They are stasis charges. You place stasis chargers there.

If the reactor starts exploding, special cells pop up around the map. Those cells go in these receptacles.

i'm not talking about the 6 lasers, i'm talking about the 4 other things outside the chamber

the large towers? those are the particle enrichment towers. allow you to refuel fuel cells while the reactor is running

oh, thanks

Oh. Those. When the Reactor is running, you put depleted cells (either spat out by the Reactor, or delivered at the Train Depot) into these towers.

In the control area, there's a room past the computer room that has panels labelled one to four.

How-to:
You can use those panels to enrich the cells. The small slot at the bottom of the panel is a speed control. Depending on which part you press, the coloured vertical bars on the left and right will fill up.

If the bar on the right fills up, the cell is enriched, and can be removed from the tower, and used as normal.
If the bar on the left fills up,... Well, don't let that happen. If the bar gets starts topping up, then an alarm will sound. You should consider slowing the enrichment down, or pressing the red button to halt the process and dump the stress.