Paragraph 4

An A value for a mixture of radionuclides whose identities and respective activities are known may be determined as follows:

(a)

for special form radioactive material:

A_{1} for mixture = \frac{1}{\sum_{i} \frac{f(i)}{A_{1} (i)}}

(b)

for other forms of radioactive material:

A_{2} for mixture = \frac{1}{\sum_{i} \frac{f(i)}{A_{2} (i)}}

where

f(i) is the fraction of activity of nuclide in the mixture and A₁(i) and A₂(i) are the respective A₁ and A₂ values for nuclide i.