Japan: Temperature remains high at damaged reactor(despite injection of more water)

An unknown rise in temperature at one of the reactors at the damaged Fukushima nuclear plant is troubling its operator. Tokyo Electric says the temperature hasn't gone down even after it increased the volume of cooling water on Tuesday.

One of the thermometers at the bottom of reactor No. 2 at the Fukushima Daiichi plant gradually rose to about 70 degrees Celsius since January 27th. It had stayed around 45 degrees before.

In an effort to lower the temperature, the operator increased the amount of water sprayed on the nuclear fuel by 3 tons to 13.5 tons per hour Tuesday morning.

But Tokyo Electric said readings were down only about 3 degrees after some 5 hours of operation, hardly showing signs of improvement.

The utility said the flow of water in the reactor may have changed after plumbing work in late January, causing difficulties in cooling part of the melted nuclear fuel.

It added that no temperature rise has been observed at 2 other thermometers in the same reactor and that it will continue to carefully monitor the reactor.

TEPCO has been unable to visually confirm conditions inside the reactors since the nuclear disaster last March because of high radiation.

First year calculus students weren't, in fact, predicting rogue waves, particularly not when everyone in authority agreed they didn't exist, and Fur Shur, I didn't do that at the time, nor even into subsequent years.

Yet, they existed.

The probability of such a wave occurring is a higher order problem than is readily dealt with through mere reference to calculus. First, you have to believe they exist

Latest speculation is that more of the fuel in #2 melted down, probably due to the plumbing changes. Reactor #2 was only reported to be about 50-60 % melted. They cannot rely on temperature guages alone. Those guages have been off by 20 C historically in this situation. There is a lot of smoke coming out of the reactor, which leads many to believe the temperature is probably closer to 85 C.

The reason they injected boric acid as a precaution was due to very low traces of fission products.

Well, you’re getting into areas of philosophy (beliefs), and that is moving outside of the realm of the questions that physics addresses. If you want to go in that direction, it is something I am reluctant to comment on in a thread that really began as a technical discussion.

Here is the latest I have on the NEI newsfeed:

"Tepco was able to discount recriticality as a potential cause of the temperature rise after conducting an analysis of charcoal filters in the containment gas control system. These showed very low traces of fission products that were below the threshold that would indicate criticality. Nevertheless Tepco this morning injected boric acid into the reactor vessel as a precaution and increased the core spray injection rate by three cubic metres per hour."

The overall core temperature remains within the limits specified for cold shutdown (less than 100 deg. C.).

The correct wording from TEPCO, I believe was that they were injecting boric acid to prevent the increase in the non-measurable fission products. You have to pay very close attention to how they word things, unfortunately.

Here is how the nuclear industry is reporting the situation.

Tepco was able to discount recriticality as a potential cause of the temperature rise after conducting an analysis of charcoal filters in the containment gas control system. These showed very low traces of fission products that were below the threshold that would indicate criticality. Nevertheless Tepco this morning injected boric acid into the reactor vessel as a precaution and increased the core spray injection rate by three cubic metres per hour.

Stabilisation after Fukushima cooling change

So it was not no detectable fission products. Again, you always need to know the limits of detection for every Tepco reported value. It was measured fission products that were determined to be below the thresholds that would indicate fission. Now how they determine the thresholds for an unknown situation is beyond me. And that is probably why they added the boric acid.

Oops. Just noted that was your exact quote. Mine has a source link. So my problem with the nuclear industry, ever since Fukushima has gone boom, is with the obfuscation about the facts. If they knew without a doubt, that there was no fission levels to worry about, they would not have added boric acid.

If they knew without a doubt, that there was no fission levels to worry about, they would not have added boric acid.

It was stated that it was done as a precaution. What is the reason for the precaution? Probably two reasons, one technical, the other political. The technical reason is that if there is material shifting around, it can change the geometry in ways that are not fully characterized. One of the principles of criticality safety is to go the extra mile to assure that you have inserted negative reactivity to offset any possible increase in reactivity as a result of the geometry change. The political reason is that if they didn't do it, the anti-nuke kooks would accuse them of not taking proper precautions.

Once the new geometry has stabilized, they will likely reduce the boric acid concentration gradually and check to be sure criticality is not being approached. That is a very straightforward reactor physics measurement involving subcritical multiplication. One of the classes I teach does the very same measurement, not by boron concentration but by control rod positions. It is called incremental approach to critical. You get extremely precise measurements of critical rod position. Same deal with born concentration.

Can understand that, but it has been reported that they ended up adding 1,094 Kg of boric acid. More then they originally estimated would be required. That does not seem to be a well calculated preventative maintenance procedure done partially for show.

1094 sounds like a lot of mass, but you have to remember basic chemistry and physics. First, remember that the chemical formula for boric acid is H3BO3. That means that only 18% of the weight of the molecule is boron. Next, remember that only 20% of the boron is of the strongly neutron-absorbing form, 10B. That means of the total 1094 kg of boric acid, about 3.5% of that mass, or about 38 kg, was of a form that strongly absorbs neutrons. When you consider the volume of the pressure vessel, or even the volume of the mass they are trying to affect, 38 kg of material spread over that isn't a terribly large amount. If it was more than originally expected, my guess is they wanted to be conservative on the chance that some of the water carrying the material might evaporate or be diverted through the complex geometry without reaching all of the places they wanted it to get to if they used less.

Now, as Obamalamadingdong would say, here we have a teachable moment. We are better if we first consider the science and run the numbers before we jump to emotional conclusions (1094 kilograms is a lot of mass, more than they expected, therefore they must be lying, putting on a show). While doing so may be emotionally satisfying because it validates a personal prejudice, it can lead you away from the truth.

Would huge ice cubes work at cooling better than water? Just wondering....

Very good. You are correct. Ice, as it melts, absorbs more heat because you are taking advantage of the phase change. This is called latent heat of fusion, and involves the concepts of enthalpy of fusion and latent heat. For ice, the heat of fusion is about 334 kJ/kg. Whatever the heat source is that melts the ice "gives up" 334 kJ of thermal energy to melt 1 kg of ice. That makes whatever is supplying the energy cooler.

In this case, they wanted to transport coolant through a structure with complex geometry, so liquid was the best choice. Large chunks of ice would have a hard time being transported through small channels and openings.

You can get added heat removal through the phase change from liquid to vapor. This is called the latent heat of evaporation. It is the principle upon which cooling towers work. The steam you see coming out of a cooling tower is removing heat from the power plant through this process. BTW, in a nuclear plant, the steam coming from a cooling tower isn't from the reactor. The coolant running through the cooling tower is from the condenser recirculating loop. What is being evaporated is from the heat sink, typically a lake (natural or man-made).

;O0 After your first 2 words *very good*, I had to pause and then read the rest of your post....I love to be called *very good* :O) just a little pride you know....LOL thank you for your reply....you also are very good even I can understand it....:O)

It's still a technical thread. The discussion slid over to a real problem with mathematics that almost always appears to be theoretical to engineers or even, as you noted, philosophical to physicists.

We currently have a runaway situation in math ~ we have found it can describe conditions in some detail in universes/realities beyond our own. What that does instantly is substantially discount the future utility of math in predicting anything at all!

My point was math hadn't predicted Rogue Waves. However, once we had some mathematicians who believed Rogue Waves were possible, they came up with predictive mathematics ~ with a distinct quantum mechanical point of view.

Rogue Waves are still "Rogue Waves" that just pop up out of an assortment of other smaller waves ~ because they can. Which raises the question ~ what do you really think the Japanese are trying to hide at that reactor?

I don't know, you're getting into areas I don't feel qualified commenting on as I have seen nothing like it in the physics I have been taught or the journals I read (things like IEEE Spectrum, Physical Review, American Scientist, Nuclear News, Health Physics, etc.). As far as anything being “hidden” at the Japanese reactors, I have no proof that anything is being hidden, all I have is what I read in the public record and what people I know in the industry and elsewhere have told me (e.g., people I know at DoE, NRC, and others). I have not been to the site myself, nor do I have plans to go there, so I cannot claim any first-hand knowledge of what is going on. But nothing I have read or heard leads me to think there is any kind of deep, dark, sinister conspiracy. Yes, there has been a lot of confusion, speculation, misunderstandings, and in some cases technical errors. But I don't see anyone sinister behind the curtain manipulating and/or coordinating it all. All I can do is work with the information I have, run the numbers, try to keep a cool head, and apply the scientific knowledge and experience I have from four years of college, five years of graduate school, and 32 years in the business.

There is a big hole in the bottom of the RPV. They estimate only up to 50 % of the fuel remains in the RPV. The rest is boring into the concrete below if we are still lucky. We do not even know if the measured fission products were from the mass boring into the concrete or the mass still up in the RPV. The temperature sensor is up in the RPV. The position of the temperature sensor does happen to be near the side where they tried to look at the outside of the RPV. Some speculate that part of the melted mass could have slumped toward that wall of the RPV and might still be there or melted through the side in addition to the main mass melting out the bottom. All unknowns at this point in time.

Fukushima got a little shaker today. 4.2 on the Japanese scale. Caused some shaking at the plant. JNN camera has been done with an error since about then.

Do you have pictures of that? Is it fact or speculation? The data I have seen indicates that the most likely exit points from the PV are the instrument tube penetrations, which are not terribly large in size, but there are a fair number of them. The heat load calculation that was done at both NRC and INL indicates that if the entire core mass ended up in the containment sump the concrete degradation would be on the order of a few inches out of the six feet of thickness of the containment structure. There is additional concrete below the containment in the form of the basemat and concrete embedment. Based on the drawings I have from GE, this added thickness seems to be about 18 feet. It forms the foundation of the entire building, so it is quite a thick slab. These are calculations, not actual measurements since no one has been in there.

Aftershocks in a region that experienced a major seismic event are not uncommon. What was the result of that 4.2 other than the camera failure? I have seen nothing on the NEI or IAEA news feeds. If its limited to a camera failure, I won't worry too much about it.

No, I had heard this operation was planned but didn't see any results. Assuming this is authentic, it appears that there are some intact structures, others damaged. I don't see any indications of PV breach. It's hard to tell because an endoscope has a limited depth of field. Those speckles are probably radiation effects. I did an experiment once with a CCD device in a high rad field and it did exactly what you see there. If they did an endoscope inside the PV I would imagine one could be done for the containment. That would tell us how much material got out, if any.

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