Introduction to Nuclear Introduction to Nuclear WeaponsWeapons

Physical SciencePhysical Science

I. Nuclear PhysicsI. Nuclear Physics

A.A. Key ConceptsKey Concepts1.1. The atom: The atom:

Nucleus Nucleus surrounded by surrounded by electrons (a.k.a. electrons (a.k.a. beta particles)beta particles)

2. The Nucleus: Protons and 2. The Nucleus: Protons and NeutronsNeutrons

a.a. Electro-magnetism Electro-magnetism holds electrons in holds electrons in orbit (electrons are orbit (electrons are negatively negatively charges, protons charges, protons are positive)are positive)

b.b. ““Strong nuclear Strong nuclear force” holds force” holds protons and protons and neutrons together neutrons together (137 times as (137 times as strong as electro-strong as electro-magnetism)magnetism)

3. Elements3. Elements

a.a. Definition: Elements are atoms with the Definition: Elements are atoms with the same # of protons in nuclei (their atomic same # of protons in nuclei (their atomic number)number)

b.b. Change # protons = change elementChange # protons = change elementc.c. Atomic weight = protons + neutrons + Atomic weight = protons + neutrons +

electrons (trivial weight)electrons (trivial weight)d.d. Change # neutrons but not protons = Change # neutrons but not protons =

same element but different atomic weight same element but different atomic weight isotope (Carbon-12, Carbon-13, isotope (Carbon-12, Carbon-13, Carbon 14, etc.)Carbon 14, etc.)

4. The novelty of nuclear weapons4. The novelty of nuclear weapons

a.a. Chemistry – Elements are combined into Chemistry – Elements are combined into compounds (atoms become molecules), compounds (atoms become molecules), which can release electro-magnetic energy which can release electro-magnetic energy as heat, light, etc. ALL weapons before 1945 as heat, light, etc. ALL weapons before 1945 use chemistry – explosives, napalm, toxins, use chemistry – explosives, napalm, toxins, etc.etc.

b.b. Nuclear weapons use the strong nuclear Nuclear weapons use the strong nuclear force for destruction force for destruction inherently more inherently more powerful than any possible chemical reaction powerful than any possible chemical reaction (by weight)(by weight)

B. Fission: Splitting a NucleusB. Fission: Splitting a Nucleus

1.1. Heavy nuclei are unstable – Put too Heavy nuclei are unstable – Put too many protons together and they repel many protons together and they repel each other. Too many (or too few) each other. Too many (or too few) neutrons can increase this repulsion.neutrons can increase this repulsion.

2.2. Spontaneous fission: Unstable heavy Spontaneous fission: Unstable heavy nuclei can randomly fission – break into nuclei can randomly fission – break into two smaller nuclei (different elements). two smaller nuclei (different elements).

3. Induced fission3. Induced fission

Throw a neutron at an unstable nucleus Throw a neutron at an unstable nucleus and:and: It might escape (pass by without being It might escape (pass by without being

captured by nucleus)captured by nucleus)Be absorbed into the nucleusBe absorbed into the nucleusTrigger fission of the nucleus into two nuclei Trigger fission of the nucleus into two nuclei

(shown)(shown)

4. The Fission Chain Reaction4. The Fission Chain Reactiona.a. More energy is required to hold one heavy nucleus More energy is required to hold one heavy nucleus

together than two moderate-sized nuclei. together than two moderate-sized nuclei. b.b. Therefore, splitting a heavy nucleus releases a great deal Therefore, splitting a heavy nucleus releases a great deal

of energy (strong nuclear force). of energy (strong nuclear force). c.c. If neutrons cause fission, and fission creates more If neutrons cause fission, and fission creates more

neutrons, a chain reaction may ensue. Small initial energy neutrons, a chain reaction may ensue. Small initial energy (a few neutrons) cascades to trillions of split nuclei. (a few neutrons) cascades to trillions of split nuclei.

d.d. Uncontrolled chain reaction = fission explosion. Requires Uncontrolled chain reaction = fission explosion. Requires Critical MassCritical Mass (enough nuclei close together for neutrons to (enough nuclei close together for neutrons to be more likely to hit nuclei than fly out of the mass without be more likely to hit nuclei than fly out of the mass without hitting anything)hitting anything)

e.e. Critical mass varies by element, isotope, shape (spheres Critical mass varies by element, isotope, shape (spheres work best), and density (so compressing sub-critical mass work best), and density (so compressing sub-critical mass can make it “go critical” and explode)can make it “go critical” and explode)

Example: Chain Reaction in U-235Example: Chain Reaction in U-235

C. Fusion: Combining NucleiC. Fusion: Combining Nuclei

1.1. It takes more energy to hold two light It takes more energy to hold two light nuclei together than a single moderate-nuclei together than a single moderate-sized nucleus.sized nucleus.

2.2. Therefore, forcing two light nuclei Therefore, forcing two light nuclei together into one nucleus generates together into one nucleus generates energy.energy.

3.3. In general, fusion produces more energy In general, fusion produces more energy than fission (which means bigger bombs)than fission (which means bigger bombs)

Curve of Binding Energy: Note energy Curve of Binding Energy: Note energy increase in fusion (light elements) increase in fusion (light elements)

compared to fission (heavy elements)compared to fission (heavy elements)

4. The problem of fusion4. The problem of fusiona.a. Fission is easy – just throw some neutrons at Fission is easy – just throw some neutrons at

inherently-unstable nuclei and they splitinherently-unstable nuclei and they splitb.b. Fusion is hard – Hydrogen doesn’t just Fusion is hard – Hydrogen doesn’t just

randomly slam into itself with the energy level randomly slam into itself with the energy level of the sun’s core. About 100 million degrees of the sun’s core. About 100 million degrees required to overcome strong nuclear force.required to overcome strong nuclear force.

c.c. All efforts to create controlled fusion use more All efforts to create controlled fusion use more energy to force the nuclei together than they energy to force the nuclei together than they extract from fusionextract from fusion

d.d. BUT we do have one tool to generate huge BUT we do have one tool to generate huge amounts of uncontrolled energy – a fission amounts of uncontrolled energy – a fission chain reaction! (Even this just barely provides chain reaction! (Even this just barely provides enough energy – limiting fusion weapons to enough energy – limiting fusion weapons to very light elements like hydrogen)very light elements like hydrogen)

II. Weapon DesignII. Weapon Design

A.A. The most basic fission weapon (aka The most basic fission weapon (aka atomic bomb) – The U-235 weaponatomic bomb) – The U-235 weapon

1.1. U-235 is U-235 is fissilefissile – Only low-energy neutrons – Only low-energy neutrons are needed to split the nucleus. Other types are needed to split the nucleus. Other types of uranium (U-238, the most common type) of uranium (U-238, the most common type) require very high-energy neutrons for fission require very high-energy neutrons for fission (= nearly impossible to create a chain (= nearly impossible to create a chain reaction)reaction)

2.2. Critical mass of U-235 = 50 kg (about 110 Critical mass of U-235 = 50 kg (about 110 pounds) in a sphere.pounds) in a sphere.

Advantage of U-235 over U-238Advantage of U-235 over U-238

3. The gun-type nuclear weapon3. The gun-type nuclear weapona.a. Principle = Quickly mash two sub-critical Principle = Quickly mash two sub-critical

pieces of U-235 together into one piece pieces of U-235 together into one piece above critical mass. Detonation ensues.above critical mass. Detonation ensues.

b.b. Simplified design:Simplified design:

4. Barriers to building a 4. Barriers to building a gun-type weapongun-type weapon

a.a. Getting the U-235Getting the U-235 99.3% of Uranium is U-238. 99.3% of Uranium is U-238.

Must Must enrichenrich uranium to uranium to increase % of U-235 increase % of U-235

Combine uranium with fluorine Combine uranium with fluorine to make uranium hexafluoride to make uranium hexafluoride gas (“hex”). Then put hex in a gas (“hex”). Then put hex in a container surrounded by a container surrounded by a membrane. Slightly more U-membrane. Slightly more U-235 will diffuse out than U-238. 235 will diffuse out than U-238. Also useful…Also useful…

Gas CentrifugesGas Centrifuges

Since U-235 is Since U-235 is lighter than U-238, lighter than U-238, spinning hex spinning hex rapidly pulls the U-rapidly pulls the U-238 to the edge 238 to the edge and leaves more and leaves more U-235 in the U-235 in the middlemiddle

US cascade of US cascade of centrifuges centrifuges

b. The danger of “fizzle”b. The danger of “fizzle” Difficult to eliminate the last U-238 from the U-235 (Hiroshima Difficult to eliminate the last U-238 from the U-235 (Hiroshima

bomb was 80% U-235 / 20% U-238)bomb was 80% U-235 / 20% U-238) U-238 spontaneously fissions, generating neutronsU-238 spontaneously fissions, generating neutrons Danger = chance that U-238 will start a partial chain reaction Danger = chance that U-238 will start a partial chain reaction

just before critical mass is reached. Blows U-235 apart before just before critical mass is reached. Blows U-235 apart before most of it has a chance to fission. Result = small explosion.most of it has a chance to fission. Result = small explosion.

Solution = assemble critical mass so quickly that U-238 is Solution = assemble critical mass so quickly that U-238 is unlikely to spontaneously fission at the wrong moment (we now unlikely to spontaneously fission at the wrong moment (we now know Hiroshima bomb had just under a 10% chance of fizzle – know Hiroshima bomb had just under a 10% chance of fizzle – the U-238 in the weapon spontaneously fissioned about 70 the U-238 in the weapon spontaneously fissioned about 70 times/second)times/second)

Similar problem makes U-233 gun-type bombs difficult to build Similar problem makes U-233 gun-type bombs difficult to build (contaminated with U-232, which fissions too rapidly) and Pu-(contaminated with U-232, which fissions too rapidly) and Pu-239 ones impossible (contaminated with Pu-240)239 ones impossible (contaminated with Pu-240)

More complex designs reduce – but do not eliminate – chance More complex designs reduce – but do not eliminate – chance of fizzle. DPRK test probably fizzled (very small blast)of fizzle. DPRK test probably fizzled (very small blast)

c. Safety problems c. Safety problems

i.i. Accident-prone: Two subcritical masses Accident-prone: Two subcritical masses kept in close proximity to explosiveskept in close proximity to explosives

ii.ii. Accidental moderation: Seawater Accidental moderation: Seawater moderates (slows) neutrons, and slower moderates (slows) neutrons, and slower neutrons are more likely to cause fission neutrons are more likely to cause fission before escaping the core. Result = drop before escaping the core. Result = drop bomb in seawater = potential detonation!bomb in seawater = potential detonation!

iii.iii. Terrorist’s dream: Easy to use U-235 to Terrorist’s dream: Easy to use U-235 to improvise a nuclear deviceimprovise a nuclear device

B. The Basic Implosion-Type B. The Basic Implosion-Type Fission WeaponFission Weapon

1.1. Why bother?Why bother?a.a. Desire to use Pu-239 (can be made using Desire to use Pu-239 (can be made using

nuclear reactors, so no separation necessary)nuclear reactors, so no separation necessary)b.b. Compressing material takes 1/10 the time of Compressing material takes 1/10 the time of

slamming it together (helps prevent fizzle)slamming it together (helps prevent fizzle)c.c. Less fissile material is required if it can be Less fissile material is required if it can be

compressedcompressedd.d. Much safer – accidental detonation can be Much safer – accidental detonation can be

made impossiblemade impossiblee.e. Allows flexibility: some or all charges can be Allows flexibility: some or all charges can be

detonated, compressing material to different detonated, compressing material to different degreesdegrees

Advantage Advantage of Pu-239 of Pu-239

2. The basic components2. The basic components

a.a. Subcritical mass of Plutonium (any isotope), U-Subcritical mass of Plutonium (any isotope), U-233 (rarely), U-235, Np-237 (similar to U-235 233 (rarely), U-235, Np-237 (similar to U-235 but easier to obtain), or Am-241 (theoretically) but easier to obtain), or Am-241 (theoretically) surrounded by explosives surrounded by explosives nearly all nearly all designs use Pu-239 or U-235designs use Pu-239 or U-235

b.b. Explosives are shaped, layered, and timed to Explosives are shaped, layered, and timed to generate a spherical shock wavegenerate a spherical shock wave

c.c. Neutron initiator supplies neutrons to begin Neutron initiator supplies neutrons to begin fission at right moment – too soon causes fission at right moment – too soon causes fizzle, but so does too late (material rebounds fizzle, but so does too late (material rebounds after compression)after compression)

d.d. Tamper between explosives and Pu-239 helps Tamper between explosives and Pu-239 helps to reflect neutrons and hold compression for a to reflect neutrons and hold compression for a moment or two to maximize yieldmoment or two to maximize yield

Simplified Implosion DesignSimplified Implosion Design

3. Maximizing Efficiency (Proportion 3. Maximizing Efficiency (Proportion of material that fissions before the of material that fissions before the whole thing blows itself apart into whole thing blows itself apart into

sub-critical pieces)sub-critical pieces)

a.a. Neutron reflector: Surrounds fissile material Neutron reflector: Surrounds fissile material below tamper to bounce stray neutrons back below tamper to bounce stray neutrons back into the coreinto the core

b.b. Levitating core: Empty space between tamper Levitating core: Empty space between tamper and core to allow tamper to build up and core to allow tamper to build up momentum (standard in today’s weapons)momentum (standard in today’s weapons)

c.c. External neutron trigger (particle accelerator External neutron trigger (particle accelerator outside the sphere) – also useful if you want to outside the sphere) – also useful if you want to put something else in the center of the core….put something else in the center of the core….

C. Boosted Fission Weapons: C. Boosted Fission Weapons: Using Fusion to Increase PowerUsing Fusion to Increase Power

1.1. Problem: Most fissile material wasted (only 1%-20% fission Problem: Most fissile material wasted (only 1%-20% fission before it blows itself apart – Hiroshima bomb was 1.4% before it blows itself apart – Hiroshima bomb was 1.4% efficient). More neutrons needed!efficient). More neutrons needed!

2.2. Solution = fill core with isotopes of H that fuse easily: Solution = fill core with isotopes of H that fuse easily: Deuterium (D or H-2 -- 1 proton, 1 neutron) and Tritium (T or Deuterium (D or H-2 -- 1 proton, 1 neutron) and Tritium (T or H-3 -- 1 proton, 2 neutrons) can fuse into He-4 (2 protons, 2 H-3 -- 1 proton, 2 neutrons) can fuse into He-4 (2 protons, 2 neutrons), creating energy and 1 extra neutron. neutrons), creating energy and 1 extra neutron. Fusion Fusion energy generated is trivialenergy generated is trivial in these weapons, but… in these weapons, but…

3. The “boost”: Extra neutrons hit the fissile material and cause more of it to fission before blowing itself apart. Result = much larger explosion (about double the explosive power).

4. Advantages: Higher yield for equal mass – which also means weapons can be miniaturized (up to a point), “dial-a-yield” through control of D/T injected into center.

Schematic of Primary Part Schematic of Primary Part of Boosted Fission Weaponof Boosted Fission Weapon

Aluminum case (1 cm)

High explosive (10 cm)

Tamper (tungsten or uranium) (3 cm)

Beryllium reflector (2 cm)

Fissile material (U-235 or Pu-239)

Hollow core, where D (H-2) and T (H-3) are injected for boosting.

C. Boosted Fission Weapons: C. Boosted Fission Weapons: Using Fusion to Increase PowerUsing Fusion to Increase Power

1.1. Problem: Most fissile material wasted (only 1%-20% fission Problem: Most fissile material wasted (only 1%-20% fission before it blows itself apart – Hiroshima bomb was 1.4% before it blows itself apart – Hiroshima bomb was 1.4% efficient). More neutrons needed!efficient). More neutrons needed!

2.2. Solution = fill core with isotopes of H that fuse easily: Solution = fill core with isotopes of H that fuse easily: Deuterium (D or H-2 -- 1 proton, 1 neutron) and Tritium (T or Deuterium (D or H-2 -- 1 proton, 1 neutron) and Tritium (T or H-3 -- 1 proton, 2 neutrons) can fuse into He-4 (2 protons, 2 H-3 -- 1 proton, 2 neutrons) can fuse into He-4 (2 protons, 2 neutrons), creating energy and 1 extra neutron. neutrons), creating energy and 1 extra neutron. Fusion Fusion energy generated is trivialenergy generated is trivial in these weapons, but… in these weapons, but…

3.3. The “boost”: Extra neutrons hit the fissile material and cause The “boost”: Extra neutrons hit the fissile material and cause more of it to fission before blowing itself apart. Result = much more of it to fission before blowing itself apart. Result = much larger explosion (about double the explosive power).larger explosion (about double the explosive power).

4.4. Advantages: Higher yield for equal mass – which also means Advantages: Higher yield for equal mass – which also means weapons can be miniaturized (up to a point), “dial-a-yield” weapons can be miniaturized (up to a point), “dial-a-yield” through control of D/T injected into center.through control of D/T injected into center.

D. Staged Fusion Weapons: D. Staged Fusion Weapons: The Thermonuclear or The Thermonuclear or

Hydrogen BombHydrogen Bomb

1.1. Parts:Parts:a.a. The “primary stage” – A The “primary stage” – A

fission devicefission device

b.b. The “secondary stage” – The “secondary stage” – designed to fuse when designed to fuse when bombarded with bombarded with radiationradiation

c.c. The casing: Usually The casing: Usually made of U-238made of U-238

2. Inside the Secondary2. Inside the SecondaryRadiation channels filled with polystyrene Radiation channels filled with polystyrene

foam surround the capsulefoam surround the capsuleThe capsule walls are made of U-238The capsule walls are made of U-238Spark plug of plutonium boosts fusion Spark plug of plutonium boosts fusion

3. Radiation Implosion3. Radiation Implosion

a.a. Primary ignites Primary ignites high-energy X-Rays high-energy X-Rays

b.b. X-Rays fill the radiation channels, turn X-Rays fill the radiation channels, turn polystyrene to plasmapolystyrene to plasma

c.c. Tamper is heated Tamper is heated outside ablates outside ablates (vaporizes – think of an inside-out rocket). (vaporizes – think of an inside-out rocket). Ablation compresses the nuclear fuel.Ablation compresses the nuclear fuel.

d.d. Plasma helps keep the tamper from blocking Plasma helps keep the tamper from blocking the radiation channels, increasing duration of the radiation channels, increasing duration of compressioncompression

4. The fusion explosion4. The fusion explosion

a.a. Compressed fuel must still be heatedCompressed fuel must still be heatedb.b. Plutonium “spark plug” in center of fusion Plutonium “spark plug” in center of fusion

fuel is compressed, becomes super-fuel is compressed, becomes super-critical and fissions (raises temperature critical and fissions (raises temperature inside case)inside case)

c.c. Result = huge pressures and Result = huge pressures and temperatures produce fusion, which temperatures produce fusion, which releases far more energy than fission releases far more energy than fission PLUS “fast fission” of spark plug from PLUS “fast fission” of spark plug from fusion-produced neutronsfusion-produced neutrons

5. The fuel5. The fuel

a.a. Early designs (first US test) used Early designs (first US test) used deuterium and tritium – but this deuterium and tritium – but this required cryogenic machinery (D required cryogenic machinery (D and T are gases at room and T are gases at room temperature)temperature)

b.b. Modern designs use solid Lithium Modern designs use solid Lithium Deuteride instead. Enriched fuel Deuteride instead. Enriched fuel (lots of Li-6) much more effective.(lots of Li-6) much more effective.

c.c. The fusion process: Neutrons from The fusion process: Neutrons from fission turn some D into T, which fission turn some D into T, which then fuse together, generating then fuse together, generating more neutrons. Some D and T also more neutrons. Some D and T also fuses with Lithium (but this fuses with Lithium (but this generates less energy).generates less energy).

E. Enhanced Fusion WeaponsE. Enhanced Fusion Weapons

1.1. Fission-Fusion-Fission designs: Make the Fission-Fusion-Fission designs: Make the bomb case out of U-238 or even U-235 and bomb case out of U-238 or even U-235 and it will detonate when neutrons from the it will detonate when neutrons from the fusion capsule hit it, greatly enhancing yield fusion capsule hit it, greatly enhancing yield (doubling power is easy)(doubling power is easy)

2.2. Multi-stage weapons: Use the secondary Multi-stage weapons: Use the secondary stage to compress a tertiary stage, and so stage to compress a tertiary stage, and so forth. Each stage can be 10-100 times forth. Each stage can be 10-100 times larger than previous stage (= unlimited larger than previous stage (= unlimited explosive potential)explosive potential)

III. Detonation ParametersIII. Detonation Parameters

A.A. Yield – A measure of explosive powerYield – A measure of explosive power1.1. Expressed as kt or Mt of TNTExpressed as kt or Mt of TNT

2.2. Measures power not weight – 20 kt weapon Measures power not weight – 20 kt weapon is equivalent to detonating 20,000 TONS of is equivalent to detonating 20,000 TONS of TNT all at once. 1 Mt means the equivalent TNT all at once. 1 Mt means the equivalent of a million tons of TNT detonating at once.of a million tons of TNT detonating at once.

Examples: “Tiny” to HugeExamples: “Tiny” to HugeOklahoma City non-nuclear bomb (.002 Kt)Oklahoma City non-nuclear bomb (.002 Kt)Davy Crockett nuclear rifle (.01 kt)Davy Crockett nuclear rifle (.01 kt)British tactical nuclear weapon (1.5 kt)British tactical nuclear weapon (1.5 kt)The nuclear cannon (15 kt)The nuclear cannon (15 kt)Hiroshima (15 kt) and Nagasaki (20 kt)Hiroshima (15 kt) and Nagasaki (20 kt)Max pure fission: Orange Herald (720 kt)Max pure fission: Orange Herald (720 kt)Chinese (3 Mt) and British (1.8 Mt) H-BombsChinese (3 Mt) and British (1.8 Mt) H-BombsLargest deployed weapon (25 Mt)Largest deployed weapon (25 Mt)Tsar Bomba, the largest bomb tested (58 Mt)Tsar Bomba, the largest bomb tested (58 Mt)

Comparative fireballs by yieldComparative fireballs by yield

B. Height: Air-Burst vs. Ground-BurstB. Height: Air-Burst vs. Ground-BurstZones of destruction (1 Mt weapon)Zones of destruction (1 Mt weapon)

Groundburst (energy concentrated at ground Groundburst (energy concentrated at ground zero):zero):

Airburst (energy distributed over wider area):Airburst (energy distributed over wider area):

IV. Effects of Nuclear WeaponsIV. Effects of Nuclear WeaponsA.A. Prompt effectsPrompt effects

1.1. Thermal and Thermal and visible radiation visible radiation (heat and light)(heat and light)

a.a. Initial pulse = Initial pulse = 1/10 second (too 1/10 second (too quick for eyes to quick for eyes to react). Few react). Few killed, but many killed, but many blindedblinded

b.b. Second pulse = Second pulse = most heat most heat damage, lasts up damage, lasts up to 20 seconds for to 20 seconds for large weapons large weapons

c. Biological c. Biological effectseffects

i. “Flash burns” – i. “Flash burns” – Most prominent Most prominent on exposed on exposed areas (i.e. dark areas (i.e. dark areas of kimono areas of kimono worn by this worn by this victim)victim)

Burns 1.5 miles from hypocenter in Burns 1.5 miles from hypocenter in NagasakiNagasaki

Add 20% for 1Add 20% for 1stst degree burn range, degree burn range, subtract 20% for 3subtract 20% for 3rdrd degree burn range degree burn range

ii. Blindness: Most far-reaching ii. Blindness: Most far-reaching prompt effectprompt effect

Flash Flash blindness blindness (temporary) (temporary) and retinal and retinal burns burns (permanent) (permanent) from light from light focused on focused on retinaretina

iii. Fire Stormsiii. Fire Storms Heat ignites flammable materialsHeat ignites flammable materials If large enough area burns, it creates its own If large enough area burns, it creates its own

wind system, sucking in oxygen to feed the wind system, sucking in oxygen to feed the flamesflames

Natural example in Peshtigo, WI (1871): “A wall Natural example in Peshtigo, WI (1871): “A wall of flame, a mile high, five miles (8 km) wide, of flame, a mile high, five miles (8 km) wide, traveling 90 to 100 miles (200 km) an hour, traveling 90 to 100 miles (200 km) an hour, hotter than a crematorium, turning sand into hotter than a crematorium, turning sand into glass.”glass.”

Firestorms in Hiroshima (but not Nagasaki), Firestorms in Hiroshima (but not Nagasaki), Dresden, Tokyo in World War II.Dresden, Tokyo in World War II.

Result: Large numbers of people not burned by Result: Large numbers of people not burned by nuclear detonation will be burned by subsequent nuclear detonation will be burned by subsequent firestorms sweeping through cityfirestorms sweeping through city

2. Blast 2. Blast damagedamage

a.a. Heat of fireball Heat of fireball causes air to causes air to expand rapidly, expand rapidly, generating a generating a shock waveshock wave

b.b. Shock wave hits Shock wave hits and damages and damages buildings, and is buildings, and is followed by…followed by…

c.c. Low-pressure Low-pressure area follows and area follows and sucks everything sucks everything backwards (blast backwards (blast wind)wind)

Note the Mach Front:Note the Mach Front:

1 Mt

d. Biological Effectsd. Biological Effects

Few likely to die from blast wave itself, but Few likely to die from blast wave itself, but flying debris may kill manyflying debris may kill manyLung damage occurs at about 70 KPa (double Lung damage occurs at about 70 KPa (double

the pressure needed to shatter concrete the pressure needed to shatter concrete walls)walls)

Ear damage begins at 22 KPa (as brick walls Ear damage begins at 22 KPa (as brick walls shatter)shatter)

In general, heat will kill anyone close In general, heat will kill anyone close enough to experience primary blast enough to experience primary blast damage. Crushed buildings will kill many damage. Crushed buildings will kill many outside this zone.outside this zone.

3. Ionizing Radiation3. Ionizing Radiation

For most weapons, immediate radiation For most weapons, immediate radiation (gamma rays and neutrons) will only kill (gamma rays and neutrons) will only kill those very close to the explosionthose very close to the explosion

More on biological effects later…More on biological effects later…

Destructive Radius (km) of Blast Effects, By Yield of Weapon

0

5

10

15

20

25

30

35

40

45

50

2.5 5 10 25 250 2500 25000

Yield (Kt)

Dis

tan

ce (

km)

Thermal

Blast

Radiation

Hiroshima Health Dept EstimatesHiroshima Health Dept EstimatesShort-Term Fatalities At Hiroshima

Burns

Debris

Radiation

4. Electromagnetic 4. Electromagnetic Pulse (EMP)Pulse (EMP)

High-altitude High-altitude nuclear bursts nuclear bursts generate generate magnetic fields magnetic fields over large over large areas (induces areas (induces current in current in transistors and transistors and integrated integrated circuits) circuits) fried fried electronicselectronics

B. FalloutB. Fallout

1.1. Definition: Radioactive particles fall to Definition: Radioactive particles fall to earth (fission products, contaminated soil earth (fission products, contaminated soil and debris sucked up by explosion)and debris sucked up by explosion)

2. Dangers of Ionizing Radiation2. Dangers of Ionizing Radiation

a.a. Alpha radiationAlpha radiationi.i. Composed of Helium nuclei (2 protons, 2 Composed of Helium nuclei (2 protons, 2

neutrons)neutrons)ii.ii. Little danger unless inhaled or ingested – Little danger unless inhaled or ingested –

stopped by a piece of paper (or skin)stopped by a piece of paper (or skin)iii.iii. Very destructive if inhaled or ingested (only Very destructive if inhaled or ingested (only

known example = Alexander Litvinenko, known example = Alexander Litvinenko, poisoned with alpha-emitter Po-210)poisoned with alpha-emitter Po-210)

b. Beta radiationb. Beta radiation

i.i. Consists of electrons emitted by Consists of electrons emitted by radioactive atomsradioactive atoms

ii.ii. Can burn exposed skin – stopped by Can burn exposed skin – stopped by clothing, skin, and gogglesclothing, skin, and goggles

iii.iii. Effective range is only a few feet, so Effective range is only a few feet, so exposure to radioactive dust is most exposure to radioactive dust is most likely source of damage (no known likely source of damage (no known fatalities from beta exposure at fatalities from beta exposure at Hiroshima or Nagasaki)Hiroshima or Nagasaki)

c. Gamma radiationc. Gamma radiationi.i. Extremely high energy photons emitted Extremely high energy photons emitted

by the detonation and falloutby the detonation and fallout

ii.ii. Penetrating power is high. Needed to Penetrating power is high. Needed to reduce exposure by half:reduce exposure by half:

d. Neutron radiationd. Neutron radiation

i.i. Produced by blast itself, insignificant in falloutProduced by blast itself, insignificant in fallout

ii.ii. Induces radioactivity (alpha, beta, gamma) in Induces radioactivity (alpha, beta, gamma) in materials it encountersmaterials it encounters

iii.iii. Shielding requires light elements (hydrogen, Shielding requires light elements (hydrogen, lithium)lithium)

iv.iv. Enhanced-Radiation Weapons, aka “Neutron Enhanced-Radiation Weapons, aka “Neutron Bombs” -- permit fusion-produced neutrons to Bombs” -- permit fusion-produced neutrons to escape, killing people even in armored escape, killing people even in armored vehicles (explosions still level civilian vehicles (explosions still level civilian structures)structures)

e. Measures of Radiatione. Measures of Radiation

i.i. Measurements of exposure: 100 rad = 1 Measurements of exposure: 100 rad = 1 graygray

ii.ii. Relative biological effectiveness (RBE): Relative biological effectiveness (RBE): alpha = up to 20, neutron varies, alpha = up to 20, neutron varies, beta/gamma/X-Rays = 1beta/gamma/X-Rays = 1

iii.iii. Measures of effect: rad * RBE = rem, Measures of effect: rad * RBE = rem, gray * RBE = sievertgray * RBE = sievert

iv.iv. Since gamma exposure is likely to be Since gamma exposure is likely to be source of most radiation poisoning, rad source of most radiation poisoning, rad usually = rem and gray usually = sievertusually = rem and gray usually = sievert

f. Radiation Poisoning (Acute f. Radiation Poisoning (Acute Radiation Syndrome)Radiation Syndrome)

i.i. Triggered by Triggered by cumulative exposure cumulative exposure – hourly dose * hours – hourly dose * hours exposedexposed

ii. LD 50 ii. LD 50 is 4.5 is 4.5 GraysGrays

g. Danger of Internal Absorptiong. Danger of Internal Absorption

Strontium-90 is chemically similar to Strontium-90 is chemically similar to Calcium Calcium incorporated into bones incorporated into bones

Iodine 131 is absorbed by the thyroidIodine 131 is absorbed by the thyroidCesium 137 is chemically similar to Cesium 137 is chemically similar to

potassium and absorbed throughout the potassium and absorbed throughout the bodybody

3. Distribution of Fallout3. Distribution of Fallout

a.a. Fallout = “point-source pollutant” Fallout = “point-source pollutant” (exposure almost always decreases with (exposure almost always decreases with distance)distance)

i.i. Key variables = speed and direction of wind.Key variables = speed and direction of wind.

ii.ii. Closer to source usually more dangerous – Closer to source usually more dangerous – but downwind “hot spots” are possiblebut downwind “hot spots” are possible

1 Mt Surface Burst: Cumulative and 1 Mt Surface Burst: Cumulative and Hourly Radiation ExposureHourly Radiation Exposure

““Hot Spots” from Castle Bravo TestHot Spots” from Castle Bravo Test

b. US-USSR Predictionsb. US-USSR Predictions Immediate Deaths:Immediate Deaths:

Fallout (1977 estimates):Fallout (1977 estimates):

Fallout (1990 Estimate)Fallout (1990 Estimate)

Fallout (USSR Estimate)Fallout (USSR Estimate)

4. Half-Life4. Half-Life

a.a. Definition: Time for 50% of a radioactive Definition: Time for 50% of a radioactive substance to decaysubstance to decay

b.b. Short half-life: These isotopes are very Short half-life: These isotopes are very radioactive but don’t last longradioactive but don’t last long

c.c. Long half-life: These are less radioactive Long half-life: These are less radioactive but also long-livedbut also long-lived

Example: 100 KT Surface Blast, Example: 100 KT Surface Blast, Fort Hood Main GateFort Hood Main Gate

100 KT = larger than ordinary fission 100 KT = larger than ordinary fission bomb, smaller than largest Russian bomb, smaller than largest Russian weaponsweapons

15 psi: Virtually all dead

5 psi: 50% dead, 45% injured

2 psi: 5% dead, 45% injured)

1 psi: 25% injured

Compare: 1 MT Surface BlastCompare: 1 MT Surface Blast

Compare: 20KT Surface BlastCompare: 20KT Surface Blast

100 KT Surface: Fallout100 KT Surface: Fallout

1 hour: Lethal2 hours: Lethal3 hours: Lethal4 hours: Lethal and 50% Lethal5 hours: Lethal and 50% LethalPossible Zone of Sickness

C. “Nuclear Winter”C. “Nuclear Winter”

1.1. Theory that nuclear war would cause Theory that nuclear war would cause global cooling global cooling bigger nuclear wars = bigger nuclear wars = more and longer coolingmore and longer cooling

2.2. Mechanism: Soot and smoke from urban Mechanism: Soot and smoke from urban firestorms and forest fires rises to firestorms and forest fires rises to stratosphere, carried around globe, stratosphere, carried around globe, remains for prolonged time, blocks remains for prolonged time, blocks sunlightsunlight

Nuclear Holocaust

Cities burn Ground bursts

Massive amounts of smoke Massive amounts of dust

Sunlight absorbed Sunlight reflected

Very little sunlight reaches the ground

Rapid, large surface temperature drops

“Nuclear Winter”

3. Technical Issues (See Pry)3. Technical Issues (See Pry)a.a. Initial TTAPS study (dramatized here) was Initial TTAPS study (dramatized here) was

poorpoor

b.b. Models assume carbon lofted into Models assume carbon lofted into stratosphere – but this process is only stratosphere – but this process is only confirmed for very small particles (diesel soot)confirmed for very small particles (diesel soot)

c.c. Models assume urban/forest targeting – bases Models assume urban/forest targeting – bases may be more logical targetsmay be more logical targets

d.d. Standard objections to climate modeling (no Standard objections to climate modeling (no global climate models are perfect)global climate models are perfect)

4. Political Issues: Why Hard-Liners 4. Political Issues: Why Hard-Liners (such as Pry) Opposed the Theory(such as Pry) Opposed the Theory

a.a. Theory undermines conventional deterrence: if Theory undermines conventional deterrence: if nuclear winter is believed by policymakers, the nuclear winter is believed by policymakers, the world is safe for conventional warworld is safe for conventional war

b.b. Theory undermines nuclear deterrence: Theory undermines nuclear deterrence: Irrational to retaliate if doing so makes nuclear Irrational to retaliate if doing so makes nuclear winter worse for everyone (including one’s own winter worse for everyone (including one’s own people)people)

c.c. Theory undermines rationale for nuclear arms Theory undermines rationale for nuclear arms race: more weapons threaten human extinction race: more weapons threaten human extinction if used (early studies come from left-wing if used (early studies come from left-wing scientists and environmentalists)scientists and environmentalists)

5. Scientific 5. Scientific AnalysisAnalysis

a.a. Cold War studies: Cold War studies: Better science Better science generally found generally found smaller “nuclear smaller “nuclear winter” effects winter” effects (note that most studies (note that most studies were excluded from were excluded from Pry’s chart on p. 203 – Pry’s chart on p. 203 – which was taken from which was taken from the conservative the conservative National Review)National Review)

b. Post-Cold War Studiesb. Post-Cold War Studies

Almost no studies 1990-2005: Why?Almost no studies 1990-2005: Why?2006 study: 100 Hiroshima-sized bombs 2006 study: 100 Hiroshima-sized bombs

on 100 subtropical cities (obviously talking on 100 subtropical cities (obviously talking about India and Pakistan)about India and Pakistan)

b. Post-Cold War Studiesb. Post-Cold War Studies

Almost no studies 1990-2005: Why?Almost no studies 1990-2005: Why? 2006 study: 100 Hiroshima-sized bombs on 2006 study: 100 Hiroshima-sized bombs on

100 subtropical cities (obviously talking 100 subtropical cities (obviously talking about India and Pakistan)about India and Pakistan)Predicts that some tropospheric soot (which Predicts that some tropospheric soot (which

usually rains out quickly) would be heated by usually rains out quickly) would be heated by the sun and enter the stratosphere (where no the sun and enter the stratosphere (where no rain occurs)rain occurs)

Predicts reduced cooling but lasts longer (up to Predicts reduced cooling but lasts longer (up to 10 years)10 years)

Chief danger: Food SupplyChief danger: Food Supply

Summer won’t turn to winter – but it may Summer won’t turn to winter – but it may turn to autumn, with repeated freezes turn to autumn, with repeated freezes threatening cropsthreatening crops

Chief danger: Food SupplyChief danger: Food Supply

Summer won’t turn to winter – but it may Summer won’t turn to winter – but it may turn to autumn, with repeated freezes turn to autumn, with repeated freezes threatening cropsthreatening crops

Besides temperature, ozone depletion, Besides temperature, ozone depletion, changes in precipitation, and reduced changes in precipitation, and reduced sunlight all reduce productivitysunlight all reduce productivity

2008 Study: A “SORT” War2008 Study: A “SORT” War Imagines 2012 global nuclear war using Imagines 2012 global nuclear war using

arsenals which have been reduced by arsenals which have been reduced by (existing) arms control agreements(existing) arms control agreements

““SORT SORT war” war” scenario: scenario: open to open to question…question…

Comparison: Regional (5 Tg) vs. Comparison: Regional (5 Tg) vs. SORT (150 Tg or more)SORT (150 Tg or more)

D. Popular Perceptions and D. Popular Perceptions and PropagandaPropaganda

1. Examples of anti-nuclear research and culture:1. Examples of anti-nuclear research and culture: Nuclear Winter: Theory popularized by Carl Sagan before academic Nuclear Winter: Theory popularized by Carl Sagan before academic

publication (PARADE Magazine)publication (PARADE Magazine) Film treatments dramatize dangers in 1980s:Film treatments dramatize dangers in 1980s:

The Day AfterThe Day After ThreadsThreads When the Wind BlowsWhen the Wind Blows

Soviet Propaganda: ExamplesSoviet Propaganda: Examples

““Two worlds - Two worlds - two goals. We two goals. We are planning are planning new life. They new life. They are planning are planning death.”death.”

Soviet Propaganda: ExamplesSoviet Propaganda: Examples

““A Christmas A Christmas present for the present for the people”people”

Soviet Propaganda: ExamplesSoviet Propaganda: Examples

““What What dangerous dangerous madness!”madness!”

Soviet Propaganda: ExamplesSoviet Propaganda: Examples

““Myth – and Myth – and reality.”reality.”

D. Popular Perceptions and D. Popular Perceptions and PropagandaPropaganda

1. Examples of anti-nuclear research and culture:1. Examples of anti-nuclear research and culture: Nuclear Winter: Theory popularized by Carl Sagan before academic Nuclear Winter: Theory popularized by Carl Sagan before academic

publication (PARADE Magazine)publication (PARADE Magazine) Film treatments dramatize dangers in 1980s:Film treatments dramatize dangers in 1980s:

The Day AfterThe Day After ThreadsThreads When the Wind BlowsWhen the Wind Blows

Soviet PropagandaSoviet Propaganda

Responses:Responses: Indictments of the TTAPS study (long after others have moved on)Indictments of the TTAPS study (long after others have moved on) Pry, “Societal Survival” (Assigned)Pry, “Societal Survival” (Assigned) Most responses focused on elites, not public (no counter-films, for Most responses focused on elites, not public (no counter-films, for

example). Why?example). Why?