Status May 21, 2012

Status May 21, 2012

Work has just begun on the cover for the Unit 4 building.  To date only the Unit 1 cover has been erected.  The Unit 3 and 4 covers were awaiting completion of debris removal before proceeding.

Fukushima has multiple potential disasters which can lead to releasing radiation if another large earthquake/tsunami should hit in the next few years.  The Unit 4 building sustained substantial structural damage and the fuel pool has the largest inventory of fuel assemblies.  The pool received external cooling from the fire hoses during the first months after the earthquake.  One of the first actions after gaining access to the area was to shore up the fuel pool with 30 steel supports.  They continue to filter the water in the spent fuel pool to remove the salt water introduced to the system.

The challenge of remediating all the damage at Fukushima requires untested solutions.  There are 3 reactors with damaged fuel which has leaked out of the reactor vessel into the drywell. In 2 cases the drywell appears to be damaged, so the highly radioactive molten mass cannot be shielded via flooding.  The Unit 3 building is still open to the elements and debris needs to be removed.  Also, there is fuel in each of the 3 associated spent fuel pools.  Plans are being formulated on how the damaged reactor vessels can be accessed in order to remove the damaged fuel.  They will also need to gain access to the area below the reactor vessel to remove the fuel which melted through the vessel.  This is a procedure which has never been performed or planned.

They are storing a huge volume of highly radioactive water containing cesium and strontium in temporary tanks on site.  The water is being cleaned and recirculated for cooling, but the pumping and piping systems were quickly assembled and are prone to break downs and leaks. If a leak occurs the risk of runoff into the ocean is high.  Since the buildings are not sealed the inventory of water continues to increase when it rains.  The basements of several buildings are flooded with contaminated water.    

Removing the fuel from the Unit 4 pool requires substantial infrastructure repairs.  A 100 ton crane is needed to lift the fuel storage casks used for removing the fuel, but they still need to clear the debris which sits on top of the fuel.  The debris includes the crane which would normally be used to place the fuel into the storage casks.   The support systems for evacuating water from the cask after loading are probably damaged because wiring and motors have been water logged.    

The plan and work to cleanup Fukushima will take decades to complete.  The risk of a large earthquake and tsunami incurring substantial damage and releasing radioactivity into the environment will be there all the time.

Status April 2, 2012

A full year has passed since the tsunami wiped out the Fukushima plant.  Water continues to be treated and circulated into the reactor and reactor containment vessel to maintain the damaged fuel in a stable state.  The water pumping, storage, and recirculation system continues to have breakdowns and leaks.  On March 26, a leak from a storage tank was found.  Before the leak was stopped an estimated 80 liters of water containing strontium 90 had entered the ocean.  To prevent the spread of the contaminated sediment in the ocean around the plant, the seabed is being covered with a layer of cement.

The plans for removing the damaged fuel from the Units 1, 2, and 3 are being formulated.  Recently, an endoscope was inserted into the Unit 2 reactor containment vessel to determine the water level in the vessel.  The water level was found to be 0.60 meters, substantially lower than the 3 meters they expected.  The lower water level indicated damage to the containment vessel is greater than anticipated which further complicates the task of removing the highly radioactive damaged fuel because raising the water level is integral to the plans for removing the debris.

The structure which encases the Unit 1 reactor building has been completed.  Debris within the damaged building has not been removed.  Removal of debris from the Units 3 and 4 reactor buildings is progressing with completion expected at the end of 2012 and mid 2012, respectively.  The method for removing the fuel in the Unit 4 spent fuel pool is being determined.  There is an urgency to remove the fuel because the building sustained structural damage so there is a risk of the further damage to the pool in the event of a large earthquake.  Usually the spent fuel pool crane is used to remove fuel, but the crane was damaged and is contributing to the debris in the building.

Some towns around the Fukushima had been evacuated are now safe for habitation.  Most people have left the area and many are concerned about the residual contamination and are staying away.