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Nuclear Weapons. Units of Radiation Dose Roentgen – Ability to create a specified electric charge per volume of air Rem (Roentgen equivalent man) –Biological.

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Presentation on theme: "Nuclear Weapons. Units of Radiation Dose Roentgen – Ability to create a specified electric charge per volume of air Rem (Roentgen equivalent man) –Biological."— Presentation transcript:

1 Nuclear Weapons

2 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

3 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

4 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

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

6 Chain Reaction

7 Nuclear Fission Chain reaction requires a critical mass to proceed 10 kg U-235 = 2.5 x 10 25 atoms 1,2,4,8 … 2.5 x 10 25 = 85 steps @ 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

8 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

9 Yields of Nuclear Weapons Kiloton = 1000 tons of explosives = 4.2 x 10 12 joules = 10 12 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 10 15 joules = 10 15 calories – Magnitude 7 earthquake – Impact of 100-m asteroid

10 “Das war keine gute Idee”

11 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

12 All Large Explosions Make Mushroom Clouds

13 Nuclear Explosion

14 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

15 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

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


18 “Little Boy” Gun Type, Uranium

19 “Fat Man” Implosion, Plutonium

20 Early Strategic Nuke


22 Trinitite

23 Atomic Bomb

24 Delivery Systems

25 Titan Warhead

26 Minuteman Warheads


28 Minuteman Missile Silo, SD


30 Tactical Nukes

31 Nuclear Artillery Shell

32 Atomic Cannon

33 “Birdcage” for Artillery Shell Fissionable Material

34 Davy Crockett



37 Cradle For Nuclear Artillery Shell

38 Palomares, Spain: My Bad

39 Russian Nukes

40 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

41 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.”

42 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

43 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

44 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

45 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



48 Nuclear Powers and Wannabes

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