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Ac-225 Chemistry development

Review of the chemistry development of Ac-225 production using high-energy protons, challenges in scale-up, chemical separations, and optimization for routine production. Includes studies on Thorium dissolution, chelating agents, and solvent extraction methods. Significant focus on Lanthanides separation.

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Ac-225 Chemistry development

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  1. Ac-225 Chemistry development Jonathan Fitzsimmons Science and Technology review March 28-29, 2017

  2. Accelerator Produced Ac-225 by high energy protons 232Th(p,x)225Ac • Ratio of total fission product to Ac-225 radioactivity is ~20:1 at EOB • Estimated 400 isotopes produced at the end of bombardment > 1 µCi • Ac-225 and Lanthanides (La-140, Ce-141) have similar chemistry • Routine production 50-100 g Th targets • Max production multiple 100 g Thtargets • Challenging chemical separation and scale up • La used as surrogate for Ac-225

  3. Phase 1: Initial Chemistry Dissolve Th target 1) MP1 (Cl) Column 3) MP1 (NO3) Column 2) MP1 (NO3) Column Elute Ac, Th, Ag, La,Ce Elute Ac, Ag, La, Ce Trace Th • Allowed evaluation of accelerator produced Ac-225 • Separation works for 1-10 gram Th targets • Takes 5+ days for processing Clean up column Retain Th retain Bulk Th retain Pa, U, Fe, Mo… Eluted Ac 5) LN (Cl) Column 4) AG50 (NO3) column Separation: Developed by ORNL team based on: Applied Radiation and Isotopes 2005, 667-679 Elute Ac, Ln, Ag Retain Ln (La, Ce) Retain Ag

  4. Phase 2: Chemistry scale up & optimization for routine production Dissolve Th target 1) MP1 (Cl) Column 3) MP1 (NO3) Column 2) MP1 (NO3) Column TriLab effort: • Retention of Th on resin at 50-100 gram scales difficult • BNL GOAL: Examine separations where Ac is retained and Th is eluted • Replace MP1 column with chelating agent and cation resin1 retain Bulk Th Eluted Ac 5) LN (Cl) Column 4) AG50 (NO3) column Elute Ac, Ln, Ag Retain Ln (La Ce) Ac losses at Ln column ~30% (LANL) 1. J. Chinese Chem Soc. 1959, 6, 1, p. 55-67.

  5. Cation Step Development Studies performed by interns: Bryna Torre, Bryan Foley • Initially evaluated with La and 19 other elements • each step graphed all elements (>8,000 data points) Elution procedure: Load, 1 M Citric acid pH 2, 3 BV 2 M HCl, 3 BV 3 M HCl, 3 BV 2.5 M HNO3 Elute: 20 BV 6 M HNO3 Rinse steps elutes 85-100% of each of the 19 metals with < 5% elution of La

  6. Ac-225/Th studies J. Chinese Chem Soc. 1959, 6, 1, p. 55-67. Aqueous Speciation of the Actinides with Organic Ligands Relevant to Nuclear Waste Thesis. Jennifer Dawn Rochford. 2014 University of Manchester

  7. Phase 2: Chemistry scale up & optimization for routine production Dissolve Th target 1) MP1 (Cl) Column 2) AG50 Column Eluted all Th and some other metals Implemented at ORNL ~90 % recovery of Ac-225 No Th present after AG50 column Issues with Ba-140 and radioactive Ra Elute Ac, Th, Ag, La Ce retain Ac, Ln (La, Ce…) retain Pa, U, Fe, Mo… • Experiment 11/16-11/20, 2015 with 10 gram Th target 3) B DGA Column Eluted Ac Retain Ln (La, Ce…)

  8. Cation Step Development: Ba/Ra • Ba chemically similar to Ra  Ba can be eluted with 2.5 M nitric acid • Examined rinse quantities of 2.5 M nitric acid to elute Ba • Evaluated with 55+ elements La, Th, Lanthanides other metals • Each element graphed • ORNL implemented cation rinse step: 5 BV 2.5 M HNO3 • No losses of Ac-225 during the cation step 6 BV of 2.5 M nitric acid eluted 92% of Ba

  9. Feasibility of 50 g Target chemical processing • Question: Does the current method work on a production scale target mass? • Experiment: simulate a 50 gram Thorium target chemical process • Irradiate thorium foil 30 min • Dissolve and add to 50 grams of dissolved Thorium • Dissolution of Th in Concentrated HCl: • Brown precipitate could not be removed by filtration • Required 1,000 mL of Conc. HCl • MP1 Column ~ 4:15 hours • Evaporation of 1 L of Conc. HCl • will likely take 1 day in hot cell • Dissolution of Th in 3 M citric acid pH 2 • (1500 mls) • Likely take 3-6 hours Solid Thorium Citrate

  10. ThDebulking method: PolyoxometalatesStudies performed by: VFP: Lynn Francesconi, Graduate student: Jasmine Hatcher, Intern: Huseyin Cicek, Ali Younes • Aqueous: • 5M HNO3, 0.2M KOAc, 3mM POM • Organic: • 3% octylamine/CHCl3 Results • POM has a high affinity: Ac (98.8%) or Th (100%) individually • High selectivity for Th (100%) over Ac (0%) and La (4%) Jasmine Hatcher Poster has detailed information

  11. ThDebulking method: solvent extraction • 6 M nitric acid / TBP / Toluene • ~20% TBP in toluene • 1-3 M nitric acid / 3 M calcium nitrate / 20% TBP in toluene • Higher concentrations of nitrate salts lead to higher ratios of Th in organic layer • Th can be back extracted from TBP/toluene into water or very dilute acid • The radiochemistry of Thorium, Hyde January 1960

  12. Future Studies with Solvent ContactorJournal of membrane Science 300 (2007) 131-136. looked at TBP and UO2 Liquid Membrane (toluene) • Overtime Thwould be dissolved, extracted with TBP, then back extracted into water • Automation of dissolution and extraction of bulk Th • Might be able to dilute target solution for cation column Ac-225 retained in less than 2 m nitrate Eliminating timely evaporation step Th Nitrate Th-Nitrate Ac, Nitrate, Na TBP Th Ac Ac Th –nitrate –TBP Th Water or dilute acid Ac, Nitrate, Na Back extract with water very dilute acid Partially Dissolve Th target

  13. Quality Control of final product Actinium-225 HPGE Th target library: prepared with 40+ isotopes specified by ORNL (prepared by intern: Joel Strandburg) ICP-OES analysis method for Ac-225 production • Method: pink and purple elements with Sc as internal standard • 5 point calibration curve from 0.05 – 1 ppm • Quantification limits determined • Elemental analysis specification for Ac-225: < 25 ppm for hot purple elements

  14. Ac-225 Chemistry Contributions at BNL • Visiting scientist and interns • VFP • Lynn Francesconi • Interns • Bryna Torre (Core) • Bryan Foley (Core) • Megan Wilken (Core/FOA) • Huseyin Cicek (VFP) • Jasmine Hatcher (VFP- graduate student) • Alyson Abraham (FOA) • David Hill (FOA) • Shane Stone (FOA) • Jacqueline Noel (FOA) • Joel Strandburg (Core/FOA) • Ali Younes (Post Doc/FOA) • Christopher Caroff (NCSS/FOA) • BNL Staff • Jonathan Fitzsimmons • Leonard Mausner • Dmitri Medvedev • Cathy Cutler

  15. Chemistry & Stages of Development Phase 1- Develop purification of Ac-225 (1-2 gram targets) • Allow evaluation of accelerator produced Ac-225 comparison to Ac-225 produced by Th-229 generator (2014-2016) Phase 2- Optimize chemistry for routine production 10100 gram target Phase 3 – Optimize chemistry for routine or max production multiple 100 gram targets Dependent on demand

  16. Cation Step Development Studies performed by Bryna Torre, Bryan Foley * * • 2 & 3 M HCl followed by 2.5 M HNO3

  17. Polymer used for resin speciation study: ATR-FT-IR Polymer  A) La + 1 M Acid pH 2  B) polymer placed in 0.3 M HCl (pH2)  4 M HCl Polymer  C) 1 M Acid pH 2 La Tartaric acid La Citric Acid Sulfonic acid polymer A) La, M Acid pH 2 B) Polymer in A rinsed with pH 2 HCl acid C) acid pH 2 no metal La removed with 4M HCl, ICP-OES

  18. Core: Solid Supports Studies Ac-225 polymers: Rh studies C • Polymer  A) Rh + 1 M Citric acid pH 2  B) polymer placed in 0.3 M HCl (pH 2), C) 4 M HCl, D) 4 M HCl 24 hrs, E) 8 M HCl hot 30 min, F) 8 M HCl 24 hrs, G) 50% ethanol A D E B F G • Rh species kinetically inert on both the resin and the polymer

  19. Evaluating 2.5 M Nitric rinse step

  20. 50+ metal study on AG50X8 - 1 M Citric acid pH 2 • Sequence: loaded on AG50 column, rinsed with 3 BV of 1 M Citric acid, • 3 BV of 2 M HCl, 3 BV of 3 M HCl, • 3 BV of 2.5 M HNO3, 3 BV of 2.5 M HNO3, • Elution: 10 BV of 6 M NO3, 10 BV of 6 M HNO3 *

  21. 50+ metal study on AG50X8 - 1 M Citric acid pH 2 Lanthanides • Sequence: loaded on AG50 column, rinsed with 3 BV of 1 M Citric acid • 3 BV of 2 M HCl, 3 BV of 3 M HCl, • 3 BV of 2.5 M HNO3, 3 BV of 2.5 M HNO3 • Elution: 10 BV of 6 M NO3, 10 BV of 6 M HNO3

  22. Ac-225/Th Safety • Multiple documents submitted/reviewed by Experimental Safety Review committee • ESR approved and 13 appendixes added for different experiments and to prevent alpha contamination in the lab • Workers review and sign • Radiation work permit issued • Continuous Air monitoring during all Ac-225/Th studies • All Ac-225 studies are performed in a glove box • Up to May 2016 a spill of Ac-225 or Th would result in a stop work and notification to department chair and head of safety Charcoal Filter HEPA Filter Transfer chamber

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