Reactor 1 Warp
The Reactor 1 Warp is a version of the Wrong Warp glitch that makes use of the countdown battle mode from Reactor 1, after defeating Guard Scorpion. Like all wrong warp glitches, it is only possible to do on PC.
Execution
To perform the Reactor 1 Warp, the player must have a save file in Reactor 1 immediately after defeating Guard Scorpion. It is recommended to have both Cloud and Barret's HP be low, usually from triggering double Tail Laser in the Guard Scorpion fight.
The player must load their Reactor 1 save and find an encounter, then kill off their party members to intentionally trigger a game over. The player can then load a save on the world map, and find another encounter. The countdown timer will activate, but will be set to zero, immediately ending the fight and warping the player straight back into Reactor 1.
If the player continues through the Reactor and takes the elevator, they will be taken to Reactor 5, instead.
If the player chooses to save the game immediately after warping, the save they create will not be correctly set in Reactor 1, but will instead be based on the battle ID of the last encounter they fought (not counting the one used to warp). This can be abused by using another world map save file with a fully dead party, and finding an encounter with an ID matching the field ID of the desired destination. However, it is important to note that the game will load the field coordinates from where the player saved in Reactor 1, which may not be valid coordinates on the resulting field.