Stet radiation

Stet Radiation was a type of radiation that did not exist until around the year 100 trillion. The radiation was very deadly to humans and could easily vaporize them. The Tenth Doctor was not aware of its existence until Atillo informed him that the couplings room was flooded with it, and they needed to go in there in order to set of the gravity footprint required to launch the Utopia Project Rocket. (DW: Utopia (TV story)