Nuclear

The mark a nuclear accident leaves: ground poisoned by a reactor explosion. It irradiates a step below uranium — out of a backpack too — and fades on its own through four steps, faster under water. Dug and carried like any block, but never crafted.

The brain of a reactor: it scans the shell, says what is wrong and exactly where, runs the reaction and delivers EU/FE. The room is optional — without one it runs weaker and melts the scenery.

A fuel rod's casing with no uranium in it: crafted 3x3, filled with a single piece of enriched uranium, and handed back by the column once the rod is spent.

The far end of the cooling loop: it takes steam from a pipe, releases it into the air as a plume and destroys it — 100 mB/t per nozzle.

A button made of shielding alloy: the way to pulse the airlock from inside a sealed room, built exactly like a vanilla button but able to survive what the room is for.

A transparent rack for four rods with two tanks — water and steam: filled by right-clicking, it wears every fuelled rod down together, and both the fuel and the coolant level read from across the room, with no menu at all.

A shell block that lights up only once the room is formed: the only source of light inside a sealed box, and at the same time a visible outside sign that the build was accepted.

A shielding-alloy panel — the only material a reactor room's sealed shell may be built from.

A transparent shell panel: it counts as wall exactly like casing, but no more than 30 % of a shell may be glass — past that the room stops being containment and becomes a display case.

The one place fluid may cross a sealed shell: a 50 mB/t crossing that works both ways — water in, steam out — and is still a full piece of wall.

A socket set into the reactor room's shell: the controller is walled in and has no face a cable can reach, so power leaves through a purpose-built piece of wall — a 512 EU/FE buffer that gives on every face and is topped up by the controller.

A lever made of shielding alloy: a held signal from inside a sealed room — the reactor's emergency stop, which neither breaks the room's shielding nor melts with its contents.

The reactor's fuel: enriched uranium in an iron sleeve on a shielding base. It holds 144,000 EU/FE, shows what is left of it as durability, and leaves an empty casing behind when it burns out.

The only way into a reactor room: it opens on a redstone pulse alone, shuts itself two seconds later, and never closes through whoever is standing in the doorway.

The only container that stops the radiation of its contents: uranium inside irradiates nobody. Iron-chest capacity (36 slots), needs no energy.