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Measurements of Ra Isotopes via MnO 2 Resin Bill Burnett, Natasha Dimova Florida State University E. Philip Horwitz PG Research Foundation.

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Presentation on theme: "Measurements of Ra Isotopes via MnO 2 Resin Bill Burnett, Natasha Dimova Florida State University E. Philip Horwitz PG Research Foundation."— Presentation transcript:

1 Measurements of Ra Isotopes via MnO 2 Resin Bill Burnett, Natasha Dimova Florida State University E. Philip Horwitz PG Research Foundation

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

3 IsotopeDirectParentHalf-life Decay Mode EnergyMeV 223 Ra 227 Th 11.4 d 5.615.72 224 Ra 228 Th 3.66 d 5.69 226 Ra 230 Th 1600 y 4.78 228 Ra 232 Th 5.75 y 0.046 Natural Radium Isotopes

4 MnO 2 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 Ra 2+ is from 4 to 8 – nearly all natural waters fall into this range. Moon et al. / Applied Radiation & Isotopes 59 (2003) 255-262

6 K D Determination A o = initial activity solution, cpm A f = final activity solution, cpm V = volume solution, mL W = weight of resin, g

7 K D 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 K D = 2.8 x 10 4 mL/g

9 Possible Analytical Uses 1.Drinking water analysis of Ra-226 and Ra-228 via preconcentration and  - spectrometry (well detector best) 2.Preconcentration of Ra isotopes and analysis of  -emitters via  -spect 3.Automated analysis of  -emitting Ra isotopes via a radon-in-air analyzer

10 Gamma-Spect Analysis React MnO 2 Resin in a batch mode, let settle, decant/ centrifuge, transfer to counting vial for  -spect analysis

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

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 BaSO 4 micro ppt 226 Ra 222 Rn 218 Po 214 Po

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

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

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

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 MnO 2 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 1.Load sample on resin, measure Ra-224, close stopcocks, allow ~5 days ingrowth for Ra-226 2.Attach to RAD-7 manifold, purge RAD-7, pump air through cartridge/RAD-7 for 5 minutes, close valves 3.Count for a few 15-min cycles for quick analysis (Po-218) or several hours for more sensitive analysis (Po-218 + Po-214) 4.Calculate results

23 Results: Ra-224 Counting Water sample passed through MnO 2 Resin and 220 Rn counted periodically over many days produced the correct half-life for 224 Ra.

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

25 226 Ra MDAs: Auto Counting 1 liter2 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  MnO 2 Resin is an excellent adsorber of Ra from natural waters  May be used for preconcentration to combine with traditional techniques (e.g.,  -spect,  -spect)  Interfacing with a RAD-7 Radon analyzer allows determination of 224 Ra and 226 Ra without chemical separations


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