1 or 0 (true/false) - true if the reactor has completed its activation phase, and has gone dark.
1 or 0 (true/false) - true if the reactor has been activated, and has turned red.
Number of ticks the reactor has been active for. It finishes after 900 game ticks (45 seconds).
Additional fields for [nether reactor](https://minecraft.wiki/w/nether reactor).