ra in water using mno2 resin: update
DESCRIPTION
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 - PowerPoint PPT PresentationTRANSCRIPT
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– 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
• 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
• 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
• 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
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
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
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 Loading
Column Stripping
Strip with 4M HCL-0.15% H2O2
Wait 36 hours and load to Ln/DGA
Ln/DGA Resin Separation
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
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/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.
Spiked Groundwater sample-500 mL
Passed through TRU-DGA at 4M HCLevaporate and precipitate
Spiked LCS-1 liter
Better alpha resolution with repass through Ln-Resin after lowering acid to 0.1M HCL
Spiked Groundwater sample-1 literFWHM=81.6
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
• 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