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In order to assess the D value for each isotope, different scenarios are considered. Two D values are calculated (D1 and D2), and the lowest value for the radionuclide is taken.

The D1 value is the amount considered dangerous if not dispersed (e.g. encapsulated).

The D2 value is the amount considered dangerous if dispersed (e.g. ruptured).

Definitions and more information on D values are provided in the section on 'Impact on people and the environment' (page 8).