The Gamma Ray Constant (Video)
Published: May 10, 2024
Source: Ionactive Radiation Protection Resources
An Ionactive video release created for us by Grallator in 2009. This video looks at the Gamma Ray constant of the form D=ME/6r2 (terms explained in the video page). Later more recent resource (i.e. 2024) takes the concepts in this video and develops them much further - looking at the detailed maths and physics (links will be found on the video page). There is still lots of good radiation protection educational content here despite its vintage.
Notes about this video
The expression subject to discussion in this video is as follows: \[ \begin{align} D_{\mu Sv hr^{-1}} &= \frac{ME}{6 r^2 } \end{align} \]
The terms are:
- M (radioactivity in MBq)
- E (energy in MeV)
- r (distance in m)
- 6 (the gamma ray constant, one of many possibilities)
The video resource presented here was written over 10 years ago, but the main findings / comments are still very relevant, namely that the above expression is somewhat of a compromise, especially for gamma emissions below about 60 keV (0.06 MeV).
You may wish to visit the following Ionactive resource: Formula for calculating dose rates from gamma emitting radioactive materials. [Ionactive comment: in this referenced resource the M (radioactivity in MBq) is replaced by A (radioactivity) ]. This subject area is then further explored by an interactive widget where you can see the above expression working for four different radionuclides (and note in particular that the value of the gamma ray constant changes) - this resource is: Gamma dose rate (D=AE/6r2) - or is it? A widget to calculate the validity of this formula.