Robot survey in No.1 reactor container

April 7, 2015

TEPCO to conduct robot survey inside Fukushima No. 1 reactor container

http://mainichi.jp/english/english/newsselect/news/20150407p2g00m0dm031000c.html

TOKYO (Kyodo) -- The operator of the crippled Fukushima Daiichi nuclear plant said Monday it will conduct a remote-controlled robot survey inside the No. 1 reactor's containment vessel, a step toward grasping the condition of melted fuel debris.

It will be the first time that Tokyo Electric Power Co. uses a robot to check the interior of a reactor's primary containment vessel. The company hopes to obtain data on radiation levels and temperature as well as images inside the vessel.

Fuel inside the Nos. 1 to 3 units is believed to have melted through the reactor pressure vessels and has been accumulating in the outer containers. But the details remain unknown more than four years after the 2011 nuclear crisis due to extremely high levels of radiation.

It is currently not feasible to conduct the survey in the lower part of the containment vessel where fuel debris is believed to be accumulating, as  the robot cannot be deployed in highly radioactive water generated in the process of cooling the fuel, a TEPCO official said.

In October 2012, radiation levels inside the containment vessel, which workers measured by lowering a dosimeter, measured up to 11 sieverts per hour.