GEOL-1010 Lecture Notes - Lecture 11: Cooling Tower, Control Rod, Chain Reaction

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5 Feb 2018
Lecture 11.2: Nuclear
Geology in the News
o Australian lakes turning pink
o Warmer weather causes water to evaporate so the salt concentration is getting higher, one
type of algae is thriving in this which is causing the bright pink color
Part two- Nuclear Energy
o Fission-getting an atom to split a part
o Very energetic process, releases a large amount of energy
o Releases a lot of energy (radiation)
o Have to harness the energy safely
Nuclear Fuel
o Uranium ore
o High deposit of uranium
o Ore- rock or layer of sediment that has a high concentration of something valuable
o Want to extract the uranium from the rock or sediment
o First step produces
o Yellowcake-processed uranium ore
o Not ready for use yet, its just the first step
o Next step is to separate the uranium by isotope
o U isotopes (235U vs 238U) separated
o You want 235U
o Want the fuel enriched in 235U rel to 238U
o Get rid of some of the 238
o How much you want to enrich depends on what you’re using it for
Powerplants- 3-5% enrichment
Weapons- 90% enrichment
You can see what people are using uranium for
Why is 235U Needed?
o Firing nos takes time and energy
o Fire neutrons into your fuel cell, causes them to undergo fission and give off a
bunch of energy
o As a byproduct you get 3 more neutrons, those three neutrons fly off into different
directions and hit 3 more neutrons, which then break up into 3 etc….. a chain
o Splitting 235U atoms starts a chain reaction
o This means you can just leave the chain reaction to do its own thing
o Spending less money and energy since you don’t have to keep firing the neutron
o Without the 3 neutron byproduct you have to keep doing it yourself
o Once you get the fission chain reaction started it keeps going you don’t have to force it
Nuclear Power- Generation
o This can get out of control and have a meltdown
o Chain reaction is controlled
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o Control rods- can be inserted into the reactor and will sort of neutrons. If the
reaction is happening too quickly you can slow it down by inserting a control rod.
Similar to hitting the breaks on a car
o Cooling system removes the heat energy
o Blue pathway= coolant moving through to absorb heat energy which is moved
somewhere else in the power plant to generate energy
o Usually the coolant is just water, when it heats up it can be converted to steam very
easily which is great to use to generate energy
o Requires lots of water
o To keep coolant system going
o 4 million gal/ year in some plants
o the tower in the picture is not a reactor, the tower is a cooling tower. Its wear a lot
of the water is stored and can cool back down before you put it back in the lake.
The stuff coming out of the tower is literally just water vapor caused by the water
temperature dropping
Nuclear Advantages
o 1. Large US Reserve
o Est. 130+ year supply of uranium assuming current production rate
o 2. Reduce C emissions
o process doesn’t generate a lot of carbon emissions unlike fossil fuels
o we’re not burning anything here so there isn’t greenhouse gases built
o 3. Decrease fossil fuel dependence
o 4. Produces tremendous amounts of energy
o 1kg of U produces 3 million times more energy than 1 kg of coal
o 5. Good safety record***
Current US Use
o ~100 plants, ~20% of US Electricity
o Use declining since 1996
o About half of the active plants are on the verge of shutting down- most will close by 2020
o No new reactors ordered between 1978-2010
o We went through a 30 year period where not a single new nuclear plant was
approved for construction anywhere in this country
o 48% of the ones ordered before ’78 were never built
Nuclear Disadvantages
o 1. Nuclear electric price tripled between 1970-1990
o 2. Reactor safety
o 3. Nuclear proliferation
o If you’re using more and more uranium, there is a better chance its going to get
used improperly and end up in the wrong hands
o 4. Nuclear waste disposal
o there are other byproducts
o a lot of those byproducts are radioactive which is not good
Radioactive Waste
o Average power plant creates 25-30 tons of waste per year
o 2007: US has 50,000 tons of stored radioactive waste
o Radiation levels vary, so safety protocols also vary
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