An excellent account of the Fukushima Daiichi accident
One of the best accounts of what actually happened.
From
Charlie Martin at Pajamas Media:
Fear the Media Meltdown, Not the Nuclear One (UPDATED)
The March 11 earthquake off the coast of Japan has been an unprecedented disaster. Now estimated to have been a magnitude 9 earthquake � one of the top five earthquakes measured since reporting started in 1900 � it was the result of a �megathrust� in which an area of sea floor bigger than the state of Connecticut broke free and moved under the force of colliding tectonic plates. It was so strong that it literally moved the entire island of Honshu eight feet to the east. The earthquake was then followed by a tsunami comparable to the Boxing Day tsunami of 2004 � but since the epicenter of the quake was only a few miles off the coast of Japan, the tsunami struck the heavily populated coast of Honshu with almost no warning, basically washing many coastal villages off the face of the earth.
The earthquake and tsunami seriously damaged reactors at the Fukushima Daiichi (�number one�) and Daini (�number two�) in Okuma, in Fukushima Prefecture, and also damaged the Onagawa plant in Miyagi Prefecture. In total, of the 55 nuclear power generation plants in Japan, 11 have been forced to shut down, cutting power generation capacity in Japan dramatically and forcing the country to adopt a series of rolling blackouts. It would seem impossible to overstate the severity of the crisis.
The media, however, has risen to the challenge, with a combination of poor information, ignorance, and alarmism, along with antinuclear activists passing themselves off as unbiased experts.
Let�s try to make some sense of it all.
He starts with an introduction to the basic design and operation and then tells what happened:
What happened at Fukushima Daiichi
The original earthquake hit. Three of the six reactors were in operation, the other three were shut down for scheduled maintenance. The reactors were designed to sustain an earthquake of magnitude 8.2; at magnitude 9, the Honshu quake was 16 times more powerful. This caused the plant to automatically shut down; this was apparently successful, but �
About an hour later, the tsunami hit. The tsunami did two significant things: it destroyed the backup generators that kept the pumps running, and it apparently so contaminated the reserve coolant that it was not only no longer pure, but was so mucked up with the scourings of the tsunami that it couldn�t be safely pumped. At this point, the reactor was in some trouble.
As the reactor heated up, water began to react with the zirconium fuel-rod containers, liberating hydrogen, which started to build up in the boiler. The operators began to vent gases from the reactor to reduce the pressure, liberating the hydrogen into the outer fa�ade building. These gases are mildly radioactive, mainly with nitrogen-16 and several isotopes of xenon, all products of the fission reaction that powers the reactor; apparently they were vented into the outer building in order to slow their dispersion and give them a chance to lose radioactivity.
Hydrogen in combination with the oxygen in the air can be explosive, and at some time after the venting started in reactor 3, the hydrogen in the outer fa�ade exploded, blowing off the walls of upper half of the building and leaving the steel structure exposed. This explosion put six workers in hospital, with various injuries and one apparent heart attack. This was the first spectacular explosion that raised great clouds of white smoke.
This was reported in the New York Times as �radiation poisoning.� No other source has reported this, including the IAEA. Apparently, according to the Times, radiation poisoning breaks arms.
The second explosion was another hydrogen explosion; as before, apparently what was destroyed was the outer building that surrounds the containment, not the containment itself.
Charlie then talks about the basics of radioactivity, the units of measurement and what was actually released at the plant and he compares this to other exposures. The worst exposure recorded was the equivalent of 20 CT Scans, well below the danger level. The fact that we are measuring elevated levels of radiation does not mean that we are measuring dangerous levels of radiation.
It is a long article but well written and worth reading for a clear view of what is happening. There is an brief update this morning (15th) about the
fuel-rod fire:
Fuel rod fire?
While I was asleep, there was a new and unhappy event at Fukushima Daiichi: stored spent fuel rods apparently caught fire. At least right now, this is considerably more exciting than the actual reactor problems. Here�s what the IAEA says:As reported earlier, a 400 millisieverts (mSv) per hour radiation dose observed at Fukushima Daiichi occurred between units 3 and 4. This is a high dose-level value, but it is a local value at a single location and at a certain point in time. The IAEA continues to confirm the evolution and value of this dose rate. It should be noted that because of this detected value, non-indispensible staff was evacuated from the plant, in line with the Emergency Response Plan, and that the population around the plant is already evacuated.
As they say, that�s in one nasty spot in the plant, and unlike most of the radiation panic, this really is a kind of nasty dose. In the US, we more commonly do dose rates in �rem� � Roentgen Equivalent Man � and one rem is roughly 1/100 Sievert. So this is 40 rem/hr, and that�s not a neighborhood you want to be in a long time. 50 rem is about where you start seeing observable radiation changes, 100 rem in a short time will actually make you sick.
That being said, the dose rate at the gate they report is this:At 00:00 UTC on 15 March a dose rate of 11.9 millisieverts (mSv) per hour was observed. Six hours later, at 06:00 UTC on 15 March a dose rate of 0.6 millisieverts (mSv) per hour was observed.
That�s 1.2 rem/hr, going down to 0.06 rem/hr.
The frustrating part about writing on this stuff is that people don�t seem to have any middle setting between �everything is fine� and �run in circles scream and shout�. So saying �no, it�s not Chernobyl� is interpreted as �it�s nothing.�
So let�s go ahead and make this clear: no, it�s still not Chernobyl. But no, it�s not nothing.
Well written and lots of links to original data. A nice anodyne to the fear-mongering from the 'activists'...
Posted by DaveH at March 15, 2011 7:06 PM