PHYSICS OF NUCLEAR WEAPONS

Nuclear Binding Energy

Nuclear Stability

Weapon Types Fission

“Little Boy”

“Fat Man”

Weapon Size

Nuclear Weapons & States

The Fission Reaction 200 MeV/240 ≈ 0.8 MeV/nucleon ≈ 1,000,000 X E chemical

Weapon Types Fusion

Two-Stage Thermonuclear

The Fusion Reaction 17.6 MeV/5 ≈ 3.5 MeV/nucleon ≈ 5 X E fission

Comparison of Fission & Fusion Nuclear FissionNuclear Fusion Definition: Fission is the splitting of a large atom into two or more smaller ones. Fusion is the fusing of two or more lighter atoms into a larger one. Natural occurrence of the process: Fission reaction does not normally occur in nature. Fusion occurs in stars, such as the sun. Byproducts of the reaction: Fission produces many highly radioactive particles. Few radioactive particles are produced by fusion reaction, but if a fission "trigger" is used, radioactive particles will result from that. Conditions: Critical mass of the substance and high- speed neutrons are required. High density, high temperature environment is required. Energy Requirement: Takes little energy to split two atoms in a fission reaction. Extremely high energy is required to bring two or more protons close enough that nuclear forces overcome their electrostatic repulsion. Energy Released: The energy released by fission is a million times greater than that released in chemical reactions; but lower than the energy released by nuclear fusion. The energy released by fusion is three to four times greater than the energy released by fission. Nuclear weapon: One class of nuclear weapon is a fission bomb, also known as an atomic bomb or atom bomb. One class of nuclear weapon is the hydrogen bomb, which uses a fission reaction to "trigger" a fusion reaction.

Paths to Fissionable Material

Nuclear Fuel - Uranium Ore → Yellow Cake → Enriched

Uranium Deposits

Uranium Enrichment Slightly Enriched (SEU): 0.9%-2.0% Used in Heavy-Water Reactors (HWR) Low-Enriched (LEU): 2%-20% 3%-5% used in Light-Water Reactors (LWR) 12%-19.75% used in Research Reactors Highly Enriched (HEU): >20% ≥ 85% used in weapons primaries ≥ 20% ‘weapons-usable’ in implosion designs 40%-80% used in secondary of two-stage ≥ 20% used in fast neutron reactors 50%-90% used in naval reactors 26.5% in commercial fast reactors

Critical Mass

Critical Masses TABLE A-1 Properties of Nuclear-Explosive Nuclides Isotope or Mixture Critical Mass (kg) Half Life (years) Decay Heat (watts/kg) Neutron Production From Spontaneous Fission (per kg-sec) Main Gamma Energies (MeV) U , from Tl- 208 U ,000, Np ,100, Pu ,700, Pu , Pu , ,000, Pu from Am- 241 Pu , ,700, Am ,

Comparison of Energy Content Fission of U-233: 17.8 kt/kg Fission of U-235: 17.6 kt/kg Fission of Pu-239: 17.3 kt/kg Fusion of pure deuterium: 82.2 kt/kg Fusion of tritium and deuterium (50/50): 80.4 kt/kg Fusion of lithium-6 deuteride: 64.0 kt/kg Fusion of lithium-7 deuteride: Total conversion of matter to energy: Mt/kg Fission of 1.11 g U-235: 1 megawatt-day (thermal) Broader comparison of Energy Densities

Enrichment Process

Uranium

UF 6

Enrichment Methods Electromagnetic (Calutron) (≤ 15% enrichment)

Enrichment Methods Gaseous Diffusion

Enrichment Timeline

Enrichment Methods Thermal Diffusion

Enrichment Methods Gas Centrifuge

Centrifuges Materials: Aluminum → Maraging Steel → Carbon Fiber Composite 100,000 rpm (balanced, magnetic bearings) STUXNET

Enrichment Methods LASER Techniques (AVLIS/MLIS)

Method Comparison

Resources IAEA/INFCIS The Atomic Archive World Nuclear Association Nuclear Chemistry Federation of American Scientists Nuclear Pathways ALSOS Digital Library Nuclear Safeguards Education Portal World Information Service on Energy (WISE) Uranium Project