Nuclear Radiation

Physics-driven radiation for Minecraft — real isotopes, real decay, real dose. No hand-wavy "rad" bar.

Drop a chunk of spent fuel and it's genuinely deadly. Hide behind lead, concrete, or a hazmat suit and they actually shield you. Get dosed, and the right medicine can pull you back from the edge.

• Modpacker Guide - no-code setup (datapack JSON, KubeJS, config). FAQ: make blocks/items radioactive, biome/dimension background, block & armor shielding, isotopes, mutations, block irradiation.
• Mod Developer Guide - Java API: radiation sources, profiles, bindings, shielding, isotopes, dose sampling, and the NREvents integration bridge.
• KubeJS Guide - full scripting reference.

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What makes it different

Most radiation mods use a single abstract "rad" number. Nuclear Radiation models the real chain:

Source activity (Bq) → radiation field → shielding attenuation → biological dose (Sv)

Every step uses correct physics units and real-world behavior:

• Becquerel (Bq) - how active a source is (decays per second)
• Gray (Gy) - absorbed dose, used for shielding math
• Sievert (Sv) - the biological dose you accumulate (live rate + lifetime total)

Different radiation types behave differently, with proper quality factors:

• Alpha - deadly up close, stopped by almost anything (Q=20)
• Beta - moderate range (Q=1)
• Gamma / X-ray - penetrating, needs dense shielding (Q=1)
• Neutron - penetrating and nasty (Q≈10)

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Features

Radiation that comes from real things

• Placed radioactive blocks emit into the world
• Block irradiation - radiation sources (blocks, dropped items, fluids) irradiate nearby blocks, with a chance for blocks to change
• Dropped radioactive item stacks become hot spots on the ground - with a visible radioactive glow so you know what's dangerous before you touch it
• Radioactive fluids irradiate their surroundings
• Chests and barrels full of hot material leak radiation (sealed = point source, no contamination spread)
• Chunks track soil / air / water contamination over time

Real decay

• Built-in isotopes (40+): U-233, U-234, U-235, U-238, Pu-238, Pu-239, Pu-241, Pu-242, Cs-137, I-131, Sr-90, Y-90, Co-60, Cf-249, Cf-250, Cf-251, Cf-252, H-3, Po-210, Xe-133, Kr-85, Th-230, Th-232, Np-236, Np-237, Am-241, Am-242, Am-243, Cm-243, Cm-245, Cm-246, Cm-247, Bk-247, Bk-248, Na-22, Ca-48, Be-7, Ir-192, Ac-225, Cn-291

• Isotopes actually decay over time based on their real half-lives

• Decay chains with daughter products (e.g. Pu-239 → U-235, Sr-90 → Y-90)

• Short-lived isotopes burn out; long-lived ones stay hot for the long haul

Shielding that works like shielding

• Stand behind stone, iron, gold, water, obsidian, or netherite and it actually blocks radiation
• Dense materials block more - proper Beer–Lambert attenuation, traced block-by-block between source and you
• Different materials block X-ray and neutron radiation by different amounts
• Armor protects you - full iron/gold/netherite sets reduce incoming dose, configurable per radiation type

Exposure that's more than standing near it

• External dose from the radiation field around you
• Inventory dose - carrying a hot item in your hotbar, offhand, or pockets exposes you; armor slots shield more
• Internal dose from ingested or inhaled isotopes - and it stays in you
• Background radiation per dimension and per biome
• White noise overlay in highly radioactive areas - the more intense the field, the heavier the static on your screen
• Mob mutations - prolonged radiation exposure causes mobs to mutate

Tools & Protection

• Geiger Counter - reads live activity (Bq) in the world; clicks faster the hotter it gets
• Dosimeter - your personal dose readout: total Sv, current Sv/h, and a breakdown of external / inventory / internal sources, with an on-screen HUD
• Hazmat Suit - full-body protective gear that significantly reduces external dose and blocks contamination; essential for working in hot zones

Medicine

Exposure is survivable if you treat it:

• Iodine Pill - blocks I-131 from being taken up by your body
• Prussian Blue - flushes out Cesium-137
• Anti-Rad Injection - strong emergency purge
• Radaway - gradual cleanup over time
• Rad-Protection Potion - general resistance to incoming dose

One radiation system for all

• Unify radiation systems from different mods into single
• Mekanism - ✅
• NuclearCraft: Neohaul - ✅
• Create: Creating Space - ✅
• Hbm's Nuclear Tech: Neo Edition - ❔it's in alpha
• Industrial Upgrade - ❔later
• Nuclear Science - ✅
• Alex's Caves - ❔no 1.21.1 version yet

For map makers & modpack authors

• KubeJs support - kubejs
• Creative Radiation Source block - place a fully tunable emitter, dial in Alpha / Beta / X-Ray / Neutron output in MBq
• Fully data-driven - assign radioactivity to any item, block, or fluid (yours or another mod's) via datapack JSON, tags, or per-stack data components
• Armor shielding values are datapack-driven too
• Deeply configurable: sim intervals, dose thresholds, recovery rates, contamination spread, background levels, and more

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Recipe-viewer support

Full JEI and EMI integration with custom info pages:

• Isotope Stats - half-life, radiation mix, quality factors, decay products
• Radioactive Items - what's hot and how hot
• Decay Graph - visual decay chains
• Armor Radiation Protection - shielding values per armor piece

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Getting started

1. Craft or grab a Geiger Counter and Dosimeter (Tools & Utilities creative tab)
2. Go find something radioactive - the Geiger counter will tell you when you're close
3. Watch your Dosimeter. Keep your total Sv down
4. Put dense blocks (or distance) between you and the source
5. Wear protective armor or hazmat when working near hot material
6. Keep iodine pills and Radaway on hand for when things go wrong

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Requirements

• Minecraft 1.21.1
• NeoForge 21.1.230+
• Java 21

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Performance

Built to run on real servers. The simulation runs on a dedicated background thread, uses a spatial radiation-field cache so cost scales with entities rather than entities × sources, has a hard radius cutoff on sources, and gates world/entity simulation on separate, configurable tick intervals. No off-thread world access.

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Real units. Real decay. Real consequences.

License: MIT