Fucking Fukushima Daiichi Reactor 4’s Fuel Pool Is a Fucking possible Extinction Fucking Issue for every Fucking Person in the Whole Fucking World and the Fucking MainstreamMedia is mute on the whole subject The world needs to get mad real FUCKING mad right now and demand our Fucking defacto leaders do something instead of trying to fuck us!!! But maybe this is the biggest FUCK ever against Mankind???

PART III

Fukushima Nuclear Power Stations I and II

Explosions at Daiichi Reactor Units #1 and #3  [March 12]
Third Blast and Fire at Daiichi Reactor Unit #2
Reactor Vessel Bottom Likely Penetrated,
Leak of Nuclear Material Possible  [March 14]
Explosion and Radioactive Fire at Unit #4
near and at Spent Fuel Pool  [March 14]
Desperate Measures in Helicopters Unsuccessful
and Fire Trucks Dumping Water onto Spent Fuel Pools   [March 17]
MOX Fuel Concerns Spent Fuel Pool Concerns

Battle for Daiichi Is Just Beginning
  [March 16]
Sand and Soil to Smother Spent Fuel Rods   [March 18]
Sandbacks to Hold Back Radioactive Water in Trench  [March 29]
World’s Largest Concrete Pump Dispatched to Japan  [March 31]
Sawdust, Shredded Newspaper, Diaper Chemicals Fail to Plug Leak  [April 3]
Cars, Whole Houses, Shoes with Feet, Tsunami Debris Floats Towards US  [April 9]
Prime Minister’s Message to the Nation 7 PM PT March 14
Fukushima Nuclear Reactor Problem Explained (CNN) March 14
TEPCO Evacuates worker from Daiichi, including the Last Fifty
then 50 workers returned after 45 minutes as radiation levels fell [March 15]

Daiichi Units #5 & #6 Heating Up  [March 15]

NASA Satellite photos [more]
show devastation in Japan, before and after [March 12]
Nuclear Disaster Eclipses Three Mile Island
Up to Six Reactors Have Problems  [March 16]
New Power Line to Daichii Nearly Complete
to Run Cooling Pumps, Valves, and Plant Controls  [March 17]
Power Lines Connected [March 18]
Micro-Helicopter Videos of Unit #4 April 16
Estimates of Exposure Define US Evacuation Zone  [March 25]
Massive Ground Water Contamination    [May 5]
Three Simultaneous Chernobyls — Almost   [June 1]

Chaos Could Come with Rice Harvest Season 3/15 plume [July 1]
Meltdown:  What Really Happened at Fukushima?  [July 2]
Prof Tatsuhik Kodama, Tokyo U.  "What Are You Doing"  [July 28]
The Explosive Truth Behind Fukushima’s Meltdown  [August 17[
Why Radiatioactive Isotopes Continue to Spread to Tokyo  [October 27]
Encrusted Salt Buildup in Reactor #1 & 2
BWR Design Flaws [Sept 1]
GE Hitachi:  35 US Reactors Could Fail in Quake [Sept 30]
Fukushima Plant Status Report, Nov 2011
Fukushima, Total Cost [Dec 2011]
Fukushima Health Issues and Nuclear Proponents NRC, AEC, IAEA [Feb 2, 2012]
New Containment Flaw Identified in BWR Mark 1 [Feb 6, 2012]
A Pool Crack, rather than Pool Collapse, Can Be the End of Tokyo [Mar 10, 2012]
Fukushima:  The Crisis Is Not Over [Mar 10, 2012]
German TV:  Armageddon if Spent Fuel Pool #4 Collapses [Mar 25, 2012]
Daiichi Tsunami Horror Daiichi Worker Stories Tourists
Health Effects from Acute Radiation Exposure  [2]  [chart]
Fukushima 1 Daiichi Power Station
Fukushima 2 Daini Power Station stable
Fukushima 1 Daichii BWR Design
Active vs Passive Backup Reactor Cooling
Japan’s Incompatible Power Grids [50 hz and 60 hz]
Fukushima Nuclear Accident Update Log  [full]
Before quake, Japan’s Nuclear Plant was a Source of Hope
Tsunami Warnings Written in Stone, Saved Some
Video from Car trapped in Tsunami
Fukushima’s Hawaii Girls on Tour to Promote Safety of Resort
Fukushima on the Mississippi
Related:  The Bomb Plant  [MOX fabrication facility]
Battle of Chernobyl
After the Nuclear Apocalypse [relevant movie]
Fukushima Wind and Temperature Forecast
Live Streaming NHK World TV [English]
Daiichi
                  flood

Outside the Daiici plant as the tsunami flood swept arouind the complex [before]

Daiichi 1-4

Daiichi Reactor Units #1 to #4 (right to left) after disaster,
showing the effect of massive hydrogen gas explosions in #3 and #4,
and a severe, but lesser explosion in #1

Power was restored to the Control Rooms for Units #3 and #4, but not the instrumentation.  Engineers were attempting to reactivate the monitoring systems, including those for measuring temperature of the fuel rods, radiation levels, water level within reactor and spent fuel pools, and valve open/closed condition!  So how did the control room workers monitor the plant, if most of their instrumentation was dead?  [3-22]
Not surprisingly, plutonium Pu-238, 239, 240 was found in soil in five locations at the Daiichi power plant.  All three isotopes have long half-lives, with plutonium-23 taknig 24,000 years to lose half its radioactivity, Pu-238 87 years, and Pu-240 more than 6,500 years. [3-21-22]
Turbine Building
From the incident standpoint, how did the workers jury-rig fire hoses to cool the damaged reactors?  News reports described fire pumps were used to inject sea water into the reactors.  No mention of ordinary fire hoses being used.  The utility never stated whether water poured onto the reactors and spent fuel pools were allowed to drain as contaminated, radioactive water directly into the Pacific Ocean, or to flood the sub-floors of the reactor buildings.  Somehow, workers were able to force sea water into the piping system.
Radiation levels at greater distances from the plant are being reported.  On March 24, the Japan government detected 1,400 microsieverts at a distance of 30 km (18.6 mi) from the plant.
Japanese officials began quietly encouraging people to evacuate a larger swath of territory around the Fukushima Daiichi nuclear plant on Friday, a sign that they hold little hope that the crippled facility will soon be brought under control.  The authorities said they would now assist people who want to leave the area from 12 to 19 miles outside the crippled plant and said they were now encouraging “voluntary evacuation” from the area. Those people had been advised March 15 to remain indoors, while those within a 12-mile radius of the plant had been ordered to evacuate.
The United States has recommended that its citizens stay at least 50 miles away from the plant.

units
              234
Smoke from Unit #3 in middle, Unit #2 (l.), Unit #4 (r.) taken from roof of
Unit #2 turbine-generator building.  Smoke particulates for burning spent fuel
include plutonium-239, strontium-90, cesium-137, yttrium-91, and iodine-137.

Current concerns on March 25.

  • Unit #1:  plant stabilized since building explosion and damage.  pressures and temperatures continue to fluctuate.  Begin fresh water injection into reactor and spent fuel pool.  cooling system inoperable.  building severely damaged by initial explosion.  lighting restored.
  • Unit #2:  reactor vessel likely cracked, venting radioactive gases into the sky; cooling pumps damaged beyond repair, need replacement, could take weeks.  Plan to inject fresh water into reactor and spent fuel pool.  building only slightly damaged.  200-300 millisieverts/hr inside the plant (250 mSv/year allowed for workers).  control room lighting restored, but no power for monitoring instrumentation.
  • Unit #3:  reactor contains plutonium fuel load; reactor temp reached 572 F (300 C), stabilized.  three electrical workers contaminated by radiowater water in basement.   pressure being maintained, less likely to have cracked vessel.   building severely damaged by initial explosions.  fresh water being pumped into reactor.   fresh water pumped in by Sunday March 27 for spent fuel pool.  [video]
  • Unit #4:  spent fuel pool likely dry, fuel overheated and damaged, releasing radioactivity into the sky.  concrete pump truck dumping sea water into spent fuel pool.  reactor water level and pressure ok.  fresh water pumped in by Sunday March 27 for spent fuel pool.
  • Unit #5:  spent fuel pool temperature reduced from 65 C to 37 C, toward normal 25 C.  cooling pumps for reactor and spent fuel pool operable.  three holes punched in exterior building to prevent hydrogen gas explosion.
  • Unit #6:  spent fuel pool temperature reduced from 65 C to 41 C, toward normal 25 C.  cooling pumps for reactor and spent fuel pool operable.  three holes punched in exterior building to prevent hydrogen gas explosion.

Earthquake chartTsunami travel
              times
The seismic chart left shows the huge magnitude and duration
of the earthquake, when compared to the 1995 Hanshin Earthquake.
Chart at right shows tsunami travel times across the Pacific.

After the quake, the reactors had automatically shutdown. Off-site power too had snapped. The generators managed to provide power for about an hour when the 10-meter tsunami reached the plant, breached the seawall, swept away the diesel fuel tanks and drowned the generators. This led to a critical condition called "station blackout".   March 23 reports from the Japan government estimated the tsunami wave as high as 77 feet (not saying where).
fuel tanks

Analysis emerging now shows that there were 13 diesel generators installed in a below-ground bunker near the seawall protecting the nuclear plant from the ocean.  Diesel fuel was reportedly stored in tanks built on the sea front to facilitate easy unloading from ships, and perhaps in storage tanks located near the diesel generator bunkers.  TEPCO indicated the rooms that house those backup generators are fairly watertight.
The before-after photo at the right shows the location for two diesel fuel tanks.  The two tanks are located right at waters edge, protected only by a small rock dike.  There were likely other fuel tanks located adjacent to the underground bunkers where the diesel generators resided.   Much plant equipment appears to be missing after the tsunami.  The reactor building is set back 100 meters from the ocean, behind the turbine-generator buildings.  The plant designers flawed assumption was that the seawall would fully protect the fuel tanks, electrical switching banks, and below ground bunkers in which the diesel generators resided.
Site Seawall
The plant was designed to ride out a tsunami, but the one which struck was beyond that design limit.  Fukushima was designed with a 5.7 meter (18.7 ft).  The seawall appears to be the large breakwater, surrounding the trapezoid shaped lagoon.  The lagoon would absorb the overflow, and prevent flow onto the low lying plant site.   The initial shock wave for a large water surge would hit the seawall at 500 mph, and force the water up and over the breakwater.   An 18 foot tsunami could overflow the 18 foot seawall.   Wave speed was estimated by transit time to California in 10 hours for 5000 miles distance.  If not computers and dynamic analysis in late 1960s, difficult computation for that decade, water tank simulation could have demonstrated the seawall limitations. 
On March 22, TEPCO revised estimated of the tsunami that hit Daiichi to 14 meters, or 46 feet, based on height of water markings on the buildings.  To fully inhibit an initial wave and subsequent tsunami tide might have required a 75 foot seawall, to allow the main lagoon to dissipate the initial surge, and allow an equally tall secondary breakwater to stop the tsunami.   There is an elevated plateau right behind the plant, which would have been a better location for the plant. 
Japan has suffered 195 tsunamis since 400, according to Japan’s Central Research Institute of Electric Power Industry, which produced a report on tsunami threats to nuclear plants on the opposite coast to Dai-Ichi in July 2008. Three in the past three decades had waves of more than 10 meters.  A 7.6-magnitude quake in 1896 off the east coast of Japan created waves as high as 38 meters, while an 8.6- magnitude temblor in 1933 led to a surge as high as 29 meters, according to the U.S. Geological Survey.
There is high residual heat in the cores even after shutdown, sufficient to boil off 300 tonnes of water every day. So water needs to be pumped in continuously to cool the core.  Pumps do this, but they need power. That is why, standby generators are needed.Keeping the generators at low levels has been criticized by experts in nuclear design.  TEPCO managing director Akio Komori admitted that the elevation of the backup generators was a potential issue of inquiry.
Daiichi site
After the generators failed, a third backup of battery power kicked in.  But it had capacity of supplying DC power for just 8 hours to operate the valves in the Reactor Core Isolated Cooling (RCIC) system.  When the batteries ran out, the reactors and storage pools were effectively without cooling water, causing heat build up, potential corrosion of fuel rods, production of hydrogen and its explosions, etc.
Some nuclear plants in the US, have Fukushima type design, but they keep the generators in watertight stalls with 30-centimeter thick concrete walls.  Experts say that the Fukushima reactors are the Mark I type with ‘active’ cooling systems, that is, based on power driven flow of water.  Later, models have ‘passive’ cooling systems that are not dependent on power.
The TVA in Tennessee has equipment similar to that which failed in Japan, but with some differences that are very important.  For example, TVA’s Browns Ferry plant, near Athens, Ala., also has emergency diesel generators, but they are in flood-protected buildings with watertight doors. Each generator has a seven-day fuel supply that is buried underground, as are the wiring and breaker panels for the generators.  To address the potential hydrogen build-up problem, in the mid-19802 the Browns Gerry plants were fitted with a "hardened" vent system that channeled hydrogen outside the containment to be dispersed into the air.  Better to disperse, than blowing up the outer building.
Radiation spewed from the reactor in a meltdown might rise to as high as 500 meters (1,640 feet). The Chernobyl explosion sent radioactive dust 30,000 feet high and continued for months.  Since the outer, Secondary Containment buildings are heavily damaged, the areas above the spent fuel pools are well ventilated.  Hence, should the spent fuel continue to overheat, and zirconium cladding overheat, the hydrogen released from the uranium will should not explode.  Should the catch zirconium fires, smoke can carry particulates of highly radioisotopes into the atmosphere, particularly cesium and plutonium, along with strontium and iodine.
The situation is unstable.  Video describes situation in plain English:  Michio Kaku, quantum physicist, author "Physics of the Future"]  The credibility of TEPCO has melted down, as the utility says the situation is under control, i.e. if one considers hanging on to the abyss by your fingernails.  The pictures do not lie.  The crane used to lift and move fuel rods from the reactor to the spent fuel spool is clearly visible.  You should not be able to see the crane from outside the plant!  [see crane photos before and after]
Situation is grave.  Prime Minister Naoto Kan said the crisis remains "very grave", as forecasts indicated changing winds could start moving radiation closer to Tokyo by the end of the weekend.  3-18-2011
Control
        roomResult after dumping initial water into reactor buildings on March 17. Chopper crews flew missions of about 40 minutes each to limit their radiation exposure, passing over the reactor with loads of about 2,000 gallons (7,500 liters) of water. Another 9,000 gallons (35,000 liters) of water were blasted from military trucks with high-pressure sprayers used to extinguish fires at plane crashes, though the vehicles had to stay safely back from areas deemed to have too much radiation.  Special police units with water cannons were also tried, but they could not reach the targets from safe distances and had to pull back.

Kyodo reported 64 tons of water were dumped on the Units #3 and #4 via helicopter and fire cannons on fire trucks, to cool the spent fuel rods in the spent fuel pool (probably empty of water).  Efforts were halted due to high radiation levels, which instead of decreasing, had increased from 3,700 to 4,000 microsieverts per hour.  Radiation level are likely too high for both fire trucks as well as helicopter pilots.  Smoke was also observed coming from Unit #2, indicating the fuel rods in its spent fuel pool was burning as well.
Considering that 700 tons of water would be needed to barely cover the tops of fuel rods in an empty pool, the initial water dumped into the plants will cool the rods by direct contact on the way to the bottom of the pool.  Its quite possible the water is leaking out as fast as water is being shot in.  But TEPCO has yet to concede the spent fuel pool is cracked and leaking water in Unit #3.  Photos of Unit #3 after the explosion show the horrific damage to the steel frame, not just upper walls blown off, but the upper steel frame mangled and two entire walls from the containment blown away.  The spent fuel pool could not have completely dried up after a couple days, from having simply lost its recirculation pumps.  Unit #3’s pool dried up much faster than the other reactor pools.
water cannon

As of 10 p.m. local time on Thursday in Japan (Wed PT), the JAIFl listed the following status of the six Fukushima reactors:
•    Reactor Buildings #1, #3 and #4: "severely damaged"; #2: "slightly damaged";
•    Cooling was not working for Reactors #1, #2 or #3;
•    Reactor #2 water levels covering >50%; in #1 & #3 water levels covered ~50% of fuel.  
•    Structural integrity of spent fuel pools unknown for Reactors #1 and #2;
•    Reactors #3 & #4:  low water levels;  spent fuel pool in #4 at dangerously high 85 C.
•    Spent fuel pool temperature rising for Reactors #5 and #6 to 65C.
The photo at left shows one fire truck shooting the water cannon to the plant roof, hoping to dump water into the spent fuel pool.  Seven fire trucks were used, one at a time due to access limitations near the reactor.  This was taken on Friday local time.  They hoped to shoot 50 tons into the reactor.  Given the volume and tonnage of water required to fill a mostly empty pool, its difficult to fathom how the pool can be filled with ongoing boil off of water.
On Friday and Saturday, the fire trucks are continuing to dump water into the reactors, using an unmanned fire truck and 2500 ft hose.
On March 19, fire trucks shot over 2000 tons of water into spent fuel #3, in a late night mission that lasted over 13 hours.  [Calculation:  the fire hose is rated at 750 gallons per minute, i.e. 100 ft3/min = 6250 lb/min, or ~3 tons/min.  Hence, 2000 tons would require 667 min = 11 hours with no down time.  This would be enough water to at least cover the fuel, since 1400 tons are required to raised an empty pool to just cover the fuel to depth of 15 feet.]
By March 20, the spent fuel pools in Unit #5 and #6 had been reduced from 65 C to 37 C and 41 C, resp., back toward the desired 25 C temperature.  The pool at Unit #4 continues to run very hot, as there is little or no water, with a potential leak in its pool.
On March 20, the government stated the entire Fukushima Daiichi complex would be scrapped once the emergency is resolved.
The spent fuel pools are of significant concern.  Used fuel rods also contain radioactive isotopes:  plutonium-239, strontium-90, cesium-137, and iodine-131.  These are more dangerous than new fuel rods. 
On March 24, Japan’s government says the detection of radioactive neutron beams 15 times near the plant following the destruction by the tsunami were natural events and there is no evidence any uranium and plutonium leaked from reactors.
What Hilary Thinks.  In a confused statement that confounded nuclear experts, Secretary of State Hillary Rodham Clinton said Friday morning that U.S. Air Force planes in Japan had delivered "coolant" to a nuclear power plant affected by the quake.  Nuclear reactors do not require special coolants, only large amounts of pumped water.  
"They have very high engineering standards, but one of their plants came under a lot of stress with the earthquake and didn’t have enough coolant," she said, "and so Air Force planes were able to deliver that."
US
            Navy barge
Though the boiling water reactor has already been turned off by inserting neutron-absorbing control rods all the way into the core, adding boric acid or, more likely, sodium polyborate would turn the reactor more off than off — which could come in really handy in the event of a subsequent coolant loss, which reportedly has already happened. But that’s a $1 billion kill switch that most experts wouldn’t think to pull.  Its use would indicate the nuclear threat is even worse than presently being portrayed in the news, and lost hope of keeping those cooling pumps on. Eventually they’ll vent the now boron-laced coolant to the atmosphere to keep containment pressures under control.  Sodium polyborate, by the way, is something you might use around the house, since it is the active ingredient in most flea and tick treatments.

The US Navy two weeks later delivered a 500,000 gallons of fresh water via barges from US naval base at Yokosuka.  The fresh water will dissolve and wash the salt buildup from the reactor cores, since salt crystals on the fuel rods would inhibit cooling.
Status of the six nuclear reactors on Wed March 17 US.  San Jose Mercury News, March 16, 2011.

Daiichi
              status

Immediate Risk to North America Currently Low.  Radioactive particles from the earlier explosions pose low risk to North America, and should fall into the Pacific before reaching the West Coast.  “Such a long time spent over water will mean that the vast majority of the radioactive particles will settle out of the atmosphere or get caught up in precipitation and rained out.  It is highly unlikely that any radiation capable of causing harm to people will be left in the atmosphere after seven days and 2000-plus miles of travel distance.”
Tsunami Wave.  Although the 10 meter height of the tsunami wave seems imaginable, in 1896 the Sanriku tsunami towered to 15 meters, nearly 50 feet and killing 27,000 people.  In one village, the tsunami wave was estimated at 20 meters.

Daiichi Layout

Fukushima Daiichi Nuclear Power Station Layout

Fuku
            Plants status

Power
              Stations

Unit3 Dispersion

Fukushima Hawaii Girls

Fukushima’s Hawaii girls go on tour in Japan to promote the safety of
their Spa Resort Hawaiians, just 28 miles from the Daiichi power station

 

Good References:
All Things Nuclear
Brad’s Blog
8390  Japan nuclear plant emergencies, March 11
8391  Explosion rocks Fukushima 1, March 12
8392  View from within the Tsunami, March 13
8393  New explosion at Unit #2, March 14
8394  PM addresses the nation, fire at unit #4, blast at unit #2, March 14
8395  Green News report, March 15
8396  Smoke billows from unit #3, workers evacuated, March 15
8397  UK and France warn citizens to get out of Tokyo, March 16
8398  Could not delay, helicopter drop water onto reactors, March 16
8401  TEPCO release footage of reactor; helicopter water drops, water cannon fails, March 17
8403 Renewed Worries for Nuclear Chain Reaction, March 18
MSNBC.com
42161238  Few options for dealing with nuke emergency 
42120956  Rachel Maddow offers a coherent understanding of concern for spent fuel pools
   How much radioactive material is at the Fukushima plant.
Fukushima Daiichi and Daini Plant Status, 13:00 15 Mar 2011
Layman’s Introduction to Radiation Doses Radiation Dose Chart
Tsunami Destruction of Tarou   protected by 10 m Seawall requiring 30 years to construct.

Technical Discussion of the Japanese Nuclear Emergency

All Things Nuclear RSS
Possible cause for hydrogen leaking into containment
Possible cause for reactor building explosions
Where did water in spent fuel pools go?

Special Considerations for BWR/PWR Facilities  Reactor Safety Course R-800

Chronological fact sheet on  2011 Crisis at Fukushima Nuclear Power Plant  (pdf)
Marks to Market:  America’s Nuclear Time Bombs  2-28-2012 
BBC Documentary

Inside the Meltdown  Feb 2012
Japan’s Children of the Tsunami  March 2012

Arnie Gundersen videos & transcripts releases

New Containment Flaw Identified in the BWR Mark 1 2-9-2012 At Unit #1, the containment pressure rose to 125 lb/in2, and then subsided back to around 100 lb/in2.  This indicates the containment head had lifted off by stretching of the 180 containment head bolts, allowing hydrogen gas to leak directly into the building.  Just before the explosion, steam was being vented from the stack, showing the vent was open.  Yet the explosion still occurred.  Why?  Hydrogen gas was leaked directly into the building, and the vent was of no consequence.
TEPCO Believes Mission Accomplished & Regulators Allow Radioactive Dumping in Tokyo Bay 12-29-2011  Plans are to dilute radioactive debris from the site to reduce to accepted levels, then burn.  This will simply re-release a large amount of radioactive particles back into the atmosphere, while the radioactive ash is dumped into the bay.  The environment will continue to be polluted, and spread across the country into the ocean.
Hydrogen buildup at Fukushima? What does it mean & why does it happen? 11-16-2011  Simple experiment to illustrate hydrogen deflagration.
New TEPCO Photographs Substantiate Significant Damage to Fukushima Unit 3 10-19-2012  Unit #3 explosion started in the spent fuel pool, evidenced by roof being blown away over the pool.  Steam plumes from the center of the building points to the containment being damaged.  The thick concrete floor and walls of the spent fuel focused the explosion upwards, spewing its nuclear fuel up to 2 miles from the plant.  The explosion at Unit #3 was a denotation, not a deflagration, as evidenced by the shock wave moving at ~1000 mph, i.e. supersonic.  This speed is required to toss such fuel pellets up to 2 miles distance.  This shock wave damaged the adjacent Unit #4 building structure, which is not designed to handle shock waves.
Identifies Safety Problems in all Reactors Designed Like Fukushima 9-19-2012  The nuclear industry are using a flawed cost benefit computer code that underestimates the value of human life and minimize property damages after an accident, which has the effect of justifying continued operation of reactors without safety modifications.  To open the vent manually (since electricity had failed) required a human to go into the radioactive containment, and turn a massive valve handle 200 turns!  A series of teams are required to manually open a single valve.  The 60+ holes in all BWR reactor vessel bottom for control rods creates an easy path for melted fuel to penetrate the vessel, unlike a pressurized water reactor.

TEPCO Data Proves Fairewinds Assertions of Significant Fuel Pool Failures at Fukushima Daiichi  8-26-2012

Why Fukushima Can Happen Here: What the NRC and Nuclear Industry Dont Want You to Know 7-10-2012   Good engineering description of how the major safety systems were supposed to work.  Unit #1 had an isolation condenser to absorb excess pressure from the reactor.  With power out, a large valve to the condenser was opened to relieve pressure, but as pressure and temperature were dropping too fast to control cooling rates to accepted levels, the valve was closed again.  Reactor vessel pressure rose again, opening safety valves when dump steam at preset pressures to the torus-shaped suppression pool below the reactor.  This is a one-way path, steam is cooled by water in the suppression chamber, but make-up water is not resent to the reactor.  Water level within the reactor drops, exposing the nuclear fuel barring any other source of makeup water.  Eventually, fire hoses were connected to dump sea water into the reactor vessel to cool the fuel.  Sea water has a problem being high corrosive, and salt buildup will prevent cooling water from cooling the fuel rods.

The Implications of the Fukushima Accident on the World’s Operating Reactors  5-11-2011 Seismic design codes did not predict containment or spent fuel pool cracking, hence the engineering designs for nuclear plants are flawed.

Current Condition of Reactors, TEPCO Claim of "No Fission" in Fuel Pool, and Lack of Radiation Monitoring in Fish  4-18-2011  Early pressure data showed unusually high internal pressure within Unit #1 containment.  Recall the Mark I containment head will lift at 100 psi internal pressure, leaking hydrogen gas into the main building.  TEPCO suggests radioactive iodine found in Unit #4 pool came from the sky, i.e. explosion at Units #1, #3, and then #2.  But Unit #4 roof is still intact, so is not plausible.  Perhaps, there was nuclear fission with Unit #4 spent fuel pool to cause the radioactive iodine.

Science Experiment:  How Fukushima’s Fuel Rods Melted and Shattered  4-10-2011  Demonstration heating an actual zircalloy fuel tube.
Fukushima:  The Crisis Is Not Over  6-11-2011   Arnie projects major problems in the disaster, months before most others have begun to learn of the impending disaster with Unit #4 spent fuel pool.