Corium is "everything in the reactor melted together". It doesn't have to include the containment vessel. For example, in Chernobyl, the corium didn't include a

Corium is "everything in the reactor melted together". It doesn't have to include the containment vessel. For example, in Chernobyl, the corium didn't include any of the containment vessel, because RBMKs funny have containment vessels. For something this small the proportion of uranium would probably be higher, but it'd still be a radioactive slurry of fuel, decay products, control systems, cooling loop, and internal structural materials.