Radiation Protection Rules of Thumb & FAQ

How do you calculate an estimate of dose rate from an X-ray tube give kV and mA? In this resource we consider a 'ballpark' estimate of radiation dose rate using some physics principles, including an estimate of % bremsstrahlung from an anode target, combined with a calculation of power density and consideration of average energy absorption rate.

At Ionactive we are often asked 'What is a Radiation Protection Adviser (RPA), and do we need one?' This is an interesting question and concept, since the question is aimed directly at an RPA. We give objective advice and for most uses of ionising radiation a Radiation Protection Adviser is required, sometimes only for initial advice via consultation, but more often than not via an official appointment (in writing). Here is a quick summary of the role of the RPA and why a user of ionising radiation will probably need to appoint an RPA.

What do lead codes mean and how do they relate to thickness? Often you might calculate a certain level of lead radiation shielding required (e.g. for an x-ray inspection enclosure) and need to supply this information to an architect who is helping you design the facility. They will ask you -"what code lead do we need to use? Find out what you need to know in this article.

A rule of thumb updated for 2024! This article considers the following expression D=ME/6r² which has turned up in text books and training courses, but there appears to be no direct reference to when it was created and by whom. We start by using the expression with Cs-137 and see how the results compare with other resources available for calculating dose rates for chosen radionuclides with given activity and distance. We then hand over to Dr Chris Robbins of Grallator who is a maths, physics and nuclear physics whizz who derives this expression from first principles, outlining the good, the not so good and how it can be improved.

The TVT (10th value thickness), and HVT (1/2 value thickness) are easy to use simplifications in radiation shielding calculations. They are a good approximation to the solution desired, and in many cases will give shielding results as good (i.e. as accurate) as the more complicated and expensive models (e.g. MicroShield and MCNP etc). However, they should be used with caution and especially where thin shields are required with low energy photons. The TVT may over estimate the shielding required, but not always. This resource will explore these issues and answer questions like 'is build up (B) accounted for in published TVT / HVT data' and similar. You will also note that there is a requirement to interpolate publicly available data (e.g. for linear attenuation coefficients) and this alone can explain why published TVT for a particular gamma emitter and shielding material can vary.

Using exact values of TVT (10 value thickness) is quite easy - just work in 1/10ths. However, a little more work is required when you have fractions of a TVT, or you want to know precisely the attenuation of a given radiation shield, or precisely how many TVT is contained within a given thickness of material. This article provides the information you need!