Ra in Water using MnO2 Resin: New Developments

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– 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)

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

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…….

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

10-2 10-1 100 10110-1

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

10-2 10-1 100 10110-2

10-1

100

101

102

103

104

105

106 TN-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

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

Column Loading

Column Stripping

Column Fully Stripped

Collect 4M HCL-0.15% H2O2 and load to DGA

TRU/DGA Resin Separation

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.

Ra-228 by Ac-228 on DGA

% Recovery % Recovery Ba-133 Ra-228

LCS (spiked DI H2O) 62% 98.0%River smp 108% N/ARiver smp spk 95% 99.0%River smp spk 100% 86.5%River smp 102% N/ARiver 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.

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/ARiver 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 pCiRa-226 spk= 5 pCi Ra-228 spk= 20 pCiInitial Ra-228/Ac-228 using Ln-Resin low/ waited 30 hr/used DGA

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

Ra-226 in Groundwater % Recovery % Recovery

Ba-133 Ra-226

Blank (DI H2O) 86.3% N/ALCS (spiked DI H2O) 88.6% 104%Grndwater smp 87.3% N/AGrndwater smp spk 88.6% 87.3%Grndwater smp 92.4% N/AGrndwater smp spk 92.7% 89.1%Tapwater smp 84.6% N/ATapwater 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.

Spiked Groundwater sample-500 mL

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

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