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.
California related reactors Diablo Canyon, two reactors San Onofre, two reactors ⅓ of Palo Verde 1, 2, & 3 in Arizona
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.
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.
Nuclear Electricity Production by Countries and Regions in Gigawatts (World Total 350 Gigawatts) and percent of electricity
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.
Nucleons more tightly bound in Fission Product Nuclei – Gives 200 Mev Energy per Fission
Inside a Nuclear Reactor • Steam outlet • Fuel Rods • Control Rods
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
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
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
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
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
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.
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
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.
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.