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. 

HASS Sources

HASS sources (High Activity Sealed source) require significant control measures due to the significant radiation hazards that may exist should the source become uncontrolled. The aim is to ensure that proper controls are in place throughout the entire life cycle of the source from production, purchase, use, storage and eventual disposal. These controls are designed to ensure that sources cannot be lost, that the threat of theft is minimised, and that sources can not be purchased unless there is a disposal route and resources available to affect that disposal when required.

Note that a HASS source ceases to become a HASS source when the radioactivity is below the HASS threshold. Examples of HASS source activity are as follows:

  • Am-241 (60 GBq)
  • Cs-137 (100 GBq)
  • Cf-252 (20 GBq)
  • Co-60 (30 GBq)
  • Ir-192 (80 GBq)
  • Ra-226 (40 GBq)
  • Se-75 (200 GBq)

The units above are in becquerels (i.e. 10^9 Bq).

Physics is really nothing more than a search for ultimate simplicity, but so far all we have is a kind of elegant messiness

– Bill Bryson -