NUCLEAR WEAPONSNUCLEAR WEAPONS

Paul SnellerPaul Sneller

HistoryHistory

1905 – Einstein’s Theory of Special Relativity.1905 – Einstein’s Theory of Special Relativity. 1932 – The Neutron is Discovered by James Chadwick.1932 – The Neutron is Discovered by James Chadwick. 1938 – Otto Hahn and Fritz Strassman are able to split 1938 – Otto Hahn and Fritz Strassman are able to split

a uranium atom by bombarding it with neutrons.a uranium atom by bombarding it with neutrons. 1942 – First self sustaining nuclear reaction is 1942 – First self sustaining nuclear reaction is

produced by scientists at the University of Chicago.produced by scientists at the University of Chicago. 1945 – First Nuclear Weapon detonated at Trinity, New 1945 – First Nuclear Weapon detonated at Trinity, New

Mexico.Mexico. 1945 – Nuclear Weapons are dropped on the cities of 1945 – Nuclear Weapons are dropped on the cities of

Hiroshima and Nagasaki.Hiroshima and Nagasaki. 1952 – First Teller-Ulam hydrogen bomb detonated.1952 – First Teller-Ulam hydrogen bomb detonated.

Nuclear FissionNuclear Fission

A nuclear reaction in which an atomic nucleus splits A nuclear reaction in which an atomic nucleus splits into fragments.into fragments.

Fission occurs readily in U-235 and Pu-239 when Fission occurs readily in U-235 and Pu-239 when bombarded with neutrons.bombarded with neutrons.

The sum of the product masses is less than the mass The sum of the product masses is less than the mass of the original atom.of the original atom.

The lost mass is converted directly into energy.The lost mass is converted directly into energy. The fission of a single Uranium-235 nucleus generates The fission of a single Uranium-235 nucleus generates

about 3.36E-11J about 3.36E-11J

Nuclear FusionNuclear Fusion

The combination of two nuclei to form a single atom.The combination of two nuclei to form a single atom. The product’s mass is less than the mass of the The product’s mass is less than the mass of the

original atoms.original atoms. Fusion occurs most readily in a combination of the Fusion occurs most readily in a combination of the

hydrogen isotopes deuterium and tritium.hydrogen isotopes deuterium and tritium. Temperature in the millions of degrees is required to Temperature in the millions of degrees is required to

initiate fusion.initiate fusion. A Deuterium-Tritium fusion generates about 2.8E-12J A Deuterium-Tritium fusion generates about 2.8E-12J

of energyof energy

CriticalityCriticality

In order for a nuclear reaction to be self-sustaining, In order for a nuclear reaction to be self-sustaining, there must be a “critical mass” of fissile material.there must be a “critical mass” of fissile material.

This is the mass necessary so that, on average, at least This is the mass necessary so that, on average, at least one neutron produced by every fission goes on to one neutron produced by every fission goes on to trigger another fission.trigger another fission.

Having less than critical mass will cause the bomb to Having less than critical mass will cause the bomb to “fizzle” and have a very low efficiency.“fizzle” and have a very low efficiency.

Actual mass required for criticality depends on the Actual mass required for criticality depends on the density of the mass, the shape of its configuration, and density of the mass, the shape of its configuration, and the presence/effectiveness of the neutron reflector.the presence/effectiveness of the neutron reflector.

Due to natural emission of neutrons, any critical mass Due to natural emission of neutrons, any critical mass has a chance of beginning a nuclear chain reaction.has a chance of beginning a nuclear chain reaction.

The Fission BombThe Fission Bomb

To prevent premature detonation of a weapon, the To prevent premature detonation of a weapon, the nuclear material must be separated into two or more nuclear material must be separated into two or more sub critical masses.sub critical masses.

The mechanism which combines these masses is the The mechanism which combines these masses is the most important part of the weapon.most important part of the weapon.

The mechanism must combine the sub critical The mechanism must combine the sub critical masses into one supercritical mass fast enough that masses into one supercritical mass fast enough that the mass is fully assembled before there is any the mass is fully assembled before there is any chance of the chain reaction blowing the fissile chance of the chain reaction blowing the fissile material apart and causing the bomb to fizzle.material apart and causing the bomb to fizzle.

The Neutron GeneratorThe Neutron Generator

In order to ensure that a chain reaction begins, there In order to ensure that a chain reaction begins, there has to be free neutrons present in the fissile material has to be free neutrons present in the fissile material when the critical mass is assembled.when the critical mass is assembled.

A combination of Po-210 which emits alpha particles, A combination of Po-210 which emits alpha particles, and Beryllium, which emits neutrons when struck by and Beryllium, which emits neutrons when struck by an alpha particle.an alpha particle.

The two substances can be separated by a foil which The two substances can be separated by a foil which blocks alpha particles and is designed to break when blocks alpha particles and is designed to break when the bomb is triggered.the bomb is triggered.

The TamperThe Tamper

The tamper is a thick layer of heavy material which is The tamper is a thick layer of heavy material which is designed to produce pressure on the fissionable core designed to produce pressure on the fissionable core as the bomb detonates, allowing more fissions to as the bomb detonates, allowing more fissions to occur before the materials are blown apart by the occur before the materials are blown apart by the energy release.energy release.

The tamper is usually constructed out of U-238 and The tamper is usually constructed out of U-238 and doubles as a neutron reflector, redirecting neutrons doubles as a neutron reflector, redirecting neutrons back into the core and increasing the efficiency of the back into the core and increasing the efficiency of the reaction.reaction.

The most effective tamper is Be-9 which actually The most effective tamper is Be-9 which actually produces two neutrons when struck by a single produces two neutrons when struck by a single neutron.neutron.

Weapon DesignsWeapon Designs

Gun-triggered fissionGun-triggered fission Implosion-triggered fissionImplosion-triggered fission Fusion Bombs Fusion Bombs

Gun-triggeredGun-triggered

This is the simplest form of nuclear weapon.This is the simplest form of nuclear weapon. A bullet of U-235 is propelled by explosives into a U-A bullet of U-235 is propelled by explosives into a U-

235 sphere.235 sphere. Because of the relatively slow combination of the Because of the relatively slow combination of the

critical mass, this method works only with U-235.critical mass, this method works only with U-235. This is the type of bomb that destroyed the Japanese This is the type of bomb that destroyed the Japanese

city of Hiroshima.city of Hiroshima.

Gun-triggeredGun-triggered

Implosion-triggered Implosion-triggered

A sub critical sphere of plutonium is surrounded by A sub critical sphere of plutonium is surrounded by explosives, when the explosives detonate they create explosives, when the explosives detonate they create a shockwave which compresses the core.a shockwave which compresses the core.

The increased density of the core causes it to become The increased density of the core causes it to become supercritical, and the nuclear reaction begins.supercritical, and the nuclear reaction begins.

This method can be used with both U-235 and Pu-239.This method can be used with both U-235 and Pu-239. This is the type of weapon detonated at the Trinity This is the type of weapon detonated at the Trinity

site, and on the Japanese city of Nagasaki.site, and on the Japanese city of Nagasaki. To properly compress instead of blowing it apart, it is To properly compress instead of blowing it apart, it is

necessary to use explosive lenses, which create a necessary to use explosive lenses, which create a concave shockwave that fits the surface of the core.concave shockwave that fits the surface of the core.

Implosion TriggeredImplosion Triggered

Teller-Ulam BombTeller-Ulam Bomb

The first true fusion bomb design.The first true fusion bomb design. Utilizes a fission weapon to provide the necessary Utilizes a fission weapon to provide the necessary

energy to cause fusion.energy to cause fusion. The massive amount of X-rays released by the fission, The massive amount of X-rays released by the fission,

which travel much faster than the actual explosion, which travel much faster than the actual explosion, are contained by a thick tamper and used to provide are contained by a thick tamper and used to provide the heat to initiate a fusion reaction before the the heat to initiate a fusion reaction before the explosion has a chance to blow apart the bomb.explosion has a chance to blow apart the bomb.

Uses lithium deuterate as a fuel.Uses lithium deuterate as a fuel. When lithium is struck by a neutron it produces an When lithium is struck by a neutron it produces an

alpha particle and tritium, which readily fuses with the alpha particle and tritium, which readily fuses with the deuterium in the extreme temperature created by the deuterium in the extreme temperature created by the fission bomb. fission bomb.

Can be scaled to nearly limitless power.Can be scaled to nearly limitless power.

Teller-Ulam BombTeller-Ulam Bomb

Teller-Ulam BombTeller-Ulam Bomb

The EffectsThe Effects

Standard Nuclear weapons emit approximately 50% of Standard Nuclear weapons emit approximately 50% of their total energy as blast energy, 35% as thermal their total energy as blast energy, 35% as thermal energy, and 15% as radiation.energy, and 15% as radiation.

The actual effects of the weapon vary greatly The actual effects of the weapon vary greatly depending on the yield, and the detonation point.depending on the yield, and the detonation point.

Detonation in the upper atmosphere can create Detonation in the upper atmosphere can create massive EMPs, severely damaging many electronics.massive EMPs, severely damaging many electronics.

Detonation in the lower atmosphere results in Detonation in the lower atmosphere results in enormous pressure damage over a larger area.enormous pressure damage over a larger area.

Surface Detonation results in blast and thermal Surface Detonation results in blast and thermal damage, and large amounts of fallout.damage, and large amounts of fallout.

Subterranean detonation results in large shockwaves, Subterranean detonation results in large shockwaves, but minimizes most of the effects, provided the blast but minimizes most of the effects, provided the blast does not break the surfacedoes not break the surface

10 Kiloton Surface 10 Kiloton Surface BlastBlast 1/3 mile radius: All but the sturdiest of buildings are 1/3 mile radius: All but the sturdiest of buildings are

completely destroyed, those that remain are merely completely destroyed, those that remain are merely empty shells, fatality rate is nearly 100%empty shells, fatality rate is nearly 100%

3/4 mile radius: Anyone directly exposed to the blast 3/4 mile radius: Anyone directly exposed to the blast receives a lethal radiation dose, all buildings suffer receives a lethal radiation dose, all buildings suffer heavy damages, fatality rate is approximately 50% heavy damages, fatality rate is approximately 50% with 45% injured.with 45% injured.

1 mile radius: Heat wave causes widespread fires and 1 mile radius: Heat wave causes widespread fires and the area is ravaged by radiation. Approximately 5% of the area is ravaged by radiation. Approximately 5% of the population is killed, with 45% injured.the population is killed, with 45% injured.

25 Megaton Airburst 25 Megaton Airburst

6.5 mile radius: All but the sturdiest of buildings are 6.5 mile radius: All but the sturdiest of buildings are destroyed, fatality rate is nearly 100%destroyed, fatality rate is nearly 100%

10.7 mile radius: Buildings suffer heavy damage, 10.7 mile radius: Buildings suffer heavy damage, approximately 50% of the population is dead and 45% approximately 50% of the population is dead and 45% injured.injured.

20 mile radius: Windows, and many of the occupants 20 mile radius: Windows, and many of the occupants of large buildings are blown out, small buildings are of large buildings are blown out, small buildings are heavily damaged or destroyed, approximately 5% heavily damaged or destroyed, approximately 5% dead and 45% injured.dead and 45% injured.

30.4 mile radius: Buildings are slightly damaged, 30.4 mile radius: Buildings are slightly damaged, approximately 25% of the population is injured.approximately 25% of the population is injured.

Construction Construction FeasibilityFeasibility To produce a functional gun-triggered nuclear To produce a functional gun-triggered nuclear

weapon, there are only 4 main requirements.weapon, there are only 4 main requirements. Access to a sufficient quantity of weapons grade Access to a sufficient quantity of weapons grade

material, or the equipment needed to enrich uranium material, or the equipment needed to enrich uranium ore.ore.

Precision machine tools.Precision machine tools. Safety equipment to protect against radiation.Safety equipment to protect against radiation. High explosives.High explosives.

Construction Construction FeasibilityFeasibility Due to the widespread availability of resources such Due to the widespread availability of resources such

as explosives, machine tools, and protective gear, as explosives, machine tools, and protective gear, sufficient monetary resources make such items trivial.sufficient monetary resources make such items trivial.

The only real impediment to non-nuclear nations and The only real impediment to non-nuclear nations and terrorists is the availability of weapons grade Uranium. terrorists is the availability of weapons grade Uranium.

Uranium AcquisitionUranium Acquisition

Although Uranium is actually fairly common in nature, Although Uranium is actually fairly common in nature, Uranium-235, the isotope required for nuclear Uranium-235, the isotope required for nuclear weapons, accounts for only .71% of all naturally weapons, accounts for only .71% of all naturally occurring Uranium. occurring Uranium.

Any sizable amount of Uranium-235 is closely Any sizable amount of Uranium-235 is closely monitored by international agencies, therefore the monitored by international agencies, therefore the most feasible means of obtaining weapons grade most feasible means of obtaining weapons grade uranium is to enrich uranium ore.uranium is to enrich uranium ore.

Uranium EnrichmentUranium Enrichment

There are several methods to enriching UraniumThere are several methods to enriching Uranium The most efficient method is by combining uranium The most efficient method is by combining uranium

with fluorine to Uranium hexafluoride and then using a with fluorine to Uranium hexafluoride and then using a gas centrifuge to separate the isotopes.gas centrifuge to separate the isotopes.

Other methods include electromagnetic isotope Other methods include electromagnetic isotope separation (EMIS) and gaseous diffusion.separation (EMIS) and gaseous diffusion.

All of these methods require a significant amount of All of these methods require a significant amount of electricity, some specialized equipment, a larger electricity, some specialized equipment, a larger supply of uranium ore, and a good deal of time, as supply of uranium ore, and a good deal of time, as each process only slightly increases the percentage of each process only slightly increases the percentage of U-235, and concentrations of over 90% are necessary U-235, and concentrations of over 90% are necessary for nuclear weapons.for nuclear weapons.

ConclusionConclusion

Nuclear weapons are one of modern science’s Nuclear weapons are one of modern science’s greatest achievements, harnessing the conversion of greatest achievements, harnessing the conversion of mass to energy.mass to energy.

They range from fairly simple, to extremely complex, They range from fairly simple, to extremely complex, but they all are extremely powerful and deadly.but they all are extremely powerful and deadly.

Although construction of a basic nuclear weapon is Although construction of a basic nuclear weapon is fairly straightforward, the logistical problems involved fairly straightforward, the logistical problems involved with obtaining sufficient nuclear fuel, the careful with obtaining sufficient nuclear fuel, the careful monitoring of nuclear development should prevent monitoring of nuclear development should prevent terrorists and third world nations from constructing terrorists and third world nations from constructing them for quite some time.them for quite some time.