Status as of 5/27/2011

After suspending pumping of water into the waste water storage facility, the water level in the storage facility dropped 4.8 cm in 20 hours.  TEPCO’s initial investigation did not identify where the radioactive water was leaking.  They have now reported finding the water in another building which is connected to the storage facility by an underground passage.  Currently the pumping of water out of buildings is suspended.

Status as of 5/24/2011

TEPCO analyzed the data and interviewed operators to put together the sequence of events after the March 11 earthquake. They have determined Unit 1 sustained a full meltdown and the molten mass is at the bottom of the reactor vessel.  Units 2 and 3 have damaged fuel and some fuel is melted down but there was always a sufficient level of water in the reactors to prevent a total meltdown.  This analysis is important because it affects the methods which will be employed for maintaining cooling and the subsequent removal of the highly radioactive fuel and materials in the reactor.

The pumping out of the Unit 2 and 3 reactor buildings will be suspended by the end of the week because the onsite storage capacity will be full.  The water processing facility is under construction and expected to be completed by mid-June.  Water continues to be injected into Units 1, 2, and 3.  No plans have been announced for how they will handle the additional water.

Status as of 4/23/2011

The Unit 2 reactor building is mostly intact and as a result the warm water in the spent fuel pool is causing high humidity inside, which is limiting the workers stay time.  TEPCO will be installing a heat exchanger to cool the Unit 2 spent fuel pool to improve working conditions prior to working on the reactor cooling system.

Work is beginning on to reinforce the Unit 4 spent fuel pool.  30 steel supports will be installed below the spent fuel pool.

The MegaFloat structure pictured in the April 20 update below is now moored at the site.  It will be used to store low level waste water.

Status as of 5/18/2011

Today’s status will summarize the work on all the Fukushima Daiichi Units.

The original plan to fill the reactor containment structures with water to a depth high enough to cover the fuel in the reactor vessels has been abandoned because of damage to the containment structures from the hydrogen explosions.  The new plan calls for circulating water from the reactor buildings or containment into the reactor vessel piping which will cool the fuel and then leak out of the reactor vessels to the reservoir of water they are tapping.  The new plan requires continuous pumping of water while the abandon plan required maintaining water level but would not need a continuous injection of water. 

The Unit 1, 2, and 3 reactors contain damaged and melted fuel.  Data is now available for Unit 1 which indicates extensive melting took place when power was lost and the water covering the fuel boiled off.  The cladding and fuel overheated causing it to burn, releasing hydrogen and creating a molten mass which flowed to the bottom of the reactor vessel.  The molten mass melted holes in welded seams at the bottom of the vessel.  The injection of water into the reactor vessel is keeping the molten mass cool.  Because the molten mass continues to produce heat from the radioactive isotopes, cooling will need to continue.  Water continues to be injected into the three reactors at rates between 1800 to 2700 gallons/hour.

Work has begun on the putting in the circulating water system for Unit 1.   They have started work on covering the damaged Unit 1 reactor building with construction fabric.  The reactor building basement is flooded with 12 feet of radioactive water. 

Four workers entered the Unit 2 reactor building for the first time since the earthquake.  They did a survey of the building to map the radiation levels in order to plan the next tasks.  The basement of the building and a piping tunnel are flooded.  

130 tons (34,000 gallons) were pumped out of the Unit 3 reactor building yesterday lowering the level about 0.5 inches.  There is about 56 inches of water remaining.  Water was found to be leaking into the ocean on Monday.  There was no status on whether the leak has been stopped. TEPCO has indicated the silt barrier for capturing some of the radioactive contaminants is not working.  They are continuing to use zeolite to absorb the cesium.

The hydrogen explosion in the Unit 4 reactor building has now been attributed to hydrogen from Unit 3 which entered the building via a common duct.  A video of the fuel in the Unit 4 spent fuel pool does not show the expected damage to the fuel which could have produced the amount of hydrogen needed to cause the explosion.  The water level in the Unit 4 spent fuel pool is being maintained by the injection of water every other day. 

Water is being pumped from the Units 5 and 6 buildings to makeshift tanks.  This water is not highly radioactive.

Status as of May 16, 2011

TEPCO has concluded that most of the fuel in the Unit 1 reactor is damaged.  The original estimate of 55% core damage was low based on the data now available.  The fuel is at the bottom of the reactor vessel and the heat from the molten mass melted holes through the bottom of the vessel at welded seams.  The damaged fuel is being cooled by the continuous water injection into the vessel and is being maintained below 100°C.  On Sunday the injection was increased from 8 to 10 tons/hour (2100 – 2600 gal/hr) to quantify the cooling affects.  The increased flow decreased the temperature of the fuel at the bottom of the vessel by 15° C.  The plan to submerge the fuel by filling the reactor containment has been scuttled because of the leaking water.  Two alternate plans are being considered.  Both will continue to inject water into the reactor vessel, but the first would circulate the water already in the reactor containment through a heat exchanger and then into the reactor.  The second would draw the water from the flooded reactor building which has accumulated over 12 feet of water in the basement.

Radioactivity in water samples from the inlet bay near Unit 3 are on the rise again indicating leakage from the plant.  Radioactive cesium was measured to be 2400 times above the allowable limits.  TEPCO also reported Iodine-131 in water samples taken near the Unit 2 intake at 2,100 times the legal limits.  We will be watching for an explanation of this sample because the radioactive iodine from the fuel should have decayed to negligible amounts since the March 11 earthquake shutdown the reactors.  

Status as of 5/12/2011

The flooding of the Unit 1 reactor containment has reached a level 3 feet below the bottom of the fuel in the reactor.  When the final 150 tons of water was added to cover the fuel, the level gauge did not show an increase.  TEPCO initially thought the level gauge was not reading properly, but has since seen a rise in the water level in the reactor building and determined the gauge to be working.  This water level is too low to provide the stable core cooling which was planned.  The Unit 1 reactor containment is leaking into the reactor building.  A revised plan is expected to be announced next week.  Work in the Unit 1 reactor building has been limited by high radiation levels which limits the time workers can spend on a task.  They have been using lead blankets for shielding between the radiation source and the worker, a standard industry practice.

Two days ago the water levels in the Unit 3 turbine building started to drop.  On Thursday they found the leak, water was flowing through an electric cable conduit into a pit which eventually flowed into the inlet bay.  The leak has been plugged.  The volume of highly radioactive water which was released was not reported.

Japan’s Prime Minister has called for the shutdown of the Hamaoko nuclear plant because it does not meet the current standards for earthquake and tsunami protection.  The plant will need to be brought up to the current standards before it can be restarted.  There are 5 units at the site, but the 2 oldest units have already been retired.  Unit 3 was already shutdown for maintenance.  Units 4 and 5 are now being shutdown.  This will create a electric deficit for the utility which owns the plant which will need to be addressed.

Status as of 5/9/2011

The air in the Unit 1 reactor building has been filtered enough to allow workers to enter the building with respirators rather than supplied air tanks.  TEPCO has posted a video which shows the air filtration system.  http://www.youtube.com/watch?v=6VtwFsKT93s   Radiation surveys are being taken to map out the radiation levels within the building.  The radiation levels will determine the time and precautions workers will take when working in an area.  One task for today is to calibrate the gauge which provides an indication of the reactor containment vessel water level.  They will be inspecting the conditions of pipes and valves which will be used for to cool the reactors with the cooling system being built.

A video of the Unit 4 SFP has also been released.  The video was taken with a submersible camera which was attached to the end of the boom which is injecting water into the pool .  It shows the debris which has settle on top of the fuel racks.  http://www.youtube.com/watch?v=qCY0xQRZ1UY  At 41 seconds, the bales on the top of the fuel assemblies are being videoed.  The surface temperature of the pool is about 81° C.

Status as of 5/5/2011

Workers entered the Unit 1 reactor building for the first time since March 11 when the tsunami and subsequent hydrogen explosion damaged the roof of the building.  The area they entered provides access to the pipes which inject water into the reactor.  The workers were setting up air filtering equipment and ducting to begin cleaning the contaminated air.  The workers were wearing air packs and protective clothing and were limited to working for 10 minutes before reaching radiation exposure limits.  Several teams were needed to complete the equipment installation.  The air will be filtered for several days to remove the particulates from the air in order to make the areas safer for the work of connecting heat exchangers to the pipes leading to the reactor.

Status as of 5/4/2011

Updates on evolutions within the plant are not being reported.  We can only assume they are continuing to pump water from the tunnels.

The radioactive cesium levels from the inlet bay at Daiichi are not trending down as expected.  Cesium levels should be trending down because of water dilution and the zeolite absorber placed in the bay last week.  The zeolite was expected to concentrate the cesium by absorbing it.  TEPCO will be lowering another canister of zeolite with a pump to circulate the water through the absorber in an attempt to capture more cesium.  The concentration of cesium may not be changing because contaminated water continues to be leak from the site.  Below is a picture of the inlet bay.  The silt fence installed to capture sediment can be seen floating across the bay.   

Inlet Bay (credit: TEPCO)

Status as of 5/1/2011

No gauges or instrumentation were built into the reactor containments to provide the water level for flooding the fuel so TEPCO has a plan to install a gauge.  An air filtering system is being installed in the Unit 1 reactor building to reduce airborne contamination.  This will make it safer and increase the stay time for workers.  Plans call for installing a water level gauge and a heat exchanger for removing the heat in the water.

Government officials are facing more protests about the situation.  In response to raising the allowable radiation level for children in the affected areas parents delivered a bag of contaminated soil to the parliament.  A top level advisor resigned in protest to the government actions.  A group of shareholders proposed a motion calling for TEPCO to close all its nuclear plants.