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gray

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The unit of absorbed dose in SI, used in studying and regulating ionizing radiation. Symbol, Gy. One gray is the quantity of ionizing radiation that, absorbed in a mass of 1 kilogram, would impart to it 1 joule of energy. The gray replaces the rep. It is named for the British physicist Louis Harold Gray (1905 – 1965).

The gray was adopted as the SI unit of absorbed dose by the 15th CGPM in 1975 (Resolution 9). In 1976, the CIPM also approved the use of the gray as a unit of specific energy imparted, kerma, and absorbed dose index, by approving a report of the Consultative Committee for Units, which had adopted a recommendation of the ICRU.

In SI base units, the gray has the dimensions meter²⁄second².

K. Lidèn.
SI Units in Biomedical Dosimetry.
Biomedical Dosimetry. Proceedings of an International Symposium on Advances in Biomedical Dosimetry Held by the International Atomic Energy Agency in Vienna, 10-14 March 1975.
Vienna: International Atomic Agency Agency, 1975.

Describes the rationale behind the ICRU's recommendation that the CGPM adopt the gray.