Reactors and Bombs Short Version

Reactor Components Moderator – Small A – Small probability of absorbing neutrons; Water Heavy water (deuterium) Graphite Coolant Control Rods – Absorbers that suck up neutrons Cadmium, indium, boron Delayed neutrons (0.7%)

Uranium Isotopes

Enrichment Numbers Low-Enriched Uranium (LEU) or Reactor Grade Fuel = 3-5% U 235 Highly-Enriched Uranium (HEU) or Weapons Grade Fuel = % U 235

Enrichment - Centrifuge

Centrifuge Cascade

Uranium Is Encased in Solid Ceramic Pellets

Fuel Pellet

Nuclear Fuel Assembly Fuel Pellet

Reactor Core

Boiling Water Reactor

PWR

CANDU

Graphite Reactor

Plutonium Production

vol_5/5-1/purexch.

Breeder Reactor

TMI

Chernobyl Reactor

Contamination

History Part – Neils Bohr and John Wheeler proposed detailed theory (Liquid Drop Model) 1939 – Fermi unsuccessfully tried to alert US Navy of importance of research 1939 – Einstein’s famous letter to Roosevelt (Szilard, and Wigner) 1941 – Britain joins US effort 1942 – Fermi, first reactor in Chicago, Oppenheimer in charge.

Neutrons From Fission Possible Fission Fuel IsotopeAverage Neutron Released SlowFast 233 U U U00.97 U - natural Pu

Manhattan Project Gen GrovesOppenheimer

Oak Ridge - K-25 Enrichment Plant U

Hanford Reactor – 239 Pu

Los Alamos – Science, Assembly

Critical “Mass” How much material needed to sustain a chain reaction and build a weapon. Depends on – Mass – Shape – Density – Configuration

Critical Masses FuelCritical Mass W/O With Tamper (U) With Tamper (Be) Natural Uranium No! 20 % 235 U160 kg65 kg 50 % 235 U68 kg25 kg 100 % 235 U47 kg16 kg14 kg 80 % 239 Pu5.4 kg 100 % 239 Pu10 kg4.5 kg4 kg

Explosion Sequence Numbers of Fissions Boom!

Yield Yield of Nuclear Weapons in equivalent explosive power of tonnes of TNT – (1 tonne = 1000 kg) 1 kT = 1000 tonnes is equivalent to 4.2x10 12 J of energy – (from kg of 235 U) 1 MT = 1 million tonnes of TNT

Gun-Barrel Device

Little Boy: A Gun-Type Bomb 28” in diameter, 10” long, 9,000 lbs 50 kg of Uranium, 70% 235 U Critical mass = 17” in diameter Y = 12.5 kT

Neutron Trigger PoBe Thin metal foil

Plutonium Bomb In a Reactor three isotopes of Plutonium produced 239 Pu, 240 Pu, 241 Pu 240 Pu and 241 Pu undergo spontaneous fission A gun barrel design too slow to prevent a “fizzle” Spontaneous Fission 240 Pu and 241 Pu

Plutonium Bomb In a Reactor three isotopes of Plutonium produced 239 Pu, 240 Pu, 241 Pu 240 Pu and 241 Pu undergo spontaneous fission A gun barrel design too slow to prevent a “fizzle”

Fat Man: Implosion-type bomb

Fat Man: Implosion-Type Bomb 60” in diameter, 10”8” long 5 kg of Pu Y = 20 kT

Nuclear Fusion

1 st Use of Fusion

Fusion Boosted Fission Weapon

Normal sequence, of fission generations. Boom! Boosted Weapon Bigger Boom!

Second Use of Fusion Actual Fusion Explosion Used Liquid tritium and deuterium Size of a building 10 MT 1952

Important Elements of Fusion Bomb Lithium Hydride (LH) but made with deuterium Lithium deuteride LD Just need a source of neutrons and lots of energy and high temperatures

Fission Bomb!

Sequence of Events 1.High explosive detonates – compresses Pu and trigger 2.Fission occurs 3.Neutrons reflected by casing changes lithium to tritium 4.X-rays focused by Styrofoam unto LD target 5.Fusion occurs releasing energy AND NEUTRONS 6.If outer casing made of 238 U, a second large fission explosion occurs! (If made of 235 U, an even bigger fission explosion (x2)) Possible Fission Fuel IsotopeAverage Neutron Released SlowFast 233 U U U00.97 U - natural Pu

Fusion Weapon