Chemical Assay of Plutonium for Safeguards

The chemical measurement of plutonium in nuclear fuel cycle materials ranges from highly precise titrimetric methods applied to homogeneous products to less precise methods applied to heterogeneous scrap materials. A system under development for analyzing scrap materials involves a combination of high-temperature pressurized acid-dissolution attack, a gamma assay for low levels of plutonium in any resulting residue, and an automated spectrophotometer for measuring plutonium in the liquid fraction. A review of chemical standards, that are essential for calibrating methods to maintain unbiased plutonium-assay measurements, indicates that a greater variety is needed for application to nuclear safeguards materials.