What counts as Reactor Maintenance without dying?

[River Victor]

Mind Your Step acheivement. Like, from which area to which area? When do I start minding not dying? Which part of the story? Is it the nest? Or is it where all electrified walkways around the central reactor where the Orange Joes are swarming you? This is very unclear and I'm confused.

[Vzzdak]

Pretty sure it's just the Reactor Core, since that's where you are being careful about your steps.

Mind you, when I achieved this, the xenomorph was not present when I clicked the elevator button to leave, but suddenly I was stabbed through the back.

I still had the achievement, so there's a tease baked into the game.