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Radiation Protection Glossary

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Activity - the Bq
Gamma decay (Co-60) - two photons per transformation
In effect means:- 'how much Radioactive material' - in terms of rate of transformations where 1 Becquerel (Bq) =1 transformation per second. Therefore, for 1MBq of activity the disintegration rate will be 1,000,000 transformations per second. The non-SI unit of activity is the Curie (Ci) where 1Ci = 37 GBq (i.e. 37,000,000,000 transformations per second). Note that the rate does not represent the number of particles emitted per second take Cobalt-60 (Co-60) for example, each decay produces two gamma ray photons per disintegration.