Deconvolution of liquid scintillation alpha spectra of mixtures of uranium and radium isotopes

A liquid scintillation analysis method for low-level radioactive wastewater

There is currently general concern over low-level radioactive wastewater from the development of nuclear industry. In this paper, a method based on an ultralow-level liquid scintillation spectrometer for measuring uranium radioactivity in low-level radioactive wastewater is proposed. This method can easily and quickly measure the radioactivity level of uranium in samples and can even distinguish the main isotopes of uranium. The liquid scintillation method directly provides results in units of radioactivity activity concentration, which are more convenient for comparison with relevant national standards to determine whether the emission standards are met. The lowest limit of detection of this method is 0.014 Bq l^-1within 600 min.

A rapid method to determine 226Ra concentrations in Marcellus Shale produced waters using liquid scintillation counting

Concentrations of naturally occurring radioactive material (NORM) in Marcellus Shale produced water presents a challenge for effective management and treatment, because of the vast fluid volumes generated. With an increased emphasis on beneficial reuse and resource recovery from the produced waters, a rapid, yet reliable, method for quantifying radium in these produced waters is needed. The high total dissolved solids (TDS) concentration introduces difficulties when measuring ²²⁶Ra by recommended EPA methods that were specifically developed several decades ago for drinking water. While other techniques for measuring radium in these high-TDS fluids have since been developed, these newer techniques often require extensive and complicated pre-concentration steps; and they thus require extensive analytical chemistry skills, utilize hazardous chemicals like hydrofluoric acid, demand long holding times or measurement times, and require high sample volumes. We present a rapid method for ²²⁶Ra measurements in high-TDS produced waters by liquid scintillation counting, which has been corroborated herein by concurrent gamma spectrometry analyses. Samples were prepared for analysis by evaporating the fluid and re-suspending the evaporate with acidified distilled deionized water prior to liquid scintillation counting for 1 h. This protocol yielded radium recoveries ≥93%. Per this protocol, the alpha and beta spectra of ²²⁶Ra and its daughters were computationally separated by alpha-beta discrimination and spectrum deconvolution. The minimum detectable activities of ²²⁶Ra was 0.33 Bq/L (9.0 pCi/L) when the counting time was 60 min and the sample volume was 4 mL. Nine produced waters of varying TDS and radium concentrations from the Marcellus Shale Formation were analyzed by this method and compared with gamma spectroscopy; and these yielded comparable results with an R² of 0.92. The reduced sample preparation steps, low cost, and rapid analysis position this as a well-suited protocol for field-appraisal and screening, when compared to comprehensive radiochemical analysis. We offer that for a given produced water region, routine and local liquid scintillation analyses can be compared and calibrated with infrequent gamma spec analyses, so as to yield a near-real time protocol for monitoring ²²⁶Ra levels during hydrofracturing operations. We present this as a pragmatic and efficient protocol for monitoring ²²⁶Ra when produced water samples host low levels of ²²⁸Ra-since the progeny of ²²⁸Ra can significantly confound the LSC analyses.

Magnetic iron oxide nanoparticles for the collection and direct measurement of adsorbed alpha-emitting radionuclides from environmental waters by liquid scintillation analysis

Radioactive contamination, be it from accidental or intentional release, can create an urgent need to assess water and food supplies and the environment, and monitor human health. In the event of such an emergency, rapid and efficient methods may be needed to assess contamination levels in scores of samples within a short time frame. Internalized exposure to radionuclides that decay by alpha (α) emission can be especially hazardous, given the strongly ionizing nature of the α particle. Unfortunately, the determination of α-emitting radionuclides using traditional radioanalytical methods is typically labor and resource intensive and time consuming. In an effort to devise methods that are fast, require little labor and laboratory expendables, and minimize the use of toxic or corrosive reagents, researchers at PNNL have evaluated superparamagnetic nanoparticles as extracting agents for α-emitting radionuclides from chemically unmodified and acidified (pH 2) aqueous systems. It is demonstrated that bare magnetite nanoparticles exhibit strong affinity for two representative α-emitting radionuclides (241Am and 210Po) from two representative aqueous matrices (river and ground water). Furthermore, use of the superparamagnetic properties of these nanomaterials to concentrate the analyte-bearing solids from the bulk aqueous solution has been demonstrated. The nanoparticle concentrate can be either directly dispensed into a scintillation cocktail, or first dissolved and then added to a scintillation cocktail as a solution for an α-emission assay by liquid scintillation analysis. Despite the severe quenching caused by the metal oxide suspensions in the cocktail, the authors have demonstrated that modern liquid scintillation analyzers can report accurate α activity count rates; the upper limits of nanoparticle suspension concentrations in a cocktail are reported for cases wherein normal instrument count mode and a quench correction protocol are used. Discussions are provided on the presented sample processing and analysis method, the improvement (lowering) of minimum detectable activity concentrations using the nanoparticle-based assay method, and the quenching effects of nanoparticle suspensions in a scintillation cocktail.