Radiation Protection Glossary

A radiation protection glossary for Radiation Protection Supervisors (RPS), Radiation Protection Advisers (RPA) and anyone else interesting in radiation safety terms and definitions. The glossary is a mixture of health physics , phrases related to radiation protection legislation, transport, practical safety, technical terms and similar.

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For formal advice, see our Radiation Protection Adviser pages. 

Specific Activity

Specific activity is taken to be the Activity (Bq) per unit mass (grams),normally expressed as Bq/g. Specific activity is related to Half-Life such that the shorter the half life the higher the specific activity. For example, the specific activity of natural Uranium is 25.4 kBq/g and has a half life of 4.51 E9 years (4510 million years). Compare this to Polonium - 210 which has a specific activity of 166500 GBq/g and a half life of 138 days.

If you start from nothing, it is very difficult to get anywhere

– Gerhard Herzberg -