Additional Analysis Of Unit 1 Containment Inspection

Workers did a brief inspection inside the containment of unit 1 earlier this week. We reported the initial findings yesterday.

The point of the inspection was found to be the north-west corner of the building above the control rod drive equipment hatch. This also is near the location of the torus inspection back in June 2012. The torus inspection was along the west wall on the first floor. Workers sent a camera scope down through the floor to look inside the torus room. The inside of the torus room was in considerably worse shape than the other units. The combination of the damaged and scorched appearance in the torus room and the structural debris found inside containment raise concerns about what took place inside unit 1.

Both efforts went on in that north-west corner of the building. One possibility for the damage in this area could be a small break LOCA on that side of the reactor, something long suspected as at least one of the events that happened at unit 1. Other possibilities include various types of explosions or projectiles

Radiation readings in unit 1 have shown the north-west corner has lower radiation than the south-east side that had considerably higher radiation on the first floor. More information would be very useful including similar inspection in the high radiation side of the building.

Update: the location of the high radiation on the SE side is also where the steam was coming up through the floor back in 2011. See diagram below (thanks to Longtimelurker for finding it). That steam location had a 4Sv/hr radiation reading (lethal levels). Peter also mentioned that the steam/smoke seen inside containment at the higher level on the scope inspection this week indicates something inside containment is boiling. This puts the reactor outside of “cold shutdown” claimed by TEPCO. 

Below are marked up diagrams of unit 1 to explain the location of the two inspection events.

First floor unit 1

Unit 1 torus room basement (the blue lines should be ignored. They are from an inspection at unit 2)

First floor unit 1 containment inspection penetration marked as X-100B

Early radiation readings in unit 1

Location of the 2011 steam through the floor on 1st floor unit 1



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