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New Fecal Method for Plutonium and Americium at SRS

New Fecal Method for Plutonium and Americium at SRS. Sherrod L. Maxwell III and David Fauth Savannah River Site. Background. SRS Incident in FB-Line (9/1/99) 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 Fecal Method for Plutonium and Americium at SRS

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  1. New Fecal Method for Plutonium and Americium at SRS Sherrod L. Maxwell III and David Fauth Savannah River Site

  2. Background • SRS Incident in FB-Line (9/1/99) • Need for Improved Fecal Analysis for Pu and Am • Complete dissolution of any plutonium oxide present • Effective Th-228 removal • Completed FB-Line incident samples • Successful routine operation

  3. New Approach • Old method: • residual undissolved solids in final nitric acid solution • solids contained some activity • New approach: • Use HNO3-HF dissolution/multiple digestions • Apply Diphonix Resin technology used successfully for large soil samples • Digest Diphonix using SRS microwave method • Apply Eichrom sequential column method

  4. Actinide Retention on Diphonix Resin Ref: E. Philip Horwitz et al.,Separation Science and Technology, 32, 1, (1977)

  5. Performance on Large Soil Samples

  6. Pu, Am on DIPHONIX RESIN • Redissolve in 0.5M to1M HCL-0.1M to 0.2M HF • Redissolve any solids that precipitate in 0.5M HCL-O.25M H3BO3 • Add 1.5M Ascorbic Acid (Reduce Fe) • Load HCl-HF and HCl- H3BO3 fractions separately Rinse 2 10mL 0.5MHCL Rinse 1 20mL 0.5MHCL-0.25M HF Rinse 3 20mL water 2.4 mL Diphonix Resin

  7. Method Digestion Details • Microwave Digestion of Diphonix Resin • Microwave to 190C for 15 minutes in 10 mL 16M HNO3 • Change disk/microwave to 200C for 20 minutes in 10 mL 16M HNO3 • Change disk/ microwave to 215 C for 25 minutes in 10 mL 16M HNO3 • Add 3.5 mL 30wt% H2O2 & microwave to 21O C for 10 minutes in 10 ml 16M HNO3 • Final wet ashing of Resin • Ash with 30wt% H2O2 four times • Ash with HNO3 + H2O2 one time, or until does not get any whiter

  8. Pu, Am Column Separation • 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

  9. Pu, Am Column Separation • Separate Pu using TEVA column • Th removal 9M HCl+8M 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 + 5 mls 1.5M ascorbic acid • Load to TRU resin

  10. Pu, Am ON TEVA + TRU RESIN (FECAL METHOD)

  11. Pu on TEVA RESIN (2nd Column to Remove all Th-228) • Redissolve in 7.5mL 3M HN03 + 1mL 2.5M Al(NO3)3 • Add 0.5mL 1.5M Ferrous Sulfate + 1mL 1.5M Ascorbic Acid • Add 1mL 3.5M Sodium Nitrite • Add 1mL 16M Nitric Acid Th Removal 2mL 9MHCI/8mL 8MHCI Rinse 10mL 3MHN03 Pu Elution 15mL 0.10MHC1 - 0.05MHF - 0.1M NH4l 1mL TEVA Resin

  12. 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 DOE RESL-Idaho • Test plan to validate versus known Pu levels

  13. TEVA+TRU 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 78.4100.8 Avg. 74.9 93.7 Column Reagent blank 74.4 90.8 Column Reagent blank 82.889.8 Avg. 78.6 90.3

  14. Assay of of DOE-RESL Fecal Standards RESL RESL SRS Measured Bias vs. RESL % Std. Dev. Stds. Ref. Values Values Values Bewteen Dups. Picocuries Picocuries 1 std. dev SR-194 #1 1.860 -14.7% #2 1.841 -15.6% SR-194 Pu-239 2.18 Avg 1.850 -15.1% 1.0% #1 2.405 -12.8% #2 2.608 -5.5% SR-194 Am-241 2.76 Avg 2.507 -9.2% 10.1% SR-234 #1 2.062 -3.2% #2 2.139 0.4% SR-234 Pu-239 2.13 Avg 2.101 -1.4% 3.9% #1 2.488 -7.8% #2 2.335 -13.5% SR-234 Am-241 2.70 Avg 2.411 -10.7% 7.7% DOELAP Bias Criteria: -25% to +50% DOELAP Standard Deviation Criteria:<40%

  15. Sr in Fecal Samples Approach • Collect rinses from Diphonix columns • Evaporate/Dissolve in 8M HNO3 • Separate on Sr-Resin Preliminary Results • 90% recovery on spiked samples • Good precision on DOELAP samples

  16. DOELAP SR RESULTS Samples Blanks Spike Spike Spike Added Measured Recovery (pCi) (pCi) (pCi) (pCi) (%) 1) 258 0.98 194.5 178.5 91.8 2) 285 0.78 178.7 91.9 3) 287 1.32 4) 244 0.44 5) 254 6) 253 Avg. 263 0.88 178.6 Stdev 6.9% 41.6% 0.11%

  17. Summary • New fecal method dissolves Pu oxide using HNO3 -HF • Column loading from HCl-HF sample solutions with no visible solids • High recovery/accurate results/good Th-228 removal • Sr-90 can also be assayed

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