Nuclear Fission & Fusion

Transcription

1 Nuclear Fission & Fusion

2 Binding Energy For energy release in fusion or fission, the products need to have a higher binding energy per nucleon (proton or neutron) than the reactants. As the graph above shows, fusion only releases energy for light elements and fission only releases energy for heavy elements.

3 Binding Energy It takes energy to break up an atom. Energy must be put into a system to break it apart. That energy is converted to mass. That energy is called the Binding Energy. E b = (Zm p + Nm n M A ) x MeV/u The masses are expressed in atomic mass units. Add the atomic mass of the electron to the proton.

4 Binding Energy per Nucleon The most stable atoms have the most Binding Energy per nucleon. Radioactive Atoms mutate by fission or fusion until they have maximum Binding Energy per nucleon which occurs at Iron.

5 Mass per Nucleon The smaller the mass per nucleon, the greater the binding energy. Elements fission down or fuse up to Iron, the most stable element, releasing energy by E = Δmc 2. Fusion Fission

6 SRJC Environmental Forum Welcomes You to Nuclear Power Is it Green, Cheap & Safe? Presented by Lynda Williams SRJC Physics

7 "Of all our nation's energy sources, only nuclear power plants can generate massive amounts of electricity without emitting an ounce of air pollution or greenhouse gases... We will start building nuclear power plants again by the end of this decade." - President George Bush, August, 2005

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9 Global Warming due to increasing Greenhouse Gases (GHG)

10 We have no time to experiment with visionary energy sources; civilisation is in imminent danger and has to use nuclear - the one safe, available, energy source - now or suffer the pain soon to be inflicted by our outraged planet. James Lovelock, Author of Gaia Hypothesis Published in The Independent - 24 May 2004

11 Nuclear energy is the only non-greenhouse gas-emitting power source that can effectively replace fossil fuels and satisfy global demand. -Patrick Moore, Co-founder, Greenpeace, Statement to US Senate Committee on Energy & Natural Resources, April 28, 2005

12 Most CO2 is produced by Transportation Transport contributes well over 30% of total world emissions of carbon dioxide. Nuclear Power only produces electricity and cannot reduce CO2 emissions produced by transportation.

13 Nuclear power is "environmentally friendly, affordable, clean, dependable and safe." - Christie Whitman, former E.P.A. chief.

14 NYT, WASHINGTON, April 24 The nuclear industry has hired Christine Whitman the former administrator of the Environmental Protection Agency, and Patrick Moore, a co-founder of Greenpeace, the environmental organization, to lead a public relations campaign for new reactors.

15 Nuclear Energy Institute

16 Nuclear Power Is it Green?

17 Nuclear Fission Heavy elements FISSION into lighter elements, releasing energy in the process by E = Δmc 2, where Δm is the difference in mass between the parent and products. About 250 MeV is released in this reaction in the form of kinetic energy of the products. No green house gases are directly released in the nuclear fission reaction.

18 Fission Described by the Liquid- Drop Model Diagram (a) Approach (c) Oscillation (b) Absorption (d) Fission

19 Critical Mass Chain Reaction Critical Mass: the minimum amount of fissionable material to produce self-sustained chain reaction, a condition called criticality. In a nuclear power plant, the critical chain reaction must control the neutron flux to avoid an exponential increase in fissions, going supercritical. In a nuclear bomb, you want a supercritical chain reaction.

20 K Values The reproduction constant K is defined as the average number of neutrons from each fission event that will cause another fission event When K = 1, the reactor is said to be critical The chain reaction is self-sustaining When K < 1, the reactor is said to be subcritical The reaction dies out When K > 1, the reactor is said to be supercritical A run-away chain reaction occurs

21 Fissile Material of Choice U-235 & P-239 Odd number of nucleons is easier to fission U-235: MeV more energy than U-238 Uranium: 238 U is >99% in nature 235 U is ~0.7% in nature. Fuels are generally enriched to at least a few percent 235 U Plutonium: 239 Pu is not found in nature, it is reprocessed from nuclear power plant waste or bred from uranium in breeder reactors

22 Pressurized Water Reactor (PWR) U-235 absorbs slow neutrons they are slowed down by water the neutrons become thermalized. Control rods absorb neutrons and moderate the chain reaction. A meltdown can happen if they fail.

23 Cooling Towers Reactor

24 Current Status 443 plants world wide (16% energy), 103 in the US (20% energy)

25 It is True... No green house gases are directly released in the nuclear fission reaction. But what about during the ENTIRE fuel cycle?

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27 Uranium Mining Uranium is mined as ore from open pits or deep shaft mines. High grade ores yield 10 kg uranium per tonne rock. World Nuclear Power Plants need 67,000 tonnes of natural uranium per year 67,000,000 tons of rock!

28 Uranium Miner "I used to go in and haul the rocks out, and I guess that's where I got hurt, because there was a lot of dust after they did the blasting and we went in right away." - Bernard Benally Red Rock Navajo Reservation, Arizona

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30 Through a series of chemical leaching processes, crushed ore is transformed into a powdered concentrate called yellowcake. Most of the ore that goes into the mill exists as waste, which contains 85% of the ore's original radioactivity.

31 Uranium Mill Tailings The rock containing Uranium is crushed into a fine sand. After the uranium is chemically removed, the sand is stored in huge reservoirs. These left-over piles of radioactive sand are called "uranium tailings".

32 Uranium Mill Tailings By 1989, some 140 million tons of mill tailings have accumulated in the United States alone, with 10 to 15 million tons added each year. Although their radiation is generally less concentrated than other types of waste, some of the isotopes in these tailings are long-lived and can be hazardous for many thousands of years.

33 Atlas Mines Tailing Pile 10.5 million tons of uranium mill wastes including 426 million gallons of highly-contaminated liquid. An Oak Ridge National Laboratory study shows that the steady rate of uranium tailing contaminant leakage into the Colorado River is estimated at 9,648 gallons per day.

34 Uranium Tailings at Elliot Lake Ontario 130 million tons radioactive for hundreds of thousands of years

35 Uranium Mill Sites

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37 In-Situ Leach Mining At an ISL site, a series of wells are drilled into the orebody. Millions of litres of strong acid or alkaline solution are then injected directly into the groundwater, stripping the uranium from the host rock and mixing it into the water. In the center of a circle of injection wells, a production well sucks most of the uranium bearing water up to the surface and pipes it into a processing plant where the uranium is recovered and the wastes are dealt with by either moving them elsewhere or pumping them back into the ground and thereby polluting the groundwater.

38 Nuclear Energy Institute Educational Website for Kids In-Situ Leach Mining

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40 Purified Yellow Cake in Aqueous Solution converted into Uranium Hexafluoride gas UF 6 Uranium Refiner, Blind River, Ontario, Canada.

41 Storing hexafloride (UF6) waste in cylinders requires constant monitoring because the estimated lifetime of cylinders is measured in decades, whereas the half-life of U- 238 is 4.5 billion years, and UF6 is highly unstable.

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43 Enriching Uranium Uranium: 238 U is >99% in nature 235 U is ~0.7% in nature Naturally occurring Uranium must be enriched to ~5% 235 U for nuclear power plants Enrichment methods Gas centrifuge (Now in Iran and formerly found in Iraq) Gaseous diffusion (used in USA) Electromagnetic isotope separation uses strong magnetic field to deflect ions of lighter isotope farther than heavier isotope

44 Gaseous diffusion Thousands of diffusion filters needed

45 Filter U-235 from U-238 through miles of filters Portsmouth, Ohio, Gaseous Diffusion Plant operating around the clock, consuming in 1 day as much electricity as a city of the size of Sacramento or Memphis, Tennessee.

46 Depleted Uranium After isotope separation, the remaining 238 U is said to be depleted as it is missing 235 U however, 238 U is radioactive Uranium is a very dense metal (1.7 x Pb), making it ideal for use in armor and shell casings DU Used in Recent Wars: Balkans: 200 Tons Afghanistan: 800 Tons Gulf War 1: 350 Tons Iraq War: 200 tons???

47 CFC is a GHG The enrichment of uranium fuel for nuclear power uses 93 percent of the refrigerant chlorofluorocarbon (CFC) gas made annually in the United States. CFC compounds are also potent global warming agents 10,000 to 20,000 times more efficient heat trappers than carbon dioxide, which itself is responsible for 50 percent of the global warming phenomenon.

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49 U-235: Converting the Gas into a Green salt and then into Metal Uranium is shipped to Fernald from the Portsmouth plant as a gel. It is heated into gas in these three autoclave vaporizers. The gas is converted into green salt and then into metal for fuel fabrication. Feed Materials Production Center, Fernald, Ohio.

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51 These pellets of enriched uranium will be sealed inside ft metal fuel rods to generate electricity in a nuclear reactor.

52 Nuclear Fuel Rods A typical 100 MW reactor contains 50,000 fuel rods containing more than 100 tons of uranium.

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54 Cooling Towers Reactor

55 Nuclear Power Plants Need Water LOTS of Water. 100,000 gallons per minute are pumped to one or more Cooling Towers, consuming million gallons of water per day. An equally huge volume of wastewater is discharged at temperatures up to 25 F hotter than the water into which it flows. Indigenous marine life suited to colder temperatures is eliminated or forced to move, disrupting delicately balanced ecosystems. Nuclear power plants discharge a significant amount of tritium as part of their routine operations; sometimes more is discharged as a result of mishaps and incidents. There have been 10 reported tritium leaks at US nuclear power plants in the last decade.

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58 SAN ONOFRE NUCLEAR GENERATING STATION Seawater for cooling: up to 2.4 billion gallons daily Once-through cooling is contributing to declining fisheries and the degradation of estuaries, bay and coastal waters. These (power) plants indiscriminately 'fish' the water in these habitats by killing the eggs, larvae and adults when water drawn from the natural environment flows through the plant analysis completed for the CA Energy Commission

59 Water Vapor is a GHG! The most powerful greenhouse gas in the atmosphere is water vapour... Just a rise of 1% of water vapour could raise the global average temperature of Earth's surface more then 4 degrees Celsius. -Andrew E. Dessler, Texas A & M University -Vladimir Shaidurov, Russian Academy of Sciences The Science and Politics of Global Climate Change

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61 After three or four years in a reactor, the pellets will become inefficient for producing electricity and the fuel rods will be removed from the reactor. After removal, the fuel rods (now called spent nuclear fuel) will be highly radioactive, requiring safe long-term disposal. Present nuclear power plants utilise only 0.7 per cent of uranium and the remaining 99.3 per cent is the spent fuel Plutonium, which remains highly radioactive for over 10,000 years in the storage.

62 Nuclear Waste 250,000 tons of Spent Fuel Rods 10,000 tons made per year in US

63 The radioactive reactor building must also be decommissioned after years of operation, taken apart by remote control and similarly transported long distances and stored. GHG will be produced in the process. (The cost is paid by US taxpayers!)

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65 Nuclear Waste Disposal Yucca Mountain, Nevada 77,000 Tons of High Level Waste

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67 Fraud at Yucca Mountain

68 Yucca Mountain

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70 THE RODS ARE FULL OF PLUTONIUM! Plutonium:Nuclear Power By-Product Each 1000 megawatt nuclear power plant produces 500 lbs of Pu per year. Global production due to nuclear power plants: ~1,200 tons Global production due to nuclear weapons: 250 tons. 5 kg in an atomic bomb!

71 Reprocessing the Hot Rods

72 Reprocessing Plutonium 239 Pu is a waste product in nuclear power reactors, that is intermixed with other spent reactor fuels. In order to become weapons grade, it must be separated out ( reprocessed )

73 Reprocessing Plutonium Spent reactor fuel is chopped up, by remote control, behind heavy lead shielding. Chopped-up pieces are then dissolved in boiling nitric acid, releasing radioactive gases in the process. Pu is chemically separated from the acid solution, leaving large quantities of high-level radioactive liquid waste and sludge behind. After it has cooled down for several years, the liquid waste is solidified for ultimate disposal, while the separated Pu is fabricated into nuclear fuel or nuclear weapons.

74 Nuclear Processing Plant Accident 1999, Tokai, Japan: Uranium Processing Plant converts enriched uranium hexafluoride (UF 6 ) to uranium dioxide (UO 2 ) (MOX). A Criticality accident involved a self-sustaining chain reaction caused from handling of too large amounts of enriched uranium. The chain reaction continued for around 20 hours, before it could be stopped, releasing large amounts of gamma and neutron radiation. 1 worker died.

75 Reprocessing Spent Fuel Rods

76 The PROBLEM Iran, North Korea, India: Every Nuclear Power Plant is a source for atomic weapons. There is no civilian nuclear power. Nuclear Power must have military protection because of the plutonium.

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79 In sum.is nuclear power green? A complete life-cycle analysis shows that generating electricity from nuclear power emits 20-40% of the carbon dioxide of a gas-fired system when the whole system is taken into account. Nuclear Power: The Energy Balance by Jan-Willem Storm van Leeuwen and Philip Smith, Center for Energy Conservation, Netherlands

80 High Grade Ore is a Limited Resource Known uranium reserves will last for about fifty years at the current consumption rate. If the nuclear share is increased to 10% of the current world energy supply by construction of 1000 new nuclear power plants (more than four times the current world nuclear capacity), the reserves will last for about fourteen years. If low grade ores of less than 0.1% are used (1 kg of U per ton of rock) the energy consumed to extract the one kg of uranium will surpass the amount of energy which can be generated from that kilogram in the nuclear system.

81 Nuclear Power Is it Cheap? To keep our economy growing, we also need reliable supplies of affordable, environmentally responsible energy including safe, clean nuclear energy. - President George W. Bush, State of the Union Address, 2006

82 The main reason that no U.S. energy company has constructed one since 1973 is not public opposition, licensing, uncertainties, lack of licensed geological repository for spent fuel disposal, or proliferation risks, but rather that new commercial nuclear power plants are uneconomical because of their higher construction costs. Natural Resources Defense Council Issue Paper on Commercial Nuclear Power

83 The Energy Policy Act of 2005 $14 billion in tax dollars, taxpayer-backed loans, and tax credits to build 6 new nuclear reactors. $2 billion line item to compensate nuclear corporations for any delay Price Anderson Act caps the industry s liability at $15 billion

84 Opposition to nuclear energy is based on irrational fear fed by Hollywood-style fiction, the Green lobbies and the media. James Lovelock, Author of Gaia Hypothesis Published in The Independent - 24 May 2004

85 Nuclear Power Is it Safe?

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87 Nuclear Weapons Proliferation Plutonium:Nuclear Power By-Product Each nuclear power plant produces ~500 lbs of Pu per year. Global production due to nuclear power plants: ~1,200 tons 5 kg in an atomic bomb! Nuclear Power increases risk of nuclear weapons PROLIFERATION!

88 Nuclear Accidents If you set aside Three Mile Island and Chernobyl, the safety record of nuclear [power] is really very good. -Treasury Secretary Paul O'Neill, June 2001

89 The 20 th Anniversary of the Chernobyl Nuclear Power Plant Disaster, April 26 th, 1986 Chernobyl reactor number 4 in Ukraine was ripped apart by an explosion on 26 April 1986, and burned for 10 days. It released a massive amount of radioactivity (10 18 becquerels) over Europe and the rest of the world.

90 Local Effects Evacuation of more than a thousand square miles 400 times more radiation released than Hiroshima Bomb 350,000 people dislocated Exclusion Zone is a permanent Ghost Town.

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94 Chernobyl released million curies of radioactivity into the atmosphere Average Background Radiation in Europe: 0.3 kbq/m 2 1 Curie = 10 Billion Bq

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96 Chernobyl Now

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98 The New Shelter

99 Chernobyl Consequences 600,000 exposed to high levels of radiation 6 million people exposed to low levels 56 deaths to date 4,000 cases of thyroid cancer to date 2 million officially classified as victims Increased rates of birth defects Hundreds of Billions of dollars in costs to date 9,000-90,000 cancer induced deaths will occur (Depending on who you re talking to.)

100 Can Chernobyl Happen Again? Is it worth the Risk?

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103 Fission & Fusion In either FISSION or FUSION, less stable atoms mutate to more stable atoms, releasing energy in the process by E = mc 2.

104 Fusion Light elements FUSE into larger elements, releasing energy in the process by E = mc 2.

105 Fusion in the Sun All stars generate energy through fusion The Sun, along with about 90% of other stars, fuses hydrogen Some stars fuse heavier elements Two conditions must be met before fusion can occur in a star: The temperature must be high enough The density of the nuclei must be high enough to ensure a high rate of collisions

106 Proton-Proton Cycle The proton-proton cycle is a series of three nuclear reactions believed to operate in the Sun Energy liberated is primarily in the form of gamma rays, positrons and neutrinos H+ H+ Then 1 1 H+ or He+ H H He H He e He + γ He e He+ + ν ν H+ 1 1 H

107 Fusion Fusion requires high temperature plasmas confined long enough to release appreciable fusion energy Confinement Method Heating Method Gravity Compression (gravity) Fusion Reactions (such as the p-p chain) Stars

108 Fusion Fusion requires high temperature plasmas confined long enough to release appreciable fusion energy Confinement Method Heating Method Inertial Compression (implosion driven by laser or ion beams, or by X-rays from laser or ion beams) Fusion Reactions (primarily D+T) Laser Beam Driven Fusioin

109 Fusion Fusion requires high temperature plasmas confined long enough to release appreciable fusion energy Confinement Method Heating Method Magnetic Electromagnetic Waves Ohmic Heating (by electric currents) Neutral Particle Beams (atomic hydrogen) Compression (by magnetic fields) Fusion Reactions (primarily D+T) Tokamak

110 Currently the largest fusion reactor is the 16 MW Joint European Torus (JET) which can sustain plasmas of a few megawatts for a few seconds. The new ITER (International Thermonuclear Experimental Reactor) fusion reactor is planned to be built in France at a cost of $16 Billion. ITER is a tokamak design. It will take 8 years to build and will run experiments for 20 years.

111 Cost of Fusion? Average US Budget for Fusion Energy per year over past 50 years: $250 Million x 50 years ~ $13 Billion so far 2008 Budget: Fusion Energy Science: $428 Million

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114 Problems with Fusion? Breeding it: Lithium is RARE! Cost: ~ $200 million/kg Need ~ 56kg/year for the ITER Breathing it:

115 Dangerous Neutrons DT fusion releases "fast neutrons." Fast neutrons turn everything they touch radioactive or busted. - Warren Smith

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