Another thermocouple goes kaput on the Reactor 2 Pressure Vessel.
From Jiji Tsushin (4/15/2012):
Reactor 2 Pressure Vessel thermocouple deemed abnormal after jumping 6 degrees Celsius instantly, says TEPCO
TEPCO announced on April 15 that one of the thermocouples installed at the bottom of the Reactor 2 Pressure Vessel at Fukushima I Nuclear Power Plant jumped 6.1 degrees Celsius in an instant on April 14 night. TEPCO investigated, as the rise in temperature was abnormal. The resistance was found to be too high, and on early April 15 TEPCO decided to exclude the thermocouple from the list of instruments that are regularly monitored because there was a doubt on the reliability of the thermocouple.
According to TEPCO, the thermocouple in question is installed on the outer wall of the Reactor Pressure Vessel, about 2.9 meters from the bottom of the RPV. At 9PM on April 14, the temperature suddenly jumped from 53.8 degrees Celsius to 59.9 degrees Celsius. The other thermocouple at the same height but at a different position stayed at about 45 degrees Celsius, showing no marked difference.
So, at this location, there will be only one thermocouple monitoring the temperature. Originally there were three, at the measurement location called "vessel wall above bottom head", but the first one, 69H1, died back in February after shooting up above 250 degrees Celsius. Now the second one has died, which must be 69H2, looking at TEPCO's temperature data on Reactor 2: