ISO/FDIS 6980-1

This document specifies the requirements for reference beta radiation fields produced by radioactive sources to be used for the calibration of personal and area dosemeters and dose-rate meters to be used for the determination of the quantities H_p(0,07), H'(0,07;Ω), H_p(3) and H'(3;Ω), and for the determination of their response as a function of beta particle energy and angle of incidence. The basic quantity in beta dosimetry is the absorbed-dose rate in a tissue-equivalent slab phantom. This document gives the characteristics of radionuclides that have been used to produce reference beta radiation fields, gives examples of suitable source constructions and describes methods for the measurement of the residual maximum beta particle energy and the dose equivalent rate at a depth of 0,07mm in the International Commission on Radiation Units and Measurements (ICRU) sphere. The energy range involved lies between 0,22MeV and 3,6MeV maximum beta energy corresponding to 0,07MeV to 1,2MeV mean beta energy and the dose equivalent rates are in the range from about10µSv·h^-1 to at least 10Sv·h^-1.. In addition, for some sources, variations of the dose equivalent rate as a function of the angle of incidence are given. However, as noted in ICRU56^[5], the ambient dose equivalent, H*(10), used for area monitoring, and the personal dose equivalent, H_p(10), as used for individual monitoring, of strongly penetrating radiation, are not appropriate quantities for any beta radiation, even that which penetrates 10mm of tissue (E_max>2MeV).

This document is applicable to two series of reference beta radiation fields, from which the radiation necessary for determining the characteristics (calibration and energy and angular dependence of response) of an instrument can be selected.

Series1 reference radiation fields are produced by radioactive sources used with beam-flattening filters designed to give uniform dose equivalent rates over a large area at a specified distance. The proposed sources of ¹⁰⁶Ru/¹⁰⁶Rh, ⁹⁰Sr/⁹⁰Y, ⁸⁵Kr, ²⁰⁴Tl and ¹⁴⁷Pm produce maximum dose equivalent rates of approximately200mSv·h^–1.

Series2 reference radiation fields are produced without the use of beam-flattening filters, which allows large area planar sources and a range of source-to-calibration plane distances to be used. Close to the sources, only relatively small areas of uniform dose rate are produced, but this series has the advantage of extending the energy and dose rate ranges beyond those of series1. The series also include radiation fields using polymethylmethacrylate (PMMA) absorbers to reduce the maximum beta particle energy. The radionuclides used are those of series1; these sources produce dose equivalent rates of up to10Sv·h^–1.