Set of radiation protection related questions and answers often asked by RPS / RPO delegates and by people via email or social media

• Calculate an estimate of x-ray dose rate from an x-ray tube given kV and mA

Published: Mar 24, 2024

Source: Dr Chris Robbins, Grallator/ Ionactive Radiation Protection Resource

Tags:
• X-ray
• X-ray dose rate
• X-ray generator
• mA
• kV
• Calculate x-ray tube output
• Formula for x-ray tube output
• Calculate x-ray tube dose rate
• Anode
• Cathode
• Bremsstrahlung x-rays
• Characteristic X-rays
• Tungsten target
• Inverse square law
• Energy Absorption
• Mass Energy Absorption Coefficient
• Gray (Gy)
• NDT X-ray tube
• Medical X-ray tube

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.

Published: Mar 16, 2024

Tags:
• RPA
• RPA2000
• IRR17
• Registration
• Consent
• HSE
• Health and Safety Executive (HSE)
• Certain practices
• Specified practices

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.

Published: Mar 09, 2024

Tags:
• x-ray shielding
• Gamma ray shielding

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.

• How reliable is TVT (10th Value Thickness) in radiation shielding calculations?

Published: Feb 20, 2023

Source: Ionactive Consulting Radiation Protection Resource

Tags:
• TVT
• 10th Value Thickness
• TVL
• 10th Value Layer
• Linear attenuation Coefficient
• Mass Absorption Coefficient
• MFP (Mean Free Path)
• Buildup
• Relaxation length
• Mean Free Path (MFP)

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.

• How do I convert TVT (10th value thickness) values to attenuation for Gamma or X-ray sources of radiation?

Published: Feb 15, 2023

Source: Ionactive Consulting Radiation Protection Resource

Tags:
• TVT
• 10th Value Thickness
• Attenuation
• TVL
• 10th Value Layer

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!

• How do I convert TVT to HVT (or the other way around)?

Published: Feb 11, 2023

Source: Ionactive Consulting Radiation Protection Resource

Tags:
• TVT
• HVT
• TVL
• HVL
• !0th value thickness
• 1/2 value thichness

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).