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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

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
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)
ra 226 and ra 228 in water
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
ac 228 on dga resin
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
improvements
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
ra 226 in water
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
column stripping
Column Stripping

Strip with 4M HCL-0.15% H2O2

Wait 36 hours and load to Ln/DGA

ra 226 228 recoveries
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

slide13

Spiked river water sample-1500 mL

Ra-226 and Ra-228 daughters

ra 226 in groundwater
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.
slide15

Spiked Groundwater sample-500 mL

Passed through TRU-DGA at 4M HCL

evaporate and precipitate

slide16

Better alpha resolution with repass through Ln-Resin after lowering acid to 0.1M HCL

Spiked LCS-1 liter

ra 226 and ra 228 in groundwater
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

summary
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