Ra in Water using MnO2 Resin: Update

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Ra in Water using MnO2 Resin Update

• Sherrod L. Maxwell, III
• Westinghouse Savannah River Company

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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)

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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

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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

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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

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Slide- E. P. Horwitz, May, 2004 Users Meeting
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Slide- E. P. Horwitz, May, 2004 Users Meeting
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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

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Column Loading
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Column Stripping
Strip with 4M HCL-0.15 H2O2
Wait 36 hours and load to Ln/DGA
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Ln/DGA Resin Separation
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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-1331040 pCi
• Ra-226 spk 5 pCi
• Ra-228 spk 20 pCi

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Spiked river water sample-1500 mL
Ra-226 and Ra-228 daughters
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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, _at_ 15 mL/ min.

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Spiked Groundwater sample-500 mL
Passed through TRU-DGA at 4M HCL evaporate and
precipitate
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Better alpha resolution with repass through
Ln-Resin after lowering acid to 0.1M HCL
Spiked LCS-1 liter
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Spiked Groundwater sample-1 liter FWHM81.6
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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-1331040 pCi Ra-226 spk 5 pCi Ra-228 spk
  20 pCi
• waited 36 hr/used Ln-DGA

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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