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

0

10

20

30

40

50

60

0.00 6.00 12.00 18.00 24.00

Act

ual

Nat

ion

al G

rid

Dem

and

(G

W)

Time of day

Minimum Summer Demand

Typical Summer Demand

Sleep Work0

10

20

30

40

50

60

0.00 6.00 12.00 18.00 24.00

Act

ual

Nat

ion

al G

rid

Dem

and

(G

W)

Time of day

Sleep Work

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)

0

10

20

30

40

50

60

00:0

0

01:0

0

02:0

0

03:0

0

04:0

0

05:0

0

06:0

0

07:0

0

08:0

0

09:0

0

10:0

0

11:0

0

12:0

0

13:0

0

14:0

0

15:0

0

16:0

0

17:0

0

18:0

0

19:0

0

20:0

0

21:0

0

22:0

0

23:0

0

50

40

30

20

6:000

Nuclear

Gas (Combined Cycle)

Large Coal

12:00 18:00 24:00

10

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

rage

(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!

0

20

40

60

80

100

0 10 20 30 40 50 60Per

cent

age

of m

axim

um g

ener

atio

n po

wer

Wind Speed (miles per hour)

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