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Summary of some of Joe Miller's Experience. This is my Blog.
My name is Joe miller and among other things, I am a nuclear engineer. To give you an idea of where my perspective is coming from, I will provide some of my back ground information. I have more than 35 years in the nuclear energy field. I worked at a boiling water reactor (BWR) for 9 years where I was a senior engineer responsible for many safety systems that help mitigate loss of coolant accidents such as the reactor core isolation cooling (RCIC) system, the residual heat removal system (RHRS), and the emergency diesel generators (EDGs). I was involved with safety assessments of the emergency diesel generators (EDGs) and supported engineering and maintenance of these systems. As supervisor of Engineering analysis, I was responsible for developing a probabilistic risk assessment (PRA) that cover external events such as fire, seismic and flooding events. Additionally, I was responsible for most of the safety analyses on site and I also performed loss of coolant accident (LOCA) simulations and I was responsible for fuel reload thermal hydraulic analysis and reactor transient analysis. As Director of Nuclear Engineering on site, I was responsible for developing and implementing the station's emergency operating procedures (EOPs) and the severe accident management procedure guidelines (SAMGs). I was also responsible for all reactor fuel on site, which included fuel in the reactor and fuel in the fuel storage pit. This responsibility also included all reloads, safety analyses and support for operations and reactor engineering in all areas of fuel. josephmiller.typepad.com

josephsmiller.com Link to Joseph S. Miller's Papers and Presentations

will see what i can dig up for early images of 4 between events those might help

I'm pretty sure WL is relative to "top of rods". For example, see theenergycollective.com , which includes the footnote "*1: Minus figure means that water level is below the top of the fuel rods." (the link just reproduces the FEPC Washington office handout -- I've seen other sites repro them.)|

@Nancy: the way #4 north wall look and the fact the north roof "row" seems highly damaged make me pretty sure this thing has been flying inside the building, bounced against the wall and went through the roof, and is now laying up there in a delicate balance.

@Jocelyn Mayer it had to come from 4. could it have been pulled up and out somehow?

@fitter: sorry, got no time right now to study this... Got work to do...

See also NISA, for example www.nisa.meti.go.jp states under the plant parameters table "*2: Distance from the top of fuel". Have to disagree on this one -- I really do not see NISA explicitly adding a footnote to clarify what the number means and getting the footnote wrong.

@Markfm: yes, you may be wrong; this is to be clarified.

interesting tidbit abt 4 sfp from tenzig"s link In addition to the reactor fuel, other reactor internals, i.e., steam dryer, cycle separators and stand pipes, and the upper head, were all removed and placed in the SFP for shielding purposes since these materials are radioactive.

@Nancy: I meant it did hit the north wall _from inside_, then flying to the north and up direction; then the wall damages seem logical: it has been pushed outside by a huge shock from inside.
The upper part of the wall is caved in just because the wall has been caved out below; like a piece of paper tied to its edges: push in the middle, the place you push will go in a direction, the upper part will fall the other direction.
Don't know if my explanations are clear...

@Tenzing: thanks for the infos !
Why ? Because they never though there could be a problem in the SFP.
What could happen to an empty reactor ? Nothing .... except what happened; was not planned, then nothing has been done to prevent it...

The core shroud and other internals replacement had carried out at Fukushima-Daichii Unit #3(1F3) of Tokyo Electric Power Company (TEPCo) in Japan. And the in-core monitor (ICM) housing replacement had carried out at Fukushima-Daichii Unit #4 (1F4). Both projects are the first experiences of the replacement procedures developed for the welded core shroud and ICM housing. The outline and experience of these projects are discussed in this paper. When the crack was found in the Fukushima-Daiichi #2 (1F2), the core shroud was reinforced by the brackest which has been studied as one of the repair concept. www.jsme.or.jp

Since NISA clarified their English reactor status report, which stated "*: Distance from the top pellet" on 15 March www.nisa.meti.go.jp to state "*1: Distance from the top of fuel." in www.nisa.meti.go.jp it really is not ambiguous. FEPC's version of the footnote was their attempt to be even more clear.

@Jim Carver Hi Jim! I have a few PDF's I will email over to you for archiving.

Highly radioactive water removal continues, water level drops by 1 cm
"The condenser (where we want to store water) is already full and water appears to be flowing in. We don't know the reason" mdn.mainichi.jp

@xxx They haven't been releasing any temperature data for reactor 4 or SFP, have they? Is the thermography image all we have?

Still curious about the actual source of #4 core heat, though it normally isn't all that high a number. By chance do the peaks in core thermography temp come the same day, or day before, we see a large injection of water into #4 SFP? Dumping into SFP, leak through the gate into the core masking residual heat until it goes away (maybe leak in the penetrations at the bottom of the well)?

It tends to be reported in the NISA Seismic damage reports, just that you have to parse the text to see when and how much they choose to pour in on a given day.

@Markfm THere has been talk that the seals on #4 sfp are leaking. Not sure if that includes the gate door closure system or just is seals around where the gate joins the 2 units. But water runnoff falling into the core well could account for the heat/cool cycle we are seeing. Still stumped by the heat signature in front of the yellow reactor cap. We have a few days where that heats up and there are enough landmarks to tell it is another area, past the well.

look on 18th sfp was 20C and core 25C, today it is 18C SFP and 29C core...