Abstract: The field monitoring method of directional dose equivalent rate $\dot{H}$′(3) in β-γ mixed field in nuclear facilities is introduced. Based on the developed directional dose equivalent rate meter of ZF-D300 , its response characteristics to gamma rays and beta rays in γ standard radiation field, β standard radiation field and combined β-γ standard radiation field are given. Combined with the data of ambient dose equivalent rate meters, beta spectrometer and gamma spectrometer, the data processing method for measuring $\dot{H}$′(3) in β-γ mixed field is given. In the standard β-γ radiation field established in the laboratory, the difference of the $\dot{H}$′(3) values measured by the extrapolation ionization chamber of the standard instrument and this data processing method is less than 1%. During the outage of a nuclear power plant, the method of monitoring $\dot{H}$′(3) in the β-γ mixed field is applied.

Key words: β-γ mixed fields, calibration factor, $\dot{H}$^*(10), $\dot{H}$′(3)