Rapid Actinide Analysis for Large Soil Samples

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Rapid Actinide Analysis for Large Soil Samples

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

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Background

• Need for improved analysis of large soil samples
  for actinides
• large sample size - lower detection limits
• total dissolution-refractory actinides
• minimize problems with column load solutions
• removal of soil matrix interferences
• consistency in tracer recoveries
• good alpha peak resolution

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Recent Work Using Actinide Resin (Dipex) and
Diphonix Resin

• Actinide Resin and Diphonex Resin
• W.C. Burnett et al, "Preconcentration of
  Actinide Elements from Soils and Large Volume
  Water Samples Using Extraction Chromatography".
  Journal of Radioanalytical Nuclear Chemistry.
  Vol. 226, (May 1997), 121-127.
• W.C. Burnett et al, Efficient Preconcentration
  and Separation of Actinide Elements from Large
  Soil and Sediment Samples, Analytical Chemistry,
  Vol. 72, pp. 4882-4887(2000)
• Diphonex Resin
• S.L. Maxwell and S. Nichols, Actinide Recovery
  Method for Large Soil Samples, Radioactivity and
  Radiochemistry Journal (January, 2001)

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Actinide Resin/Diphonix Resin-Soil

• Eliminated soil matrix but still had some
  disadvantages
• Actinide Resin/Diphonix Resin (Burnett)
• high phosphate -HEDPA solvent destruction
  (Fentons Reagent)- large TRU column
• Fe in Fentons reagent -cant stack TEVATRU
  cartridges
• Diphonix (Maxwell)-requires microwave dissolution
  of resin
• microwave work takes time/ can be tedious
• using HEDPA strip instead of microwave on fecal
  samples
• Pre-concentration steps take time and can have
  losses
• Need a simple, user-friendly, effective approach

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New Soil Method

• Cerium fluoride precipitation for soil matrix
  removal
• CeF3 used for high iron water samples
• M. Schultz et al, Analysis of Am, Pu and Th in
  Large Volume Water Samples in the presence of
  High Concentrations of Iron, International
  Radiochemical Analysis Conference, Maidstone,
  Kent, UK, Sept. 2002
• Rapid elimination of soil matrix problems
• Rare earth removal for large soil samples
  anyway-no extra separation time

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Benefits

• Faster
• After drying, blending, overnight furnace
• 1 day sample preparation 1 day column
  extraction
• Previous method 4-5 days
• Total dissolution (5-10 grams)
• High recoveries/clean spectra
• Eliminates interferences (Ex. Th, Po)
• Th-228 on Pu-238, Am-241, etc
• Po-210 affecting U-232

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Soil Sample Preparation

• Total dissolution and matrix removal (1 day)
• After drying and blending, heat at 550C
• Ash with nitric acid/HF to remove silicon, then
  fusion
• Fusion in zirconium crucibles for 20 minutes at
  700C
• 10 grams sodium peroxide 5 grams sodium
  hydroxide (or as needed for larger samples)
• Hydroxide precipitation
• Iron carrier with TiCl3 reductant
• Barium to eliminate carbonate interference
• Additional Ce carrier sometimes added here for
  very sandy samples to enhance precipitation

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Soil Sample Preparation, contd.

• Redissolve in dilute HCl and perform cerium
  fluoride precipitation (1 mg to 5 mg Ce) with
  TiCl3 present
• Rinse precipitate with 0.25M HCl- 6MHF with 0.02M
  rongalite present
• Soil load solution
• 5 mLs 3M HNO3-0.25M boric acid
• 6 mL 7M HNO3
• 7.5 mL 2M AL(NO3)3

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Transfer to crucible after silicon removal
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10 grams sodium peroxide 5 grams sodium
hydroxide
700C for 20 minutes
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Just add water after cooling briefly
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Dilute to 1 liter with water with iron carrier,
TiCl3, and barium present
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After centrifuging, acidify and add TiCl3, Ce
and HF.
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Place on ice, then centrifuge
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Rinse with dilute HCl, HF with rongalite present
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Redissolve in acid, boric acid and aluminum
nitrate
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TEVA TRU Resin-Stacked Cartridges
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Actinides in Soil
1) Redissolve in 18.5 mL 3M HN03 - 0.8M Al(NO3)3-
0.07M boric acid 2) Add 0.5 mL 1.5M Sulfamic Acid
1.25 mL 1.5M Ascorbic Acid 3) Add 1 mL 3 M
Sodium Nitrite
Rinse Beaker rinse 3mL 5MHN03 Separate
cartridges TEVA 5 mL 3MHN03 Collect/acidify -
with 2 mL16M HN03 then to TRU TEVA10 mL5M
HNO3 8 mL3M HN03
Th Elution 20mL 9MHCI
Pu (and/or Np) Elution 20mL 0.10MHCl - 0.05MHF -
0.03M TiCl3
Remove TRU cartridge 1) Elute Am with 15mL 4M
HCI 2) Add 3M HNO3 rinse from TEVA 3) 10 mL 6M
HNO3 -remove any Po-210 4) 15 mL 4M HCl-0.2M
HF-remove Th 5) Elute U with 15mL 0.1M ammonium
bioxalate
Add 0.5 mL 30 wt H2O2
2mL TEVA Resin (50-100 um)
Cerium fluoride
Alpha spectrometry
2.0mL TRU-Resin (3mL if needed) (50-100 um)
Cerium fluoride / Alpha spectrometry
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Am/RE Removal on TEVA
1) Evaporate 4M HCl with 5mL con.HNO3, 50 uL of
1.8M H2SO4, then ash with nitric acid and
hydrogen peroxide 2) Redissolve in 5 mL of 4M
NH4SCN, warm gently.
Rinse Beaker rinse 3mL 4M NH4SCN, warm 10 mL
1.5 M NH4SCN to column
Am Elution 25 mL 1M HCl (warm and rinse original
beaker)
2mL TEVA Resin (50-100 um)
Cerium fluoride
Alpha spectrometry
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Final Am Clean-up on TEVA
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QAP 0309-SOIL

• SRS EML Ratio
• Pu-238 14.9 14.6 1.021
• Pu-239 31.6 30.4 1.039
• Am-241 18.3 18.4 0.995
• U-234 117.7 127.3 0.925
• U-238 119.9 127.1 0.943
• Results in Bq/kg
• 5 gram sample analyzed

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QAP 0403-SOIL

• SRS EML Ratio
• Pu-238 0.826 0.82 1.007
• Pu-239 19.8 22.82 0.868
• Am-241 13.2 13.0 1.015
• U-234 86.7 87.22 0.994
• U-238 93.7 89.73 1.044
• Results in Bq/kg
• 5 gram sample analyzed

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Summary

• Large sample size
• Total dissolution
• fast fusion, multiple samples
• Removal of soil matrix interferences
• Cerium fluoride precipitation
• Reduced sample preparation time by 2 days
• Good tracer recoveries and alpha peak resolution
• Reduced spectral interferences