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Nuclear Power

Nuclear Power Dennis Silverman, U C Irvine In the US, 20% of our electricity is produced by nuclear power. There are 103 US nuclear power plants. California related reactors Diablo Canyon, two reactors San Onofre, two reactors ⅓ of Palo Verde 1, 2, & 3 in Arizona California Nuclear energy

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Nuclear Power

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  1. NuclearPower Dennis Silverman, U C Irvine In the US, 20% of our electricity is produced by nuclear power. There are 103 US nuclear power plants.

  2. California related reactors Diablo Canyon, two reactors San Onofre, two reactors ⅓ of Palo Verde 1, 2, & 3 in Arizona

  3. California Nuclear energy • Each of the five reactors produces about 1,100 million watts (megawatts) of electricity • This is enough to power one million homes per reactor • Each reactor’s production is equivalent to 15 million barrels of oil or 3.5 million tons of coal a year. • The total 5,500 reactor produced megawatts is out of a peak state electrical power of 30,000 – 40,000 megawatts.

  4. Worldwide Nuclear Power Reactors • There are 440 nuclear power reactors in 31 countries. • 30 more are under construction. • They account for 16% of the world’s electricity. • They produce a total of 351 gigawatts (billion watts) of electricity.

  5. World Nuclear Power Plants

  6. Nuclear Electricity Production by Countries and Regions in Gigawatts (World Total 350 Gigawatts) and percent of electricity

  7. How a Nuclear Reactor works • 235U fissions by absorbing a neutron and producing 2 to 3 neutrons, which initiate on average one more fission to make a controlled chain reaction • Normal water is used as a moderator to slow the neutrons since slow neutrons take longer to pass by a U nucleus and have more time to be absorbed • The protons in the hydrogen in the water have the same mass as the neutron and stop them by a billiard ball effect • The extra neutrons are taken up by protons to form deuterons • 235U is enriched from its 0.7% in nature to about 3% to produce the reaction, and is contained in rods in the water • Boron control rods are inserted to absorb neutrons when it is time to shut down the reactor • The hot water is boiled or sent through a heat exchanger to produce steam. The steam then powers turbines.

  8. Nucleons more tightly bound in Fission Product Nuclei – Gives 200 Mev Energy per Fission

  9. Nuclear Fission from Slow Neutrons and Water Moderator

  10. Inside a Nuclear Reactor • Steam outlet  • Fuel Rods  • Control Rods 

  11. Energy Taken out by Steam Turbine

  12. Production of Plutonium (Pu) in Nuclear Reactors • 239Pu is produced in nuclear reactors by the absorption of a neutron on 238U, followed by two beta decays • 239Pu also fissions by absorbing a thermal neutron, and on average produces 1/3 of the energy in a fuel cycle. • 239Pu is relatively stable, with a half life of 24 thousand years. • It is used in nuclear weapons • It can be bred for nuclear reactors

  13. Nuclear Weapons to Reactor Fuel • We are buying highly enriched uranium (20% 235U) from the former Soviet Union’s nuclear weapons for 20 years from 1993--2013 • Converting it to low enriched uranium (3% 235U) for reactor fuel • It will satisfy 9 years of US reactor fuel demand • It comes from 6,855 Soviet nuclear warheads so far

  14. Nuclear Plant Future • The countries of the world are each planning their own course of nuclear plant development or decline • Nuclear power is competitive with natural gas • It is non-polluting • It does not contribute to global warming • Obtaining the fuel only takes 5% of the energy output • Plant licenses have been extended from 20 years to an additional 20 years

  15. Nuclear Plant Future • Newer designs are being sought to make them more economical and safer • Preapproval of a few designs will hasten development • Disposal of high level radioactive waste still being studied, but scientists believe deep burial would work • Because they are have large electrical output, their cost at $2 billion is hard to obtain and guarantee with banks • Replacing plants may be cheaper using the same sites and containment vessels

  16. Nuclear Problems and Solutions • Three Mile Island 1979 • 50% core meltdown, stuck valve with no indicator released water, but containment vessel held • More sensors added, better communication to experts in Washington, don’t turn off emergency cooling • 28 year US safety record since accident • Chernobyl 1986 • Human stupidity turned off cooling system • Poor steam cooling reactor design allowed unstable steam pocket to explode • Graphite caught fire • Design not used in other countries

  17. Yucca Mountain Project: Nuclear Fuel and High Level Waste Repository • Much more secure repository than leaving high level waste at 60 reactor sites around the country. • On old atomic bomb testing base, inside a mountain. • The storage is above the water table. • The Yucca Mountain site would be 60% filled by present waste. • US has legal commitment to the reactor industry. • Site has been studied extensively by scientists for over 20 years. • Will store waste during its 10,000 year decay time. • Questions of how to deflect dripping water around and under the storage vessels. • Questions of radioactive decay weakening storage containers. • A solution would be to build containers that can be opened and reincased, or to which surrounded casings could be added.

  18. Liquid Metal Fast Breeder Reactor • Uses the fast neutrons from 235U fission on surrounding 238U to produce 239Pu • In 10-20 years, enough Pu is produced to power another reactor • No moderators are allowed • No water, must use liquid sodium coolant • U must be at 15%-30% enrichment to generate power with fast neutrons while breeding Pu • This is at weapons grade enrichment, however • Super-Phenix in France has operated for 20 years

  19. Nuclear Power Proposed Solution? • Richard Garwin , MIT and industry propose: • If 50 years from now the world uses twice as much energy, and half comes from nuclear power • Need 4,000 nuclear reactors, using about a million tons of Uranium a year • With higher cost terrestrial ore, would last for 300 years • Breeder reactors creating Plutonium could extend the supply to 200,000 years • Nonpolluting, non-CO2 producing source • Need more trained nuclear engineers and sites • Study fuel reprocessing, waste disposal, and safer designs. • While nuclear reactors have to be on all day and night, and power use is less at night, they could be used to charge up electric cars. • Until electric cars or a hydrogen generation economy, they might only be used for the 40% of generation used at night, up from the present 20% that they generate.

  20. Fusion Reactors • Fusion easiest for Deuteron (D) + Tritium(T): D(p,n) + T(p,nn) → 4He(pp,nn) + n in a high temperature plasma. • Replacement T created from Li blanket around reactor n + 6Li → 4He + T • Fusion reactors • International ITER in 2012 for research for a decade, costing $5 billion • Current stalemate over siting in France or Japan • Followed by DEMO for a functioning plant, taking another 10 years. • Design and completion of a commercial plant not until 2050. • US Lithium supply would last a few hundred years. • Still would be a radioactive waste disposal problem.

  21. International Thermonuclear Experimental Reactor (ITER)

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