Jeremy L. Dillon
RW Monitor
8/7/2015
The Tokyo Electric Power Co. announced on Sunday the successful removal of the “the largest and most complex piece of rubble” from the damaged Unit 3 reactor building at the Fukushima Daiichi site, enabling the clearing of remaining rubble and the rest of the 514 spent fuel assemblies in the pool. TEPCO extracted the facility’s 20-ton fuel handling machine (FHM), which was damaged in the March 2011 accident. According to TEPCO, the FHM was securely lifted from the spent fuel pool and safely brought down on to the ground using two 600-ton cranes with a special hook and clamps. “The successful completion of this complex task is a credit to the hard work and collaborative spirit of many people from many organizations who have worked together,” TEPCO Chief Decommissioning Officer Naohiro Masuda said in a statement. “It paves the way for continued progress and is a milestone in reducing the risk of removing spent fuel assemblies. The workers should take satisfaction in this accomplishment even as we continue the work of decommissioning.”
The removal of spent fuel rods and fuel debris from the spent fuel pools in Units 1, 2, and 3 remains among the largest obstacles at the cleanup. The fuel rods at the units all suffered heavy damage during the accident, resulting in fuel debris, and are not so easily transferred. “Since the fuel melted into a state called debris, it became difficult to apply conventional measures to remove it,” TEPCO said in a report last year. “To deal with this situation, we are planning to conduct the task in parallel with the development of tools and devices for removal, etc. during the decommissioning process, over the next 30 to 40 years.”
TEPCO Makes Progress on Contaminated Water Leakage
TEPCO also announced late last week that it had removed the last of the retained water from the trenches on the seaside of Units 2 and 3. The removal should reduce the risk of water leakage, preventing further contamination of the site. TEPCO had originally tried to freeze the water in the trenches as a way of removing the contamination, but after repeated attempts failed, the company switched to a different strategy involving a special liquid cement while removing the retained water to on-site water storage containers. “One of our most important goals this year is to reduce any risk of water leakage and to prevent the possibility of environment or ocean contamination,” Masuda said in a statement. “Completion of the water removal from the trenches is an important milestone towards achieving that goal. It has been a challenging task and I congratulate our workers on their persistence and their success.”
Water management at the site remains a top priority for TEPCO, which last year announced the launch of its bypass system that diverts groundwater from Fukushima. The bypass system is an attempt to reduce the accumulation of contaminated water by intercepting clean groundwater before it reaches the plant by rerouting it around the plant into the sea. TEPCO also began construction of an ‘ice wall,” which freezes the surrounding soil in an effort to block the flow of groundwater. The strategy also aims to prevent groundwater from flowing into the sea by constructing a steel pipe sheet pile wall on the east side of the site and a subdrain system that will capture underground water and pump the water for treatment. All four systems are part of TEPCO’s three large water management strategies: contaminant removal, contaminant isolation, and leakage prevention.
