TOKYO >>Tokyo Electric Power Co. Holdings, Inc. has decided to retrieve the sandbags that were used to lower the radiation level of water that was contaminated while cooling down the reactors at the Fukushima No. 1 nuclear power plant following the 2011 meltdown.

The plan aims to reduce workers’ exposure to radiation, which would allow the decommissioning process to be sped up. The company plans to start the sandbag removal by February.

Zeolite, a mineral used to adsorb radioactive cesium, was placed in about 1,300 sandbags — weighing a total of about 26 tons — and placed on the basement floor of two facilities near the reactors.

Following the 2011 Tohoku earthquake and tsunami, there were meltdowns in three reactors. The enormous amount of water used in an attempt to cool the reactors became highly contaminated and was stored in the basement floor of the two buildings. Because the water was so highly radioactive, zeolite sandbags were placed in the water to lower the radiation level.

After being submerged in the contaminated water for years, the sandbags have degraded and are now dangerously radioactive themselves.

The level of radiation on the surface of the sandbags measures a maximum of 4.4 sieverts per hour, which is enough to kill 50% of people exposed to it for one hour. The high radiation levels have been a huge obstacle in the decommissioning work and the retrieval of nuclear fuel debris in the reactors.

TEPCO has been developing two types of robots for retrieving the sandbags. They are currently in the final phase of testing conducted in the prefecture, and TEPCO has decided they are ready for use.

For the retrieval, a remote-controlled robot will go into the water to tear the bags and release the zeolite. Then, beginning fiscal 2025, another robot will draw the zeolite with contaminated water through a pipe to the buildings’ upper floors and into metal containers that can shield against radiation. The containers will be stored temporarily in elevated areas on the plant grounds.

Activated charcoal, which was used in other sandbags to absorb oil spilled during the accident, will be stored in containers as well.

Although the work is scheduled to be completed by fiscal 2027, the decision of how to ultimately dispose of the containers has not yet been made.

TEPCO succeeded in a test retrieval of a piece nuclear fuel debris weighing 0.7 grams (.02 ounces) at one of the reactors in November. Removal of the debris is deemed the most difficult task in the decommissioning process.