Status as of 6/29/2011

After a couple of attempts to begin recirculating the processed water, it appears all the piping leaks have been fixed.  They are now injecting a mix of processed water and fresh water into the Unit 1, 2, and 3 reactors for cooling. 

Construction of the structure around the Unit 1 reactor building has begun.  A construction crane is now in place for lifting a steel framework which is being preassembled offsite.  Panels of one millimeter-thick polyester fiber panes will be attached to the frame.  The structure will be about 162 feet high and is expected to be completed by late September.

Status as of 6/27/2011

Water from the water treatment plant was injected into the reactors for one and a half hours before the discovery of leaking pipes halted the recycle.  The original schedule had anticipated the recycling would be working by mid June.  An estimated 110,000 tons of water has collected in the basements and tunnels in the plant and 1850 tons has been processed.

Status as of 6/20/2011

The water treatment plant was started on Friday, but was stopped after 5 hours because a component reached its limit for radioactive contamination much faster than expected.  The contaminated water is to undergo three processes, the first separates the oil and water, the second reduces the radiation by absorbing the cesium, and the third removes the salt and other impurities.  The processed water will be stored and eventually used to cool the reactors.  The oil in the water is from the machinery which is in the basements of the flooded buildings.  The salt is from the seawater which was injected into the reactor for several days following the earthquake until a supply of fresh water could be obtained.  The cesium and other radioactive materials are from the damaged fuel and appeared to be at concentrations higher than TEPCO anticipated.  While it is expected that the water treatment plant will concentrate radioactive materials, they need to monitor the radiation level in order to avoid the problem of the ‘filter’ becoming too radioactive to be handled and disposed of properly.

The Unit 2 reactor building doors were opened to reduce the humidity in the building.  Efforts to cool the spent fuel pool apparently did not remedy the situation previously reported May 23.  The humidity was at 99%.  They want to reduce it to below 70% to create better working conditions.  

Question: What is the difference between a nuclear melt down and a melt through? What are the implications?

There is a bit of a difference in that a melt through is where the fuel melts through the lower core plate and through the lower head of the pressure vessel into the primary containment.  It makes clean up a bit more challenging.  There may be some additional releases to the environment.  However, there is nothing necessarily catastrophic about this problem.  It's a bit like the difference in a turbine explosion of having all the blades contained, or a few actually being ejected past the engine containment.  Either way, your day is going to suck.   This is not the nuclear equivalent of a disk explosion.

There is actually some benefit to having some melt through because the fuel is now spread out and you have a larger surface to volume ratio allowing more cooling potential of radio nuclide decay heat.   The fuel that falls to the bottom of containment is also under water and in contact with a huge heat sink.  Part of the trick to cooling the fuel is lots of wetted surface area.

See the diagram below.  The reactor pressure vessel (brown) is inside the primary containment (yellow).  Leaking out of the reactor vessel does not mean being released to the environment.  Assuming the primary containment is still substantially or completely intact, melting through the reactor vessel into the drywell should not cause much additional release to the environment.

The primary containment is protected from steam overpressure by venting into the Torus which is partially filled with cold water.  The steam released from the RV into containment during an accident is vented underwater in the torus and condenses reducing its volume and controlling pressure in the primary containment.

Status as of June 16, 2011

The water processing facility is undergoing final testing and could start operations by tomorrow.  After processing, the radioactivity in the water should be reduced between one-1000^th and one-10,000^th.  It will then be transferred to makeshift tanks at the plant and be used for cooling the fuel.  TEPCO estimates more than 110,000 tons of radioactive water has accumulated and will need to be processed.

TEPCO is also working on installing a system to clean the water in the intake bay.  It is pumping the water through zeolite to capture the radioactive cesium which has escaped into the bay.

Assembly of the framing which will support a polyester fabric for Unit 1 reactor building has begun.  The frame is 120 ft x 120 ft x 150 feet high.  After it is complete it will be lifted and placed over the damaged building then the fabric will be put into place.

Status as of June 8, 2011

Testing of components in the facility for processing the radioactive water has begun.  June 15 is the target date for it to begin operations.  The facility will remove the radioactive cesium and flocculate other radioactive substances with a capacity of 1200 tons/day.  The plant is collecting 500 tons/day from the constant injection of water into the reactors.  The current inventory of water for processing is 105,000 tons.  Without any additional water processing taking place, it will take over 100 days to process the water already collected.  Some of the processed water will be injected back into the reactor, but there will be a surplus of processed water which will need to be stored. 

Remote controlled equipment continues to be used to cleanup debris on the site.  The debris needs to be surveyed for radioactivity because when hydrogen explosions scattered contaminated materials from the reactor buildings.  There are guidelines for the disposal of radioactive materials which are based on the level and type of radioactivity which makes the cleanup effort more difficult.   

Status as of 6/2/2011

The water level in the Unit 2 and 3 tunnels is 28 cm and 24 cm from the top of the tunnel and rising.  They are considering using the basements of a couple of buildings for additional storage.  Earlier in the week Fukushima experienced a typhoon, so additional water entered into the damaged buildings.  The water processing facility is still a couple of weeks away from being ready.  Groundwater surveillances have been increased to determine whether any of the buildings are leaking radioactive water.

A heat exchanger has been installed for cooling the Unit 2 spent fuel pool.  The temperature of the pool is down to 58°C.  The lower temperature will reduce the humidity in the Unit 2 reactor which needed to be lowered to facilitate working within the building.

It was estimated that cleaning up Fukushima Daiichi and the surrounding area would cost $250 billion over 10 years.  The estimate included $54 billion for buying all the land within 12.4 miles of the plant.  This indicates the radioactive isotopes released from the plant have contaminated the land and people living in the area would receive levels of radiation in excess of allowable limits