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Accelerator Driven Subcritical Reactors. or How Accelerators can save the planet Roger Barlow Institute of Physics Meeting Imperial College April 12 th 2010. Roger Barlow: ADSRs. 1. We have to stop burning fossil fuels. They cause climate change - PowerPoint PPT Presentation
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Accelerator Driven Subcritical Reactors
or
How Accelerators can save the planet
Roger BarlowInstitute of Physics Meeting
Imperial CollegeApril 12th 2010
Roger Barlow: ADSRs 1
We have to stop burning fossil fuels
Roger Barlow: ADSRs
1.They cause climate change
2.They are increasingly concentrated in countries with dodgy politics
3.They are going to run out
2
Renewables can’t fill the gap
Roger Barlow: ADSRs
Even major (country-scale) developments will not be enough
Alternatives (windmills,tidal power, solar power, improved insulation, retreat to the middle ages) can’t supply the deficit
Turbine typically delivers 1.5 MW peak
3
Nuclear Power
Fossil fuels will need to be replaced by a basket of alternativesIt is hard (impossible?) to put such a basket together without nuclear power
Big issues (real or in the eyes of the public?) with:•Safety: Chernobyl and 3 Mile Island•Waste disposal. Storage for millenia - NIMBY•Proliferation. Rogue states and terrorist organisations
4Roger Barlow: ADSRs
Safe Subcritical Reactors
Conventional:Run 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
5Roger Barlow: ADSRs
ADSRs
“Manifestly Safe”Switch off accelerator and reaction stopsEnergy balance is OK: need 5-10% of power to run
accelerator
Accelerator
Spallation Target
Core
6Roger Barlow: ADSRs
OFF
ThoriumWhen do we run out Uranium? In about 100 years, unless we move to a fast breeder system.
Uranium is not the only possibility…
Thorium: Fertile, not fissile 232Th +n 233Th233Pa233U • Abundant. (Like lead) and spread around• Much smaller waste problems (no long-lived minor actinides)• Proliferation resistant
7Roger Barlow: ADSRs
Thorium Reactors
Thorium mixed with U or Pu• MSR (1964)• Winfrith (Dragon)• Fort St Vrain (1976)• Shippingport (1977)• Germany Julich (1967), THTR (1983)• Kurchatov Institute/Thorium Power• India
But Thorium and ADSRs go togetherRoger Barlow: ADSRs 8
Energy Amplifier (Rubbia)
Thorium ADSR fast reactor
Idea has been around for years
Lead/Bismuth Eutectic acts as target and coolant and moderator.
Nobody’s built one yet!
Feeling is that the accelerator is the weak point.
9Roger Barlow: ADSRs
Waste from ADSR
Needs storing – but not foreverMinor Actinides (Np, Cm, Cf) are not produced
10Roger Barlow: ADSRs
Transmutation
• Fast neutron flux can burn actinides produced by conventional reactors. MYRRHA project.
• Also destroy most-problematic fission products (e.g. 99Tc: soluble, T½=211,000 Y) by ‘Adiabatic Resonance Crossing’. Lead moderator to ensure neutrons hit the resonance for absorption
11Roger Barlow: ADSRs
Fuel lifetime
Typical Uranium/Plutonium PWR needs refuelling in months, limited by fission product neutron poisoning
Typical Thorium fuel lasts for years as fission product effects counterbalanced by increasing amounts
of 233U Do we need reprocessing? Yes. Not for recycling
of fuel but because 233U storage is problematic Roger Barlow: ADSRs 12
Proliferation
Thorium fuel system does not produce weapons
• Explains why nuclear power went the U/Pu route back in the 1950’s
• Solves today’s dilemma of states like Iran
Specifically1. There is no equivalent to a 235U
device2. Constructing the equivalent of a
Pu device, using 233U, is made very difficult due to contamination with 232U
13Roger Barlow: ADSRs
Summary so far
ADSRs: Nuclear Power that avoids the real and perceived problems of criticality accidents
Thorium as fuel removes problems of • Long-lived waste• Proliferation
Worth a closer look… Lots to do in understanding The reactor. Thorium cross sectionsThe Target and spallationFuel reprocessingAccelerators
14Roger Barlow: ADSRs
Let's look at this
Accelerator requirements
Proton Energy ~ 1 GeV gives ~20 spallation neutrons per proton.
For 1GW thermal power:• Need 3 1019 fissions/sec (200 MeV/fission)• 6 1017 spallation neutron induced fissions/sec (k=0.98
gives 50 fissions/neutron)• 15 1017 spallation neutrons/sec• 7.5 1016 protons/sec Current ~10 mA. Power ~ 10 MW Compare: PSI cyclotron: 590 MeV, 2mA, 1MWISIS synchrotron: 800 MeV, 0.2mA, 0.1 MW
15Roger Barlow: ADSRs
Accelerators for ADSRs
Cyclotron
Energy too high for classical cyclotron. On the edge for other types
FFAG
Looks like the answer
“Cyclotron currents at Synchrotron energies”
Simplicity = reliability
Linac
Can do the job. But VERY expensive
Synchrotron
Current far too high.
Complicated (ramping magnets)
16Roger Barlow: ADSRs
Reliability: the 3rd Frontier
In the real world:Accelerators often trip for
seconds/hours/days. They are complicated systems operating in real world environments
But there are complex real world pieces of apparatus that trip rarely. Planes, computers, radio sets…
17Roger Barlow: ADSRs
Target runs hot. If beam stops, target cools & stresses & cracks: Require not more than 3 trips per year (or similar numbers)
Straw man scheme: AESIR
Accelerator Energy System with Inbuilt Reliability
18Roger Barlow - UK ADSR programme
Design and build a Thorium ADSR, hopefully with an nsFFAG providing the accelerator
(Other accelerator solutions are acceptable.)
1 GeV 10 mA protons with high reliability and low losses (don't want contamination problems)
Stage I: LOKI
The Low-key demonstrator35 MeV H- system -or H+ or H
2+
High current. (1 mA? 10 mA?) Commercial source RF Quadrupole Standard LinacStudy reliability and build it in from the start. Looks like the Front End Test Stand?? Copy? Move?
Daresbury is the obvious place to do this as -Space availablePeople availableFriendly RDA Cockcroft, Universities, etc...
19Roger Barlow - UK ADSR programme
Stage 2: FREA
FFAG Research for the Energy Amplifier•Add a 2nd stage ring: boost energy to 390 MeV•Why 390? Pion production. But ~300 would still be interesting•Produces spallation. Not as much as 1 GeV, but enough to be interesting.•Continue to emphasise reliability. Increase current to 10 mA•Use a proton nsFFAG – with a cyclotron as fallback. Or Linac•Gives useful proton machine (c.f. TRIUMF, PSI). 99mTc production?•Links to proton therapy 20Roger Barlow - UK ADSR programme
Stage 3: Thor
Add a second ring to give 1 GeVnsFFAG, with RCS and Linac as backup optionsUse with a real target and nuclear core for productionNeed private funding
21Roger Barlow - UK ADSR programme
Conclusions
Things are movingMore peopleMore ideasPossibility of funding at some levelWay ahead for Daresbury
22Roger Barlow - UK ADSR programme