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Nuclear Reactors. 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. Different T ypes of Power Plants. In the US: Pressurized Water Reactor
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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
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