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Accelerator-Produced 225Ac for Radiotherapy: Target Development Update

This research effort provides an update on the target development for accelerator-produced 225Ac for radiotherapy, including the status of target fabrication and the forward outlook. The goal is to refine the target design, develop high-current targets, evaluate thermal contact enhancement techniques, and establish alternate target fabrication capabilities.

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Accelerator-Produced 225Ac for Radiotherapy: Target Development Update

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  1. Tri-Lab Research Effort to Provide Accelerator-Produced 225Ac for Radiotherapy: Target Development Update and Forward Outlook Meiring Nortier Los Alamos National Laboratory September 19-20, 2017 Annual Program Review

  2. Outline • Technical goals • Status of the targetry development and demonstration • Continuing LANL targetry development • Routine target fabrication defense in depth • Targetry for Stage 3 and beyond

  3. Support regular production irradiations at LANL and BNL for 225Ac material evaluation and pre-clinical trials Refine detail design of Ci-scale BNL targets Develop high-current Th targets for Ci-scale production at LANL Evaluate alternate thermal contact enhancement techniques Down select and develop routine fabrication process Establish alternate target fabrication capabilities Stage 2 Targetry Technical Goals BNL LANL BNLCook&Look

  4. LANL Sigma Facility is Central • Developed the target fabrication process (now routine) • 19 LANL, 20* BNL (total for Stages 1&2) * includes 6 welded surrogate targets • Th puck preparation • Arc melting • Rolling with annealing steps • Electrical discharge machining (EDM) • Encapsulation • Machining • EB (now Laser) and TIG welding • Note: Sigma’s primary mission is to support the weapons program Arc Melter

  5. BNL Target Status • Stage 2 production targets • Design and fabrication process are locked in (0.3mm, 13g, 5 sectors, He) • Stage 3 targets (3mm, 103g, He) • Fabrication process finalized • Thermal performance verified at 160 µA (rastered) • Minor change required to Gen3 design to facilitate post irradiation puck removal • Gen4 target is fabricated and ready to be tested in 2019 (likely the final design) 2016 2017 2018 No melting observed in cook&look targets

  6. LANL Target Status • Stage 2 production targets • Design and fabrication process are locked in (1 mm, 20g, He) • Stage 3 targets • 2mm cook&look target showed melting • Enhanced thermal contact at the puck/capsule interface is under development • The contact resistance measurement apparatus is operational • Hot pressing approach is being evaluated 2016 Buckling melting Buckling and melting observed for 2mm cook&look target

  7. Rationale for Additional R&D 5 kW of beam power Thermal contact • Target heating at 100 MeV is much higher than at 200 MeV • Heat flux across the thermal contact is >6X higher • Thermal performance requirements for LANL targets are higher

  8. Exploring Thermal Contact Enhancement He-filled, TIG-welded Th target • Interstitial gas layer options • He gas (suitable for Stage 2) • Diffusion bonding • Pressure and temperature conditioning • Hot Pressing • Hot Isostatic Pressing (HIP) • Interstitial layers - In, Cu, Ni or Au • Others? (e.g. additive manufacturing) Mini HIP Hot Press Electroplated Th samples and Electroplating Bath at Sigma

  9. R&D Plan for Contact Enhancement • Develop enhancement technique • Fabricate final sample • Verify bonding by metallographic analysis • Verify contact enhancement by CR measurement • Fabricate production target • Verify quality by CR measurement • Verify performance in cook&look irradiation • Evaluate anticipated impact on chemistry • Goal is to down select viable techniques and finalize fabrication procedure by FY19 Q4

  10. Contact Resistance (CR) Measurement Apparatus is Operational Heating Measurement station • Will be used to evaluate enhancement techniques • Student Rishi Bhandiaplayed a major role in the design, fabrication and testing of the system • We have completed the measurement of benchmark samples • Will be used as a target QA tool in the long term TC’s no sample 0.05mm Th Measuring core 0.36mm Th 3mm Th Target (Vacuum) Target (He) Cooling Vacuum chamber

  11. First Technique: Hot Pressing <3600 lb force Graphite Die • Pressed in graphite die up to 3600 lb force • Induction heating with temperature control up to 800°C Vacuum chamber Graphite die Induction heating coil <800°C Inconel Hot Press Th Inconel

  12. First Hot Pressed Samples 0.002” SS304 0.155” tungsten 0.002” SS304 • Initial 1.5” DIA Inconel/Th/Inconel • Pressed for 30 min at 510°C and 850 psig (1100 psi on sample surface) • Bonded initially but then delaminated when cut for analysis • First ¾” DIA Inconel/Th sample • cracked graphite die • Second ¾” DIA sample • cracked die again • For 3rd try • Reduced pressure, increased temperature • Added tungsten inserts to spread out the force • Added SS foils to protect tungsten surfaces 0.008” Inconel 625 0.121” Thorium 0.155” tungsten 0.002” SS304

  13. ¾” Hot Pressed Sample (3rd try) Bonded sample • Single interface (Inconel/Th-0.2mm/3mm) • Pressed for 30 min at 725-790°C and 500 psig (2700 psi on sample surface) • Interface appears bonded • Th-side unexpectedly bonded to the tungsten insert (will be addressed) • Contact resistance measurement is consistent with a reasonably good bond • Metallographic analysis is in progress Inconel side Thorium side Tungsten Insert Graphite Die

  14. Looking Ahead:Routine Target Fabrication Defense in Depth • Fabrication approach for BNL and LANL Stage 2 (50-100 mCi) targets is established • Frequency of regular productions is projected to increase substantially as the project approaches Stage 3 • While manageable thus far, the burden on Sigma facilities and personnel will increase Hot Press Arc Melter

  15. Processes for Routine Target Fabrication Present Sigma processes Th melting Hot pressing EB welding Th rolling with annealing Alternatives for LANL targets to be down selected LANL Target EB Welding Hot isostatic pressing Th EDM He fill TIG welding EB welding BNL Target Machining of capsule components Outside Vendor

  16. Risks Associated with Routine Target Fabrication • Ac-225 Project brings risk to Sigma operations • Cross contamination can impact other high priority Sigma Programs (2017 contamination event shut down arc melter operations) • Unexpected un-availability of critical target fabrication facilities shared with high priority programs • E.g., Hot Press, HIP, EB welding, TIG welding • May 10th NNSA announcement: LANL to increase pit production – expected to impact Sigma availability

  17. Stage 2 Goal Towards Risk Reduction • Limit Sigma operations to high temperature Th processes only • Establish other capabilities external to Sigma • LANL: Laser welding capability • LANL: Down selected thermal contact enhancement capability (e.g. hot press) • BNL Welding capabilities (institutional and outside vendor) • ORNL: Backup Th processing under consideration • Use outside vendors where possible • Budget allows for establishing laser welding and hot pressing capabilities at LANL

  18. Stage 3 Out Year Low Risk Fabrication External Vendors Sigma LANL (External to Sigma) Th melting Hot Pressing Laser Welding • Additional goal: Procure a dedicated Sigma-based melting apparatus (present arc melter is shared with high priority programs). Machining of capsule components Th rolling with annealing LANL Target Hot isostatic Pressing Laser Welding Th EDM BNL Laser Welding under He ORNL BNL Target Machining of capsule components Th processing capabilities

  19. Case for Transitioning to Laser Welding Th target capsule welds • Sigma recommends laser welding for routine fabrication • Weld quality is as good as EB • Laser is capable of welding • In vacuum • Under cover gas such as helium (important for BNL targets) • Added benefit to Isotope Program • Compatible with in-hot-cell-welding essential for future recycling of enriched target material • First laser welded LANL target successfully irradiated in August (3 days @ 250 µA) EB weld Laser weld Inside hot cell Outside hot cell Laser Welding chamber

  20. Proceed with Procurement of Laser Welder in Stage 2 • Two very different quotes for similar systems • Focus (~$275k) • PTR-Precision Technologies (~$800k) • Awaiting a third quote • Goal • Initiate procurement in Q2 of FY19 (Stage 2 milestone) • Commission by June 2020

  21. Looking Ahead: Stage 2 Productions in the Near Term (50-100 mCi) BNL 2nd Gen 13 g target • BNL • 2nd Gen 0.3 mm (13 g) target is considered adequate for Stage 2 • Expected EOB yield is 260 mCiof Ac-225 at 165 uA for 10 days • LANL • 1st Gen 1 mm (20 g) target with He filling is considered adequate for Stage 2 • Targets tested (3X) during 2017/8 run cycles • Expected EOB yield for a 3-day irradiationat 250 µA is 136 mCi (363 mCi for 10 days) LANL 1st Gen 20 g target

  22. Advances and Opportunities for Stage 3 Targets:Higher Currents and Multi Targets at BNL • NP funded Accelerator Improvement Project (AIP) included a new 2-circle raster system • BLIP increased beam-on target current from 115 µA to 165 µA • Further increase to 250 µA envisaged by 2021 BLIP beam power density before raster project (left) and after(right) drops 5 fold

  23. Advances and Opportunities for Stage 3 Targets:Multi Targets at BNL Th Ga RbCl • High energy beam presents the opportunity to irradiate multiple Th targets in the energy range 120-200 MeV. • Will have minimal impact on production in energy range <100 MeV (e.g.Sr-82) • Can irradiate up to 4 Th targets per production with projected EOB yields of~ 1.6 - 2.2 Ci per target at 165 µA <100 MeV 120-200 MeV Example BNL target stack with 4 Th targets

  24. Advances and Opportunities for Stage 3 Targets:Ultra-high Beam Currents at LANL • The recently completed AIP project allows • Beam currents up to 450 µA and beyond • Advanced raster patterns with up to 100 circles • Larger targets up to 2.5” in DIA

  25. Looking Ahead to Ci-level Targets:Ultra-high Beam Currents at LANL • Models predict that thorium targets will withstand 450 µA, assuming • larger 2.5” Th-targets • 5-circle raster pattern • close-to-ideal thermal contact • Translates into Ac-225 production yields of up to 2.5 Ci for a 10 day irradiation • Stretch goal is to fabricate and irradiate a 2.5” target prior to Stage 3 start. 2.5” target, 450 µA 5-circle raster pattern

  26. Summary • Unique target fabrication techniques for Thorium targets have been established. • BNL Stage 2&3 targets are ready • Continue to pursue enhanced thermal contact for LANL Stage 3 targets • Additional focus on routine target fabrication defense in depth • Multi-target stacks at BNL and ultra-high beam currents at LANL offer a substantial increase in production capacity • Present annual worldwide supply can easily be exceeded in 10 days of operation at either one of our high energy accelerators in Stage 3 and beyond

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