For a mixture of radionuclides whose identities and respective activities are known the basic radionuclide values given in Table 1 of Schedule 1 may be determined as follows—

• where

• f(i) is the fraction of activity or activity concentration of radionuclide i in the mixture;

• X(i) is the value of A1 or A2, or the activity concentration for exempt material or the activity limit for an exempt consignment as appropriate for the radionuclide I; and

• Xm is the derived value of A1 or A2, or the activity concentration for exempt material or the activity limit for an exempt consignment in the case of a mixture.

When the identity of each radionuclide is known but the individual activities of some of the radionuclides are not known, the radionuclides may be grouped and the lowest radionuclide value, as appropriate, for the radionuclides in each group may be used in applying the formulae in paragraph 1 above and paragraph 4(b) of Schedule 4. Groups may be based on the total alpha activity and the total beta/gamma activity when these are known, using the lowest radionuclide values for the alpha emitters or beta/gamma emitters, respectively.