Thursday, February 9, 2012

#Fukushima I Nuke Plant Reactor 2 RPV Temperature Remains Near 70 Degrees Celsius Despite Increased Water Injection

70.6 degrees Celsius at 5AM on February 9, 67.9 degrees Celsius twelve hours later at 5PM.

TEPCO's thinking on this: It will go down eventually, someday. (Seriously.)

From TEPCO's reference data sheet on Reactor 2 RPV temperatures as of February 9, from February 8:

Let's review the recent events on Reactor 2, a Boiling Water Reactor with Mark 1 containment designed by GE.

In October last year, Quince the robot was sent on a mission to survey the radiation levels in the reactor building. After going all the way to the top floor and measuring 250 millisieverts/hour, it started the descent, and was stuck somewhere between the 5th floor and the 2nd floor after the communication cable was either severed or disconnected. Now, Quince is on a solo mission somewhere in Reactor 2 building to monitor the effect of radiation on electronic equipment.

On January 14, 2012, out of nowhere the temperature at CRD (control rod) Housing spiked to 142 degrees Celsius, only to be plunged to -197 degrees Celsius 5 days later on January 19. TEPCO announced it was an instrument failure. The temperature there spiked above 130 degrees Celsius again in late January, and since then has been dropping down. As of February 9, it is back down to 70s.

On January 19, TEPCO conducted an endoscopy using the industrial endoscope by Olympus to peek inside the structure called Containment Vessel, inside the reactor building. Dozens of carbon-based workers, having trained on Reactor 5, drilled a hole on the CV, inserted the endoscope, and manipulated the endoscope to get the glimpse of the interior of the CV which still contains the Reactor Pressure Vessel (RPV). TEPCO was hoping to find water at about O.P. (Onahama Peil) 6000, which is about the level of the first floor, 5.3 meters from the bottom of the CV. There was no water at that level. Another peek is not scheduled in the near future.

Needless to say, the thermometers at the bottom of the RPV have not been measuring the temperature of water for a very long time, as everybody knows.

Then in February TEPCO announced that the temperature at the bottom of the RPV had been rising since February 2. TEPCO responded by increasing the amount of water injection to the RPV by 50% (from 9 tonnes/hour to 13.5 tonnes/hour) and adding boric acid. Probably as the result of this 50% increase in water, the Reactor 2 sub-drain pit overflowed.

It's not that hard to imagine the decent increase in the amount of contaminated water to be treated.


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