Pmorph Robot Prepares For Fukushima Unit 1 Entry

An improved version of the Hitachi shape changing robot previously used at unit 1 has been unveiled by IRID. The new version will eventually conduct the third robot excursion into unit 1’s containment.

Pmorph includes a radiation sensor on a drop down winch. This will be used to check radiation levels closer to the containment floor at pre-determined locations. One of those is the pedestal doorway that faces the turbine building, inside containment. This has long been suspected as a route that molten fuel escaped the pedestal. The diagram below shows the route Pmorph will take inside unit 1 containment.

Photo below shows the portable hot cell that will be used to put Pmorph into unit 1 containment. This mock up is in the test facility used for training but shows the hot cell in the left yellow outline. This allows the robot to be sent in and later retrieved without exposing workers to radioactive contamination on the robot. It also serves to create a seal for the robot and containment to lower worker exposures.

The diagram below shows the planned locations for containment floor radiation readings. This work should provide information about potential locations of corium (fuel debris) on the containment floor. 

The diagram below shows how Pmorph will drop a sensor near the pedestal doorway to take radiation readings in an attempt to locate corium.

Close up detail of the radiation sensor that will drop down out of Pmorph. It also includes an on board camera that could identify corium or other materials on the containment floor. This all in one combination technology of a radiation sensor and camera in one unit is significant. Other equipment has not had all of this in one sensor. The potential for other uses of this type of combined sensor at Fukushima Daiichi many.

This work is not without risk. The radiation levels inside unit 1 containment have so far been lower than any found inside unit 2’s containment. This doesn’t mean Pmorph would not potentially run into high radiation hot spots. One benefit of Pmorph’s design and mission is that the robot itself will sit further from the areas of expected high radiation. So only the radiation sensor/camera device would be close to the potential source. This may provide a benefit to Pmorph that would allow it to operate with less risk of failure.

IRID and TEPCO have not published a specific date for Pmorph’s inspection work. So far they have reserved one inspection project at a time at the disaster site. So they may wait until Scorpion’s work at unit 2 is completed before Pmorph’s inspection would take place.

Overview of “PMORH” investigation robot (via IRID)
Main body dimension：
Length 699mm x width 72mm x height 93mm
(When travelling on the guide pipe)
When travelling on grating：
Length 316mm x width 286mm x height 93mm
Sensor unit dimension：
Width 20mm x height 40mm
Cable: Length 3.5m
Weight:
Approximately 10kg
Power:
100V
Specification:
Camera x 5, dosimeter x 1
Radiation resistance:
Over 1000 Sv. (approx.)
Operation:
Remote-controlled with cable

IRID Documentation:
IRID report in English
IRID handout in Japanese

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