**4. Results**

4 Gamma Radiation

*E* (2)

the energy-dependent mass energy-

(3)

(5)

(6)

(4)

*<sup>K</sup>*air <sup>=</sup>*<sup>k</sup>*

The kerma rate, d*K /*d*t,* is obtained from the kerma by substituting the flux density for

*A <sup>l</sup>* 

> *<sup>A</sup> <sup>k</sup> <sup>E</sup> l*

*i i*

*i i*

*i i*

*p E*

where is expressed in m-2 s-1. The quantity is derived from the activity *A,* of a radiation

*dt* <sup>=</sup> <sup>2</sup> <sup>4</sup>

If photons with energy *Ei* are emitted per decay event with yield *pi,* Equation 5 becomes:

*dK A*

By inserting Equation 6 in Equation 1, the following equation is obtained for

4

*dt l*

*air k*

*k*

*<sup>p</sup> <sup>E</sup>* 

*i i*

Starting from Equation 7, the air kerma rate constants, were calculated using data on mass energy-transfer coefficients for air (Hubbell, 1969; Hubbell & Seltzer, 2001) and data on photon emission yield in the process of decay of the radionuclides (Firestone, 1996; Stabin & Luz, 2002). The subscript implies that only photons with energy > , in MeV are included

Concerning the radiation spectra emitted per decay of a radionuclide, there are three types of photons: the gamma ray photons, those characteristic X-ray photons, those from internal conversion of gamma rays and electron capture and those accompanying bremsstrahlung processes of electrons from decay and internal conversion of gamma rays and X rays. In this calculation gamma rays and characteristic X-ray photons with energies >20 keV as value are only ones to have been taken into account. The contribution of bremsstrahlung

*dt*

By inserting Equation 4 in Equation 3, the following equation is obtained:

where is the flunce, *E* the photon energy, and

*air k dK <sup>E</sup>*

source in accordance with inverse square low:

*air dK*

2 <sup>4</sup>

<sup>1</sup>

**3. Calculation of** 

in the calculation.

radiation has not been included.

2 <sup>4</sup>

transfer coefficient for air.

the fluence in Equation 2:
