Initial Results of Fast Active Neutron Coincidence Measurements

We have developed a new Fast Neutron Coincidence Counter (FNCC) that uses an array of BC454/BGO phoswich scintillators to detect neutrons by a combination of proton recoil and boron capture signals. The BC454/BGO phoswich detector has intrinsic advantages of high-detection efficiency and a short die-away time that enable the development of a faster active neutron coincidence counter. A unique feature of the system is that the neutron energy information is preserved and can be used as a method of discrimination to remove counts arising from the AmLi interrogation sources. We are investigating the application of this new technology to the active assay of uranium, where substantial reductions in assay time can be achieved using this discrimination technique. We will describe the new FNCC, the associated data analysis electronics, and the software algorithms used for uranium assay. We will report on the measurement results obtained to date and provide preliminary conclusions on the applicability of the technique to improved uranium inventory verification.