Abstract: Fixed environmental gamma radiation dose rate monitoring instrument is the main equipment to undertake environmental continuous monitoring tasks, such instrument is usually not easy to remove and install, and the submission of a longer period (about a week), affecting the continuity of the continuous monitoring data.For the on time calibration of fixed environmental gamma radiation dose rate monitoring instrument, combined with the Monte Carlo method developed a portable ¹³⁷Cs irradiation device, PTW dosimeter was used to measure dose rate of the radiation field. Finally, portable radiation device was used to carry out on-site calibration experiments for the fixed environmental gamma radiation dose rate monitoring instrument.

Key words: Gamma ray portable irradiation facility, Monte carlo, Reference radiation field, On-site Calibration