By the way ... what is Nuclear exactly?

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Grelinette
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Re: By the way ... what is Nuclear exactly?




by Grelinette » 18/11/17, 15:09

moinsdewatt wrote:
Grelinette wrote:There are some values ​​on the internet, of the order of 300 to 400 degrees in the primary circuit, ie the circuit whose water will directly recover the heat produced by the nuclear reaction, (See the EDF website) ... while the nuclear reaction is capable of producing some 15 000 000 of degrees Celsius. (We "play" with fifteen million degrees to use 300! : Shock: ).


No, there is nowhere 15 000 000 of ° C in a fission reactor.

You have not understood anything about what happens in a fission reactor. Review Wikipedia.

Sorry, I'm not an expert on the subject, and I'm waiting for this type of discussion to better understand what nuclear is, but especially, apart from the many risks and dangers known and inherent to this energy, why does this subject give rise to so many oppositions and disagreements and with as much virulence, against the background of exchanges of figures and information that are systematically questioned? ? !!! : Shock:
(The debates on other sons, and on this one also, are blatant examples).

For the neophyte that I am it is very difficult to get an idea between those who say that nuclear energy is cleaner and less dangerous than others, and others who claim that the exploitation of this energy is not only more polluting and can incidentally heavily burden the future of our planet, even destroy it ... Uh, well, yes, who says the truth, who should I believe? ... :?

Having said that, by reading the discussions of this forum on the subject of nuclear power, discussions which obviously involve specialists, I note on the one hand that ALL the data put forward by one and the other are always systematically contradicted and subject to opposition, and on the other hand, that it is very difficult to have reliable information, even by searching the web.

Public chat Wiki I read this:
Chapter: Fusion Mechanism: ...
Very high temperature: The energies necessary for fusion remain very high, corresponding to temperatures of several tens or even hundreds of millions of degrees Celsius depending on the nature of the nuclei (see below: fusion plasmas). In the Sun, for example, the fusion of hydrogen, which results, in stages, in the production of helium takes place at temperatures of the order of fifteen million kelvin, but according to different reaction patterns of those studied for the production of fusion energy on Earth. In some more massive stars, higher temperatures allow the melting of heavier nuclei.


Certainly, I misread and the "hundreds millions of degrees Celsius" correspond to the "necessary" energies (without really knowing if this is the temperature that must be supplied to launch the reaction, or if it is that of the reaction itself) but that does not change much to my basic (naive) observation which is that "we play with millions of degrees to finally use only the few 300 ° necessary to heat the water of the primary circuit ".

Moreover, here is another thing that I do not quite understand: how can a positive global balance, in terms of energy produced and usable, if we must provide very high temperatures to finally recover very low, any proportion grade (330 °)? ...
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Re: By the way ... what is Nuclear exactly?




by Christophe » 18/11/17, 15:21

moinsdewatt wrote:The document you mentioned also says 6g CO2 by KWh according to EDF and 35g for the ökö institute.
Bad. It's not much.


What document?
Who are you answering?
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Olivier22
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Re: By the way ... what is Nuclear exactly?




by Olivier22 » 18/11/17, 16:34

Grelinette wrote:Public chat Wiki I read this:
Chapter: Fusion Mechanism: ...
Very high temperature: The energies necessary for fusion remain very high, corresponding to temperatures of several tens or even hundreds of millions of degrees Celsius depending on the nature of the nuclei (see below: fusion plasmas). In the Sun, for example, the fusion of hydrogen, which results, in stages, in the production of helium takes place at temperatures of the order of fifteen million kelvin, but according to different reaction patterns of those studied for the production of fusion energy on Earth. In some more massive stars, higher temperatures allow the melting of heavier nuclei.


Certainly, I misread and the "hundreds millions of degrees Celsius" correspond to the "necessary" energies (without really knowing if this is the temperature that must be supplied to launch the reaction, or if it is that of the reaction itself) but that does not change much to my basic (naive) observation which is that "we play with millions of degrees to finally use only the few 300 ° necessary to heat the water of the primary circuit ".

You confuse fusion and fission.
In today's nuclear power plants, fission is used. The principle is to explode atoms by swallowing too many neutrons for their small carcass.
By bursting they release in turn neutrons, which will explode the atoms next door etc. So it's very easy to operate, the reaction is self-sustaining, it just has to regulate it by trapping part of the neutrons (I do not know if you saw my big explanatory post on page 3 ...)

Fusion is something else: combine 2 atoms to form only 1. For that you have to project them against each other with enormous energy, from where the millions of degrees necessary.

It is not used industrially yet, it is under study. The difficulty is precisely the temperature that must be maintained, we have not yet materials capable of supporting that.
We hope to get there because it works with fuels much easier to find, it releases a lot of energy and it produces almost no radioactive waste.
Grelinette wrote:Moreover, here is another thing that I do not quite understand: how can a positive global balance, in terms of energy produced and usable, if we must provide very high temperatures to finally recover very low, any proportion grade (330 °)? ...
You boil 1L with water.
You spend 1 joule to turn on the gas (spark, 10000 ° C).
The gas burns at 1500 ° C
Water boils at 100 ° C
At the end you have recovered 4185 joules in the pan against only 1 joule provided to initiate the reaction.
Ben for fusion is the same, it's just the temperatures that change.

You really have to stop confusing temperature and energy. Temperature is a quantity, energy is a quantity. The balance is done on quantities.
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Re: By the way ... what is Nuclear exactly?




by sen-no-sen » 18/11/17, 17:38

Grelinette wrote:
moinsdewatt wrote:
(...) but that does not change much to my basic (naive) observation which is that "we play with millions of degrees to finally only use the few 300 ° necessary to heat the water in the primary circuit ".


The best thing is that you take off your head this story of millions of degrees.
Such temperatures are possible in the case of nuclear fission only in the context of a nuclear explosion (bomb A), which corresponds to a maximum dissipation of energy in a period of ultra-short time.
In a nuclear power plant reactor the opposite is desired: much lower temperatures, no more than 300C ° in a PWR (pressurized water reactor) and less than 700C ° in a breeder reactor as was super-phoenix, but over a long period of time.


As mentioned above Olivier22it is in the context of thermonuclear fusion that we try to maintain temperatures of several million degrees, this technology is currently not operational, if you want more information there is a subject dedicated to the competition of several laboratories in the world:https://www.econologie.com/forums/energies-fossiles-nucleaire/la-course-a-la-fusion-nucleaire-t15153.html?hilit=la%20course%20a%20la%20fusion
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Re: By the way ... what is Nuclear exactly?




by Ahmed » 18/11/17, 18:23

Grelinette, you write:
For the neophyte that I am, it is very difficult to get an idea between those who say that nuclear energy is clean and less dangerous than others and others who claim that the exploitation of this energy is not only more polluting and can incidentally heavily burden the future of our planet, even destroy it ... Uh, well, yes, who says the truth, who should I believe? ... :?

You underline an important point here: the discussions have often become bogged down in debates by contradictory experts, while the substance of the problem is political (not in the sense of political politics) and depends on a choice of society, which explains why the passionate nature of the debate. Nuclear power represents a technical turning point which implies a centralized and strong state structure, the pre-eminence of technocracy and police control: a true democratic choice is therefore excluded and opponents necessarily classed as "enemies of progress".
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Re: By the way ... what is Nuclear exactly?




by moinsdewatt » 18/11/17, 20:29

Grelinette wrote: [

Certainly, I misread and the "hundreds millions of degrees Celsius" correspond to the "necessary" energies (without really knowing if this is the temperature that must be supplied to launch the reaction, or if it is that of the reaction itself) but that does not change much to my basic (naive) observation which is that "we play with millions of degrees to finally use only the few 300 ° necessary to heat the water of the primary circuit ".

Moreover, here is another thing that I do not quite understand: how can a positive global balance, in terms of energy produced and usable, if we must provide very high temperatures to finally recover very low, any proportion grade (330 °)? ...


NO.

Nuclear power plants around the world are at fission of Uranium. No fusion (which otherwise do not fuse with uranium).
So no '' millions of ° C ''.
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