Rapid isotopic analysis of uranium, plutonium, and americium in post-detonation debris simulants by RIMS

Abstract

We demonstrate rapid isotopic analysis of trace U, Pu, and Am in solid basalt matrices using resonance ionization mass spectrometry (RIMS). The samples were intended to mimic post-detonation debris from a nuclear explosion, in which material from the device is intimately mixed with entrained material from the environment. Complete isotopic analysis of materials containing ppm to ppb levels of the actinides was done without separating them from the host matrix, and consumed <100 ng of sample. Measured isotopic compositions of U, Pu, and Am were accurate to ≤10% for most isotope ratios except ²³⁸Pu, which was compromised by low concentration and excesses of ²³⁸U up to 34 000 : 1. A new method called “blinking” that takes advantage of the singular ability of RIMS to quantify backgrounds from all sources rapidly and accurately was developed for the analysis of ²³⁸Pu. Using the blinking method we accurately measured the ²³⁸Pu/²³⁹Pu ratio on a sample containing 1.4 × 10⁶ atoms of ²³⁸Pu at a concentration of 0.1 ppb in the host material.