Direct extraction and high efficiency gross alpha detection of trace-level U or Pu actinides in deionized and saline water samples with CTMFDs

Studies were conducted to demonstrate the ability to directly extract U from pure and saline waters and then rapidly detect trace (0.02-0.2 mBq/mL) gross alpha particle emissions using centrifugally tensioned metastable fluid detectors (CTMFDs), which enable 4π (∼99 %) intrinsic alpha detection efficiency with keV-level resolution, while also exhibiting insensitivity to gamma and beta radiation. Actinide resin-extractant cartridges were used to extract U (in fresh and saline water) and Pu (in fresh water). A CTMFD-specific protocol was developed to remove the extractant and actinide from the cartridge, flushing with methanol and transferring into the CTMFD's sensing fluid, decafluoropentane (DFP), allowing gross alpha assay within hours. Effects of volumetric flow rate through the cartridge, actinide concentration, sensing fluid precompression, and salinity were assessed. The studies demonstrated the ability to reproducibly detect actinide content in deionized and saline (3.5 w% sea salt) water at levels commensurate with USEPA's minimum detectable activity (MDA) target levels, with uncertainty levels of 0.05 mBq/mL (0.2 pCi/L) range. The resulting method allowed direct extraction and reproducible monitoring within hours for actinides in 0.01M HNO₃ water at varying efficiencies- For U: ∼96 % (no salt); ∼80 % (3.5 w% sea salt); ∼10-20 % (salt with infused additives). For Pu: ∼60-80 % (non-saline).