double flash

noun2

1. •
   The characteristic visual phenomenon produced by the atmospheric detonation of a nuclear weapon, consisting of a very brief, bright flash of light which dims rapidly, followed by a second, gradually brightening flash.

   • On 22 September 1979 at about 1 a.m. GMT, a US Vela satellite passing over the South Atlantic detected a double flash of light in the vicinity of Prince Edward Island. — 2010
2. •
   A system using two flash separators to separate phases of a working fluid.

   • Dipippo, in 2008, reported that the double-flash plant increased power output by 15-25% compared to a single flash plant under the same geothermal fluid conditions [9, 10]. — 2018