Nonsoluble Fission Product Residues, Crud, and Fine Chips of Zircaloy Cladding in Headend Process of Nuclear Fuel Reprocessing

Abstract

The amount and behavior of fine suspended particles and sediments in headend process vessels were investigated. Powdery fines of Zircaloy cladding, crud, and nonsoluble fission product (FP) residues were determined to be 5.3, 1.8, and 1.0 kg/ton of spent fuel reprocessed, respectively. The 1.0 kg/ton of nonsoluble FP residues and 1.8 kg/ton of crud were reasonable amounts when compared with those estimated from burnup and amount of spent fuels treated. The 5.3 kg/ton spent fuel reprocessing came from powdery fines of Zircaloy cladding that had been confirmed by chop of unirradiated Zircaloy clad tube. These residues were mostly suspended in a process solution. Particle size of sediments and suspended particles distributed mostly in <0.5-mm size. Most of the particles that arose in the dissolver scarcely settled down and passed through headend process vessels into the high-active liquid waste storage vessel, while some of the particles settled down in succession in process vessels. Uranium and plutonium dissolved well, so that they left little nonsoluble residue. The weight fraction ratio of nonsoluble plutonium to uranium was 0.05% in sediments, which was higher than the value of 0.02% in hulls. It was concluded that uranium continues to dissolve even after settling down into sediments of the dissolver.