1. Ra in Water using MnO2 Resin: Update
Sherrod L. Maxwell, III
Westinghouse Savannah River Company

2. Need for Improved Method for Ra-226, 228 in Groundwater Samples
Cation Resin experience
slow flow-1 to 2 days load time
potential calcium interference
1 pCi/L MDA required
need large sample aliquot (1L) for Ra-228 via Ac-228 (gas proportional counting)
Test MnO2 Resin developed by PGRF (Horwitz et al) and W. Burnett et al (FSU)

3. Ra-226 and Ra-228 in Water 1.25 g MnO2 Resin (Eichrom)
1 liter samples + Ba-133 tracer
pH adjustment to 6-7 / add 25 mg Ca
Flow rate ~15 mL/min
Vacuum box loading with inner liner
~ 1-2 hour loading
speed & ability to deal with slow samples
Strip MnO2 with 12 mL 4M HCL-1.5% H2O2
Wait 36 hours if analyzing Ra-228

4. Ac-228 on DGA Resin Ln Resin (2 mL) + DGA-Normal (2mL) stacked
Ln resin (U,Th removal) and DGA (Ac-228 retention)
loaded 12 mL strip solution from MnO2 resin on LN-DGA
collect load + 5 mL 4M HCL rinse for Ra-226
10 mL 4M HCL rinse-discard
Save LN Resin
Strip Ac-228 from DGA with 10 mL 0.5M HCl
100 uL Ce and 1 mL con. HF

5. Improvements Use Ln -DGA Resin instead of TRU-DGA
better alpha resolution and consistency
even with large groundwater sample size
combines Ra-226 and Ra-228 sample preparation
Ac-228 on DGA (Ln Resin removes Th,U)
Ra-226 after repass through Ln-Resin at low acid

6. Slide- E. P. Horwitz, May, 2004 User’s Meeting

7. Slide- E. P. Horwitz, May, 2004 User’s Meeting

8. Ra-226 in Water Evaporate load + rinse solutions from Ln-DGA
Redissolve in 0.1M HCl
Pass solution through same Ln cartridges to better remove alpha resolution interferences
Precipitate Ra-226 (Ra-224) using Ba sulfate
100 uL of 0.70 mg/mL Ba + 5 mL 30% sodium sulfate place on ice
0.1 mL seeding suspension
Count Ra-226 (Ra-224) by alpha spectrometry
Count filter by gamma for Ba-133 tracer recovery

9. Column Loading

10. Column Stripping Strip with 4M HCL-0.15% H2O2
Wait 36 hours and load to Ln/DGA

11. Ln/DGA Resin Separation

12. Ra-226/228 Recoveries % Recovery % Recovery % Recovery
Ba-133 Ra-226 Ra-228
LCS (spiked DI H2O) 60% % %
River smp 108% N/A N/A
River smp spk 95% % %
River smp spk 100% % 93.7% Avg = % %
1.5 L samples
Ba-133=1040 pCi
Ra-226 spk= 5 pCi
Ra-228 spk= 20 pCi

13. Spiked river water sample-1500 mL
Ra-226 and Ra-228 daughters

14. Ra-226 in Groundwater % Recovery % Recovery Ba-133 Ra-226
Blank (DI H2O) 86.3% N/A
LCS (spiked DI H2O) 88.6% 104%
Grndwater smp % N/A
Grndwater smp spk 88.6% %
Grndwater smp % N/A
Grndwater smp spk 92.7% %
Tapwater smp % N/A
Tapwater smp spk 91.2% %
Avg.= 89.0% Avg = 93.8% ±6.9%
Ba-133= 1040 pCi, 500 mL sample, 5 pCi Ra mg 15 mL/ min.

15. Spiked Groundwater sample-500 mL
Passed through TRU-DGA at 4M HCL
evaporate and precipitate

16. Better alpha resolution with repass through Ln-Resin after lowering acid to 0.1M HCL
Spiked LCS-1 liter

17. Spiked Groundwater sample-1 liter
FWHM=81.6

18. Ra-226 and Ra-228 in Groundwater
% Recovery % Recovery % Recovery Ba Ra Ra-228
BLK 90% N/A N/A
LCS (spiked DI H2O) 95% 99.2% 99.7%
GRNDWATER smp 100% N/A N/A
GRNDWATER smp 89% N/A N/A
GRNDWATER smp 97% N/A N/A
GRNDWATER SPK 95% 96.5% %
Avg = 94% % %
1 L samples
Ba-133=1040 pCi; Ra-226 spk= 5 pCi: Ra-228 spk= 20 pCi
waited 36 hr/used Ln-DGA

19. Summary Ra-226 and Ra 228 using MnO2 resin Vacuum Box method Benefits
Ln/DGA Resin -Ra-228 via Ac-228
Ra-226 using barium sulfate micro-precipitation
Speed and selectivity
Vacuum Box method
1L loaded and stripped ~ hours
Benefits
Fast, easy separation for both Ra-226, 228
Short count for Ra-226 with large aliquot
Better alpha resolution