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50 Cards in this Set
- Front
- Back
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uranium fission
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tiny amounts of uranium release very large amounts of energy. Electromagnetic radiation.
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nuclear chain reaction controlled by?
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fission, (or split) into radioactive elements. Release 3 more nuetrons.
Each of those atoms will give up U235 neutrons and those will give up 3, and those 3.. |
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huge amount of energy given up as
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electromagnetic radiation
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uncontrolled atomic reaction =
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explosion
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controlling these reactions: control fission by
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by diluting 235U with 238U.
Uranium 238U will not support this fission reaction with neutron bombardment. Generate neutrons in lab reactor |
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U238 reaction?
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non reactive, but adding U235 mix can cause fissure.
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liming neutron flux (flux = elements moving around in this process neutrons)
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1. moderators = slow down neutrons. steady neutron flux created.
2. control rods = absorb neutrons, slow fission. pull some neutrons out of the reaction like a sponge so it slows the reaction. |
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moderators use what minerals to slow down neutrons?
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graphite or water to slow down neutrons
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what's used in control rods to slow neutron reaction?
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boron or cadmium
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1kg of uranium fuel =
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enough energy for 176 US citizen for 1 year.
(a lot of energy from a little bit of uranium) |
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uranium ore must be enriched in U235 to become reactor or weapons fuel. What are the 3 steps?
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step 1. concentration to yellowcake.
step 2. conversion to UF6 gas Step 3: Separate 235UF6 from 238UF6 |
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raw uranium ore
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1% U30 Uranium Oxide
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mining Uranium
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leaching to yellow. dissolve away impurities and concentrate: what's left is yellowcake. 70-90% U209
convert to UFC uranium Hexaflouride gas. |
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mass of UFC Uranium Hexaflouride is small, but when you have enough what happens?
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it's converted to Uranium Dioxide.
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separating 235 UF6 from 238 UF6:
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two gasses different concentration. blend those two gasses together.
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U02 uranium dioxide is then?
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pressed into pellets and filled into fuel rods.
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reactor fuel vs weapon fuel
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reactor <20% 235U2
weapon >85% 235U2 |
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where was first nuclear research
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tennessee washington
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nuclear reactor inside--?
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fuel goes into swimming pool for 5-7 years and going to degrade into other radioactive elements.
-cool fuel off heat generated can acutally melt uranium dioxide into a liquid and steel tubes that hold it together. |
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even after we've consumed a reactor, how much of original 235U remains?
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25% remains. even though there's still fissure material and radioactive there's not enough 235U to sustain any reaction anymore.
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all nuclear reactors produce huge amounts of
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heat
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gas cooled reactors use what?
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carbon dioxide or helium gas
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oldest reactors are of what type?
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gas cooled reactors, least safe reactor design.
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focus of new renewed interest because of high potential from?
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small fuel volumes
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energy goes to heating up?
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the cooling. high pressure gas, usually C02 or helium pumped through fissing.
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fast breeder reactor
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jacket of 238U,
surrounds the 235U fuel rods reactors "bread" 239 pu fuel popular in france and japan makes new, fissible material: plutonium |
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239Plutonium is rapidly made into
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atomic weapons-- very toxic highly radioactive the size of a pin is the amoutn of plutonium it would take to kill you. fleck of ust.
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Liquid metal cooling the reactor; problem?
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lquid sodium, much higher temp to make much hotter steam, but the technical problem of keeping the metal liquid.
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water cooler reactors: pressurized water
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pressurized water -- transfers heat to steam generators that make steam into turn turbine.
water is the moderator (controls reaction by slowing down) -coolant -transfer heat to make energy |
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water cooler reactors: Boiling Water
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makes steam to turn turbine
directly Steam drives a turbine to produce electricity Steam is condensed back to liquid water |
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Three Mile Island Nuclear Generating Station
Harrisburg Pennsylvania |
most famous nuclear accident in US penn
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Criticality:
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Nuclear reactors can have uncontrolled fission
Loss of coolant accidents are most severe risk Nuclear reactors cannot yield an atomic explosion -maximum stable power output of a nuclear reactor "ideal conditions" |
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Bioaccumulating
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animals who ingest radioactive materials will generate contaminated
milk and meat |
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loss of cooling accidents
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maintaining the coolness. cooling problems: Leaks, Pump Fails, valves.
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insert control rods
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stop neutron flux
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residual heat boils coolant
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increases neutron flux
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high temp melt fuel
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bundles: meltdown
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steam and gas explosions destroy reactor
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release radiation
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what was the problems with 3 mile island reactor?
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Pressurized water-cooled reactor
Pump for water cooling system failed Incorrectly set valves caused a coolant leak but operators thought there was excess water Coolant flow was reduced - led to overheating Reactor core was uncovered for several hours Operators vented slightly radioactive steam to reduce pressure 133Xe (xenon) gas Partially melted and vaporized the core |
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131 Iodine gas
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very radioactive
decay quickly emitted a lot of radiation absorbed by the humans thyroid |
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Chernobyl Power Station USSR
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1 death by explosion
31 died weeks later from radiation exposure Reactor went from 7% power to several 100x full power in ~ 1 second Vaporized the cooling water to steam - blew the reactor open, caught fire Ejected molten graphite and fuel rods to an altitude of 7 km |
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1999 - workers at a Tokyo uranium processing facility
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added too much 235U
during fuel fabrication - caused a brief chain reaction; released radiation 300,000 residents ordered to remain indoors for a few days Two workers died and 439 people were exposed to significant radiation The facility's license was revoked by the Japanese government carelessness |
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Davis-Besse Nuclear Power Station - Oak Harbor, Ohio
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Cracks and severe corrosion found on pressurized water reactor
Nuclear Regulatory Commission is conducting safety studies of ~70 similar reactors in the U.S. 2005 - NRC levied $5,450,000 in fines against FirstEnergy Nuclear Operating Co. |
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what part of US has more nuclear power?
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eastern.
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Hanford Reserve
Washington |
Defense waste at government facilities
military bases weapons and research facilities |
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Weapons grade material and
spent fuel rods will take at least ___________ yrs to decay to safe levels |
10,000 years.
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U.S. Disposal Policies for High Level Waste specify that?
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High Level Waste will be disposed of underground, in a deep geologic repository
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Congress specified ________ site best fit criteria
and had minimal political influence |
Nevada, Yucca Mountain
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Problems Problems with Yucca Mountain
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Tectonically unstable
Volcanism in the last 10,000’s years High groundwater flow Yucca Mtn is not large enough to hold all of the waste already generated |
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Nuclear fuel and waste transport
in the U.S. and Europe have a _____ safety record |
perfect
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