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.

Search the Glossary by either clicking on a letter or typing a keyword into the search box. This glossary is relational so when looking at one term you can click through to other related terms as required.

For formal advice, see our Radiation Protection Adviser pages. 

AmBe Americium-Beryllium neutron source

An AmBe (Americium-Beryllium) source is a special type of industrial neutron source. It is made in the form of a capsule which contains a finely blended powder of radioactive Am-241 (Americium) and Beryllium (Be). The AmBe source works on the interaction of the alpha particles from the Am-241 with Beryllium:

\[\alpha+Be^{9}\rightarrow C^{12}+n\]
The neutrons formed are emitted in the energy range of 0.1 - 11 MeV, with an average energy of 4.2 MeV.

Typical neutron output can be specified as 2.2 x 106neutrons/s per 37 GBq (1 Ci). The half-life of the source is 432 years (i.e. based on Am-241); the source usually has a recommended working life of 15 years.

Typical dose rates will be in the order of 0.7 micro Sv/hr at 1 m per GBq (gamma) and 0.6-0.7 micro Sv/hr at 1 m per GBq (neutron). Knowing the neutron and gamma dose rates per known activity is useful when determining the transport index (TI) - this is required when transporting the packaged source around.

Typical applications include:

  • Well logging
  • Industrial gauges
  • Porosity / moisture measurements
  • Prompt Gamma Neutron Activation Analysis (PGNAA) - security applications

Typical source activities available range from around 37 MBq-740 GBq (1 mCi to 20 Ci). Note that where the Am-214 activity exceeds 60 GBq then the source becomes a High Activity Sealed Source (HASS). More Ionactive resource on HASS sources can be found here: 5. High Activity Sealed Sources (HASS).

In the beginning, there was nothing, which exploded

– Terry Pratchett -