Rapid meltdown occur(ed) in No.1 reactor

[FBaggins]

Tokyo Electric Power Company says most of the fuel rods in the No.1 reactor at the Fukushima Daiichi nuclear plant had dropped to the bottom of the pressure vessel within 16 hours of the earthquake on March 11th. The plant operator revealed its findings on Sunday. TEPCO said it analyzed the data and calculated a timeline for developments in the No. 1 reactor on the assumption that it lost its cooling system as soon as the tsunami hit.

The firm said that about four and half hours after the quake the level of water in the pressure vessel fell below the top of fuel rods and that parts of them began melting. The temperature of the rods is believed to have reached 2,800 degrees Celsius at this stage, and the meltdown advanced rapidly. Almost all the rods melted and dropped to the bottom of the pressure vessel by 6:50 am on March 12th.

TEPCO said the temperature dropped after water was poured into the reactor starting at 5:50 AM the same day. The firm says the melted rods created small holes in the bottom of the vessel. It believes the amount of radioactive substances that could spread from the reactor will be limited.

NHK's correspondent says TEPCO should analyze the situations at the No. 2 and No. 3 reactors as soon as possible.

http://www3.nhk.or.jp/daily/english/16_05.html

The amount "of radioactive substances that could spread from the reactor" may be "limited", but this sure complicates any cleanup plan. Probably years to remove the fuel.

[Fledermaus]

1. The reality is they don't know where the corium is and neither do you.

[FBaggins]

2. Ah... But they know a number of place where it *isn't*

Including the water table and any number of your prior claims.

[thereismore]

3. "Small holes" eh? They always insert these optimistic baseless tidbits to make you feel better.

Fucking corporations.

[Javaman]

4. Until they announce the the small holes were actually gaping openings. nt

[FBaggins]

5. They seem to think that the bulk of the core is at the bottom of the RPV

The holes couldn't be too big and have that happen, right?

Unit #2 remains the one that's most likely to have the most significant breach of the RPV... since we still don't know just what events caused the suppression chamber failure. The building is the most intact (ignoring #5 & #6 of course), so a gas explosion seems less likely than a steam explosion from molten fuel dropping into water at the bottom of the primary containment.