From a couple of days, people all over the world discover, stunned, the scale of the damage due to the earthquake and, most of all, the tsunami which was being created in the mid-Pacific ocean, 140 kilometers from the North-East coast of Japan.
If you want an overview of this damage, go and see this Chinese video.
These pictures are extremly impressive. Here are some samples:
One says "governing, it's predicting". In this case, it's predicting the consequences, that we could call "secondary" or "colateral", of such a natural disaster. Japan, overpopulated, owns 58 nuclear reactors to meet it's electricity requirements. A nuclear reactor, it's a tank made of steel, very resistant, in which are put bars made of a fissile material. Technically, it's these tubes that we call "fuel rods" and in which are stacked fissile elements, being an oxide blend, and having the aspect of aspirin pills.
Compared to an atomic bomb, which behaves as an explosive, a reactor looks like an ember pile. In these rods, the uranium 235 decomposition, or even the one of a certain pourcentage of plutonium 239, frees heat and provodes the emission of neutrons which, hitting other uranium 238 atoms, provode secondary reactions.
To well understand the functioning of a reactor, download my comic book "Yours, energetically" on the website of Knowledge Without Borders http://www.savoir-sans-frontieres.com (almost 400 books from the Anselme Lanturlu Adventure series, totally free, in 36 languages, without any media coverage, whatever the press).
A coolant is necessary, which permanently circulates in this tank, this core of the reactor, to evacuate calories, the heat given off by fission reactions, otherwise the worst can occur.
Considering it's my duty to try to shed light on some information, I do my best to broadcast it. I get knowledge, oftenly on short deadlines, when it's not in a rush situation, about current affairs. I do it besides many activities that I have to carry on in the same time (I have to write two new books, to lead researches about MHD, to do complex calculations...).
I take advantage of this remark to ask tens of readers who, daily, beg me to accept to be added on their "chat list" to refrain from doing this. I don't have the time to hold forth as on a highschooler blog. Highschoolers solicit me for their supervised personnal project TPE (same thing : I absolutely don't have any time to look after them). Other people expect that I will answer questions like "could you explain me in simple terms the relativity ?" or even "what do you think about the theory of the hollow Earth ?" ; unless they just say me "I am personnaly very sceptical about... could you give me arguments able to convince someone as sceptical as me ?". Someones, who came across websites or videos which they considered interesting, settle for forwarding me the web addresses without any explanation. If these web addresses are not added with some lines of explanation, I don't have physically the time to go and explore each of these contents.
Sometimes, readers ask me a question to which I answer laconically, may the response be simply "I don't know". Sometimes the interlocutor insist, don't understanding why "a scientist such as me doesn't take time to answer in a suitable and argued way". Sometimes, the exchange ends with a mail coupled with violent insults.
Despite this, what I receive continuously, every day, constitutes an irreplaceable material, and it is thanks to all these contributions and explanations from specialists that I can be better equipped to try to inform you. Someones, which follow me from a while, know how to provide me this information, with some presentation lines, or even a picture, saying me "it seems to me that this is important", and I am grateful to them. Other people know how to cut out a video to extract key elements.
When I build a new web page, you can notice that I don't settle for indiquate an URL address of an article or a video. I do many screenshots, I make up my own text and the set-up of a simple page, where elementary tasks are accumulated, represents frequently from 6 to 12 hours of work.
In the following part, I will correct what I published on the web yesterday, quickly, about the Japanese reactor, and which readers immediatly corrected. No, it's not pressurized water reactors, but boiling water reactors.
Let's tackle the diagram of pressurized water reactors, solution of American origin, mainly used in France.
Into atmospheric pressure, water boils at 100°C ; at lower temperature, 85°C, at the top of the Mont Blanc ; and inversely at a higher temperature than one hundred degrees Celsius if this water is into a higher pressure than one bar.
If the heat is not evacuated continuously, these bars, in metal, can melt down (it's the "nuclear meltdown") and the result of this meltdown can get together into the bottom of the tank, constituting something which has to be avoided at all costs : that this material be confined, because it would increase drastically the emition of energy, due to the begining of a "nuclear criticality".
Indeed, a nuclear reactor is a place where a chain reaction occurs, which must be careffuly controled ; these fissile metal rods hanging like hams in the reactor's tank. Around them circulates a fluid which collects calories (water under 150 bars, in the case of PWR : pressurized water reactors). This water gets in the tank under a temperature of 295°C et gets out of it at 330°C. The flow rate is significant : 60,000 cubic meter per hour, that is sixteen cubic meter per second. In this configuration, it has been decided to isolate this primary system from the second one, coupled to the first thanks to an exchanger, and which is sent to the gas turbine, operating an electric generator.
In purple : the primary circuit of pressurized water, circulating in the containing bulding of the reactor's core. In blue and red, the secondary circuit. From the exchanger, located in the containing building, this water (dark blue in the liquid state) moves to gas steam state. Then, this steam operates a two stage gas turbine : high and low pressure. And then, the steam, expanded and cooled down, go through a condenser, where it liquefies again.
A system which produces energy has always a hot source and a cold source. The hot source, it's the "fuel rods" in the reactor's core, being swimming in pressurized water, in which the fission reactions occurs, that releases energy. The cold source, it's the atmospheric air (for reactors which uses this system of cooling). The both first circuits are closed and are coupled to a third one, in contact with the atmospheric air, thanks to very huge cooling towers which we can see, flanking the French nuclear plants.
Water streams along the internal side of these towers, openned at their bottom to allow air to circulate inside them. That's how this water transmits the heat collected in the condenser to the air going up in the tower. On it's way, a part of the water is vaporized (500 litre par second). That's why it's necessary to have a water supply close to the plant (a river or a sea). This vaporized water which made the towers topped by a steam plume, when the reactor works.
That's how 70% of the heat produced goes into the atmosphere (or in the river, the sea, if the cold source is of this nature). The yield of a reactor isn't over 30%.
There are 58 pressurized water reactors in France. A list of French reactors (in French).
Let's move on to the boiling water reactors, of the same type than those of the Japanese plants.
Like you, I discover and try to explain. The diagram is the following one:
The comparition with the former diagram is immediate. There is only one closed circuit left. It's the water which is sent into the reactor's core which is steamed and which is directly directed to the two stage gas turbine. On the left (1), the core, in its metal shell. In (2) the nuclear fuel. In (3) the control bars which have to go up and cannot anymore, in this set-up, fall under gravity in case of emergency.
The water in liquid form (blue) is more heat conductive than steam (in red, in the upper part of the core).
At the outlet of the turbine the water returning into the liquid form, in the condenser, appears in purple. There is no cooling tower. It's sea water, in grey, which is sent into the condenser.
To do so, we use control bars (for example in cadmium) which absorb the neutrons, but without creating new nuclear reactions which would release energy. When these bars are put completely down (or put completely up, in the case of Japanese set-up), the activity of the reactor is reduced ten times in comparition to its nominal power. In French reactors, the necessary time to put the bars down under gravity is of few seconds, in case of emergency. Twenty seconds in the case of Tchernobyl. The bars of the Japanese reactor are put up thanks to worm drives (see the PDF file : I am not making up anything).
On the contrary, it's when the bars are put up (or put down conserning the Japanese set-up) that the reactor starts, during its ignition. That's when one can say that "the reactor diverges".
If any failure is noticed in the evacuation system of the heat produced inside the reactor's core, where are the bars, it's necessary to either operate the emergency pumping system, or reduce drastically the produced power by puting down (or up for Japanese set-up) the control bars.
The production of electric energy is carried out thanks to alternators, driven by gas turbines. The steam which circulates in these turbines must be, at the outlet, transformed into liquid form, in a condenser. These condenser are these high towers that we can see, flanking the place containing the reactor, in France. The steam condenses into it and is recovered in the lower part of the tower. A part of the water evaporates, this loss being of 500 litres per second.
There is no such structure in Japanese reactors. Why? Because they use sea water to do this refrigeration. For economical and yield reasons, the Japaneses installed their reactors close to the ocean, which is a pretty dogshit, in a country where coasts can be hit by tsunami.
I imagine that engineers studied these plants in relation to some risks. Each Japanese nuclear reactor is build respecting anti-seismic standards. These ones correspond to a magnitude of 7 on the Richter scale, which is equivalent to a possible horizontal acceleration of one "g". The technique consists in puting the building on something like "cylinder-blocks", but much bigger.
Click on the link. You will see, in the middle of the page, that a seism of magitude 8.9 can create damage several thousand kilometers across the epicenter. It's what happened, the epicenter being located on the border between two plates, 140 km away.
Roughly, the magnitude is the logarithmic measure of the power of a seism (which has to be corrected, considering the duration of the tremors and the type of the involved waves).
