is a unit of absorbed radiation
dose. The rad was first proposed in 1918 as "that quantity of X rays which when absorbed will cause the destruction of the malignant mammalian
cells in question..." It was defined in CGS units
in 1953 as the dose causing 100 ergs
of energy to be absorbed by one gram
of matter. It was restated in SI units
in 1970 as the dose causing 0.01 joule
to be absorbed per kilogram
The United States Nuclear Regulatory Commission requires the use of the units curie, rad and rem as part of the Code of Federal Regulations 10CFR20.
The older quantity and unit of radiation exposure (ionization in dry air) is the "roentgen" (R), where 1 R is equal to 2.58 × 10<sup>-4</sup> C
/kg. The older quantity and unit of absorbed dose is the "rad," where 1 rad = 0.01 J/kg. The material absorbing the radiation can be tissue or any other medium (for example, air, water, lead shielding, etc.). To convert absorbed dose to dose equivalent, or "rem
," the biological effects in man are now considered, which is done by modifying with a quality factor. For practical scenarios, with low "linear energy transfer" (LET) radiation such as gamma or x rays, 1 R = 1 rad = 1 rem.
The Système International
has introduced as a rival unit, the gray
(Gy); the rad is equal to the centi
and 100 rads are equal to 1 Gy. The continued use of the rad is... Read More