Photo/Illutration The No. 2 reactor building at the Fukushima No. 1 nuclear power plant in Okuma, Fukushima Prefecture (Asahi Shimbun file photo)

Tokyo Electric Power Co. on Aug. 22 again postponed a long-awaited test to remove melted nuclear fuel from the stricken Fukushima No. 1 power plant, citing a mistake in equipment installation.

The removal work was scheduled for later that day at the plant’s No. 2 reactor. TEPCO said it has not yet decided on a new starting time.

According to the utility, preparatory work began at around 7:30 a.m. on Aug. 22. However, TEPCO later discovered that equipment for the test was installed in the wrong order.

TEPCO’S plan was to open an isolation valve, insert a simple “fishing rod-type device,” and move it on a path toward the reactor containment vessel via remote control.

Once in the containment vessel, the tool would extract up to 3 grams of fuel debris over a period of about two weeks, according to the plan.

But work was halted because of the possibility that the device may not pass through, the company said.

TEPCO said no radiation leaks have been confirmed as a result of the opening of the isolation valve.

The radiation level inside the containment vessel of the No. 2 reactor is several tens of sieverts per hour, enough to kill most people within a few minutes.

The only way to remove the fuel debris is to use a remote-controlled robot. This is expected to be the most difficult part of the decommissioning process of the plant, which is expected to take several decades to complete, according to TEPCO.

An estimated 880 tons of melted fuel debris accumulated at the plant’s No. 1, No. 2 and No. 3 reactors following the Great East Japan Earthquake and tsunami in March 2011.

The central government and TEPCO had planned to begin removing the debris from the No. 2 reactor in 2021 using a robotic arm developed with government funds.

But work was postponed three times due to technical problems, including a lack of precision of the robotic arm.

(This article was written by Nobuyuki Takiguchi and Keitaro Fukuchi.)

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