Fukushima Daiichi NPS Prompt Report 2015

Safe extraction of largest piece of rubble came after extensive preparation and marks major step forward in removing the fuels

FUKUSHIMA, August 2 - After months of careful preparation, workers at Fukushima Daiichi Nuclear Power Station today successfully completed removal of the largest and most complex piece of rubble from the severely damaged Unit 3 reactor building: the facility's fuel handling machine (FHM). The 20-ton 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 or clamps.

When the Unit was operating prior to the March 2011 accident, the FHM was used to move nuclear fuel assemblies within the reactor building, move them into the reactor core, and move spent fuel assemblies from the reactor to the spent fuel storage pool. But along with the rest of the building, the FHM was severely damaged in the accident, and had to be carefully removed without causing further damage to the spent fuel pool or to the fuel assemblies within it.

Removal of the large piece of machinery clears the way for removing the remaining rubble and the rest of the 514 spent fuel assemblies in the pool.
The milestone was hailed by Chief Decommissioning Officer Naohiro Masuda, who praised his workers: "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," he said. "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."

Major Preparations

The FHM had been the largest single piece of rubble remaining inside Unit 3.
To remove it safely, TEPCO conducted the  extra precautionary
measures:
* Preventing oil leakage from FHM with preparation of oil absorption material
* Adapting hooks or clamps to lift FHM with fail-proof mechanisms
* Operator training in FHM lifting mock-up tests
* Preparing the operational procedures for lifting FHM
* Preventing dust scattering by sprinkling water or anti-scattering agent Further risk management measures were also taken in case of water leakage from the pool when FHM were to come in contact with the pool gate:
* Adding a water injection function to the pool
* Preparing to stop drain route and to pump up any leaked water
* Regulating all operations at the site to give priority on FHM lifting