Study on the effect of build-up plate to calibration factors for personal dosemeters in a 6-7 MeV high energy ray (R-F) reference field

Kowatari, Munehiko; Yoshitomi, Hiroshi   ; Yoshizawa, Michio  

Calibration factors for widely available active and passive dosemeters (Aloka PDM-122-SZ and PDM-222-SZ, Fuji NRF31, Glass-Dosemeters (GD) and OSL) in Japan were obtained under conditions with and without BUPs in the 6-7 MeV high energy ray reference field. As for the condition with the BUP, calibration factors for personal dosemeters were obtained in accordance with the recommendation of ISO 4037-3, using a PMMA-made BUP with the dimension of 30 30 2.5 cm. Irradiating the same personal dosemeters without the BUP, calibration factors were then obtained and comparison was made with those under the condition of BUP. Calibration factors of each dosemeter obtained under the condition with the thick BUP were determined to be between 0.91 and 1.0. On the other hand, calibration factors of GD and OSL were determined to be less than 0.7. This implies that readings of GD and OSL would overestimate under the condition which charged particle equilibrium was not properly achieved.