Computational Approaches on Photon-Attenuation and Coincidence-summing Corrections for the detection of gamma-emitting radionuclides IN foods.

Source-based calibration methods used for photon attenuation and coincidence summing corrections are time consuming and require multiple certified standards that match sample geometry with varying densities. Three programs which are capable of simulating a variety of sample geometries, matrix compositions, and sample densities have been examined as alternatives. LabSOCS, ANGLE 3 and GESPECOR are effective at generating efficiency curves for food matrices with a range with different densities. The curves generated have been successfully used to determine activity in food samples.

Rapid detection of enriched uranium in food.

We have developed a quadrupole ICP-MS method for detecting sub-picogram quantities of 235U in contaminated foods. Notable features included elimination of the requirement for possessing licensed nuclear materials so that non-radiochemical laboratories may perform this analysis in the event of a large-scale nuclear or radiological emergency calling for high sample surge capacity, elimination of several extremely hazardous reagents in sample analysis e.g. aqua regia and hydrofluoric acid, and the method was developed for applying a moderately priced, and widely used quadrupole inductively coupled plasma mass spectrometer (Q-ICP-MS). This method could be quickly implemented at many laboratories to increase emergency response capability.

Isotopic analysis of plutonium in foods by inductively-coupled plasma mass spectrometry.

Pu isotopes in various foods were detected using a quadrupole ICPMS and Aridus II desolvation nebulizer. The method has ability to detect 239Pu and 240Pu at concentrations of ~52pg/kg (0.12Bq/kg) and ~9.5pg/kg (0.08Bq/kg) as well as 240Pu/239Pu ratio in <8h after receiving the samples. Foods were wet-ashed followed by DGA extraction for eliminating matrix, isobaric, and polyatomic interferences. A UH+ formation rate <10-5 and a 5-fold enhanced sensitivity for Pu was achieved after system optimization.

Analysis of radioactive strontium-90 in food by Cerenkov liquid scintillation counting.

A simple liquid scintillation counting method using DGA/TRU resins for removal of matrix/radiometric interferences, Cerenkov counting for measuring 90Y, and EDXRF for quantifying Y recovery was validated for analyzing 90Sr in various foods. Analysis of samples containing energetic ß emitters required using TRU resin to avoid false detection and positive bias. Additional 34% increase in Y recovery was obtained by stirring the resin while eluting Y with H2C2O4. The method showed acceptable accuracy (±10%), precision (10%), and detectability (~0.09Bqkg-1).