The new special names of SI units in the field of ionizing radiations

A letter from the International Commission on Radiation Units and Measurements (ICRU) announce two resolutions adopted by the 15th General Conference of Weights and Measures at its meeting in May-June 1975 concerning the adoption of special names for the SI unit the joule per kilogram, j/kg, when applied to absorbed dose and related quantities, and for the SI unit the reciprocal second, s-1, when applied to the quantity activity as a measure of the rate of spontaneous nucear transformation of radioactive nuclides. It was decided that the SI unit for activity should be the becquerel, symbol Bq, equal to the second to the power minus one and that the SI unit for ionizing radiations be the gray, symbol Gy, equal to the joule per kilogram, The ICRU now recommends that the special units the rad, the roentgen and the curie be gradually abandoned over a period not less than about 10 yr and replaced by the SI units the gray (Gy), the coulomb per kilogram (C/kg) and the becquerel (Bq), respectively. (U.K.)