Posted on 02/07/2012 5:36:50 AM PST by TigerLikesRooster
Temperature remains high at damaged reactor
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.
Tuesday, February 07, 2012 13:05 +0900 (JST)
P!
You take tons of water, with the requisite inclusion of some Deuterium and a small amount of Tritum, and you pump it into this mass in an attempt to cool it, and you get a surprising increase in temperature!
Is this a joke?
That's basically what you do in a few milliseconds in your typical friendly neighborhood hydrogen bomb.
It's more of a joke when a non-physicist tries to explain how something like a thermonuclear devices works.
The general outline of the fission-fusion bomb has been out there for quite a long time. The details may be missing, but we currently have SEVERAL nations with sufficient knowledge of that process to have made successful bombs.
BTW, it's an ENGINEERING PROBLEM. Most of the physics was worked out and published back in the 1930s.
Modern weapons use a three-stage fission-fusion-fission process.
BTW, it's an ENGINEERING PROBLEM. Most of the physics was worked out and published back in the 1930s.
No, the physics of the "classical Super" were suggested by Teller and others during the Manhattan Project. The 1930s was basic research into the fission process, measuring cross-sections, etc. There was insufficient data on cross-sections to suggest that even a fission weapon was possible until the early 1940s.
What makes modern thermonuclear weapons possible is the concept of radiation implosion. Teller signed off on the first definitive study of the physics of this process, also known as the Teller-Ulam method, in the LAMS-1230 report of April, 1951. It took about a year to implement, but even Ivy Mike in Nov. 1952 was still a kind of physics test since it used liquid deuterium instead of the lithium deuteride which forms the "fuel" in contemporary staged thermonuclear weapons.
But those were uninformed opinions ~ the physicists had long known the probability of that was very small so they forged ahead with the engineering part.
What you have here is something UNEXPECTED by the current hot-nukes guys. All they're doing is running a large volume of water (into a nuclear pile) and doing that repeatedly! Or, maybe they're just dumping it into the ocean. Do you actually know what these yahoos are doing?
Has anyone done it quite this way before? Isn't there a reason nuclear power plants use fuel that's packed in discrete amounts in precisely measured containers?
Where to begin? Well, anyway, here goes...
So, you have a bunch of fissionable material ...
The fuel in a LWR is not "fissionable", it is fissile. It undergoes fission by absorption of a thermal neutron. Fissionable material is typically classified as something that requires a high-energy neutron to induce fission.
...sitting there fissioning away,
Other than spontaneous fission and perhaps a very small amount of subcritical neutron multiplication, there is no credible evidence of ongoing criticality in any of these reactors.
... and no longer contained within its stainless steel fuel housings
Fuel in a LWR is not contained in stainless steel. The cladding of fuel rods is zircalloy.
~ at a low rate of course ~ but it's still fissioning.
See comment above.
You take tons of water, with the requisite inclusion of some Deuterium and a small amount of Tritum, and you pump it into this mass in an attempt to cool it, and you get a surprising increase in temperature!
Far too little deuterium and tritium and in far too dilute a form to be significant for any fusion-type reactions. You need a plutonium trigger fission bomb to have sufficient energy to initiate any kind of fusion reaction. Try as you might, you are not going to get a fission detonation from any kind of LWR core, no matter how badly you damage it.
That's basically what you do in a few milliseconds in your typical friendly neighborhood hydrogen bomb.
Silly descriptors (friendly neighborhood) aside, you need far more to make a thermonuclear explosion than just bringing together uranium, plutonium, deuterium, and tritium. And the reactions in a thermonuclear detonation occur on a time scale of nanoseconds, not milliseconds. If it were milliseconds, there would be a yield comparable to chemical explosives. It is the release of a lot of energy over a very short time scale that makes for a big bang.
The first thing you need is a plutonium fission bomb. You don't have that in a LWR. Plutonium is preferred (weapons-grade, not reactor fuel grade, there is a BIG difference) because it has a higher reproduction factor than uranium. You need specially-designed tampers and "pushers", you need specially-machined radiation channels for directing the energy from the fission weapon (primary x-rays), you need a significant quantity of thermonuclear fuel, either liquid deuterium (as in Ivy Mike) or lithium deuteride. You need a pure plutonium (again, weapons-grade, not reactor fuel grade) embedded in the thermonuclear fuel. Happenstance in a damaged LWR core isn't going to produce these things, and certainly not in the form needed to initiate any kind of significant thermonuclear activity.
Thank you for sharing your knowledge. Would you please sum up the risks and options for recovering a safe state in these damaged reactors?
I love it ~ you did the perfect job on deriving the correct answer (from the perspective of the hot nukes school of thought).
I'm sure the fella's at Fukushima are going to be so happy to hear it's just their imagination.
So, regarding the "zircalloy" containers ~ when they're all busted up and this stuff is just lying about being fissile, why are you pouring water on it? Like I asked, did anybody ever try this trick out before?
Yes. And they are not yahoos. They are good people doing the best they can in a difficult situation in a land that was devastated by a natural disaster. They are doing what the article said, using light water to remove heat from a material that still has a decay heat load.
And THAT IS ALL we are dealing with here. Decay heat. The materials generating the decay heat are in a geometry that is not precisely known. That makes heat transfer a difficult proposition, and modeling of the heat transfer process even more difficult. As to the temperature rise, it is explainable with much simpler and more probable mechanisms than fusion reactions. My guess (speculation, which is something generally frowned upon, but since you asked, I'll give it an honest try) is that something shifted in the cooling mass, a heat removal pathway that was previously open because blocked by debris, or perhaps vapor pressure built up enough to prevent coolant flow through an area previously receiving coolant. You see this happen all the time in other, more familiar examples. Just yesterday evening the logs in our fireplace shifted positions a little as they burned down, causing a slight increase in the radiant heat outflow. Until someone can get a visual inspection of the damaged cores, we won't known precisely what the geometry of the materials really is.
No, I never said that. I very patiently explained the physics of why there was no thermonuclear reaction occurring, which is what you suggested as a heat source.
Sure, it was done after the damage to the TMI-2 core. You need more than randomly distributed fissile material and light water to initiate a fission reaction (other than spontaneous fission, which you're going to get anyway). Read up on reactor theory and the criticality equation and get back to us.
The light water is being used for heat transfer. The goal is to remove the decay heat from the materials in order to develop a plan for, first, inspecting the damaged systems, and, second, to come up with a way of recovering the materials in a way that will allow either restoration or decommissioning of the facility (TBD).
I have no fear that any more radionuclides are going to be expelled than there ever were ~ that part of the science is certainly settled, eh! It ain't gonna' blow up, but the fellows running the show (presumably all highly trained physicists and atomic power plant engineers and designers) said the heat increase wasn't explainable.
Thank you. It will be a long process. The methodology is pretty well known. It will have to be implemented slowly. I am very confident the necessary operations can be conducted with essentially no risk to the general public. I am reasonably confident the people doing the work will be adequately protected, although their risk will be higher than the public due to proximity and handling of the damaged materials.
The first steps will be a visual inspection of the damaged cores to see precisely what we are dealing with. The experience we had with the TMI-2 core damage gives us a pretty good experience base as to what to expect from damaged LWR fuel (which is different than the Chornobil core). If any of it got out of the pressure vessel (if it did it likely exited through the instrument tube penetrations at the bottom of the vessel) then there will have to be a process implemented to remove that material from the containment structure.
Long-term, I don't know. It will depend on the extent of the damage. If the pressure vessels were significantly damaged, there is probably no other option than dismantling the facility. That does not mean the site could not be re-used for a power plant, but the existing structures would have to be removed.
Thank you.
The electroweak interaction is a unification between the electromagnetic and weak nuclear forces. This unification does not occur until particle interaction energies are in the range of 100 GeV, the so-called unification energy. This energy is generally not available in natural reactions except just after the Big Bang. You can get it in high energy particle accelerators, but not fission or fusion reactions. Uranium or plutonium fission releases total energy in the range of 200 MeV (MeV, not GeV). Common fusion reactions (D-D, or D-T) release energies in the range of 25 MeV per reaction. Nowhere near those needed for electroweak interactions to occur.
I have no fear that any more radionuclides are going to be expelled than there ever were ~ that part of the science is certainly settled, eh! It ain't gonna' blow up, but the fellows running the show (presumably all highly trained physicists and atomic power plant engineers and designers) said the heat increase wasn't explainable.
I think it is explainable using convention heat transfer theory, as I noted previously.
Certainly some of the red-hot radioactive waste with short half-lives has to be doing something.
A poster up the line noted that when the Japanese point to a problem they're probably trying to hide a worse problem. No doubt we will all find out what that is over the next few months.
I think maybe what they were saying was that they were not sure of what was causing it, or even certain it was occurring. Remember that they said they had three "thermometers" (really thermocouples) monitoring the temperature inside the pressure vessel, one showed an increase, the others didn't. That raises the question of an instrumentation problem with the one thermocouple. If it was a legitimate reading, the mechanism for the increase could be any number of things that are explainable by conventional heat transfer effects, things like blocked flow, buildup of vapor (which can inhibit conductive heat transfer), shifting of the heat-generating mass, deposition of insulating materials (debris) from the coolant flow, etc.
We all must admit it’s going to be very difficult to get someone to go in there and check eh!
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