Technical Guidance

Here you will find data and articles on radiation shielding, frequently asked questions (FAQ), monitor performance, specific gamma ray constants, mathematical derivations, radiation protection widgets  - everything we have personally found useful from our own tool kit. New resources will be uploaded here from time to time.

For formal radiation safety advice, visit our Radiation Protection Adviser (RPA) services page. 

  • The Gamma Ray Constant (Video)

    Published: May 10, 2024

    Source: Ionactive Radiation Protection Resources

    • Gamma Ray Constant
    • Radioactive materials
    • Absorption
    • Dose
    • Accumulated dose
    • Guiding approximations
    • Computer simulation
    • D=ME/6r2
    • Energy MeV
    • What receives the dose?
    • Point source
    • Inverse square law
    • Energy absorbed per unit volume
    • Mass Energy Absorption Coefficient

    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. 

    Read more
  • The Geiger-Muller tube - radiation detector (video)

    Published: May 04, 2024

    Source: Ionactive Radiation Protection Resource

    • GM Tube
    • Geiger Muller tube
    • gas filled detector
    • GM Counter
    • radiation detector
    • Alpha radiation
    • beta radiation
    • Gamma radiation
    • neutron radiation
    • boron
    • inert gas
    • argon
    • neon
    • radiation window
    • thin mica
    • potential difference
    • Anode
    • Cathode
    • end cap energy filter
    • ambient count
    • ambient dose
    • gas amplification
    • electric field
    • avalanche effect
    • dead time
    • recovery time
    • recombination
    • quenching
    • Dose Rate
    • counts per second
    • CPS
    • Contamination
    • pulsed radiation

    An animated video explaining how the Geiger-Muller tube functions - a classic radiation detector which was envisaged in 1908,  practically built in 1928, and is still a widely used detector today in 2024 (nearly 100 years later!). 

    Read more
  • Dose rate through a small aperture widget

    Published: May 03, 2024

    Source: Design & implementation by Dr Chris Robbins (Grallator) / Facilitated by Ionactive radiation protection resource

    • Gamma rays
    • aperture
    • Dose Rate
    • widget
    • Calculator
    • equivalent dose
    • effective dose
    • Whole body exposure
    • Nuclear gauge accident dose rates
    • Nuclear gauge
    • Inverse square law
    • dose rate through small hole

    Imagine a radioactive source holder breaking away from an industrial nuclear gauge  - forming a small aperture from which gamma rays can be emitted. What would the dose rate be at various distances from the aperture, and what % of the body trunk would be exposed at each distance? When would an equivalent dose to a part of the body become a whole body effective dose? This interactive widget sets out to answer these questions. 

    Read more
  • Radioactive source holders - Dose rate through an aperture

    Published: Apr 23, 2024

    Source: Dr Chris Robbins, Grallator / Ionactive radiation protection resource

    • Shielding aperture
    • Nuclear gauge
    • Nuclear density gauge
    • Radiation through an aperture
    • Whole body exposure
    • effective dose
    • Nuclear gauge accident dose rates
    • Collimated radiation
    • Inverse square law
    • Multi-phase flow meter
    • Radioactivity

    This article, and our discussions with Dr Chris Robbins of Grallator, was born from a consideration of when a radioactive source holder (such as that fitted as part of a nuclear gauge) might become detached during a radiation accident, such that the radiation from the source is exposed directly through a small aperture. This is reasonably foreseeable compared to a radioactive source which might be completely exposed (unshielded). What would the dose rates be at a certain distance from the source holder, and what % of the trunk of the body would be exposed? This article considers the maths / physics behind this situation which has been developed for Ionactive by Chris. Ionactive has then taken the results of this analysis and shown how it would apply to a real world radiation accident. 

    Read more
  • Gamma dose rate (D=AE/6r2) - or is it? A widget to calculate the validity of this formula.

    Published: Apr 02, 2024

    Source: Design & implementation by Dr Chris Robbins (Grallator) / Facilitated by Ionactive radiation protection resource

    • D=AE/6r2
    • D=ME/6r2
    • Gamma dose rate formula
    • Gamma emitter
    • Radioactivity
    • Co-60
    • Cs-137
    • Ir-192
    • I-125
    • Mass Energy Absorption Coefficient
    • Energy dose contribution
    • Soft tissue absorption
    • micro Gy
    • Absorbed dose
    • Gamma dose rate calculator
    • Gamma dose rate widget

    This resource uses a radiation protection widget to explore the validity of a popular gamma dose rate formula of the form:

    \[ \begin{align} D_{\mu Sv hr^{-1}} &= \frac{AE}{6 r^2 } \end{align} \]

    where D is dose rate in µSv/h, A is activity in (MBq), E is gamma ray energy in MeV, and r is the distance in m.

    Read more
  • Shielding gamma rays with thick water shielding - what if you fall in?

    Published: Mar 31, 2024

    Source: Design & implementation by Dr Chris Robbins (Grallator) / Facilitated by Ionactive radiation protection resource

    • Gamma rays
    • Spent nuclear fuel
    • Co-60
    • Cobalt-60
    • Storage pool
    • Water shielding
    • Dose
    • Dose Rate
    • TVT
    • 10th Value Thickness
    • Shielding pool
    • Gray (Gy)
    • Sieverts (Sv)
    • Dose assessment
    • Exposure calculation
    • Water pool
    • Water pond
    • Fall in water

    Large volumes of water (in pools / ponds) are often used for radiation shielding, particularly for spent nuclear fuel and high activity Co-60 sources in industrial irradiation facilities. The water provides shielding and cooling whilst allowing remote movement of highly radioactive items where operators stand safely outside the pool. Imagine falling in - how would you fair? Very well if you can swim as illustrated in this radiation protection widget.

    Read more

In the beginning, there was nothing, which exploded

– Terry Pratchett -