What is radiation Skyshine - and does it matter to me?

Radiation skyshine is where radiation (predominately gamma or x-rays photons, or neutrons) scatter within air (and other objects) above a facility which is either open topped (no shielding) or has reduced shielding. Some of the radiation emitted from within the facility will scatter upwards to the top of the facility, and some of this will then scatter downwards towards the ground - the other side of the facility shielding. It may be that direct measurements from the source of radiation through the shield are negligible. However, as you move away from the facility a peak dose rate will be measured some distance from the shielding (maximum skyshine) before reducing with further distance from the facility. It matters to you,  since some have ignored this phenomenon and only discovered higher dose rates some distance from the facility many months later.

A more rigorous explanation of Skyshine can be found here: Skyshine – radiation scattering around and over shielding.

Updated May 2025. For an interactive demonstration of radiation skyshine visit the following resource: Radiation skyshine (photon scattering) over a shielding wall widget. 

Updated May 2026. If you fancy calculating skyshine then try out this new Ionactive resource: Gamma Radiation Skyshine Calculator.