Transcript nuclear power - Fort Thomas Independent Schools

Reading Qs
1. List the different reasons why
these nuclear accidents occurred.
2. Select the one that interests you
the most and explain why.
Starter Q (1/13)
1. What is the difference between
an atom, element, molecule,
atomic number, isotope and ion?
Nuclear Weapons
Atom Bomb (fission)
Hydrogen Bomb (fission-fusion)
Which releases more energy?
• Nuclear fission of U 235 molecule
or the explosion of one molecule
of dynamite?
Release of nuclear
potential energy vs.
chemical potential energy
• “The energy released by the fission of one
uranium-235 nucleus is enormous—about
seven million times the energy released by
the explosion of one TNT molecule.”
Paul Hewitt—from Conceptual
Physical Science Explorations (2003)
• Nuclear energy provides more energy per
unit time than does burning an equivalent
amount of a source of chemical PE.
Which is more powerful?
Chemical Reactions vs. Nuclear
Reactions
• Chemical reactions do not change the nucleus,
they just release the chemical PE stored in the molecular
bonds. There is no conversion of mass into energy, just
energy to energy transformations.
– In chemical reactions, mass is conserved and
the elements do not change.
• Nuclear reactions change the nucleus, releasing the
nuclear PE stored in the nucleus and changing the
element (transmutation).
– A small amount of mass is converted into
energy during this process (mass loss = energy
gain)
– The sun loses 2 to 3 x 10-14 solar masses per year due to fusion.
Two types of nuclear reactions
• Releasing the energy stored in the nucleus
causes a small amount of matter to be
converted into energy.
– Fission (splitting of a heavy nucleus)
• U235 and Pu239 absorbs 1 neutron and splits!
– Fusion (fusing together of light nuclei)
• Hydrogen nuclei fuse to form Helium
http://www.ida.liu.se/~her/npp/dem
o.html
Fission vs. Fusion
• Prime examples of fission reactions
– Nuclear power plants
– Atomic bombs
• Prime example of fusion reaction
– Fusing hydrogen nuclei into helium nuclear at
the core of every star (including the Sun)
http://www.visionlearning.com/libr
ary/flash_viewer.php?oid=2747http://www.visionlearning.com/libr
ary/flash_viewer.php?oid=3602
What is radioactive decay?
• Process by which an unstable nucleus emits one
or more particles or energy in the form of
electromagnetic radiation.
Radioactive Decay
• Loss of Mass
– Alpha decay (emits a helium nucleus)
– Beta decay (emits an electron)
• Loss of Energy
– Gamma decay (emits a gamma ray)
Common Radioactive Elements
and Half-Lives
•
Beryllium...................2,700,000 years
Calcium.....................100,000 years
Cesium-137................half life - 30 years
Cesium-135................2,000,000 years
Rubidium...................47,000,000,000 years
Palladium...................7,000,000 years
iodine-129..................17,200,000 years
plutonium-239............half life - 24,390 years
strontium-89...............53 days
strontium-90...............28 years
tin-126.......................100,000 years
uranium-235........................713,000,000 years
uranium-238...............4,510,000,000 years
Nuclear power plant
To Power lines
_________ potential energy is released by ________ of the isotope _____ ,
producing __________ energy. This energy causes the water in the steam
generator to change state and __________, increasing the pressure in the steam
generator. The steam then applies a __________ to the turbine causing it to turn
a certain distance. This represents ______ done by the steam, which represents
a transfer of ___ - ________ energy to ____________ energy. The movement
of the turbine represents __________ energy. As the turbine turns, a coil of
copper wire turns inside a magnetic field, generating _____________. So the
___________ of the turbine is transferred to ____________, which is
conducted to homes and businesses via high voltage power lines.
What is the basic fuel for nuclear
power?
• Uranium 235 (a heavy radioactive metal) or
Plutonium 239
• The earth contains U238 (99%) and U235 (0.7%).
• U-235 is one of the few materials that can
undergo induced fission.
• U 235 must be enriched to 3-5 % to be used in
nuclear reactors.
• Weapons-grade U235 needs to be 95%.
What happens during fission of
Uranium 235?
1. The nucleus will split into two lighter
nuclei (Krypton and Xenon or Strontium
and Barium, for example)
2. A large amount of thermal energy is
released.
3. Gamma rays are released.
4. Two additional neutrons are released.
Uranium Fuel
Nuclear Fuel Rods
Nuclear Reactor Core and
Control Rods
Radioactive Wastes
• The fission process produces highly-radioactive
products, including plutonium.
• Generation (new fuel needed every 16-18
months)
• Holding (at the power plant)
• Transportation (DOE approved routes)
• Disposal/Burial Vault (in theory)
• http://www.nrc.gov/waste/hlwdisposal/design.html
How do we get electricity from
nuclear energy?
• Nuclear fission releases thermal energy,
which heats a fluid (water), which boils
producing high pressure steam. Work can
be done by the steam, which turns a turbine
connected to a generator, which transfers
mechanical energy to electrical energy.
• http://www.nei.org/scienceclub/nuclearwor
ld.html
Nuclear Power Plants in the
United States
There are over 100 nuclear power plants in the USA.
Can a nuclear power plant
explode like a nuclear bomb?
• No.
• Nuclear fuel contains a small percentage of
uranium 235 (3-5%). Weapons grade is
over 90% uranium 235.
• A meltdown of the core can occur, which
can lead to a steam explosion, not a nuclear
blast. Like Chernobyl.
Question
1. What is the difference between
an atom bomb and an nuclear
bomb?
2. Atom bombs use U235 or Pu239, which
release stored nuclear energy by fission
3. Nuclear bombs require an initial atomic
bomb explosion to initiate hydrogen
fusion.
The sun gets its
energy from nuclear
fusion reactions at its
core.
Sunlight is mostly yellow-green
visible light
Blue star
Sun
Red star