| The Raccoon and one of its supporting relays (Image: Tepco)
A robot vacuum cleaner dubbed the Raccoon is to tackle contamination within Fukushima Daiichi 2 in preparation for workers re-entering the building.
From 28 November Tepco will begin a trial of the powerful remote-controlled washer unit. This will move around the floor of the reactor building's first level, scrubbing and jet washing the concrete surface in an attempt to bring down radiation levels. If successful, this method could be used throughout the building.
Unit 2 is the only one of the four stricken reactors at the site that did not experience a hydrogen explosion and so remains basically airtight without the need for a secondary cover. Most of the radioactive material given off by the damaged core was retained within the building and is now distributed around its internal surfaces, putting it off-limits for workers.
Controlled via heavy cables, the Raccoon is powered by two mobile relay units and supported by systems supplying suction and water. It features a 35 kilogram jet head with rotating washers and cameras to aid steering. It moves at up to 10 metres per minute and uses 13 litres of water per minute at a pressure of 15 MPa. A separate robot oversees the cleaner's progress.
The Raccoon system is being deployed on the building's first floor as this is the location of the access hatch to the reactor containment vessel that Tepco needs to inspect. This will require another remote-controlled operation, but access by workers is needed to open the hatch and set up equipment.
The northern part of the floor will be cleaned first while the southern part will be tackled from around March next year. Work towards clearing the level started several weeks ago with robots clearing away the various items of plant equipment on the floor that would present an obstacle to the Raccoon.
Researched and written
by World Nuclear News