Year
1975
Abstract
Performance characteristics of three different radioactive source NDA systems are compared for the assay of HTGR fuel rods and stacks of rods. These systems include the fast neutron Sb-Be assay system, the 252cf \"Shuffler,\" and the thermal neutron PAPAS assay system. Studies have been made to determine the perturbation on the measurements from particle size, kernel Th/U ratio, thorium content, and hydrogen content. In addition to the total 23^u determination, the pellet-to-pellet or rod-to-rod uniformity of HTGR fuel rod stacks has been measured by counting the delayed gamma rays with a Nal through-hole in the PAPAS system. These measurements showed that rod substitutions can be detected easily in a fuel stack, and that detailed information is available on the loading variations in a uniform stack. Using a 1.0 mg 25Zcf source, assay rates of 2-4 rods/s are possible, thus facilitating measurement of 1001 of a plant's throughput