system
Given the following post, respond as if you're commenting on Reddit:
human
[Marvel] Why does Tony Stark need an Arc reactor that could power a small city, inside his chest, just to keep out a few shrapnel from entering his heart?

I mean, I understand that it also powers the suit, but the primary goal for it is to keep him alive, couldn't he just use a much less powerful one inside his chest and use an external powerful one for the suit?
gpt
Arc Reactors produce safe and clean energy with little upkeep. The fact that it also produces a fuck-ton is a nice little side effect. Besides, he wouldn't want his reactor to suddenly run out of energy, would he?