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Nuclear Energy
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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: [email protected]: 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%
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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.)
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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
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