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That's a massive report. Even just the chapter on the accident itself. But so far, regarding No. 1, I found:
  • they think the earthquake did not break reactor circuit pipes, based on pressure/steam flow readings before the tsunami hit;
  • at last there is a confirmation that the electric switchboxes of the rectors were submerged by the tsunami, too (thus making initial attempts to restore AC power futile);
  • in addition to the generators and the switchboxes, the seawater pumps of the cooling system were damaged, too;
  • elevated radiation levels inside the building were first detected at 23:00 local time on 11 March, that is seven and a half hours after the tsunami hit;
  • TEPCO's difficulty in following up on the government's order to vent was also because of elevated radiation levels, which forced workers to use improvised methods to open the valves;
  • they mention some confusion in the line of communication between TEPCO's higher and lower echelons and the government regarding a supposed suspension of seawater injection after starting it on the second day, but TEPCO's current position is that at the order of the plant director, there never was an actual suspension.


*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Jun 12th, 2011 at 03:44:30 PM EST
[ Parent ]
From the next section I'm reading, it appears that basically none of the gauges installed inside the reactor pressure vessel are to be trusted, making estimates about the conditions inside guesswork. Take this last one for example:

In the present state, it is thought that steam continues to escape from the gas phase part of the RPV, but the RPV pressure is higher than the D/W pressure, so it is assumed that the opening is not large. However, the pressure changes after March 23 are changing in parallel with the changes in PCV pressure, so the possibility cannot be denied that there is a problem with the measurements.


*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Jun 12th, 2011 at 04:12:56 PM EST
[ Parent ]
Why do they think (most of?) the fuel still in the pressure vessel? Temperature readings:

...after the injection water amount was dropped, temperatures in some areas increased, so it is thought that the fuel is inside the RPV.

Apparently not all the fuel at the bottom of the vessel is under water (have you read this before?):

The temperature of part of the RPV (the feed water nozzles, etc.) is higher than the saturation temperature for the PRV pressure, so at the present stage it is estimated that part of the fuel is not submerged in water, but is being cooled by steam.

What is the rate of aerial loss to the environment?

The inclusion of nitrogen, which started on April 7, was measured to increase the pressure by approx. 0.05 MPa, so at that stage it was estimated that the leakage rate from the D/W was approx. 4%/h.


*Lunatic*, n.
One whose delusions are out of fashion.
by DoDo on Sun Jun 12th, 2011 at 04:22:27 PM EST
[ Parent ]

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