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CCFE is the fusion research arm of the United Kingdom Atomic Energy Authority

Nuclear Fusion…..

Icarus flies too close to a fusion reactor.

Fall of Ikarus, Pieter Bruegel, Musées

Royaux des Boaux-Artes, Brussels

A talk by Robin Stafford Allen FIMechE

Monday 2nd September 2019

For Camberley and District U3A Members.

Fusion Power –

within our grasp?

Fusion --within our grasp?

• Purpose and outcomes.

– Explain the basics of Plasma and Fusion Physics.

– Introduce the JET, MAST and ITER machines.

– Explain some of the terminology and technology.

– But first – WHY?

Present annual consumption / person

0.7 TCE

12.5 TCE6 TCE

1.4 TCE

Fossil FuelsAll-world conventional oil production will peak in 5-15 years

And then there is

Global Warming …

Fossil FuelsAll-world conventional oil production will peak in 5-15 years

And then there is

Global Warming …

Summary

• We need base-load energy for the future– Fossil fuels reserves (oil and gas) are running low

– Global Warming means• Fossil Fuel with total carbon capture.

• Fission.

• Fusion (magnetic or laser).

• A technology yet to be found.

• “Renewables” are not the answer, they are a diversion.

• And now to Physics…..

Structure of the average atom.

The number of protons define the element

Hydrogen has ONE proton

Helium has 2 protons

Lithium has 3 protons

Beryllium has 4 protons

……………..

Carbon has 6 protons

……………..

Iron has 26 protons

……………..

Uranium has 92 protons

Isotopes.

• The same element can have other forms.

• Hydrogen (1) has a proton and no neutron.

– Usually called simply Hydrogen; Sometime termed “protium”

• Hydrogen (2) has 1 proton and 1 neutron.

– Usually called “Deuterium”

• Hydrogen (3) has 1 proton and 2 neutrons.

– Usually called “Tritium”.

Fusion Process Introduction

• Fusion

A fusion reaction occurs when two

light nuclei (ions) approach each

other so closely that they fuse.

Methods being investigated include:

– Magnetic Confinement fusion

(Tokamak’s)

– and Inertial Confinement fusion

(Lasers).

Fusion Process Introduction

•Lawson’s CriterionUsable Fusion is feasible if Lawson

criterion is exceeded

“Plasma density”,

“Plasma temperature” and

“Confinement Time” are all sufficient at

the same time).

Typical numbers required are:

•Plasma density ~0.000001

atmospheres (million times less than

atmosphere),

•Plasma temperature 150 million

degrees C (million times room

temperature)

•Confinement time ~5-10s.

A PLASMA

A ”soup” of ions, and electrons,

D + T Fusion

D + T a (3.5 MeV) + n (14.1 MeV)

Ash Plasma

heating

Energy

production

1 gram of D and T reacted is equivalent to burning 10,000,000 grams of coal or gas.

On a gallon of D and T a car would go 300,000,000 miles theoretically.

Mass deficit

E=Dmc2

In the process of fusion, 0.4% of the mass of the nuclei is lost and released as energy.

Plasma, Magnetic Confinement and

Interaction with the Wall

Motion of ions and electrons without magnetic field

With magnetic field

Motion in all directions

Particle contact with

the wall

Ordered particles

motion

Reduced (minimised)

contact with the wall

Bend it around into a Torus

Ohmic Heating.

• The first of three forms of

“Additional Heating”

• The transformer effect.

• This is used to drive a huge

current through the plasma.

• Used in the early stages of

heating the plasma.

• Not much use once the

temperature is up to

50 million °C as the plasma is

too good a conductor by then.

RF Heating (Radio Frequency)

• Cyclotron frequency

– Charged particles in a magnetic field have a natural frequency of

gyration in the plane perpendicular to the field - the cyclotron

frequency. For electrons in a tokamak, the cyclotron frequency is

typically a few tens of GHz, and for ions, a few tens of MHz.

Neutral Beam Heating

• A beam of VERY

energetic fast particles.

• Ions, can be accelerated

but cannot penetrate to

magnetic field without

being recombined with

electrons to make

electrically neutral

particles.

– Analogy is a blow-lamp!

A pulse on JET

Disruptions

• Disruption

– Sudden loss of the plasma – it “goes out” with, usually a bang!

• Disruption information

– During a disruption forces of over 600 tonnes have been recorded. It is an audible bang!

– Vessel movements up to 8 or 9mm have been seen. (JET weighs 2,800 tons, and is now restrained on hydraulic dampers) .

– Anecdotally, there is a seismic station north of Oxford which can detect the vibrations from a JET disruption. Apparently the spectrum is different from the spectrum of an earthquake.

A pulse on JET

Flywheel Generators

Progress on JET

Can we improve the tokamak?

Spherical

Tokamak

Spherical Tokamak

MAST-UPGRADE

Spherical Tokamak

The Next Step - ITER

Construction costs €20 Billion in 15 years

Construction in Cadarache - France

Construction began in 2007/8

Operation in 2025

ITER Machine 2018

ITER site in 2018

Transporter• A dummy load of 360

concrete blocks will

be loaded onto the

special self propelled

platform (88 axles,

352 wheels) to travel

the whole length of

the itinerary..

• Its weight and dims. –

800 tons, 40 metres

long, 9 metres wide,

11 metres high –

mimic the most

exceptional ITER

A Fusion Powerplant

Lithium blanket captures

energetic neutrons from the

fusion process and serves

two purposes.

Boils water in a heat

exchanger to produce

steam to drive a generator.

The Lithium and neutron

react to produce Tritium, one

of the primary fuels in the

fusion process.

Hydrogen from Fusion?

• High temperature catalytic thermo-chemical cracking of water

• Heat (800C or more) + 2H2O 2H2 + O2

• Only real candidate technologies are solar thermal, electric, or nuclear power. Fusion is safer, cleaner than fission.

HTR-10

Source: Solar Developments

So what’s holding us back?

• Money – limited funding.

– The big experiments are being done in sequence

JET → ITER → DEMOResults in the “30-year-rule”!

– D-T experiments: 1997, 2020, and 2025?

• Technical Limitation.

– Materials, and materials research.– The high-energy neutrons generally damage materials and

can only realistically be studied within fusion machines.

“Nuclear fusion…would

provide an inexhaustible

supply of energy without

pollution or global warming.”

(Professor Stephen Hawking)

“We know how to do fusion

as physicists, how it works.

It is an engineering solution

that is within our grasp.”

(Professor Brian Cox)

ITER News.

• Fusion - the neglected alternative

"In the current energy policy debate the longer-term prospects for a sustainable energy supply have been lost from view. Especially the potential of nuclear fusion are hardly perceived in the public debate", writes Dennis Wesselbaum, the author of an article recently published by the renown Institute for World Economy based in Kiel, Germany. In his conclusion, the Macro-Economist writes: "Our society can not afford not to invest into this technology."

Advantages of Fusion …

• Fusion has little or no environmental impact – No greenhouse

gasses.

• Fusion will not produce any ‘long-lived’ radioactive waste.

• There is no risk of critical safety events e.g. ‘meltdown’.

• The fuels are abundant. Lithium in the earth’s crust, and…

Deuterium is freely available in …. Water.

Advantages of Fusion …

Fusion has little or no environmental impact – No greenhouse gasses.

Fusion should not produce any ‘long-lived’ radioactive waste.

There is no risk of critical safety events e.g. ‘meltdown’.

The fuels are abundant. Lithium in the earth’s crust, and

Deuterium is freely available in …. Water.

Any Questions?

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