1. Measurements of Ra Isotopes via MnO2 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. Natural Radium Isotopes
Direct
Parent
Half-life
Decay Mode
Energy
MeV
223Ra
227Th
11.4 d a
5.61
5.72
224Ra
228Th
3.66 d
5.69
226Ra
230Th
1600 y
4.78
228Ra
232Th
5.75 y b
0.046

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)

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 ~ mg/L ( o/oo)
Moon et al. / Applied Radiation & Isotopes 59 (2003)

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 226Ra peak 186 keV no U via 214Pb + 214Bi
352
226Ra peak 186 keV no U
via 214Pb + 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
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. Natural Ra isotopes and Ra-225 tracer
a-Spectrometry
Natural Ra isotopes and Ra-225 tracer
Ra daughters
S. Purkl, A. Eisenhauer / Applied Radiation and Isotopes 59 (2003) 245–254

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

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 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