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. 

HVT - Half Value Thickness

Simply stated, the HVT is the thickness of a radiation shield that will reduce radiation gamma / x-ray dose rate (or dose) to 1/2 of the of the pre-shielded value. There are a number of factors that will potentially interfere with this approach, but HVT is still a good approximation in many cases.

HVT is related to TVT by the expression 3.32 HVT = 1 TVT. Head over to the TVT resource for a fuller explanation of this concept.

Reality is merely an illusion, albeit a very persistent one

– Albert Einstein -