to probe Fukushima reactor again to confirm nuclear debris
An executive of the operator of the crippled Fukushima Daiichi
nuclear complex said Friday the company plans to probe inside the
plant's No. 2 reactor by the end of February to confirm whether the
black mass spotted in a recent survey was nuclear debris.
Naohiro Masuda, the chief decommissioning officer at Tokyo
Electric Power Company Holdings Inc. told Kyodo News it is "possible"
to conduct the probe using a robot, the day after the operator
announced it had detected extraordinarily high radiation levels
inside the reactor.
The operator will be able to tell whether the deposits are
nuclear debris from the March 2011 meltdown if new images and data
such as the radiation levels and temperatures are obtained in the
upcoming robot survey, he said.
"Images of the bottom of the pressure vessel and radiation
levels are very important. It is worth surveying even if we end up
abandoning the robot," Masuda said.
TEPCO said earlier this week it had detected a record radiation
level of up to 530 sieverts per hour and found a black mass, believed
to be nuclear debris, and a 1-square-meter hole in a area of metal
grating beneath the pressure vessel during a recent survey inside the
No. 2 reactor.
Images captured using a camera attached to a telescopic arm in
late January showed the hole in the grating that is feared could
hinder the robot's probe abilities.
Masuda said while it is easy to assume that nuclear debris
dropped and caused the hole and other damage to the metal grating, he
wants to "carefully judge" the cause.
He admitted the area in which the robot can operate has been
reduced by the hole and other damage to the grating. But he stressed
the need to conduct the survey nonetheless.
The record reading has posed unexpected difficulties for
conducting further probes inside the reactor as the robot could fail
in less than two hours when exposed to such high levels of radiation.
But Masuda raised doubts about the levels, saying it could have
been a "mistake in the measurement," as the radiation levels
beneath the pressure vessel were relatively low at 20 sieverts.
Economy, Trade and Industry Minister Hiroshige Seko said in a
press conference Friday, "Confirming the conditions inside the
reactor is the first step towards decommissioning."
"While difficult tasks and unexpected matters may arise, we will
mobilize all of Japan's technological capabilities to steadily
implement the decommissioning work and rebuild Fukushima," he added.
On the same day, a nuclear research organization unveiled a
robot that will be tasked with surveying the No. 1 reactor of the
Fukushima plant in March as TEPCO plans.
The stick-like robot, some 70 centimeters in length and equipped
with a camera, is remotely controlled and can articulate its two
joints, according to the International Research Institute for Nuclear
The institute was established in 2013 by nuclear plant
constructors, power firms and government organizations to develop
technology needed for the decommissioning of the Fukushima plant,
which was damaged by the March 2011 earthquake and tsunami.
After the disaster, three of the plant's reactors suffered
meltdowns in the world's most severe nuclear crisis since the 1986
During a robotic survey in April 2015, the operator found no
major obstacles in the robot's path in the No. 1 reactor while
discovering water accumulating in the basement.
In the upcoming survey, the operator hopes to search the water
by deploying a camera and a radiation censor. (Feb. 3)