Nuclear Physics

_{Focus Areas · Design document §3}

Available from: CH06 + MA05 (Corpuscular/atomic worlds only — in Elemental worlds this focus never coheres; see Quintessic Physics for the niche equivalent)

20 breakthroughs — CORE 3 · STANDARD 13 · UNCOMMON 1 · RARE 3 — Modern – Space

Builds on: Mining (1) · Mathematics (1) · Thermodynamics (1) · Chemistry (1) · Optics (1) · Electricity (5) · Electronics (1) · Quantum Physics (3) · Rocketry (1) · Materials Science (1) · Energy Systems (4)

Leads into: Seafaring (1) · Quantum Physics (1) · Rocketry (4) · Space Engineering (2) · Energy Systems (3)

_{The numbers count prerequisite links between this focus and the other. How to read the tables.}

Overview

ID	Breakthrough	Tier	Era	Prerequisites
NP01	Radioactivity	CORE	Modern	CH06 (Periodic Table) + OP08 (Spectroscopy) + MI05 (Deep Shaft Mining)
NP02	Atomic Model	CORE	Modern	NP01 + MA05 + EL03
NP03	Nuclear Fission	CORE	Atomic	NP02
NP04	Nuclear Fusion	STANDARD	Atomic	NP02 + TH01 + EL11 (Superconductivity)
NP05	Nuclear Weapons	STANDARD	Atomic	NP03
NP06	Thermonuclear Weapon	STANDARD	Atomic	NP05 + NP04
NP07	Breeder Reactor	UNCOMMON	Atomic	NP03
NP08	Thorium Reactor	STANDARD	Atomic	NP03 (Nuclear Fission)
NP09	Compact Fusion	RARE	Space	NP04 + MS01 + EL12 (Room Temp Superconductor) — cost ×4
NP10	Cold Fusion	RARE	Atomic	NP02 + EL02 (Voltaic Pile — electrochemistry)
NP11	Antimatter Production	STANDARD	Space	(NP04 or NP03) + QP04 (Particle Accelerator) — cost ×2.5
NP15	Superconducting Storage Rings	STANDARD	Space	EL11 + (ES06 or ES14 or ES08) — cost ×2.5
NP12	Particle Laboratories	STANDARD	Space	NP02 + QP04 — cost ×2.5
NP13	Hardened Shelters	STANDARD	Space	NP12 — cost ×2.5
NP16	Particle-Beam Weapons	STANDARD	Space	NP15 — cost ×2.5
NP17	Particle-Beam Artillery	STANDARD	Space	NP16 + NP13 — cost ×4

The Fission Deep Path

ID	Breakthrough	Tier	Era	Prerequisites
NP-F01	Advanced Fuel Cycles	STANDARD	Atomic	NP07 (Breeder Reactor) + (NP08 Thorium Reactor, or ES06 Nuclear Fission Plant)
NP-F02	Micro-Fission Reactors	STANDARD	Atomic	NP-F01 + EN10 (Miniaturization)
NP-F03	Fission Fragment Propulsion	STANDARD	Space	NP-F01 + RK02 (Liquid Fuel Rocket) — cost ×2.5
NP-F04	Quantum Fission Cascade	RARE	Space	NP-F02 + QP02 (Quantum Mechanics) — cost ×4

Prerequisite map

flowchart LR
  n_NP01["NP01 Radioactivity"]:::CORE
  n_NP02["NP02 Atomic Model"]:::CORE
  n_NP03["NP03 Nuclear Fission"]:::CORE
  n_NP05["NP05 Nuclear Weapons"]:::STANDARD
  n_NP06["NP06 Thermonuclear Weapon"]:::STANDARD
  n_NP07["NP07 Breeder Reactor"]:::UNCOMMON
  n_NP_F01["NP-F01 Advanced Fuel Cycles"]:::STANDARD
  n_NP_F02["NP-F02 Micro-Fission Reactors"]:::STANDARD
  n_NP_F04["NP-F04 Quantum Fission Cascade"]:::RARE
  n_NP_F03["NP-F03 Fission Fragment Propulsion"]:::STANDARD
  n_NP08["NP08 Thorium Reactor"]:::STANDARD
  n_NP11["NP11 Antimatter Production"]:::STANDARD
  n_NP04["NP04 Nuclear Fusion"]:::STANDARD
  n_NP09["NP09 Compact Fusion"]:::RARE
  n_NP10["NP10 Cold Fusion"]:::RARE
  n_NP12["NP12 Particle Laboratories"]:::STANDARD
  n_NP13["NP13 Hardened Shelters"]:::STANDARD
  n_NP17["NP17 Particle-Beam Artillery"]:::STANDARD
  n_NP15["NP15 Superconducting Storage Rings"]:::STANDARD
  n_NP16["NP16 Particle-Beam Weapons"]:::STANDARD
  n_NP01 --> n_NP02
  n_NP02 --> n_NP03
  n_NP02 --> n_NP04
  n_NP03 --> n_NP05
  n_NP05 --> n_NP06
  n_NP04 --> n_NP06
  n_NP03 --> n_NP07
  n_NP03 --> n_NP08
  n_NP04 --> n_NP09
  n_NP02 --> n_NP10
  n_NP04 -.-> n_NP11
  n_NP03 -.-> n_NP11
  n_NP02 --> n_NP12
  n_NP12 --> n_NP13
  n_NP15 --> n_NP16
  n_NP16 --> n_NP17
  n_NP13 --> n_NP17
  n_NP07 --> n_NP_F01
  n_NP08 -.-> n_NP_F01
  n_NP_F01 --> n_NP_F02
  n_NP_F01 --> n_NP_F03
  n_NP_F02 --> n_NP_F04
  classDef CORE fill:#dbeafe,stroke:#1d4ed8,color:#0b1b3b
  classDef STANDARD fill:#f1f5f9,stroke:#64748b,color:#0f172a
  classDef UNCOMMON fill:#dcfce7,stroke:#15803d,color:#052e16
  classDef RARE fill:#fef3c7,stroke:#b45309,color:#3b2005
  classDef UNIQUE fill:#fae8ff,stroke:#a21caf,color:#3b0a3f

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_{Prerequisites within this focus. Box colour is the tier (blue CORE, grey STANDARD, green UNCOMMON, amber RARE, purple UNIQUE); dotted arrows are alternatives (“or”); a line can pass behind another box, so follow it from its start. 12 of these 20 breakthroughs also need breakthroughs from other foci, which the overview above lists.}

Breakthroughs

NP01 · Radioactivity

• Tier: CORE · Era: Modern
• Prerequisites: CH06 (Periodic Table) + OP08 (Spectroscopy) + MI05 (Deep Shaft Mining)
• Unlocks: Reveals Uranium (the canonical Atomic Theory revealedBy); ⟨[+1 Gold] from [Uranium] tiles [in all cities]⟩ — radium, the costliest substance on Earth. Uranium Discovery merged here in v3.124. Atomic worlds only.
• Leads to: NP02 Atomic Model, SE03 Radiation Shielding

NP02 · Atomic Model

• Tier: CORE · Era: Modern
• Prerequisites: NP01 + MA05 + EL03
• Unlocks: Nuclear Physics Labⁿ [250/1; requires a Research Lab in this city; +2 Science; Great Scientist points 2]; grants HIGH_ENERGY_PHYSICS. The atom has parts.
• Leads to: NP03 Nuclear Fission, NP04 Nuclear Fusion, NP10 Cold Fusion, NP12 Particle Laboratories, QP01 Wave-Particle Duality

NP03 · Nuclear Fission

• Tier: CORE · Era: Atomic
• Prerequisites: NP02
• Unlocks: ⟨Reveal up to [all] [Uranium] within a [20] tile radius⟩ (a Triggerable on discovery — prospectors know what to look for). Prerequisite for Nuclear Weapons (NP05), the Nuclear Plant (ES06) and the fission-path chain. Atomic worlds only — the familiar reactor, familiar in every way.
• Leads to: SF14 Nuclear Submarine, NP05 Nuclear Weapons, NP07 Breeder Reactor, NP08 Thorium Reactor, NP11 Antimatter Production, RK08 Nuclear Thermal Rocket, ES06 Nuclear Fission Plant

NP04 · Nuclear Fusion

• Tier: STANDARD · Era: Atomic
• Prerequisites: NP02 + TH01 + EL11 (Superconductivity)
• Unlocks: The clean, abundant path — prerequisite for the Fusion Reactor (ES08). Dead-ends in FQ2-Impossible worlds (~25%) and underperforms in FQ2-Marginal ones (~15%); when it fails, the Fission Deep Path (NP-F01–04) is the way forward, and the fissile economy becomes the atomic world's whole energy story.
• Leads to: NP06 Thermonuclear Weapon, NP09 Compact Fusion, NP11 Antimatter Production, RK10 Fusion Drive, RK14 Bussard Ramjet, ES08 Fusion Reactor

NP05 · Nuclear Weapons

• Tier: STANDARD · Era: Atomic
• Prerequisites: NP03
• Unlocks: Manhattan Project (national wonder — the canonical enabler); Atomic Bomb (unit; requires Uranium; <when nuclear weapons are enabled>). Deterrence is no mechanic — the bombs simply exist, as in the base game.
• Leads to: NP06 Thermonuclear Weapon, RK13 Orion Nuclear Pulse, SE13 Planetary Defense

NP06 · Thermonuclear Weapon

• Tier: STANDARD · Era: Atomic
• Prerequisites: NP05 + NP04
• Unlocks: Nuclear Missile (unit; requires Uranium). Requires Fusion (NP04): in FQ2-Impossible worlds the hydrogen bomb never comes, and the fission bomb is the ceiling.
• Notes: Requires Nuclear Fusion (NP04), which dead-ends in FQ2-Impossible worlds.

NP07 · Breeder Reactor

• Tier: UNCOMMON · Era: Atomic
• Prerequisites: NP03
• Unlocks: ⟨[+100]% [Uranium] resource production⟩ — the Arabian-Oil pattern: a reactor that makes more fuel than it burns doubles what every deposit yields.
• Leads to: NP-F01 Advanced Fuel Cycles

NP08 · Thorium Reactor

• Tier: STANDARD · Era: Atomic
• Prerequisites: NP03 (Nuclear Fission)
• Unlocks: Thorium Reactorⁿ [625/3; requires a Factory in this city; +4 Production; ⟨[+10]% [Production] [in this city]⟩; needs no Uranium; ⟨Remove [{Power Plant} {non-[Thorium Reactor]}] [in this city]⟩ — a grid plant: ⟨Power Plant⟩ (tag)] — the route for the uranium-poor, and the safer one. (Civ V has no Thorium resource; the breakthrough itself is the gate.) Competing Solution (§1.2): the alternative to Nuclear Fission Plant (ES06), detour margin ×1.5 while Nuclear Fission Plant exists in this world; if Nuclear Fission Plant is discovered first this is never developed, and if it arrives later this persists — it needs no Uranium and cannot melt down.
• Leads to: NP-F01 Advanced Fuel Cycles

NP09 · Compact Fusion

• Tier: RARE · Era: Space
• Prerequisites: NP04 + MS01 + EL12 (Room Temp Superconductor) — cost ×4
• Unlocks: Compact Fusion Plantⁿ [a grid plant: ⟨Power Plant⟩ (tag); ⟨Remove [{Power Plant} {non-[Compact Fusion Plant]}] [in this city]⟩; 1125/6; requires a Factory in this city; +8 Production; ⟨[+15]% [Production] [in this city]⟩]; ⟨[+1] Movement <for [Water] units>⟩ (fusion-powered hulls). Requires the Room-Temperature Superconductor (EL12).
• Notes: W18 — Capstone B, rare (where fusion works).

NP10 · Cold Fusion

• Tier: RARE · Era: Atomic
• Prerequisites: NP02 + EL02 (Voltaic Pile — electrochemistry)
• Unlocks: Cold Fusion Cellⁿ [625/3; +3 Production; +2 Happiness — clean, distributed, and needing no fuel]. Extremely hard to reach: deep investment in both Nuclear Physics and Electrochemistry.
• Notes: Speculative.

NP11 · Antimatter Production

• Tier: STANDARD · Era: Space
• Prerequisites: (NP04 or NP03) + QP04 (Particle Accelerator) — cost ×2.5
• Unlocks: ⟨Triggers a [Antimatter in Bulk] event⟩ on discovery — the Science Advisor reports that antimatter can be made and held, and the physicists turn to exotic matter. Prerequisite for Exotic Matter Synthesis (QP11).
• Notes: W18 — Pool (left Tachyonic's build in balance round two).

NP15 · Superconducting Storage Rings

• Tier: STANDARD · Era: Space
• Prerequisites: EL11 + (ES06 or ES14 or ES08) — cost ×2.5
• Unlocks: ⟨[+15]% [Science] <in cities with a [Nuclear Physics Lab]>⟩ — antimatter is held in magnetic traps and storage rings, and the converter ring is one at ship scale.
• Notes: W18 — Pool; Tachyonic engineering — the converter ring (atomic worlds).
• Leads to: NP16 Particle-Beam Weapons

NP12 · Particle Laboratories

• Tier: STANDARD · Era: Space
• Prerequisites: NP02 + QP04 — cost ×2.5
• Unlocks: ⟨[+15]% Great Person generation [in all cities]⟩ — accelerator laboratories as a home for big science.
• Notes: W18 — Entry: opens the pool.
• Leads to: NP13 Hardened Shelters

NP13 · Hardened Shelters

• Tier: STANDARD · Era: Space
• Prerequisites: NP12 — cost ×2.5
• Unlocks: ⟨Population loss from nuclear attacks [-50]% [in all cities]⟩, ⟨Damage to garrison from nuclear attacks [-50]% [in all cities]⟩; fallback ⟨[+15]% Strength for cities <when nuclear weapons are disabled>⟩.
• Notes: W18 — Pool.
• Leads to: NP17 Particle-Beam Artillery

NP16 · Particle-Beam Weapons

• Tier: STANDARD · Era: Space
• Prerequisites: NP15 — cost ×2.5
• Unlocks: ⟨[+20]% Strength <for [Siege] units>⟩ — beams strike; lasers (Optics) defend.
• Notes: W18 — First step of capstone A.
• Leads to: NP17 Particle-Beam Artillery

NP17 · Particle-Beam Artillery

• Tier: STANDARD · Era: Space
• Prerequisites: NP16 + NP13 — cost ×4
• Unlocks: Particle Beam Cannonⁿ [unit, Siege; statistics set at spec; a long-range siege unit].
• Notes: W18 — Capstone A.

The Fission Deep Path

The deep fission path represents what happens when a civilisation pushes fission technology to its limits rather than pivoting to fusion. NP-F01 is the gateway — the alternative in a Competing Solutions group whose primary is Nuclear Fusion (NP04). Discover fusion first and the deep fission path is never developed; reach advanced fuel cycles first and the chain opens and persists — its micro-reactors and endurance remain worth having after fusion arrives. But a civilisation that invests heavily in breeder reactors and thorium before fusion arrives may discover advanced fuel cycles — and from there, the rest of the chain follows. In FQ2-Impossible worlds Nuclear Fusion dead-ends — a dead-ended breakthrough obsoletes nothing — so the deep fission path can never be obsoleted.

NP-F01 · Advanced Fuel Cycles

• Tier: STANDARD · Era: Atomic
• Prerequisites: NP07 (Breeder Reactor) + (NP08 Thorium Reactor, or ES06 Nuclear Fission Plant)
• Unlocks: ⟨[+50]% [Uranium] resource production⟩ (fuel from seawater). Competing Solution (§1.2): the alternative to Nuclear Fusion (NP04), detour margin ×1.5 while Nuclear Fusion exists in this world; if Nuclear Fusion is discovered first this is never developed, and if it arrives later this persists — the deep fission chain it opens keeps its micro-reactors and endurance.
• Notes: Gateway to the deep fission chain.
• Leads to: NP-F02 Micro-Fission Reactors, NP-F03 Fission Fragment Propulsion, ES14 Advanced Fission

NP-F02 · Micro-Fission Reactors

• Tier: STANDARD · Era: Atomic
• Prerequisites: NP-F01 + EN10 (Miniaturization)
• Unlocks: Micro-Reactorⁿ [500/3; requires a Factory in this city; +3 Production; ⟨[+10]% [Production] [in this city]⟩; requires Uranium; ⟨Remove [{Power Plant} {non-[Micro-Reactor]}] [in this city]⟩ — a grid plant: ⟨Power Plant⟩ (tag) — power for the town that cannot afford the plant]; ⟨[+1] Movement <for [Armored] units>⟩ (reactors small enough for a hull). Fusion civilisations never build these.
• Leads to: NP-F04 Quantum Fission Cascade

NP-F03 · Fission Fragment Propulsion

• Tier: STANDARD · Era: Space
• Prerequisites: NP-F01 + RK02 (Liquid Fuel Rocket) — cost ×2.5
• Unlocks: ⟨Propulsion⟩ (tag), counted toward the Boosters' propulsion by Orbital Mechanics (RK04) — the fission-fragment drive: more efficient than chemistry, longer-lived than fusion. The no-fusion road to the stars.
• Notes: W18 — Pool. The no-fusion path to deep space.

NP-F04 · Quantum Fission Cascade

• Tier: RARE · Era: Space
• Prerequisites: NP-F02 + QP02 (Quantum Mechanics) — cost ×4
• Unlocks: Cascade Reactorⁿ [a grid plant: ⟨Power Plant⟩ (tag); ⟨Remove [{Power Plant} {non-[Cascade Reactor]}] [in this city]⟩; 1125/6; requires a Factory in this city; +8 Production; ⟨[+15]% [Production] [in this city]⟩; requires Uranium — approaching fusion's density with fission's fuel]. The endgame energy of a fission-path civilisation.
• Notes: W18 — Capstone B, rare (the fission road).