JJG 521-2006

This regulation applies to the initial verification, subsequent verification, and in-use inspection of portable, mobile, or fixed instruments for measuring environmental X-ray and gamma radiation air kerma rates (absorbed dose rates) (hereinafter referred to as air kerma rate instruments).
The range of air kerma rates for X-ray and gamma radiation is 30 nGy/h to 10 μGy/h, and the radiation energy range is 50 keV to 15 MeV (for instruments that may be used to measure high-energy photons around nuclear reactors, the radiation energy range also includes a photon energy verification point of 6 MeV). This regulation also applies to instruments that use ionization current, count rate, or other integration methods to measure and display average air kerma rates over a certain period of time.
This regulation does not apply to the verification of instruments for measuring environmental X-ray and gamma radiation air kerma (cumulative dose) rates; nor does it apply to the verification of thermoluminescence dosimeters or other passive measurement devices, as well as beta radiation instruments.