Response of Photon Dosimeters and Survey Instruments to New Operational Quantities Proposed by ICRU RC26

Operational quantities in radiation protection are defined as conservative estimates of the protection quantities, which are generally not accessible to measurement. Radiation protection dosimeters and monitors are calibrated in the operational quantities. An ICRU Report Committee works on a proposal to replace the operational quantities for external radiation ambient dose equivalent, H*(10) and personal dose equivalent Hp(d, α) by quantities which are defined in close relation to the protection quantities. In this note, the response of dosimeters and survey instruments for photon radiation to these new operational quantities is evaluated. Survey instruments, having a low-energy cut-off at 50 keV can simply be recalibrated in the new quantity ambient dose and function as usual. Personal dosimeters will show an overreponse to photons with energy below 50 keV and either the dosimeter holder or the evaluation algorithm must be adapted to the new quantity.