After the new round of contaminated water leaks were admitted by TEPCO, we revisited the technical design of the buildings and where they could leak from. The buildings themselves are not as solid and contained as one would assume. Even the containment structure has hundreds of “holes” in it for pipes, cabling and the torus vents to pass through. These are sealed to prevent leaks but the penetration seal materials can melt or otherwise fail. Worker Happy11311 mentions exactly how many penetration holes are in the outer reactor building walls.
If there are 590 building penetrations that are below the groundwater level, each of those provides a potential route out for contaminated water. The groundwater height is about 3000 OP as seen with the blue line in the diagram below. This is about the same height as the standing water in the torus room.
Anything below the blue line has the potential to leak. It is also known that neither unit 1 or 2 have containment structures that can hold water. Unit 3 is assumed to not hold water. It isn’t know for sure where or how any unit is leaking, but there are many assumptions. Anything leaking out of the containment structure would flow downward by whatever route is available.
In our review we did find some additional places that are not water tight in the lower levels. Most of the publicly available floor plans and drawings do not have the level of detail needed to see every pipe penetration and opening. This floor plan from TEPCO that shows the torus room level does show some leak routes. In the two right side corners there are sump pump pits. These are used to pump groundwater out of the building area during normal operation. Each right side corner also has a torus drain pump. That water would have to be pumped to some sort of controlled water storage so these pumps likely have pipes that leave the torus basement area. On the left side each corner shows an open doorway that leads to an accessory building that houses equipment for the reactor. This is outside the reactor building walls. These two doorways provide a route out of the torus room into the adjacent building. In the middle is the base of the containment structure and pedestal. A sump pit exists below the control rod drive equipment in the pedestal and two sump pumps are also located nearby. It is not indicated how those pumps route their water out of the containment pedestal area. The accessory buildings to the left would be on the land (hill) side of the plant.
This plan drawing below is cited as being obtained from GE/TEPCO/METI and claims to be a BWR Mark 1 reactor but may not be 100% accurate of structures at Fukushima Daiichi. The blue boxes below show a blow out panel in the outer reactor building wall and the HPCI cooling unit outside the reactor building. If these exist in the Fukushima reactors in the same manner, they would provide a route for water leakage that is below the groundwater line. These would allow water to leak into the accessory building. If similar panels exist in other locations they would provide more leak routes. .
Images from the most recent scope inspection of the unit 1 torus room show what would be the upper left corner of the torus room on the floor plan posted earlier. That corner shows an opening in the outer reactor building wall on the floor plan. A photo taken of the bottom of the torus room but within the area that houses the torus tube shows what appears to be an opening in the 45 degree angle wall that creates the corner of the reactor building. The debris on the torus room floor? TEPCO hasn’t said what that is, just that it wasn’t highly radioactive.
Views of the area seen by the scope also indicated the possibility that the corner area was accessible from the main torus room. RHR pumps were seen below the water line and equipment that could not be housed next to the torus tube area was also viewed with a clear view into what appears to be a sub room. This creates a situation where it could be possible for water in the main torus room to flow into the corner areas that then have routes out of the reactor building into the accessory building.
RHR pump below the water line
View of the torus tube side during the scope inspection
What all of this shows is the potential for leakage points around the lowest levels of the reactor building. TEPCO has not released any detailed information or admissions about this but what can be gleaned from various other reporting shows the potential. Once water leaves the reactor building it only needs to find a route to the sea. Multiple tunnels and open canals exist around the plant along with the purposeful structures in the turbine building area to route sea water in and out for cooling. There is also the potential for water to travel outside built structures as TEPCO is now finding out as they test wells dug near the sea port.
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