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[Time Stamp: 00:00] In July 1986, after most of the loose debris had been removed, the core stratification sampling project, better known as "Core Bore," was begun.
[Time Stamp: 00:11] A specially modified drilling rig, provided by the Department of Energy, was mounted on top of the reactor vessel, and hollow core drill bits were used to bore into the damaged core.
[Time Stamp: 00:22] From each of ten locations, a drill string, containing a long cross-sectional sample of the core, was extracted and placed into a defueling canister.
[Time Stamp: 00:30] This was later sent to the Department of Energy facilities in Idaho for further study.
[Time Stamp: 00:35] Videotape surveys were then performed in each three and one-half inch diameter hole.
[Time Stamp: 00:40] The middle of the core region was found to be a solid mass of once-molten material that extended as deep as five feet at the center of the core.
[Time Stamp: 00:50] This mass was found to be quite hard and brittle; apparently ceramic in nature.
[Time Stamp: 00:55] Visible in this mass, particularly near the top, were metallic streaks and clumps.
[Time Stamp: 01:00] These apparently were partially melted end fittings and other structural components.
[Time Stamp: 01:05] No significant voids were seen in the ten locations examined.
[Time Stamp: 01:10] At the bottom and sides of this mass, agglomerated material, consisting of fuel rods and pellets, surrounded by once-molten material, was observed.
[Time Stamp: 01:20] This is a transition zone between the once-molten mass and the intact fuel rods and fuel rod stubs.
[Time Stamp: 01:27] Under all of this are stubs of fuel rods.
[Time Stamp: 01:30] They are shiny, indicating they were underwater throughout the accident and not exposed to the oxidizing steam environment.