A quasi-isothermal method of operating an absorbed-dose graphite calorimeter is described in theory and practice. In contrast with the well-known quasi-adiabatic operation, which entails temperature increases during measurements, in the quasi-isothermal mode the temperatures of the different graphite bodies remain constant except for small temperature drifts throughout the measurement. This implies that the temperature dependence of the specific heat of the absorber and of the sensitivity of the temperature sensor influence the absorbed-dose determination significantly less. The method is characterized by a power-compensating measuring principle which is illustrated with a 3-body graphite calorimeter. Comparisons of the quasi-isothermal with the quasi-adiabatic method of operation showed good agreement.

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Comparisons of the air kerma standards of six national laboratories, carried out in 137Cs gamma radiation, show an overall agreement of 0,8 % between the standards. This result is not quite as good as that of comparisons in 60Co gamma radiation, mainly because the evaluation of the ionization-chamber wall correction is less accurate for 137Cs radiation. However, this agreement is acceptable for radio-protection applications.

A personal dose equivalent comparison was carried out between the BEV and the PTB using a direct-reading electronic dosemeter system as a transfer instrument. This was the first comparison for the 'new' operational quantity, H p (10), for individual monitoring of strongly penetrating radiation and was performed in the preparatory stage of the European co-operation for Accreditation interlaboratory comparison IR4. For the BEV-PTB comparison described in this paper, the ISO water slab phantom and the ISO radiation qualities N-60 to N-300, S-Cs and S-Co were selected, whereby the axes of the radiation fields were perpendicular to the phantom surface. The results show very good agreement. In addition, the properties of the dosemeter system were investigated.