Nuclear Weapons

Units of Radiation Dose Roentgen – Ability to create a specified electric charge per volume of air Rem (Roentgen equivalent man) –Biological effect of one roentgen of X-rays Rad (Radiation absorbed dose) – Energy absorption: 400,000 rads heat H 2 O 1 deg For general human exposure, these units are roughly equivalent

Background Radiation Cosmic Rays Solar Wind Decay of Natural Radioactivity Typical Doses – Global Average 0.1 rem/year (80% natural) – Some areas up to 1 rem/year – Ramsar, Iran: up to 26 rem/year

Human Radiation Sources Nuclear Fallout from Atmospheric Testing (US and Russia, 1963; France, 1974; China, 1980) Chernobyl 1986 Uranium Mining Radon release from construction and earth- moving Conventional power plants

Human Survival Limits 200 rem (whole body): few immediate fatalities 500 rem (whole body): 50% fatalities 1000 rem (whole body): No survivors

Chain Reaction

Nuclear Fission Chain reaction requires a critical mass to proceed 10 kg U-235 = 2.5 x atoms 1,2,4,8 … 2.5 x = 85 1/1,000,000 sec per step = 1/10,000 sec After 64 steps, T = 10,000 K (twice as hot as sun) Have only completed 1/1,000,000 of fission

Nuclear Weapons To get a nuclear explosion, you have to Assemble a critical mass in millionths of a second Retain a high percentage of the neutrons Hold the material together against temperatures hotter than the Sun Imposes limits on yield of weapon Unless something is specifically designed to be a nuclear weapon, it will not explode

Yields of Nuclear Weapons Kiloton = 1000 tons of explosives = 4.2 x joules = calories – Texas City, Texas, April 16-17, 1947 – Collapse of World Trade Center – Impact of 10-m asteroid Megaton = 1,000,000 tons of explosives = 4.2 x joules = calories – Magnitude 7 earthquake – Impact of 100-m asteroid

“Das war keine gute Idee”

Effects of Nuclear Weapons Direct ionizing radiation Heat (Fireball) – Rising fireball sucks dust upward, creates “mushroom cloud” – Any large explosion will create a “mushroom cloud” Blast (Expansion of Fireball) Fallout Volume α Yield: Radius α 3 √ Yield

All Large Explosions Make Mushroom Clouds

Nuclear Explosion

Weapons Terminology Warhead: The Actual Explosive Component of a Nuclear Weapon Warhead Section: The Delivery Casing for a Nuclear Weapon. Includes casing, radars, timers, detonators, etc When most people say “Warhead,” they actually mean “Warhead Section.” Tactical = Range < 500 km Strategic = Range > 500 km

Some Nuclear Factoids Nuclear weapons are always under armed guard Nobody Ever Goes Near a Nuke Alone. U.S. Protocols Call for a “Two Man” Rule There are persistent rumors we allowed designs of our locking mechanisms to be leaked to the Russians Information on locations of nuclear weapons is classified “Secret” or above Do not confirm/deny

Nuclear Weapons Systems All military explosive weapons have had nuclear versions – Artillery Shells – Bombs – Depth Charges – Rockets – Missiles – Anti-Aircraft – Stationary charges

DASA and SASCOM

“Little Boy” Gun Type, Uranium

“Fat Man” Implosion, Plutonium

Early Strategic Nuke

Trinitite

Atomic Bomb

Delivery Systems

Titan Warhead

Minuteman Warheads

Minuteman Missile Silo, SD

MIRV

Tactical Nukes

Nuclear Artillery Shell

Atomic Cannon

“Birdcage” for Artillery Shell Fissionable Material

Davy Crockett

SADM

MADM

Cradle For Nuclear Artillery Shell

Palomares, Spain: My Bad

Russian Nukes

Nuclear Winter Publicized by Carl Sagan and others in 1980’s Global nuclear exchange would raise large amounts of dust and soot into upper atmosphere Would absorb or reflect sunlight, cooling the surface Would be above most precipitation processes Did not happen in Gulf War 1991

Fusion Natural: how stars (and the sun) generate energy Artificial and uncontrolled: Thermonuclear Weapon (hydrogen bomb) Fusion Reactor: controlled “Energy source of the future. Always has been, always will be.”

Core of the Sun Energy output: 90 billion megatons/second Energy output = 6 microwatts/kg – less than a candle Human body outputs 1.2 W/kg – 200,000 times greater Trying to duplicate sun’s energy output not practical on Earth Energy takes 10,000 – 100,000 years to reach surface

Uncontrolled Fusion We cannot achieve T and P necessary to use ordinary hydrogen Have to use H-2 (deuterium) or H-3 (tritium) Still need T = 1,000,000 K+ Initiated by a nuclear (fission) weapon Fission weapons yield up to 20 kilotons Fusion (hydrogen or thermonuclear) weapons yield up to 20 megatons

Controlled Fusion Temperatures too high for any material Need to contain by magnetic fields, achieve small-scale reactions for short periods Have not achieved break-even Apparatus will be incredibly complex and expensive Reactions give off neutrons: there will still be radioactive waste No spent fuel or fissionable residue

Detecting Nuclear Explosions Vela System (US) Space: X-ray and Gamma Ray pulses Atmospheric: – Double-humped light pulse – Initial Fireball – Obscured by ionized gas in shock wave – Revealed again as shock wave cools – Vela Incident, September 22, 1979 Subsurface: Seismic First Motion Analysis

Nuclear Powers and Wannabes