Plutonium age determination from 240Pu/236U ratios in individual particles by ICP-MS without prior chemical separation

The determination of the time (i.e., age) elapsed since the last purification of plutonium with chemical separation gives important information for monitoring nuclear activities related to reprocessing and nuclear weapon production. Although methods for the analysis of plutonium solutions have been extensively studied, few studies were conducted for the measurement of individual particles. In this work, a simple technique was developed for age determination of individual plutonium particles by a combination of single particle dissolution and measurement by inductively coupled plasma mass spectrometry (ICP-MS) without prior chemical separation. The analytical results of individual plutonium particles having an age of 5.98 y indicated that the use of 240Pu/236U ratios allowed for the determination of accurate ages, though that of 238Pu/234U and 239Pu/235U ratios was not suitable because of the contamination of natural uranium during the process of sample preparation. The developed technique is especially useful for the analysis of the samples containing a number of plutonium particles having different ages.