IAEA to review fuel removal work at Fukushima No. 4 reactor this month

Kyodo

The government said Tuesday that International Atomic Energy Agency experts will visit Japan later this month to study such issues as the just-started fuel removal work at a pool inside a damaged reactor building at the Fukushima No. 1 nuclear complex.

The IAEA mission, to be led by Juan Carlos Lentijo, director of the IAEA Division of Nuclear Fuel Cycle and Waste Technology, will be in Japan from Nov. 25 to Dec. 4. The team will release a summary of its review on the final day, a government official said.

The announcement was made as delicate work by Tokyo Electric Power Co. to eventually remove more than 1,000 fuel assemblies from the spent fuel pool in the No. 4 reactor building entered its second day.

On Monday, workers successfully extracted four unused fuel assemblies from the fuel rack and placed them in a transportation cask also inside the spent fuel pool, filled with water around 12 meters deep.

Once the cask is filled with 22 fuel assemblies, workers will lower it to a trailer and take it to another pool around 100 meters away, which will provide more stable conditions for keeping the fuel cool. It is expected to take about a week to complete the work cycle for the first cask.

Tepco will review the work flow after it finishes one cycle. It has not yet decided when it will start taking out the spent fuel, which is more difficult to handle than unused fuel because it is highly radioactive and emits heat as radioactive elements in the fuel decay.

The pool, located on the top floor of the reactor building, holds 1,533 fuel assemblies, including 202 unused ones. Tepco plans to finish the removal work by the end of 2014.

A fuel assembly is a bundle of fuel rods comprised of zirconium metal tubes with pellets inside. The pellets, made of uranium, serve as the actual fuel for nuclear reactors.

The operation requires extreme prudence, as it is an unprecedented attempt to remove fuel from a building that saw its roof and walls blown up by a hydrogen explosion in 2011 when the nuclear crisis began.

Tepco has cleared away large pieces of rubble that fell onto the upper floor of the reactor building as a result of the explosion and created a huge steel-framed cover to blanket the reactor building.

During the crisis immediately after the earthquake and tsunami of March 11, 2011, reactors 1, 2 and 3 experienced core meltdowns.

The No. 4 reactor only suffered a hydrogen explosion as all of its fuel was stored in the spent fuel pool because it was undergoing periodic maintenance work at the time.

The IAEA team will consist of 19 experts, some of whom have knowledge of how the plant should deal with the buildup of massive amounts of radioactive water, according to the government official.

It will be the second time that Japan has accepted an IAEA review mission on work toward decommissioning the four stricken reactors at Fukushima No. 1.