Electron linacs:

From the laboratory to the factory floor

CLIC Workshop

CERNDavid Brown, Mevex Corporation

February 2014

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

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

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  

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.

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.

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

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

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

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.

(CNS Workshop Dec-09) 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

•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”

(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

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

(CNS Workshop Dec-09) 20

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

(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

0.00

0.05

0.10

0.15

0.20

0.25

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0.35

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0 20 40 60 80

Activ

ity (C

i/g)

Irradiation time (hrs)

Xe-123

I-123

(CNS Workshop Dec-09) 22

• 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

(CNS Workshop Dec-09) 23

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%

(CNS Workshop Dec-09) 24

Accelerator cluster – 4 Linacs, 35MeV, 100kW each

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