1. MnO 2 Resin and Automated Measurements of Ra Isotopes Bill Burnett Dept. Oceanography Florida State University

2. MnO 2 Resin Developed by PGRF 80-160 mesh High adsorption of Ra, trivalent and tetravalent actinides (Ac, Am, Pu, Th) Preconcentration approach in batch, column, or pump (filtration) modes

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. Tracers for Characterization Ba-133 (commercial, nominal activity) Ra-228, Ra-224 (separated from 40-year old Th(SO 4 ) 2, calibrated by gamma spect Ra-226 NIST solution standard

5. Distribution Coefficient C 1 = amount adsorbed per gram dry resin; and C 2 = amount that remains in solution after equilbrium has been reached. Units = mL/g

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

7. Percent Recovery K D = 2.8 x 10 4

8. Kinetics, pH = 7 pH = 7 Resin = 25 mg Solution = 10 mL Floridan Aquifer groundwater ~40-200 mg/L (0.04-0.2 o / oo )

9. pH Variation pH = variable Resin = 25 mg Solution = 10 mL Reaction time = 90 min Surface charge Ra 2+ speciation The optimum pH for adsorption of Ra 2+ is from 5 to 8 – nearly all natural waters fall into this range.

10. Pump Tests Peristaltic pump; cartridge loaded with 1 g MnO 2 Resin; single pass

11. Pump Video Fresh waters can be processed at high flow rates (  300 mL/min) without any loss. Highly salted waters require longer equilibration times

12. Ra Isotopes via RAD-7 MnO 2 -Resin ( 226,228,224,223 Ra) Alpha Detector --- 222 Rn 220 Rn 219 Rn 222 Rn, 220 Rn, 219 Rn 215 Po 216 Po 214 Po 218 Po Drierite Air Pump RAD7

13. Optimum Moisture Content Water/Fiber Ratio = (x i -x o )/x o ; where x i = mass at each stage; and x o = mass when completely dry

14. Recoil Effect on Rn Emanation Recoil range in air = 0.07 cm Recoil Range in water = 9.1 x 10 -5 cm

15. “DRYSTIK” Approach Drierite

16. Moisture Control During Counting

17. Effect on Countrate

18. 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.

19. Results: Ra-226 ( 222 Rn Ingrowth) T 1/2 = 3.84 days Several standards prepared with NIST 226 Ra solution. Theoretical line drawn with decay constant for 222 Rn.

20. 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