Sheila Kramer-Tremblay

Ultra-trace determination of plutonium in urine samples using a compact accelerator mass spectrometry system operating at 300 kV

Accelerator mass spectrometry (AMS) is a very sensitive and robust technique for analysis of long-lived radionuclides. Employment of the AMS technique can reduce the demands on sample preparation chemistry, due to its high rejection of interferences and low susceptibility to sample matrix. This is particularly of interest for ultra-trace determination of 239Pu in bioassay and environmental samples, as other mass spectrometric methods such as inductively coupled plasma mass spectrometry (ICP-MS) can suffer from isobaric mass interferences by the presence of uranium in the sample. A rapid sample preparation method for analysis of Pu at femtogram levels in large volume urine samples is described. Using the compact ETH AMS Tandy facility operating at ∼300 kV, the method was validated by analysing urine samples spiked with known amounts of 239/240/241Pu ranging from 1 to 30 fg. The detection limits for the method were estimated to be 0.38 fg for 239Pu, 0.40 fg for 240Pu and 0.08 fg for 241Pu in 1400 mL of urine.

A bioassay method for americium and curium in feces

Fecal radiobioassay is an essential and sensitive tool to estimate the internal intake of actinides after a radiological incident. A new fecal analysis method, based on lithium metaborate fusion of fecal ash for complete sample dissolution followed by sequential column chromatography separation of actinides, has been developed for the determination of low-level Am and Cm in a large size sample. Spiked synthetic fecal samples were analyzed to evaluate method performance against the acceptance criteria for radiobioassay as defined by ANSI N13.30; both satisfactory accuracy and repeatability were achieved. This method is a promising candidate for reliable dose assessment of low level actinide exposure to meet the regulatory requirements of routine radiobioassay for nuclear workers and the public.

Rapid determination of 90 Sr/ 90 Y in water samples by liquid scintillation and Cherenkov counting

Strontium-90 (90Sr) is a ubiquitous contaminant at nuclear facilities, found at high concentrations in spent nuclear fuel and radioactive waste. Due to its long half-life and ability to be transported in groundwater, an accurate method for measuring 90Sr in water samples is critical to the monitoring program of any nuclear facility. To address this need, a rapid procedure for sequential separation of Sr/Y was developed and tested in groundwater samples collected from an area of riverbed affected by a 90Sr groundwater plume. Sixteen samples, plus spike and water blanks, were analyzed. Five different measurements were performed to determine the 90Sr and yttrium-90 (90Y) activities in the samples: direct triple-to-double-coincidence ratio (TDCR) Cherenkov counting of 90Y, liquid scintillation (LS) counting for 90Sr following radiochemical separation, LS counting for 90Y following radiochemical separation, Cherenkov counting for 90Y following radiochemical separation and LS counting of the Sr samples for 90Y in-growth. The counting was done using a low-level Hidex 300SL TDCR counter. Each measurement method was compared for accuracy, sensitivity and efficiency. The results following Cherenkov counting and radiochemical separation were in very good agreement with one another.

ICP-MS method for Pu and Np isotopes in population monitoring by a micro-flow injection sample introduction system

An ICP-MS method using a micro-flow injection (μ-FI) sample introduction system was developed for measuring 237Np and 239,240,241Pu in urine samples for sensitive and rapid population monitoring following a radiological or nuclear accident. Good selectivity from the chemical separation method allowed the determination of 237Np together with Pu isotopes using 242Pu as a tracer. Significant improvements in ICP-MS sensitivity and detection limit were achieved using the μ-FI sample introduction and the desolvation techniques. The method developed has been successfully applied to a set of human urine samples spiked with Pu isotopes and a set of rat urine samples with metabolized Pu isotopes from research experiments.

Rapid determination of 226Ra in urine samples

A new radiochemical separation method has been developed for rapid analysis of (226)Ra in urine samples. In this method, radium is separated from urine matrix using cation and anion exchange column chromatography. A (224)Ra tracer is added, together with its parent in the (228)Th standard, for chemical recovery correction. After separation, the sample is precipitated with hydrous titanium oxide and then prepared for counting by creating a thin-layer counting source using BaSO(4) micro-precipitation. The radium isotopes are then counted by alpha spectrometry. Replicate spike and blank samples were analysed for validation of the procedure. The detection limit was determined to be 0.22 Bq l(-1) with 4 h of counting for 20 ml of urine sample. Using this method, the results can be reported within an 8 h turn-around time. This method is suitable for quick dose assessment of (226)Ra exposure following a radiation emergency.

EURADOS intercomparison on emergency radiobioassay

Nine laboratories participated in an intercomparison exercise organised by the European Radiation Dosimetry Group (EURADOS) for emergency radiobioassay involving four high-risk radionuclides ((239)Pu, (241)Am, (90)Sr and (226)Ra). Diverse methods of analysis were used by the participating laboratories for the in vitro determination of each of the four radionuclides in urine samples. Almost all the methods used are sensitive enough to meet the requirements for emergency radiobioassay derived for this project in reference to the Clinical Decision Guide introduced by the NCRP. Results from most of the methods meet the requirements of ISO 28218 on accuracy in terms of relative bias and relative precision. However, some technical gaps have been identified. For example, some laboratories do not have the ability to assay samples containing (226)Ra, and sample turnaround time would be expected to be much shorter than that reported by many laboratories, as timely results for internal contamination and early decisions on medical intervention are highly desired. Participating laboratories are expected to learn from each other on the methods used to improve the interoperability among these laboratories.

Extraction of Tc(VII) and Re(VII) on TRU resin

Abstract TRU resin can be used to rapidly and selectively extract Tc(VII) and Re(VII). The retention capacity curves of Tc(VII) and Re(VII) for HNO3, HCl, H2SO4 and H3PO4 solutions were studied and prepared. Tc(VII) and Re(VII) were simultaneously extracted in 2 M H2SO4 and 1.5 M H3PO4 and were effectively separated from Mo(VI) and Ru(III). Tc(VII) and Re(VII) remained strongly bonded to the resin even after washing using a large volume of 2 M H2SO4 at a relatively high flow rate. Also, they were both completely eluted from the resin using 15 mL of near boiling water, an eluent directly compatible for ICP-MS instrument measurements.

Determination of Atto- to Femtogram Levels of Americium and Curium Isotopes in Large-Volume Urine Samples by Compact Accelerator Mass Spectrometry

Ultralow level analysis of actinides in urine samples may be required for dose assessment in the event of internal exposures to these radionuclides at nuclear facilities and nuclear power plants. A new bioassay method for analysis of sub-femtogram levels of Am and Cm in large-volume urine samples was developed. Americium and curium were co-precipitated with hydrous titanium oxide from the urine matrix and purified by column chromatography separation. After target preparation using mixed titanium/iron oxides, the final sample was measured by compact accelerator mass spectrometry. Urine samples spiked with known quantities of Am and Cm isotopes in the range of attogram to femtogram levels were measured for method evaluation. The results are in good agreement with the expected values, demonstrating the feasibility of compact accelerator mass spectrometry (AMS) for the determination of minor actinides at the levels of attogram/liter in urine samples to meet stringent sensitivity requirements for internal dosimetry assessment.