ADSR systemsand their contribution to our energy needs

Roger Barlow

DIUS visit

Manchester, 16th September 2008

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Problem

Fossil Fuels

• Cause global warming

• Politically dangerous

• Becoming less abundant

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Solution

• Renewable energy?

• Restrict consumption??

• Nuclear power ???

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Nuclear power

Problems (real or perceived)

• Dangerous

• Long-term waste disposal

• Proliferation of nuclear weapons

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Reactors

ConventionalRun with k=1

Exactly: k<1 stopsk>1 explosion

Sub CriticalRun with k<1

Use accelerator to supply extra neutrons

Hence: Accelerator Driven Subcritical Reactor (ADSR)

Each fission absorbs 1 neutron and produces ~2.5

Some neutrons lost, leaving k neutrons to produce k fissions

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ADSRs

“Manifestly Safe”Switch off accelerator and

reaction stopsEnergy balance is OK:

need 5-10% of power to run accelerator

Can use Thorium as fuel

Accelerator

Spallation Target

Core

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Thorium

Fertile, not fissile 232Th +n 233U • Much smaller waste problems (no long-

lived actinides)• Proliferation resistant

– No 235U equivalent– Fissile 233U contaminated by ‘too hot to

handle’ 232U

• Abundant. (Like Lead) And spread around

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Energy Amplifier (Rubbia)

Idea has been around for years

Nobody’s built one yet!

Feeling is that the accelerator is the weak point.

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Waste from ADSR

Needs storing – but not forever

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Accelerator requirements

Proton Energy ~ 1 GeV For 1GW thermal power:• Need 3 1019 fissions/sec (200 MeV/fission)• 6 1017 spallation neutrons/sec (k=0.98 gives 50 fissions/neutron)• 3 1016 protons/sec (20 spallation neutrons each)Current 5 mA. Power = 5 MWReliable! Spallation target runs hot. If beam stops, target cools and

stresses and cracks: no more than 3 trips per year

Compare: PSI cyclotron: 590 MeV, 2mA, 1MWISIS synchrotron: 800 MeV, 0.2mA, 0.1 MWMany trips per day

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Accelerator types

Cyclotron

Energy too high for classical cyclotron. On the edge for other types

FFAG

Looks like the answer

Similar to proton therapy machine except higher current and no need for variable energy extraction

Very similar to neutrino factory proton driver

Linac

Can do the job. But VERY expensive

Synchrotron

Current far too high.

Complicated (ramping magnets)

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FFAG ACCELERATORSFixed Field Alternating Gradient

Cyclotron

Constant Field

Orbit radius increases

All cyclic accelerators use magnetic fields to contain the particles

As the energy increases:

Synchrotron

Constant Radius

Field is ramped up

FFAG

Radius increases slightly

Particles move from low field to high field region

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FFAG

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EMMA:World’s firstnsFFAG

Design

Prototypes

Site

Production

First Beam

2009

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Formation of the Thorium Energy Amplifier Association: Universities and labs and industry

A research consortium aimed at • Networking (website, workshops)• Sharing knowledge, within and outside UK• Collaborative response to funding opportunities• Design of a Thorium ADSR, aimed at power generation

with transmutation as bonus. FFAG is baseline accelerator

Inaugurated here last week

A way forward

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ThorEA

• The Thorium Energy Amplifier Association – hereafter known as ThorEA – is an affiliation of academic institutions, research laboratories, industrial companies, and individual scientists, engineers, technologists and policy specialists who share a common interest in developing thorium as a nuclear fuel in accelerator-driven systems such as the energy amplifier.

• The overriding purpose of ThorEA is to provide a platform for discussion and a focus for action in thorium fuel and energy

amplifier technology and related topics including transmutation.

If you’re interested, see www.thorea.org

From the Articles of Association:

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Summary

ADSRs provide a possible form of Nuclear Power that avoids the problems of

• Critical accidents• Long-lived waste• ProliferationFFAGs may provide the best accelerator

technologyWe (UK, Particle Physicists, Manchester,

Cockcroft Institute) are working hard to make it happen