Chapter 12Chapter 12

NuclearNuclear

PG&E BillPG&E Bill

PG&E WebsitePG&E Website

DefinitionsDefinitions

Combustion- Combustion-

Nuclear- Nuclear- Fission-Fission- Fusion-Fusion-

Nuclear reactions Nuclear reactions produce _______x produce _______x more than energy more than energy per atom than per atom than chemical reactionchemical reaction

The atomThe atom Atomic Mass- Atomic Mass-

Atomic Number-Atomic Number-

More DefinitionsMore Definitions IsotopesIsotopes- forms of a single element that differ in - forms of a single element that differ in

atomic mass (due to different # of neutrons)atomic mass (due to different # of neutrons) RadioisotopesRadioisotopes- unstable isotope that spontaneously - unstable isotope that spontaneously

emit a form of energy consisting of particles emit a form of energy consisting of particles (radiation)(radiation)

Radioactive Decay-Radioactive Decay- process of a radioisotope process of a radioisotope emitting radiation whose nucleus changes into the emitting radiation whose nucleus changes into the nucleus of a different element as a result of the nucleus of a different element as a result of the radiationradiation

Radioactive half-life-Radioactive half-life- period of time required for period of time required for one half of the total amount of a radioactive one half of the total amount of a radioactive substances to change into different material substances to change into different material (daughter product)(daughter product)

Nuclear power plants use fission.Nuclear power plants use fission.

Nuclear FissionNuclear Fission

Uses uranium as fuelUses uranium as fuel• Non-renewable resourcesNon-renewable resources• Found predominantly Found predominantly

in_______________________)in_______________________)

3 main uranium isotopes3 main uranium isotopes• U-238: U-238: • U-235:U-235:• U-234: U-234:

Fission ProcessFission Process

Enriched uranium (U-235) ore formed Enriched uranium (U-235) ore formed into pellets & placed in fuel rodsinto pellets & placed in fuel rods

Fuel rods put into fuel assemblies & Fuel rods put into fuel assemblies & placed in reactor vesselplaced in reactor vessel

Reaction controlled by control rodReaction controlled by control rod In fission process, U-235 is bombarded In fission process, U-235 is bombarded

w/ neutrons which splits the atom w/ neutrons which splits the atom releasing energy & daughter productreleasing energy & daughter product

Energy is in form of Energy is in form of heat => used to form heat => used to form steam & generate steam & generate electricity (steam electricity (steam turns turbine which turns turbine which turns generator which turns generator which makes electricity)makes electricity)

Fission occurs in Fission occurs in reactor corereactor core

Condenser used to Condenser used to cool steamcool steam

http://reactor.engr.wisc.edu/pics/reachttp://reactor.engr.wisc.edu/pics/reactor2.giftor2.gif

Water coolingWater cooling

3 water circuits3 water circuits• Primary (closed)- Primary (closed)- • Secondary (closed)-Secondary (closed)-• Tertiary-Tertiary-

Reactor vessel and generator/water Reactor vessel and generator/water system are in containment buildingsystem are in containment building

Breeder Nuclear FissionBreeder Nuclear Fission

Alternate type of nuclear fissionAlternate type of nuclear fission Uses U-238 and changes it into Pu (plutonium) Uses U-238 and changes it into Pu (plutonium)

-239 to use as a fuel in the reactor-239 to use as a fuel in the reactor Breeder reactors use have many safety Breeder reactors use have many safety

problems. Main one is use of liquid sodium as problems. Main one is use of liquid sodium as coolant (a highly reactive metal that explodes coolant (a highly reactive metal that explodes when in contact with water and burns when in contact with water and burns spontaneously in air at high temperature)spontaneously in air at high temperature)

Plutonium also used in nuclear weaponsPlutonium also used in nuclear weapons

What are the advantages and What are the advantages and disadvantages of Nuclear Power?disadvantages of Nuclear Power?

Advantage of nuclear- Advantage of nuclear-

Disadvantage-Disadvantage-

Nuclear Power in USNuclear Power in US

___ nuclear power plants in US (434 ___ nuclear power plants in US (434 world wide) supply ___% of nations world wide) supply ___% of nations electricityelectricity

Nuclear plants regulated by US Nuclear plants regulated by US Department of Energy, Nuclear Department of Energy, Nuclear Regulator Agency Regulator Agency

Internationally- Int’l Atomic Energy Agency Internationally- Int’l Atomic Energy Agency (IAEA)(IAEA)

Effects of ionizing radiation (contains Effects of ionizing radiation (contains enough energy to eject electrons from enough energy to eject electrons from atoms) damages DNA (mutations) atoms) damages DNA (mutations) resulting in birth defects, mental resulting in birth defects, mental retardation or genetic diseaseretardation or genetic disease

Mutations in genes controlling cellular Mutations in genes controlling cellular growth may convert them oncogenes growth may convert them oncogenes (genes that cause cancer)(genes that cause cancer)

What do we do with the waste?What do we do with the waste? #1 problem with plants = #1 problem with plants = 2 types of waste2 types of waste1.1. Low-level radioactive wastes- radioactive Low-level radioactive wastes- radioactive

solids, liquids and gases that give off solids, liquids and gases that give off small amounts of ionizing radiation and small amounts of ionizing radiation and include glassware, food, paper, clothing, include glassware, food, paper, clothing, etc.etc.

2.2. High-level radioactive wastes- High-level radioactive wastes- radioactive solids, liquids and gases that radioactive solids, liquids and gases that initially give off large amounts of ionizing initially give off large amounts of ionizing radiation and include reactive metals, radiation and include reactive metals, coolants fluids and reactor gasescoolants fluids and reactor gases

1980 Low-level Radioactive Policy Act1980 Low-level Radioactive Policy Act• Specified all states are responsible for the Specified all states are responsible for the

wastes they generate and encourage states to wastes they generate and encourage states to develop faculties to handle low-level wastesdevelop faculties to handle low-level wastes

No permanent facility for high-level wastes No permanent facility for high-level wastes (Yucca Mountain is proposed location)(Yucca Mountain is proposed location)

72 temporary sites in US72 temporary sites in US 1982 Nuclear Waste Policy Act- requires 1982 Nuclear Waste Policy Act- requires

federal government to find permanent federal government to find permanent disposal site and be operational by 1998 disposal site and be operational by 1998

Cons of Yucca MountainCons of Yucca Mountain

Near volcano and earthquake fault Near volcano and earthquake fault lineline

Transportation of high level wastes is Transportation of high level wastes is a problema problem

Pros of Yucca MountainPros of Yucca Mountain Dry area=>deep ground waterDry area=>deep ground water Only site currently under Only site currently under

consideration and it is safeconsideration and it is safe

Decommissioning (closing) Nuclear Decommissioning (closing) Nuclear Power PlantsPower Plants

Storage-Storage-

Entombment-Entombment-

Decommission-Decommission-

Radioactive Waste DisposalRadioactive Waste Disposal

1.1. Liquid wastes- highly unstable and Liquid wastes- highly unstable and difficult to monitor: must be difficult to monitor: must be converted to solid form via converted to solid form via “vitrification” (conversion to solid “vitrification” (conversion to solid glass or ceramic logs)glass or ceramic logs)

2.2. Solid Waste- Consolidation and Solid Waste- Consolidation and storage/monitoring underground storage/monitoring underground

FusionFusion

Combining 2 lighter atoms into one large Combining 2 lighter atoms into one large one producing very large amounts of one producing very large amounts of energyenergy

AnimationAnimation Isotopes of hydrogen (heavily hydrogen or Isotopes of hydrogen (heavily hydrogen or

deuterium) used for the processdeuterium) used for the process Radioactive Tritium is formed by fusion Radioactive Tritium is formed by fusion

(man-made; not found in nature)(man-made; not found in nature) Tritium and deuterium formed together to Tritium and deuterium formed together to

create energy and Helium-4create energy and Helium-4

FusionFusion

Advantage- no high-level radioactive Advantage- no high-level radioactive wastes (low-level wastes produced)wastes (low-level wastes produced)

#1 problem- requires very high #1 problem- requires very high temperaturetemperature

#2 problem- confining fuel#2 problem- confining fuel• Super heated ionizing gas (plasma) has Super heated ionizing gas (plasma) has

tendency to expand and nuclei aren’t tendency to expand and nuclei aren’t close together and will lose energy when close together and will lose energy when hit container wall (looking @ magnetic hit container wall (looking @ magnetic fields for containment)fields for containment)