electron linacs: from the laboratory to the factory floor
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Electron linacs: From the laboratory to the factory floor. CLIC Workshop CERN David Brown, Mevex Corporation February 2014. Electron linacs – workhorses in many fields. Cross-linking/curing Medical therapy Industrial imaging/inspection Security applications Medical device sterilization - PowerPoint PPT PresentationTRANSCRIPT
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Electron linacs:
From the laboratory to the factory floor
CLIC Workshop
CERNDavid Brown, Mevex Corporation
February 2014
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Electron linacs – workhorses in many fields• Cross-linking/curing
• Medical therapy
• Industrial imaging/inspection
• Security applications
• Medical device sterilization
• Gemstone treatment
• Semi-conductor irradiation
• Mining applications (GAA/PAA)
• Medical isotope production
• Vaccine production
• Curing of composite materials at operating temperature
• Food irradiation for safety and shelf-life extension
• Quarantine/Phytosanitary treatments for fruits
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A bit of information about Mevex• Incorporated in 1987• Privately held, family company• Organic growth / Self-financing• 40 employees total: Canada, Sweden, Belgium, Thailand, France• Core Technology:
• Accelerator structures• Peak surface field strengths up to 100MV/m• Compact S-Band structures (30MV/m average – unloaded)• High power industrial linacs (15MV/m average – unloaded)
• Pulsed power and RF systems• Controls and monitoring• Radiation calculations and safety systems
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Mevex installed base summary…Applications Acc Mod Beams EnergyGemstones 2 2 1 22
Contract irradiation 1 1 1 10
Medical product research 1 1 1 5
Medical product sterilization 1 1 1 10
Medical product sterilization 1 1 1 5
Medical product sterilization 2 2 2 10
Medical product sterilization 6 3 6 5
Gemstones 2 2 1 22
Medical Therapy 6 0 6 6
Semiconductor irradiation 1 1 1 10
Contract irradiation 2 1 1 10
Contract irradiation 2 1 1 10
Medical product research 1 1 1 5
Contract irradiation 2 2 2 10
Food treatment (pathogen control and shelf life extension) 1 1 1 10
Gemstones, isotopes, semiconductors 2 2 1 20
Medical sterilization 1 0 1 10
Medical isotope production 3 3 1 35
Medical sterilization 2 2 1 10
Medical sterilization 1 1 1 10
40 28 32
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Gradients – To repair or to replace a section…. That is the question
• Conditioning effort is proportional to gradient (to the nth power).
• Conditioning effort is also related to required “missing pulse tolerance”.
• “High gradient” S-Band:
• Pulse duration 2-4 usec.
• 30MV/m takes 5 day bakeout at 400C and 2-5 days on RF test stand.
• Cannot be re-gunned/repaired in the field
• “Low gradient” S-Band:
• Pulse duration 8 – 16 usec.
• 15MV/m takes no bakeout and 24 hours RF conditioning
• Planned maintenance activities mean approximately 24 hours down.
• Catastrophic failures can be repaired but may take up to 2 weeks and may require a bakeout at 180C.
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Post-conditioning performance• Medical guides can be quickly (and fairly easily) replaced.
• Medical guides typically require low breakdown/pulse/m (less than 10-12)
• Conditioning to these gradients and breakdown rates is “easily” achievable.
• This BDR requirement applies to certain “real-time” security applications.
• Industrial guides and their scanning systems are typically “fixtures”.• Changing them is a big deal
• Industrial guides can typically tolerate higher breakdown/pulse/m
• Breakdown rates may be in the range of 10-5 BD/pulse/m immediately following a pump down.
• Conditioning happens “on-the-fly” while the machine is making money.
• BDR drops during operation for approximately 7-10 days following pump-down.
• Conditioning to these gradients and breakdown rates is “easily” achievable.
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Industrialization….• Low production rate• Easy customization by application• Must be easy to understand and repair.• Industrial safety equipment.• Industrial PLC and HMI• Distributed I/O• Modular-ized software• Connector-ized• Revision control
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Our next frontier – High energy, power, and reliability• Gemstones• Semiconductors• Medical isotope production
• Moly-99 / Tc99m• I-123• Cu-67• Etc….
• Driving sub-critical assemblies• Photo-fission• Heat• Electricity• Isotopes• Nuclear waste
This is long for us: (3 x 1.2m) 10,000 times shorter than CLIC
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Isotope production: A work in progress• The availability of high flux reactors for the production of medical isotopes caused panic
several years ago.
• Several Canadian groups received funding to do pilot-scale testing of alternatives.
• Cyclotrons were built to directly produce Tc-99m from enriched Mo-100.
• A linac facility was funded to produce Mo-99 from natural Moly and enriched Mo-100.
• NRC did early calculations, target configurations, testing, and separation experiments.
• The Canadian Light Source coordinated the funding proposal and implementation
• The pilot-scale linac was produced by Mevex and installed at the Canadian Light Source.
• 35MeV
• 1.2mA average current (average beam power 40kW)
• 3 standing wave sections, 1.2m each
• 3 klystrons
• S-Band – 2998MHz
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Isotope production: Production machine requirements• Parameters/overview:
• 35-50 MeV
• 3 – 5 mA average current (100 – 200kW average beam power)
• 3 - 5 standing wave sections, 1.4m each
• 3 -5 klystrons
• S-Band – 2998MHz
• “low gradient” 15MV/m average
• High reliability
• Performing service/maintenance activities in areas that have been activated
• Shut-downs are expensive ($1000’s per hour)
• Down-time causes scheduling/logistics problems… long time to recover.
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Tc-99m:
• 140 keV -ray, 6 hr half life
• Used for 90 % of nuclear medicine imaging
• Canada – about 5500 procedures per day
• Ottawa Hospital – about 15 cameras
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Mo-99 via U-235 fission:
• Mo-99 at peak of fission mass distribution
• ~ 6 % of fissions yield Mo-99
• Half life of 66 hrs
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An alternative route:
• Photonuclear reaction on Mo-100
• Natural Mo about 10 % Mo-100
• Available at enrichments of > 95 %
• Known for more than 40 years
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Work at Idaho National Laboratory:
• Late 1990’s
• Worked through technical, economic details
• Suggested single 15 kW accelerator for Florida
• Each target about 15 g (1 cm by 2 cm)
• Mo-100 consumption measured in µg
• “Goats” are “milked” for their Tc-99m
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Key enabling technologies:
• High-power electron accelerators
• Separator for low specific activity
• Mo-100 enrichment > 95 %
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One estimate:
• Canadian requirements (33M people): 430 six-day Ci of Mo-99 per week
• Assume reactor model: need 2500 Ci of Mo-99 per week at end-of-beam
• Need to produce 360 Ci of Mo-99 per day
• From INL study, 14 kW beam yields 25 Ci after 24 hrs
• Single 100 kW machine capable of producing about 180 Ci in 24 hours
(From US NRC study – world production)
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•For Canada, 5,500 Tc-99m procedures per day
•Each procedure requires 10 - 30 mCi; thus 110 Ci/day of Tc-99m
•Every 24 hrs, can elute ~100 % of remaining Mo-99 activity
•So need to replace 22 Ci/ day of Mo-99
•From EoB to delivery can be less than 1 t1/2 (~ 3 days)
•Conclude 44 Ci/day, EoB, should be adequate
Another estimate:
• These estimates differ by a factor of 8
• Largely because of “six-day curie”
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Mo-100 estimates:
• Enriched to > 99 %: $2,000 per gram (~$600/g for large quantities)
• Material will be recycled
• Each day, irradiate two 15 g targets to yield 180 Ci each
• Recycle time set by decay: 10 mCi can be handled with modest shielding: need 40 days
• Need (2 x 15) [g/day] x 40 [days] = 1200 g of Mo target material: 2.4 M$
• Nine cycles per year: losses per cycle expected to be small: suppose 4 %
• Then need 430 g per year to replace Mo-100 losses
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Capital Cost (k$)
Two 35 MeV, 100 kW accelerators, each 7 M$ 14000
Building, infrastructure, 3500 ft2, $1000/ft2 3500
Hot cells 3000
Mo-100 2400
Laboratory equipment 200
Total capital 23100
Facility costs – two 100 kW machines in a single location:
Assumptions:
• Both machines run 24 hours/day, 5 days a week
• Targets will be processed on site, yielding molybdate ready for the separator
• Using “six-day curie” concept, but from EoB to shipping should be less than two days
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Variable Cost (k$)
Cost of capital, 20 % 4620
Operator salaries (8 operators, 80 k$ each) 640
Supervisory, scientific salaries (head, two engineers, physicist, 120 k$ each) 480
Utilities, 2 MW, at 13 cents/kW-hr 1600
Target processing (two technicians, 80 k$ each) 160
Replacement Mo-100 (9 cycles/year, 4 % loss per cycle) 800
Accelerator maintenance and repairs (10 % of capital) 1400
Shipping (50 units per day, 260 days per year, $50 per unit) 650
Total variable 10350
Yearly output of Mo-99, 360 Ci/day, EoB, 260 days per year 94000 Ci
Yearly output of six-day curies of Mo-99 21 000 Ci
Yearly output of Tc-99m, for five milkings 62000 Ci
Separator costs from 1.5 to 5.0 ¢/mCi
Unit cost of Tc-99m ~25 ¢/mCi
Present customer cost about 100 ¢/mCi
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I-123:
• 159 keV -ray, 13 hr half life
• Several charged particle reactions can be used
• Xe-124 (p, pn) Xe-123 gives best purity
• Need 15 to 30 MeV protons; enriched Xe-124
• Typical dose costs $700, versus $20 for Tc-99m
• Can also use Xe-124 (, n) Xe-123
0.00
0.05
0.10
0.15
0.20
0.25
0.30
0.35
0.40
0 20 40 60 80
Activ
ity (C
i/g)
Irradiation time (hrs)
Xe-123
I-123
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• Oganesyan et al, Dubna, USSR, 1990
• 25 MeV, 0.3 kW
• Measured 20 mCi per hour for 10 g target
Scaling:
• 10 hr irradiation, x 10
• 100 kW beam, x 330
• In 10 g, expect 66 Ci
Pluses:• Separation very easy
• Gas is easily recycled
Minuses:• Half life of 13 hrs
• Gas easily lost
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35MeV, 100kW Linac facility requirements (Single Unit)
Description Value
Total power consumption (peak/maximum) 800kW
Total power consumption (typical operation) 650kW
Facility chilled water temperature 8C to 15C
Facility chilled water flow rate 360 liters/min
Facility chiller, heat removal capacity (recommended) 800kW
Ozone extraction fan - VFD control 3kW
Electrical conversion efficiency (AC to beam power) Approximately 15-20%
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Accelerator cluster – 4 Linacs, 35MeV, 100kW each
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Thanks and acknowledgements:• Mark de Jong, The Canadian Light Source
• Carl Ross, National Research Council, Canada
• Walter Davies, National Research Council, Canada
• Jim Harvey, Northstar Medical Radioisotopes LLC
• Chris Saunders, Prairie Isotope Production Enterprise
• Peter Brown, Mevex Corporation