Rapid Actinide Measurements in Environmental Samples: Techniques and Innovations
Dr. Phil Warwick from the Geosciences Advisory Unit at Southampton Oceanography Centre discusses advanced techniques for the rapid measurement of actinides in environmental samples, focusing on plutonium (Pu) and uranium (U) separation from soils at sensitive sites like the former Greenham Common airbase. This paper details the challenges associated with conventional methods, and highlights a lithium borate fusion technique for sample dissolution that improves analytical efficiency. Key improvements include enhanced separation via UTEVA resin and reduced analytical timelines, resulting in fast, reliable nuclide recovery rates suitable for environmental monitoring.
Rapid Actinide Measurements in Environmental Samples: Techniques and Innovations
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Presentation Transcript
Rapid actinide measurements in environmental samplesDr Phil WarwickGeosciences Advisory UnitSouthampton Oceanography Centre
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
Final measurement techniques • Plutonium - Alpha spectrometric measurement of 239+240Pu and 238Pu • Uranium - 238/235 atomic ratio and U concentration by TIMS
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
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
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
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
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
Lithium borate fusion versus aqua regia digest for Pu Data for NIST 4353
Lithium borate fusion versus aqua regia digest for U Data for NIST 4353
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)
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
Acknowledgements • Co-workers I Croudace, R Taylor, J-S Oh, J Milton, S Dee • Funding bodies West Berkshire Council AWE Aldermaston
