Half Value Thickness 

HVT Half Value Thickness is the thickness of specified material which, when introduced into the beam of X or gamma radiation, reduces the intensity of the incident beam by a half. If the incident intensity is I0 then the transmitted intensity from the HVT of a material is I0. If the thickness of the material is twice the HVT, then the transmitted intensity is I0/4.

The HVT helps to simplify the calculation of the required thickness of shielding layers.

For more information on HVT and other radiographic terms see:
BS EN 1330-3: 1997 – Non-destructive testing. Terminology. Terms used in industrial radiographic testing

What the hec?! articles are not intended to be the definitive account on the topic or acronym in question. Readers’ comments and contributions are welcomed. Email: ndtnews@bindt.org