A hole was drilled in the #2 reactor containment vessel for insertion of an industrial endoscopy camera on January 19th, revealing high gamma radiation, no water level or evidence of corium, and a steady dripping of water through the breached reactor vessel. Which was reported to have "melted through" in the early days of the mid-March 2011 disaster.
Today the "0" level gage at unit-2 is still hovering around 250ºC, after having gone as high as 275.9ºC on Monday. TEPCO has been issuing reassuring statements that they 'think' the gage is broken because two other temperature gages in the vessel aren't reading that high, although at least one of them has behaved as irregularly as the "0" gage has. TEPCO employees at the site say they doubt the gage is actually broken, and have increased the water being added to the vessel as well as injected boron to help prevent criticality. Analysts have suggested that recent changes in the coolant flow due to changes made when the endoscopy was done may have affected the amount of water reaching the molten corium (wherever it may be), causing it to crack or shift, thus possibly going critical again for short periods to cause the temperature rise. Also over the weekend [Feb. 11 & 12] cesium levels measured around unit 2 jumped from single digits to 98.2 MBq/km2 for Cesium 134 and 139 MBq/km2 for Cesium 137.