Fukushima Reactor Temperature Surpasses 752 Degrees … More Than 4 Times Maximum for “Cold Shutdown”

Over 400 Degrees Celsius

Pretending that the Fukushima reactors achieved a state of “cold shutdown” was a political – rather than scientific – decision.

Tepco itself said the state of cold shutdown could only continue so long as the temperature within the nuclear reactors stayed below 100 degrees Celsius. (Because the thermometers within the reactors have a 20 degree margin of error, Tepco says that any reading over 80 degrees violates the conditions for a cold shutdown.)

As Bloomberg notes today:

Tokyo Electric Power Co. said the temperature in one of the damaged reactors at its Fukushima nuclear station rose to levels above safety limits even as it injected increased amounts of cooling water.

One of three thermometers indicated the temperature at the bottom of the No. 2 reactor pressure vessel rose to 93.7 degrees Celsius (200.7 Fahrenheit) today, higher than the 80 degrees limit, Ai Tanaka, a spokeswoman for the utility known as Tepco, said by phone today.


The thermometers have a margin of error of as much as 20 degrees.

But major Japanese news sources Yomiuri and Jiji note that the thermometer in reactor 2 has since climbed to 272.8 degrees Celsius, and then hit the upper limit of the thermometer at 400 degrees Celsius (752 degrees Fahrenheit).

In other words, the thermometer is showing temperatures more than 4 times higher than the 100 degree Celsius limit for cold shutdown.

Tepco claims that such a high reading means that the thermometer must be broken, and is maintaining its declaration of cold shutdown based upon the reading of other thermometers. Of course, the fuel is moving around, so there could be hot spots and cooler spots within each reactor.

Of course, Tepco could be right: the thermometer could be broken. But I am not yet convinced, given that – ever since the earthquake last year – Tepco has repeatedly claimed that an instrument is broken whenever there is a new reading of things gone haywire. (Indeed, one Japanese writer said that Tepco’s spokesman sounded “testy” when asked how Tepco knew that the thermometer was broken.)

In good news, a second, nearby 4-reactor nuclear complex which almost melted down last March – the Fukushima Daini complex (referred to as the Fukushima “2” complex), which is 7 miles away from the infamous, leaking 6-reactor Fukushima Daiichi complex – apparently is in a true state of cold shutdown.

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  • cr

    Ok, so how hard would it be to put a NEW thermometer into the failed reactor?
    It couldn’t be that expensive…and it is a critical thing to have working!…nah

    • Well…it wouldn’t be hard at all if you didn’t mind dying from radiation poisoning a few days later…

      BUT: why hasn’t Sony reprogrammed that violin/stairclimbing robot to get in there and hold a cooling hose or something? They have the fanciest robots of all yet are standing around looking at their shoes…

      • Its too radioactive for the robots and they quickly become radioactive robot > my understanding

        • Better them Sonybots than us – ‘We’ can always make extra Sonybots

  • Lili

    Cr how would you suggest they brave those temperatures in a failing reactor site filled with nuclear fuel to install a single thermometer? They can possibly put in a robot but at those temperatures how are they going to get it close enough?

    One explosion and there will be a chain reaction throughout all of Japan. I hope people remember that these “volcanic” islands sit on unstable tectonic plates. Huge nuclear explosions tend to agitate plate activity.

  • angryinadk

    I do believe that the robots cannot operate in high ionizing radiation environments.

  • Mbert

    The radiation will kill anyone that goes in to replace it, and Sony’s robots aren’t “hardened” for radiation. I don’t know why they haven’t hardened one yet, or have the military’s hardened robots go in there to do some work (I know the US, japan’s ally, has these robots.)
    Reactor cores exploding really aren’t huge nuclear explosions. Just look at the one you can find on the net of it exploding early on. Check “fukushima hydrogen explosion” but that’s no hydrogen explosion, look at what some explosive analysts have to say. Its kinda like you know you can just take 2 peices of uranium of sufficient size and just drop one on the other from about 6 feet and it will explode. It will be pretty wimpy though, why do you think “little boy” weighed like 2000 pounds? you need to keep the nuclear material supercritical for as long as possible for it to really go boom, usually by using explosives around the mass.
    Big question is why hasn’t a larger effort been put forth to deal with the problems? By now there should be some of those radiation hardened robots in there. There should be a better system to take care of the radioactive runoff water. Browns gas can nearly eliminate some of the radioactive products. There are also a few novel ways and materials people have proposed that should mitigate the effects of this meltdown. There is no funding for them. The entities in control of billions, be it government or corporations, really have no interest in taking care of this problem.

    • “Browns gas can nearly eliminate some of the radioactive products.”

      I’m eager to learn how this might be so (but a smidgen dubious).

  • Will

    It’s probably just a ground. A nuclear explosion cannot happen in this type of reactor.

  • dasmonde

    The “4 times higher” bit is meaningless: the ratio is 4 in Celsius but 3.55 in Fahrenheit. Consider if the limit were zero Celsius… The only meaningful ratio is in Kelvin, which is about 1.106.