Nuclear energy

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Nuclear energy is on the one hand the form of primary energy, which is set free with nuclear reactions, in particular with the nuclear fission and nuclear fusion. On the other hand thereby the technology and industry become the industrial production of secondary energy, as designates electric current, from nuclear energy. While nuclear fusion reactors are only in the research stage, the nuclear fission is used already for the 1950er years in nuclear power stations - predominantly using the source of energy uranium - generally speaking yardstick.

Table of contents

term history

original coined/shaped the physicist Hans Geitel 1899 the term atomic energy for the phenomena arising in connection with radioactive decay processes; later the often synonymously used terms nuclear energy , nuclear power , nuclear power and nuclear energy were added .

The use of these terms has a contentwise since Geitels of first term coinage both, and a social differentiation experience. At the same time with the increasing use of the terms atomic energy and nuclear power by nuclear power opponents these found less and less to use in economics, politics and science. Instead nuclear energy in the atomiclegal, nuclear energy and nuclear power in the scientific and economic surrounding field are used. In addition the term nuclear power is used in nuclear physics also as name for the strong reciprocal effect.

Physical background

Schematische Darstellung der Induzierten Kernspaltung
schematic representation of the induced nuclear fission

most frequently used nuclear reactions for the utilization of nuclear energy are the induced nuclear fission and the nuclear fusion.

During the induced nuclear fission the atomic nuclei of heavy uranium -, thorium - disintegrate, or plutonium - isotopes into several lighter cores, as soon as them a small activation energy - by penetration of a neutron into the core receive. The difference between the mass of the origin core and the sum of the masses of the fission products, also as mass defect admits, thereby to the equivalence of mass and energy into kinetic energy is converted. Per splitting this is about 200 MeV. Among the fission products rank also 2-3 prompt neutrons, which are set free with each splitting. These can induce and lead further nuclear fissions so to a nuclear chain reaction. The retarded neutrons resulting from radioactive decay of the fission products make a steered nuclear chain reaction possible in a nuclear reactor.

With the nuclear fusion several light atomic nuclei, like the hydrogen - isotopes deuterium and tritium, are merged to a heavier core, about a helium - isotope. Since atomic nuclei are positively charged, for it the Coulomb force , which causes a repulsion of the cores, must be overcome. In addition a high pressure and a very high temperature - about 100 million Kelvin - are necessary. As is the case for the nuclear fission by the mass defect a part of the core binding energy, depending upon reaction in the order of magnitude of approximately 3-18 MeV per fusion, is set free.

History

Otto cock and Lise Meitner in the laboratory

around 1890 were accomplished first experiments to the radioactivity. The goal Antoine Henri Becquerels, Marie and Pierre Curies and other one was the research of nuclear reactions. 1938 discovered Otto cock and Fritz Strassmann the induced nuclear fission of uranium, which 1939 were theoretically explained by Lise Meitner and Otto freshness. Together with in particular the proof furnished by Frédéric and Irène Joliot curies that a nuclear chain reaction is possible, became the practical application possibilities of the nuclear fission clearly.

first these realizations were used for the military research during the Second World War. In the context of the Manhattan project Enrico Fermi succeeded to 2. December 1942 first controlled nuclear nuclear chain reaction in a nuclear reactor in Chicago (Chicago Pile One). While the goal by Robert Oppenheimer led of the Manhattan project with the first successfully ignited atom bomb to 16. July 1945 (Trinity test) was reached, succeeded it to the German research group under Werner Heisenberg and Carl Friedrich from Weizsäcker to the end of war not to develop a functioning nuclear reactor (uranium project).

Also after the Second World War the military research was continued. Thus became to 31. October 1952 the first hydrogen bomb ignited, with which the nuclear fusion application finds. In addition, at the same time at the civilian use of the nuclear energy one researched. 1954 were taken in Obninsk with Moscow the first nuclear power station in enterprise. 1955 followed the first commercially nuclear power station in Calder, used for generation of current, resound (northwest England). In Germany 1957 with the Atomei were taken in Garching the first research reactor in enterprise. 1961 followed the first German nuclear power station in bald at the Main with an output of 15 MW.

numerous further nuclear power stations were built for nuclear power station count Rhine field into the 1960er, whereby their achievement was increased clearly. So the nuclear power station Gundremmingen, which 1966 went into enterprise, had an output of 250 MW. Into the 1970er years after the first oil crisis 1973 the building was forced in particular by nuclear power stations. The achievement of these power stations, as for instance the block B of the nuclear power station Biblis, was with 1,3 GW. With the protest of the nuclear power opponents against the building of a nuclear power station in Wyhl at the emperor chair 1975 a larger opposition developed against the civilian use of the nuclear energy in Germany. This strengthened itself still in particular by the heavy reactor misfortune in the nuclear power station Three Mile Island with Harrisburg (the USA) to 28. March 1979, at which it came to a partial core melt-through.

1983 were taken in Hamm Uentrop of the thorium high-temperature reactor THTR-300 in enterprise. This prototype was shut down after several technical disturbances six years later. Due to the political arguments around the nuclear energy no agreement could be obtained over the necessary extent of necessary repairs, why the THTR among other things for economic reasons not again in enterprise one took, but one transferred into the safe inclusion.

To 26. April 1986 occurred the disaster of Tschernobyl, with which large quantities of radioactivity were set free. In the consequence in particular the criticism increased in the use of the nuclear energy clearly in Europe. 2000 were decided in Germany on pressure of the Federal Government the door from the commercial use of the nuclear energy to approximately 2020. In this framework until already 2005 two nuclear power stations were taken by the net, the door resolution are however politically and socially further disputed. Similar the situation is for example in Italy, Belgium or Sweden. In other countries against it, in particular in the USA, the running times of existing nuclear power stations are extended or built at present (conditions 2006) new nuclear power stations (for example in India, Russia, China and Japan). In the USA an extensive development program for new nuclear power stations (the so-called „fourth generation “) was presented. In Olkiluoto (Finland) became to 12. August 2005 begun with the building of the first power station of the type European Pressurized Water Reactor (EPR) with an output of 1,6 GW; France seized the building decision for an identically constructed nuclear power station in Flamanville. (see also: Nuclear energy to countries)

economics


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Länder die Kernkraftwerke in Betrieb haben
Countries the nuclear power stations in enterprise have

the most important application of the nuclear energy are the production of electric current in nuclear power stations (KKW). Zurzeit are 442 nuclear power stations with a total output of 369 GW in 30 countries in enterprise. 135 of these nuclear power stations stands in Western Europe (124 GW), under it 17 in Germany (20 GW) and 5 in Switzerland (3.2 GW). Austria does not have nuclear power stations in enterprise. In 9 countries, under it Finland as only Western European country, are altogether 24 nuclear power stations with a total output of 20 GW in building. (Conditions October 2005)

the portion of the atomic energy of the world-wide energy production amounted to 1998 6.5% (UNDP). The atomic current portion of the world-wide generation of current amounts to about 16%. Lithuania and France with nearly 80% portion take the point places. In Western Europe about 30% of the electric current are produced by nuclear energy, in Germany 28% and in Switzerland scarcely 40%.

In Belgium, Germany and Sweden a door from the commercial use of the nuclear energy is planned.

A further application - the nuclear energy drive - became generally accepted outside from militarily used nuclear-powered submarines and ships only (partly) with ice-breakers.

To nuclear power station

see major item nuclear power station

for the production of electric current by nuclear energy nuclear power stations, special power stations, which accomplish steered nuclear chain reactions of nuclear fissions in nuclear reactors, are used. Nuclear fusion reactors still are to time in the research stage.

Technology

the production of electricity happens indirectly: The warmth, which develops during the nuclear fission, is transferred to a cooling agent - for instance water -, whereby this is warmed up. Directly in the reactor or indirectly in a steam generator develops water vapour, which propels then a steam turbine.

Begun in nuclear power stations different reactor types by the used nuclear fuels, cooling circuits and moderators to essentially differ. The most important are:

Schema eines Kernkraftwerks mit Druckwasserreaktor
Pattern of a nuclear power station with pressurized water reactor
Schema eines Siedewasserreaktors
pattern of a boiling water reactor
  • in the light-water reactor (LWR) is used „light “water< (>math \ mathrm {H_2O<}> /math) as reactor coolant and moderator. As fuel enriched uranium with 235 a around eating portion is used between approximately 1.5 and 6 per cent. The light-water reactor exists in the variants pressurized water reactor (DWR) and boiling water reactor (SWR). While with the pressurized water reactor the reactor coolant produces water vapour in a closed primary cycle circulated and with a steam generator in a secondary cycle, which propels the turbines, with the boiling water reactor the cooling agent in the reactor pressure vessel one evaporates and propels the turbines directly.
  • Since in the heavy-water reactor (HWR) the water heavy used as reactor coolants and moderator (<math> \ mathrm {D_2O}< /math>) absorbs neutrons more badly than normal water, nature uranium with a proportion at 235 U can be used of approximately 0.7 per cent as fuel.
  • The RBMK is a reactor of Soviet design, which graphite as moderator and water use as cooling agent, therefore can to the enterprise uranium with the natural isotopic distribution be used. The design makes the enterprise of these reactors very uncertain, therefore they are not no more built after the disaster by Tschernobyl in such a reactor. However still some reactors of this design with some technical improvements are further in enterprise in the area of the former Soviet Union.
  • The breeder reactor (fast breeder) produces fissile plutonium from nature uranium during the enterprise and makes thereby a higher utilization of fuel possible. As cooling agent instead of water liquid sodium is used, since for this type of reactor fast neutrons are needed.
  • The high-temperature reactor (HTR) is a German invention, with which the fuel (235 U or 232 Th) is enclosed in tennis ball-large Graphitkugeln. The graphite serves as moderator. For cooling helium is used.

To security

see major item security by nuclear power stations

the construction of a nuclear power station required - apart from the actual task to produce with the help of the nuclear reactor electric current - the emission of radioactive substances, which result from the nuclear fission, into the environment preventing.

The release of radioactivity in the normal enterprise to keep so small that after today's scientific Ernkentnissen health damage is to be excluded, is reached by closed cycles and a sufficient screen of the reactor.

In addition, the moreover one the emission must be if possible prevented by radioactivity into the environment by disturbing and accidents. By „a multi-level, errorforgiving security concept “causalities, which can lead to the Emmision of radioactivity, are to be prevented by several by each other independent measures, so that both technical errors and human failure can be intercepted.

Into modern western light-water reactors to it „a multi-barrier and a safety level concept are used “, which plan the inclusion of the radioactive materials in repeated, each other enclosing barriers, which are to ensure a sufficient integrity by a system of graduated measures.

Both as the Konstrukion of the fuel elements, and those of the reactor serve barriers. The fuel is as crystal lattice in gas-tight welded fuel rods, so that the fission products normally do not leave the fuel elements. That, consisting of 20-25 cm thick steel, reactor pressure vessel forms a closed cooling system together with the following pipings. It is, together with one, the screen of radiation serving, thermal sign, in the Containment, a reactor containment from approximately 4 cm thick steel. 1.5-2 m a thick reinforced concrete covering encloses the entire reactor containment and is effects from the outside to prevent.

In modern German nuclear power stations gives it four safety levels, which reach from the normal operation on the first levels up to the fourth level, which the effects of an incident are to be limited if possible to the plant. At the individual levels systematically a failure is subordinated, which is to be caught by suitable measures on the next level.

In order to avoid the loss of several safety systems by a common cause, it is made certain that these both redundantly, i.e. several times available and spatially and system-oriented strictly separately, and diversitär, as thus as possible on different physical fundamentals being based, are.

To fuel supply and disposal

see major item fuel cycle

fuel cycle with supply, disposal and reprocessing

for the work procedures for the supply of nuclear reactors with fuel elements serving and the necessary measures for the disposal of the radioactive waste, also the term fuel cycle one uses. Admits became the term fuel cycle in the discussion during a reprocessing.

Supply

in the fuel elements of the nuclear reactors at present the isotope 235 [[uranium becomes|U] and in mixing oxide fuel rods additionally the isotopes 239 Pu and 241 Pu as nuclear fuel uses.

While in heavy-water reactors and in breeder reactors uranium with the natural isotopic distribution can be used from 99,3% 238 U to 0.7% 235 U, the wide-spread light-water reactors need enriched uranium with a portion of up to approximately 6% 235 And.

Uranium ore is promoted both in the open mining and in the underground work. The ore is extracted husbands and the uranium chemically - usually as U3O8 -. Subsequently, the U3O8 is converted into UF6. The enrichment of 235 U takes place usually by means of gas diffusion or ultra centrifuges. The uranium is then converted as uranium dioxide, possibly together with plutonium dioxide as mixing oxide, to fuel rods. Several fuel rods are then combined into fuel elements.

Disposal

of there used up fuel elements are highly radioactive, for the evacuation and the storage special containers, for example Castor containers, are used.


Burned one down, not reprocessed fuel elements and radioactive waste from reprocessing plants faded away in storage containers in temporary storage facilities so long stored to the radioactivity so far that a dumping is possible. Zurzeit gives it world-wide still no ultimate waste disposal for highly radioactive waste. In Gorleben from 1979 to 2000 an underground salt plug was examined for its suitability as dump for all kinds of radioactive wastes, under it particularly also for fuel elements and high-radioactive wastes. The investigation of the salt plug is since then (conditions 2005) interrupted. The moratorium put on on three to ten years was set on the basis of the agreement made by the Federal Government with the power supply firms into force and serves clarifying conceptional and safety-relevant questions for the dumping.

Reprocessing

in reprocessing plants - as for instance the reprocessing plant La Hague in France - the 97% unspent uranium and plutonium contained in burned down fuel elements can be separated from the 3% fission products and higher actinides and converted to new fuel elements. The fission products and higher Aktinide constitute then the actual radioactive waste .

In Germany a reprocessing in Wackersdorf in building was, however for financial reasons was not finished.

Legal basis

flag of the IAEO

the international atomic energy organization (IAEO) is to promote the international cooperation in the area of the peaceful use of the nuclear energy and the application of radioactive substances and to prevent at the same time the abuse of this technology (in particular the pro running ration of nuclear weapons) by monitoring measures. Various international contracts like the nuclear weapon check contract and the atomic adhesion convention give appropriate guidelines.

In Germany the legal basis of the civilian use of the nuclear energy is the German atomic law (law over the peaceful use of the nuclear energy and the protection against its dangers). In Switzerland the Swiss atomic law ( Federal law over the peaceful use of the atomic energy) serves as legal basis. In Austria the commercial use of nuclear reactors is not permitted due to a national referendum.

Further regulations, like the atomiclegal covering precaution regulation (AtDeckV), convert the international guidelines in Germany. The covering precaution for a nuclear power station amounts to 2.5 billion euro, which are secured to a part as liability insurance and on the other hand part as Solidarvereinbarung among the nuclear power station operators.

The upper limit of liability with damage, which is to be attributed directly to actions of an armed conflict, from hostilities, a civil war, a rebellion or to a heavy natural catastrophe of unusual kind, is with evenly these 2.5 billion euro. For damage from other causes the operators are responsible for an unlimited period.

For the retreating longwall system of nuclear power stations the operators in Germany and Switzerland must put on a resetting by approximately 500 million euro for each nuclear power station.

Follows a large accident in Germany

the damage of an accident with substantial release of radioactivity numbered a study of the Prognos AG 1992 with up to 10.7 trillion DM, the three to the quadruple at that time annual German gross national product. In the first “German risk study” from the year 1979 provided by the society for reactor safety possible accident sequences are indicated by up to 14,500 Soforttoten and 104,000 later deaths. Also a surface up to 5600 square kilometers could be so strongly contaminated according to society for reactor safety that 2.9 million humans to be evacuated would have.

Comparison with fossil fuels (greenhouse effect)

nuclear power stations actual produces as with all power stations - the energy employment with the production of the power stations, with their enterprise (with nuclear power stations including fuel procurement and refuse disposal) and with their outline in principle with CO 2 - for setting free connected in the enterprise no CO 2, but. Those altogether (over the entire life cycle) set free CO 2 - quantity is however smaller with nuclear power stations around more as an order of magnitude than with production of the same quantity of electricity by means of conventional (fossil more fired) power stations. Nuclear power stations can be used therefore effectively for the fight of the greenhouse effect. Approximately equal high CO 2 - reduction factors can theoretically with wind force (in co-operation with existing power stations on other basis, as well as to time still smaller employment potential) and hydro-electric power plants be achieved, during other renewable energies, in particular the Fotovoltaik, only clearly smaller CO 2 - reduction factors to reach. In Germany the nuclear power stations reduce the CO 2 - setting free annually by approximately 150 million t (counted opposite hard coal; Total total 858 million t, of it 337 million t by the energy production, values in each case for the year 2000).

According to a study of the German physical society e. V. (September 2005) the following trend that knows CO 2 - reduction in the year 2020 measures becomes (in millions Tons of CO 2 per year):

  • River from renewable energies (main wind energy): Reduction around 8 to 15,
  • modernization of the fossil power stations and duplication of the gas portion on 32%: Reduction around 23,
  • introduction of alternative fuels in traffic: Reduction around 20,
  • switching the nuclear power stations and replacement off by most modern fossil power stations with gas portion of 40%: Increase around 112.

So far there is not no study with complete CO 2 - balance, since the immense expenditure of the earth movements with the dismantling - per ton uranium oxide falls between 1000 and 40.000 tons overburden on and for security with the disposal to whole ones to be seized or to become be able.

To criticism

see major item nuclear power opponent

protest in Brasília against the use of the nuclear energy

the use of the nuclear energy for the production of electric current by nuclear power opponents one rejects. They are the view that the enterprise of nuclear power stations as well as their en and disposal with nuclear fuel save irresponsible safety risks.

Already during the uranium promotion high-grade health-endangering radioactive substances were set free such as radon in large quantities. The history of the uranium mining industry in the former GDR e.g. numerous cancer illnesses of the adjoining owners and workers entailed. Plants for 235 uranium enrichment, like the German uranium enrichment plant in Gronau, could be used also for the production of nuclear weapons - capable material, with a portion of 80% 235 U.

The enterprise of nuclear power stations would be uncertainly, since a disaster was not to be excluded as in the nuclear power station Tschornobyl and it also very frequently - although usually only smaller one - incidents would give, with which partial radioactivity is set free. In particular the consequences of a largest accident which can be accepted are not answerable, since whole regions became uninhabitable.

In particular the disposal of the highly radioactive fuel elements is unsecured, since these very high radioactive half-lives have (239 Pu for example 24,000 years). Transport in Castor - and other containers is likewise not safe because of possible accidents. During the reprocessing extracted plutonium can be used for the production of nuclear weapons. In addition give it from the reprocessing plant in particular to Sellafield many medium reports that uncontrolled radioactivity would have withdrawn there and the neighbouring living families with some cases of leukaemia which can be attributed to it - illnesses of their children and seniors were confronted.

Due to the high radioactive half-life nuclear power opponents assume the period, in which radioactive waste in an ultimate waste disposal would have to be kept, is difficult-to-understand and there could be therefore no safe ultimate waste disposal.

In opposition to the nuclear power opponents the nuclear power proponents stand.

Literature

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