Measurement of reference beta particle absorbed dose rate to 85Kr and 90Sr/90Y sources

The ISO 6980-1(2006) standard establishes the requirements for reference beta radiation fields. These reference fields are employed in the calibration of personal dosimeters, area dosimeters and dose rate meters-- used in beta dosimetry with purpose to radiation protection--- for determination of: the personal dose equivalent Hp(0.07), and the directional dose equivalent H'(0.07. The ISO 6980-2 (2004) specifies the methods for the measurement of the reference beta particle absorbed dose rate DRβ, for the ISO 6980-1 beta reference radiation fields. This work presents two results: first, the determination of residual maximum beta energy Eres = 0.57 MeV, for the 85Kr source (2.1 GBq, model FH46M, serial 8128BK) according to ISO 6980- 1, from the beta spectra measured at ININ-SSDL --using a 5 mm deep silicon surface detector operated to room temperature, in air and under dark room. Second, the DRβ measurements with the ISO 6980-2 standard technique, for: 85Kr source above mentioned; and the 90Sr/90Y source (1.850 GBq, model Beta Secondary Standard BSS 1 serial 86), measurements done with an extrapolation chamber (PTW model 30-360). The DRβ's obtained are: 24.38 μGy s-1 for 85Kr at the calibration distance of 30 cm; and 405.3, 60.02 and 21.06 μGy s-1 for the 90Sr/90Y at the calibration distances of 11, 30 and 50 cm, respectively. Furthermore the 85Kr source has an uniformity in the dose rate <10%, with a equivalent dose per activity of 41.8 μSv h-1 MBq-1. (author)