⚛️Intro to Applied Nuclear Physics Unit 12 – Nuclear Weapons & Nonproliferation

Key Concepts and Terminology

• Nuclear weapons release massive amounts of energy through fission, fusion, or a combination of both processes
• Fissile materials (uranium-235, plutonium-239) are essential for creating nuclear weapons
• Enrichment increases the concentration of fissile isotopes in a material
  • Uranium enrichment typically uses gas centrifuges or gaseous diffusion
  • Plutonium is produced in nuclear reactors and separated through reprocessing
• Critical mass is the minimum amount of fissile material needed to sustain a nuclear chain reaction
• Yield refers to the explosive energy released by a nuclear weapon, measured in kilotons (kt) or megatons (Mt) of TNT equivalent
• Deterrence theory suggests that the threat of nuclear retaliation prevents conflicts between nuclear-armed states
• Nonproliferation aims to prevent the spread of nuclear weapons to additional states or non-state actors

Historical Context of Nuclear Weapons

• Nuclear weapons were first developed during World War II as part of the Manhattan Project
• The United States conducted the first nuclear test, Trinity, on July 16, 1945, in New Mexico
• Atomic bombs were dropped on Hiroshima (Little Boy, uranium-based) and Nagasaki (Fat Man, plutonium-based) in August 1945
• The Soviet Union conducted its first nuclear test in 1949, leading to the Cold War arms race
• Other nations that have developed nuclear weapons include the United Kingdom (1952), France (1960), China (1964), India (1974), Pakistan (1998), and North Korea (2006)
• The Cuban Missile Crisis in 1962 brought the world to the brink of nuclear war
• The end of the Cold War in 1991 led to a reduction in nuclear stockpiles, but proliferation concerns persist

Nuclear Fission and Fusion Basics

• Nuclear fission occurs when a heavy atomic nucleus (uranium-235, plutonium-239) splits into lighter nuclei
  • Fission releases neutrons, which can trigger a chain reaction if enough fissile material is present
  • Fission reactions are used in nuclear power plants and fission weapons
• Nuclear fusion combines light atomic nuclei (hydrogen isotopes) to form a heavier nucleus, releasing energy
  • Fusion reactions power the sun and other stars
  • Fusion weapons (thermonuclear weapons) use fission to trigger fusion reactions for increased yield
• Fission and fusion reactions release energy according to Einstein's equation: $E=mc^2$
• Binding energy is the energy required to disassemble a nucleus into its constituent protons and neutrons
  • Fission and fusion reactions convert some of the binding energy into kinetic energy of the reaction products

Types of Nuclear Weapons

• Fission weapons (atomic bombs) rely on nuclear fission chain reactions
  • Gun-type design (Little Boy) uses conventional explosives to fire one subcritical piece of fissile material into another
  • Implosion design (Fat Man) uses explosives to compress a subcritical sphere of fissile material into a critical configuration
• Boosted fission weapons use a small amount of fusion fuel (deuterium-tritium) to increase the yield and efficiency of fission reactions
• Fusion weapons (thermonuclear weapons, hydrogen bombs) use fission to trigger fusion reactions
  • Staged design (Teller-Ulam) uses a fission primary to compress and heat a fusion secondary, which further compresses the primary
  • Fusion reactions can be boosted with additional fissile material for increased yield
• Enhanced radiation weapons (neutron bombs) are designed to release a higher proportion of their energy as neutron radiation
• Dirty bombs combine conventional explosives with radioactive material to spread contamination, but do not involve a nuclear explosion

Nuclear Weapon Design and Effects

• Nuclear weapon design involves the arrangement of fissile material, conventional explosives, and other components
  • Efficient design maximizes yield while minimizing size and weight
  • Safety features prevent accidental detonation and unauthorized use
• The effects of a nuclear explosion include blast, thermal radiation, ionizing radiation, and electromagnetic pulse (EMP)
  • Blast creates a shock wave that can destroy structures and cause injuries
  • Thermal radiation causes burns, fires, and eye damage
  • Ionizing radiation (gamma rays, neutrons) can cause acute radiation sickness and long-term health effects
  • EMP can disrupt electronic devices and power grids
• Fallout is the radioactive material that settles to the ground after a nuclear explosion
  • Fallout can contaminate air, water, and soil, leading to health risks and environmental damage
• The severity of nuclear weapon effects depends on factors such as yield, height of burst, and local conditions (terrain, weather)

Nuclear Proliferation Challenges

• Horizontal proliferation refers to the spread of nuclear weapons to additional states
  • States may seek nuclear weapons for security, prestige, or domestic political reasons
  • Proliferation can destabilize regions and increase the risk of nuclear conflict
• Vertical proliferation involves the expansion of existing nuclear arsenals
  • States may seek to improve the quantity, quality, or diversity of their nuclear weapons
• Non-state actors (terrorist groups) may attempt to acquire nuclear weapons or materials
  • Nuclear terrorism could involve the use of a stolen or improvised nuclear device
• Dual-use technologies (enrichment, reprocessing) can be used for both peaceful and military purposes
  • The spread of dual-use technologies can enable proliferation under the guise of civilian programs
• Nuclear latency refers to a state's ability to quickly develop nuclear weapons based on its technological capabilities
  • States with advanced nuclear infrastructure (reactors, enrichment facilities) may be considered latent nuclear powers

Nonproliferation Treaties and Agreements

• The Nuclear Non-Proliferation Treaty (NPT) is the cornerstone of the global nonproliferation regime
  • Non-nuclear-weapon states agree not to acquire nuclear weapons
  • Nuclear-weapon states commit to disarmament and peaceful nuclear cooperation
  • The International Atomic Energy Agency (IAEA) verifies compliance through safeguards
• The Comprehensive Nuclear-Test-Ban Treaty (CTBT) prohibits all nuclear test explosions
  • The CTBT has not yet entered into force, but most states adhere to a testing moratorium
• Nuclear-weapon-free zones (NWFZs) prohibit the development, deployment, and use of nuclear weapons in specific regions
  • Existing NWFZs cover Latin America, the South Pacific, Southeast Asia, Africa, and Central Asia
• Bilateral arms control agreements between the United States and Russia have limited strategic nuclear forces
  • The New Strategic Arms Reduction Treaty (New START) caps deployed warheads and delivery systems until 2026
• Multilateral export control regimes (Nuclear Suppliers Group, Zangger Committee) coordinate restrictions on the transfer of sensitive technologies

Detection and Verification Methods

• Seismic monitoring detects underground nuclear tests by measuring seismic waves
  • The Comprehensive Nuclear-Test-Ban Treaty Organization (CTBTO) operates a global network of seismic stations
• Atmospheric monitoring detects radioactive particles and gases released by nuclear tests
  • Radionuclide monitoring can identify the specific isotopes produced in a nuclear explosion
• Satellite imagery can identify nuclear facilities, test sites, and delivery systems
  • Imagery analysis can detect construction, modifications, and activity at suspect sites
• Environmental sampling collects air, water, soil, and vegetation samples to detect traces of nuclear materials
  • Sampling can reveal undeclared nuclear activities or verify the absence of such activities
• On-site inspections allow international experts to directly access and investigate suspect sites
  • Inspections may involve visual observation, radiation detection, and sample collection
• Open-source intelligence (OSINT) gathers and analyzes publicly available information
  • OSINT sources include news reports, scientific publications, and social media

Current Global Nuclear Landscape

• Nine states are known to possess nuclear weapons: the United States, Russia, the United Kingdom, France, China, India, Pakistan, Israel (presumed), and North Korea
• The United States and Russia maintain the largest nuclear arsenals, with thousands of warheads each
  • Both countries are modernizing their nuclear forces, raising concerns about a new arms race
• China, India, and Pakistan are expanding and diversifying their nuclear capabilities
  • Regional tensions (India-Pakistan, China-India) could escalate into nuclear conflicts
• North Korea has conducted six nuclear tests and developed intercontinental ballistic missiles (ICBMs)
  • Diplomatic efforts to denuclearize North Korea have made limited progress
• Iran's nuclear program has raised proliferation concerns
  • The Joint Comprehensive Plan of Action (JCPOA) limited Iran's nuclear activities, but the agreement is under strain
• Nuclear terrorism remains a significant threat
  • Efforts to secure nuclear materials and prevent illicit trafficking are ongoing
• The Treaty on the Prohibition of Nuclear Weapons (TPNW) seeks to delegitimize nuclear weapons
  • The TPNW has been criticized by nuclear-armed states and their allies as unrealistic and divisive