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Troubleshooting & FAQ

Organised by symptom. Find what's going wrong, apply the fix, follow the link for the full mechanic. Most answers come back to the heat economy: fuel makes heat, exchangers and turbines turn heat into Drive Cells, and vents and hull ambient loss carry off the rest before it melts.

Neutronics: overview and fast start
Building a Reactor: cells, shell, commissioning
Fuel & Isotopes: the enrichment chain and β
Operating a Reactor: throttle, cruise/push, SCRAM
Breeding: breeder geometry, harvest timing
Byproducts & Waste: the isotope zoo and Nuclear Waste

Numbers below are the baseline; your server may tune them.

Getting started

How do I get fuel into the reactor?

Load it by hand at the Fuel Port, not the Core Console. Hold a Uranium-235 rod and click a Fuel Assembly cell; each rod adds a burn budget (~3 hours at the T1 recommended throttle). The Console is throttle and meters; the Port is fuel and internals. They're never fused. See Operating a Reactor.

Where does the fuel come from?

Mine Raw Uranium Ore (rare deep-planet veins), then enrich it at an Enrichment Centrifuge (module.reactor_enrichment) — a dedicated machine, not the ore refinery. That yields Uranium-235. See Fuel & Isotopes.

What's the safest way to start?

Buy a starter kit, build the shipped burner geometry (well-moderated, coolant-coupled), and run it at about 45% throttle. That holds a steady ~1000 Drive Cells/hr and never nears meltdown. The burner is idle-safe; leave it and it holds itself via Doppler feedback. See Neutronics.

It won't commission

Why won't the Core Console commission?

It's short a requirement and prints exactly which one. The Console lists every shortfall at once, so read all of them. Common gates:

Gate	What it means	Fix
not shielded	A Fuel/Exchanger/Coolant/Control/Moderator/Reflector cell touches open space	Wrap the core in Reactor Plating or Viewports so no core cell faces outside
fuel not controlled	A Fuel Assembly has no adjacent Control Rod	Put a Control Rod next to every Fuel Assembly — the rods are the throttle
coolant doesn't reach a Turbine	Exchanger coolant dead-ends	Join the coolant loop (coolant-to-coolant) all the way to a Turbine's coolant
vents don't exhaust	A Heat Vent or Turbine is buried	Move it to the outer wall so it vents to open space
network not coherent	Stray/detached blocks, or a missing Console/Turbine/Exchanger	Join everything into one connected structure; an Exchanger must touch both fuel and coolant
too few cells	Below a minimum count (fuel/vents/exchangers/coolant/plating/turbines)	Add the named cell type

See Building a Reactor.

The build looks connected but it still says the coolant dead-ends.

The capture geometry is there, but the coolant loop isn't hydraulically live to a Turbine — the exchangers' coolant doesn't trace all the way through to a turbine's coolant. Follow the loop cell by cell and close the gap. See Building a Reactor.

Output problems

My reactor runs fine but output plateaus / DC-per-hour is low.

You're capture-bottlenecked, not production-bottlenecked. Drive-Cell rate is capped by the smaller of your Exchanger capture capacity and your Turbine throughput — not by how hot the fuel runs. Adding fuel or throttle past the balance point just runs the core hotter without more output. Add Heat Exchangers (and the Turbines to convert what they pull). See Building a Reactor.

I pushed the throttle up but output barely moved.

Above the cruise balance point, production outruns capture: the extra heat piles into the fuel and toward the hull, not into the loop. You get a hotter core and faster burn for little extra output. Grow the capture chain instead of the throttle. See Operating a Reactor.

Breeding

I loaded fertile but nothing breeds. Why?

A burner breeds nothing by design. Breeding is geometry-gated: each fuel cell's breeding depends on its net packing = fuel neighbours − moderator neighbours. A packed, under-moderated fuel cube (net 3) breeds at full rate; a spread, well-moderated burner sits at or below the floor and breeds ~nothing. You need a distinct breeder build. See Breeding.

I have a breeder geometry and it still barely breeds.

Breeding also scales with flux — you have to run it hot. A breeder is under-moderated and attention-hungry; at a cold idle throttle the breed rate is near zero. Load Uranium-238 as fertile, pack the cube, and run it up (attended). See Breeding.

Pu-240 keeps climbing in the Fuel Port.

You're over-breeding. Bred Plutonium-239 left cooking under flux walks to Pu-240, a poison. Breeding is a harvest-timing skill: pull the Pu-239 sooner. Withdrawing the bred stock stops the walk. Pu-240 also leaves a spontaneous-fission floor that resists SCRAM, so withdraw the Pu-240 too to clean the core. See Breeding.

The core is misbehaving

Xenon reads ~25% and power is sagging after I dropped the throttle.

That's a xenon dead-time transient, not a fault. Drop power and iodine keeps decaying into Xe-135 faster than it burns off, so the poison spikes and power sags for a while, then recovers. Wait it out, or hold the throttle steady instead of chasing it. See Operating a Reactor.

My reactor is melting down. What do I do right now?

SCRAM — it dumps the core and slams the rods in. Then diagnose: you were over-throttled (production ran past capture + cooling), your vents were stripped or buried, or the coolant was starved. Add Heat Vents, restore the coolant loop, and back off to cruise. No reactor is meltdown-proof — the lethal ceiling is always there for the careless. See Operating a Reactor.

Do I have to babysit the reactor constantly?

No. Attention is event-driven — your throttle changes and alerts — never a constantly-draining meter. A burner at cruise is safe to leave; it holds itself via Doppler feedback. Only a pushed core or a breeder is attended-only. See Operating a Reactor.

The k gauge on the Console isn't sitting exactly at 1. Is that wrong?

No. In normal running the gauge shows the demand-follower deviation — how far the servo is from your throttle set-point — not a raw criticality eigenvalue. It reads honest criticality shifts (Doppler, xenon) on top. See Operating a Reactor.

Byproducts and waste

I withdrew Cs-137 (or Xe-135, Pu-240, etc.) and only got Nuclear Waste.

By design. You see every fission-product species live in the Fuel Port, but on withdrawal the produced byproducts consolidate into one generic Nuclear Waste item. Two isotopes (Pu-238, Am-241) are reserved as exempt, but nothing produces them yet — so the seven produced species are all unobtainable as distinct items. See Byproducts & Waste.

What do I do with Nuclear Waste?

Nuclear Waste is terminal — it doesn't feed back into the reactor and its uses are still to be defined. It's a sink, not a resource. See Byproducts & Waste.

What does a burnt-out fuel rod leave behind?

A spent rod is depleted uranium: a burned-out Fuel Assembly ejects Uranium-238 directly — no separate spent-fuel item, no reprocessing step. U-238 is the fertile stock for a breeder (you also get it as enrichment tailings). See Fuel & Isotopes.

Multiple reactors and scaling

Can I run more than one reactor per host?

No: one reactor per host. A second Console reads the same reactor. Scale a reactor by growing its cell counts (more fuel, exchangers, turbines, vents), not by building a second one. See Building a Reactor.

Does plating make my reactor meltdown-proof?

No. Plating raises the meltdown ceiling only modestly — the base ceiling stays the dominant term, so an enclosed shell doesn't balloon your safety margin. Plating is containment, not a cheat. Cool the core with vents, exchangers, and sane throttle. See Building a Reactor.