http://www.canadianmanufacturing.com/regulation/cleaning-robot-pulled-from-fukushima-reactor-due-to-radiation-184384/
Cleaning robot pulled from Fukushima reactor due to radiation
The remote-controlled cleaner was the first robot to enter the nuclear
plant's Unit 2 reactor since the 2011 disaster. It spent just two hours
inside before being yanked out
February 9, 2017
by Mari Yamaguchi, The Associated Press
TOKYO—A remote-controlled “cleaning” robot that entered one of three
wrecked Fukushima reactor containment chambers Feb. 9 had to be pulled
out before completing its mission due to camera glitches most likely
caused by high radiation.
It was the first time a robot entered the chamber inside the Unit 2
reactor since the March 2011 earthquake and tsunami critically damaged
the Fukushima Da-ichi nuclear plant.
Tokyo Electric Power Co. said the intent was to inspect and clean a
passage before another robot does a fuller examination to assess details
of the damage to the structure and fuel inside.
TEPCO needs to know the melted fuel’s exact location and condition and
other structural damage in each of the three wrecked reactor in order to
figure out the best and safest way to remove them. It is part of the
plant’s decommissioning work, which is expected to take decades.
The robot went only partway on a narrow bridge into a space under the
core that TEPCO wants to inspect closely. It crawled down the passage
while blowing off some debris with a water spray and peeling them with a
scraper on its head, and about two hours later, the two cameras on the
robot suddenly developed a lot of noise and its image quickly darkened—a
sign of a mechanical glitch from high radiation.
The outcome means the second robot will encounter more obstacles and
have less time for examination on its mission, currently planned for
later this month.
The robot is designed to withstand up to 1,000 Sieverts of radiation,
and its two-hour endurance roughly matched the estimated radiation level
of 650 Sieverts based on noise analysis of the images transmitted by the
robot-mounted cameras. That’s less than 1 per cent of radiation levels
inside a running reactor, but still would kill a person almost instantly.
TEPCO officials reassured that despite the dangerously high figures,
radiation is not leaking outside of the reactor.
Images recently captured from inside the chamber showed damage and
structures coated with molten material, possibly mixed with melted
nuclear fuel, and part of a disc platform hanging below the core had
been melted through. Similar photographic analysis of radiation levels
from the visual data was slightly lower than Thursday’s figure.