On 6/29/2015, Tepco announced they detected 1197 mSv/h near unidentified substance overflowing from PCV 2 (Primary Containment Vessel of Reactor 2). Because the highest detectable level of the used dosimeter was 1000 mSv/h, the actual radiation level can be higher than 1197 mSv/h.
In order to collect image data of the inside of PCV 2, Tepco was investigating the access hole on the wall.
The substance was found overflown from the lid of the hole by a remote control robot called “PackBot”.
The second highest reading was 1150 mSv/h. The composition of the substance has not been announced.
Additionally, on Tepco’s source to indicate the location of the issued hole, there are two parts concealed. (Blue circled on the photo attached below)
It is not known what they tried to hide from the press release.
Source: Fukushima Diary