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Analytical requirement

Rapid actinide measurements in environmental samples Dr Phil Warwick Geosciences Advisory Unit Southampton Oceanography Centre. Analytical requirement. Sequential Pu and U separation from soils Survey of the former Greenham Common airbase

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Analytical requirement

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  1. Rapid actinide measurements in environmental samplesDr Phil WarwickGeosciences Advisory UnitSouthampton Oceanography Centre

  2. Analytical requirement • Sequential Pu and U separationfrom soils Survey of the former Greenham Common airbase Survey of the environment around a UK nuclear weapons establishment 300 - 400 samples per year

  3. Final measurement techniques • Plutonium - Alpha spectrometric measurement of 239+240Pu and 238Pu • Uranium - 238/235 atomic ratio and U concentration by TIMS

  4. Conventional approach and associated problems • Sample dissolution Aqua regia leach or fluoride / pyrosulphate fusion Problems with incomplete dissolution or application of a potentially hazardous procedure • Pu and U separation Preconcentration / Anion exchange chromatography Long ion exchange columns and incomplete U / Fe separation

  5. Sample fusion • Complete sample dissolution can be achieved rapidly and effectively using a lithium borate fusion technique • The technique is routinely used in geological analysis for rock dissolution prior to ICP-AES measurement as well as in XRF analysis

  6. Isolation of Pu and U • Pu is readily isolated and purified using conventional anion exchange chromatography. • U isolated using UTEVA resin Good separation of U from Fe. U Kd on UTEVA is > 200

  7. Uptake of U on UTEVA

  8. Analytical technique - fusion • Thoroughly mix 5g of sample (ground) with 7g of lithium borate flux. Spike with 242Pu and 236U. • Fuse at 1200°C • Cast melt into 50ml of water. Add 50ml HNO3 and 1ml 0.2M PEG-2000 • Dissolve glass at 60°C overnight and filter to produce a clear solution

  9. Pu (Th) / U separation Load 8M HNO3 Wash 1 3M HNO3 Wash 2 (AX only) c. HCl Elution 1 (AX only) HCl / H2O2 Elution 2 (UTEVA only) 0.02M HCl

  10. Lithium borate fusion versus aqua regia digest for Pu Data for NIST 4353

  11. Lithium borate fusion versus aqua regia digest for U Data for NIST 4353

  12. Advantages • Rapid and efficient fusion procedure • Fast analysis - typically 2 days for 8 samples • Clean alpha spectrum - Good Pu recoveries (routinely 80-90%) U recoveries around 60 -70 % (not directly monitored) • U sources suitable for TIMS or alpha spectrometric measurement • Reduction in consumable costs as smaller columns are used (also UTEVA can be recycled)

  13. Further developments • Isolation of U and Th from sediments using UTEVA resin • Sequential separation of Pu and Am from sediments and biota using TRU resin Both techniques employ a lithium borate fusion followed by extraction chromatographic isolation of the analytes

  14. Acknowledgements • Co-workers I Croudace, R Taylor, J-S Oh, J Milton, S Dee • Funding bodies West Berkshire Council AWE Aldermaston

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