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How nuclear fission works
An atom is made of a nucleus (composed of neutrons and protons) and electrons. If a neutron collides with a 235/92 U atom, and if the 2 or more resulting hight speed neutrons are slowed down by a moderator, a chain reactions stars, which releases energy. Used for military (nuclear bomb) or civil purposes (nuclear plant).
I. Inside a nuclear plant
Nuclear and fossil fuels plant
Differences : fuel source, fossil fuels release CO2 whereas Uranium doesn't
Similaires : steam (vapeur) is produced and turns turbine connected to an alternator
Moderator in the plant
The moderator is heavy water (2/0 H2O), which is 10% heavier than ordinary water (1/1H2O).
Reactor in the plant
The reaction can be stopped with control rods (barre de contrôle), which can absorb neutrons.
II. Pros and cons
Advantages
-Creates most of our electricity
-It doesn't produce CO2
-It provides a relative energetic independence
Drawbacks
-Very dangerous in case of a accident (Fukushima, Chernobyl)
-It produces dangerous radioactive waste (déchets)
III. Nuclear waste classification
Low-level waste
Property : contains enough radioactive material to require action for the protection of people, but not so much that it requires shielding (blindage) in handling (manipulation) or storage.
Origin : comprises paper, tools, clothing, filters... which contain small amounts of mostly short lived radioactivity.
Intermediate-level waste
Property : sufficiently radioactive to require both shielding (blindage) and cooling (refroidissement), generates > 2kW/m3 of heat and has a high level of long lived alpha-emitting isotopes.
Origin : includes resins, chemical sludge (boue chimique) and metal reactor fuel cladding (gaines métalliques du combustible des réacteurs), as well as contaminated materials form reactor decommissioning (démantèlement des réacteurs).
High-level waste
Property : requires shielding. If it has more than 4000 Bq/g of long-lived (over 30y half-life) alpha emitters it is categorised as long-lived and requires more sophisticated handling and disposal (elimination).
Origin : contains fission products generated in the reactor core.
IV. Next generation : EPR (European pressurised reactor)
Qualities
-Offers a great environmental protection.
-Has a collecting area in case the reactor would melt (fondrait) and protecting walls (murs) against an aircraft crash.
-There is a cooling area in the generator and a system that prevents the building form collapsing (effondrement) bc of an earthquake (tremblement de terre).
-There are 4 subsystem working independently in order to avoid a global failure (éviter une panne totale).
EPR and currents nuclear reactors
-The electricity costs 10% lessh
-The maintenance is easier
-Requires 17% less uranium.
null
How nuclear fission works
An atom is made of a nucleus (composed of neutrons and protons) and electrons. If a neutron collides with a 235/92 U atom, and if the 2 or more resulting hight speed neutrons are slowed down by a moderator, a chain reactions stars, which releases energy. Used for military (nuclear bomb) or civil purposes (nuclear plant).
I. Inside a nuclear plant
Nuclear and fossil fuels plant
Differences : fuel source, fossil fuels release CO2 whereas Uranium doesn't
Similaires : steam (vapeur) is produced and turns turbine connected to an alternator
Moderator in the plant
The moderator is heavy water (2/0 H2O), which is 10% heavier than ordinary water (1/1H2O).
Reactor in the plant
The reaction can be stopped with control rods (barre de contrôle), which can absorb neutrons.
II. Pros and cons
Advantages
-Creates most of our electricity
-It doesn't produce CO2
-It provides a relative energetic independence
Drawbacks
-Very dangerous in case of a accident (Fukushima, Chernobyl)
-It produces dangerous radioactive waste (déchets)
III. Nuclear waste classification
Low-level waste
Property : contains enough radioactive material to require action for the protection of people, but not so much that it requires shielding (blindage) in handling (manipulation) or storage.
Origin : comprises paper, tools, clothing, filters... which contain small amounts of mostly short lived radioactivity.
Intermediate-level waste
Property : sufficiently radioactive to require both shielding (blindage) and cooling (refroidissement), generates > 2kW/m3 of heat and has a high level of long lived alpha-emitting isotopes.
Origin : includes resins, chemical sludge (boue chimique) and metal reactor fuel cladding (gaines métalliques du combustible des réacteurs), as well as contaminated materials form reactor decommissioning (démantèlement des réacteurs).
High-level waste
Property : requires shielding. If it has more than 4000 Bq/g of long-lived (over 30y half-life) alpha emitters it is categorised as long-lived and requires more sophisticated handling and disposal (elimination).
Origin : contains fission products generated in the reactor core.
IV. Next generation : EPR (European pressurised reactor)
Qualities
-Offers a great environmental protection.
-Has a collecting area in case the reactor would melt (fondrait) and protecting walls (murs) against an aircraft crash.
-There is a cooling area in the generator and a system that prevents the building form collapsing (effondrement) bc of an earthquake (tremblement de terre).
-There are 4 subsystem working independently in order to avoid a global failure (éviter une panne totale).
EPR and currents nuclear reactors
-The electricity costs 10% lessh
-The maintenance is easier
-Requires 17% less uranium.