Nuclear Reactions:. AN INTRODUCTION TO FISSION, FUSION, AND NUCLEAR POWER. Nuclear reactions deal with interactions between the nuclei of atoms The focus of this presentation are the processes of nuclear fission and nuclear fusion Both fission and fusion processes deal with matter and energy.
AN INTRODUCTION TO FISSION, FUSION, AND NUCLEAR POWER
The focus of this presentation are the processes of nuclear fission and nuclear fusion
Both fission and fusion processes deal with matter and energy
Previous studies have taught us that “matter and energy cannot be created nor destroyed”
We now need to understand that Matter and Energy are two forms of the same thing
The equation may be read as follows:
Energy (E) is equal to Mass (m) multiplied by the Speed of Light (c) squared
This tells us that a small amount of mass can be converted into a very largeamount of energy because the speed of light (c) is an extremely large number
Fission may be defined as the process of splitting an atomic nucleus into fission fragments
The fission fragments are generally in the form of smaller atomic nuclei and neutrons
Large amounts of energy are produced by the fission process
Fissile nuclei are generally heavy atoms with large numbers of nucleons
The nuclei of such heavy atoms are struck by neutrons initiating the fission process
Fission occurs due to electrostatic repulsion created by large numbers of protons within the nuclei of heavy atoms
U-235 + 1 Neutron
2 Neutrons + Kr-92 + Ba-142 + Energy
In this example, a stray neutron strikes an atom of U-235. It absorbs the neutron and becomes an unstable atom of U-236. It then undergoes fission. Notice that more neutrons are released in the reaction. These neutrons can strike other U-235 atoms to initiate their fission.
The fission process is a natural one. A French researcher found a natural uranium reactor in Gabon, West Africa; it has been estimated to be over 2 billion years old
Fission produces large amounts of heat energy and it is this heat that is captured by nuclear power plants to produce electricity
The fusion process generates tremendous amounts of energy; refer back to Einstein’s equation
For fusion to occur, a large amount of energy is needed to overcome the electrical charges of the nuclei and fuse them together
Fusion reactions do not occur naturally on our planet but are the principal type of reaction found in stars
The large masses, densities, and high temperatures of stars provide the initial energies needed to fuel fusion reactions
The sun fuses hydrogen atoms to produce helium, subatomic particles, and vast amounts of energy
Fission is a nuclear reaction in which a heavy atomic nucleus is split into lighter atomic nuclei
Fusion is a nuclear reaction in which 2 light atomic nuclei are combined into a single, heavier atomic nucleus
Chain reaction occurs when a Uranium atom splits
Atomic Bomb in a split second
Nuclear Power Reactor more controlled, cannot explode like a bomb
1938– Scientists study Uranium nucleus
1941 – Manhattan Project begins
1942 – Controlled nuclear chain reaction
1945 – U.S. uses two atomic bombs on Japan
1949 – Soviets develop atomic bomb
1952 – U.S. tests hydrogen bomb
1955 – First U.S. nuclear submarine
Program to justify nuclear technology
Proposals for power, canal-building, exports
First commercial power plant, England 1956
One million times as much energy in one pound of Uranium as in one pound of coal.Economic advantagesnotes
Nuclear energy annually prevents
5.1 million tons of sulfur
2.4 million tons of nitrogen oxide
164 metric tons of carbon
Nuclear often pitted against fossil fuels
Some coal contains radioactivity
Nuclear plants have released low-level radiation
17% of world’s electricity from nuclear power
U.S. about 20% (2nd largest source)
431 nuclear plants in 31 countries
103 of them in the U.S.
Built none since 1970s (Wisconsin as leader).
U.S. firms have exported nukes.
Push from Bush/Cheney for new nukes.
3% enriched Uranium pellets formed into rods, which are formed into bundles
Bundles submerged in water coolant inside pressure vessel, with control rods.
Bundles must be SUPERCRITICAL; will overheat and melt if no control rods.Reaction converts water to steam, which powers steam turbine
Reactor’s pressure vessel typically housed in 8” of steel
36” concrete shielding
45” steel reinforced concrete
Low-level wastes in commercial facilities
Spent fuel in pools or “dry casks” by plants
Nuclear lab wastes
Hanford wastes leaked radiation into Columbia River
High-level underground repository
Yucca Mountain in Nevada to 2037
Wolf River Batholith in Wisconsin after 2037?
Risks of cracks in bedrock, water seepage
Disposal of radioactive waste from nuclear power plants and weapons facilities by recycling it into household products.
In 1996, 15,000 tons of metal were received by the Association of Radioactive Metal Recyclers . Much was recycled into products without consumer knowledge.
Depleted Uranium munitions for military.
Nuclear waste contains high levels of radioactive waste, which are active for hundreds of thousands of years.
The controversy around nuclear energy stems from all parts of the nuclear chain.Summary notes