The operator of the Fukushima Daiichi nuclear complex in Japan restarted on September 10 in a bid to retrieve a small amount of melted fuel from one of its stricken reactors after its first attempt last month was suspended due to setup complications, Report informs referring to Kyodo News.
The attempt to extract the fuel by Tokyo Electric Power Company Holdings Inc. is the first since the complex was damaged following a massive earthquake and tsunami in March 2011 and comes after three suspensions since the initial plan was scheduled to launch around three years ago.
TEPCO put the trial extraction on hold on Aug. 22 after finding the five pipes to be used to insert a retrieval device into the No. 2 reactor's containment vessel had been set up incorrectly.
After confirming that the pipes are now installed in the correct order, the company passed the device through an isolation valve, intended to block radioactive material, in the morning.
It plans to insert the device, which extends up to 22 meters, into the containment vessel to collect less than 3 grams of debris. It is expected it will take around two weeks for the probe to reach and then extract the debris.
The task of retrieving melted fuel remains a serious challenge in the decades-long decommissioning plan for the Fukushima Daiichi complex, with an estimated 880 tons of fuel debris remaining in the Nos. 1, 2 and 3 reactors.
The extraction of the radioactive material will be conducted remotely, but no decision has been made on specific methods to retrieve the entire amount.
An investigation following the suspension of the trial extraction last month found that TEPCO and contractor Mitsubishi Heavy Industries Ltd. had outsourced the preparation of the pipes and had ultimately failed to check the order in which they had been set up.
TEPCO later drew up countermeasures to prevent another mishap, including a reevaluation of its manual and instructions for employees to inspect the tasks.