Temperature of the Reactor Pressure Vessel of Reactor 2 at Fukushima I Nuclear Power Plant has been rising since February 2. TEPCO will increase the amount of water being injected into the reactor to see if that lowers the temperature.
The temperature at the bottom of the Reactor Pressure Vessel of Reactor 2 was about 52 degrees Celsius on February 2, but it kept rising. As of 5AM on February 5, it was 67.4 degrees Celsius, 15 degrees increase.
On February 5 TEPCO increased the amount of water injected into the reactor from 8.6 tonnes/hour to 9.6 tonnes/hour to see if it lowers the temperature.
TEPCO says it doesn't know what is causing the temperature to rise, but says it doesn't affect the decision of "cold shutdown state".
According to the latest plant parameter data from TEPCO, the temperature at the bottom of the RPV of Reactor 2 at 11AM is 68.6 degrees Celsius, up over 1 degrees from 5AM.
By the way, the temperature at the CRD Housing Upper Part, which went up to 142 degrees on January 14, and dropped down to -197 degrees on January 19, is now back up at 124.7 degrees Celsius ("instrument failure", according to TEPCO):
Here's what TEPCO said in the handout for the press on February 4, 2012:
【Unit 2】19:20 on February 3: To improve reliability of water injection to the reactors, the injection line connecting to the reactor injection pump on the hill was replaced with polyethylene pipes and we have been changing the route for reactor injection from feed water system to reactor core spray system in a stepwise manner. After completion of adjusting water flow amount as planned on February 2, tendency of temperature rise at the bottom of PCV was observed. Thus, we changed the injection amount into Unit 2 reactor through feed water system from 2.9 m3/h to 4.9 m3/h and changed that though reactor core spray system from 5.8 m3/h to 3.8 m3/h . As for the temperature rise, the temperature at the upper head of the bottom of PCV has risen to approx. 67.2 ℃ at the highest (as of 4 pm on February 4: reference), but currently, it is approx. 65.1℃*1 (as of 5 pm on February 4). The trend of the temperature seems to be going flat and we will monitor it continuously.
The worker who tweets from Fukushima I Nuke Plant is more worried about Reactor 2 than Reactor 4.