Assessment of radiation levels in and around plant is required to permit planning of dose reduction strategies. Radiation levels can be driven by direct radiation penetration or by scatter paths through a weak shield. (ie a duct)

Skyshine is the commonly used term for the scatter of radiation by air. At large distances from radiation facilities, the dose rate can be determined not by radiation which has penetrated the walls of the facility but that which has penetrated the often relatively weak roof and scattered in the air. The facility could for example be a reactor surrounded by its containment building, or a store for radioactive waste. The Skyshine document concentrates on gamma-ray sources in a specimen facility of simple geometric structure, and considers the variation of dose-rate on the ground with distance from the facility and the energy of the gamma-ray source. The point kernel code RANKERN is often used for Skyshine studies, and its validity for such calculations is assessed by comparison with the Monte Carlo code MCBEND.