Dry removal recommended by decommissioning commission

August 31, 2017

Group: Water plan to remove Fukushima fuel ‘not viable’

http://www.asahi.com/ajw/articles/AJ201708310042.html

By KOHEI TOMIDA/ Staff Writer

A decommissioning organization on Aug. 31 formally recommended bypassing a safety measure to remove melted nuclear fuel from crippled reactors at the Fukushima No. 1 nuclear plant.

The Nuclear Damage Compensation and Decommissioning Facilitation Corp. (NDF) urged the central government and Tokyo Electric Power Co. to use the “airborne method” in which the melted fuel is removed even when the water level in the reactor containment vessel is kept low.

Proposals have been made to fill the containment vessels with water to restrain the spewing of radioactive materials during the fuel removal process.

But the NDF said that method is currently not viable because of the difficulties in patching up the holes in the containment vessels.

The government and TEPCO are expected to decide on a fuel removal method in September and confirm the specific steps next fiscal year.

The removal of equipment and other structural objects in and around the reactors must be completed before work can start on taking out melted fuel that remains in the pressure vessels.

The nuclear fuel that has seeped through the pressure vessels and landed at the bottom of the containment vessels will be the first to be removed.

Work will also have to be done to develop a robot arm that can remove fuel from the side of the containment vessel.

Under the current schedule, removal of the melted fuel will start at one of the three, No. 1 to No. 3, reactors of the Fukushima No. 1 plant in 2021.

However, officials still do not know the exact location of the melted fuel in the reactors.

Hajimu Yamana, NDF president, pointed out there would likely be a need to combine various methods instead of pushing through with one specific procedure to meet the scheduled deadline.

August 31, 2017

Dry method' recommended to remove nuclear debris

https://www3.nhk.or.jp/nhkworld/en/news/20170831_18/

A Japanese government body has officially recommended a method known as "dry removal" to retrieve nuclear fuel debris from the damaged Fukushima Daiichi power plant.

The Nuclear Damage Compensation and Decommissioning Facilitation Corporation submitted the recommendation to the government on Thursday. It said the method should be the first option for all 3 reactors that suffered meltdowns.

Fuel in each of the 3 reactors is believed to have melted in the 2011 accident and combined with the reactor structures to form fuel debris. Most of the fuel is considered to have melted through surrounding pressure vessels and accumulated at the bottom of the containment vessels.

Removing the debris is considered the biggest hurdle to decommission the reactors as it gives off high levels of radiation.

The Corporation initially considered another method that involved filling the vessels with water to block high levels of radiation. But the body says it is difficult to repair the containment vessels damaged by the accident.

The body says that nuclear debris at the bottom of the containment vessels should be retrieved from the side of the vessels, but debris left at the bottom of the reactors' pressure vessels should be taken out from the top. It also says combinations of other methods should be considered in the future.

Hajimu Yamana, head of the Corporation, said it plans to begin the work to retrieve nuclear fuel debris in 2021, and that there has been no reason for changing the schedule so far.

The Japanese government and Tokyo Electric Power Company will review the schedule for decommissioning the reactors based on the body's recommendation. They will announce in September which method they will choose to remove debris from each of the 3 reactors.