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7/28/2019 Nuclear Power2012
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NBS-M018
Low Carbon Technologies and Solutions
2012
NUCLEAR POWERhttp://www2.env.uea.ac.uk/energy/nbs-m018/nbs-m018.htm
http://www2.env.uea.ac.uk/energy/energy.htm Alternate server under development
http://www.uea.ac.uk/~e680/energy/nbs-m018/nbs-m018.htm
http://www.uea.ac.uk/~e680/energy/energy.htm
N.K. Tovey () M.A, PhD, CEng, MICE, CEnv.. .., -
Energy Science DirectorCRedProject
HSBC Director of Low Carbon Innovation
http://www2.env.uea.ac.uk/energy/nbs-m018/nbs-m018.htmhttp://www2.env.uea.ac.uk/energy/energy.htmhttp://www.uea.ac.uk/~e680/energy/nbs-m018/nbs-m018.htmhttp://www.uea.ac.uk/~e680/energy/energy.htmhttp://www.uea.ac.uk/~e680/energy/energy.htmhttp://www.uea.ac.uk/~e680/energy/nbs-m018/nbs-m018.htmhttp://www.uea.ac.uk/~e680/energy/nbs-m018/nbs-m018.htmhttp://www.uea.ac.uk/~e680/energy/nbs-m018/nbs-m018.htmhttp://www.uea.ac.uk/~e680/energy/nbs-m018/nbs-m018.htmhttp://www.uea.ac.uk/~e680/energy/nbs-m018/nbs-m018.htmhttp://www2.env.uea.ac.uk/energy/energy.htmhttp://www2.env.uea.ac.uk/energy/nbs-m018/nbs-m018.htmhttp://www2.env.uea.ac.uk/energy/nbs-m018/nbs-m018.htmhttp://www2.env.uea.ac.uk/energy/nbs-m018/nbs-m018.htmhttp://www2.env.uea.ac.uk/energy/nbs-m018/nbs-m018.htmhttp://www2.env.uea.ac.uk/energy/nbs-m018/nbs-m018.htm7/28/2019 Nuclear Power2012
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NUCLEAR POWER
Background Introduction
5. Nature of Radioactivity
a. Structure of the Atom
b. Radioactive Emissions
c. Half Life of Elements
d. Fission
e. Fusion
f. Chain Reactions
g. Fertile Materials
6. Fission Reactors
7. Nuclear Fuel Cycle
8. Fusion Reactors
LectureSli Lecture 2 Lecture 3
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0
2000
4000
6000
8000
10000
12000
14000
1955 1965 1975 1985 1995 2005 2015 2025 2035
Installe
dCapacity(MW) New Build ?
ProjectedActual New Build
Assumes 10 new
nuclear power
stations are
completed (one
each year from
2019).
NUCLEAR POWER in the UK
Generation 1: MAGNOX: (Anglo-French design) three reactors ( two stations)
still operating on extended lives of 43 and 41 years
Generation 2a: Advanced Gas Cooled reactors (unique UK design)most
efficient nuclear power stations ever built - 14 reactors operating.
Generation 2b: Pressurised Water Reactormost common reactor Worldwide.UK has just one Reactor 1188MW at Sizewell B.
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0
100
200
300
400
500
600
1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025 2030
TWh
Nuclear new nuclear coal new coal CCS
oil Other Renewables onshore wind offshore wind
UK gas Imported gas Demand
Existing Nuclear
Existing Coal
Oil
UK Gas
Imported
Gas
New Nuclear
New Co
Other
Renewables
Offshore
Wind
Onshore
Wind
1 new nuclear station completed each year after 2020.
1 new coal station fitted with CCS each year after 2020
1 million homes fitted with PV each year from 2020 -
40% of homes fitted by 2030
19 GW of onshore wind by 2030 cf 4 GW now
Data for modelling derived from DECC & Climate Change Committee (2011) - allowing for
significant deployment of electric vehicles and heat pumps by 2030.
Our looming over-dependence on gas for electricity generation
4
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Historic and Future Demand for Electricity
Number of households will rise by 17.5% by 2025 and consumption
per household must fall by this amount just to remain static
0
50
100
150
200
250
300
350
400
450
500
1970 1975 1980 1985 1990 1995 2000 2005 2010 2015 2020 2025
ElectricityConsumption(TWh)
Business
as usual
Energy
Efficient
Future ?
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Carbon Dioxide Emissions
0
50
100
150
200
250
1990 1995 2000 2005 2010 2015 2020 2025
MTonnesCO2
Actual
Business as Usual
Energy Efficiency
The Gas Scenario
Assumes all new non-renewable
generation is from gas.
Replacements for ageing plant
Additions to deal with demand changes
Assumes 10.4% renewables by 2010
25% renewables by 2025
Energy Efficiency consumption
capped at 420 TWh by 2010
But 68% growth in gas demand(compared to 2002)
Business as Usual
257% increase in gas consumption
( compared to 2002)
Electricity Options for the Future
Gas Consumption
0
10
20
30
40
50
60
70
80
90
100
1990 1995 2000 2005 2010 2015 2020 2025
billioncubicme
tres Actual
Business as UsualEnergy Efficiency
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Energy Efficiency Scenario
Other Options
Some New Nuclear needed by 2025 if CO2
levels are to fall significantly and excessivegas demand is to be avoided
Business as Usual Scenario
New Nuclear is required even to reduceback to 1990 levels
Carbon Dioxide Emissions
0
50
100
150
200
250
1990 1995 2000 2005 2010 2015 2020 2025
MTonnesCO2
ActualGasNuclearCoal40:20:40 Mix
Carbon Dioxide Emissions
0
50
100
150
200
250
300
350
1990 1995 2000 2005 2010 2015 2020 2025
MtonnesCO2
Actual
Gas
Nuclear
Coal
40:20:40 Mix
25% Renewables by 2025
20000 MW Wind
16000 MW Other Renewables inc.
Tidal, hydro, biomass etc.
Alternative Electricity Options for the Future
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To District Heat Main ~
90oC
Boiler
Heat Exchanger
Combined heat and power can also be used with NuclearPower
e.g. Switzerland, Sweden, Russia
Nuclear Power can be used solely as a source of heat
e.g. some cities in Russia - Novosibirsk
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NUCLEAR POWER
Background Introduction
5. Nature of Radioactivity
a. Structure of the Atom
b. Radioactive Emissions
c. Half Life of Elements
d. Fission
e. Fusion
f. Chain Reactions
g. Fertile Materials
6. Fission Reactors
7. Nuclear Fuel Cycle
8. Fusion Reactors
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NATURE OF RADIOACTIVITY (1)
Structure of Atoms.
Matter is composed of atoms which consist
primarily of a nucleus of: positively charged PROTONS
and (electrically neutral) NEUTRONS.
The nucleus is surrounded by a cloud of
negatively charged ELECTRONS whichbalance the charge from the PROTONS.
PROTONS and NEUTRONS have
approximately the same mass
ELECTRONS are about 0.0005 times themass of the PROTON.
A NUCLEON refers to either a PROTON or a
NEUTRON
+
++
3p
4n
Lithium Atom
3 Protons 4 Neutrons
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NATURE OF RADIOACTIVITY (2)Structure of Atoms.
Elements are characterized by the number of PROTONS present
HYDROGEN nucleus has 1 PROTON HELIUM has 2 PROTONS
OXYGEN has 8 PROTONS
URANIUMhas 92 PROTONS.
Number of PROTONS is the ATOMIC NUMBER (Z)
N denotes the number of NEUTRONS.
The number of neutrons present in any element varies.
3 isotopes of hydrogen all with 1 PROTON:-
HYDROGEN itself with NO NEUTRONS
DEUTERIUM (heavy hydrogen) with 1 NEUTRON TRITIUM with 2 NEUTRONS.
only TRITIUM is radioactive.
Elements up to Z = 82 (Lead) have at least one isotope which is stable
Symbol D
Symbol T
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NATURE OF RADIOACTIVITY (3)
Structure of Atoms.
URANIUM has two main ISOTOPES
235U which is present in concentrations of 0.7% in naturally
occurring URANIUM
238U which is 99.3% of naturally occurring URANIUM.
Some Nuclear Reactors use Uranium at the naturally occurring
concentration of 0.7%
Most require some enrichment to around 2.5% - 5%
Enrichment is energy intensive if using gas diffusion
technology, but relatively efficient with centrifuge technology.
Some demonstration reactors use enrichment at around 93%.
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Radioactive emissions.
FOURtypes of radiation:-
1) ALPHA particles ()- large particles consisting of 2 PROTONS and 2 NEUTRONS
the nucleus of a HELIUM atom.
2) BETA particles () which are ELECTRONS
3) GAMMA - RAYS. () Arise when the kinetic energy of Alpha and Beta particles is lost
passing through the electron clouds of atoms. Some energy is used
to break chemical bonds while some is converted into GAMMA -
RAYS.
4) X - RAYS.
Alpha and Beta particles, and gamma-rays may temporarily
dislodge ELECTRONS from their normal orbits. As the electrons
jump back they emit X-Rays which are characteristic of theelement which has been excited.
NATURE OF RADIOACTIVITY (5)
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NATURE OF RADIOACTIVITY (6)
- particles are stopped by a thin sheet of paperparticles are stopped by ~ 3mm aluminium
- rays CANNOT be stopped they can be attenuated to safelimits using thick Lead and/or concrete
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U23592
Radioactive emissions.
UNSTABLE nuclei emit Alpha or Beta particles
If an ALPHA particle is emitted, the new element will have an
ATOMIC NUMBER two less than the original.
U235
92
NATURE OF RADIOACTIVITY (7)
If an ELECTRON is emitted as a result of a NEUTRON
transmuting into a PROTON, an isotope of the element ONE
HIGHER in the PERIODIC TABLE will result.
Th231
90
He4
2
Np235
93
e
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Radioactive emissions.
235U consisting of 92 PROTONS and 143 NEUTRONS is one
of SIX isotopes of URANIUM
decays as follows:-
NATURE OF RADIOACTIVITY (8)
URANIUM
235
U
alpha
THORIUM
231
Th
PROTACTINIUM
231PaACTINIUM
227Ac
Thereafter the ACTINIUM - 227 decays by further alpha and
beta particle emissions to LEAD - 207 (207Pb) which is stable.
Two other naturally occurring radioactive decay series exist.
One beginning with 238U, and the other with 232Th.
Both also decay to stable (but different) isotopes of LEAD.
beta alpha
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HALF LIFE.
Time taken for half the remaining atoms of an element to
undergo their first decay e.g:-
238U 4.5 billion years
235U 0.7 billion years
232Th 14 billion years
All of the daughter products in the respective decay series
have much shorter half - lives some as short as 10-7 seconds.
When 10 half-lives have expired,
the remaining number of atoms is less than 0.1% of theoriginal.
20 half lives
the remaining number of atoms is less than one millionth
of the original
NATURE OF RADIOACTIVITY (9)
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HALF LIFE.
From a radiological hazard point of view
short half lives - up to say 6 months have intenseradiation, but
decay quite rapidly. Krypton-87 (half life 1.8 hours)-
emitted from some gas cooled reactors - the radioactivity
after 1 day is insignificant. For long half lives - the radiation doses are small, and also
of little consequence
For intermediate half lives - these are the problem - e.g.
Strontium -90
has a half life of about 30 years which means it has a
relatively high radiation, and does not decay that quickly.
Radiation decreases to 30% over 90 years
NATURE OF RADIOACTIVITY (10)
A O A OAC (11) i i
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This reaction is one of several which
might take place. In some cases, 3daughter products are produced.
n
n
n
140Cs
93
Rb
235U
Some very heavy UNSTABLE elements exhibit FISSION e.g. 235U
NATURE OF RADIOACTIVITY (11): Fission
NATURE OF RADIOACTIVITY (12)
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FISSION
Nucleus breaks down into two or three fragments
accompanied by a few free neutrons and the release of verylarge quantities of energy.
Free neutrons are available for further FISSION reactions
Fragments from the fission process usually have an atomic
mass number (i.e. N+Z) close to that of iron. Elements which undergo FISSION following capture of a
neutron such as URANIUM - 235 are known as FISSILE.
Diagrams of Atomic Mass Number against binding energy per
NUCLEON enable amount of energy produced in a fissionreaction to be estimated.
All Nuclear Power Plants currently exploit FISSION reactions,
FISSION of 1 kg of URANIUM produces as much energy as
burning 3000 tonnes of coal.
NATURE OF RADIOACTIVITY (12)
NATURE OF RADIOACTIVITY (13) F i
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n
4He 2H
3H
Deuterium
Tritium
Deuterium Tritium fusion
(3.5 MeV)
(14.1 MeV)
In each reaction 17.6 MeV is liberated or 2.8 picoJoules (2.8 * 10-15J)
Fusion of light elements e.g. DEUTERIUM and TRITIUM produces
even greater quantities of energy per nucleon are released.
NATURE OF RADIOACTIVITY (13): Fusion
NATURE OF RADIOACTIVITY (14) Bi di E
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1) The energy released per nucleon in fusion reaction is much greater than the
corresponding fission reaction.
2) In fission there is no single fission product but a broad range as indicated.
NATURE OF RADIOACTIVITY (14): Binding Energy
0 50 100 150 200 250
Atomic Mass Number
-2
-4
-6
-8
-10
BindingEnergypernucleon[MeV]
Iron 56
Uranium 235Range of Fission
Products
Fusion Energyrelease per
nucleon
Fission Energy
release pernucleon
1 MeV per nucleon isequivalent to 96.5 TJ per kg
Redrawn from 6th report on Environmental Pollution Cmnd. 6618 - 1976
NATURE OF RADIOACTIVITY (15) F i
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Developments at the JET facility in Oxfordshire have achieved
the break even point.
Next facility (ITER) will be built in Cadarache in France.
Commercial deployment of fusion from about 2040 onwards
One or two demonstration commercial reactors in 2030s perhaps No radioactive waste from fuel
Limited radioactivity in power plant itself
8 litres of tap water sufficient for all energy needs of oneindividual for whole of life at a consumption rate comparable to
that in UK.
Sufficient resources for 1 10 million years
NATURE OF RADIOACTIVITY (15): Fusion
NATURE OF RADIOACTIVITY (16) Ch i R ti
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n
n
n235U
n
n
n
235
U
Slow neutron
Slow neutron
fast neutron
fast
neutron
Fast Neutrons are
unsuitable for sustainingfurther reactions
NATURE OF RADIOACTIVITY (16): Chain Reactions
NATURE OF RADIOACTIVITY (17)
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CHAIN REACTIONS
FISSION of URANIUM - 235 yields 2 - 3 free neutrons.
If exactly ONE of these triggers a further FISSION, then a
chain reaction occurs, and continuous power can be
generated.
UNLESS DESIGNED CAREFULLY, THE FREE
NEUTRONS WILL BE LOST AND THE CHAIN
REACTION WILL STOP.
IF MORE THAN ONE NEUTRON CREATES A NEW
FISSION THE REACTION WOULD BE SUPER-
CRITICAL
(or in layman's terms a bomb would have been created).
NATURE OF RADIOACTIVITY (17)
NATURE OF RADIOACTIVITY (18)
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CHAIN REACTIONS IT IS VERY DIFFICULT TO SUSTAIN A CHAIN
REACTION,
Most Neutrons are moving too fast
TO CREATE A BOMB, THE URANIUM - 235 MUST BE
HIGHLY ENRICHED > 93%,
Normal Uranium is only 0.7% U235
Material must be LARGER THAN A CRITICAL SIZE and
SHAPE OTHERWISE NEUTRONS ARE LOST.
Atomic Bombs are made by using conventional explosive tobring two sub-critical masses of FISSILE material together for
sufficient time for a SUPER-CRITICAL reaction to take place.
NUCLEAR POWER PLANTS CANNOT EXPLODE LIKE AN
ATOMIC BOMB.
NATURE OF RADIOACTIVITY (18)
NATURE OF RADIOACTIVITY (19)
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FERTILE MATERIALS
Some elements like URANIUM - 238 are not FISSILE, but
can transmute:-
NATURE OF RADIOACTIVITY (19)
n
238U
fast
neutron
239U
238UUranium - 238
239UUranium - 239
+n
ee
239NpNeptunium -239
239PuPlutonium -239
beta beta
239Np239Pu
PLUTONIUM - 239 is FISSILE and may be used in place ofURANIUM - 235.
Materials which can be converted into FISSILE materials are FERTILE.
NATURE OF RADIOACTIVITY (20)
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FERTILE MATERIALS
URANIUM - 238 is FERTILE as is THORIUM - 232
which can be transmuted into URANIUM - 233.
Naturally occurring URANIUM consists of99.3% 238U
which is FERTILE and NOT FISSILE, and 0.7% of235U
which is FISSILE. Normal reactors primarily use the
FISSILE properties of235U.
In natural form, URANIUM CANNOT sustain a chain
reaction: free neutrons are travelling fast to successfully
cause another FISSION, or are lost to the surrounds.
MODERATORS are thus needed to slow down/and or
reflect the neutrons in a normal FISSION REACTOR.
The Resource Base of235U is only decades
But using a Breeder Reactor Plutonium can be produced
from non-fissile 238U producing 239Pu and extending the
resource base by a factor of 50+
NATURE OF RADIOACTIVITY (20)
NATURE OF RADIOACTIVITY (21): Chain Reactions
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n
n
n235U
n
n
n
235
U
fast
neutron
Slow neutron
fast neutron
fast
neutron
n
Fast Neutrons are
unsuitable for sustainingfurther reactions
NATURE OF RADIOACTIVITY (21): Chain Reactions
Slow neutron
n
Insert a moderator to
slow down neutrons
Sustaining a reaction in a Nuclear Power Station
NUCLEAR POWER
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NUCLEAR POWER
Background Introduction
5. Nature of Radioactivity
6. Fission Reactorsa) General Introduction
b) MAGNOX Reactors
c) AGR Reactors
d) CANDU Reactorse) PWRs
f) BWRs
g) RMBK/ LWGRs
h) FBRs
i) Generation 3 Reactors
j) Generation 3+ Reactors
7. Nuclear Fuel Cycle
8. Fusion Reactors
FISSION REACTORS (1):
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FISSION REACTORS CONSIST OF:-
i) a FISSILE component in the fuel
ii) a MODERATOR
iii) a COOLANT to take the heat to its point of use.
The fuel elements vary between different Reactors
Some reactors use unenriched URANIUM i.e. the 235U in fuel elements is at 0.7% of fuel
e.g. MAGNOX and CANDU reactors,
ADVANCED GAS COOLED REACTOR (AGR) uses 2.5 2.8% enrichment
PRESSURISED WATER REACTOR (PWR) and BOILING WATERREACTOR (BWR) use around 3.5 4% enrichment.
RMBK (Russian Rector of Chernobyl fame) uses ~2% enrichment
Some experimental reactors - e.g. High Temperature Reactors (HTR) use
highly enriched URANIUM (>90%) i.e. weapons grade.
FISSION REACTORS (1):
FISSION REACTORS (2): Fuel Elements
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FISSION REACTORS (2): Fuel Elements
PWR fuel assembly:
UO2 pellets loaded into fuelpins of zirconium each ~ 3 m
long in bundles of ~200
Magnox fuel rod:
Natural Uranium metal barapprox 35mm diameter and
1m long in a fuel cladding
made of MagNox.
AGR fuel
assembly:
UO2 pellets loaded
into fuel pins of
stainless steel each~ 1 m long in
bundles of 36.
Whole assembly in
a graphite
cylinder
Burnable
poison
FISSION REACTORS (3):
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No need for the extensive coal handling plant.
In the UK, all the nuclear power stations are sited on the
coast so there is no need for cooling towers.
Land area required is smaller than for coal fired plant.
In most reactors there are three fluid circuits:-
1) The reactor coolant circuit
2) The steam cycle
3) The cooling water cycle.
ONLY the REACTOR COOLANT will become radioactive
The cooling water is passed through the station at a rate of
tens of millions of litres of water and hour, and the outlet
temperature is raised by around 10oC.
FISSION REACTORS (3):
FISSION REACTORS (4):
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REACTOR TYPES summary 1
MAGNOX - Original British Design named after the magnesium
alloy used as fuel cladding. Four reactors of this type were built inFrance, One in each of Italy, Spain and Japan. 26 units were built
in UK.
They are only in use now in UK. On December 31st 2006,
Sizewell A, Dungeness A closed after 40 years of operation leavingOldbury with two reactors is now continuing beyond its original
extended 40 year life. Wylfa (also with 2 reactors) will close this
year or next. All other units are being decommissioned
AGR - ADVANCED GAS COOLED REACTOR - solelyBritish design. 14 units are in use. The original demonstration
Windscale AGR is now being decommissioned. The last two
stations Heysham II and Torness (both with two reactors), were
constructed to time and have operated to expectations.
FISSION REACTORS (4):
FISSION REACTORS (5):
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REACTOR TYPES - summary SGHWR - STEAM GENERATING HEAVY WATER
REACTOR - originally a British Design which is a hybridbetween the CANDU and BWRreactors.
PWR - Originally an American design ofPRESSURIZED WATER REACTOR (also known as a LightWater Reactor LWR). Now most common reactor.-
BWR - BOILING WATER REACTOR - a derivativeof the PWRin which the coolant is allowed to boil in thereactor itself. Second most common reactor in use.
RMBK - LIGHT WATER GRAPHITE MODERATINGREACTOR (LWGR)- a design unique to the USSR whichfigured in the CHERNOBYL incident. 16 units still inoperation in Russian and Lithuania with 9 shut down.
FISSION REACTORS (5):
FISSION REACTORS (5):
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REACTOR TYPES - summary
CANDU - A reactor named initially after CANadian
DeUterium moderated reactor (hence CANDU),alternatively known as PHWR(pressurized heavy waterreactor). 41 currently in use.
HTGR - HIGH TEMPERATURE GRAPHITE
REACTOR - an experimental reactor. The original HTR inthe UK started decommissioning in 1975. The new PebbleBed Modulating Reactor (PBMR) is a development of thisand promoted as a 3+ Generation Reactor by South Africa.
FBR - FAST BREEDER REACTOR - unlike allprevious reactors, this reactor 'breeds' PLUTONIUM fromFERTILE 238U to operate, and in so doing extends resourcebase of URANIUM over 50 times. Mostly experimental atmoment with FRANCE, W. GERMANY and UK, Russia
and JAPAN having experimented with them.
FISSION REACTORS (5):
MAGNOX REACTORS (also known as GCR):
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FUEL TYPE - unenriched URANIUMMETAL clad in Magnesium alloy
MODERATOR - GRAPHITE
COOLANT - CARBON DIOXIDE DIRECT RANKINE CYCLE
- no superheat or reheat efficiency ~20% to 28%.
ADVANTAGES:-
LOW POWER DENSITY- 1 MW/m3.Thus very slow rise in temperature infault conditions.
UNENRICHED FUEL GASEOUS COOLANT
ON LOAD REFUELLING
MINIMAL CONTAMINATIONFROM BURST FUEL CANS
VERTICAL CONTROL RODS - fallby gravity in case of emergency.
MAGNOX REACTORS (also known as GCR):
DISADVANTAGES:-
CANNOT LOAD FOLLOW[Xepoisoning]
OPERATING TEMPERATURELIMITED TO ABOUT 250oC - 360oC
limiting CARNOT EFFICIENCY to ~40 -
50%, and practical efficiency to ~ 28-30%.
LOW BURN-UP - (about 400 TJ pertonne)
EXTERNAL BOILERS ON EARLY
DESIGNS.
ADVANCED GAS COOLED REACTORS (AGR):
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FUEL TYPE - enriched URANIUMOXIDE - 2.3% clad in stainless steel
MODERATOR - GRAPHITE
COOLANT - CARBON DIOXIDE SUPERHEATED RANKINE CYCLE
(with reheat) - efficiency 39 - 41%
ADVANTAGES:- MODEST POWER DENSITY- 5 MW/m3.
slow rise in temperature in fault conditions.
GASEOUS COOLANT(40- 45 BAR cf 160
bar for PWR) ON LOAD REFUELLINGunder part load
MINIMAL CONTAMINATION FROMBURST FUEL CANS
RELATIVELY HIGHTHERMODYNAMIC EFFICIENCY 40%
VERTICAL CONTROL RODS- fall bygravity in case of emergency.
ADVANCED GAS COOLED REACTORS (AGR):
DISADVANTAGES:-
MODERATE LOAD FOLLOWING
CHARACTERISTICS SOME FUEL ENRICHMENT
NEEDED. - 2.3%
OTHER FACTORS:-
MODERATE FUEL BURN-UP - ~
1800TJ/tonne (c.f. 400TJ/tonne forMAGNOX, 2900TJ/tonne for PWR).
SINGLE PRESSURE VESSEL with
pres-stressed concrete walls 6m thick.
Pre-stressing tendons can be replaced
if necessary.
CANDU REACTOR (PHWR):
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FUEL TYPE - unenriched URANIUMOXIDE clad in Zircaloy
MODERATOR - HEAVY WATERCOOLANT - HEAVY WATER
ADVANTAGES:- MODEST POWER DENSITY- 11 MW/m3.
HEAVY WATER COOLANT -lowneutron absorber hence no need for
enrichment. ON LOAD REFUELLING- and very
efficient indeed permits high load factors.
MINIMAL CONTAMINATION fromburst fuel can -defective units can beremoved without shutting down reactor.
MODULAR:- can be made to almost any size
CANDU REACTOR (PHWR):
DISADVANTAGES:-
POOR LOAD FOLLOWINGCHARACTERISTICS
CONTROL RODS AREHORIZONTAL, and therefore cannotoperate by gravity in fault conditions.
MAXIMUM EFFICIENCY about 28%
OTHER FACTORS:-
MODERATE FUEL BURN-UP - ~
MODEST FUEL BURN-UP - about1000TJ/tonne
FACILITIES PROVIDED TO DUMP
HEAVY WATER MODERATORfromreactor in fault conditions
MULTIPLE PRESSURE TUBES
instead of one pressure vessel.
PRESSURISED WATER REACTORS PWR (WWER):
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FUEL TYPE - 3 4% enrichedURANIUM OXIDE clad in Zircaloy
MODERATOR - WATER
COOLANT - WATER
ADVANTAGES:-
GOOD LOAD FOLLOWINGCHARACTERISTICS - claimed forSIZEWELL B. - most PWRs are NOToperated as such.
HIGH FUEL BURN-UP- about2900TJ/tonne
VERTICAL CONTROL RODS - drop bygravity in fault conditions.
PRESSURISED WATER REACTORS PWR (WWER):
DISADVANTAGES:-
ORDINARY WATER as COOLANT -
pressure to prevent boiling (160 bar). If
break occurs then water will flash to
steam and cooling will be less effective.
ON LOAD REFUELLING NOTPOSSIBLE - reactor must be shut down.
SIGNIFICANT CONTAMINATION OF
COOLANT CAN ARISE FROM BURST
FUEL CANS - as defective units cannot be
removed without shutting down reactor.
FUEL ENRICHMENT NEEDED. - 3-4%.
MAXIMUM EFFICIENCY ~ 31 - 32%
latest designs ~ 34%
OTHER FACTORS:-
LOSS OF COOLANT also means LOSS
OF MODERATOR so reaction ceases - but
residual decay heat can be large.
HIGH POWER DENSITY - 100 MW/m3,
and compact. Temperature can rise
rapidly in fault conditions. NEEDS active
ECCS.
SINGLE STEEL PRESSURE VESSEL 200mm thick.
BOILING WATER REACTORS BWR:
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FUEL TYPE - 3% enriched URANIUMOXIDE clad in Zircaloy
MODERATOR - WATER
COOLANT - WATER
ADVANTAGES:-
HIGH FUEL BURN-UP- about2600TJ/tonne
STEAM PASSED DIRECTLY TOTURBINEtherefore no heat exchangersneeded. BUT SEE DISADVANTAGES..
BOILING WATER REACTORS BWR:
DISADVANTAGES:-
ORDINARY WATER as COOLANTbut
designed to boil: pressure ~ 75 bar.
CONTROL RODS MUST BE DRIVEN
UPWARDS - SO NEED POWER IN FAULT
CONDITIONS. Provision made to dump water(moderator in such circumstances).
ON LOAD REFUELLING NOT
POSSIBLE - reactor must be shut down.
SIGNIFICANT CONTAMINATION OF
COOLANT CAN ARISE FROM BURST
FUEL CANS - as defective units cannot beremoved without shutting down reactor.ALSO IN SUCH CIRCUMSTANCES
RADIOACTIVE STEAM WILL PASS
DIRECTLY TO TURBINES.
FUEL ENRICHMENT NEEDED. - 3%.
MAXIMUM EFFICIENCY ~ 34-35%
OTHER FACTORS:-
LOSS OF COOLANT also means LOSS
OF MODERATOR so reaction ceases - but
residual decay heat can be large. HIGH POWER DENSITY - 100 MW/m3,
and compact. Temperature can rise
rapidly in fault conditions. NEEDS active
ECCS.
SINGLE STEEL PRESSURE VESSEL 200
mm thick.
RMBK (LWGR): (involved in Chernobyl incident)
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FUEL TYPE - 2% enriched URANIUMOXIDE clad in Zircaloy
MODERATOR - GRAPHITE
COOLANT - WATER
ADVANTAGES:-
ON LOAD REFUELLING
VERTICAL CONTROL RODSwhich
can drop by GRAVITY in faultconditions.
NO THEY CANNOT!!!!
RMBK (LWGR): (involved in Chernobyl incident)
DISADVANTAGES:-
ORDINARY WATER as COOLANT -
flashes to steam in fault conditions
hindering cooling.
POSITIVE VOID COEFFICIENT !!! -
positive feed back possible in some fault
conditions -other reactors have negative
voids coefficient in all conditions.
IF COOLANT IS LOST moderator will
keep reaction going.
FUEL ENRICHMENT NEEDED. - 2%
PRIMARY COOLANT passed directly to
turbines. This coolant can be slightly
radioactive.
MAXIMUM EFFICIENCY ~30% ??
OTHER FACTORS:-
MODERATE FUEL BURN-UP - ~
MODEST FUEL BURN-UP - about1800TJ/tonne
LOAD FOLLOWINGCHARACTERISTICS UNKNOWN
POWER DENSITY probablyMODERATE?
MULTIPLE PRESSURE TUBES
FAST BREEDER REACTORS (FBR or LMFBR)
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FUEL TYPE - depleted Uranium or UO2surround PU in centre of core. Allelements clad in stainless steel.
MODERATOR - NONE
COOLANT - LIQUID METAL
ADVANTAGES:-
LIQUID METAL COOLANT- atATMOSPHERIC PRESSURE. Willeven cool by natural convection in eventof pump failure.
BREEDS FISSILE MATERIALfromnon-fissile 238U increases resource base50+ times.
HIGH EFFICIENCY(~ 40%)
VERTICAL CONTROL RODS drop byGRAVITY in fault conditions.
FAST BREEDER REACTORS (FBR or LMFBR)
DISADVANTAGES:-
DEPLETED URANIUM FUEL
ELEMENTS MUST BE REPROCESSED
to recover PLUTONIUM and sustain the
breeding of more plutonium for future use. CURRENT DESIGNS have SECONDARY
SODIUM CIRCUIT
WATER/SODIM HEAT EXCHANGER.
If water and sodium mix a significant
CHEMICAL explosion may occur which
might cause damage to reactor itself.
OTHER FACTORS:- VERY HIGH POWER DENSITY - 600
MW/m3 but rise in temperature in fault
conditions limited by natural circulation of
GENERATION 3 REACTORS: the EPR1300
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Schematic of Reactor is very similar to later PWRs (SIZEWELL) with 4Steam Generator Loops.
Main differences? from earlier designs.
Output power ~1600 MW from a single turbine(cf 2 turbines for 1188 MW at Sizewell).
Each of the safety chains is housed in a separate building.
GENERATION 3 REACTORS: the EPR1300
Construction is under way at
Olkiluoto, Finland.
Second reactor under
construction in
Flammanville, France
Possible contender for new
UK generation
Efficiency claimed at 37%
But no actual experience
and likely to be less
GENERATION 3 REACTORS: the AP1000
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GENERATION 3 REACTORS: the AP1000
A development from SIZEWELL
Power Rating comparable with SIZEWELL
Will two turbines be used ?? Passive Cooling water tank
on top water falls by gravity
Two loops (cf 4 for EPR)
Significant reduction in
components e.g. pumps etc.
Possible Contender for new
UK reactors
GENERATION 3 REACTORS: the ACR1000
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GENERATION 3 REACTORS: the ACR1000
A development from CANDU with added safety features less Deuterium
needed
Passive emergency cooling as with AP1000
See Video Clip of on-line refuelling
ESBWR: Economically Simple BWR
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S W : co o c y S p e W
A derivative of Boiling Water Reactor for which it is claimed has
several safety features but which inherently has two disadvantages of
basic design
Vertical control rods which must be driven upwards
Steam in turbines can become radioactive
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Kung Hei Fat Choi !
Gong Xi Fa Cai !
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