TEPCO abandons second robot

April 21, 2015

Images show structures intact near Fukushima reactor; robots abandoned

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201504210045

By HIROMI KUMAI/ Staff Writer

A second robotic probe was abandoned after completing its survey mission inside a reactor containment vessel at the crippled Fukushima No. 1 nuclear plant, Tokyo Electric Power Co. said.

TEPCO, operator of the plant, said April 20 that it has wrapped up the study of the highly radioactive environment at the No. 1 reactor and given up efforts to retrieve the robot.

“We have gathered sufficient information on the inside of the containment vessel,” a TEPCO official said.

The utility started the survey of the containment vessel by sending in a tubular-shaped robot to shoot images and monitor radiation levels and temperatures on April 10. The robotic probe, however, became inoperable.

The second robot entered the containment vessel on April 15.

TEPCO said images taken by the devices showed that scattered cables and other debris are unlikely to hamper the next stage of the decommissioning process there.

The plant operator said the photos revealed no obstacles in an area connecting the first floor and the basement, and that the surrounding facilities are more or less intact.

TEPCO on April 20 released additional images taken by the robots, including piping, conduits, ladders and pumps to circulate water inside the reactor.

The images snapped by the second robot confirmed TEPCO’s assumption that the first robot became stuck in the iron-mesh first floor of the container vessel.

A monitoring camera installed in the containment vessel to control the second robot later malfunctioned because of high radiation levels, forcing TEPCO to give up its plan to retrieve the robot.

“Attempts to forcibly retrieve the robots could pose the larger risk (of further damaging it),” a TEPCO official said.

After analyzing radiation levels, temperatures and other data obtained by the robotic probes, TEPCO plans to start a robotic survey of the basement of the containment vessel, where coolant water is circulating.

This phase is scheduled to start by the end of March next year and is intended to gather more detailed information for preparations to remove the melted nuclear fuel, the toughest part of the decommissioning process

New photo confirms robot probe stuck inside Fukushima No. 1 reactor vessel

http://mainichi.jp/english/english/newsselect/news/20150421p2a00m0na006000c.html

A new photo of a disabled observation robot inside the disaster-stricken Fukushima No. 1 nuclear plant's No. 1 reactor containment vessel was released on April 20 by plant operator Tokyo Electric Power Co. (TEPCO).

TEPCO believes that the new image -- shot by a second robot sent into the containment vessel -- confirms that the first device was immobilized after its tread snagged on the vessel's steel mesh floor.

The second robot was scheduled to be removed from the highly radioactive containment vessel, but TEPCO decided to leave the probe inside over fears that the probe would get stuck on its way out. In the end, the utility cut the robot's power cable so it wouldn't get in the way of future inspections, abandoning the device.

Though TEPCO lost both probes, the robot inspections appeared to show nothing blocking the entrance to the containment vessel's basement level, where the No. 1 reactor's melted fuel is thought to have pooled. The utility also confirmed that contaminated water is collecting in the basement.

TEPCO is planning to develop another robot capable of underwater missions, and is looking to inspect the containment vessel's basement level by the end of fiscal 2015.

April 21, 2015(Mainichi Japan)

April 20, 2015

TEPCO issues video of robot stranded inside reacto

http://www3.nhk.or.jp/nhkworld/english/news/nuclear.html

Apr. 20, 2015 - Updated 10:13 UTC+2

The operator of the Fukushima Daiichi nuclear power plant has issued a video of a robot stranded inside one of the damaged reactors.

The video released by Tokyo Electric Power Company on Monday shows the remote-controlled robot tilting to the right inside the containment vessel of the No.1 reactor.

The robot was sent inside the vessel on April 10th but stopped working after advancing just 10 meters. The utility has since given up on recovering the device.

TEPCO sent a second robot to retrieve the first robot. But the probe's camera malfunctioned due to radiation exposure.

The utility decided to abandon both robot probes.

TEPCO says video footage shows no major damage to a part leading to the bottom of the containment vessel. Melted nuclear fuel fell on the vessel in the 2011 accident.

The operator says it will analyze the footage and other data to remove the fuel.