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NPL/IoP Teachers Day2007 Do we need nuclear power?
Do we need nuclear power? What about Fusion? How much electricity does Britain need? Where does it come from? Chernobyl! Does Britian need nuclear power? Nuclear Power Stations are due for closure. Nuclear Fission Pros and Cons Radioactivity What about the alternatives? How can we replace their generating capacity?
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
Electricity Generation in UK Daily variations in 2001/2002 1 gigawatt (GW) billion watts =109 W =10 Million 100 W light bulbs Roughly speaking 1 large power station gigawatt (GW) billion watts =109 W = 1000000000 W =10 Million Light bulbs
Electricity Generation in UK Daily variations in 2001/2002 1 gigawatt (GW) billion watts =109 W =10 Million 100 W light bulbs Roughly speaking 1 large power station
Electricity Generation in UK 2004 Lighting • Where do we use this electricity?
Electricity Generation in UK Other Imports Power (GW) Typical Winter Demand Thursday 6th December 2001 50 40 Large Coal 30 20 Gas (Combined Cycle) 10 Nuclear 0 0:00 6:00 12:00 18:00 24:00 Time of Day
Electricity Generation in UK Data from 2004 • Gas & Coal increasing • Nuclear decreasing • Hydro is at maximum • Renewables increasing
Forecast Demand 365 TWh (365 days x 24 h) = 41 GW TWh
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
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 get10% (5.3 GW) of electricity from wind? • Wind has problems of • availability • variability • Build 5000 of the largest wind turbines 13 GW • On average generates only 5.3 GW • Sometimes more: Sometimes less! • Can’t control when! • Retain 3 GW of coal fired capacity as ‘backup’ 5.3 GW 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 atexactlythe 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. • Variabilitylimits likely maximum wind contribution to about 10%
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
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… Electricity ‘Nuclear’ refersto the nucleusof atoms Heat Electromagnetic waves 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 Same number of protons Different numbers of neutrons • Natural potassium is 2.4% of the Earth’s crust • Natural potassium (symbol K) has three isotopes
What is Radioactivity(6)… Three types of radioactivity • Named with the Greek a, b, c a alpha, b beta, g gamma • Nuclei with a ‘balanced’ number of protons and neutrons are stable
What is Radioactivity(8)Alpha (a) Decay Nucleus with too many protons Alpha particle gamma ray Charge oscillations in nucleus
What is Radioactivity(9)Beta (b) Decay Nucleus with too many neutrons Beta particle gamma ray Charge oscillations in nucleus
Some radioactive things (10) Let’s look at some radioactive things… Detectors Cloud Chamber Supermarket Radioactivity
Radioactivity What are the health risks of ionising radiation?
Radioactive health risksIntroduction • Radioactive emissionsa alpha, b beta, g 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 • Average annual dose to the UK population from all sources • Average 0.0026 Sieverts • Average 2.6milliSieverts • About 7microSieverts /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 food About 15 million potassium 40 atoms and 7000 natural uranium atoms disintegrate inside us each hour From the air About 30,000 atoms disintegrate each hour in our lungs and give of alpha, beta, and gamma radiation From soil and building materials Over 200 million gamma rays pass through the average individual each hour
What is Nuclear Power? Nuclear Power How does it work?