Abstract: Fixed environmental gamma radiation dose rate monitoring instrument is the main equipment to undertake environmental continuous monitoring tasks, but its inconveniencies in terms of installation and removal, as well as it prolonged submission period (about a week) affects the continuity of its continuous monitoring data. For the on-time calibration of the instrument, a portable ¹³⁷Cs irradiation device was developed using the Monte Carlo method with PTW dosimeter being adopted to measure dose rate of the radiation field. Finally, the portable irradiation device was used to calibrate on-site the fixed environmental gamma radiation dose rate monitoring instrument.

Key words: portable ¹³⁷Cs irradiation facility, Monte Carlo, reference radiation field, on-site calibration