Dangerous Forces (version 1)

These three bright orange circles placed on the same axis constitute a special sign used to facilitate the identification of "works and installations containing dangerous forces" (e.g. dams, dikes and nuclear electrical generating stations), as defined in article 56 of the Protocol Additional to the Geneva Conventions of 12 August 1949, and relating to the Protection of Victims of International Armed Conflicts, June 8, 1977. It is forbidden by International Humanitarian Law to attack such installations if an attack may cause consequent severe losses among the civilian population.

See also:
https://www.cafepress.com/dangerousforce2