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Actinide Analysis from Large-Volume Seawater Samples

Actinide Analysis from Large-Volume Seawater Samples. Bill Burnett & Guebuem Kim Department of Oceanography Florida State University and Phil Horwitz PG Research Foundation. Acknowledgments. Pavel Povinic, Jerry LaRosa IAEA Marine Environment Laboratory, Monaco PG Research Foundation.

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Actinide Analysis from Large-Volume Seawater Samples

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  1. Actinide Analysis from Large-Volume Seawater Samples Bill Burnett & Guebuem Kim Department of Oceanography Florida State University and Phil Horwitz PG Research Foundation

  2. Acknowledgments Pavel Povinic, Jerry LaRosa IAEA Marine Environment Laboratory, Monaco PG Research Foundation

  3. Marine Environment LaboratoryMonaco

  4. Need for Large Volumes • Activities of fallout Pu in the open sea very low — on order of 0.01 mBq/kg! • To obtain good precision with reasonable count times (~1 week) requires volumes on the order of 100-400 liters! • How can we preconcentrate/separate actinides efficiently from such a large volume?

  5. MnO2 Co-precipitation • Seawater, 100-400 liters • Acidify to pH 2, add Pu/Am tracers, stir/hold • For 100L sample, add 35 mL sat KMnO4 (~2.1g); Pu-->Pu(VI), org oxid, purple color • Adjust pH to 8-9 with NaOH • Add 0.5M MnCl2 (2x vol of KMnO4); --> MnO2 ppt, dark brown Seawater MnO2 Suspension 2MnO4- + 3Mn2+ + 2H2O = 5MnO2 + 4H+ • Re-adjust pH to 8-9 as necessary • Stir occasionally to keep MnO2 suspended for few hours • Allow Mn02(Pu, Am) ppt to settle overnight • Pump supernatant into clean tank for Cs, Sr processing • Drain MnO2 slurry from bottom tap centrifuge/ filter MnO2 ppt (Pu, Am) ~4400 mg! supernatant Cs, Sr

  6. Transferring Water and MnO2 Supernatant seawater transferred from one plastic tank to another via pumping — this will be used for 90Sr and 137Cs. MnO2 suspension withdrawn from bottom of conical-shaped plastic tanks — processed for Am and Pu.

  7. Fe(OH)3ppt MnO2 ppt (Pu, Am) • Dissolve MnO2 w (~2L) 2M HCl + (~20-40 mL) NH2OH.HCl (0.1g/mL) • Add 50 mg Fe3+ as FeCl3 --> yellow • Add (~1.5L) 2M NaOH to decrease acid conc. • Add ~2mL NH2OH.HCl to reduce Fe3+ --> Fe2+ Pu*-->Pu3+; colorless soln • Add 20 mL NaNO2 (0.1g/mL); Fe2+ --> Fe3+; Pu3+ --> Pu4+ • Add 2M NH4OH to pH = 8-9; ppt Fe(OH)3 • Boil ~5 min to improve coagulation of Fe(OH)3 ppt • Adjust pH to 6-7 w 1M HCl to hold Mn in soln • Let cool, settle, centifuge Fe(OH)3 suspension, filter supernatant, dissolve ppt in acid for separation Mn2+ soln (Pu, Am) Mn2+, Fe2+ soln (Pu3+, Am3+) Fe(OH)3 ppt (Pu, Am) Chemical separations

  8. Collection of Fe(OH)3 ppt Fe(OH)3 is ppt and allowed to settle in 10-liter glass beakers Supernatant from Fe(OH)3 suspension filtered through a 0.45 mm filter

  9. 2-Column Separation: Part 1 1 2 U/TEVA • U, Th, Np Resin® 2 1 TRU Am, Pu • Resin® 1 2 [Discard or to Sr•Resin]

  10. 3 2 4 2 1 3 1 2.5M HNO3 1 9M HCl 1 2.5M HNO3 - 0.1M NaNO2 U/TEVA 2.5M HNO3 TRU 5N HCl - 0.05 H2C2O4 • 2 9M HCl • 2 Resin® 0.01M HCl 3 4M HCl 3 Resin® 0.1M NH4HC2O4 or 4M HCL + 0.1M H2Q 4 1 2 1 2 4 Pu Np, Th Discard 3 3 U Am Actinide Separation: Part 2

  11. Results: Irish Sea Water *IAEA Intercomparison (Povinic, pers. comm.)

  12. Am Spectrum

  13. Pu Spectrum

  14. Summary & Future Plans • MnO2/Fe(OH)3 ppt effectively concentrates actinides from large volumes. • UTEVA/TRU effectively and easily separates Pu/Am from Fe(OH)3 matrix. • Investigate use of Diphonix for actinide preconcentration from large volumes.

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