Sievert Nuclear Regulatory Commission permits the use of the units curie, rad, and rem alongside SI units, the European Union European units of measurement directives required that their use for "public health ... purposes" be phased out by 31 December 1985. An older unit for the dose equivalent is the rem, still often used in the United States. One sievert is equal to 100 rem: Sievert The sievert (symbol: Sv) is a derived unit of ionizing radiation dose in the International System of Units (SI) and is a measure of the health effect of low levels of ionizing radiation on the
Rad (unit) nuclear applications can survive up to 100 Mrad (1 MGy). Metals creep, harden, and become brittle under the effect of radiation. Foods and medical equipment can be sterilized with radiation. In the 1930s the roentgen was the most commonly used unit of radiation exposure. This unit is obsolete and no longer clearly defined. One roentgen deposits 0.877 rad in dry air, 0.96 rad in soft tissue, or anywhere from 1 to more than 4 rad in bone depending on the beam energy. These conversions to absorbed energy all depend on the ionizing energy of a standard medium, which is ambiguous