The Nuclear Fuel Cycle:Waste, Risk, and Economics
Lecture #17
ER 100/200
Pub Pol 184/284
Oct. 29, 2015
The Nuclear Fuel Cycle
Economics
Radioactive Waste Disposal
Safety
Security
The first nuclear reactors: submarines (constrained engineering)
“Good ideas are not adopted automatically. They must be driven into practice with courageous patience.”
-Admiral Hyman G. Rickover, father of the U.S. Nuclear Navy
The first commercial nuclear power plant
Shippingport, PA
achieved criticality in 1957
decommissioned in 1982
California’s electricity mix (2012)
Source: California Energy Commission’s Energy Almanac, http://energyalmanac.ca.gov/electricity/total_system_power.html
Nuclear power plants in CA:
Diablo Canyon Power Plant (DCPP)
San Onofre Nuclear Generating Station (SONGS)
California’s electricity mix (2012)
Units 2 and 3
Combustion Engineering two-loop
pressurized water reactors, generated
1,127 MWe gross, and
1,070 MWe net respectively, when
operating at 100% capacity.
“Bechtel was ... embarrassed in
1977, when it installed a 420-ton
nuclear-reactor vessel backwards"
at San Onofre.
California’s electricity mix (2015)
Source: California Energy Commission’s Energy Almanac, http://energyalmanac.ca.gov/electricity/total_system_power.html
Nuclear power plants in CA:
Diablo Canyon Power Plant (DCPP)
[San Onofre Nuclear Generating Station (SONGS), closed; nuclear production now ~5% in CA]
Some nuclear physics
Periodic Table of the Elements
Chart of the Nuclides
Fission: the splitting of an atom into two or more nucleiFission is the splitting of a nucleus
into two or more nuclei
Reaction Energy (MeV)
Fission 200
Fusion (D,T) 17.6
Chemical ~10-6
Comparison with Fossil Fuels
C12 + O2 C12 O2 + 4 eV
per atom [eV] per gram [W•hr]
Carbon ~ 4 ~ 10
Uranium ~ 2E8 ~ 2E7
0n1
0n1
92U235
92U235
92U238
94Pu239
x
y 200MeV
Nuclear Fission
Chemical reaction
Comparison to Fossil Fuels
120 gallons of oil
1 ton of coal
0.5 cubic meter
of natural gas
200 MeV per reaction ~100 eV per reaction
Why it works: Binding Energy
The mass of an atom is smaller than the sum of its parts.
The difference is called the “binding energy”—the energy required to hold the atom together.
DE = Dmc2
“The discovery of nuclear reactions need not bring about the destruction of mankind any more than the discovery of matches.”
Albert Einstein
The front end of the fuel cycle
17
Uranium Global Resources
Uranium Resources
18
LWR Fuel Cycle
Uranium
U mined as U3O8
Natural abundance:
99.3% of 92U238
0.07% of 92U235
92U235 is fissionable by “slow” neutrons
92U238 is fissionable only by “fast” neutrons (but is a “fertile” isotope)
Our fuel cycle uses fission of U-235 to produce electricity
Source: World Nuclear Association
Mining
extraction of natural ore from the ground
Ranger open pit uranium mine, Australia. Image credit: http://www.abc.net.au/news/2008-09-17/a-haul-truck-carries-uranium-ore/405464
Mining (cont.)
In-situ leaching of U, a.k.a.
in-situ recovery (ISR)
Little surface disturbance, no tailings
Milling
Extraction of uranium from ore by crushing, grinding, solvent-extraction separation
Creation of mill tailings
Uranium Reduction Company Mill, Moab, UT. Image credit: http://www.moabhappenings.com/Archives/historic0909ProgressingFromRadioactivePast.htm
Conversion
From U3O8 yellowcake (~80% U) to UF6 gas
Fluorine is used because:
-only one isotope of F
-commercially viable
-UF6 the only uranium compound that is a gas at room temperature
Enrichment
0.7 % 235U → 3.3 - 5 % 235U for PWR
Two main enrichment technologies:
Gas centrifuge
Gaseous diffusion
Graham’s Law:
Depleted Uranium
Parking lot full of 750,000 MT of DU cylinders in Paducah, KY
Fuel Fabrication
UF6 converted into UO2 powder, then sintered and pressed into pellets at >1700°C
MOX fuel: a combination of UO2
and PuO2
Pellets tapered slightly on each end, which allows pellets to expand and contract through drastic temperature changes inside reactor without damaging fuel or cladding materials
They are "dished" slightly on each end. End taper allows pellets to
expand and contract through drastic temperature changes inside
reactor without damaging fuel or cladding materials
Reactor Fuel (Pellet) Fabrication
Final machined pellets are typically about 0.5 inch
in length & about 0.33 inch in diameter.
Image Source: See note 9
Image Source: See note 6
Uranium dioxide pellets form
fuel rods that are grouped
in square assemblies
Fuel Fabrication (cont.)
Fuel pellets assembled into fuel rods with Zircaloy cladding and bundled into a (square) fuel assembly
Shipping of Fuel to Reactor
Assembly is shock-mounted
so that damage does not occur
during transport to customer
which is usually performed by
truck
New Fuel Shipping Container
Images Source: See Note 6 Images Source: See Note 6
Images Source: See Note 6
Assembly is shock-mounted
so that damage does not occur
during transport to customer
which is usually performed by
truck
New Fuel Shipping Container
Images Source: See Note 6 Images Source: See Note 6
Images Source: See Note 6
The Reactor
Nuclear energy systems require three basic componentsNuclear energy systems require
three basic components
! Fuel
! Fissile material necessary to maintain the chain reaction
! Moderator
! Reduces neutron energy to enhance fission probability
! Light material, non-absorbing
! Water, graphite
! Coolant
! Removes the heat generated in the fuel
! Carries the heat for conversion
Light Water Reactors: the majority of all nuclear power plantsLight Water Reactors are the
majority of all nuclear power plants
Type No. of Units Total MWe
BWR 92 83,656
FBR 2 690
GCR 18 8,909
LWGR 16 11,404
PHWR 44 22,441
PWR 264 243,121
Total 436 370,221
Type No. of Units Total MWe
BWR 3 3,925
FBR 2 1,220
LWGR 1 925
PHWR 4 1,298
PWR 40 35,515
Total 50 42,883
Reactors in operation worldwide
Reactors under construction worldwide
BWR Boiling Water ReactorGCR Gas Cooled ReactorFBR Past Breeder ReactorLWGR Light Water Graphite Reactor
PWR Pressurize Water ReactorPWHR Pressurized Heavy Water Reactor
Life Cycle GHG Emissions
~100 nuclear power by 2020,
Tripling 2014 to reach 58 million
kilowatts,
~ 2 billion per reactor, 5 year
construction time
Pressurized Water Reactors: two-loop heat conversion systemPressurized Water Reactors use a
two-loop heat conversion system
Boiling Water Reactors: single-loop heat conversion system
Boiling Water Reactors use a
single-loop heat conversion system
GenIV systems to improve economics, safety, sustainabilityGeneration IV systems are will improve economics, safety, and sustainability
LWR fuel releases hydrogen and fission products when overheated
Zirconium cladding reaction with steam to
produce hydrogen becomes substantial at
temperatures above 1000°C
Volatile fission products released as noble gases
(e.g. Kr) or aerosols (e.g. I, Cs)
Fuel pellets melt at 2600°C
TMI Events: March 28, 19794 a.m.Unit 2 has been in service for about three months. Unit 1 is shut down for refueling. A minor malfunction in the non-nuclear part of Unit 2 occurs, triggering a series of automated responses in the reactor's coolant system, including the opening of a reliefvalve on top of the pressurizer to relieve pressure. The relief valve fails to close automatically when the pressure drops. Control roomoperators misread the situation and mistakenly believe coolant is being pumped into thesystem. Meanwhile, the valve remains open for 2 1/4 hours as precious reactor coolantspews out.
An automated emergency cooling system also is turned off.
6:48 a.m.By now, high radiation levels exist in several areas of the plant, and evidence indicates as much as two-thirds of the 12-foot-high core has stood uncovered. A partial meltdown of the fuel bundles occurs.
Chernobyl: Immediately after the Accident
At 1:30 A.M. on April 26, 1986reactor #4 exploded due tobuilt up steam in the reactorcore itself. Twenty percent ofthe radioactive contents ofthe core were blown 2/3 of amile in the air.
RBMK-1000 Reactor
The Sarcophagus
A twenty-eight story building,called the sarcophagus,constructed of lead, steel, andconcrete was built over thecrumbled remains of the powerplant
Chernobyl pictured in 1995
(Notice there are NO containment domes.)
Hultman, Koomey & Kammen (2007) ES&T
The Cost of Nuclear Power from the U. S. Civilian Reactor Fleet
Can nuclear compete? (depends who you ask)
The back end of the nuclear fuel cycle
An Example of Nuclear Fuel Cycle
49
Nuclear Fuel Cycle and Waste Generation
LLW 1,000 200-liter drums26 ton U
0.95 ton FP
0.27 ton Ac
0.24 ton Pu
TRU/LLW
< 0.26 ton U
0.95 ton FP
0.27 ton Ac
~ 1 ton U
Ra, ThMill tailings U7%
Th-230 100%, Ra 98%Airborne Rn
0.2% U3O8
= 181 ton U
167 ton
26 ton
100,000
Ton ore
165 ton
(0.3%U-235)
~ 0.5 ton U
27.5 ton
27.3 ton
~0.2 ton U
1 GWe, LWR, 1 year
Reprocessing scheme
Thermal efficiency 0.325
Capacity factor 0.8
50
Half-life: basics
The rate of radioactive decay is expressed in terms of half-life:
dQ/dt = -kQ, so Q(t) = Q0e-kt
The half-life of an element is the time required from one-half of its unstable nuclei to decay
The half-life of an element, or the 1/e time is
thalf = 0.693/k
The decay constant for U238 is 4.87 X 10-18/s
The half life is therefore
thalf = 0.693/4.87 X 10-18/s = 1.42 X 1017s = 4.5 X 109 years
The half-life of U238 is 4.5 billion years.
U238 decay pathway
52
A Variety of radiation units
25-July-09
55
Many of the weapons were tested in Nevada.
Easily viewed on
Google Map, about
~ 60 miles NW of
Las Vegas
Radioactive Waste
LWR Spent Fuel
Stored in pools upon discharge
Transportation of Radioactive Waste
http://archive.org/details/nuccasktest1
Storage of Radioactive Waste
Provide:
isolation, environmental protection, and monitoring
To facilitate:
treatment, conditioning, and disposal
Storage may be necessary for decay and/or thermal management prior to geologic disposal. Sometimes, storage of radioactive waste is practiced for economic or political reasons.
Interim Storage
Dry cask storage Decay storage of solidified HLW
Composition of Used Nuclear FuelPlutonium does not occur in nature, but is instead produced
from irradiation of 238U in a reactor.
Reprocessing of Used Nuclear Fuel: PUREX
Reprocessing facility in La Hague, France: Spent Fuel Reprocessing
Reprocessing Complex
LaHague, France
Image Source: See Note 4
Image Source:
See Note 2
Image Source: See Note 4
Reprocessing Facilities Around the World
COMMERCIAL SPENT URANIUM OXIDE FUEL REPROCESSING PLANTS
IN OPERATION AND UNDER CONSTRUCTION IN THE WORLD IN OPERATION AND UNDER CONSTRUCTION IN THE WORLD
Country / Company Facility / Location Fuel Type
Capacity
(tHM/year)
France, COGEMA UP2 and UP3, La Hague LWR 1700
UK, BNFL Thorp, Sellafield LWR, AGR 1200
1500UK, BNFL B205 Magnox Magnox GCR
1500
Russian Federation, Minatom
RT-1 / Tcheliabinsk-65
Mayak 400 VVER 400
Japan, JNC Tokai-Mura LWR, ATR 90
Japan, JNFL
Rokkasho-Mura
(under construction) LWR 800
India, BARC
PREFRE-1, Tarapur
PREFRE-2, Kalpakkam
PHWR
PHWR
100
100
China, CNNC Diowopu (Ganzu) LWR 25-50, p ( )
MOX Fuel Fabrication Facilities
MIXED URANIUM PLUTONIUM OXIDE (MOX) FUEL FABRICATION FACILITIES
Country / Company Facility / Location Fuel Type
Capacity
(tHM/year)
France, COGEMA CadaracheLWR, FBR 40
France, COGEMA Marcoule-Melox LWR 100
Belgium, Belgonucleaire DesselLWR 40
UK, BNFL Sellafield SMP LWR 120
UK Sellafied MDFLWR 8
Russian Federation,
Minatom Chelyabinsk
FBR 60
Japan, JNC Tokai-Mura ATR 10
Japan, JNFL Rokkasho LWR 130LWR 130
India, AFFF, BARC Tarapur LWR, PHWR &
FBR
Vitrification of HLW
Calcination followed by induction melting
History of U.S. Radioactive Waste Management
Nuclear Waste Policy Act (NWPA): 1982
Amended: 1987
Mandated Yucca Mountain to be the nation’s geologic radioactive waste repository
With plans to build a second repository in the East in the future
Radioactive Waste Classification in the U.S.
Adapted from Croff et al.
Waste Isolation Pilot Plant
Permian rock salt formation near Carlsbad, NM
World’s only operating radioactive waste geologic disposal facility
Has been accepting U.S. TRU waste since 1999 … Accident in 2013
Yucca Mountain
Volcanic tuff:
Porous, but low precipitation and percolation flux
Strong radionuclide immobilization in rock layers
Two major issues with permanent geologic disposal
Repository capacity limits for future nuclear power utilization
Uncertainty in long-term performance of the repository