While it is premature to draw conclusions from the tragedy in Japan, we can certainly consider what is taking place a "worst case" disaster, and thus far, even the most seriously damaged of its 54 reactors has not released radiation at levels that would harm the public. That is a testament to their design and construction, and the effectiveness of their employees and their emergency preparedness planning.
Following Friday's devastating earthquake, uranium fuel rods were exposed for at least two and a half hours. There was some burning of nuclear fuel, as evidenced by the presence of radioactive hydrogen and cesium, and partial meltdowns did occur.
However, as I pointed out yesterday, the explosions witnessed were not the reactors themselves blowing up, nor were they the primary containment. The primary containment that houses and protects the reactor vessel and fuel remains intact and is safe. This structure is made of steel and steel-reinforced concrete and is extremely robust.
The primary and secondary containment are designed to prevent radiation from being released into the environment in the case of an accident. However, TEPCO (Tokyo Electric Power Company) intentionally vented steam from the secondary containment building in an effort to reduce pressure in that building. What we saw blow up was the secondary containment, the sheet metal building that sits on top of the cement containment. The reactor's containment performed according to design.
It appears that as the level of coolant in the reactor vessel lowered, a portion of the top of the uranium fuel rods was exposed. This may have caused zirconium cladding of the fuel rods to react with water to create hydrogen. This hydrogen was vented, then somehow ignited, causing the explosion.
As the explosion did not occur inside the reactor core, and the primary containment was not breached, there has not been a significant public health impact from the release of radiation from the containment structure.
Reactors 2 and 3 at Fukushima Daiichi were shut down in response to the earthquake. Units 4, 5 and 6 had been shut down prior to the earthquake for inspections and scheduled outages.
In response to the emergency conditions, TEPCO has been pumping seawater, laced with boron, into the reactor.
Fukushima Daiichi Unit 1 was shut down at 2:48pm on March 11th. The reactor was shut down, reactor water level was stable, and offsite power was available.
At 8:19am, March 12th, there was an alarm indicating that one of the control rods was not properly inserted. However at 10:43am the alarm was spontaneously called off. Other control rods were confirmed fully inserted and the reactor was in a subcritical status.
o Status of main steam isolation valve: closed.
o Injection of water into the reactor by the Make-up Water Condensate System.
o There was not believed to be any leakage of reactor coolant in the containment vessel at this time.
o At 5:22am March 12th, the temperature of the suppression chamber exceeded 100 degrees. As the reactor pressure suppression function was lost, at this time it was determined that a "significant nuclear incident" had occurred.
o The Utility decided to prepare implementing measures to reduce the pressure of the reactor containment vessel (partial discharge of air containing radioactive materials) in order to fully secure safety. This preparation work started at around 9:43am March 12th and finished at 6:30pm the same day.
o Restoration work in reactor cooling function that was conducted to achieve reactor cold shutdown was completed and cooling of the reactor commenced at 1:24 am, March 14th.
o It was confirmed afterwards that the average water temperature of suppression chamber was constantly below 100 degrees.
Fukushima Daiichi Unit 2 was shut down at 2:48pm on March 11th. The reactor was shut down and reactor water level was stable, offsite power was available, and control rods were fully inserted, rendering the reactor in a subcritical status.
o Status of the main steam isolation valve: closed.
o Water was injected into the reactor by the Make-up Water Condensate System.
o It is not believed that there was leakage of reactor coolant in the containment vessel.
o At 5:32am March 12th, the temperature of the suppression chamber exceeded 100 degrees. As the reactor pressure suppression function was lost, at 5:32am March 12th it was determined that a "significant nuclear incident" had occurred.
o The Utility decided to prepare implementing measures to reduce the pressure of the reactor containment vessel - a partial discharge of air containing radioactive materials - in order to fully secure safety. This preparation work started at around 10:33am March 12th and was completed by 10:58pm March 12th.
o Restoration work in the reactor cooling function was in progress to achieve reactor cold shutdown.
o Restoration work in reactor cooling function conducted to achieve reactor cold shutdown was completed and cooling of the reactor commenced at 7:13 am, March 14th.
o It was confirmed afterwards that the average water temperature in the suppression chamber was constantly below 100 degrees.
Fukushima Daiichi Unit 3 was shut down at 2:48pm on March 11th.
o The reactor was shut down, reactor water level was stable, offsite power was available, control rods were fully inserted, and the reactor was in a subcritical status.
o Status of the main steam isolation valve: closed
o There was not believed to have been leakage of reactor coolant in the containment vessel, but measures to reduce the pressure of the reactor containment vessel via partial discharge of air containing radioactive materials were implemented in order to fully secure safety. The preparation work started at around 12:00pm March 12th and finished at 12:13pm March 12th.
o Reactor cold shutdown occurred at 12:15pm March 12th
Fukushima Daiichi Unit 4 shut down at 2:48pm on March 11th. The Reactor was shut down, reactor water level was stable and offsite power was available. At 0:43PM, there was a signal indicating that one of the control rods may have not properly inserted. However, another signal confirmed it completely inserted. The reason for this in under inspection.
o Status of main steam isolation valve: closed
o Injection of water into the reactor is done by Make-up Water Condensate System.
o There is not believed to be a leakage of reactor coolant in the containment vessel.
o In order to cool down the reactor, water was injected into the reactor by the Reactor Core Isolation Cooling System. However, at 6:07am March 12th, the temperature of the suppression chamber exceeded 100 degrees. As the reactor pressure suppression function was lost, at 6:07am March 12th it was determined that a "significant nuclear incident" had occurred.
o It was decided to prepare implementing measures to reduce the pressure of the reactor containment vessel - partial discharge of air containing radioactive materials - in order to fully secure safety. This work started at around 11:44am March 12th and finished at around 11:52am March 12th.
o Restoration work that was conducted to achieve reactor cold shutdown was completed and cooling of the reactor commenced at 3:42pm March 14th.
At approximately 11:01am, an explosive sound followed by white smoke occurred at the reactor building of the Fukushima Daiichi Unit 3. It was believed to be a hydrogen explosion.
As of 4:00 pm, the measured value of radiation dose at the monitoring post in Fukushima Daiichi Power Station remained at ordinary levels. No radiation impact to the external environment has been confirmed.
The possibility of radioactive material being discharged from exhaust stack or discharge canal is continuing to be monitored in detail. As of 4:00 pm, the measured value of radiation dose at the monitoring post in Fukushima Daiichi Power Station remains at the ordinary level. No radiation impact to the external environment has been confirmed.
Timelines info source: TEPCO
There is one thing of which we can be certain: A) Given the basic design features of the Fukushima Daiichi plant, a Chernobyl-type disaster was never a possibility.
The fact of the matter is that our modern society needs electrical power, and to get that electrical power, current must be generated by turbine generators. It takes energy to turn those turbines, in the form of steam (or in the case of hydro-electric dams, water driven by gravity). To boil the water to make the steam takes a source; heat, from either nuclear fission, or coal, oil or natural gas. Wind and sunshine simply cannot generate the current, and we cannot depend upon them for energy without accepting some serious cutbacks in our lifestyle; like, say, doing without air conditioning, television, X-ray machines, and modern manufacturing processes.
Incidents like what took place over the weekend are the risks we accept, to maintain our modern quality of life. It was bad, and our hearts go out to those injured in the events at the Fukushima Daiichi plant, to the hundreds of thousands displaced by Friday's terrible events, and to the tens of thousands dead, injured and missing.
- SEAN LINNANE SENDS
If
If you can keep your head when all about you
Are losing theirs and blaming it on you;
If you can trust yourself when all men doubt you,
But make allowance for their doubting too:
If you can wait and not be tired by waiting,
Or, being lied about, don't deal in lies,
Or being hated don't give way to hating,
And yet don't look too good, nor talk too wise;
If you can dream - and not make dreams your master;
If you can think - and not make thoughts your aim,
If you can meet with Triumph and Disaster
And treat those two impostors just the same:.
If you can bear to hear the truth you've spoken
Twisted by knaves to make a trap for fools,
Or watch the things you gave your life to, broken,
And stoop and build'em up with worn-out tools;
If you can make one heap of all your winnings
And risk it on one turn of pitch-and-toss,
And lose, and start again at your beginnings,
And never breathe a word about your loss:
If you can force your heart and nerve and sinew
To serve your turn long after they are gone,
And so hold on when there is nothing in you
Except the Will which says to them: "Hold on!"
If you can talk with crowds and keep your virtue,
Or walk with Kings - nor lose the common touch,
If neither foes nor loving friends can hurt you,
If all men count with you, but none too much:
If you can fill the unforgiving minute
With sixty seconds' worth of distance run,
Yours is the Earth and everything that's in it,
And - which is more - you'll be a Man, my son!
- Rudyard Kipling
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