The unit of outdoor use of radioactive sources is Becker, symbol Bq, which is defined as the number of decays per second. If it decays once every second, it is 1 Becker; Commonly used units are Curie symbol Ci, 1Ci=3.7 times Bq power of 10, 1Ci= 1000mCi, 1mCi= 1000uCi.

Radioactive source-describes its size by activity, and the unit is the old special unit of Bekkerel (Bq) and Curie (Ci). It can be calculated according to the counting rate.

Exposure-ionization capacity of X-ray or γ-ray in air, in coulomb/kg, the old special unit is Roentgen (R), which can be calculated according to the activity of radioactive source.

Absorbed dose-the radiant energy absorbed by a substance. The unit of SI is Joule/kg, the special unit is Gory, and the old special unit is Rade. It can be calculated according to the exposure.

The relevant requirements of radioactive units stipulate that:

1, absorbed dose. The absorbed dose is the energy given by ionizing radiation to a unit mass of matter. Strictly defined as the quotient obtained by dividing the average energy de given by ionizing radiation to a substance with a mass of dm by dm, expressed by D, and its SI unit is gy, 1Gy= 1J/Kg. The unit used to be rad. 1 rad = 0.0 1 gray.

2. Half-life. The time required for half the nuclei of radioactive elements to decay is called half-life. As the radiation continues, the radiation intensity will decrease exponentially, and the time required for the radiation intensity to reach half of the initial value is called isotope half-life.

3. Radioactivity refers to the number of decays of radioactive nuclei in a specific energy state per unit time, which is denoted as a, A=dN/dt=λN, indicating the radioactive intensity of radioactive nuclei. According to the law of exponential decay, radioactivity is equal to the decay constant multiplied by the number of decaying nuclei.

Legal basis:

Article 13 of the Law of the People's Republic of China on the Prevention and Control of Radioactive Pollution shall meet the following conditions when applying for a license:

(1) Having a specialized radiation safety and environmental protection management institution;

(2) There shall be no less than 5 technicians specialized in nuclear physics, radiochemistry, nuclear medicine and radiation protection, among whom there shall be no less than 1 person with senior titles. Units that produce radioisotopes with a half-life of more than 60 days shall have not less than 30 professional and technical personnel mentioned in the preceding paragraph, including not less than 6 with senior titles;

(3) Personnel engaged in radiation work must undergo training and examination in radiation safety and protection professional knowledge and relevant laws and regulations, and key positions in radiation safety should be held by registered nuclear safety engineers.