6 Years after Fukushima disaster, robots continue search for radioactive fuel — Bloomberg, Insurance Journal; The Japan Times

” The latest robot seeking to find the 600 tons of nuclear fuel and debris that melted down six years ago in Japan’s wrecked Fukushima Dai-Ichi power plant met its end in less than a day.

The scorpion-shaped machine, built by Toshiba Corp., entered the No. 2 reactor core [on Thursday, Feb. 16] and stopped 3 meters (9.8 feet) short of a grate that would have provided a view of where fuel residue is suspected to have gathered. Two previous robots aborted similar missions after one got stuck in a gap and another was abandoned after finding no fuel in six days.

After spending most of the time since the 2011 disaster containing radiation and limiting ground water contamination, scientists still don’t have all the information they need for a cleanup that the Japanese government estimates will take four decades and cost 8 trillion yen ($70.6 billion). It’s not yet known if the fuel melted into or through the containment vessel’s concrete floor, and determining the fuel’s radioactivity and location is crucial to inventing the technology needed to remove it.

“The roadmap for removing the fuel is going to be long, 2020 and beyond,” Jacopo Buongiorno, a professor of nuclear science and engineering at the Massachusetts Institute of Technology, said in an e-mail. “The re-solidified fuel is likely stuck to the vessel wall and vessel internal structures. So the debris have to be cut, scooped, put into a sealed and shielded container and then extracted from the containment vessel. All done by robots.” … ”

Continue reading about the fuel-removal status of Fukushima No. 1’s Units 1 through 3.

by Emi Urabe and Stephen Stapczynski, Bloomerg via Insurance Journal

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Read a similar article by The Japan Times

Japan’s $25 billion nuclear recycling quest enters 28th year — Bloomberg Business

Spent-nuclear fuel issues plague restarts — The Japan Times

” Spent fuel at the Hamaoka nuclear power station in Shizuoka Prefecture could exceed the capacity of storage pools some two years after the plant is restarted — much sooner than the previously assumed eight years, according to sources.

The faster pace is because the storage pools for reactors 1 and 2 at the Chubu Electric Power Co. plant will be removed from the complex’s total storage capacity following the decommissioning of the two units.

Previously, Chubu Electric planned to continue using the two reactors’ storage pools. The operations of the two reactors ended in 2009.

Last month, four power suppliers, including Kansai Electric Power Co., decommissioned a combined five aging reactors, significantly reducing storage pool capacity.

As of the end of March, the Hamaoka plant’s storage capacity fell by 440 tons in the past six months to 1,300 tons, reflecting the exclusion of the reactor 1 and 2 pools, according to Chubu Electric’s semiannual report to the Federation of Electric Power Companies. Meanwhile, the amount of spent fuel stored at the plant stood at 1,130 tons.

If the remaining three reactors at the plant are brought back online, the amount of spent fuel would exceed the storage capacity in 2.3 years, compared with the eight years estimated before the company’s decision not to use the reactor 1 and 2 pools.

Of all 15 domestic nuclear plants that operators are seeking to restart, storage space capacity appears to be lowest at the Hamaoka plant.

Only four of the plants have more than 10 years before they run short of capacity, including Hokkaido Electric Power Co.’s Tomari plant, which has the longest time, at 16.5 years. The three others are Tohoku Electric Power Co.’s Higashidori plant, with 15.1 years, Hokuriku Electric Power Co.’s Shika plant, with 14.4 years, and Kyushu Electric Power Co.’s Sendai plant, with 10.7 years.

All nuclear reactors in Japan are now offline.

Some nuclear plant operators are working to increase their spent-fuel storage capacities while pinning hopes on fuel recycling at Japan Nuclear Fuel Ltd.’s facilities in the village of Rokkasho, Aomori Prefecture.

Chubu Electric has applied to build a dry-cooling storage facility at the Hamaoka plant to boost its total capacity to store spent fuel. It hopes to put the facility into operation in fiscal 2018 if the plan is approved by the Nuclear Regulation Authority.

A Chubu Electric official said storage capacity prospects remain unclear at the plant because it is uncertain if any reactors will be allowed to restart. ”

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​Fukushima has 9 days to prevent ‘unsafe’ overheating — RT

” Fukushima operator TEPCO has been forced to switch off the cooling system at mothballed Reactor Unit 5, after it was discovered that it had been leaking water. In nine days, if the system is not repaired, temperatures will exceed dangerous levels.

Engineers have discovered that 1,300 liters of water leaked from a cooling system intended to stabilize the temperature of the spent fuel at the Reactor Unit 5, which was offline but loaded with fuel rods when the plant was damaged by the earthquake and tsunami in March 2011.

The source of the leak was a 3 mm-diameter hole near a flow valve, a statement published by the Japanese energy giant on Sunday asserts. However it is unclear from company data if the location of the opening has been discovered, or whether it was calculated with flow measurements.

At the time when the cooling system was switched off at around 12pm on Sunday, the temperature in the pool in which the rods are submerged was 23C but started increasing by 0.193 degrees per hour, TEPCO says.

If no new cold water is pumped in at such rate it will reach the dangerous threshold of 65C by the midpoint of the month in roughly 9 days.

Such temperatures, which have not been routinely seen at the plant since the failing of the cooling system in the immediate aftermath, would increase the possibility of dangerous reactions and further radiation leaks in the plant.

TEPCO however says that currently, there have been no abnormal readings anywhere in the plant.

Since TEPCO is using seawater for many of its cooling needs at the power plant, it has previously encountered heightened levels of corrosion, in sensitive equipment. The cooling system at various reactors has also been beset by calamities – from rats short circuiting the control panel and forcing a blackout, to an employee “accidentally” switching it off, though all were resolved before rod pools overheated.

At the same time, TEPCO is struggling to deal with ever-increasing volumes of contaminated water which is being stored in hundreds of tanks at the facility and frequently leaking and contaminating the soil beneath it. And the much publicized plan to stop contaminated water from leaking into the sea by building an ‘ice-wall’ and freezing soil and water around the facility is not working as well as Japanese officials had hoped. ”

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Fukushima news 4/25/14: Tepco pleads for help; Is Fuku radiation a “state secret”? — multiple sources, NHK World

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Fukushima Unit 4 fuel removal risks — The Fukushima Project

” TEPCO plans to begin removing spent fuel from unit 4 this fall. This effort only came about after ongoing public outcry over the danger the damaged pool posed. The effort was accelerated and the defueling building installed this spring and summer. This will be the first of some very high risk work at the plant but is little understood by the public. … “

Read this article that explains how the fuel rods will be removed, the stability of the building, spent fuel pool and fuel and the various risks involved.