Radiation Protection Rules of Thumb & FAQ

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!

A short and simple article looking at the conversion of 10th value thickness (TVT) to 1/2 value thickness (HVT), or the reverse process. Note that sometimes TVT is known as TVL (10th value layer) and HVT is known as HVL (1/2 value layer).

The Radiation Protection Supervisor (RPS) is a statutory appointment required by the UK Ionising Radiations Regulations 2017 (IRR17). The RPS is appointed in writing by an employer who works with ionising radiation. The RPS is required to supervise the radiation safety aspects of the work, in compliance with local rules.

There is quite a lot in this resource article even though we will not labour the physics of these terms. We explore the SI base unit of radiation exposure, absorbed dose (the Gray - Gy), and then contrast with biological effective dose (Sievert - Sv). Number multiplier examples will be explored and the important difference between dose and dose rate is highlighted. Finally we will also note the non-SI units of the Rad and Rem and look at conversions.

The SI unit of radioactivity is the becquerel (Bq). In this resource we will look at some typical activity values you might find in nature or in the workplace. Number multipliers will be explored as will conversions e.g. to the non-SI radioactivity unit of the Curie (Ci). Some interesting facts will be included such as 'why do certain UK industries still think in terms of the curie?!'.