Rapid Actinide Analysis for Large Soil Samples

1. Rapid Actinide Analysis for Large Soil Samples Sherrod L. Maxwell, III Westinghouse Savannah River Company

2. 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

3. 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)

4. Actinide Resin/Diphonix Resin-Soil • Eliminated soil matrix but still had some disadvantages: • Actinide Resin/Diphonix Resin (Burnett) • high phosphate -HEDPA solvent destruction (Fenton’s Reagent)- large TRU column • Fe in Fenton’s reagent -can’t stack TEVA+TRU 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

5. 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

6. 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

7. 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

8. 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

9. Transfer to crucible after silicon removal

10. 10 grams sodium peroxide + 5 grams sodium hydroxide 700C for 20 minutes

11. Just add water after cooling briefly

12. Dilute to 1 liter with water with iron carrier, TiCl3, and barium present

13. After centrifuging, acidify and add TiCl3, Ce and HF.

14. Place on ice, then centrifuge

15. Rinse with dilute HCl, HF with rongalite present

16. Redissolve in acid, boric acid and aluminum nitrate

17. TEVA +TRU Resin-Stacked Cartridges

18. 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 TEVA:10 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

19. 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

20. Final Am Clean-up on TEVA

24. 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

25. 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

28. 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