Nuclear Power Physics /7/03

Outline  The Nucleus  Radioactivity  Fission  Fusion  Nuclear Weapons  Nuclear Power

Nucleus  Composed of protons and neutrons  239 Pu 94 or Pu – 239  94 protons  145 neutrons  Isotope of Plutonium

Radioactivity  Some isotopes are unstable  Spontaneously Decay  Decaying isotopes emit particles

Radon is a health hazard  Product of the decay of naturally occurring uranium  Affects indoor air quality  2 nd leading cause of lung cancer  Regional issue

Half-life  Pu-239 decays to U- 235 with the emission of an alpha particle:  The time for half of the Pu-239 nuclei to decay is called the half-life.  24,000 years is half- life for Pu-239 decay

Aside: Pathetic Joke  Did you hear about the socially sophisticated physicist?.  He was the half-life of the party.

Fission  By bombarding a nucleus with neutrons, a stable isotope can be induced to fission or split.  U-235 is an example of a fissionable material.  The release of neutrons in this reaction means that we can set up a chain reaction

Fission Releases Energy  When the fission is controlled, as in a nuclear reactor, it can be a practical source of power.  When the fission is uncontrolled it can be the basis for weapons of mass destruction.

Fusion  Two light nuclei combine to form a heavier nucleus.  The fusion of deuterium (a hydrogen isotope) with tritium (another hydrogen isotope) to form a helium nucleus can release a great deal of energy.

Fusion Power  Using a fission bomb as a trigger, a hydrogen bomb, or a H-bomb uses fusion to create a WMD.  Solar energy originates as fusion energy in the sun’s interior.  Fusion power is an active area of research.

Nuclear Weapons  First nuclear weapon tested at Trinity site in 1945 used Pu-239.  The fuel for the Hiroshima and Nagasaki bombs were U-235 and Pu-239, respectively.  First H-bomb test in 1952

Nuclear Weapons CountryStrategicTacticalTotal United States7,3003,200-4,70010,500-12,000 Russia6,0007,000-15,00013,000-20,000 China France United Kingdom India Israel Pakistan Global Total--24,700-33,507

Nuclear Reactors: Boiling Water Reactor (BWR)  Similar to coal plant: boils water, makes steam, steam drives turbine, turbine turns electrical generator  Fissioning of U-235 is the fuel.

BWR Components  Containment building prevents release of radiation  Water is needed as coolant and to prevent meltdown.

Nuclear Reactor is a Heat Engine  Efficiency is similar to a coal burning plant, about 33%  So, 2/3 of the released energy is waste heat.

Uranium Fuel  Only 0.7% of natural U is U-235.  U-238 is not fissionable.  U must be enriched to 2.8% U-235.

Uranium Fuel Supply  Worldwide U-235 resource does not offer a long-term energy solution.  Breeder reactor consuming U-235 can convert U-238 into Pu- 239.

Plutonium Economy  Breeder reactors would greatly increase the availability of weapons-grade Plutonium.

Nuclear Power in the US  104 nuclear plants  Produce 20% US Electricity  No new plants since 1973  Why?

Nuclear Accidents  1979 Three Mile Island partially core melt  1986 Chernobyl explosion and fire, release of radiation

Waste Disposal  WIPP near Carlsbad, NM. Stores hi-level waste associated with nuclear weapons  Yucca Mountain, Nevada. High-level waste from commercial reactors.

Will there be a nuclear renewal?  Economics do not look good. Very capital intensive.  Fear of terrorism  Anti-nuclear groups  Waste disposal