MA9001 – Introduction to Energy

Topic 4 – Nuclear Energy

Weeks 5 & 6 (6 hours)

presented bypresented by

A/P Stuart Victor Springham

N l S i d S i Ed i (NSSE) NIENatural Sciences and Science Education (NSSE), NIE

Email: stuart.springham@nie.edu.sgPhone: 6790 3838o e: 6 90 3838

1

Nuclear Energy WorldwideNuclear Energy Worldwidegygy440 operating commercial power reactors

31 countries

376,500 MWe

62 new reactors under construction

154  new reactors planned

Primarily used for Electricity Generation

Produces 16% of the World’s Electricity

Other applications beyond electricity generation

Water desalination Hydrogen Production – for a 

Chemical Process Heat future Hydrogen Economy !

Source: World Nuclear Association: www.world‐nuclear.org/info/reactors.html

2

Attitudes to Nuclear EnergyAttitudes to Nuclear EnergyIn the West, Nuclear Energy was at a low ebb for about 20 years following the 

Chernobyl Accident (1986). However it has continued to grow in Asia; especially in Japan, h d b l h d d b

gygy

South Korea and Taiwan, but now also in China, India, Vietnam, United Arab Emirates, Indonesia, …

In recent years there has also been a resurgence of interest in Nuclear Energy in the

“We can agree renewable energies, such as wind, geothermal and hydro are part of the 

In recent years there has also been a resurgence of interest in Nuclear Energy in the West, due largely to concerns about Global Climate Change and Energy Security.

solution. But nuclear energy is the only non‐greenhouse gas‐emitting power source that can effectively replace fossil fuels and satisfy global demand.”

Patrick Moore, Founder Of Greenpeace,                 

Chair and Chief Scientist of Greenspirit

“I believe that the world nuclear industry will continue to supply electricity in a safe and reliable manner and that this supply will give civilization the chance to survive throughreliable manner and that this supply will give civilization the chance to survive through the difficult times soon to come.”

“Nuclear energy is the only green solution.”Nuclear energy is the only green solution.James Lovelock, Geophysicist who developed

the Gaia Theory of Earth Ecology3

But… Fukushima But… Fukushima Disaster 2011Disaster 2011Nuclear reactor core meltdowns, and releases of radioactive materials at the Fukushima Nuclear Power Plant in Japan, following the earthquake and t i 11 M h 2011tsunami on 11 March 2011.

4

Economical Simplified Boiling Water Reactor (ESBWR)

E P i d W t

However many new 

European Pressurized Water Reactor (EPR)

Generation III+ Reactor Designs that offer i ifi tl i d

Advanced Passive 

Pebble Bed Modular Reactor (PBMR)significantly improved 

Safety and Economicsrelative to the (mainly)

Reactor (AP1000)(PBMR)

relative to the (mainly) Generation II Reactors which are in operation today.

5

Sources of EnergySources of EnergySources of EnergySources of EnergyRenewableNon‐Renewable

Sources of EnergySources of EnergySources of EnergySources of Energy

• Biomass

• Geothermal

• Coal

• Oil Geothermal

• Hydro

S l

Oil

• Natural Gas

P • Solar

• Wind

• Propane

• Uranium

All sources have positive and negative attributes related to environmental impacts, abundance, cost, reliability, etc.environmental impacts, abundance, cost, reliability, etc.

Many governments now take the view that the best way to meet Economic, Environmental and Energy Security concernsmeet Economic, Environmental and Energy Security concerns is to have a Mix of Energy Sources.

6

Electricity Electricity –– Daily Load ProfileDaily Load ProfileElectricity Electricity –– Daily Load ProfileDaily Load Profileyy yyyy yy

ElectricityHigh‐Demand Day in Summer High‐Demand Day in Winter

Electricity Generation MUST equal Electricity Consumption in pReal‐Time

An important constraint because there are very few good ways to store electricity on the scale required.

(Hydro‐Pumped(Hydro Pumped Storage is the only significant storage method at present).

7

method at present).

Electricity Electricity –– Daily Load ProfileDaily Load ProfileElectricity Electricity –– Daily Load ProfileDaily Load Profileyy yyyy yy

Germany: daily  electricity consumptionconsumption & fuel source contributions

8

Nuclear is especially well suited for Base Load Generation

E.g. Intermittency is a key problem for someE.g. Intermittency is a key problem for some renewable energy sources…

and will probably limit wind & solar contribution to no more than 20% to 30% for most countriesno more than 20% to 30% for most countries

9

The Energy Policy TriangleThe Energy Policy Trianglegy y ggy y g

Economics

Energy

Security of

Energy Policy

Security ofSupply

Environment

10

Greenhouse Gas Emissions from Electricity ProductionElectricity Generation: COElectricity Generation: CO22 EmissionsEmissionsGreenhouse Gas Emissions from Electricity Production

1400

22Whole Life CycleWhole Life Cycle

2891200

1400Indirect, from life cycle

Direct emissions from

176800

1000

grams

Direct emissions fromburning

Twin bars indicate range

113

1017600

800gCO2

equivalentper kWh

771017

790575

362200

400

101

per kWh

Electricity

236 4280

100 48 10 21 9362

0

200

Coal Gas Hydro Solar PV Wind Nuclear

17

Source: IAEA 2000

Coal Gas Hydro Solar PV Wind Nuclear

11

Atmospheric Impact of Fuel UseAtmospheric Impact of Fuel Use

Every 26 T n f U OTons of U3O8

“yellow cake” saves

1,000,000 Tons of

Atmospheric Atmospheric CO2 Relative

to Coal !to Coal !

Source: EU-EUR 20198, 200312

Structure of Global Electricity ProductionStructure of Global Electricity Production

HydroGlobal electricity 

i i 2006y16.0% generation in 2006: 

18,930 TWh

Coal41.0%

Renewables2.3%

Nuclear 14.8%

Note:1 TWh = 1 million MWh1 TWh = 1 billion kWh1 TWh   1 billion kWh

Oil5.8%

Natural gas20.1%

13

Structure of Global Electricity ProductionStructure of Global Electricity Production

Global electricity i i 2006generation in 2006: 

18,930 TWh

Note:1 TWh = 1 million MWh1 TWh = 1 billion kWh1 TWh   1 billion kWh

14

Fuels for Electricity Generation (USA)Fuels for Electricity Generation (USA)Fuels for Electricity Generation (USA)Fuels for Electricity Generation (USA)

Net Non emitting Sources ofNet U.S. Electric Generation (2006)

y ( )y ( )y ( )y ( )

Nuclear 19 5% Hydropower 7.1%

Net Non‐emitting Sources of Electricity

Nuclear

Generation (2006) 4,065 TWh

19.5% Nuclear 72.3%

Renewables                        

Natural Gas 20.1%

(non‐hydro)

2.5%

Petroleum 1.7%Geothermal 

Hydropower 24.9%

Coal 49.1% Wind 1.6%1.3%

Solar 0.05%

Fossil Fuels: 70.9%Fossil Fuels:  70.9%Non‐Emitting:  29.1%

15

Fuels for Electricity Generation (France)Fuels for Electricity Generation (France)Fuels for Electricity Generation (France)Fuels for Electricity Generation (France)y ( )y ( )y ( )y ( )

Fossil Fuels: 9.5%Fossil Fuels:  9.5%Non‐Emitting:  90.5%

16

Source: International Energy Outlook 2010: http://www.eia.doe.gov/oiaf/ieo/index.html

17

o Demand & Consumption of Electricity is growing faster than for of other forms of World

Electricity Energy

o CO2 Emissions related to Electricity Generation are growing faster than CO2Generation are growing faster than CO2emissions from sectors

CO

World

CO2

CO2World

Source:  International Energy Agency, CO2 Emissions from Fuel Combustion Highlights (2009 Edition)www.iea.org/co2highlights/co2highlights.pdf

18

Fact: Electricity and Heat production contributes aboutFact:  Electricity and Heat production contributes about 40% of the World’s CO2 emissions, and Demand for Electricity is growing faster than for other forms of EnergyElectricity is growing faster than for other forms of Energy.

Prediction: The World’s Electricity consumption isPrediction: The World s Electricity consumption is predicted to increase by ~75% in the next 25 years. The most rapid growth being in non OECD countriesmost rapid growth being in non‐OECD countries.

Challenge: To meet this growing demand for ElectricityChallenge: To meet this growing demand for Electricity, and to do it without accelerating Global Climate Change or causing other widespread Environmental Damagecausing other widespread Environmental Damage.

19

Characteristics of Nuclear Electricity GenerationCharacteristics of Nuclear Electricity Generationo High power density, small fuel volume, large output

o Environmental benefits: clean air, carbon‐free

o Costs: • Capital intensive: large units, high cost to build, low cost to operate

j f d l i i l ( l id l)• Major component of Base‐Load Electricity supply (alongside coal)

o Long reactor lifetimes: 40‐60 years

o Excellent Security of Supply (Uranium from politically stable countries, e.g. Australia & Canada)

E ll f d ( f USSR)Base Load

o Excellent safety record (except former USSR)

o Concerns over:• Safety of Long‐term Radioactive Waste Disposal• Safety of Long‐term Radioactive Waste Disposal• Nuclear Weapons Proliferation• Accidents – Three Mile Island, Chernobyl,          

and Fukushimaand Fukushima

20

Number of Energy Accidents from 1969 to 1996 Number of Energy Accidents from 1969 to 1996 with at least 5 Fatalitieswith at least 5 Fatalitieswith at least 5 Fatalitieswith at least 5 Fatalities

(Paul Scherrer Institut, "Severe Accidents in the Energy Sector“)

334350400

250300350

dent

s

187

150200250

of a

ccid

86 77

50100150

No. o

9 10

50

C l Oil N t l LPG H d N lCoal Oil Naturalgas

LPG Hydro-pow er

Nuclear

Nuclear  Power is EconomicalNuclear  Power is Economical

18 

US Electricity Production CostsYears: 1995‐2009   (Averages in 2009 cents per kilowatt‐hour)

C l (2 97 t/kWh)

14 

16 Coal    (2.97 cent/kWh)

Gas    (5.0 cent/kWk)

Nuclear    (2.03 cent/kWh)

Oil (12.4 cent/kWh)

10 

12 

/ kW

h

Oil    (12.4 cent/kWh)

Production Costs = Operation & Maintenance Costs + Fuel Costs

6 

8 

Cents 

2 

4 

0 

1994 1996 1998 2000 2002 2004 2006 2008 2010Year

Source: Nuclear Energy Institute, Washington, D.C. http://www.nei.org/resourcesandstats/documentlibrary/reliableandaffordableenergy/graphicsandcharts/uselectricityproductioncostsandcomponents/ 22

Investment Costs for 1,000 MWeInvestment Costs for 1,000 MWe

C l

Clean coal

Coal

Nuclear

Clean coal

Wind farm

NuclearNuclear Power Plants are

Natural gas

costly to build…

0 1 2 3 4

Billion US $23

Levelized Generating Costs of New Electricity Levelized Generating Costs of New Electricity G i C i iG i C i iGenerating CapacitiesGenerating Capacities

Coal

Clean coal … but Operational Costs are relatively low due to

Nuclearare relatively low due to low fuel (uranium) costs

N t l

Wind farm

0 1 2 3 4 5 6 7 8 9 10

Natural gas

US cents / kWh24

Fuel as a Percentage of Electric Power Fuel as a Percentage of Electric Power P d ti C tP d ti C t

Fuel as a Percentage of Electric Power Fuel as a Percentage of Electric Power P d ti C tP d ti C t

4% C i

Production CostsProduction CostsProduction CostsProduction Costs

Fuel26%

11%

7%4% Conversion

Fabrication

Waste Fund

Fuel

26%

26% Enrichment

O&M

78% Fuel94%

O&M

74% 52% Uranium

22%6%

Coal Gas Nuclear Nuclear Fuel CostComponents

Source: Global Energy Decisions/Energy Administration 25

Power Plant Land Use Required in km2/MWeSource: J. Davidson (2000)

Nuclear0 001/0 01

Coal0.001/0.010.01/0.04

Biomass5 2

1000 MWe POWER PLANTS RUNNING AT 100 % CAPACITY  5.2(8766 GWh/year)

Wind0.79

PV0.12

SolarThermal

0 08

Hydro0.07-0.37Geothermal

0.080.00326

Nuclear Energy WorldwideNuclear Energy Worldwide

Source: International Nuclear Safety Center, Argonne National Laboratory http://www.insc.anl.gov/pwrmaps/map/world_map.php

Reactor Types in use Worldwide,January 2004

27

Nuclear Energy WorldwideNuclear Energy Worldwide

Source: http://en.wikipedia.org/ 28

Nuclear Physics Nuclear Physics &&Nuclear Physics Nuclear Physics &&The Basics ofThe Basics ofThe Basics ofThe Basics of

Nuclear ReactorsNuclear ReactorsNuclear ReactorsNuclear Reactors

Units used for Nuclear Energy Calculations

electron volt:  eV

The energy an electron acquires when it moves throughThe energy an electron acquires when it moves through  an electric potential difference of one volt:

1 V 1 602 10 19J1 eV = 1.602 x 10‐19J

Nuclear Binding Energies are commonly expressed in unitsof mega‐electron volts (MeV)

1 MeV = 106 eV = 1.602 x 10 ‐13J

A particularly useful factor converts a given mass differencein atomic mass units to its energy equivalent in electronin atomic mass units to its energy equivalent in electronvolts:

1 u  =  931.5 x 106 eV  =  931.5 MeV

30

PERIODIC TABLESHOWING CHEMICAL ELEMENTS BY ATOMIC NUMBER AND CHEMICAL SYMBOL

1 (IA) GROUP NUMBER 18 (VIII)

1 2 13 14 15 16 17 2(Alternative designation in parentheses)

SHOWING CHEMICAL ELEMENTS BY ATOMIC NUMBER AND CHEMICAL SYMBOL

H (IIA) (IIIB) (IVB) (VB) (VIB) (VIIB) He3Li

4Be

5B

6C

7N

8O

9F

10Ne

11 12 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18(← VIIIA →)Na Mg (IIIA) (IVA) (VA) (VIA) (VIIA) (IB) (IIB) Al Si P S Cl Ar

19K

20Ca

21Sc

22Ti

23V

24Cr

25Mn

26Fe

27Co

28Ni

29Cu

30Zn

31Ga

32Ge

33As

34Se

35Br

36Kr

37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54Rb Sr Y Zr Nb Mo Tc Ru Rh Pd Ag Cd In Sn Sb Te I Xe

55Cs

56Ba

57La

72Hf

73Ta

74W

75Re

76Os

77Ir

78Pt

79Au

80Hg

81Tl

82Pb

83Bi

84Po

85At

86Rn

87 88 89 104 105 106 El t ith N St bl I t → R di ti87Fr

88Ra

89Ac

104 105 106

Lanthanides(Rare Earths)

58Ce

59Pr

60Nd

61Pm

62Sm

63Eu

64Gd

65Tb

66Dy

67Ho

68Er

69Tm

70Yb

71Lu

Elements with No Stable Isotopes→ Radioactive

(Rare Earths) Ce Pr Nd Pm Sm Eu Gd Tb Dy Ho Er Tm Yb Lu

Actinides 90Th

91Pa

92U

93Np

94Pu

95Am

96Cm

97Bk

98Cf

99Es

100Fm

101Md

102No

103Lr

Fissile Nuclides: 233U 235U 239PuElements in vertical columns have more or less similar chemistryFuels for Nuclear Reactors

31

Fissile Nuclides: 233U, 235U, 239Pu

Fertile Nuclides : 232Th, 238U

Elements, Isotopes, etc. Atomic nuclei are made up of protons and neutrons

The number of protons (= atomic number Z)The number of protons ( atomic number Z)determines Chemical Element: H, He, Li, Be, B, C,…, U

Neutrons provide the remaining nuclear mass, but may vary in number Np g , y y

Nuclei with same Z but different N of are called isotopes: e.g. 12C, 13C, 14C

M b A ( f & Z N)isotopes of carbon

Mass number A (= sum of protons & neutrons = Z + N)

e.g. Uranium‐235 (Z=92, N=143) , Uranium‐238 (Z=92, N=146)

Isotopes have identical chemistry (except for the usually negligible effects ofmass), but they have different nuclear properties

Not all nuclear combinations are stable ‐ many decay spontaneously and areradioactive

Specific combinations of protons and neutrons are generically called nuclides,and if unstable radionuclides 32

How to write an element’s symbol for a given isotope

XA

XZ

Example

Th90

232

90

Note: N=A‐Z

Definition: Atomic Mass Unit (u) = 12th of the mass of one 12C atom

Note: N A Z

( )

1 u=1.66054 ×10‐27 kg (so very small !)

Energy equivalent of 1 u is 931.5 MeV33

The proton and neutron numbers for the most common isotopes of several elements

The nucleus gets larger as the number of protons and neutrons increases

34

Segrè Chart of the NuclidesSegrè Chart of the Nuclides

deuteron

Interactive on‐line version:

protonneutron

http://www.nndc.bnl.gov/nudat2/atomic masses 35

Proton Mass = 1.007825 u

Neutron Mass = 1.008665 u

Mass Sum = 2.016490 uMass Sum 2.016490 u

Deuteron Mass = 2.014102 u

Missing Mass

(M M M ) 0 002388(Mp + Mn – Md) = 0.002388 u

What happened to the mass?

36

Answer: It represents the Nuclear Binding Energy accordingAnswer: It represents the Nuclear Binding Energy according to Einstein’s mass-energy relation

E 2E=mc2

For the deuteron example this isFor the deuteron example, this is…

BE = 0.002388 u x 931.5 MeV/u

= 2.22 MeV (the binding energy of the deuteron)

o To break the deuteron apart we must put this energy inp p gy

o If we form a deuteron from a free proton and a free neutron then we get this energy outthen we get this energy out

(here free means unbound)

37

But it’s often more convenient to think in terms of…

binding energy per nucleon       

For Deuteron: BE/A = 2 22MeV/2 = 1 11 MeV/nucleonFor Deuteron:  BE/A = 2.22MeV/2 = 1.11 MeV/nucleon

Energy fromFISSION

Energyfrom b h d hfromFUSION

For both Fusion and Fission there is an increase inBinding Energy per nucleon → Energy is released

Atomic Mass (A)38

Note: 1) Nucleon number is conserved (i e the number of nucleons remains1) Nucleon number is conserved (i.e. the number of nucleons remains

the same in all nuclear reactions and radioactive processes)

2) E i l d f N l R ti ( f i fi i2) Energy is released from a Nuclear Reaction (e.g. fusion, fission, radioactive decay, etc.) only when it results in:

o an increase in total binding energyo a decrease in total mass (these two things are actually

identical, because of E=mc2) Overview:Overview:

Energy from FissionChain reaction and thermal neutron reactorsChain reaction and thermal neutron reactorsControl of ReactorsUranium and the Open Fuel CycleUranium and the Open Fuel CycleTypes of Fission ReactorsNuclear SafetyNuclear Safety

39

E g Suppose one 238U nucleus (Z=92) splits into two 119Pd nuclei (Z=46)

Energy from Nuclear FissionEnergy from Nuclear FissionE.g. Suppose one 238U nucleus (Z=92) splits into two 119Pd nuclei (Z=46) –spontaneous fission – and apply conservation of mass-energy…

( ) ( ) 922705118Pd050785238U 119238 MM 238U( ) ( )( ) ( )[ ] MeV/u 5.931Pd2U

u922705.118Pd ,u050785.238U119238

119238

××−=

==

MMQMM 238U

splits

Q is positive when energy is released (and mass ↓)

MeV191=Q119Pd119Pd

On the atomic scale, 191 MeV is an enormous amount of energy…its about 50 million times the energy involved in the formation of aCO l l f b t (C) d l l (O )

fissionfragments

CO2 molecule from one carbon atom (C) and an oxygen molecule (O2)

In Fission this energy mostly goes to the KE of the Fission Fragments (the two 119Pd nuclei in the above case) The fission fragments slow down and stop over a119Pd nuclei in the above case). The fission fragments slow down and stop over a very short distance (in any material, e.g. fuel rod)…and KE is converted to HEAT.

40

Spontaneous Fission: a Radioactive ProcessSpontaneous Fission: a Radioactive Process– happens all by itself

– with a (very long) half‐lifewith a (very long) half life

– according to the radioactive

decay law

– of no importance for reactors

Neutron Induced Fission– induced by absorption of a neutron

– happens the instant the neutron is absorbed

2 3 t l itt d– 2 or 3 neutrons are also emitted

– therefore possibility of a chain reaction

– vitally important process for nuclear reactors

41

vitally important process for nuclear reactors

Neutron Induced Fission &Neutron Induced Fission &F l f R tF l f R tFuels for ReactorsFuels for Reactors

There are 3 main nuclides with sufficiently long half‐lives and largeThere are 3 main nuclides with sufficiently long half lives and large enough fission cross‐sections that that they readily undergo neutron induced fission, and are useful for fission reactors

Of these, only one exists naturally on Earth:   Uranium‐235

But only 0.72% of natural Uranium atoms  are 235U atoms, nearly all the rest (99 28%) are 238U atomsall the rest (99.28%) are 238U atoms

A nucleus which undergoes fission when absorbing a neutron of any energy (fast or slow) is said to be Fissiley gy (f )

The three fissile nuclides are:

233U T / = 1 59 x 105 years (artificial) fission “probability” = σ = 531 barnsU T1/2 = 1.59 x 10 years (artificial) fission  probability  = σf = 531 barns

235U T1/2  = 7.04 x 108 years (natural) fission “probability” = σf = 585 barns

239Pu T = 2 44 x 105 years (artificial) fission “probability” = σ = 750 barnsPu T1/2 = 2.44 x 105 years (artificial) fission  probability  = σf = 750 barns

42

3 Options for Induced Fission…3 Options for Induced Fission…

The fission of U‐235 was discovered by Otto 

238U and 232Th are said to be fertile nuclides → neutron absorption by 

fissile

Uranium-235

yHahn and Lise Meitner in 1938.

these nuclei leads to fissile nuclei:

238U → 239PuUranium 235(0.7% of all U)

Pu‐239 as a fissile fuel

U→ u232Th → 233U

fertilefissile

Pu‐239 as a fissile fuel was discovered by Glenn Seaborg in March 1941

Uranium-238(99.3% of all U)

Plutonium-239March 1941.

f til fissileU‐233 as a fissile fuel was discovered by Seaborg’s student John

fertile fissile

Thorium-232(100% of all Th)

Uranium-233

Seaborg s student John Gofman in February 1942. 43

A slow moving neutron induces fission in A slow moving neutron induces fission in UraniumUranium‐‐235235

fission fragment

fission fragment

n3KrBanU 1921411235 ++→+ n3KrBanU 03656092 ++→+one of many possible “splits”

44

Energy released in this Fission Reaction…

n3KrBanU 10

9236

14156

10

23592 ++→+

M(235U) = 235.043929 uM(92Kr) = 91.926156 u 

ΣMin = 236.052594 uΣM t = 235 866562 u( )

M(141Ba) =140.914411 uM = 1 008665 u

ΣMout  235.866562 uΔM =  +0.186032 uQ +173 MeVMn = 1.008665 u

Mostly Q → KE of Fission Fragments → HEAT

Q = +173 MeV

Many other induced fission reactions occur, e.g. Note: 

n2ZrTenU 10

9540

13952

10

23592 ++→+

n3MoSnnU 11021311235 ++→+

i. Number of emitted neutrons varies! Average of 2.5 for 235U

ii. Energy released (Q) also varies a bit n3MoSnnU 04250092 ++→+ between reactions (i.e. different fission fragments coming out)

45

Using 200 MeV (equiv. ΔM= 0.215 u) as average (sum of) energies released in g ( q ) g ( ) gfission, then fraction of 235U mass converted to energy for this reaction is ΔM /M(235U) = 0.215/235 = 9.1x10‐4

So almost 1/1000th of mass → energy

If we do this with 1 kg of pure 235U, the energy released is:

E = 9.1x10‐4 x 1 kg x (3.0x108 m/s)2 = 8.2x1013 J= 2.3x107 kWh   (thermal energy)

More realistically, if we start with 1 kg of 5% enriched U (5% 235U, 95% 238U) then

E = 4.1x1012 J = 1.1x106 kWh   (thermal energy)( gy)

Equivalent to burning about 195 tons of coal.

46

U i iUranium is very “energy dense” by comparisonby comparison with other fuels

47

Discovery of nuclear fissionDiscovery of nuclear fission ‐‐ Heavy nucleus splits underneutron bombardment

Possibility first suggested by Ida Noddack in 1934Possibility first suggested by Ida Noddack in 1934

Otto Hahn & Fritz Strassman experiments in Berlin (1938) observed barium after bombarding uranium with fast neutrons Publishedbarium after bombarding uranium with fast neutrons. Published results in Naturwissenschaften, Jan 1939.

Otto Hahn communicated results secretly to his colleague, Lise Lise Meitner y gMeitner, who had fled Nazi Germany earlier the same year.Meitner & nephew Otto Frisch explained it as nuclear fission!

Published in British journal, Nature, j , ,in Feb 1939.

Hahn was award the 1944 Nobel Prize for      Ch i t f i i l diChemistry for original discovery

However, it was Lise Meitner who first realized the possibility of a chain reaction→ outgoing 

48

neutrons from one fission reaction producing one (or more) other fission reactionsfast neutron

An Uncontrolled Neutron Chain Reaction !

A chain reaction is one in which the products of an initial step

Reaction !

the products of an initial step initiate further reactions

Here, the three neutrons emitted by the fission reaction (far left) strike other U-235 nuclei, and induce fission in them

... Producing more neutrons, which can go on to strike moreU-235 nuclei...U 235 nuclei...

49

Slow Neutrons for Induced Nuclear Fission in ReactorsSlow Neutrons for Induced Nuclear Fission in Reactors

The Fast Neutrons (KE ~ 1 MeV) emitted from the fission reaction cannot sustain a chain reaction. The probability of fission is much larger for Slow Neutrons and a fission chain reaction can occur.

To get a self‐sustaining chain reaction the fast 

slow neutron

neutrons have to be slowed‐down to thermal energies (KE ~ 1/10th eV). This is done by arranging for them to make many collisions with l l i ( h h d d t i

fast neutron

low‐mass nuclei (such as hydrogen, deuterium, or carbon).

The material with lots of low low mass nuclei isThe material with lots of low low‐mass nuclei  is called the moderator. Light‐water, heavy‐waterand graphite are all effective moderators.

Usually the moderator is physically separated from the fuel… see next 4 slides…

fastneutron

50

Role of Neutron Moderation in the Chain Reaction 

238U

235UNeutronNeutron

51

Role of Neutron Moderation in the Chain Reaction

3 outgoing fastneutrons emitted

52

Role of Neutron Moderation in the Chain Reaction

53

Role of Neutron Moderation in the Chain Reaction

slow neutron (due to loss of KE over many elastic collisions)over many elastic collisions)

54

A Controlled Chain ReactionA Controlled Chain Reaction

Clearly, an ever expanding chain reaction cannot be sustained. For controlled nuclear power, once we reach our desired power l l h i d d fi i d llevel we want each neutron induced fission to produce exactly one subsequent neutron induced fission (criticality: f = 1.00) → then the chain reaction is linear & the population of neutrons is p pconstant and the reactor power level is constant

55

Piecing Together a Nuclear ReactorPiecing Together a Nuclear ReactorPiecing Together a Nuclear ReactorPiecing Together a Nuclear Reactor

1. Fuel

2 M d2. Moderator

3. Control Rods

4. Coolant

5 Steam Generator5. Steam Generator

6. Turbine/Generator

7 P7. Pumps

8. Heat Exchanger

56

Basic Reactor ModelBasic Reactor ModelBasic Reactor ModelBasic Reactor Model4. Coolant

Electricity generated by 

turbine +

6.

turbine + generator

rol r

od

erator

Water in tertiaryge

r

. Fue

l

3. C

ontr

m gen

e

8.Fuel

tertiary coolant circuit (open)Ex

chang

1 3

5. Stea

Water in d

(open)

Heat 

7

secondary coolant circuit (closed)

7. Primary coolant circuit (closed) 57

Control RodsControl RodsControl rods are made of materials that readily absorb slowmaterials that readily absorb slow neutrons (i.e. elements with large neutron‐capture cross sections ( C d i H f i )(e.g. Cadmium or Hafnium)

The control rods are moved in Low Reactivity High Reactivity

and out of reactor core to control the number of neutrons

By controlling the number of neutrons, we can control the rate of fission (and therefore the rateof fission (and therefore the rate of Heat Production)

58

Reactor CoreReactor Core Coolant in (closed) primary circuit can Reactor CoreReactor Core be light‐water, heavy‐water, helium gas, CO2 gas, liquid Na metal, lead‐bismuth liquid metal, etc. For most 

Outgoing High‐Temperature Water

q ,operating reactors it’s light water.

Outgoing High Temperature Water

Control rods ofneutron‐absorbingsubstance

Uranium in fuel

Here light‐water functions as 

b thcylinders both :

Coolant, and

I i L T t W t

Moderator

Incoming Low‐Temperature Water

59

Nuclear Power Plant:Nuclear Power Plant:Pressurized Water Reactor (PWR)Pressurized Water Reactor (PWR)

Secondary CoolantSecondary Coolant Circuit (closed)

Tertiary Coolant 

Primary Coolant Circuit (closed)

Circuit (open)

Circuit (closed)

60

Components common to most types of reactors:Components common to most types of reactors:Components common to most types of reactors:Components common to most types of reactors:

Fuel: Usually in the form of uranium oxide (UO2): a ceramic material with a high melting point (2 800°C) In many reactor designs the UO fuel pellets are arranged inmelting point (2,800 C). In many reactor designs, the UO2 fuel pellets are arranged in long zirconium alloy (zircaloy) tubes to form fuel rods. Zircaloy is used because it is hard, corrosion‐resistant and permeable to neutrons. 

Moderator: This material slows down the neutrons released from fission reactions. Should primarily be composed of low‐mass atoms, so that fast neutrons give up a significant amount of KE in elastic collisions with low‐mass nuclei. By far the most g ycommon moderator materials are light water, heavy water or graphite (carbon).

Control Rods: These are made with neutron‐absorbing material such as cadmium, boron, gadolinium or hafnium. The control rods are gradually inserted or withdrawn from the core to control the rate of the chain reaction. The control rods are fully inserted to shutdown the reactor – bringing the chain reaction to an abrupt halt.

Coolant: A liquid or gas circulating through the core, removing heat from the core, and transporting it to the power generation plant. In some reactor designs, either l h h f b h h d d h llight‐water or heavy‐water, functions both as the moderator and the coolant.

61

Reactor Pressure Vessel (RPV): A robust steel vessel enclosing the reactor core, with inlets and outlets for the coolant. Usually the control rods also pass through the RPV.

Reactor Core: The volume inside the pressure vessel with an arrangement of fuel elements surrounded by moderator, flowing coolant, and control rods.

Steam Generator: Part of the cooling system where the heat from the reactor is used to make steam for the turbine. This unit is not present in BWR or HTGR reactors (see later)reactors (see later).

Containment: The structure around the reactor core which is designed to protect it from outside intrusion and to protect those outside from the effects of radiation infrom outside intrusion, and to protect those outside from the effects of radiation in case of any major malfunction inside. It is typically a meter‐thick concrete and steel structure. It contains the reactor core, coolant circulation pumps, and heat exchanger / steam generator.exchanger / steam generator.

62

Schematic of aSchematic of aPressurized Water Reactor (PWR)Pressurized Water Reactor (PWR)

http://www.nrc.gov/ 63

Schematic of aSchematic of aBoiling Water Reactor (BWR)Boiling Water Reactor (BWR)

http://www.nrc.gov/ 64

AREVAAREVA –– EPR (European PressurizedEPR (European Pressurized‐‐WaterWaterAREVA AREVA  EPR (European PressurizedEPR (European Pressurized Water Water Reactor)Reactor)

• 4500 MWt (thermal)• 1650 MWe (electricity)• 1650 MWe (electricity)• 60 – yr Service Life3 4 C i• 3 – 4 yr Construction

• Multiple Barriers and Si l S f SSimple Safety Systems

http://www.youtube.com/user/arevaresources?blend=8&ob=5#p/a/f/2/K6kuN9njqIY65

U iU iUraniumUranium(and the (and the FrontFront EndEnd of the Fuel Cycle)of the Fuel Cycle)(and the (and the FrontFront--EndEnd of the Fuel Cycle)of the Fuel Cycle)

Basics of UraniumBasics of UraniumDiscovered in 1789 by Martin Klaproth, a German chemist, in the mineral called pitchblende 

It occurs in most rocks in concentrations of 2 to 4 parts per million (ppm)

About as common in the Earth's crust as tin, tantalum or germanium. It also occurs in seawater.

High density: 19.1 g/cm3

67

Uranium Ore to YellowcakeUranium Ore to Yellowcake

o Each ton of Uranium ore produces 1 to 2 5 kg ofproduces 1 to 2.5 kg of Uranium compounds

o Uranium ore is processed nearo Uranium ore is processed near the mine to produce “yellow cake”, which is predominantly , p yU3O8.

o Only 0.72% of natural uranium y(as‐mined) in the yellow cake is fissile U‐235.

o About 99.28% is U‐238 which is not fissile. But, as we’ll see later, the U‐238 is fertile.

68

Uranium ProductionUranium Production

69

Uranium ResourcesUranium Resources

70

Sustainability of Uranium Resources

71

From Start to FinishUraniumUraniumOpen

( h h)(or once‐through)  Fuel Cycle

Front End Back End

72

ConversionConversion

To enrich uranium it must be in gaseous form as UF6.  This step is called conversion.  First the yellow cake is converted to uranium dioxide UO22through a process of reacting it with hydrogen.  Then anhydrous hydrofluoric acid is used to make UF4.  Next the UF44 4is mixed with fluorine gas to make uranium hexafluoride.  This liquid is stored in steel drums and crystallizes.  y

73

EnrichmentEnrichment• To be used as fuel in most power reactors (for electricity 

generation), uranium must be enriched to 3‐5% U‐235  g ),• Yellow cake is converted into UF6 and this compound is 

enriched using gaseous diffusion or centrifuges• Centrifuges are the more modern and efficient technology• There are some reactor designs that run on natural (un‐

enriched) uraniumenriched) uranium

• Highly Enriched Uranium (HEU) up to ~90% U‐235 is used forup to  90% U‐235, is used for weapons and naval reactors

• Depleted Uranium (DU) with p ( )~0.25% U‐235 in produced as a by‐product of the enrichment processprocess

Pellets, Rods & AssembliesPellets, Rods & Assemblies,,o UO2 is a high melting point ceramico Fuel pellets are inserted into long zircalloy

8 mm

15 mm

o Fuel pellets are inserted into long zircalloy tubes to form fuel rods

o Zircalloy is permeable to neutrons o ircalloy is permeable to neutronsand very corrosion resistant

o The fuel rods are collected into b dl ( d b dl )bundles (~200 rods per bundle) called fuel assemblies

o Typically there could be ~175o Typically there could be  175 bundles in the reactor core

o It takes approximately 25 tons of pp yfuel to power one 1000 MWe reactor for a year

A fuel assembly that will produce energyA fuel assembly that will produce energy equivalent to burning 72,000 tons of coal

75

From a previous lecture… on COALFrom a previous lecture… on COALpp

So the fuel assembly on the previous slide is equivalent to a 9 mile long coal train!

76

Tour of a Boiling Water Reactor (BWR)Tour of a Boiling Water Reactor (BWR)Tour of a Boiling Water Reactor (BWR)Tour of a Boiling Water Reactor (BWR)

http://www.energy‐northwest.com/generation/cgs/index.php

77

Spent Nuclear FuelSpent Nuclear Fuel(and the (and the BackBack EndEnd of the Fuel Cycle)of the Fuel Cycle)(and the (and the BackBack--EndEnd of the Fuel Cycle)of the Fuel Cycle)

Spent Nuclear FuelSpent Nuclear Fuel• Most is U and Pu, which can be

recycled and ‘burned’

• Most heat produced by fission products decays in 100 yr

• Most radiotoxicity is in the1 metric tonne

of SNF* contains: Most radiotoxicity is in the actinides (TRU) could be transmuted and/or disposed in much smaller packages

of SNF contains:955.4 kg U8.5 kg Pu (5.1 kg 239Pu)

Minor actinides (MAs):0.5 kg 237Np0 6 kg Am0.6 kg Am0.02 kg Cm

Long-lived fission products (LLFPs):

0.2 kg 129I0.8 kg 99Tc Longer‐Lived Fission

Iodine & Tc  0.1%Short‐livedFission Prod.  0.2%

Uranium  95.5%g

0.7 kg 93Zr0.3 kg 135Cs

Short-lived fission products (SLFPs):

1.0 kg 137Cs0 7 k 90S

OtherPlutonium  0.9 %

Minor Actinides 0.1%

Longer‐Lived Fission Products  0.1 % 

0.7 kg 90Sr*33,000 MWD/MT, 10 yr cooling

Minor Actinides  0.1%

Stable Fission Products  3.1% 

79

At Reactor Storage of Spent FuelAt Reactor Storage of Spent FuelAt Reactor Storage of Spent FuelAt Reactor Storage of Spent FuelWet storage• The great majority of spent nuclear fuel is initially 

stored as spent fuel assemblies in water‐filled pools on power plant siteson power plant sites

• The pools provide radiation shielding and cooling 

Dry Storage• Spent Fuel is usually placed in dry cask storage after 5 years in wet 

storage (NRC regulation requires at least 1 year in wet storage)

http://infocusmagazine.org/5.2/eng_nuclear_plants.html

storage (NRC regulation requires at least 1 year in wet storage)• Dry cask storage uses concrete or steel 

containers as a radiation shield and is cooled b i t iby inert gas or air 

• The casks are built to withstand the elements and accidents and do not require electricity, q y,water, maintenance, or constant supervision

U.S. DOE

80

Spent Fuel Cooling PoolSpent Fuel Cooling PoolSpent Fuel Cooling PoolSpent Fuel Cooling Pool

http://www.uic.com.au/opinion6.html

81

Transport Cask for

Spent Nuclear FuelSpent Nuclear Fuel

82

Dry Cask StorageDry Cask StorageDry Cask StorageDry Cask Storage

http://library.thinkquest.org/17940/texts/nuclear_waste_storage/nuclear_waste_storage.html

83

Handling Nuclear WasteHandling Nuclear Waste• Waste Reprocessing

– Recondition for further use as fuelRecondition for further use as fuel• Waste Disposal

T– Temporary storage– Permanent disposal (geological repository)

Waste Disposal FundingWaste Disposal Funding• Funded by power customers

• 0.1 cent per kWh p

• About $18 billion collected to date

• About $6 billion has been spent• About $6 billion has been spent

– Yucca Mountain, elsewhere 84

How different to other wastes?How different to other wastes?How different to other wastes?How different to other wastes?Radioactive (a small proportion is highly radioactive)( p p g y )

Self‐heating due to radioactivity

Requires Shieldingq g

Contained and managed, not dispersed to environment

Radioactivity decays over time !

To ensure that no significant environmental releases occurover a period of about ten thousands of years a multiple

Radioactivity decays over time !

over a period of about ten thousands of years, a multiple‐barrier concept is used to immobilize the radioactiveelements in high‐level wastes and isolate them from thee e e ts g e e astes a d so ate t e o t ebiosphere. It involves stabilizing, containment and finally,remote disposal.

85

Amount (volume) of Radioactive WastesAmount (volume) of Radioactive Wastes

200

(from a 1000 MWe reactor for 1 year of operation)

200

200

m3m3

10070

Spent Nuclear 

70Fuel

0

10

2.50High Level Intermediate Level Low Level

Source: OECD NEA 1996

2.5

86

Wastes Wastes produced duringproduced duringFuelFuel PreparationPreparation and/orand/or PlantPlant OperationOperationFuel Fuel Preparation Preparation and/or and/or Plant Plant OperationOperationMillion tonnesper GWyr

on

0.5

per GWyr

Flue

 gas 

sulphu

rizatio

0.4de

s

0.3s  ation

0.1

0.2

Ash sweetening

 waste

adioactive 

aste (H

LW)

Flue

 gas

desulphu

riza

oxic

aste

0

A

Gas s Ra w

Oil Nuclear SolarNatural WoodCoal

Ash

d To w

Ash

Source: IAEA, 1997

Oil Nuclear SolarPV

Naturalgas

WoodCoal

87

Spent fuel transport

Spent fuel re‐processingVitrification

Basis: 33 000 MWd/tSource: Cogema

88

Planned Geological Repository for Planned Geological Repository for g p yg p ySpent Fuel in FinlandSpent Fuel in Finland

• Spent Fuel is placed in Cast Iron Insert – then in copper canister• canister is embedded in Bentonite clay

• then buried in Granite rock 500 meters underground

89

90

Yucca Mountain Project: Nuclear Fuel and Yucca Mountain Project: Nuclear Fuel and High Level Waste RepositoryHigh Level Waste Repository

• Much more secure repository than leaving high level waste at 60 

reactor sites around the USA

• On old atomic bomb testing base, inside a mountain

• The storage is above the water table

• The Yucca Mountain site would be 60% filled by present waste

• US government has legal commitment to the reactor industry

• Site has been studied extensively by scientists for over 20 years.

• Will store waste during its 10,000 year decay time.

91

Yucca Mountain, Nevada, USAYucca Mountain, Nevada, USA

92

Cross Section of Yucca MountainYucca Mountain Deep Geological R itRepository

93

Interior of Yucca MountainInterior of Yucca MountainInterior of Yucca MountainInterior of Yucca Mountain

http://library.thinkquest.org/17940/texts/nuclear_waste_storage/nuclear_waste_storage.html

94

Storage of HighStorage of High‐‐Level Wastes at Yucca MountainLevel Wastes at Yucca Mountain

95

Waste Isolation Pilot Plant (WIPP)Waste Isolation Pilot Plant (WIPP)The world's first fully licensed deep geologic repository for nuclear waste, owned and operated by the US p ygovernment.

Used as a research facilityfacility

Storage at 2,150 feet underground

Source: http://www.wipp.ws/index htmndex.htm

http://www.wipp.energy.gov/general/general_information.htm96

Waste Isolation Pilot Plant (WIPP), New Mexico, USAWaste Isolation Pilot Plant (WIPP), New Mexico, USA

97

WIPPWaste is placed in rooms 655 m underground that have been excavated within a 1000 m thick salt formation which has been geologically stable for more than 250 million years.250 million years.

The surrounding salt gradually “flows” inwards filling gaps andflows  inwards filling gaps and spaces – so that the waste canisters become completely surrounded by and embeddedsurrounded by, and embedded within, the salt formation.

98

Spent Fuel Can Be Transported Spent Fuel Can Be Transported Safely and SecurelySafely and Securely

• Spent fuel assemblies consist of inert ceramic pellets inside corrosion resistant zirconium alloy tubes

• Shipment occurs in massive steel transport canisters weighing t f tmany tens of tons

• Thousands of shipments in the U.S., and tens of thousands in Europe (where most spent fuel is reprocessed) have occurred without harm to a single member of the publicwithout harm to a single member of the public

• Spent fuel transport adds very small safety and security risks compared to the routine transport of much larger quantities of hazardous chemicals (liquefied natural gas, liquid chlorine, ( q g , q ,sulfuric acid, etc.)

99

Transportation Container DurabilityTransportation Container DurabilityA 120 ton locomotive, 

Transportation Container DurabilityTransportation Container Durability

travelling at 80 miles per hour, crashed broadside into a container on ainto a container on a flatbed

The impact demolished theThe impact demolished the train, but hardly dented the container

Average Average A lA lAnnual Annual RadiationRadiationRadiation Radiation Dose inDose inCanadaCanada

101