Fukushima Unit 1 More Questions Than Answers From New Inspection

TEPCO has completed a multiple day inspection of unit 1 at Fukushima Daiichi. This new work used the PMORPH robot to inspect the pedestal doorway and lower areas of the containment floor. They hoped to find traces of the melted fuel and surprisingly appear to have found none.

The robot was used over a period of four days inside containment. Images and readings were taken along the catwalk grate outside of the pedestal and on the outer containment floor. These found relatively low radiation readings. While all readings are what would be considered “deadly” they are nowhere near as high as those found inside unit 2. The readings even with the shielding factor of the standing water inside containment are lower than would be expected with the presence of melted fuel.

The only other finding of any significance was what appeared to be a sand like material on the containment floor. TEPCO didn’t speculate on the origin of this material. We have two assumptions for potential causes. One would be sand being injected among the initial sea water injections. This would be less likely to distribute outside the pedestal region if it were to have taken place. Also, much of the sea water back flowed into the turbine building condenser. Another potential is that this is aggregate from damaged concrete. Objects that appeared to be pieces of concrete have been found on previous inspections of the unit 1 containment structure. Under this theory, the concrete bio shield around the reactor or parts of the pedestal concrete could have been damaged by either the earthquake or the heat of the meltdown. This could have caused damage to the concrete such as spalling where concrete breaks apart due to heat damage. More data would be required to clarify either potential cause of the sand substance.

TEPCO has been extremely tight lipped about this work in a manner that is unusual even for TEPCO. Very limited imagery has been provided. Much of it very low resolution and small in size. A few nondescript images of high quality were provided. TEPCO has said they would not release any video of this work until the 27th. Why they are being so evasive with this data raises questions.

The published handouts each used multiple pages to explain that the radiation levels found were inside containment and not in the outer environment. This is likely a response to the mainstream media failures during the recent unit 2 inspections. News reports incorrectly told the public that radiation was rising at the plant.

TEPCO and IRID seemed confident they would find traces of melted fuel in the pedestal doorway and it appears they found nothing. Since they found no indications of fuel in containment or in the pedestal doorway, where IS the fuel?

Photos and data below:

Radiation readings at the various locations including the height above the containment floor.

Grating: 6.7 Sv/h
Grating:  3.6 Sv/h
Grating:  7.8 Sv/h
1 m above floor: 1.5 Sv/h
0.6m above floor:  1.6 Sv/h
0.3m above floor:  5.4 Sv/h

Grating: 3.8 Sv/h
0.3m above floor  11 Sv/h

Between D1 & D2:
Grating: 8.4 Sv/h
Grating: 8.2 Sv/h
Grating: 9.2 Sv/h
0.9m above floor:  6.3 Sv/h
0.9m above floor:  5.9 Sv/h
0.9m above floor: 7.4 Sv/h

Grating:   9.3 Sv/h
Grating:  12 Sv/h
1m above floor:  6.3 Sv/h
0.9m above floor: 9.4 Sv/h

Grating: 10 Sv/h
1.6m above floor:  3.0 Sv/h

These radiation readings do not indicate any areas of significantly high radiation that would confirm the presence of a mass of melted fuel. They don’t even appear to indicate an area of higher radiation that would be a tell tale sign of one area vs. another being closer to said fuel.

March 18 Handout in English (preliminary report)
March 18 Handout in English
March 19 Handout in English
March 21 Handout in English
March 22 Handout in English

Images can be found in our Flickr album for this inspection work.

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