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Ra in Water using MnO2 Resin: Update

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

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Ra in Water using MnO2 Resin: Update

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  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% 106.2% 108.6% River smp 108% N/A N/A River smp spk 95% 102.7% 110.2% River smp spk 100% 103.1% 93.7% Avg = 104 % 104% 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 87.3% N/A Grndwater smp spk 88.6% 87.3% Grndwater smp 92.4% N/A Grndwater smp spk 92.7% 89.1% Tapwater smp 84.6% N/A Tapwater smp spk 91.2% 94.6% Avg.= 89.0% Avg = 93.8% ±6.9% • Ba-133= 1040 pCi, 500 mL sample, 5 pCi Ra-226 + 25 mg Ca, @ 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-133 Ra-226 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% 101.2% Avg = 94% 97.8% 100.4% 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 • 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 ~ 1.5-2 hours • Benefits • Fast, easy separation for both Ra-226, 228 • Short count for Ra-226 with large aliquot • Better alpha resolution

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