Holodeck reactor is a technology used on Starfleet ships that powers the holodeck.
In 2371, the crew of the USS Voyager tried hooking up the holodeck reactor to the ship's systems for an additional power source. However, it ended up blowing half the relays on the ship. Ensign Harry Kim found that the holodeck reactor was not compatable with Voyager's systems. (VOY: "Parallax")