Radiation Units

Radiation Units, units of measurement for radioactivity and radiation doses. In the International System of Units (SI), the activity of a radioactive source is measured in becquerels (Bq) where one becquerel is equal to one nuclear disintegration per second (another unit is the curie). The exposure is measured in coulombs per kilogram (C kg^–1), the amount of ionizing radiation (X rays or gamma rays) that produces one coulomb of charge in one kilogram of dry air (replacing the roentgen). The absorbed dose of ionizing radiation is measured in grays (Gy) where one gray is equal to one joule of energy being imparted to one kilogram of matter (another unit is the rad). The dose equivalent, which is a measure of the effects of radiation on living organisms, is the absorbed dose multiplied by a suitable factor that depends upon the type of radiation. It is measured in sieverts (Sv), where one sievert is a dose equivalent to one joule per kilogram (an older unit is the rem).