Turning Rocks into Gold (Electric gold, that is)

A miracle of modern alchemy

Energy Potentials in the Universe

• Hydrogen fusion (as well as other nuclei) – in our sun and all visible stars

• Uranium fission – on earth – both natural and man-made

• Radioactive decay – energy from our primordial “big bang” via supernovae

• Gravitation – drop a pencil, release some energy. Pick it up, store

some energy

Uranium is Natural • Our uranium was created in supernova

explosions in space, about 6.5 billion years ago – even before the earth was formed

• It is all around us, in soil and rock and water – mostly in low concentrations

– In some areas, uranium has been concentrated by the action of flowing water

• It is part of our natural environment – life on earth evolved in a bath of radiation

Uranium??

• It is radioactive – Uranium-238 decays by alpha particle emission to

thorium-234; it eventually transforms into lead-206

• Uranium-238 also splits by spontaneous fission – 2 or 3 neutrons are released by the fission fragments

• The fission and decay of natural uranium release (in the whole earth) about 24 million megawatts – this heats the core of the earth

– More than half of all geothermal energy leaving the earth’s surface comes from this radioactive decay

Nuclear Fission

• When two light nuclei fuse (join), mass is converted to energy

• When a heavy nucleus fissions (splits), mass is converted to energy

• When gasoline burns in your car, mass is converted to energy

Per atom, heavy element fission is much more energetic than fusion or chemical burning

What are some uses for Uranium?

• We use heat from fission to make steam for a steam turbine – more than half Ontario’s electricity comes from uranium

• We have used it to make nuclear bombs – and nations have formed an international organization

(IAEA) to guard against its use for this purpose

• We have used it to make attractive glass – until recently some glass-makers added uranium to glass.

Such uses are now banned, to protect our health

• We use it as ballast in B747 aircraft

Energy of Fission

• It takes 31 billion fission reactions to release one watt-second (one joule) of energy.

– Fission is sustained at a constant rate by neutrons emitted during earlier fissions, in a chain reaction

– The fragments (fission products) are at first highly radioactive, then rapidly decay to stable elements

– Most of the energy appears as heat in the fuel pellets. It is this energy that we use to boil water at high temperature and pressure

Energy Flows

Thermal energy (fuel)

Thermal energy (water)

Mechanical (turbine)

Co

nd

uct

ion

Bo

ilin

g

Fiss

ion

Energy in the atomic nucleus

Electrical (generator)

Induction

Your lights, toaster, stove

Tran

smis

sio

n

Losses to environment

Nuclear Fuel (pellet & bundle)

• Uranium dioxide – ceramic, melting point 2800 C

– It is slightly radioactive

– One pellet releases enough energy to make 2 slices of toast every minute for a year (about 1 million slices)

• Over 6 million fuel pellets are loaded in each reactor, in 5760 fuel bundles

– Darlington produces 3522 megawatts of electricity from 4 reactors

• The world’s supply of nuclear fuel is inexhaustible

Energy in the atomic nucleus

Thermal energy (fuel)

The Magnitude of the Hazard Varies

HA

ZA

RD

OF

NU

CL

EA

R F

UE

L

BEFORE

LOADING REACTOR

OPERATION

USED FUEL COOLDOWN

Ab

ou

t 7

ord

ers

of

mag

nit

ud

e

Ab

ou

t 300

years

• Used fuel decays rapidly at

first, then more slowly

• The “last nucleus” does not

decay for a very long time

• Hazard returns to the original

level after about 300 years

• This suggests “Put the

stuff back where you got

it”.

Making Electricity • Heat energy is pumped in high

pressure water to the boilers • Water is then boiled to produce

steam to drive a steam turbine • Induction transforms

mechanical energy into electrical energy

• Electricity is transmitted to you, the customer, all in about 30 seconds after fission

• About 70% of the total fission energy is lost to environment

Thermal energy (water)

Mechanical energy (turbine)

Electrical energy (generator)

Fuel -- A Small Part of Electricity Cost*

• Today, the uranium price is about $90 per kilogram – At this price we have enough to fuel 6000 thermal reactors for > 40 years – The uranium fuel contribution to electricity price is negligible – If the uranium price were half the price of gold, the price of electricity from

thermal reactors would double – If the uranium price were half the price of gold, it would be very profitable to

extract uranium from seawater – Seawater is known to contain enough uranium to supply 100% of the world’s

energy for 4000 years using thermal reactors or at least 600,000 years using fast reactors

– Uranium in seawater is constantly replenished by surface water runoff and by dissolution from the seabed.

– Thorium (another potential fuel) is more abundant than uranium in the earth’s crust

* D.Lightfoot et al, “Nuclear Fission Energy is Inexhaustible”, Proc. Climate Change

Technology Conference, EIC, Ottawa, May 2006

It’s Not all Sweetness and Light

• Fission must be controlled at a constant rate

• High pressure pipes must hold water

• Heat losses must not damage the environment

• Radiation must be contained

• Fission products (the ashes of fission) must be safely stored in the long term

• Electricity must be affordable

Today, we only use 1% of the energy in the fuel

Used Fuel Hazard vs Time (Another view)

Should we really worry so

much about this?

Daily Electricity Demand

Base Load

Intermediate

Load

Intermediate - reservoir limited

Tops

Peak

Frequency

Control

Nuclear energy

supply range

Daily Energy

Storage

How Many Power

Plants?

The Problem of Scale

1000

2000

1970

NU

CL

EA

R C

AP

AC

ITY

, G

We

2070

NU

CL

EA

R C

AP

AC

ITY

, E

J P

ER

YE

AR

100

200

300

600

500

400

800

700

900

Target 2: 2005 total

world energy from

nuclear

Target 1: 2005 world energy

supply from nuclear, except

for hydro and transportation

3000

4000

5000

6000

7000

Two hundred

1000 MWe units

built each year

for 30 years

8000

9000

One ambitious plan

(Dr. Yoon Chang, 2006)

17

Nuclear Fuel Pellet, compared with a penny

This pellet weigh about 30

grams. A similar pellet, in a

CANDU reactor, can

produce enough electricity

to toast one million slices of

bread during its time in the

reactor – about one year.

The pellet is made of

uranium dioxide. This is

a ceramic material

similar to that used to

make coffee cups.

It is safe to hold now – but it will be

intensely radioactive when taken out

of the reactor. After 300 years in safe

storage, you could once again pick it

up safely – but I would wear a glove.

Fuel Pellet, Bundle, and Reactor

CANDU FUEL BUNDLE

Here is an old friend of

mine holding a CANDU

fuel bundle. On average,

each bundle releases

about 500 kilowatts of

heat for one year. This is

enough heat to produce

electricity for about 25

Ontario homes.

Dr. William Garland, McMaster University

There are 5760 fuel bundles

in each Darlington reactor

Darlington Nuclear Power Plant

Four nuclear

reactors, producing

3520 megawatts of

electricity.