Tepco has just released the results of an investigation made in the containment of reactor 2. Nothing really new, apart from a found assembly element, we are waiting for radioactivity measurements now.
20 janvier 2018
A new 10-hour investigation was conducted in the Fukuishima Daiichi reactor 2 containment enclosure, according to a report released by Tepco on January 19, 2018. However, Tepco does not indicate the date of the operation. The images and measurements were taken using a 13 meter probe with a camera. TEPCO will only broadcast the radioactivity measurements later.
Photo: an assembly element was found
According to this document, TEPCO gives two main informations:
– The entire bottom of the base of the reactor base is covered with deposits of sandy and clay.
– Some fuel assembly components have fallen to the base of the reactor base and are considered fuel debris.
As usual, Tepco does not use the word “corium”. It does not speak more about the radioactive environment of the place which is lethal (a last year made measure at this place was 530 Sieverts) but promises to return soon. I will update this page when the information falls.
The deposit of sandy and clay types is what is at the bottom of the enclosure and which had already been spotted last year around the pedestal. This vase prevents a clear view of the bottom of the enclosure because the slightest movement of the camera, the water is troubled.
For the first time, Tepco discloses a diagram showing the inside of the reactor pedestal. We see :
– an upper platform, which was already known, which allows access to control rods located just below the reactor vessel. This, according to the February 2017 report, is pierced with a hole 1 meter in diameter. It is the mass of the corium coming from the tank during the meltdown that made this hole.
– an intermediate platform that Tepco claims has not been piereced (but the diagram does not show it in full)
– An annular lower platform bordering the wall of the pedestal, which Tepco also claims that it has no hole. But, same remark, the diagram shows only half.
The piece of assembly that emerges very clearly from a pile of various materials is an upper tie plate. It is surmounted by a bar (“bail handle”), a kind of handle for moving the assembly using an articulated arm. This photo makes it possible to deduce that at least one whole assembly has passed through the tank, which implies that the tank has a hole of at least the width of an assembly (approximately 50 cm). The probe has certainly taken pictures of this hole but Tepco do not release them.
Type of assembly element found on the lower platform of the No. 2 reactor pedestal.
This element is the upper part that we see for example in these assemblies of the reactor pool
Toshiba’s probe, during its presentation in Yokohama, December 22, 2017. The telescopic arm carries a panoramic camera.
Here are the photos of the interior of the BR2 containment building released by Tepco on January 19, 2018:
Here are some pages from the report on the same date:
Tepco’s full report of 19 January 2018
Special thanks to Pierre Fetet of the Fukushima Blog
Translation Hervé Courtois (Dun Renard)