Plutonium
Overview
Plutonium is a radioactive, man-made element that serves as the primary fissile material in nuclear weapons and nuclear reactors. Created in nuclear reactors through neutron bombardment of uranium-238, plutonium-239 can sustain nuclear chain reactions with smaller critical masses than uranium-235.
Physical Properties
Plutonium exhibits unique characteristics:
- Atomic number: 94 (94 protons)
- Density: 19.8 g/cm³ (very dense metal)
- Melting point: 640°C (1,184°F)
- Appearance: Silvery metal that tarnishes to olive green
- Isotopes: Multiple isotopes, with Pu-239 most important for weapons
Production Methods
Plutonium is produced artificially through nuclear processes:
- Reactor production: Uranium-238 captures neutrons to become Pu-239
- Chemical separation: Plutonium extracted from irradiated uranium fuel
- Weapons-grade: Requires high concentration of Pu-239 isotope
- Reactor-grade: Contains higher percentages of other plutonium isotopes
Toxicity and Health Effects
Plutonium poses severe health risks:
- Alpha radiation: Emits alpha particles that damage tissue
- Inhalation hazard: Most dangerous when inhaled as particles
- Bone and liver: Accumulates in bones and liver tissue
- Cancer risk: Causes lung, bone, and liver cancers
- External safety: Alpha radiation cannot penetrate skin
Nuclear Weapons Applications
Plutonium enables compact nuclear weapons:
- Critical mass: Only 4-6 kg needed for weapons (vs. 15-20 kg uranium)
- Implosion design: Fat Man bomb used plutonium implosion
- Weapon efficiency: Higher yield per unit mass than uranium
- Proliferation concern: Easier to weaponize than uranium-235
Nuclear Power Applications
Plutonium has civilian nuclear uses:
- Breeder reactors: Create more fuel than they consume
- MOX fuel: Mixed oxide fuel combines plutonium with uranium
- Energy potential: Can provide thousands of years of energy
- Fuel recycling: Extracted from spent nuclear fuel
Environmental Impact
Plutonium contamination affects large areas:
- Hanford site: 54 million gallons of radioactive waste
- Rocky Flats: Contaminated soil around former weapons plant
- Marshall Islands: Fallout from nuclear testing
- Mayak facility: Severe contamination in Russia
Global Stockpiles
Worldwide plutonium inventories present security challenges:
- Total stocks: Over 500 tons of separated plutonium
- Weapons material: Enough for 100,000+ nuclear weapons
- Civilian stocks: Japan holds 47 tons for reactor programs
- Security concerns: Theft and terrorism risks
Relevance to Nuclear Weapons
Plutonium is crucial to nuclear weapons because:
- Lower critical mass enables smaller, more efficient weapons
- Produced in nuclear reactors, making it accessible to many nations
- Dual-use nature creates proliferation risks in civilian programs
- Long half-life (24,000 years) creates lasting security challenges
Sources
Authoritative Sources:
- Lawrence Berkeley National Laboratory - Plutonium discovery and research history
- International Atomic Energy Agency - Plutonium safeguards and security
- Nuclear Threat Initiative - Plutonium proliferation risks and management
- U.S. Department of Energy - Plutonium production history and cleanup efforts
- World Nuclear Association - Plutonium in nuclear fuel cycles