New Fecal Method for Plutonium and Americium at SRS

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New Fecal Method for Plutonium and Americium at
SRS

• Sherrod L. Maxwell III and David Fauth
• Savannah River Site

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Background

• SRS Incident in FB-Line
• Need for Improved Fecal Analysis for Pu and Am
• Complete dissolution of any plutonium oxide
  present
• Effective Th-228 removal

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New Approach

• Old method
• residual undissolved solids in final nitric acid
  solution
• solids contained some activity
• New approach
• Continue to use HNO3-HF dissolution/multiple
  digestion
• Apply Diphonix Resin technology
• Used successfully for large soil samples
• Allows loading from HCl-HF solutions
• Digest Diphonix using SRS microwave method
• Apply Eichrom sequential column method

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Method Details

• Fecal sample preparation
• Dry/weigh/flame/ash overnight
• Weigh ash in glass beaker
• Wet ash with HNO3, then H2O2, then HCl, then
  HNO3, then H2O2
• Wet ash with HNO3, then H2O2 until white or
  lavender
• Dissolve in 10 mL 1MHCL-0.2M HF
• Centrifuge, decant solution
• Add 10 mL 0.5M HCL-0.1M H3BO3 to solids, heat in
  teflon beaker
• Centrifuge, decant solution-separate H3BO3
  fraction

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Method Details

• Fecal sample preparation, contd.
• Heat in HNO3 HClHF H2O2 /go to near dryness
• Dissolve in 5 mL1M HCl-0.1M HF
• Centrifuge, decant solution
• Heat in HNO3 HF H2O2 / go to near dryness
• Dissolve in 5 mL 1M HCl-0.1M HF
• Centrifuge, decant solution
• Heat in HNO3 HF/ go to near dryness
• Centrifuge, decant solution
• Repeat HNO3 HF / and dissolve in 1M HCl-0.1M HF
  until completely dissolved.
• Combine clear HCl-HF fractions. Keep separate
  clear H3BO3 fraction.

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Method Details

• Actinide Preconcentration on Diphonix Resin
• Add ascorbic acid to HCL-HF and boric acid sample
  solutions
• Load HCl-HF sample aliquot to 2.4 ml Diphonix
  resin
• Load boric acid sample aliquot to same Diphonix
  column
• Rinse column with 10 mL 0.5M HCL-0.25M HF
• Rinse column with 5 mL 0.5M HCl
• Rinse column with 20 mL water

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Method Details

• Microwave Digestion of Diphonix Resin
• Microwave to 190C for 20 minutes in 10 mL 16M
  HNO3
• Vent microwave to 22O C for 35 minutes in 10 mL
  16M HNO3
• Add 3.5 mL 30wt H2O2 microwave to 21O C for 20
  minutes in 10 ml 16M HNO3
• Final wet ashing of Resin
• Ash with 30wt H2O2 four times
• Ash with HNO3 H2O2 two times, or until does
  not get any whiter

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Method Details

• Preparation for Pu, Am column separation
• Dissolve in 6 mLs of 5M to 6M HNO3
• Add 6 mLs 2 to 2.5M aluminum nitrate
• Solution ready for TEVA TRU Resin column
  extraction
• Preparation for Pu, Am column separation
• Valence adjustment for Pu
• 1) Add 1 mL 1.5M ferrous sulfate 1 mL 1.5M
  ascorbic acid, wait 3 min.
• 2) Add 1 mL 3.5M to 4M sodium nitrite

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Method Details

• Separate Pu using TEVA column
• Th removal 9M HCl8M HCl
• Use 2nd 1 mL TEVA column to remove all Th-228
• High retention/good clean-up
• Separate Am using TRU column
• Collect load plus rinse from 1st TEVA column
• Evaporate to dryness
• Redissolve in 15 mls 3 M HNO3
• Add 2 mLs 1.5M sulfamic acid 2.5 to 3 mls 1.5M
  ascorbic acid
• Load to TRU resin

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Pu, Am ON TEVA TRU RESIN (FECAL METHOD)
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TEVATRU Pu/Am Tracer Recoveries

• Fecal samples 1.5-4 grams ash/ Pu-242 spike
  1.26 dpm
• TEVA column 2nd 1 mL TEVA column
• Pu-242 Recovery Am-243 Recovery
• Fecal blank 1A 75.3 91.5 Fecal blank 1B
  68.5 103.1 Fecal blank 2 72.1 81.5
• Fecal blank 3 A 75.6 89.2
• Fecal blank 3 B 79.3 95.8
• Fecal blank 4 78.4 100.8
• Avg. 74.9 93.7
• Column Reagent blank 74.4 90.8
• Column Reagent blank 82.8 89.8
• Avg. 78.6 90.3

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Method Validation

• Analysis of multiple sample blanks
• Complete dissolution
• High tracer recovery
• Good Th-228 removal
• Analysis of artificial fecal sample spiked with
  Pu oxide from RESL-Idaho
• Test plan to validate versus known Pu levels

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Summary

• New fecal method dissolves Pu oxide using HNO3
  -HF
• Enables column loading from HCl-HF sample
  solutions with no visible solids
• High recovery/good Th-228 removal
• Diphonix technology compatible with fusion
  preparation as well (as demostrated with soil
  fusions)