#Fukushima I Reactor 2: Thermocouples in Containment Vessel Are Acting Up Again

The temperature is either 88 degrees Celsius, or 20 degrees Celsius, depending on which thermocouple you believe.

Or none of the above, and both thermocouples are broken. Given the previous history (from 2012 when one thermocouples after another was failing inside the Containment Vessel of Reactor 2), it is possible that both are broken.

Mainichi Shinbun (4/7/2015) reports:

福島第１原発:２号機格納容器内の温度計が異常な上昇表示

東京電力は７日、福島第１原発２号機格納容器内の温度計が異常値を示したことを明らかにした。

３日午前５時に２０．９度だった温度が同１１時に７０度に急上昇。５日午後５時には８８．５度まで上昇したが、２号機の別の温度計は平常値を示しており、東電は「原子炉の制御に影響はない」として、原因を調べている。

Thermocouple inside the Containment Vessel of Reactor 2 at Fukushima I Nuclear Power Plant shows abnormal rise in temperature

On April 7, TEPCO disclosed that a thermocouple inside the Containment Vessel of Reactor 2 at Fukushima I Nuclear Power Plant showed abnormal temperature.

The temperature was 20.9 degrees Celsius at 5AM on April 3 but it rapidly rose to 70 degrees Celsius at 11AM. On 5PM on April 5 it further rose to 88.5 degrees Celsius. Other thermocouples show normal temperatures. TEPCO says "It does not affect the control of the reactor," and is currently investigating.

Here's the latest temperature parameters for Reactor 2 Containment Vessel from TEPCO's plant parameters page, which omits the particular thermocouple that spiked:

So which thermocouple spiked? It is the thermocouple "supply air D/W cooler(TE-16-114K#1)". There is a site that continues to plot charts from the plant parameter data disclosed by TEPCO, and here's the chart plotting all "supply air D/W cooler" thermocouples:

Looking at the chart, it is more likely that this particular thermocouple broke, and the temperature inside the Containment Vessel remains between 20 and 30 degrees Celsius.

Quickly checking the measuring devices installed inside Reactor 2 (information from TEPCO's site), broken and malfunctioning devices are numerous.

As of July 2014, only 8 thermocouples out of 24 inside Reactor 2 Containment Vessel are monitored in accordance with the safety procedures set by regulatory authorities (meaning only 8 are properly functioning), according to TEPCO's information.

In contrast, 16 thermocouples out of 21 are functioning properly in Reactor 1 Containment Vessel, and all 19 thermocouples are functioning properly in Reactor 3 Containment Vessel.