Confirmed: 70 to 100% fuel likely melted in No.2

September 27, 2015

Researchers: More than 70% of No. 2 reactor's fuel may have melted

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201509270023

By HIROMI KUMAI/ Staff Writer

More than 70 percent of the fuel may have melted in one of the three reactors at the Fukushima No. 1 nuclear power plant that suffered meltdowns in the wake of the 2011 nuclear disaster, researchers reported on Sept. 26.

The group, which includes researchers from Nagoya University, concluded that it is highly likely that 70 to 100 percent of the fuel has melted in the No. 2 reactor through inspecting the interior using a fluoroscopic device, which utilizes elementary particles called muons.

It was the second time that researchers successfully scanned the interior of the damaged reactors using a fluoroscopic device since a group led by Tokyo Electric Power Co., the operator of the crippled plant, announced the results of its survey inside the No. 1 reactor in March.

In cooperation with the electronics firm Toshiba Corp., the group, led by Nagoya University researchers, has conducted a probe into the No. 2 reactor since last year.

The survey detected few signs of nuclear fuel remaining in the reactor core, in contrast to the No. 5 reactor, which was not affected by the nuclear disaster, triggered by the Great East Japan Earthquake and tsunami in March 2011.

The researchers released their report at a meeting of the Physical Society of Japan in Osaka on Sept. 26.

TEPCO had reported earlier that it is likely that a portion of the nuclear fuel remains in the core of the No. 2 reactor based on the results of its computer analysis.

By HIROMI KUMAI/ Staff Writer

 September 26, 2015

Up to 100% of No. 2 reactor fuel may have melted

http://www3.nhk.or.jp/nhkworld/english/news/nuclear.html

Sep. 26, 2015 - Updated 00:51 UTC+2

A group of researchers says it is highly likely that 70 to 100 percent of fuel has melted at one of the damaged reactors at the Fukushima Daiichi nuclear power plant.

The group includes researchers from Nagoya University. It has been probing the plant's No. 2 reactor since April of last year, using a device that uses elementary particles called muons to see into its interior.

The researchers say the results of their study show few signs of nuclear fuel at the reactor core, in contrast to the No. 5 reactor where fuel was clearly visible at its core.

This led them to believe that 70 to 100 percent of fuel at the reactor has likely melted.

The researchers say further analyses are needed to determine whether molten fuel penetrated the reactor and fell down.

The No.2 reactor is said to have released large amounts of radioactive substances following the March 2011 accident.

Tokyo Electric Power Company, the plant's operator, has estimated that part of nuclear fuel at the reactor remains at its core.

The locations of nuclear fuel will have a significant impact on the process to remove it from the damaged reactors, the most difficult step of the decommissioning work.

The Japanese government and TEPCO plan to scan the No. 2 reactor once again using a different device.

They are also preparing to use robots around the reactor.

The group will announce the results of its study at a meeting of the Physical Society of Japan in Osaka on Saturday.