Nuclear Fission

1. Revolves around the battle between good nuclear attractive forces and evil electrical repulsion forces. Usually, nuclear forces overpower everything in the nuclei, but in Uranium, repulsive forces nearly rival the nuclear ones. If Uranium’s nucleus is stretched, electrical forces may stretch it further. If the nucleus stretches past a critical point, nuclear forces give way and the nucleus separates. This is nuclear fission. Nuclear Fission

2. The absorption of a neutron by a Uranium nucleus is enough to cause stretching. Written as follows:

3. The combined mass of the fission fragments is less than the mass of the original Uranium atom. • The tiny amount of missing mass is converted into A LOT of energy. • One Uranium reaction releases about 200000000 e- volts. In comparison, the explosion of a TNT molecule releases 30 e- volts.

4. The scientific community was taken aback by the jaw-dropping intensity of nuclear fission reactions, as the amount of energy released and the number of neutrons liberated was extraordinary. • A typical fission reaction releases 2-3 neutrons, which will divide into 2-3 more nuclei, which will release 4-9 more neutrons, which will continue to divide further and further. • This is known as a chain reaction. • Naturally occurring U-238 does not chain react, as it isn’t refined enough. Only U-235 (only 0.7% of natural U) will go through fission. -The minimum amount of mass required to sustain a chain reaction is called the critical mass.

5. Nuclear Physics The Atomic Bomb & U-235 Separation

6. The Manhattan Engineer District The Manhattan Project A project designed to research and create a usable atomic bomb. Now commonly called

7. 1939- Albert Einstein along with several other physicists sent a letter to President Franklin D. Roosevelt. It encouraged the research and development of an atomic bomb. They feared the Germans had already embarked on such a course. The result is what we now call the Manhattan Project.

8. Totals for the Project • 40 laboratories and factories • Employed 200,000 people • Total cost: $ 1,889,604,000 • Constant 1996 dollars: $ 21,570,821,000

9. Physicists struggle to determine how to spark a fission chain reaction.

10. Their Solution… • Drive 2 pieces of U-235 (each w/ less than the critical mass) together • If done correctly and at the right time, the combined mass will exceed the critical mass • Then a violent, chain reaction explosion will occur

11. U-235 Separation… The construction of a Uranium fission bomb is not a formidable task. The difficulty is separating enough U-235 from the more abundant U-238.

12. Slightly lighter U-235 moves at a faster speed than U-238 at the same temperature. As a gas, the faster isotope has a higher rate of diffusion through a thin membrane at the same temperature. Results in slightly enriched U-235 gas on the other side of the membrane.

13. U-235 moves faster than U-238 because both have the same KE (1/2mv^2). • So, U-235 has a lower mass and thus a higher velocity.

14. It took Manhattan Project scientists and engineers more than two years to extract enough U-235 from uranium ore to make the bomb that was detonated over Hiroshima in 1945. Uranium isotope separation is still a difficult, expensive process today.

15. Sources • Chapter Notes on Nuclear Physics Mr. Bobby • Conceptual Physics Third Edition Paul G. Hewitt • The Atomic Bomb Paper Natalie Bate (2000) • “Albert Einstein” Microsoft Encarta 96 Encyclopedia

16. Thanks… Concept, design, and creation by Natalie Bate and Chris Geddes for 1st period Physics. To everyone who paid attention. Questions… comments… *smart remarks… …see Natalie Bate or *Chris Geddes 5/15/02

17. Plutonium • When U-238 absorbs a neutron, no fission occurs. • Nucleus then emits a Beta particle and becomes Neptunium. • At Neptunium’s ½ life (2.3 days), another Beta particle is emitted and it becomes Plutonium. • The new isotope Pu-239 will undergo fission when it captures a neutron

18. The primary use of fermis atomic pile was to make Pu. • The development of Pu-239 solved the dilemma of separating U-235 out of U-238. • Pu will fission, and it’s much easier to obtain than U-235. • The bomb that exploded over Nagasaki was a Plutonium bomb. • Very dangerous due to radiation • Used on breeder reactors

19. Breeder Reactors • When U-238 is mixed with fissionable isotopes in a reactor, the neutrons released turn the abundant U238 into fissionable Pu-239 • This in effect creates more fuel than it consumes • For every 2 fissionable isotopes put into the reactor => 3 fissionable isotopes are produced • Nuclear Reactors are simply nuclear furnaces, which boil H2O to produce electricity

20. plutonium • When U-238 absorbs a neutron, no fission occurs. • The nucleus then emits a beta particle & becomes neptunium. • At neptunium’s half life, (2.3 days) another beta particle is emitted & becomes plutonium. • The new isotope Pu-239 will undergo fission when it captures a neutron. • The primary use of Fermis atomic pile was to make Pu. • The development of Pu-239 solved the dilemma of separating U-235 out of U-238. • Pu will fission, & it’s much easier to obtain than U-235 • Very dangerous due to radiation. • Used in breeder reactors.

21. Breeder Reactors • When U-238 is mixed with fissionable isotpes in a reactor, the neutrons released turn the abundant U-238into fissionable Pu-239. • This in effect creates more fuel than it consumes. • For every 2 fissionable isotopes put into the reactor, 3 new fissionable isotopes are produced. • Nuclear reactors are simply nuclear furnaces, which boil H2O produce electricity.

22. Nuclear Fusion Fusion Reaction can produce as much as 26,700,000 e- Volts Nuclear Fusion involves combining Hydrogen nuclei to form Helium • The mass lost in the fusion of Hydrogen • appears as energy

23. + + + + 1 1 2 2 2 2 4 3 + + + + H H He n H H He n 2 1 1 1 2 2 0 0 + + + + + + 3.26 MeV + 17.6 MeV + • Nuclei must collide very quickly to overcome • electromagnetic repulsion of protons

24. Controlling Fusion Tokamak Fusion Reactor

25. Tokamak Fusion Reactor • an experimental controlled fusion reactor • A donut-shaped fusion device that is • surrounded by electrical coils which produce • intense magnetic fields to confine hot, D-T • fuel plasma.

26. Frozen Deuterium Chamber • Deuterium is an isotope of Hydrogen that is • available in large quantities in seawater • Tritium is easily produced from deuterium

27. In inertial confinement fusion, deuterium and tritium are liquefied under high pressure and confined in tiny glass spheres. Multiple laser beams are directed at the spheres. The energy deposited by the lasers results in forces that make the pellets implode, squeezing their contents. The tremendous compression of the hydrogen that results raises the temperature to the levels needed for fusion.

28. Cold Fusion Meuon induced fusion • Meuon has the same charge as an e- but is • 200 times more massive • orbits very close to the nucleus • effectively cancels out electromagnetic • repulsion of protons • Only exists for 2 nanoseconds at a time • Would allow the nucleus to fuse at low • temperatures, for example a light bulb

29. Fusion Torch of today Raw Materials Products Consumers Production Plants Waste & Pollution Non-fusion power

30. POLLUTION

31. White hot flame or plasma in which materials can be dumped • Plasma will break waste down to an atomic level • Atoms can then be separated using a mass spectrometer type device

32. the future... Raw materials Products Fusion Power Waste & Pollution Fusion torch recycling plant

33. Boiling Water Reactors • Water is boiled and turned to steam • Steam is used to rotate a turbine • The turbine powers a generator, which in turn creates electricity • Steam is recycled into water by a condenser

34. Boiling Water Reactor

35. Pressurized Water Reactors • Water is heated, but pressurized so that it doesn’t boil • Pressurized water flows through a different tank of water, boiling that water • Steam generated rotates a turbine, that powers a generator • Generator creates electricity • Steam sent through a condenser and recycled back into water to continue the process

36. Pressurized Water Reactor