Reaper hull material in and of itself is safe, especially after being passed through a gravitic plasma forge.

That being said, it reacts … somewhat weirdly to certain things, and it isn’t safe to use in a sense that if a normal warp sword is damaged and blows up it would make a pretty big bang, and this monster has six times as much eezo inside it.

So if it was damaged and blew up, the result would be pretty much a nuke.

Let’s put it like this.

I’ve made changes to how ships use eezo, but a cruiser needs about ten pounds of eezo to operate its core for a six month deployment.

There are fifteen pounds of eezo in that sword. A standard warp sword has two pounds.

Logical Premise wrote:

a cruiser needs about ten pounds of eezo to operate its core for a six month deployment.

There are fifteen pounds of eezo in that sword.

Yeah, a core detonation is a bit heftier than a nuke.

But hey! You could sneak it on to a Reaper and detonate it in there to destroy the Reaper!

This is a tactic the Thirty eventually use on Thessia. Even a conventional warp sword going off is basically like a CAIN detonation.