CURRENT USE STATISTICS
HISTORY OF NUCLEAR ENERGY
NUCLEAR POWER CYCLE
Basics of Nuclear Power
History
Ernest Rutherford – split the atom in 1917Enrico Fermi – nuclear fission in 1934Scientists realized fission reactions could be
self-sustainingFirst man-made reactor – Chicago Pile-1 in
1943 (later part of the Manhattan Project)Stricter government regulation after WWIIMovement against nuclear power driven by
fear and history of nuclear accidents
Current use statistics
Worldwide - 2.1% of the energy and 15% of electricity United States, France, and Japan 56.5% of nuclear-
generated electricity Economics – large initial investment ($6-10 billion),
most economical to run plants for as long as possible or add reactors to existing plants
From the 2003 MIT study, “The Future of Nuclear Power”: “In deregulated markets, nuclear power is not now cost
competitive with coal and natural gas. However, plausible reductions by industry in capital cost, operation and maintenance costs, and construction time could reduce the gap. Carbon emission credits, if enacted by government, can give nuclear power a cost advantage.”
Nuclear fuel cycle
Exploration
Two uranium isotopes U-235 (0.71%) and U-238 (99.29%)
U-235 is a fissile isotope – fissions when hit by a free neutron
U-238 absorbs the free neutron to become U-239
U-238 become Pu-239, a fissile isotope, though natural radioactive decay
Uranium mining and processing
Open-pit (surface), underground, and in situ leaching mining techniques
Uranium ore in the United States ranges from 0.05% to 0.3% uranium oxide (U3O8)
Trace quantities of uranium in domestic phosphate-bearing deposits of marine origin
Uranium ore is ground and the uranium is extracted though chemical leaching
The resulting product, yellowcake, is sold as uranium oxide
Uranium ore Yellowcake
Uranium mining and processing
Uranium conversion
Uranium oxide converted to uranium hexaflouride, form required by most commercial uranium enrichment plants Solid at room temperature, gas at 57°C Conversion of only natural uranium (not enriched) Most uranium converted to UF6
Also convert to uranium dioxide (UO2) for reactors that do not require enriched uranium
Enrichment
Natural UF6 enriched to fissionable isotope Light-water reactor fuel enriched to 3.5% U-
235Various methods of isotope separation –
gaseous diffusion, gas centrifuge96% of byproduct is depleted uranium95% of DU is stored as uranium hexaflouride
Fabrication
Enriched UF6 converted into UO2 powder, which is processed into pellets
Pellets fired in sintering furnace, processed to be uniformly shaped
Pellets stacked into tubes of metal alloy and sealed, creating fuel rods (specific to reactor core)
For BWR and PWR, fuel rods bundled, given unique identification numbers (trace from manufacture to disposal)
Transportation
Most transports of nuclear fuel material occur between different stages of the cycle
Minimize radiation exposureSpecial handling for spent fuel and high-level
wasteSpent nuclear fuel shipping casks, shielding
techniques
In-core fuel management and interim storage
Array of cells, each cell is fuel rod surrounded by coolant (water)
Water or boric acid provide cooling (decay heat from residual radioactive decay) and shielding
After operating cycle, spent fuel discharged and usually stored in spent fuel pool
When spent fuel pool is filled, store cool aged fuel in dry storage facility (ISFSI)
Reprocessing
Fissile and fertile materials, such as U-235, Pu-239, and U-238, can be chemically separated and recovered from the spent fuel to be recycled for use as nuclear fuel
Mixed oxide fuel (MOX) – blend of reprocessed uranium, plutonium, and depleted uranium; behaves similarly to the enriched uranium Alternative to low-grade uranium used by light-water
reactors
Waste disposal “the Achilles heel of the nuclear industry”
Disposal of spent fuel and disposal of wastes from processing plants
Nuclear Waste Policy Act (1982) – Department of Energy responsible for waste disposal system for spent nuclear fuel and high-level radioactive waste
Deep geological repository for solid wastes, burningHigh-level radioactive waste – spent fuel (spent fuel
pools casks) Proposed storage at Yucca Mountain, no longer harmful after
10,000 years (EPA)Low-level radioactive waste – contaminated items,
hand tools, water purifier resins, and the reactor materials
Three Mile Island Accident
March 28, 1979 Combination of equipment
failure and confused plant operators.
Partial melting of fuel rod cladding.
Release of 43,000 curies of radiation released
Very strong containment shell built over reactor thanks to activists
No deaths or injuries-exposure to people in a 10 mile radius was about the same as receiving a chest x-ray
Lots of unknowns and fear at the time of the accident
Chernobyl
April 26, 1986 Ukranian republic of the USSR Monitoring turbine generators during at low power Reactor design made it unstable at low power and operators didn’t
take proper safety precautions A power surge caused two explosions which destroyed the reactor
core and blasted a hole in the roof of the reactor building 100-150 million curies released into atmosphere radioactivity estimated to be about two hundred times that of the
combined releases in the bombing of Hiroshima and Nagasaki Evacuation zone of ~1,100 square miles Over 75,000 people relocated Fallout devastated farmland, increased rates of thyroid cancer in
children Possibility of birth defects in future generations Plant completely shut down in 2000
Nuclear Proliferation
Plutonium is a waste product of nuclear fission- this can be used as further fuel or to make nuclear bombs
International Atomic Energy Agency (IAEA)- responsible for monitoring the world’s nuclear facilities and
preventing nuclear proliferation. The agency has acknowledges that there is a large amount of uncertainties and its impossible to detect all diversions of nuclear material.
Hanford
Nuclear weapons production beginning in 1943
Built along the Columbia river
Released large amount of waste into river/air
Affected 75,000 square miles
Hanford continued
Secrecy surrounded the operationIncreased citizen pressure finally allowed for release of
19,000 page document regarding Hanford’s historyBetween 1944-1972 approximately 2 million people
exposedDoses of I-131 increases risk of thyroid cancer, children
most susceptibleCurrently Hanford is the most contaminated nuclear
waste site in the U.S. and focus of largest environmental cleanup
53 million gallons of high level radioactive waste = 2/3 of nations high-level radioactive waste by volume
Hard to find data correlating cancer and exposure
High Level Radioactive Waste
Shearon Harris
New Hill, NC in Wake County
Single ReactorUntil 2003 nuclear waste
from two other plants were being shipped in for temporary storage on trains
Currently houses nation’s largest spent fuel pools.
These rods are packed in high density-run the risk of going critical
Long Term Storage at Yucca Mountain
90 Miles northwest of Las Vegas33 known geological faults in the vicinity 1992-5.6 earthquake 8 mile from site center which
damaged DOE project officeStorage to be well above water table but DOE
underestimated the time for water to seep from the surface
The earliest Yucca Mountain could open would be 2017 and by this point the amount of commercial waste produced will have surpassed the legal limit allowed in Yucca Mountain…a second repository would be needed
Yucca Mountain
“Low-level” Radioactive Waste
Very poor classificationExample: Includes medical waste as well leakages
from the reactor coreMost medical waste is hazardous for less than 8
months but reactor waste in the same category could be hazardous for hundreds of thousands of years
Trend has been to downgrade high grade waste. Saves money as regulations only require 100 years of passive institutional control.
NRC has planned for allowed/acceptable leakages (life on container does not last radioactivity lifespan) which are deemed as acceptable risks
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