A highly sensitive method for the reassessment and quantification of 239Pu in urine samples based on a 1 MV accelerator mass spectrometry system

Abstract

A new and highly sensitive method for the determination of 239Pu in human urine has been developed permitting the reassessment of planchets initially prepared for alpha spectrometry (AS) analysis in the context of internal dosimetry. A set of urine samples (volume: 500 mL) was spiked with known quantities of 239Pu, ranging from 2 to 120 fg (4.6 μBq–0.3 mBq), employing 14 pg (2.05 mBq) of 242Pu as internal standard. The Pu was purified by ion-chromatography using BioRad AG1X2 anion-exchange resins (Bio-Rad Laboratories Inc.). The chemical yield was determined by alpha-spectrometry, being about 80%. Afterwards, the planchets so obtained were leached with diluted HNO3 and the dissolved plutonium was determined by Accelerator Mass Spectrometry (AMS) at the Centro Nacional de Aceleradores (CNA) in Seville, Spain. The minimum detectable activity (MDA) for the AMS measurements was determined through the study of a set of procedural blanks, giving figures of about 0.44 fg (∼1 μBq) per sample. This contrasts with the MDA obtained by AS for the same set of samples, of about 50 fg (∼0.1 mBq). The results now presented helps to demonstrate that the routine measurement of 239Pu at ultra trace levels in human urine samples is possible with the new-generation of compact AMS systems, offering a highly sensitive method for the reassessing of planchets prepared for bioassay purposes.