ON THE ACHIEVEMENT OF OPERATIONAL RADIATION PROTECTION QUANTITIES FOR MIXED PHOTON-NEUTRON RADIATION-FIELDS

In calibration fields for penetrating radiation, operational radiation protection quantitites such as H*(10) and H-p(10) are commonly derived from measurable quantities (spectral fluence for neutrons,, air kerma for photons) and calculated fluence to dose equivalent coefficients for neutrons and kerma to dose equivalent conversion coefficients for photons. The paper presents a theoretical study on the suitability of a small tissue-equivalent proportional counter (TEPC), inserted at a depth of 10 mm in a phantom, for measuring H*(10) and H-p(10). The differences between the definition of dose equivalent and the measurement principle of the TEPC are discussed. If the pressure of the TEPC gas filling, the phantom material and size are all correctly chosen, a reading which deviates by less than +/-25% from H-p(10) for photons and neutrons impinging on the phantom from the entire front hemisphere can be obtained.