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Electron linacs: From the laboratory to the factory floor

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

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Electron linacs: From the laboratory to the factory floor

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  1. Electron linacs:From the laboratory to the factory floor CLIC Workshop CERN David Brown, Mevex Corporation February 2014

  2. 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

  3. 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

  4. Mevex installed base summary…

  5. 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.

  6. 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 10-5BD/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.

  7. 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

  8. 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

  9. 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

  10. 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.

  11. 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 (CNS Workshop Dec-09)

  12. 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 (CNS Workshop Dec-09)

  13. 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 (CNS Workshop Dec-09)

  14. 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 (CNS Workshop Dec-09)

  15. Key enabling technologies: • High-power electron accelerators • Separator for low specific activity • Mo-100 enrichment > 95 % (CNS Workshop Dec-09)

  16. 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) (CNS Workshop Dec-09)

  17. Another estimate: • These estimates differ by a factor of 8 • Largely because of “six-day curie” (CNS Workshop Dec-09)

  18. 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 (CNS Workshop Dec-09)

  19. 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 (CNS Workshop Dec-09)

  20. Present customer cost about 100 ¢/mCi (CNS Workshop Dec-09)

  21. 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 (CNS Workshop Dec-09)

  22. Oganesyanet 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 (CNS Workshop Dec-09)

  23. 35MeV, 100kW Linac facility requirements (Single Unit) (CNS Workshop Dec-09) 23

  24. Accelerator cluster – 4 Linacs, 35MeV, 100kW each (CNS Workshop Dec-09) 24

  25. 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

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