Astolmar

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Nuclear meltdown

I feel that your latest additions to this article have too much written down the possibility of fuel melt in favour of only the steam-Zircally reaction. My understanding was that a full core melt was still possible and was indeed observed at TMI. Admittedly the physics isn't just a urania melt, since I think there's a U3Ox/ZrOy eutectic which forms and melts out first. But I've been out of this field for nearly a dozen years... Bob aka Linuxlad (talk) 18:28, 27 August 2008 (UTC)

A full meltdown is not possibble and was not observed any meltdown at all. What was observed the end state of an intense zirconium fire in the steam. It carried away a mixture of washed away fuel both at the Chernobyl 4 and TMI 2 accidents which was deposited on the lower elevations forming a (ZR,U)O₂ (relocated core at TMI-2) lava flows at Chernobyl-4.

I'm aware of the misdirecting the investigation toward the so called eutectic - also the limiting the coolant influx in the subsequent investigations and tests; the introduction of the nonsense of steam explosion. I could not idetified the interested in these misrepresentations parties... Aladar Astolmar (talk) 14:25, 2 September 2008 (UTC)

Reference? Bob aka Linuxlad (talk) 17:30, 2 September 2008 (UTC)

I came here to aske the same thing - could you please provide references for your changes to Nuclear meltdown? ·:· Will Beback ·:· 20:11, 2 September 2008 (UTC)

There is one from a list of several, but I insert this here to see (if you follow the link) the difference between the authors description and what is cited as a summary...

"The high-temperature oxidation reaction began at the 2.4- to 3.04-m elevation and formed a localized burn front that moved quickly downward as far as the 1.2-m elevation and then steadily upward. The burn front reached the top end caps (3.80m) and ceased 15 min before the end of the test. The oxidation reaction consumed 75% of the total Zircaloy or almost 100% of the Zircaloy in the path of the burn front. The remaining 25% of the Zircaloywas always below or near the bundle water level. The amount of hydrogen generated was 300±30 g, close to the total conversion of the 1.26-g/s makeup coolant flow within the 45-min high-temperature period. The hydrogen flow fluctuated during the 45-min high-temperature period in response to similar fluctuations (10% to 20% relative)in the bundle coolant flow. The peak hydrogen flow was 190 mg/s, which corresponded to an oxidation power of 28 kW." http://www.osti.gov/energycitations/product.biblio.jsp?query_id=2&page=0&osti_id=10188341 Astolmar (talk) 11:33, 3 September 2008 (UTC)

but this 1993 reference is essentiallly fresh fuel in a low neutron flux. There's essentially no decay heat or nuclear heating. It's hardly surprising the only energy source is from the clad oxidation. Now, what on your understanding happens to a rubble-ised bed of irradiated fuel pellets???

Bob aka Linuxlad (talk) 12:07, 3 September 2008 (UTC)

What did happen to the worked over by the intense fiery reaction of zirconium-steam? Don't forget that this reaction starts at 800 C or so and the decay heat corresponding equilibrium temperature inside the fuel pellets is around 2500 C (way under the melting of ceramic fuel). You can look at Youtube under the tmi and indeed the cited article also shows a less intense but worked over rubble bed. Nothing happens. Stays as it was produced in the churning over by the fire, brocken pieces of fuel pellets. Lose debris field over the hard layer in the TMI-2 reactor. The Hydrogen gas - and most preferably the reflood with water - will keep it cool. Correction: did keep them cool in the TMI-2 accident, INEL SFD ST and the above Canadian full length test. In Chernobyl-4 not much left in a describable volume, it was mixed with all kind of material thrown at it. However the fiery process generated worked over fuel was well identifiable in the lava flows (encased in the zirconia. Hm, where could that come from?!) Astolmar (talk) 12:30, 3 September 2008 (UTC)

I have not yet found a reference or video which says that there was NO urania-melting at TMI - perhaps you can help here.

Even if TMI was mainly rubble-ised that does not gainsay the possibility of large scale melting in large PWRs, which has been used as a limiting case for safety calculations for many years.

Whole-core melt probably happened at SL1 and SPERT IIRC.

Single-channel melt has probably happened at one early UK reactor and in Enrico Fermi.

Single Channel events with fuel melt are the limiting events in many channelised designs.

the Article IS about nuclear melt - unless you argue this is synonomous with the empty set, what do you suggest we change it to!

Bob aka Linuxlad (talk) 14:33, 3 September 2008 (UTC)

• It's best to conduct discussions about articles on the article talk pages, so that other concerned editors can participate and so that it all stays together. I'm going to copy this text and request that everyone continue the discussion at talk:Nuclear meltdown#zirconium-steam ·:· Will Beback ·:· 02:14, 4 September 2008 (UTC)

Speedy deletion of Miklós Duray

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