Removing 20-ton debris from No.3 pool

August 2, 2015

In delicate operation, 20-ton object removed from Fukushima fuel pool

http://ajw.asahi.com/article/0311disaster/fukushima/AJ201508020026

By HIROMI KUMAI/ Staff Writer

Tokyo Electric Power Co. on Aug. 2 removed a 20-ton piece of debris from a nuclear fuel storage pool, a small but critical step in decommissioning the crippled Fukushima No. 1 nuclear power plant.

It was the largest piece of debris left in the No. 3 reactor building’s storage pool, which is holding 566 nuclear fuel assemblies.

The reactor building was heavily damaged by a hydrogen explosion shortly after the Great East Japan Earthquake and tsunami on March 11, 2011, triggered the nuclear crisis at the plant.

The object removed was part of fuel replacement equipment used to load and unload nuclear fuel at the No. 3 reactor. It has prevented TEPCO from removing the nuclear fuel assemblies in the pool to a safer location.

The piece of equipment originally weighed 35 tons, but TEPCO used an underwater cutting device to pare it down to 20 tons.

The utility began lifting the debris shortly before noon. Workers remotely controlled two large cranes, equipped with three specially designed hooks, to pull out the debris while closely monitoring the process with cameras.

The delicate operation required the utmost attention to detail to prevent the debris from touching the pool’s walls. If it had dropped back into the pool, it could have damaged the nuclear fuel assemblies.

The debris was safely placed on the ground after 90 minutes, during which time TEPCO suspended all outdoor decommissioning work at the plant compound in case of an accident.

After removing the smaller debris from the pool, the utility plans to install special equipment on the upper structure of the reactor building to lift out the nuclear fuel assemblies.

TEPCO plans to start the fuel-removal operation in January 2018 at the earliest.

Key debris operation at Fukushima clears way for removal of still-simmering fuel rods

http://www.japantimes.co.jp/news/2015/08/02/national/key-debris-operation-fukushima-clears-way-removal-still-simmering-fuel-rods/#.Vb4hRPnwmos

by Reiji Yoshida

Staff Writer

Tokyo Electric Power Co. succeeded Sunday in safely removing a massive piece of debris weighing roughly 20 tons from the fuel pool of the Fukushima No. 1 nuclear power plant’s damaged reactor 3 building, the utility said.

The operation was considered a major step toward removing the 566 fuel rod assemblies that have remained in the pool since the triple meltdown at the Fukushima plant in March 2011.

Tepco is aiming to remove all of the still-hot fuel assemblies in the No. 3 pool by the end of March 2018.

The debris, originally a piece of equipment used to remove and insert fuel rod assemblies, fell into the pool after a hydrogen explosion ripped through the reactor building on March 14, 2011.

More than four years after the crisis, radiation still remains dangerously high in the area around the pool.

In Sunday’s removal operation, which took just over an hour, workers used two huge remote-controlled cranes to lift the 14-meter-long piece of debris out of the pool.

The risk surrounding the removal effort — given the huge number of fuel assemblies in the pool — meant Tepco halted all other outdoor decommissioning work.

No significant uptick in radiation levels was observed at the plant during the operation, the utility said.

The gigantic tsunami that hit the Fukushima plant on March 11, 2011, knocked out critical cooling functions and led to meltdowns of three of the six reactors, triggering hydrogen explosions that blew up the upper floors of the reactor 1, 3 and 4 buildings.

Tepco has already moved fuel rod assemblies from the pool of the reactor 4 building — considered the most fragile among the damaged structures — to a safer building within the plant’s compound.