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NOTE: The major means of cooling a reactor with fuel damage caused by a LOCA is the suppression pool. This is achieved by blow down of steam thru pipes and valves into the s/p. The s/p has a very narrow range in which the water level must be kept for it to function as designed: 12'4" to 12'6". Tepco now admits that unit 1 suppression pool is full of water. This makes it extremely difficult to cool, as just pouring in more water doesn't help water around fuel to CIRCULATE and draw off heat. Water is collecting in the drywell from steam out of reactor core which is precipitating back into water. Think this makes the case for valves (which are supposed to be one-way) and pipes of the reactor coolant system being damaged by the high pressure in March. So if there is a bouyant mass of hot steam at the top of the containment vessel, it's pushing down on the water below it, applying more than normal force on the bottom of the containment vessel. NISA talks about their concerns that the mass of water could make the unit more susceptible to EQ's. I believe they specifically mean two things: that the non-design water+steam in the drywell could rupture the bottom of the drywell just from build-up; that an EQ could shift the weight/force during an EQ (think slosh) so that force is more directed at a given point vice evenly distributed. www3.nhk.or.jp

AEC-produced video of the SL-1 accident www.youtube.com

Per the 4/23/2011 #110 Report - Data highlights
Unit 1 is up t to 1.130 MPa, Unit 2 S/C B is reading 136 Sv/h, Unit 3 D/W A is 15.1 Sv/h B is 11.3 Sv/h. Unit 5 needs more water - it's down to 1544 mm with a temp of 43.5.
www.meti.go.jp

*"they always take" Scrambling to get out the door to a Common Frequency conference, so I'm not proofreading, it seems.

@elainekirk is that for an ABWR like 6? I thought 4 was an old BWR but a newer "mark" type? I could be wrong why I am asking. :-)

@Bobby1 The SL1, I read up on it a bit in March seemed so insanely unsafe today.

Re-reading the SL1 incident. Some of the descriptors of the incident sound like potentials in #3. Two things in the known issues with the BWR Mark 1 that really stuck in my head. 1. the reactor vessel (the metal pod) can propel itself upward like a rocket in a pressure situation. 2. The reactor cap gasket has a rather low failure threshold. It will fail at a fairly low pressure (by comparison) and leak. If somehow melted or destroyed fuel was put into the steam before it escaped in the explosion it could explain the highly radioactive concrete covers.

@Bobby1 the "off" iodine/cesium rates? I think someone was bothered by that in various stats. Didn't you also comment on that the other day in the fallout readings? I was reading something this morning about how the boron plates in the SFP can be fragile in some ways. If they were eroded, broken or moved it could be causing issues in 4.

@Nancy Huge amounts of tellurium (and I-132) were found in the air immediately after the explosions (supposedly from ZrTe compounds). In contrast, SL-1 released low amounts of tellurium. But this might have been from #2.

@Nancy Hard to tell, but the Te was released no later than March 15. This indicates concrete interaction.

@Bobby1 so fuel or radioactive materials to concrete by the 15th. Does anyone have an event timeline?

@Nancy Good idea. And try to figure out if it was #2 or #3 (or both, or even #1), and if the concrete was the cap, floor, or rubble.

@Bobby1 I am almost positive the concrete is cap sections. They are about the right size and rough shape. The also came out of the blast plume first like they were shot out of a gun. I am really starting to think they let something catstrophic happen in 3 due to their reluctance to vent that caused 3 to go off like a gun when the hydrogen ignited.

@Nancy The cap would have already been a bubbling goop by then.

@Nancy The Te release would have come from bubbling goop.

Are you talking unique to #3 or in multiple reactor instances?

@Nancy Yes, zirconium oxidizing in the presence of water to as high as 5000C. It would have released barium, lanthanum, strontium, cerium, as well as initiate the concrete reaction. I don't know if it is #2 or #3.... the goop would have splattered to other parts of the mix.

@Nancy By now, there would little Zr left, so you wouldn't expect much tellurium now. I think this had to occur before the explosions.

If I get another lul in things to do I will probably start trying to work on a timeline that can be housed online and maybe group edited?

@Nancy Yes, I think so... tho thinking about it, it could have happened after the explosions too. The cloud had to travel 100 miles, with unfavorable winds, to be picked up at Takasaki. It sounds like it would take some time to get there by March 15.

@bobby, back to #4. You mentioned the info on the SL1 accident. Are you thinking a criticality in the pool might have set it off?