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Ra in Water using MnO2 Resin: New Developments
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 (1.5L) 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
• MnO2 Resin from Eichrom• 1.25 g MnO2 Resin• 1.5 liter samples + Ba-133 tracer• pH adjustment to 6-7• Flow rate ~20 mL/min• Vacuum box loading with inner liner
– ~ 1.5 hour loading
– speed & ability to deal with slow samples
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Ra-226 and Ra-228 in Water
• Initial testing
• Strip MnO2 with 20 mL 2M HCL-1% H2O2
– evaporated and redissolved in 0.075M HCL
• Hold >30 hrs for Ac-228 ingrowth• Ln-Resin tests
– 10 mL 0.075M HCL load + 5 mL 0.075M beaker rinse– 10 mL 0.090M HCl Rinse– 15 mL 0.35M HNO3 strip– Had some inconsistencies that seemed related to Mn in load solution
• Instead, strip MnO2 with 15 mL 4M HCL-1.5% H2O2 and use…….
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Ac-228 on DGA Resin
• TRU (1 mL) + DGA-Normal (2mL) stacked– TRU (U,Th removal) and DGA (Ac-228 retention)
– No impact from Mn on Ac-228 recovery
– loaded 15 mL strip solution from MnO2 resin on TRU-DGA
– collect load + 5 mL 4M HCL rinse for Ra-226
– 10 mL 4M HCL rinse-discard
– Discard TRU Resin
– Strip Ac-228 from DGA with 10 mL 0.5M HCl
– 100 uL Ce and 1 mL con. HF
– Consistent high recoveries of Ac-228
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10-2 10-1 100 101
10-1
100
101
102
103
104
105
106TN-DGA ResinTRU Resin
Np(V)
Am(III)
Np(IV)
U(VI)
Comparison of TRU and DGA Resins
k'
[HNO3]
10-2 10-1 100 10110-1
100
101
102
103
104
105
106
Am(III)
U(VI)
Th(IV)
Th(IV)
Pu(IV)
[HNO3]
Slide- E. P. Horwitz, May, 2004 User’s Meeting
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10-2 10-1 100 101
10-2
10-1
100
101
102
103
104
105
106TN-DGA ResinTRU Resin
Am(III)
Np(IV)
U(VI)
Comparison of TRU and DGA Resins
k'
[HCl]10-2 10-1 100 101
10-2
10-1
100
101
102
103
104
105
106
Am(III)
U(VI)
Th(IV)
Th(IV)
Pu(IV)
[HCl]
Slide- E. P. Horwitz, May, 2004 User’s Meeting
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Ra-226 and Ra-228 in Water
• Evaporate load + rinse solutions from TRU-DGA
• Redissolve in 0.075M HCl
• Precipitate Ra-226 (Ra-224) using Ba sulfate
• 100 uL of 0.70 mg/mL Ba + 3 mL 40% sodium sulfate + 4 drops 1:1 acetic acid/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
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Column Fully Stripped
Collect 4M HCL-0.15% H2O2 and load to DGA
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TRU/DGA Resin Separation
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Ba-133 Recovery on MnO2 Resin
1 g MnO2 1.25 g MnO2
81% 94%
85% 90%
87% 90%
95% 92%
Avg. 87% 91%
Ba-133=1040 pCi in 1.5 L groundwater samples @ 20 mL/min.
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Ra-228 by Ac-228 on DGA
% Recovery % Recovery
Ba-133 Ra-228
LCS (spiked DI H2O) 62% 98.0%
River smp 108% N/A
River smp spk 95% 99.0%
River smp spk 100% 86.5%
River smp 102% N/A
River smp spk 106% 84.3%
River smp spk 93% 107.9%
Avg = 95.1%±10.1%
Ba-133= 1040 pCi, 1.5L sample, 67.8 pCi Ra-228@ 20 mL/min.
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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-133=1040 pCi
Ra-226 spk= 5 pCi
Ra-228 spk= 20 pCi
Initial Ra-228/Ac-228 using Ln-Resin low/ waited 30 hr/used DGA
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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, @ 15 mL/ min.
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Spiked Groundwater sample-500 mL
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Summary
• Ra-226 and Ra 228 using MnO2 resin– Ra-226 using barium sulfate micro-precipitation – TRU/DGA Resin -Ra-228 via Ac-228– Speed and selectivity
• Vacuum Box method– Rapid flow rates– 1.5 L loaded and stripped < 2 hours
• Benefits– Fast, easy separation (<1 hr loading for 500 mL groundwater
sample)– Consistent– Increased productivity
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Acknowlegments
• Eichrom-Larry Jassin and Anil Thakkar
• W. Burnett et al, MnO2 Resin
• PGRF- E.P. Horwitz et al– DGA and MnO2
• Joyce Ray, SRS, lab technician