Device set to see inside unit 2 containment vessel

28 December 2017

A suspended pan-tilt camera attached to a telescopic guiding pipe will soon be used to investigate the interior of the primary containment vessel (PCV) of the damaged unit 2 at the Fukushima Daiichi plant in Japan. The device was developed by Toshiba Energy Systems & Solutions (Toshiba ESS) and the International Research Institute for Nuclear Decommissioning (IRID).

Device for FD2 PCV survey - 460 (Toshiba-IRID)
The camera module and telescopic guiding pipe undergoing testing
(Image: Toshiba/IRID)

In February, Tokyo Electric Power Company (Tepco) sent a "scorpion-shaped" robot - also developed jointly by Toshiba and IRID - into the PCV of unit 2. That survey discovered part of the grating of the platform inside its pedestal had dropped. Although the robot was unable to reach the area directly under the reactor pressure vessel, the company said the information it gathered would help it determine how to decommission the unit.

Toshiba ESS and IRID have now developed a small and radiation-hardened device to investigate the condition under the platform inside the PCV. The device will be deployed from the latter half of January to February.

The device will be introduced into the PCV through a pipe about 12cm in diameter. It comprises a guiding pipe some 13m in length and with a diameter of around 11cm. Attached to this is a further telescopic guiding pipe, about 5m long. A camera module weighing some 2kg is mounted on the end of this. The camera module houses two cameras - a pan-tilt camera and a bird's eye camera - as well as an LED lighting unit, a radiation dosimeter and a thermometer.

Goro Yanase, general manager of Toshiba ESS's nuclear energy systems and services division, said: "We are doing all we can to contribute to the investigation of the interior of the Fukushima reactors. In this case, we have had to meet the challenges of limited access and a highly radioactive environment. Working with IRID, we have succeeded in developing a small device with high-level radiation resistance, and by deploying it we expect to get more information for advancing decommissioning."

Tepco has also carried out robotic surveys of the PCVs of units 1 and 3 at the Fukushima Daiichi plant.

In March, Tepco carried out an investigation of the PCV of unit 1 at Fukushima Daiichi using the PMORPH robot developed by Hitachi-GE Nuclear Energy and IRID. Equipped with a dosimeter and waterproof camera, it took radiation readings and digital images at ten different measurement points within that unit's PCV.

In July, it inserted a screw-driven submersible robot developed by Toshiba and IRID into unit 3's PCV.

Researched and written
by World Nuclear News