npl/iop teachers day 2007 do we need nuclear power?
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NPL/IoP Teachers Day2007
Do we need nuclear power?
In the event of an alarm sounding…
Do we need nuclear power?
Does Britian need
nuclear power?
How much electricity does Britain need?
Where does it come from?
How can we replace their generating
capacity?
What about the alternatives?
Radioactivity
Nuclear Power
Stations are due for closure.
Nuclear Fission
Pros and Cons
Chernobyl!
What about Fusion?
Tonight’s Talk
How is electricity generated?
How is electricity generated?
• Coil turning in a magnetic field
• Pistons driven by hot steam
• Chemical Reaction
• Wax
• C + O2 CO2
How is electricity generated?More generally
Type of power station
Electricity made by…
What makes coil turn?
Prime Energy Source
CoalCoil turning in a magnetic field
Turbine driven by hot steam
Chemical Reaction
Coal
C + O2 CO2
GasCoil turning in a magnetic field
Turbines driven by hot gas and steam
Chemical Reaction
Gas (methane)
C + O2 CO2
NuclearCoil turning in a magnetic field
Turbine driven by hot steam
Nuclear Reaction
U + n ???
Wind/WaveCoil turning in a magnetic field
Turbine driven by air or water flow
Solar energy
H + H He
How much electricity do we need?
Electricity Generation in UK Daily variations in 2001/2002
gigawatt (GW) billion watts =109 W= 1000000000 W
=10 Million Light bulbs
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Time of day
Minimum Summer Demand
Typical Summer Demand
Sleep Work0
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Typical Winter Demand
Maximum Winter Demand
1 gigawatt (GW)
billion watts =109 W
=10 Million 100 W light bulbs
Roughly speaking 1 large power station
Electricity Generation in UK Daily variations in 2001/2002
Required generating
capacity (GW)Summer Winter
Peak 40 50
Base 20 30
Daily Maximum- Daily Minimum 20
1 gigawatt (GW)
billion watts =109 W
=10 Million 100 W light bulbs
Roughly speaking 1 large power station
Electricity Generation in UK 2004
• Where do we use this electricity?
Domestic29%
Industry29%
Agriculture 1%Transport 2%
Public Adminsitration
5%
FuelIndustries
8%
Losses8%
Commercial18%
Lighting
How do we meet this demand?
Electricity Generation in UK
Typical Winter DemandThursday 6th December 2001Figure 2.5(b) - Typical Winter Demand (Thursday 6th December 2001)
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Nuclear
Gas (Combined Cycle)
Large Coal
12:00 18:00 24:00
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Imports
0:00
OtherPower
(GW)
Time of Day
Electricity Generation in UK Data from 2004
– Gas & Coal increasing
– Nuclear decreasing
– Hydro is at maximum
– Renewables increasing
Coal33%
Oil1%Gas
40%
Nuclear19%
Hydroelectric1%
Wind/Biomass/Landfill Gas3.5% Imports
2.5%
Forecast Demand
TWh
365 TWh
(365 days x 24 h)=
41 GW
Generation mix versus time
TWh
What’s the projection for nuclear capacity?
Current UK Nuclear CapacityHistory and Future
• Decline could be faster
15
10
5
0
Generating Capacity (GW)
GW
Electricity Generation in UK 2020
• In the future– Nuclear contribution
will decline rapidly– Renewables will
undoubtedly increase, but by how much?
– Coal and gas likely to rise in cost and supplies are insecure
Coal33%
Oil1%Gas
40%
??????????????????????????????
Hydroelectric1%
Wind/Biomass/Landfill Gas3.5% Imports
2.5%
Alternatives?
So what can we do?
Can we reduce demand?
What to do?Reduce Demand
• This is my families electricity usage for the last two years
• But can we force people and businesses to use less electricity?
2000 kWh
30% reduction£160 a year
Alternatives?
So reducing demand can help.
What can wind provide?
Wind Power (1)UK Wind in 2006
• UK has some of the best sites in Europe
• 118 Projects• 1446 Turbines• 1.338 GW
• 3 million tonnes CO2 reduction
Wind Power Could we get 10% (5.3 GW) of electricity from wind?
• Retain 3 GW of coal fired capacity as ‘backup’
3 GW
13 GW
• Build 5000 of the largest wind turbines
•Wind has problems of
–availability
–variability
• On average generates only 5.3 GW• Sometimes more: Sometimes less!• Can’t control when!
5.3 GW
Alternatives?
So wind can provide a lot of power,
but we can’t control when it is generated
Could we store some of the power?
Wind Power Storage?
• This is the electricity ‘Grid’.• Electricity needs to be generated
at exactly the time it is needed.• Storage is possible, but difficult:
– Pumped hydro as a backup to wind power, is more sustainable than conventional generation but is more costly.
• Variability limits likely maximum wind contribution to about 10%
Electricity Generation in UKPumped Storage
-1.5
-1.0
-0.5
0.0
0.5
1.0
1.5
0 6 12 18 24
Pum
ped
Sto
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(G
W)
Time of Day
Energy Storage
Energy Use
Other Alternatives?
So reducing demand can help.
And wind and stored energy could help too
What about solar electricity?
Solar Photo VoltaicStep 1
• Put this on your roof• 7 m2 • Twickenham
Solar Photo Voltaic Step 2
• Put these in your house
Solar Photo VoltaicHey presto!
• Average 146 W = 3.5 kWh/day (1277.5 kWh/year)
• More than 1 tonne CO2 reduction per year
• Cost in 2005: £9000
Daily generation rate
0.00
2.00
4.00
6.00
8.00
10.00
10 14 18 22 26 30 34 38 42 46 50 54 58 62
w eek #
kWh
/day
Other Alternatives?
Severn Tidal Barrage
Could generate 10% of UK
demand
5 GW
£15B
Other Alternatives?
• Reducing demand can help.• And wind and stored energy could help too. • A tidal barrage or lagoons is a ‘no brainer’• Solar energy is not sensible for most settings
But…
Summary
• 12 GW of CO2-free generating capacity will be retiring in the next 17 years
• We need to replace it with something! • Many possibilities but 12 GW is a lot of electricity
– Energy savings, Wind power & Storage– Also Wave Power, Tidal Power, ‘Clean Coal’– Even replacing it will not reduce CO2 emissions
• There is no easy answer
So let’s find out about nuclear power!
To understand nuclear power and how it works
we first need to understand about radioactivity
Remember this…
Electromagnetic waves
Atoms Heat
Electricity
‘Nuclear’ refersto the nucleus
of atoms
What is Radioactivity(2)…
• Normally nuclei act as heavy point-like centres for atoms
• More than 99.9% of the mass of every atom is made of nuclear matter
• More than 99.9% of the mass of your breakfast is made of nuclear matter
Nucleus
What is Radioactivity(3)…
• The number of protons (+) in the nucleus determines the number of electrons required to make the atom neutral
• This determines the chemical and physical properties of the atom
• But the number of neutrons in a nucleus can vary
What is Radioactivity(4)Example 39K, 40K and 41K
• Natural potassium is 2.4% of the Earth’s crust• Natural potassium (symbol K) has three isotopes
39K 40K 41K93.3% 0.01% 6.7%
19 protons
20 neutrons
20 + 19 = 39
Not radioactive
19 protons
21 neutrons
21 + 19 = 40
Radioactive
19 protons
22 neutrons
22 + 19 = 41
Not radioactive
Same number of protons
Different numbers of neutrons
What is Radioactivity(6)…
Three types of radioactivity • Named with the Greek a, b, c
alpha, beta, gamma• Nuclei with a ‘balanced’ number of protons and neutrons are stable
Isotopes with too many protons
Isotopes withtoo many neutrons
Alpha decay Beta decay
Emission of fast moving helium nucleus
Emission of fast moving electron
And gamma radiation And gamma radiation
Charge oscillations in nucleus
What is Radioactivity(8)Alpha () Decay
Alpha particlegamma ray
Nucleus with too many protons
Charge oscillations in nucleus
What is Radioactivity(9)Beta () Decay
Beta particlegamma ray
Nucleus with too many neutrons
Some radioactive things (10)
Let’s look at some radioactive things…Detectors
Cloud ChamberSupermarket Radioactivity
Radioactivity
What are the health risks
of ionising radiation?
Radioactive health risksIntroduction
• Radioactive emissions alpha, beta, gamma• If they pass living cells, they interact electrically and cause
damage.– Cells are killed– Can cause mutations and cancer– Very bad for you
• Fortunately we have evolved in a radioactive world
Radioactive health risksMeasurement units
Many ways of measuring radioactive dose• Optimal measure for effect on human health is the
Sievert
Radioactive health risksAnnual average UK dose
Source Dose (mSv)
Natural
Cosmic 0.26
Gamma rays 0.35
Internal 0.3
Radon 1.3
Artificial
Medical 0.37
Occupational 0.007
Fallout 0.005
Products 0.0004
Discharges 0.0002
Total 2.6
• Average annual dose to the UK population from all sources
• Average 0.0026 Sieverts• Average 2.6 milliSieverts• About 7 microSieverts /day
Radioactive health risksSources From the sky
About 100,000 cosmic ray neutrons and 400,000 secondary cosmic rays penetrate the average individual every hour
From the airAbout 30,000 atoms disintegrate each hour in our lungs and give of alpha, beta, and gamma radiation
From foodAbout 15 million
potassium 40 atoms and 7000 natural uranium
atoms disintegrate inside us each hour
From soil and building materialsOver 200 million gamma rays pass through the average individual each hour
Radioactive health risksCompared with other risks
Average annual risk of death in the UK from…
Smoking 10 cigarettes a day 1 in 200
Heart disease 1 in 300
All cancers 1 in 400
All causes, 40 years old 1 in 700
All radiation (2.6 mSv) 1 in 7,700
Accident in the home 1 in 15,000
Accident on the road 1 in 17,000
Homicide 1 in 100,000
Nuclear discharges 1 in 140,000
Pregnancy for mother 1 in 170,000
What is Nuclear Power?
Nuclear Power
How does it work?
Nuclear Fission (1)‘Fission means splitting’
• Some very heavy nuclei can be induced to fission i.e. split in two by the addition of a single neutron
• Nuclear fragments move very fast. As they interact with nearby atoms they cause tremendous heating One more ‘wafer thin’ neutron, Sir?
Nuclear Fission (2)Uranium
• Uranium has two common isotopes 238U and 235U– Uranium has 92 protons– The 238 or 235 is the total number of protons and neutrons
238U 235U
neutrons 238 – 92 = 146 235 – 92 = 143natural
uranium. 99.3% 0.7%Fissile? No Yes
Nuclear Fission (3)Uranium Fission
• 235U + n >>> 236U + n
• After a short while
• 236U >>> fragments + 3 n
Nuclear Fission (4)Chain reaction
• 235U + n >>> 236U >>> Fragments + 3n
Nuclear Fission (5)Chain reaction
• Each fission produces 3 extra neutrons on average
– If more than one neutron produces an additional fission• The rate of fission increases• If uncontrolled leads to a nuclear explosion
– If less than one neutron produces an additional fission• Then the rate of fission decreases• Nuclear reactions will die out
– If exactly one neutron produces an additional fission• Sustainable nuclear reaction
Nuclear Fission (6)Chain reaction
• Nuclear phenomena has always been associated with great hopes and great fears.
• Chicago• 3:25 P.M. December 2,
1942• Nuclear Age began• Gain = 1.0006
Nuclear Fission (6)Hopes
Arthur Compton • We entered the balcony at one end of the room. On the balcony a dozen scientists were
watching the instruments and handling the controls. Across the room was a large cubical pile of graphite and uranium blocks in which we hoped the atomic chain reaction would develop. Inserted into openings in this pile of blocks were control and safety rods. After a few preliminary tests, Fermi gave the order to withdraw the control rod another foot. We knew that that was going to be the real test. The geiger counters registering the neutrons from the reactor began to click faster and faster till their sound became a rattle. The reaction grew until there might be danger from the radiation up on the platform where we were standing. "Throw in the safety rods," came Fermi's order. The rattle of the counters fell to a slow series of clicks. For the first time, atomic power had been released. It had been controlled and stopped. Somebody handed Fermi a bottle of Italian wine and a little cheer went up.
• One of the things that I shall not forget is the expressions on the faces of some of the men. There was Fermi's face—one saw in him no sign of elation. The experiment had worked just as he had expected and that was that. But I remember best of all the face of Crawford Greenewalt. His eyes were shining. He had seen a miracle, and a miracle it was indeed. The dawn of a new age. As we walked back across the campus, he talked of his vision: endless supplies of power to turn the wheels of industry, new research techniques that would enrich the life of man, vast new possibilities yet hidden.
Nuclear Fission (6)Fears
Leo Szillard
• There was a crowd there and when it dispersed, Fermi and I stayed there alone. Enrico Fermi and I remained. I shook hands with Fermi and I said that I thought this day would go down as a black day in the history of mankind.
• I was quite aware of the dangers. Not because I am so wise but because I have read a book written by H. G. Wells called The World Set Free. He wrote this before the First World War and described in it the development of atomic bombs, and the war fought by atomic bombs. So I was aware of these things.
• But I was also aware of the fact that something had to be done if the Germans get the bomb before we have it. They had knowledge. They had the people to do it and would have forced us to surrender if we didn't have bombs also.
• We had no choice, or we thought we had no choice.
Nuclear Power Stations
What is Nuclear Power?
Sounds like a lot of trouble: Why bother?
Nuclear Fission (6)
• 1 kg natural uranium has a volume of 50 cm3
– Produces 40 thousand kWh– Equivalent to 16 tons of coal
• Nuclear energy is cleaner than coal– Lower radioactive emissions– Much less radioactive waste
• Conventional Power Stations– Don’t pay to clean up their waste (CO2)
Downsides?
OK so nuclear power is quite interesting.Are there any downsides?
• Possibility of catastrophic explosion• Radioactive waste• Possibility of nuclear terrorism
Catastrophic ExposionChernobyl
• 26 April 1986• 31 dead Immediately• Ultimate death toll
– 100?– 15,000?
Chernobyl Effect on UK
Chernobyl
Fall out from atmospheric
atomic weapons testing
Annual dose
(micro Sieverts)
1951 1988
Total radiation emissions were 20 times less than the emissions from the atmospheric bomb tests from 1945 to 1963.
Year
Radioactive waste (1)Low level waste
• Low level waste– Not very radioactive– Much of it is
‘precautionary’– No problem really
Radioactive waste (2)Intermediate level waste
• Intermediate level waste– Very radioactive– Quite a lot of it– Many different physical
forms– No problem with heat– Requires isolation for
thousands of years
Radioactive waste (3)High level waste
• High level waste– Used fuel rods– Intensely radioactive– Requires cooling– Chemical mess – Requires ‘management’
for around 50 years– Will remain intensely
radioactive for tens of thousands of years
Radioactive waste (4)Amounts in cubic metres
No permanent resting place has been found for the high level waste
Type of Waste
Year
2000
Year
2030
Low 424,000 1,411 ,000
Intermediate 100,000 260 ,000
High 1,200 3,000
Amounts in cubic metres
Nuclear terrorism (1)
• September 11, 2001? • What would happen if
terrorists flew an aeroplane into a nuclear reactor?
Do we need nuclear power?You need to decide?
Does Britian need nuclear power?
Consider • Our need to reduce carbon dioxide emissions• The risks & benefits of nuclear technology
– Do we want all countries to have nuclear power?• The effect on renewables
– Undermining or supporting?• The need to make decisions soon
– Build the next generation of nuclear power stations?– Or not?
Do we need nuclear power?
Does Britian need nuclear power?
FusionThe answer?
• Collect interstellar hydrogen and turn it into helium
• Build a fusion reactor bigger than the Earth!
• Position the reactor about 93 million miles away
• Call it the Super Universal Neutrino machine (or SUN)
The End
Thank you
Resources
Unused Slides
World Oil Production(projections)Oil prices will rise
Table
World Oil ProductionWe are close to ‘the midpoint’
GigaBarrels of OilAnnual Production
World Oil Production(the gap)
Electricity GenerationThe case for nuclear power
But is oil relevant to this problem?
(still plenty of gas and coal)
Electricity Generation in UK Pros and Cons
Type Pros ConsCO2
Kg/kWh
NuclearWell suited to
supplying base loadNot popular
Waste Problem0.010
WindClean, plentiful,
available in the UKFluctuating Supply
Unsightly?0.001
Radioactive health risksRadon
Radioactive health risksHeight above sea level
0.01 mSv per hour
15 km
0.005 mSv per hour
10 km
0.001 mSv per hour
7 km
0.0001 mSv per hour
2.5 km
Mexico City
Himalayas
Coal89.5%
Crude Oil10.4%
Hydro0.1%
Electricity Generation in UK 1950
• Back in 1950– Basically just coal
Electricity GenerationCO2 Emissions
1990: 160 million tons
2005: 150 million tons
2010: target: 135 million tons
Wind PowerEnvironmental Change Institute
• Wind has problems of– availability– variability
• Availability– On average a 3MW turbine only
generates 1 MW– Sometimes, it generates nothing!– Needs conventional back up
• Variability– If wind speed changes– 40 to 30 mph: No problem– 30 to 20 mph: Output halves!
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Sustainable Development Commission
Sustainable Development CommissionThe government’s independent watchdog on sustainable developmentReport March 2006
“The two overriding concerns for Government are the need to:
• reduce carbon dioxide (CO2) emissions as part of efforts to tackle climate change, and
• increase confidence in the security of energy supply.”
“Nuclear power is not the answer to tackling climate change or security of supply”
What is Radioactivity(5)Isotopes
• Nuclei with the same number of protons, but different numbers of neutrons are called isotopes
• Nuclei with an ‘unbalanced’ ratio of protons and neutrons are unstable
• Instability is caused by electrical repulsion between protonsactually a couple more but don’t worry about them for now
• Only nuclei with a ‘balanced’ number of protons and neutrons are stable
What is Radioactivity (7)Summary
Isotopes with too many protons
Isotopes withtoo many neutrons
Alpha decay Beta decay
Emission of fast moving helium nucleus
Emission of fast moving electron
And gamma radiation And gamma radiation
Current UK Nuclear CapacityWith retirement dates
• Current capacity is 12.4 GW
• Most of this will be retired by 2023– Possibly much earlier
• If we don’t replace it with nuclear power, what should we replace it with? – Energy savings?– A CO2 free technology?
• If we don’t replace the power stations with something, there will be power cuts!
http://www.dti.gov.uk/energy/nuclear/technology/history.shtml
Power Station Capacity GW Retirement
Calder Hall 0.194 2003
Chapelcross 0.196 2005
Sizewell A 0.420 2006
Dungeness A 0.450 2006
Oldbury 0.434 2008
Dungeness B 1.110 2008
Wylfa 0.980 2010
Hinkley Point B 1.220 2011
Hunterston B 1.190 2011
Hartlepool 1.210 2014
Heysham 1 1.150 2014
Heysham 2 1.250 2023
Torness 1.250 2023
Sizewell B 1.188 2035
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