Nuclear Energy David Rude Unit 7 – Chapter 9, Part 2 Nuclear Energy David Rude

Non-Renewable Energy Sources Diablo Canyon Nuclear Power Plant

Outline 9.5 Nuclear Power 9.6 The Nature of Nuclear Energy 9.7 Nuclear Chain Reaction 9.8 Nuclear Fission Reactors

Outline 9.9 The Nuclear Fuel Cycle 9.10 Issues Related to the Use of Nuclear Fuels

9.5 Nuclear Power Nuclear power is fueled by uranium Obtained from mining Non-renewable. Word energy sources in order of importance: Oil Coal Natural gas Hydroelectric Nuclear Fifth most important

9.5 Nuclear Power Main reasons for opposing nuclear power: Threat to world peace This group opposes all things nuclear Environmental concerns due to potential nuclear contamination Problem of waste disposal

9.5 Nuclear Power Two reasons for renewed interest The threat of climate change Does not produce carbon dioxide Many now see it as a continuing part of the energy equation Economics Increased cost of oil and natural gas makes nuclear more attractive

9.5 Nuclear Power World’s energy production: 14% of world-wide electrical output 5½% of all power consumed

9.5 Nuclear Power As of 2011 440 nuclear power reactors in operation 61 under construction in 13 countries 169 nuclear power plants currently planned Most in Asian countries Breakdown: 85 in China, India, Japan and South Korea 14 in Russia 7 in US

9.5 Nuclear Power 19 Countries get 20% or more of electricity from nukes US – 20% Japan – 30% France – 75% Original operation licenses were for 40 years Most are being extended to 60 years Delays decommissioning for 20 years No new plants needed to replace lost capacity

9.6 The Nature of Nuclear Energy Atoms Basic building blocks of matter Element Cannot be divided into any other type of matter Oxygen, carbon, hydrogen, iron, and aluminum 90 naturally occurring kinds 25 types made by scientists

9.6 The Nature of Nuclear Energy Compound Matter made up of two or more types of atoms Examples Water, steel, oil, plastic

9.6 The Nature of Nuclear Energy Three basic parts Protons – positive charge Neutrons – no charge Electrons – negative charge Heald together by Nuclear force

The Nature of Nuclear Energy Radioactive Nuclei of certain atoms are unstable and spontaneously decompose (break apart) Neutrons Electrons Protons Other larger particles Great deal of energy

When atoms decay and release particles Become a different type of atom Example: U-238

The Nature of Nuclear Energy Radioactive Half-Life Time it takes for half the radioactive material to spontaneously decompose Isotope: An atom with the same number of protons, but different numbers of neutrons Isotopes are different forms of a single element.

The Nature of Nuclear Energy Carbon C12 – 6 Protons, 6 Neutrons Stable 98.8% C13 – 6 Protons, 7 Neutrons 1.1% C14 – 6 Protons, 8 Neutrons Unstable – 5,730 year half-life Years Amount 1 g 5,730 0.5 g 11,460 0.25 g 17,190 0.125 g C14 Half Life

The Nature of Nuclear Energy Iodine 37 known isotopes I-127 is only stable isotope 53 Protons 74 Neutrons Iodine-131 78 Neutrons Used in Medicine 8 day half-life Emits beta radiation (electrons) Days Amount 4 mCi 8 2 mCi 16 1 mCi 32 .5 mCi Dental X-Ray = 2-3 millicuries

p. 215

p. 215

The Nature of Nuclear Energy Radiation Energy released from the nucleus during nuclear disintegration Three basic types of radiation Alpha Two neutrons and two protons Stopped by sheet of paper Beta radiation Electrons Stopped by layer of clothing, glass or aluminum

The Nature of Nuclear Energy Gamma radiation Electromagnetic radiation

The Nature of Nuclear Energy Nuclear fission Neutrons hit and split the nuclei of certain other atoms Fissionable Atoms that can split easily Nuclear chain reaction Splitting nuclei release neutrons These strike more nuclei releasing more neutrons Cascading effect

The Nature of Nuclear Energy Nuclear fission chain reaction

The Nature of Nuclear Energy Atoms suitable nuclear chain reaction Two most common Uranium-235 Plutonium-239. Must be a certain quantity of nuclear fuel (critical mass)

9.8 Nuclear Fission Reactors Nuclear reactor A device that permits a controlled fission chain reaction U-235 is fuel Fissionable: element whose nucleus will split apart

The Nature of Nuclear Energy Nuclear fission chain reaction

Nuclear Fission Reactors Control rods Made of a non-fissionable material (boron, graphite) Absorb neutrons to control rate of fission Rate slows when inserted Rate increases when withdrawn Moderator Substance that absorbs energy Slows neutrons Enables them to split the nuclei of other atoms more effectively

Nuclear Fission Reactors Core coolant Material used to transfer heat away from the core Prevents overheating and melting of reactor casing Usually water

Nuclear Fission Reactors A nuclear reactor serves the same function as a fossil-fuel boiler Produces heat Heat converts water to steam Steam turns a turbine Turbine spins a giant coil of wire between to large magnets

Nuclear Fission Reactors Three most common types of reactors 20% Boiling-Water 60% Pressurized-Water 10% Heavy-Water Uses Deuterium Hydrogen stable isotope (1 proton, 1 neutron) Boils at higher temperature Gas-Cooled Reactors are not popular No new plants being constructed

Nuclear Fission Reactors Boiling-water reactor Steam forms in reactor and turns turbine Disadvantages Steam must be treated to remove any radiation Some radioactive material is left in the steam Generating building must be shielded

Nuclear Fission Reactors Boiling water reactor

Nuclear Fission Reactors Pressurized water reactor Water is pressurized so it doesn’t form steam Secondary loop transfers the heat from the pressurized water in the reactor to a steam generator. Advantages/Disadvantages Less waste radiation Increased costs of construction Easier maintenance due to radiation being contained

Nuclear Fission Reactors Pressurized-water reactor

Nuclear Fission Reactors Heavy-water reactor Basically same as Pressurized Water Reactors Uses water with deuterium instead of regular hydrogen Normal Hydrogen: one Proton and Electron – no neutron Deuterium: one proton, neutron and electron A stable isotope of hydrogen Not radioactive

Nuclear Fission Reactors Advantages Heavy water is a better moderator than regular water Moderator slows free neutrons more efficient at splitting nuclei Cheaper to run since it can use regular uranium Uses naturally occurring U-238 instead of enriched U-235

9.8 Nuclear Fission Reactors Breeder reactors produce nuclear fuel as they produce electricity. Liquid sodium efficiently moves heat away from the reactor core. Hence they are called Liquid Metal Fast Breeder Reactors. A fast moving neutron is absorbed by Uranium-238 and produces Plutonium-239 P 239 is fissionable fuel. Most breeder reactors are considered experimental. Because P239 can be used in nuclear weapons, they are politically sensitive.

Investigating Nuclear Alternatives Breeder reactors Produce nuclear fuel as they produce electricity Plutonium Requires fast moving neutrons Cannot use water as a moderator Lots of heat is generated Uses liquid metal as core coolant Usually sodium Also called Liquid Metal Fast Breeder Reactors Most considered experimental

Investigating Nuclear Alternatives Formation of Pu-239 in a breeder reactor

Investigating Nuclear Alternatives Problems Produce Plutonium-239 Very hazardous to humans Can be used in nuclear weapons Very dangerous to operate If liquid sodium boils it can damage reactor and lead to a nuclear accident. Liquid sodium must be at 620oC so it requires very specialized equipment. When shut down sodium becomes a solid

Investigating Nuclear Alternatives Can be difficult to operate because the reaction occurs so rapidly Most have been shut down Currently Only operating in Russia, China, & Japan Russia and India plan to build new ones

Investigating Nuclear Alternatives Nuclear fusion Two lightweight atomic nuclei combine to form a heavier nucleus Releases large amount of energy Fusion occurs in stars like our sun. Currently not possible provide a reliable source of energy with fusion Governments provide little funding for fusion research