Core layout of the fast spectrum reactor for LLFP transmutation. Plan view and side view of the core layout of the fast spectrum reactor with numbers and lengths of assemblies and pins in the core and radial blanket region. For the transmutations of Cs and Zr, the pellets were loaded along the full length of the radial blanket assembly, whereas the pellets were loaded at the core height of the radial blanket assembly for Se, Tc, Pd, and I. The shield region was used for the transmutations of Cs and Zr, but they were loaded only at the core height of the shield assembly. Unless the shield region is used for the transmutation, the shielding assemblies surround the core and radial blanket assemblies to shield neutrons and gamma rays from the reactor vessel.