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One-Column Separation and Analysis of Isotopic Am and Pu in Soil Samples

One-Column Separation and Analysis of Isotopic Am and Pu in Soil Samples. Nidal M. Jadalla , Eberline Services, Albuquerque, NM Anil Thakkar, Eichrom Technologies, Inc. Objective.

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One-Column Separation and Analysis of Isotopic Am and Pu in Soil Samples

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  1. One-Column Separation and Analysis of Isotopic Am and Pu in Soil Samples • Nidal M. Jadalla, Eberline Services, Albuquerque, NM • Anil Thakkar, Eichrom Technologies, Inc.

  2. Objective • Develop an efficient, reliable, and cost-effective method to analyze isotopic americium and plutonium in soil samples.

  3. First Approach 1-Sample Preparation (500 C Furnace and Microwave Digestion) 2-Digested sample in ~200 ml of 1M HN03 solution 3-Add NH4OH to precipitate Fe in the sample 4-Centrifuge and collect the precipitate 5-Dissolve precipitate in 3M HNO3- 1.0M Al(NO3)3. Add ascorbic acid. 6-Condition TRU Resin 3M HNO3 7-Charge sample. 8-Oxidize to Pu+4 with 2M HNO3-0.1M NaNo2 solution 9-Elute Am with 4M HCl 10-Elute Pu with 25 ml 4M HCl-0.833 ml 20% TiCl3 11-Prepare Source by NdF3 precipitation.

  4. Problems • Low americium chemical recoveries in soil (particularly with high iron content) • Isotopic Th frequently appears in the plutonium spectrum (Th-228/Pu-238 overlapping).

  5. Current Method: 1-Sample Preparation (500 C Furnace and Microwave Digestion) 2-Digested sample in ~200 ml of 1M HNO3. Add Ca carrier and oxalic acid. Precipitate calcium oxalate with NH4OH at pH 3-4 3-Dissolve precipitate in 3M HNO3- 1.0M Al(NO3)3 4-Condition TRU Resin 3M HNO3 5-Charge Sample. 6-Oxidize to Pu+4 with 2M HNO3-0.1M NaNo2 solution 7-Elute Am with 4M HCl 8-Elute Pu with 25 ml 4M HCl-0.833 ml 20% TiCl3 9-Prepare Source by NdF3 precipitation.

  6. Low Am-243 Chemical Recovery • Frequent problem in soil matrix when TRU resin is used. • Possible reason: Matrix effect (Presence of Fe+3). • Proposed solution: Precipitate as calcium oxalate to eliminate matrix interference

  7. Thorium in Pu Spectrum • Sample is being Digested. Thorium is retained on column and a small but noticeable fraction elutes with Pu. • Proposed Solution: 1- Sample leaching instead of digestion. 2- Add a 25 ml rinse of 4M HCL-0.1M HF to remove remaining Th.

  8. Procedure: Sample Prep. (3) Volume to 500 ml with DI H2O. Stir and heat (1) Leach 1 g of Soil 40 ml HNO3. Heat and stir 4 hrs (2) Transfer to C-tubes. Decant into 500 ml beaker (5) Bring to PH=3 using NH4OH. Stir for 30 more min (4) Add oxalic acid and calcium carrier (6) Let precipitate settle and decant. Wash precipitate (9) Dissolve in 20 ml 3M HNO3- 1.0M Al(NO3)3 (7) Heat precipitate At 500 C for 6 hr (8) Aqua Regia. Digest with HNO3

  9. Procedure: TRU Resin LoadSolution 10 ml 2M HNO3- 0.1M NaNO2 25 ml 4M HCl-0.8333 ml TiCl3 20 ml 4M HCl 25 ml 4M HCL-0.1M HF Am Pu

  10. Results:Th Interference

  11. Results: Chemical Recoveries

  12. Results: Precision and Accuracy

  13. Conclusions • Modified procedure significantly improves Am chemical recovery • Modified procedure reduces Pu tracer recovery by an average of 10-15% • Th-228 may interfere in Pu spectrum unless leaching and additional rinse to the TRU column is added.

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