Dangerous Quantities of Radioactive Material (D-Values)

D-values are used by the Environment Agency (EA), SEPA and the UK police advisers (CTSA) to determine the source category and appropriate security measures for sealed sources, where this cannot be assessed directly from the use/practice. D (Danger) values are in TBq, and the quotient A/D (where A is the activity of a source in TBq) are used to determine source category. In the UK some sources are already categorised for security and this will then take precedence over A/D. For those into dosimetry calculations and assessments behind D values, section 3 onwards explain in detail how the values are derived.