Fukushima unit 2 liquification of uranium core. never seen before in history of nuclear power

ENEnews ^ | ENEnews

[yank in the UK]

Unit 2 we now know completely liquified. We’ve never seen this before in the history of nuclear power. A 100% liquification of a uranium core.

[justa-hairyape]

Sorry about getting the terminology incorrect. Really do not care much about TMI. It is ancient history and I was just typing off the top of my head.

Do you see what I did in the above paragraph ? I apologized for being wrong about something. The terminology. You might want to remember that.

Sorry, but you are just flat out wrong about there not being bottom penetrations in the TMI vessel. There were 52 penetrations. Go to post 108. Read that article linked there. It has a section on TMI along with schematics showing the bottom penetrations. Here is the relevant extract.

2. BOTTOM HEAD PENETRATION EXPERIENCE AT THREE MILE ISLAND
The Three Mile Island (TMI) Unit 2 reactor vessel bottom head penetrations accommodate the PWR instrument guide tubes as indicated in Fig. 3. The portion of the penetration nozzle passing through the vessel wall is schedule 160 pipe with internal diameter 0.614 inch (1.56 cm) and wall thickness 0.218 inch (0.554 cm). The tube wall thickness within the reactor vessel adjacent to the wall is 0.693 inch (1.76 cm). There are 52 such penetrations in the vessel bottom head. Post-accident wire probing of 17 of the TMI-2 bottom-entry instrument penetration tubes revealed 16 of these to be blocked at points outside the reactor vessel.1 Entry of debris into the penetration tubes must have been by ablation of the in-vessel portion of the penetration nozzle, as indicated in Fig. 4.2 .

[NVDave]

Yes, I know that.

Still not concerned.

NB: It has come out in the fullness of time that Naoto Kan (former PM of Japan) was less than no help to TEPCO in the days after the tsunami. There’s a reason why the Diet was going to remove him...

That said, God smiles upon little children, drunks and America, and while we would be in a world of crap with a similar incident with Obama at the helm, the ability and habit of Americans to not wait for central command/control authority before doing the right thing would make the big difference in the outcomes.

There’s almost no technical issue that can’t be made worse by politicians. There is also no technology that can’t be screwed up by a politician. Kan and TEPCO management took an already bad problem and made it MUCH worse than it needed to be.

[UCANSEE2]

That is probably the most ignorant, scaremongering and flat-@$$3d WRONG statement made on FR in many a year.

Well... first off you must not have noticed my tagline.

Secondly, How many nuclear weapons have we detonated UNDERGROUND, and how many have melted their way to the core of the Earth? Why hasn't the radioactivity from all those detonations poisoned all the water supplies?

Since there is a giant layer of MOLTEN MAGMA under the crust, wouldn't the radioactive material dissolve into the magma and have about as much effect as pissing in the ocean?

[TXnMA]

Does your tagline apply to #163, as well? '-) Must be nice to have a "gimmick" that lets you (IYOSO) post whatever you like -- and then back out later... ;-}

Apparently, you believe that the "China Syndrome" scenario is BS. We agree.

FWIW, nuclear explosions disintegrate the reactive mass; there is no "blob" left to travel... BTW, if you've never "traveled to our NTS via Google Earth, you will probably appreciate the image I posted in my #96...

And, dilution by dissolved crust (see "sand", "corium". and "Chernobyl") would shut down any "blob" long before it reached the "Moho". ("Mohorovičić discontinuity" -- crust-mantle interface...)

~~~~~~~~~~

"China Syndrome"? As worthless as Hanoi Jane's conservative credentials...

[Ditto]

Bottom line - a seal on the bottom of the RPV broke at TMI.

No it didn't. The melted core ate away at the bottom mounted in-core instrumentation guides that extend a foot or so up into the vessel, but it never exited to pressure vessel, never ate through and welds, 'stainless steel' or otherwise, and never violated the primary pressure boundary.

FYI... all the welds in a pressure vessel are on high strength carbon steel. The stainless steel inside nuclear vessels is a corrosion resistant cladding applied over top of the carbon steel. It is not intended to be part of the pressure boundary. It is just a cladding to resist corrosion and keep contamination to a minimum.

The Reactor Pressure Vessel (RPV) did not 'break,'. The pressure boundary was never violated. All of the fuel was contained inside the RPV. None of it exited. Zero.

[justa-hairyape]

See post 161. Technically corium debri broke intro areas it was not supposed to break into. Did not technccally leave the RPV assembly, but technically it left the original RPV bare steel housing. That is because it ate into the instrument tubes. So 16 out of 17 tubes is 94 % failure rate for the penetration nozzles.

BTW - Check out the leftist article linked below. Amazing history if true. Explains how we got here after WWII. Published by some website run by DC leftist heavy hitters.

United States Circumvented Laws To Help Japan Accumulate Tons of Plutonium

[Ditto]

From your post #161

Entry of debris into the penetration tubes must have been by ablation of the in-vessel portion of the penetration nozzle, as indicated in Fig. 4.2 .

From INEL who did all the testing: Results of examinations of pressure vessel samples and instrument nozzles from the TMI-2 lower head

15 prism-shaped steel samples were removed from the lower head of the damaged Three Mile Island Unit 2 (TMI-2) nuclear reactor pressure vessel to assess the effects of approximately 19 tonne of molten core debris that had relocated there during the 1979 loss-of-coolant accident.

Metallographic examinations of the samples revealed that inside-surface temperatures of 800–1100°C were attained during the accident, in an elliptical ‘hot spot’ with dimensions of about 1 m × 0.8 m. Tensile, creep and Charpy V-notch specimens were cut from the samples to assess the mechanical properties of the lower head material at temperatures up to the peak accident temperature. These properties were used in a margin-to-failure analysis of the lower head.

Examinations of instrument nozzles removed from the lower head region assisted in defining the relocation scenario of the molten core debris and showed that the lower head was largely protected from catastrophic failure by a solidified layer below the molten core debris that acted as a partial thermal insulator.

Bottom line... no welds were melted through as you stated above. The damaged instrumentation tubing (not control rods as you first stated) plugged itself via "ablation" (they melted in on themselves) of the in-vessel portion of the penetration nozzle.

No core material ever left that vessel. To say otherwise is not accurate.

I don't care what you think of nuclear, but please keep your facts straight.

[justa-hairyape]

The abalation was not the point. That was just the dumb luck that saved a large area of Pennsylvania. The point was that over 90 % of the instrument tubes were found to contain corium debris. That means the corium was on its way out of the vessel with nothing to stop it except for the fact that it stopped on its own accord. This stuff stops when it wants to stop. Not when some nuclear engineer thinks it will stop.

[Ditto]

The point was that over 90 % of the instrument tubes were found to contain corium debris.

No they weren't. They were found to have melted in on themselves. No corium entered them.

[BigFinn]

Well, it seems it's time to go back to sleep and as one poster put it, crack open your neighbor's skull and feast on the goo... don't worry... be happy... move along... nothing to see here.

There's a bit more to the story. The severely damaged #4 reactor building is tettering with an above ground spent fuel pool on the upper floor with 1,500 fuel rods in it. Another large earthquake. it tooples and who knows what will happen? God help us. Life as we know it will... will not be as we know it.

And I quote, "Men's hearts failing them for fear, and for looking after those things which are coming on the earth...