# Fission Reactor

The Fission Reactor is NeroPower's mid-game generator: a hollow cube of **Fission Casing** with a
**Fission Core** set into one wall, burning **Fuel Rods** that age as they burn. It is the first
machine that walks the [failure ladder](Failure-Stages.md), so it rewards an operator who watches
the heat and punishes one who does not. The core block on its own is **inert** — nothing happens
until you build it a shell.

## How it works

### Building a shell

Two sizes are valid — **3×3×3** and **5×5×5** (outer dimensions):

1. Build a hollow cube of **Fission Casing**.
2. Set the **Fission Core** into the **centre of one vertical wall**, facing outward. It replaces
   that casing position and counts as part of the shell.
3. Leave the interior **empty or filled only with Control Rod Assemblies** — any other block
   (including fluids) unforms the reactor.

The core re-checks its shell every two seconds and whenever a neighbouring block changes (the
larger size is tried first). It never loads chunks to do so: if part of the shell sits in an
unloaded chunk the reactor simply reads as *unformed* until the area is back. The GUI shows the
shell size once it forms; breaking any casing block unforms it and the core goes dark.

### Fuel rods and burn-up

The core has four rod slots, but only `shell size − 1` of them are usable: **two** in a 3×3×3 shell,
**all four** in a 5×5×5. Locked slots refuse everything. Only fresh **Fuel Rods** go in; a slot can
be pulled by hoppers or pipes only once its rod is spent.

Every loaded rod carries its **burn-up** (0–100 %) as item data, and every running tick advances
all loaded rods together. Output follows a curve over burn-up rather than a flat number:

| Burn-up | Output (of nominal) | Heat factor |
| --- | --- | --- |
| 0 % (fresh) | 120 % | 140 % |
| 20 % | 100 % | 120 % |
| 60 % | 80 % | 100 % |
| 100 % (spent) | 30 % | 50 % |

Between the knots the curve is linear. A fresh rod over-performs and runs hottest; a nearly spent
rod limps along. At 100 % the rod turns into a **Spent Fuel Rod** in its slot, ready for
reprocessing. The work bar in the GUI is the average burn-up of the loaded rods.

At the default rate a rod lasts about **104 minutes** on the Balanced preset. Overdrive and Speed
modules burn rods faster (and make more power while they do).

### Control rods

Every **Control Rod Assembly** you place *inside* the shell scales output **and** heat by
`1 − (assemblies × 15 %)`, down to a floor of **15 %**. They are the operator's throttle: a 3×3×3
shell holds one, a 5×5×5 up to 27. Fewer assemblies means more power and more heat.

### Neutron poisoning (the xenon pit)

Poison builds only while the core runs **hot**: it is producing, there is no failure-ladder
penalty, every usable slot is loaded, **and** the effective control-rod factor is above
`fissionPoisonRodThresholdPermille` (90 % by default). A core with no Control Rod Assembly runs at
100 %, so it builds poison at `fissionPoisonPerTick` (2) per tick. Once poison reaches
`fissionPoisonStallPermille` (90 %) the core **stalls**: no output, no burn-up, status *Xenon pit*.
It only restarts once the poison has decayed 30 points (300 ‰) below the line, so a core hovering
at the threshold cannot flicker on and off.

In every other case poison decays at `fissionPoisonDecayPerTick` (3) per tick: idle, stalled,
part-loaded, derated by the failure ladder, or control-rodded at or below the threshold. With the
defaults a single Control Rod Assembly (factor 85 %) is enough, and so is a SCRAM (15 %), so a core
with at least one control rod, or with one slot left empty, runs steadily without ever stalling.
The poison level is shown in the GUI.

### Heat, cooling and failure

The reactor pushes heat into NeroTech's thermal model exactly like a NeroTech machine: coolant
blocks, Radiators and Coolant Pumps next to the shell all help, and a
[Stirling Generator](RTG-and-Stirling.md) parked against it will draw heat *and* pay you for it.

Heat drives the [failure ladder](Failure-Stages.md). At **FAILURE** the shell explodes with a
radius of `shell size + 2` (5 or 7 blocks, before the server cap) and — if the server enables it —
leaves a **scorch zone** that hurts living creatures for a few real days.

### SCRAM

The NeroLink companion app offers a **SCRAM** action, and an *acknowledge alarm* action that clears
the alarm state. For 60 seconds after a SCRAM the core behaves as if every control rod were fully
inserted (the 15 % floor), whatever is actually inside the shell, so output and heat drop and the
ladder can climb back down.

Who may use them: if the reactor has a recorded owner (only when the server turned on NeroTech's
per-player attribution), only that owner, from anywhere. A reactor with no recorded owner (the
default) accepts them from any player who is online, in the reactor's dimension, within 128 blocks
of it, and allowed by the server's protection rules to use that block. The server checks this
itself on every request.

### Automation

- Energy leaves every face (Generator preset).
- Fuel Rods are accepted on every face; faces set to *output* in the Side Config tab let pipes
  pull **spent** rods only.
- The reactor is never load-shed by NeroTech's throttling.

## Recipes

| Item | Recipe |
| --- | --- |
| **Uranium Pellet** | 4 Glowstone Dust + 1 Iron Ingot (shapeless), or 2 Reprocessed Pellets |
| **Uranium Pellet** ×2 | 1 Raw Uranium — anything tagged `#c:raw_materials/uranium` (shapeless) |
| **Fuel Rod** | 3 Uranium Pellets in a row between two Iron Ingots |
| **Control Rod** | Iron Ingot, Redstone, Iron Ingot in a column |
| **Control Rod Assembly** | Control Rod, Iron Ingot, Control Rod in a row |
| **Fission Casing** (×4) | 8 Iron Ingots around a NeroTech Machine Frame |
| **Fission Core** | Iron Blocks in the corners, Circuit Boards top and bottom, Nero Coils on the sides, a Machine Frame in the middle |
| **Reprocessed Pellet** | a Spent Fuel Rod in NeroTech's **Chemical Processor** |
| **Reprocessed Pellet** ×2 | a Fuel Rod (fresh or partially burnt) in the **Chemical Processor** |

Spent Fuel Rods are never crafted — they come out of the reactor.

**Uranium source.** No mod in the Neroland ecosystem adds uranium ore yet. NeroPower declares the
`#c:raw_materials/uranium` tag (empty), so the raw-uranium recipe starts working as soon as another
mod you install puts its raw uranium in that common tag. Until then the glowstone recipe is the
fallback and the raw-uranium recipe simply cannot be crafted.

**Reprocessing yields.** A spent rod gives 1 Reprocessed Pellet. Pulling a rod early and
reprocessing it gives 2, whatever its burn-up, since the recipe cannot read how burnt the rod is.
That is more than a spent rod gives, but it is still a loss. Two Reprocessed Pellets make one
Uranium Pellet, so the 2 pellets from an early rod are worth 1 Uranium Pellet, against the 3 that
went into it.

## Config keys

All in `config/neropower.properties`; see [Configuration](Configuration.md) for the full list.

| Key | Default | What it does |
| --- | --- | --- |
| `fissionNePerRod` | 120 | Nominal NE/tick per fresh rod at 100 % of the curve |
| `fissionHeatPerRodPerTick` | 6 | Heat per rod per tick at 100 % heat factor |
| `fissionBurnupPerTick` | 8 | Burn-up per tick (permille ×1000) |
| `fissionBurnupCurve` | `0=1200,200=1000,600=800,1000=300` | The output curve knots |
| `fissionControlRodPermille` | 150 | Reduction per Control Rod Assembly |
| `fissionPoisonPerTick` | 2 | Poison gained per tick while the core runs hot |
| `fissionPoisonRodThresholdPermille` | 900 | Poison builds only above this control-rod factor |
| `fissionPoisonDecayPerTick` | 3 | Poison shed per tick otherwise |
| `fissionPoisonStallPermille` | 900 | Poison level that stalls the core |
| `fissionScorchEnabled` | false | Leave a scorch zone on failure |
| `fissionScorchDays` | 3 | Real days a scorch zone lasts |
| `fissionScorchRadius` | 6 | Half-edge of the scorch cube |