material (D = dE/dm) [8] The SI unit of absorbed dose is the gray (Gy) defined as one joule per kilogram. Absorbed dose, as a point measurement, is ...
The roentgen or röntgen (/ ˈ r ɛ n t ɡ ə n,-dʒ ə n, ˈ r ʌ n t-/; [2] symbol R) is a legacy unit of measurement for the exposure of X-rays and gamma rays, and is defined as the electric charge freed by such radiation in a specified volume of air divided by the mass of that air (statcoulomb per kilogram).
The NRC's definition of dose equivalent is "the product of the absorbed dose in tissue, quality factor, and all other necessary modifying factors at the location of interest." However, it is apparent from their definition of effective dose equivalent that "all other necessary modifying factors" excludes the tissue weighting factor. [17]
Recognized effects of higher acute radiation doses are described in more detail in the article on radiation poisoning.Although the International System of Units (SI) defines the sievert (Sv) as the unit of radiation dose equivalent, chronic radiation levels and standards are still often given in units of millirems (mrem), where 1 mrem equals 1/1,000 of a rem and 1 rem equals 0.01 Sv.
For such purposes, doses should be evaluated in terms of absorbed dose (in gray, Gy), and where high-LET radiations (e.g., neutrons or alpha particles) are involved, an absorbed dose, weighted with an appropriate RBE, should be used" Radiation weighting factors are largely based on the RBE of radiation for stochastic health risks. However, for ...