Radioactive amount

In Nuclear physics and Protection against radiation, the radioactive amount or concisément the amount indicates the energy deposited by unit of Masse by a Ionizing ray. A frequent application is to consider the energy deposited in a biological Tissu to envisage the medical effects of the Radioactivité: care of the Cancer S by Radiotherapy or Curiethérapie, prediction of the disease risks in the event of accidental exposure, etc

Unit

The unit of amount of the international Système is the Gray (Gy); it is a derived unit being worth a Joule by Kilogram. In other words, 1 Gy = 1 J/kg. Gray officially supplanted old units which remain however of everyday usage:

the Rad (rad) being worth 0,01 Gy;
the Röntgen (R), is an electric unit Charge per unit of mass being worth 0,258 m C.

Use

The effect on biological fabrics of the weak irradiations (< 0.1 Gy) is however badly described by the amount, because it depends on the relative biological effectiveness of the radiation considered and the relative sensitivity of the fabric irradiated. The equivalent of amount and the effective equivalent of amount, expressed in Sievert (Sv), take into account these corrections.

The radioactive amount is used in case acute irradiation (> 1 Gy), because the various radiations have comparable effectiveness then.

See too

Internal bonds

Gray ~ Rad ~ Röntgen
equivalent of amount ~ effective equivalent of amount ~ Sievert

External bonds

International Draft off the Commission one Radiological Protection, Basis for Dosimetric Quantities Used in Radiological Protection
Robert NR. Cherry, Jr., the ionizing rays, Encyclopedia of Safety and Health at the work, 3rd edition, chapter 48, ISBN 92-2-209203-1

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