For decades we have been told that with the lessons learned from the 1986 Chernobyl disaster, nuclear energy is safe. As the still unfolding mayhem at the Dai-Ichi plant in Fukushima, Japan, proves, nothing could be further from the truth.
The fuel rods in at least three reactors are partly molten. All six reactors are in trouble, although most were not on-line during the earthquake! In spite of all downplaying by officials, the nuclear industry, and science apologists, a complete meltdown of some reactors and a nuclear chain reaction of molten fuel are still possible. A few science bloggers keep up honest reporting about the current state. I will here provide a deeper overview and in a second part tomorrow additionally try to give a rational long term outlook.
Before the Present Fukushima Disaster
2007, after an earthquake at another plant belonging to the same TEPCO power company, radioactivity was leaked. The leak was kept secret, the public only informed days after, too late for any simple precautions like staying indoors.
The Fukushima plant is 40 years old and was supposed to be dismantled, but is kept alive just like many frail reactors all over the world. Already during an earthquake in 2008 did water leak out of a fuel rod storage facility at the Fukushima plant.
Reactor schematics of the boiling water reactors in Fukushima
This history is important, because it clearly shows that the nuclear science is not the problem. One cannot honestly discuss the so called “irrational panic” of the public without discussing the fact that safety records have been falsified and problems downplayed routinely. The public’s distrust and fears are mostly rational and justified.
Friday, March 11, 2011
An earthquake with a subsequently to be expected tsunami wave triggered the far reaching problems in the Fukushima Dai-Ichi nuclear plant. It needs to be stressed: This was the trigger, not the reason for why the mostly off-line reactors are in trouble. As we will discuss, the reason is the same as it was in Chernobyl in 1986, the same as for the 1979 Three Mile Island incident before that: nuclear power is inherently unsafe and too complicated to be safely handled by humans under the pressures of human society, which includes economical and political pressures.
Carter Leaving Three Miles Island
Merely three of the reactors in Fukushima were running at the time. The widely praised automatic emergency shut-off did therefore little to prevent the catastrophe. A boiling water reactor needs active cooling even when “switched off” – that means, you cannot actually switch it off! It keeps going at a steady rate of at least 3% normal for over 30 years. Remember, we are talking 3% of the power output of a nuclear reactor, which is huge and the reason for why such reactors have been build in the first place.
After the diesel generators failed to keep the cooling water pumps running, batteries only lasted one hour. The water necessary to cool the fuel rods started to boil away. External diesel generators were brought to the plant, but could not be connected because the batteries’ sockets were under the waterline that one would expect in the basement suffering flooding. None of this involves nuclear physics. These are failures that humans always encounter with long and well known technologies. No future advance in nuclear technology is expected to improve the usual error rate when humans meet conventional technology.
Chernobyl is often conveniently blamed on “the stupid Ukrainians messing up”. Keep in mind: The present failures occurred in the technologically most advanced human society, which arguably is Japan!
Saturday, March 12, 2011
The tips of the fuel rods in block 1 and 3 are not surrounded by cooling water anymore. How far is not known because the water level sensors fail.
At half past three in the afternoon, the pressure inside the reactor core of block 1 rises to 8 mega Pascal, double the normal operating pressure (remember – it is supposedly “switched off”!). There is no other choice: radioactive steam has to be vented into the environment.
The vented gas contains hydrogen, which ignites and blasts the roof and the top walls off of block 1. Radioactive Iodine and Cesium are released. All three, hydrogen, iodine and cesium, prove that the core partially melted! Hydrogen results if the zirconium in the fuel rod shells melts and reacts with the water steam at around 2500 degrees Celsius.
Melting reactor core
This means that against all downplaying by the media, already on day two it was clear that the fuel rods partially disintegrated and uranium pellets were likely falling to the floor of the reactor core. In case water totally evaporates, the pellets can melt together and go critical, leading to a nuclear chain reaction. There are no so called “diluting core catchers” at usual, non research nuclear plants.
Nevertheless, only a 20 kilometer radius zone around the plant is evacuated. This is very similar to the 1979 Three Mile Island incidence near Harrisburg. Human failure lead to 50% melting of the 36 thousand fuel rods, which in turn lead to a uranium “swamp” that scientists are still not sure about why it did not go critical. Do not feel reassured – it was a different reactor design from Fukushima. As always, the power company denied any danger and tried to silence the news about the released radioactive steam. Only two days later, a 12 kilometer radius was evacuated. Just like today, those that fled further away were called panicky irrationals. In fact, we now know that they were doing the right thing and that those that stayed behind were lucky. It is still not known why Three Mile Island did not blowup or how much radiation was really released (see link above).
In the evening, the engineers at the plant know it all too well: Block 1 could go critical. In a desperate measure, they pump seawater into the reactor. Not only does this increase the pressure yet further, but it destroys the reactor. A reactor is supposed to be cooled with distilled water, not with dirty, at high temperatures corrosive salt water. The reactor in block 1 is thus condemned to become a radioactive monument like Chernobyl, still for our grand children and their grand children to be concerned about.
To help you grasp the desperation of this act: The engineers were well aware of that the water level monitors did not work and that there was no way to tell whether the sea water even reaches inside the core. Yet they pumped, because it was the very last option.
At around ten at night, the fuel rods in block three start melting. These are no ordinary rods. They contain MOX fuel, a mixture of Uranium and highly poisonous Plutonium, dangerous not only as a nuclear fuel that easily goes critical, but also highly chemically poisonous in minute quantities. If this stuff collects on the reactor floor, pray that the steel below melts soon enough to let it fall right through before going ballistic.
If it falls through and encounters the water in the outer reactor building, it may however still explode badly enough to lead to a Chernobyl like incident also globally. Luckily, as of now, it has overtaken Three Mile Island in terms of severity, but resembles Chernobyl only quite locally. Released Plutonium would make northern Japan a wasteland for generations to come.
Reactor block 3 was vented during the night, releasing radioactive steam. TEPCO admits for the first time that fuel rods in block 3 were partially sticking up to three meters out of the cooling water. While some officials are still trying to argue that no melting in block 3 is possible, experts now know that the rods are partially molten also in this reactor.
And indeed: Hydrogen has collected under the roof of block 3. At 11 in the morning, the second explosion propels the roof from block 3. Although it is likely that the containment vessel with the Plutonium has cracks, the public hears nothing but downplaying of the danger. Internationally, popular science websites link to and translate an article titled “Why I am not worried about Japan's Nuclear Reactors”. It is written by a cooperation risk management researcher with cozy industry ties, but referred to as an MIT expert, as if to say nuclear scientist. While the internet is widely hailed as somehow allowing new oversight over the corporate media, a dark chapter in science on the internet unfolds, still not admitted to be another tragedy all by itself by science bloggers. Only few counter pieces like “Why You Should Be Worried About Japan's Nuclear Reactors”, have appeared.
Around noon, reactor 2 heats up to result in a pressure that calls again for the desperate flooding with seawater. Another reactor turns into a pile of radioactive trash for generations to deal with. It is announced that all is successful. Shortly afterward the opposite is announced: The fuel rods are completely dry and melting. Radioactivity in the surrounding area goes up. The international atomic energy agency IAEA is still telling people that no melting has occurred in any of the three by now actually partially molten reactors.
Block2 experiences an explosion, the pressure container is breached. In the immediate surrounding of the plant, radiation rises to eight milliSievers per hour (8mSv/h), forty thousand times the natural background radioactivity.
Shortly after: Bang number 4. Block 4 explodes. This reactor was not in use during the earthquake! This time it is not even the reactor, but the so called “spent” fuel rods in the close by storage pool are to be blamed. Please read this again and remember, taking reactors automatically off-line in case of an earthquake does not ensure safety. This is basic physics: You cannot switch of radioactive decay!
The explosion rips two 8 meter large holes into the building. The fuel rod storage is exposed to the environment, the water evaporates. Fire breaks out, the smoke carries radioactive Iodine and Cesium outside. Outside block 4, a radiation level of 400 mSv/h is reached, millions the natural background. Three hours here and you will likely die soon after.
At these levels, also the control room of block 4 is being abandoned, and 750 workers are immediately evacuated. 50 stay “voluntarily”, to be understood in the context of Japanese culture, where the individual exists for society rather than the other way around. These are the walking dead.
In block 4, fire breaks out repeatedly. Smoke carries radioactive Iodine and Cesium particles as far as Tokyo. While NHK television shows the burning storage facility, Reuters goes along with the Ministry of Economy in Japan, telling us that nothing burns.
Temperatures rise now also in the already before the quake “switched off” blocks 5 and 6.
Reactor 3 burns, radioactivity rises to 1000 mSv/h. Control room 3 is abandoned. The Japanese government decides to increase the legal limit of radiation exposure to five times the US limit in order to not be liable for the workers being exposed. 250 mSv/year is the new maximum. The workers however are long past that limit. Close to the reactors, 600 mSv/h and above are now the norm.
Helicopters drop sea water into reactor 3. This is the fourth reactor that now turns into a Chernobyl like monument for sure. Some Helicopters cannot reach the reactor as the radiation is just too strong.
The fuel rods in the rod storage in block 3and 4 are dry and their temperature rises. They are completely open to the environment now, with block 3 having plutonium in the rods. With lead plates somewhat protected helicopters dump water on the buildings. The crew can fly maximally four times before the radiation limit is reached. Most of the water does not reach the intended aim, radioactivity keeps rising.
At around eight o’clock they try to employ water cannons that the police purchased to disperse anti nuclear protesters. It fails due to high radiation levels. The Japanese Military has more powerful cannons and douses the block 3 and 4 with some water.
Finally, electricity cables reach the plant. However, they cannot be connected to the pumps, as the electrical structure in the plant is damaged. More than a hundred fire fighters and military keep pumping water into the general direction of the reactors. It is unclear how much hits the intended target.
Block 2 starts to smoke. It cannot be doused in water, because the roof is still intact. Japanese officials for the first time admit that even if all goes well now, the reactors will have to be treated just like the ones in Chernobyl.
Governments and scientists still play down the risks, however, they also tell their own people to evacuate as far away as Tokyo at the same time (!), for example France and the journal Nature.
Only two blocks have been connected to electricity. Venting of radioactive gas is going on.
The crisis is far from over. Pressures in the plutonium carrying reactor rose again. Venting a cloud dense with radioactive Iodine, Krypton and Xenon may be necessary. Moreover: The wider consequences start to become apparent:
Radioactivity in spinach and milk from areas as far as 75 miles away exceed safety limits. Tap water turned up radioactive iodine in Tokyo and other areas. Safety officials finally admit that protective iodine pills should have been distributed near the plant days earlier:
A “nuclear safety official said the government was caught off-guard by the accident's severity and only belatedly realized the need to give potassium iodide to those living within 12 miles (20 kilometers) of the Fukushima Dai-ichi nuclear complex. […] The official, Kazuma Yokota, said an explosion at the plant's Unit 3 reactor last Sunday should have triggered the distribution.”
There have been sadly few scientists/ science bloggers who took the lessons from the surprisingly large number of earthquake and tsunami survivors seriously: Preparedness is the most important fact in any disaster. Very few told you since day one: Potassium iodide belongs into your disaster preparedness kit! Do not hope that in the heat of a large disaster, your government will be able or even willing to get them to you! Their main concern is avoiding panic and the appearance of not being in control, not the health of your family. If you are anywhere near nuclear facilities, which you are in any industrialized country, you should have potassium iodide in your first aid kit at home! You do not? Get it now!