Chapter 16/17 RAD Guide July 7, 2016

NUCLEAR ENERGY

Atomic Model

Atomic Model (cont)  Atomic consists of: Protons ( + charge) Nuetrons (neutral charge) Electrons (- charge)  Protons and neutrons makes the nucleus  Majority of atomic mass is in the nucleus  Electrons orbit the nucleus

Atomic Number & Mass Number  Atomic number: the number of protons in an atom. Example: if oxygen has 8 protons, what is oxygen’s atomic number?  Mass number: the number of protons plus the number of neutrons in an atom. We exclude electrons from mass number because mass of electrons is negligible.

Isotopes

Isotopes (cont)  Atoms of the same element that have different numbers of neutrons are called isotopes.  This means that isotopes of the same element will have different mass numbers.  Note: the number of protons in isotopes are always the same.

Radioactivity  Unstable atoms decay, emitting particles and energy from the nucleus.  After a series of decay changes, a radioactive element becomes stable.

Types of Particles Emitted from Unstable Nuclei (Radiation)  Alpha particles (α): decay that gives off 2 protons and 2 neutrons  Beta particles (β): decay that gives off an electron, converting a neutron into a proton  Gamma (γ) radiation: form of electromagnetic radiation. A large burst of energy.

Question  Which type of emissions alter an element’s … Atomic number? Mass number?

Half-Life  The amount of time it takes for half of the atoms in a sample of radioactive material to decay.

Parent Atoms Decaying to Daughter Atoms.

dd

Reactions and Reactors

Nuclear Fission  Energy holds the protons and neutrons in an atom’s nucleus together.  Question: what would happen if we were to split the nucleus of an atom apart?

 Nuclear Fission: Reaction in which the nucleus of a large atom is split into smaller nuclei.

Uranium -235 Chain Reaction  most commonly used in nuclear reactors.

Critical Mass

Structure & function of nuclear power plant.  Fission of U-235 in reactor vessel  heats H 2 O  steam  turns turbines  energy stored in generator  used as electricity  Water circulates between fuel rods, acting as a coolant and slowing neutrons.  control rods control how fast or slow reaction occurs

Nuclear Power Plant dd

Breeder Reactors

Nuclear Fusion Energy of the Future??

Nuclear Fusion-main rxn in STARS!! IS IT POSSIBLE TO CREATE A FUSION REACTOR ON EARTH?  Recall: Occurs when 2 atomic nuclei fuse to become one larger nucleus  The fuel for nuclear fusion reactions is deuterium (H-2 isotope of hydrogen).  Fuel is readily available in seawater  Fusion produces much less waste than fission, and produces enormous amounts of energy  However, scientists are still learning how to harness this energy source efficiently (needs extremely high temperatures; HARD TO CONTROL).

Nuclear Fusion using Deuterium

Nuclear Fusion with Deuterium and Tritium

Radioactive Waste  Harmful to living organisms Immediate effect: skin burns, anemia, death Long term effect: changes in DNA, leading to cancer & genetic mutations

Nuclear Waste Disposal  High level wastes Emit large amounts of radiation. Uranium fuel rods, control rods, coolant water. Stored in tanks outside power plants Tanks often leak, leading to contaminated site.  Low/medium level wastes Often buried Enclosed and dropped into oceans.

Nuclear Waste Disposal  Issues in finding permanent disposal method: Long half-lives hazardous/poisonous. Wastes must be sealed in containers that will never corrode Containers often leak into environment Waste sites must be geologically stable. Deep underground storage is highly expensive.

Nuclear Meltdown  If the cooling and control systems in a reactor core fail, the chain reaction becomes uncontrollable and melts reactor core.

Chernobyl Disaster-Russia April 1986 Chernobyl Disaster videoclip 13 min Chernobyl Disaster videoclip 13 min

Chp 17 Alternative Energy Sources- Solar energy, Hydroelectric Energy, Wind Energy, & Geothermal Enery

Solar Energy

The Sun  Source of almost all the energy on Earth Ecosystems Water Cycle Causes the winds to blow

Ecosystems-the sun is the major contributor of energy (which flows through the organisms)

Water Cycle

Wind dd

Thermonuclear Fusion: Production of Solar Energy

Solar Energy  Harnessing the sun’s energy to generate heat and electricity.  Advantages renewable, nonpolluting.  Disadvantages Energy source is not constant Equipment is not size and cost efficient.

Passive Solar Energy  Passive: sun’s energy is collected, stored, & distributed naturally in enclosed dwelling Not used to produce electricity, but reduces the need for it. Achieved through building design and positioning. Ex: Greenhouse

Passive Solar Energy (cont) dd

Passive Solar Energy (summary)  South facing windows  Building materials that absorb solar energy  Glass-enclosed areas  Dark colored walls and floors  Good insulation  Thick, heavy curtains or shutters.

Active Solar Energy  Active: devices are used to collect, store, and circulate heat produced from solar energy.  Types Flat-plate solar collectors Photovoltaic cells AC vs. DC power

Flat-Plate Solar collectors

Flat-Plate Solar Collectors

Solar One in Mojave Desert, CA.

Photovoltaic (PV) Cells  Only solar energy device that produces electricity directly.  Uses thin wafers of semiconductor material. Silicon or selenium  Structure: Two thin slices of semiconductor material joined. Sunlight striking the cell causes electrons to move from one slice to the other, resulting in an electric current.

PV Cells (cont)

PV Cell (cont)  Uses Solar powered Calculators Solar powered watch Electricity for homes, industry, automobiles  Advantages Light weight No wastes or pollutants No moving parts Do not consume any materials

Hydroelectric Energy

Dams  Flowing Water Water behind dam is directed at the turbine blades Water pushes against the turbine blades, causing them to turn. (kinetic energy to mechanical energy) Mechanical energy of the turbine is transferred to coils within a generator The coils spin through a magnetic field, producing sent electricity

Function of Dams dd

Advantages of Dams  Renewable  Controls flow of water Flood control Navigation of Boats  Reservoirs Recreation areas (fish, boat, swim) Store water (irrigation and home use)

Disadvantages of Dams  Changed water depth and flow alters natural plant & animal life  Shoreline can flood, leading to erosion & change ecosystems  Fish caught in turbine blades  Prevent salmon from completing reproductive cycle  Stored water released into downstream water causes changes a rapid change in temp

Oh that “Dam” humor!!

Tidal Energy (still hydroelectricity)  High and low tides cause turbines to turn in both directions generating electricity.

Tidal Energy Disadvantages  In most regions, the difference between high and low tide is insufficient to power a generator  Equipment damages surrounding wetlands  Affects local ecosystems.

Wind Energy Wind mills saving a town Wind mills saving a town

Aerogenerator Windmills that are used to generate electricity (wind turbine generators)

Aerogenerators  Winds causes blades to turn  energy is stored in generator  sent out as electricity  Types 1. Blades on horizontal (like airplane) 2. Blades on vertical (like eggbeater) Used for calmer conditions

Picture from my sister in California

Wind Farms dd

Advantages of Wind Power  Renewable  Free  Unlimited  nonpolluting

Disadvantages of Wind Power  DISADVANTAGES Not always windy enough Wind farms Require a lot of land Interferes with radio & TV signals Impact wildlife Ugly (?)

Geothermal Energy

Heat Source  Radioactive decay of elements deep beneath the ground.  This decay gives off heat

 lava, geysers steam vents, hot springs, & bubbling mud.

Hot Rock Zones  1.Hot water is pumped from deep underground through a well under high pressure.  2.When the water reaches the surface, the pressure is dropped, which causes the water to turn into steam.  3.The steam spins a turbine, which is connected to a generator that produces electricity.  4.The steam cools off in a cooling tower and condenses back to water.  5.The cooled water is pumped back into the Earth to begin the process again.

Hot Rock Zones

What are some advantages & disadvantages to using geothermal?  ADVANTAGES  DISADVANTAGES 1. Not easy to find 2. Most areas have very little geothermal heat at surface, and it’s not worth extracting. 3. Hydrogen Sulfide gas pollutes the air. 4. Minerals and salts corrode pipes. 5. Lack local H 2 O supply for steam production.