Determination of the radioactive material and plutonium holdup in ducts and piping in the 324 Building

This report describes the measurements Performed to determine the radionuclide content and mass of plutonium in exposed ducts, filters, and piping in the 324 Building at the US Department of Energy Hanford Site in Washington State. This information is needed to characterize facility radiation levels, to verify compliance with criticality safety specifications, and to allow more accurate nuclear material control using nondestructive assay (NDA) methods. Gamma assay techniques typically employed for NDA analysis were used to determine the gamma-emitting isotopes in the ducts, filters, and piping. Passive neutron counting was selected to estimate -the plutonium content because high gamma levels from fission and activation products effectively mask any gamma emissions from plutonium. A high-purity gamma-ray detector Was used to measure the mixed fission and activation radionuclides. A neutron slab detector containing five 3He proportional counters was used to determine the neutron emission rates and estimate the mass of plutonium present. Both measurement systems followed the methods and procedures routinely used for nuclear waste assay and safeguards measurements