**4.1 New recalculated values of**

Table 1, lists recalculated air kerma rate constants for the 35 radionuclide used most often in gamma ray dosimetry and practical applications. For every radionuclide in the table are given the following data:

 in column 1 the symbol of gamma-emitting nuclide, in column 2 the half-life, in column 3 the low- energy photon spectra limit, in column 4 the high-energy photon spectra limit , in column 5 the calculated value of the constant in basic SI units, and finaly in column 6 the calculated value of the constant in practical units (Gy m2 GBq-1 h-1)

The last unit, for air kerma rate constant, is the practical one especially, for radiation protection and safety calculations in nuclear medicine laboratories, industrial radiography and many others applications of point gamma radiation sources.

The accuracy of calculation of air kerma rate constants is not more than three significant figures. The major portion of the standard error associated with these calculated values of arise from uncertainties in relative intensity measurements of the X ray and gamma ray photon spectra and intensity of omitted bremsstrahlung radiation.

Bremsstrahlung radiation contributes to the total air kerma rate constant by, for exam≤≤le, for 60Co, not more than 0.4%, and this decreases markedly with decreasing photon energy (BCRUM, Br.J.Rad., 55, 1982). The contribution to from the omitted photons of energies < 20 keV, varies from radionuclide to radionuclide, this is not interesting for the purposes of practical health physics, but is of interest in specific nuclear medicine radionuclide applications.

#### **4.2 Examples of our previous measurements of photon spectra and calculation of for selected radionuclide**

The next section of the text shows, as examle, the data of our previous measurement of the photon spectrum and the results of calculating the air kerma rate constants for the three selected radionuclides ( 182Ta, 192Ir and 226Ra in equilibrium with its decay products).
