Development of New Column Extraction Methods

1. Development of New Column Extraction Methods Sherrod L. Maxwell, III Westinghouse Savannah River Site

2. Approach • Ion exchange, solvent extraction, or extraction chromatography? • Sample matrix, analyte levels, interferences? • Separation efficiency vs. interferences, ruggedness, sample frequency, turnaround time, detection limit, consistency of chemical yields, cost, alpha peak resolution, radiological containment, space limitations, automation, sequential analysis, waste disposal • Ex.: low level Pu in urine • 500+mL sample size, handle high phosphate and calcium, ensure good Th-228 removal, sequential analysis for other actinides plus Sr, high throughput, minimize acid waste, good alpha peak resolution, high tracer recoveries, DOELAP accuracy and precision criteria, etc.

3. Approach • Sample matrix, analyte levels, interferences? (contd) • Dissolution required? • fusion or complete digestion vs leach (microwave, hot plate, furnace) • Analyte stable in separation matrix? (Ex. Ti in fecal samples after dissolution, do I need HF to stabilize?, if so can I still extract?) • Tracer selection (Pu-242 vs. Pu-236 or Sr-85 vs. stable Sr) • traceability, tracer contamination level, equipment available, (e.g. gamma PHA for Sr-85) • Interference type • U-238 mass on Pu-238, Am-241 on Pu-241 (ICP-MS or TIMS) • Th-228 on Pu-238, Am-241 alpha spectrometry • U by KPA laser phosphorescence (quenchers such as Fe) • U, Pu spectral interferences on ICP-AES • Beta interferences on Tc-99, Sr-90

4. Approach • Preconcentration/dilution required? • Evaporation • Precipitation (calcium phosphate, iron hydroxide, etc.) • Resin (cation resin for Sr in water, Diphonix or Dipex from soil, fecal) • Aliquot size limited by radiation levels (process dissolver samples) • Valence adjustment? • Pu+3, Pu +4, Pu +5, Pu +6 • Np +4, Np +5, Np +6 • U +4 ,U +6 • Am +3, Cm +3, rare earths • Th +4, Sr +2 • Oxidants/reductants (efficiency, interference, waste, corrosion, destruction, redissolution) • If evaporate strip solution, readjustment required? form Np+5, Np+6, Pu+6

5. Approach • Analytes together, matrix limitations ? • Ex. Pu , Th, Np by ICP-MS • Pu and Np by alpha spectrometry (with Pu-236 tracer) • Process samples with high Pu (may not need Th removal) • Np assay in process samples with extremely high Pu (need Pu removed from Np due to tail overlap on Np-237) • Depends on levels and assay type (alpha spectrometry vs mass spectrometry)

6. Approach • Final strip solution matrix: • Interferences on assay method • Low salt for alpha planchet, TIMS filament or ICP-MS assay • Evaporation needed/available (e.g. Ti+3, NH4I, HF) • Ex. second column separation required/hard to redissolve Ti • Ashing required for electrodeposition (optimal # of ashing cycles) • Extractant or resin bleed-off (Am on TRU resin) • Dilute sulfuric acid enhances destruction on ashing • REE removal on TEVA for Am from soil/destroy extractant bleed well

7. Extraction chromatography options • Offers selectivity over ion exchange • Aluminum to complex matrix interferences/supplement nitrate levels • 0.5M to 1.25M aluminum nitrate • Gravity flow vs. vacuum • Vacuum 3X to 5X faster • Helps with stubborn sample flow/particluates • Need 50-100 micron size (now in cartridges from Eichrom) • Keep lid clean/control flow rate • Sequential options • Pu on TEVA or TRU • U on UTEVA or TRU • TEVA +TRU vs. UTEVA+TRU • Cerium fluoride vs. electrodeposition (alpha spectrometry)

8. Pu on TEVA Approach • TEVA (Pu, Np, Th) +TRU (U, Am) approach • Can separate Pu and Np together; good U, Th removal • Pu loading as strongly retained Pu+4 instead of Pu+3 • Pu stripped with less difficult matrices for some types of assay • Better Th removal/recovery on TEVA with no competition from U (from soil for ex.) • Second TEVA column can be applied for additional Th, U removal

9. Pu on TEVA Approach • TEVA (Pu, Np, Th) +TRU (U, Am) approach • No Th-228 in Am fraction from TRU resin • Any residual Th-228 on TRU in U strip does not interfere as it does with Pu-238 on TRU • For urine, with no iron in samples, stacked cartridges (TEVA+TRU) can be used • If iron in samples or is used in valence adjustment, evaporate load + rinse from TEVA, redissolve, add ascorbic acid + sulfamic acid and then load to TRU • Can insert UTEVA for U if you want low salt strip for TIMS or ICP-MS

10. Pu on TRU Approach • UTEVA (U, Th) +TRU (Pu, Am) approach • Can separate Pu and Am from same resin (TRU) • Cartridges can be stacked in single column (UTEVA+TRU) since Fe reduced to Fe+2 in load solution for all samples (no evaporation step prior to TRU resin) • Pu can be stripped with HCL-Ti(III) for enhanced separation from U, Th vs. older TRU methods • TRU retention still high for Pu despite loading as Pu+3 since Pu converts rapidly to Pu+4

11. Pu on TRU Approach • UTEVA (U, Th) +TRU (Pu, Am) approach • Retains uranium that may come through UTEVA • Th recovery on UTEVA not as good as TEVA (for soil, sediments) • Th occasionally in Am/Pu fractions • Np not recovered with Pu • Can insert TEVA prior to UTEVA to remove/recover Th and Np

12. Examples • Actinides in water • Pu, Am, U, Sr at low levels • 500 mL water sample (10 liters?) • Evaporation or precipitation? • Interferences: how high can I tolerate? • Tracers? • Sequential options? • Valence adjustment? • Gravity flow or vacuum? • Add Np as analyte?

13. Examples • Np-237 in mixed Pu/U oxide? • Dissolve? • Resin? • Valence adjustment? • Assay? • Interferences? • Tracers, spikes, or standards? • Gravity flow or vacuum? • Np in Pu metal?

14. Summary • Many factors have to be considered/needs are different • Preconcentration methods and highly selective extraction chromatography methods are available • Information exchange valuable • User workshops • Journals/radchem message groups via email • Eichrom web page/procedures • Call Larry