Measurement of Reference Beta Particle Absorbed Dose Rate to ~(85)Kr and ~(90)Sr/~(90)Y sources

摘要

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 ratemeters-- used in beta dosimetry with purpose to radiation protection--- for determination of: the personal doseequivalent H_ρ 0.07??, and the directional dose equivalent H'0.07??. The ISO 6980-2 (2004) specifies themethods for the measurement of the reference beta particle absorbed dose rate D_(Rβ), for the ISO 6980-1 betareference radiation fields. This work presents two results: first, the determination of residual maximum betaenergy E_(res) =0.57 MeV, for the ~(85)Kr 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 roomtemperature, in air and under dark room. Second, the D_(Rβ) measurements with the ISO 6980-2 standardtechnique, for: ~(85)Kr source above mentioned; and the ~(90)Sr/~(90)Y source (1.850 GBq, model Beta SecondaryStandard BSS 1 serial 86), measurements done with an extrapolation chamber (PTW model 30-360). The D_(Rβ)'sobtained are: 24.38 μGy s~(-1) for ~(85)Kr at the calibration distance of 30 cm; and 405.3, 60.02 and 21.06 μGy s~(-1) forthe ~(90)Sr/~(90)Y at the calibration distances of 11, 30 and 50 cm, respectively. Furthermore the ~(85)Kr source has anuniformity in the dose rate <10%, with a equivalent dose per activity of 41.8 μSv h~(-1) MBq~(-1).