Fundamentals of nuclear power
Download
1 / 35

Fundamentals of Nuclear Power - PowerPoint PPT Presentation


  • 133 Views
  • Uploaded on

Fundamentals of Nuclear Power. Nuclear Fission. We convert mass into energy by breaking large atoms (usually Uranium) into smaller atoms. Note the increases in binding energy per nucleon. A slow moving neutron induces fission in Uranium 235. Fission products.

loader
I am the owner, or an agent authorized to act on behalf of the owner, of the copyrighted work described.
capcha
Download Presentation

PowerPoint Slideshow about 'Fundamentals of Nuclear Power' - tuvya


An Image/Link below is provided (as is) to download presentation

Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author.While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server.


- - - - - - - - - - - - - - - - - - - - - - - - - - E N D - - - - - - - - - - - - - - - - - - - - - - - - - -
Presentation Transcript

Nuclear fission l.jpg
Nuclear Fission

  • We convert mass into energy by breaking large atoms (usually Uranium) into smaller atoms. Note the increases in binding energy per nucleon.



Fission products l.jpg
Fission products

  • The fission products shown are just examples, there are a lot of different possibilities with varying probabilities


Expanding chain reaction l.jpg
Expanding Chain Reaction

  • The fission reaction produces more neutrons which can then induce fission in other Uranium atoms.

  • Mouse Trap Chain Reaction


Linear chain reaction l.jpg
Linear Chain Reaction

  • Obviously, an expanding chain reaction cannot be sustained for long (bomb). For controlled nuclear power, once we reach our desired power level we want each fission to produce exactly one additional fission


Tricks of the trade l.jpg
Tricks of the trade

  • Slow moving (thermal) neutrons are more effective at inducing fission, but, fissions produce fast moving electron. We need to slow neutrons down.

  • Fissions typically produce several neutrons but a linear chain reaction only needs one. We need to get rid of a good fraction of our neutrons.


Moderator l.jpg
Moderator

  • Neutrons are slowed down by having them collide with light atoms (Water in US reactors).

  • Highest level of energy transfer occurs when the masses of the colliding particles are equal (ex: neutron and hydrogen)


Control rods l.jpg
Control Rods

  • Control rods are made of a material that absorbs excess neutrons (usually Boron or Cadmium).

  • By controlling the number of neutrons, we can control the rate of fissions


Basic ideas l.jpg
Basic Ideas

  • The Uranium is both the fuel and the source of neutrons.

  • The neutrons induce the fissions

  • The Water acts as both the moderator and a heat transfer medium.

  • Control rods regulate the energy output by “sucking up” excess neutrons


Practicalities l.jpg
Practicalities

  • Processing of Uranium

  • Each ton of Uranium ore produces 3-5 lbs of Uranium compounds

  • Uranium ore is processed near the mine to produce “yellow cake”, a material rich in U3O8.

  • Only 0.7% of U in yellow cake is 235U. Most of the rest is 238U which does not work for fission power.




Enrichment l.jpg
Enrichment

  • To be used in US reactors, fuel must be 3-5% 235U.

  • Yellow cake is converted into UF6 and this compound is enriched using gaseous diffusion and/or centrifuges.

  • There are some reactor designs that run on pure yellow cake.


Slide17 l.jpg


Fuel pellets l.jpg
Fuel Pellets

  • The enriched UF6 is converted into UO2 which is then made into fuel pellets.

  • The fuel pellets are collected into long tubes. (~12ft).

  • The fuel rods are collected into bundles (~200 rods per bundle

  • ~175 bundles in the core


Cladding l.jpg
Cladding

  • The material that the fuel rods are made out of is called cladding.

  • It must be permeable to neutrons and be able to withstand high heats.

  • Typically cladding is made of stainless steel or zircaloy.


Controlling the chain reaction depends on l.jpg
Controlling the chain reaction depends on

  • Arrangement of the fuel/control rods

  • Quality of the moderator

  • Quality of the Uranium fuel

  • Neutron energy required for high probability of fission


Slide22 l.jpg



Other options l.jpg
Other Options Pressurized Water Reactor.

  • Other countries use different reactor designs.

  • Some use heavy water (D2O) as a moderator. Some use Graphite as a moderator.

  • Some are designed to use pure yellow cake without further enrichment

  • Liquid metal such as sodium or gasses such as Helium are possibilities to use for coolants


Breeder reactors l.jpg
Breeder Reactors Pressurized Water Reactor.

  • A big problem with nuclear power is the creation of Plutonium in the reactor core.

  • This is a long lived radioactive element that is difficult to store.

  • Q: Why not use it as a fuel too?


Basic idea l.jpg
Basic Idea Pressurized Water Reactor.

  • Process that creates the Pu.

  • During fission use one of the extra neutrons to create a Pu atom


Slide28 l.jpg

  • Somewhat difficult in that we want fast neutrons to “breed” the 239Pu out of the 238U, but we want slow neutrons to induce the fission of 235U.

  • Requires a different design of reactor.

  • Doubling time: Time required to produce twice as many 239Pu atoms as 235U destroyed. A good design will have a 6-10 doubling time.

  • There are no currently operating breeder reactors in the US.


Nuclear power in the us l.jpg
Nuclear Power in the US “breed” the

  • We currently generate approximately 20% of our electricity using nuclear power.

  • No new nuclear power plants have been “ordered” since the late 1970’s.

  • Even “new” plants are nearing 20 years old and will start to need replacing.


Us nuclear power plants l.jpg
US Nuclear Power Plants “breed” the


World nuclear power l.jpg
World Nuclear Power “breed” the


ad