nuclear reactors. what is fission again? nuclear reactors take advantage of the process of nuclear...
Post on 19-Dec-2015
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What is fission again?• Nuclear reactors take advantage of the
process of nuclear fission which splits an atom and releases a great deal of energy
• FP = Fission Product
Quick Review of Nuclear Plants
Nuclear Fission
Generates Heat
Water intoSteam
Drives Turbine
Generates Electricity
Different Types of Power Plants
• In the US:– Pressurized Water Reactor– Boiling Water Reactor
• In general, most reactors are “Generation II,” such as the Fukushima Dai-ichi reactors
• Modern reactors are “Generation III” which are dramatically improved and more efficient– So-called “passive” safety measures which rely
solely on natural laws such as gravity
How is Radiation Contained?• The nuclear core is contained within a
“3.9 to 7.9 ft thick pre-stressed, steel-reinforced, air-tight concrete dome” to prevent escape
How is Waste Material Secured?
• Fuel can be replaced every 12-18 months• Two types of waste:– Low-Grade: Refers to materials in contact with the fuel
rods, directly or indirectly– High-Grade: Refers to the spent nuclear material and
byproduct• Secured in underground pools and depots for
several years in the plants or nearby• Geologists study naturally occurring fission
processes to better understand how to dispose of waste material
What could go wrong?
• Damage to the core due to loss of cooling– Due to loss of pressure– Due to loss of coolant– Due to uncontrolled power excursion
• Nuclear Meltdown– Not a technical term, but refers to the melting of
nuclear material and a breach in the containment vessel
Worst-case
• When:– “A limiting fault … that
leads to the failure of heat removal within the core ”
– The Emergency Core Cooling System (ECCS) fails
Then the core would heat beyond it’s melting point and turn into corium causing a containment breach
Radiation in the Environment
• Iodine 129 and 131 are radioactive and can be absorbed by the body causing thyroid cancer
• Acute radiation syndrome• Stunted growth and death in local wildlife• Increase in mutations in humans and other
animals• Groundwater absorbs radionuclides
Naturally Occurring Fission
• First found in Oklo in Gabon, Africa by physicist Francis Perrin
• These reactions occurred about 2 billion years ago, and were self-sustained for some hundred thousand years
• Scientists are studying this process to better learn how radioactive material travels through the Earth’s crust and how to contain radioactive inert gases release
1. Nuclear reactor zones2. Sandstone3. Uranium ore layer4. Granite
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