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