30 Janvier 2017
January 30, 2017
Possible fuel debris located in reactor
NHK has learned operators of the crippled Fukushima Daiichi nuclear plant believe they may have located molten fuel inside one of the plant's reactors.
If confirmed, this would be the first time since the 2011 nuclear disaster that they have managed to determine the exact location of the debris.
The operator of the plant, Tokyo Electric Power Company, began sending a remote controlled camera into the containment vessel of the Number 2 reactor last week.
On Monday, it transmitted images of a black mass on the floor under the reactor core.
The operator suspects it is fuel debris, a mixture of molten fuel and broken interior parts.
It plans to send in a robot equipped with a radiation-measuring device early next month to get a better idea.
TEPCO plans to hold a news conference on Monday to explain more about the finding.
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January 30, 2017
Tokyo Electric Power Co. said Jan. 30 it may have finally pinpointed the location of melted fuel at the Fukushima No. 1 nuclear plant, nearly six years after the triple meltdown unfolded there.
If confirmation is made, it would represent a breakthrough in the daunting task of decommissioning the stricken nuclear plant.
A remote-controlled camera fitted on a long pipe detected black lumps on grating in the lower part of the containment vessel of the No. 2 reactor at the plant early on Jan. 30, TEPCO said.
The wire-mesh grating is located below the pressure vessel of the reactor. The lumps were not there before the Great East Japan Earthquake and tsunami on March 11, 2011, caused the nuclear disaster, according to TEPCO.
The utility plans to determine whether the lump is melted fuel based on images and radiation levels taken by an investigative robot and other data. The robot, called “Sasori” (scorpion) and fitted with two cameras, a dosimeter and a temperature gauge, will be sent into the No. 2 reactor containment vessel next month.
High radiation levels have hampered efforts at the nuclear plant to determine the condition and location of melted nuclear fuel.
TEPCO tried--and failed--three times to locate melted fuel using an industrial endoscope at the No. 2 reactor.
The latest investigation inside the No. 2 reactor began on Jan. 26 to locate the melted fuel.
The company is preparing to devise a method to retrieve the melted fuel in fiscal 2018 as part of the decommissioning work.
Tepco on Monday found what may be melted nuclear fuel debris that penetrated the reactor 2 pressure vessel at the Fukushima No. 1 plant.
Tokyo Electric Power Company Holdings Inc. said more analysis and investigation is needed to confirm that the black lumps detected in the reactor’s containment vessel are indeed fuel debris.
The steel pressure vessel houses the nuclear fuel rods and is set up inside the surrounding containment vessel.
“At this point, it’s difficult to clearly identify what they are,” said Yuichi Okamura, general manager of Tepco’s nuclear power and plant siting division, during an evening news conference at the utility’s Tokyo headquarters.
Video footage from Monday’s probe showed black lumps that looked like something that had melted and then congealed, sticking to parts of a steel grating area at the base of the containment vessel.
The material could be melted paint, cable covers or pipe wrappings, Okamura said.
Still, this is the first time Tepco has detected anything in any of the facility’s three wrecked reactors that might be melted fuel rods since the outbreak of the crisis in March 2011. Okamura described the finding as “valuable information.”
The location of the debris and what form it is in are critical to eventually recovering the fuel.
Tepco plans next month to send in a remote-controlled robot equipped with a thermometer and dosimeter. Analyzing the temperature and radiation level will help identify whether the lumps are fuel debris, Okamura said.
The fuel melted after the March 11, 2011, earthquake and tsunami knocked out Fukushima No. 1’s power supply, including the vital cooling functions.
It is believed that reactor No. 2’s fuel rods melted and penetrated the bottom of the 20-cm-thick pressure vessel and fell in to the containment vessel.
Tepco has been conducting an investigation to check the interior of the containment vessel since last week.
In a previous try, workers inserted a rod equipped with a small camera as a precursor to sending in the remote-controlled robot.
The first attempt turned up nothing of note, but the utility then tried a longer rod — 10.5 meters long — on Monday that could capture images of the area beneath the pressure vessel.
The video footage also showed that water droplets were falling, which Tepco said must be cooling water being injected into the damaged pressure vessel.
Reactor 2 is one of three reactors, including 1 and 3, that experienced fuel meltdowns.