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jlduh
#6832
May12-11, 07:11 AM
P: 468
Quote Quote by jlduh View Post
Ok now let's list what new questions are raised IF WHAT TEPCO REVEALED IS TRUE AND IF THEY DON'T COME BACK TO APOLOGIZE FOR A NEW MISTAKE ABOUT THIS (who knows?):

1- if what used to be the core in N1 has totally relocated at the bottom of the RPV, how can all the parameters given by TEPCO be interpreted? Total BS?

2- the same question applies to the 2 other reactors (2 and 3): are this parameters relevant to assess the situation or can it be considered like for N1 as total BS? Then i have to admit that one of the "proofs" that N3 reactor was still there in a "close to normal shape" is clearly weakened because of this revelation...

3- based on the amount of fuel initially inside the reactor N1, plus the volume of the "other stuff" inside (control rods, etc.), is it even physically possible, from the volume standpoint, based on the dimensions of the RPV and its layout, that ALL the fuel has enough room to relocate below the "1m below the bottom of fuel rods" level? This calculation has to be done to assess if what TEPCO says is consistent with reality and IF WE CAN THEN ASSUME that NO MELTED FUEL/LAVA LEAKED OUTSIDE OF THE BOTTOM OF THE RPV. If there is not enough room, then at some point it would probably mean that some lava leaked outside.

4- considering what is below the RPV, the drawings and sketches we have indicate that there is below it what is called sometimes "reactor cavity" where sits all the control rods mecanisms and some other stuff.







The question is: do we think this cavity is now full of water coming from:

A) the containment vessel around (which is supposedly flooded to some level) whatever path the water folllowed (leaks, etc.)

or

B) the leaked RPV (bottom) especially through control rods bores or any other leakage there.

5- If this cavity has water in it, and if it is a quite closed cavity (concrete around) then any drop of lava from RPV could create a new feared steam explosion.

But who knows, maybe there is already some lava there? The calculation of point number 3- is a first check for this assessment.

6- how can such a mass of melted/damaged fuel relocated at the bottom of the RPV can still be "cooled" by only sitting water above it? In TMI meltdown, only half of the core was melted and relocated, but more than 1 meter below the bottom of fuel rods levels, this is a 100% damage and relocation.

As a first try to assess the point that i listed above (3-), i mean the volume of the possibly melted fuel at N1, we could start with the TMI corium data, especially densities:

"The bulk density of the samples varied between 7.45 and 9.4 g/cm3 (the densities of UO2 and ZrO2 are 10.4 and 5.6 g/cm3). The porosity of samples varied between 5.7 and 32%, averaging at 1811%."

http://en.wikipedia.org/wiki/Corium_(nuclear_reactor)

Of course it's a little bit difficult to be sure of the accuracy of this approach because:

-TMI was a pressurized reactor, so the core is substantially different.
-the TMI core was only around 50% damaged



-There can be some void/porosities in various combinations inside
-AND, last but not least, we still don't know if part of it melted, or just got damaged, and in which percentage. I even saw in an article (don't remember which sorry) that the fuel has been "sliding" below (i don't know how to interpret this!).

Anyway, the 100% corium hypothesis can be calculated to assess the minimum volume it would occupy assuming it's at the bottom of the RPV (which seems strange IF the temp of 100C is confirmed, but i don't trust to much these readings now i must say...).

Any hypothesis with only a part of the core melted (partial corium) would result in a global lower density for the destroyed core, so a bigger volume. So let's see if the minimum volume hypothesis (100% corium) fits the actual volume at the bottom of he RPV, 1m below the bottom level of fuel rods.

1- we have some possible densities for corium between 7.45 and 9.4 g/cm3 (the densities of UO2 and ZrO2 are 10.4 and 5.6 g/cm3).

2- we need the core mass in unit 1, including all the "stuff" around, and the mass of the control rods.

3- we need the volume of this part of the RPV for Unit 1 (around 5m diameter I think, but we need more precise data). The key data is also how high were located the bottoms of fuel rods from the very bottom of RPV.

Any sources of infos?

EDIT1:
Found this from tepco site:
http://www.tepco.co.jp/en/nu/fukushi...1/index-e.html

--> So inner diameter of RPV is indicated "around 4,8m"
--> 400 fuel assemblies, 69 tons of uranium (but do they include the total weight of fuel rods or just uranium content?)
--> 97 control rods (which unit weight?)


EDIT2:

i add this picture and sketch of BWR RPV:

This one was called BWR800 (800 MWatts?) on the page i found it; it shows the bottom of the RPV with the peripheral flange on which it seats over its concrete piedestal, and the many holes into which the control rods are entering (damn how can this thing not leaking???)



these sketches of RPV are from BWR4 and 6 designs, but i think the global layout is the same so it gives some ideas: