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Measurements of Ra Isotopes via MnO 2 Resin

Measurements of Ra Isotopes via MnO 2 Resin. Bill Burnett, Natasha Dimova Florida State University E. Philip Horwitz PG Research Foundation. FSU Graduate Students : Natasha Dimova Henrieta Dulaiova Ricky Peterson Benjamin Mwashote Christina Stringer. PGRF : Phil Horwitz Andy Bond

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Measurements of Ra Isotopes via MnO 2 Resin

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  1. Measurements of Ra Isotopes via MnO2 Resin Bill Burnett, Natasha Dimova Florida State University E. Philip Horwitz PG Research Foundation

  2. FSU Graduate Students: • Natasha Dimova • Henrieta Dulaiova • Ricky Peterson • Benjamin Mwashote • Christina Stringer • PGRF: • Phil Horwitz • Andy Bond • Dan McAlster Acknowledgments

  3. Natural Radium Isotopes

  4. MnO2 Resin • Developed by PGRF • High adsorption of Ra, trivalent and tetravalent actinides (Ac, Am, Pu, Th) • Preconcentration approach in batch, column, or pump (filtration) modes

  5. Adsorption vs. pH • pH = variable • Resin = 25 mg • Solution = 10 mL • Reaction time = 90 min The optimum pH for adsorption of Ra2+ is from 4 to 8 – nearly all natural waters fall into this range. Moon et al. / Applied Radiation & Isotopes 59 (2003) 255-262

  6. KD Determination Ao = initial activity solution, cpm Af = final activity solution, cpm V = volume solution, mL W = weight of resin, g

  7. KD and Kinetics, pH = 7 Floridan Aquifer groundwater ~40-200 mg/L (0.04-0.2 o/oo) Moon et al. / Applied Radiation & Isotopes 59 (2003) 255-262

  8. Percent Recovery KD = 2.8 x 104 mL/g

  9. Possible Analytical Uses Drinking water analysis of Ra-226 and Ra-228 via preconcentration and g-spectrometry (well detector best) Preconcentration of Ra isotopes and analysis of a-emitters via a-spect Automated analysis of a-emitting Ra isotopes via a radon-in-air analyzer

  10. Gamma-Spect Analysis React MnO2 Resin in a batch mode, let settle, decant/ centrifuge, transfer to counting vial for g-spect analysis

  11. Gamma Spectrum 214Pb 352 226Ra peak 186 keV no U via214Pb + 214Bi 228Ra via 228Ac 214Pb 295 214Bi 609 226Ra 186 228Ac 911 228Ac 338

  12. MDA Gamma Spect • ~100-cc Ge well detector • 2-liter volume • 295+352+609 keV assumes 50% equilibrium (4-day ingrowth)

  13. Alpha Spectrometric Analysis Nour et al., in press

  14. Ra-226 via BaSO4 micro ppt 226Ra 222Rn 218Po 214Po

  15. a-Spectrometry Natural Ra isotopes and Ra-225 tracer Ra-224 + daughters S. Purkl, A. Eisenhauer / Applied Radiation and Isotopes 59 (2003) 245–254

  16. moisture B A x x x x x = stopcock C Automated Measurements drying tube filter sample in out (pump) “DRYSTIK” inner drying tube outer RAD-7

  17. Gas Handling System Front Back All the necessary tubing, valves, and drying system fits easily into a small cabinet

  18. Loading the Sample Fresh water samples can be processed either by gravity flow or by pumping at rates up to 300 mL/min without any loss of Ra.

  19. Connecting Sample to RAD-7 The sample, inside the same cartridge used for processing the sample, is hooked up to a radon-in-air analyzer.

  20. Validating Standard Ra Activity Our standards are made by passing NIST-traceable Ra-226 solution standards through the MnO2 Resin. Any Ra remaining is measured by Rn emanation. Results confirm retention >96%.

  21. Setting Standard Ingrowth The standards are re-set for ingrowth by passing helium through the cartridge to ensure no Rn-222 is present at t=0. A small amount of water is then added to enhance Rn emanation.

  22. Suggested Protocol • Load sample on resin, measure Ra-224, close stopcocks, allow ~5 days ingrowth for Ra-226 • Attach to RAD-7 manifold, purge RAD-7, pump air through cartridge/RAD-7 for 5 minutes, close valves • Count for a few 15-min cycles for quick analysis (Po-218) or several hours for more sensitive analysis (Po-218 + Po-214) • Calculate results

  23. Results: Ra-224 Counting Water sample passed through MnO2 Resin and 220Rn counted periodically over many days produced the correct half-life for 224Ra.

  24. Results: Ra-226 (222Rn Ingrowth) Several standards prepared with NIST 226Ra solution. Theoretical line drawn with decay constant for 222Rn.

  25. 226Ra MDAs: Auto Counting 1 liter 2 liters MDAs calculated assuming 96% yield, typical blanks for A and C channels, and an equilibrium fraction of 0.5 (4 days ingrowth)

  26. Summary • MnO2 Resin is an excellent adsorber of Ra from natural waters • May be used for preconcentration to combine with traditional techniques (e.g., a-spect, g-spect) • Interfacing with a RAD-7 Radon analyzer allows determination of 224Ra and 226Ra without chemical separations

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