24 Décembre 2017
December 23, 2017
Toshiba unveils device for Fukushima nuclear reactor probe
THE ASSOCIATED PRESS
YOKOHAMA--Toshiba Corp.'s energy systems unit on Friday unveiled a long telescopic pipe carrying a pan-tilt camera designed to gather crucial information about the situation inside the reactor chambers at Japan's tsunami-wrecked Fukushima nuclear plant.
The device is 13 meters long and designed to give officials a deeper view into the nuclear plant's No. 2 reactor primary containment vessel, where details on melted fuel damage remain largely unknown.
The Fukushima plant had triple meltdowns following the 2011 quake and tsunami. Finding details about the fuel debris is crucial to determining the right method and technology for its removal at each reactor, the most challenging process to safely carry out the plant's decades-long decommissioning.
Japan's stricter, post-Fukushima safety standards also require nuclear plant operators elsewhere to invest more time and money into safety measures.
On Friday, Kansai Electric Power Co. announced that it would decommission two idle reactors at the Oi nuclear power plant in western Japan, citing the difficulty of adding all the safety requirements at the nearly 40-year-old reactors that would be needed to get approval for their restart.
Reports have said it would cost about 58 billion yen ($500 million) and take 30 years to decommission a reactor, about half the estimated cost to restart one.
Also Friday, Japan Nuclear Fuel said that it was postponing the planned launch of its trouble-plagued spent fuel reprocessing plant by three more years until 2021. It cited delayed approval by the authorities. It also said it was postponing the planned manufacturing of fuel from recycled plutonium and uranium.
The mission involving Toshiba's new probe at Fukushima's No. 2 reactor could come as soon as late January. Company officials said the new device will be sent inside the pedestal, a structure directly below the core, to investigate the area and hopefully to find melted debris.
The device looks like a giant fishing rod about 12 centimeters in diameter, from which a unit housing the camera, a dosimeter and thermometer slowly slides down. The probe, attached by a cable on the back, can descend all the way to the bottom of the reactor vessel if it can avoid obstacles, officials said.
Two teams of several engineers will be tasked with the mission, which they will remotely operate from a radiation-free command center at the plant.
A simpler predecessor to the pipe unveiled Friday had captured a limited view of the vessel during a preparatory investigation in February. A crawling robot sent in later in February struggled with debris on the ground and stalled in the end due to higher-than-expected radiation, its intended mission incomplete.
The upgraded probe has been co-developed by Toshiba ESS and International Research Institute for Nuclear Decommissioning, a government-funded unit of construction and nuclear technology companies over the past nine months.
See also : https://mainichi.jp/english/articles/20171223/p2g/00m/0bu/010000c
December 22, 2017
Tool for Fukushima reactor vessel probe shown
The operator of the Fukushima Daiichi nuclear power plant has given a media preview of equipment that will be used to investigate the inside of the containment vessel of one of the damaged reactors.
Tokyo Electric Power Company, or TEPCO, showed a tool called a "guide pipe" at a factory in Yokohama on Friday.
The pipe can be extended to 16 meters in length and has a camera and a dosimeter at its tip.
TEPCO plans to use it to get a better look inside the containment vessel of the No.2 reactor.
The operator believes fuel debris, made up of a mixture of molten fuel and broken interior parts, lies at the bottom of the vessel.
In January, workers confirmed the presence of a mass on the floor under the reactor.
But they could not confirm if it was fuel debris because they could not measure the radiation levels there.
In January next year, workers hope to confirm that it is fuel debris by sending in a camera and a dosimeter using the guide pipe.
The government and TEPCO plan to determine which reactor they should remove debris from first and how to conduct the procedure during fiscal 2019, which begins in April.