This document describes the procedures to prepare plutonium sources and to measure the activity ratio of ²³⁸Pu to (²³⁹Pu + ²⁴⁰Pu) by alpha spectrometry. The alpha spectrometry method is used for the determination of isotopic abundance of ²³⁸Pu in combination with isotope-amount ratios determined by mass spectrometry after a preliminary separation of plutonium from uranium and fission products which eliminates the possible isobaric interferences of ²³⁸U in the latter method. It is applied to the analysis of purified solutions of plutonium in 2 mol/l to 4 mol/l of nitric acid containing 50 µg to 200 µg of plutonium per millilitre, as can result from the chemical treatment and purification preceding plutonium isotopic analysis by mass spectrometry.

This document is applied to plutonium solutions free from ²⁴¹Am and those containing less than 10 % of other non-volatile impurities relative to the plutonium content. Otherwise purification is carried out in accordance with ISO 8299.

The methods provided in this document are intended for use in conjunction or in parallel with mass spectrometry for the isotopic analysis of plutonium in spent-fuel solutions or nuclear-grade plutonium products.