How much energy

• 200 MeV is released per fission event• The fission of 1 g of uranium or plutonium per

day liberates about 1 MW. • This is the energy equivalent of 3 tons of coal

or about 600 gallons of fuel oil per day• No CO2 emissions!

• Vastly superior in terms of energy per amount of fuel

Self sustaining or chain reaction

• The fission reaction itself releases neutrons, these can be used to fission additional nuclei, so the elements are there for a sustained or chain reaction.

• Tremendous power capability made this an ideal weapon.

Fission Bombs• Created in response to a fear that Nazi Germany

would develop one first, which would tip the balance of power and possibly the outcome of WWII in their favor.

• Manhattan Project – Secret US project to develop a nuclear weapon

• Developed 3 nuclear devices, one with 235U and two with 239PU.

• One was tested in New Mexico in 1945, the other two were dropped on Hiroshima and Nagasaki Japan in August 1945, ending WWII in the Pacific.

Critical Mass

• In order to sustain a chain reaction, one needs a specific amount of fissionable material, called the critical mass

• Critical mass is the smallest amount of fissile material needed for a sustained nuclear chain reaction.

• Creating the critical mass was one of the challenges that faced the Manhattan project

The devices

• Fat Man and Little Boy • Little Boy – device dropped on Hiroshima• Gun-type device– One mass of U-235, the "bullet," is fired down a

gun barrel into another mass of U-235, rapidly creating the critical mass of U-235, resulting in an explosion.

The devices• Fat Man• Tested in New Mexico and dropped on Nagasaki• Used Plutonium rather than Uranium• Implosion style device– The required implosion was achieved by using shaped charges with many explosive lenses to produce the perfectly spherical explosive wave which compressed the plutonium sphere.

Effects of a Fission explosion

• Blast Damage• Thermal radiation• Electromagnetic Pulse• Ionizing radiation• earthquake

Blast Damage

• 40-50% of the total energy released is in the blast.

• Most of the destruction due to blast effects

• Blast wind may exceed 1000 km/h.

Thermal Radiation• 35-45% of the energy released

is in thermal radiation• Burns occur• Eye injures

– Flash Blindness-caused by the initial bright flash, can last up to 40 minutes

– Retinal burns – scarring due to the direct concentration of explosions thermal energy on the eye-rare the fireball needs to be in the direct line of sight

• Firestorms-gale force winds that blow in from all sides towards the center of a fire

Electromagnetic pulse• The nuclear explosion produced

high energy electromagnetic radiation-Gamma rays.

• The Gamma rays interact with (scatter) electrons and produce higher energy electrons.

• Long metal objects (cables, etc) act as antenna and generate high voltages and currents, which can damage or destroy electrical equipment.

• No known biological effects, though useful against Sentinels (The Matrix).

Ionizing radiation• About 5% of the energy• In the form of neutrons,

gamma rays, alpha particles and electrons, moving at nearly the speed of light

• Neutrons transmutate (change the atomic structure of) the surrounding matter, often making it radioactive. This adds to the radioactive fallout

What does this have to do with Nuclear Energy

• It sets the historical context and shows the power released

• To point out that this is NOT what will happen if there is an accident in a nuclear power facility-they do not “blow up” like explosive nuclear devices. More on that later