As with any human activity it is important to know, a nuclear fission plant carries risks and benefits. Risks must be anticipated and analyzed in order to be mitigated. All those systems designed to eliminate or at least minimize these risks are called protection and control systems. In a nuclear power plant for civil use, an approach called defense in depth is used. This approach follows a multiple barrier design to achieve that purpose. A first approximation to the different barriers used (each of them multiple), from outside to inside could be:

In addition, it must be planned what to do in the event that all or several of these levels fail due to any circumstance. All workers, or other people living nearby, must have the necessary information and training. There must be emergency plans that are fully operational. For this it is necessary that they be periodically tested through simulations. Each nuclear power plant has two emergency plans: one internal and one external, the external emergency plan including, among other measures, evacuation plans for the nearby population in case all else fails.

Although the safety levels of third generation reactors have increased considerably compared to previous generations, it is not expected that the defense in depth strategy will change. For their part, the designs of future fourth-generation reactors are focusing on making all safety barriers foolproof, relying as much as possible on passive systems and minimizing active ones. Likewise, the strategy followed will probably be defense in depth.

When a part of any of these levels, composed in turn of multiple systems and barriers, fails (due to manufacturing defect, wear or any other reason), a notice is produced to the controllers who in turn communicate it to the resident inspectors at the nuclear power plant. If the inspectors consider that the failure may compromise the safety level in question, they raise the notice to the regulatory body (in Spain the Nuclear Safety Council (CSN). These notices are called notifiable events.[5][6]​ In some cases, when the failure can cause some operating parameter of the plant to exceed the Technical Operating Specifications (ETF) defined in the design of the plant (with safety margins), an automatic stop of the chain reaction called SCRAM occurs. In other cases, the repair of that part in question (a valve, a sprinkler, a gate,...) can be carried out without stopping the operation of the plant.

If any of the barriers fail, the probability of an accident occurring increases. If several barriers fail at any level, the breakdown of that level may eventually occur. If several of the levels fail, an accident may occur, which can reach different degrees of severity. These degrees of severity were organized into the International Nuclear Accident Scale (INES) by the International Atomic Energy Agency (IAEA) and the Nuclear Energy Agency (AEN), with the scale starting at 0 (no significance for safety) and ending at 7 (serious accident). The incident (so called when they are at grade 3 or lower) Vandellós I in 1989, classified a posteriori (the scale did not exist that year in Spain) as grade 3 (major incident).[7]​.

The breakdown of several of these barriers (there was no independence from the government, the reactor design was positive reactivity, the plant did not have a containment building, there were no emergency plans, etc.) caused one of the most serious accidents: the Chernobyl accident, level 7 at the INES. For similar reasons (the retaining wall was only 8 meters high despite knowing the presence of tsunamis larger than 38 meters and the location of several critical systems in easily flooded places) another serious accident of magnitude 7 occurred: The Fukushima I nuclear accident.[8]​.

Nuclear power plants in Spain:[9]​.

Abandoned projects. Nuclear moratorium:

Plants dismantled, in the process of dismantling or permanently stopped due to license expiration:.

Nuclear power plants in Argentina

Atomic Centers:.

Nuclear power plants in Mexico

Atomic Centers:.

Nuclear power plants: present and past

By analyzing the evolution of the number of nuclear power plants in the world during recent decades, we can analyze the change in mentality of countries regarding this type of energy. It can even be said that through the number of nuclear power plants we can read the events that have marked these last 60 years.

Today there are 444 nuclear power plants in the world, accounting for 17% of global electricity production. The country that currently has the most is the US with 104, but more surprising are the 58 power plants in France, more than half that of the US with almost 15 times less surface area. Although Japan is not far behind with 54 (although they are not currently in operation due to the cessation decreed by the government as a result of the Fukushima accident), or South Korea with 21 in less than 100,000 km². Currently Spain has 7 nuclear reactors. The accident at the Fukushima plant has recalled ghosts of the past, giving the nuclear debate a hot topicality.

Las centrales nucleares presentan una serie de ventajas y desventajas como fuente de generación de energía eléctrica.

Advantages

One of the advantages of current nuclear reactors is that they emit almost no pollutants into the air (although small amounts of radioactive gases periodically emerge), and the waste produced is much smaller in volume and more controlled than the waste generated by plants powered by fossil fuels. In those conventional thermal power plants that use fossil fuels (coal, oil or gas), greenhouse gases (CO mainly), gases that produce acid rain (SO mainly), carbon, heavy metals, thousands of tons of ash annually, and even concentrated natural radioactive material (NORM) are emitted. In a nuclear power plant, the solid waste generated is on the order of a million times smaller in volume than the pollutants in thermal power plants.

The enriched uranium used in nuclear power plants is not suitable for building a nuclear weapon or for using uranium from them. For this, the reactors are designed in high enrichment cycles or designs such as RBMK type reactors used for the generation of plutonium are used.

Lately, assisted fission plants are being investigated, where part of the most dangerous waste would be destroyed by bombardment with particles from an accelerator (probably protons) that, by spallation, would produce neutrons that in turn would cause the transmutation of those most dangerous isotopes. This would be a kind of self-maintained radioactive waste neutralization center. The performance of these plants would in principle be lower, given that part of the energy generated would be used for the transmutation of waste. It is estimated that construction of the first transmutation reactor (Myrrha) will begin in the year 2040.

Disadvantages

The danger to the population comes from several factors: 1) accident at an atomic power plant, 2) terrorist attack, 3) dangerousness of waste and its high environmental contaminating power, 4) nuclear landfills, 5) possible diversion of waste for the production of weapons of mass destruction.

It is worth clarifying that the waste is not useful for generating nuclear bombs and its waste is stored for a sufficient period of time so that it has a zero or minuscule radioactive load and terrorist attacks are not the fault of nuclear reactors, only of irresponsible states and terrorists.

Nuclear reactors generate radioactive waste. Some of them have a high half-life, such as americium, neptunium or curium, and high toxicity. Detractors of nuclear energy emphasize the danger of this waste that lasts hundreds and even thousands of years.

Some nuclear reactors were used to generate plutonium-239 used in nuclear weapons. Civil reactors generate plutonium but plutonium 239 (required in nuclear weapons) appears mixed with high proportions of plutonium 240, 238 and 242, making it unviable for military use.

The most serious nuclear accidents have been: Mayak (Russia) in 1957, Windscale (Great Britain) in 1957, Three Mile Island (United States) in 1979, Chernobyl (Ukraine) in 1986, Tokaimura (Japan) in 1999 and Fukushima (Japan) 2011.

The danger of nuclear waste is a highly controversial topic. These are usually associated with the generation of nuclear fission energy, however there are countless radioactive sources used in various uses that are also buried in nuclear cemeteries. Most countries have national companies in charge of managing this waste. In Spain, nuclear power plants pay a fee that goes to a fund for the management of this waste and the dismantling of nuclear power plants when they end their life cycle. Currently there is a definitive storage facility for the burial of spent fuel (Onkalo Spent Nuclear Fuel Reservoir); previously, it was usually kept in pools at the reactor sites or in centralized warehouses. For many, this is the most reasonable option since the spent fuel preserves 95% of the uranium, which will allow its reuse in the future. In fact, some countries already do it, but the technique is expensive. Work is being done to make it cheaper, as is intended by the BN-800 Nuclear Reactor, which has a 1200 MW brother (BN-1200 Nuclear Reactor) under construction, whose objective is to make profitable and make a commercial reactor model that is fed by waste. nuclear reactors, reduce their radioactivity and at the end of the cycle in this type of reactor, be ready to be used again in a conventional nuclear reactor, this cycle would be repeated until the Uranium and Plutonium of the nuclear fuel is exhausted, which will turn it into waste again with the exception that its radioactivity will be substantially lower.

As with any human activity it is important to know, a nuclear fission plant carries risks and benefits. Risks must be anticipated and analyzed in order to be mitigated. All those systems designed to eliminate or at least minimize these risks are called protection and control systems. In a nuclear power plant for civil use, an approach called defense in depth is used. This approach follows a multiple barrier design to achieve that purpose. A first approximation to the different barriers used (each of them multiple), from outside to inside could be:

In addition, it must be planned what to do in the event that all or several of these levels fail due to any circumstance. All workers, or other people living nearby, must have the necessary information and training. There must be emergency plans that are fully operational. For this it is necessary that they be periodically tested through simulations. Each nuclear power plant has two emergency plans: one internal and one external, the external emergency plan including, among other measures, evacuation plans for the nearby population in case all else fails.

Although the safety levels of third generation reactors have increased considerably compared to previous generations, it is not expected that the defense in depth strategy will change. For their part, the designs of future fourth-generation reactors are focusing on making all safety barriers foolproof, relying as much as possible on passive systems and minimizing active ones. Likewise, the strategy followed will probably be defense in depth.

When a part of any of these levels, composed in turn of multiple systems and barriers, fails (due to manufacturing defect, wear or any other reason), a notice is produced to the controllers who in turn communicate it to the resident inspectors at the nuclear power plant. If the inspectors consider that the failure may compromise the safety level in question, they raise the notice to the regulatory body (in Spain the Nuclear Safety Council (CSN). These notices are called notifiable events.[5][6]​ In some cases, when the failure can cause some operating parameter of the plant to exceed the Technical Operating Specifications (ETF) defined in the design of the plant (with safety margins), an automatic stop of the chain reaction called SCRAM occurs. In other cases, the repair of that part in question (a valve, a sprinkler, a gate,...) can be carried out without stopping the operation of the plant.

If any of the barriers fail, the probability of an accident occurring increases. If several barriers fail at any level, the breakdown of that level may eventually occur. If several of the levels fail, an accident may occur, which can reach different degrees of severity. These degrees of severity were organized into the International Nuclear Accident Scale (INES) by the International Atomic Energy Agency (IAEA) and the Nuclear Energy Agency (AEN), with the scale starting at 0 (no significance for safety) and ending at 7 (serious accident). The incident (so called when they are at grade 3 or lower) Vandellós I in 1989, classified a posteriori (the scale did not exist that year in Spain) as grade 3 (major incident).[7]​.

The breakdown of several of these barriers (there was no independence from the government, the reactor design was positive reactivity, the plant did not have a containment building, there were no emergency plans, etc.) caused one of the most serious accidents: the Chernobyl accident, level 7 at the INES. For similar reasons (the retaining wall was only 8 meters high despite knowing the presence of tsunamis larger than 38 meters and the location of several critical systems in easily flooded places) another serious accident of magnitude 7 occurred: The Fukushima I nuclear accident.[8]​.

Nuclear power plants in Spain:[9]​.

Abandoned projects. Nuclear moratorium:

Plants dismantled, in the process of dismantling or permanently stopped due to license expiration:.

Nuclear power plants in Argentina

Atomic Centers:.

Nuclear power plants in Mexico

Atomic Centers:.

Nuclear power plants: present and past

By analyzing the evolution of the number of nuclear power plants in the world during recent decades, we can analyze the change in mentality of countries regarding this type of energy. It can even be said that through the number of nuclear power plants we can read the events that have marked these last 60 years.

Today there are 444 nuclear power plants in the world, accounting for 17% of global electricity production. The country that currently has the most is the US with 104, but more surprising are the 58 power plants in France, more than half that of the US with almost 15 times less surface area. Although Japan is not far behind with 54 (although they are not currently in operation due to the cessation decreed by the government as a result of the Fukushima accident), or South Korea with 21 in less than 100,000 km². Currently Spain has 7 nuclear reactors. The accident at the Fukushima plant has recalled ghosts of the past, giving the nuclear debate a hot topicality.

Las centrales nucleares presentan una serie de ventajas y desventajas como fuente de generación de energía eléctrica.

Advantages

One of the advantages of current nuclear reactors is that they emit almost no pollutants into the air (although small amounts of radioactive gases periodically emerge), and the waste produced is much smaller in volume and more controlled than the waste generated by plants powered by fossil fuels. In those conventional thermal power plants that use fossil fuels (coal, oil or gas), greenhouse gases (CO mainly), gases that produce acid rain (SO mainly), carbon, heavy metals, thousands of tons of ash annually, and even concentrated natural radioactive material (NORM) are emitted. In a nuclear power plant, the solid waste generated is on the order of a million times smaller in volume than the pollutants in thermal power plants.

The enriched uranium used in nuclear power plants is not suitable for building a nuclear weapon or for using uranium from them. For this, the reactors are designed in high enrichment cycles or designs such as RBMK type reactors used for the generation of plutonium are used.

Lately, assisted fission plants are being investigated, where part of the most dangerous waste would be destroyed by bombardment with particles from an accelerator (probably protons) that, by spallation, would produce neutrons that in turn would cause the transmutation of those most dangerous isotopes. This would be a kind of self-maintained radioactive waste neutralization center. The performance of these plants would in principle be lower, given that part of the energy generated would be used for the transmutation of waste. It is estimated that construction of the first transmutation reactor (Myrrha) will begin in the year 2040.

Disadvantages

The danger to the population comes from several factors: 1) accident at an atomic power plant, 2) terrorist attack, 3) dangerousness of waste and its high environmental contaminating power, 4) nuclear landfills, 5) possible diversion of waste for the production of weapons of mass destruction.

It is worth clarifying that the waste is not useful for generating nuclear bombs and its waste is stored for a sufficient period of time so that it has a zero or minuscule radioactive load and terrorist attacks are not the fault of nuclear reactors, only of irresponsible states and terrorists.

Nuclear reactors generate radioactive waste. Some of them have a high half-life, such as americium, neptunium or curium, and high toxicity. Detractors of nuclear energy emphasize the danger of this waste that lasts hundreds and even thousands of years.

Some nuclear reactors were used to generate plutonium-239 used in nuclear weapons. Civil reactors generate plutonium but plutonium 239 (required in nuclear weapons) appears mixed with high proportions of plutonium 240, 238 and 242, making it unviable for military use.

The most serious nuclear accidents have been: Mayak (Russia) in 1957, Windscale (Great Britain) in 1957, Three Mile Island (United States) in 1979, Chernobyl (Ukraine) in 1986, Tokaimura (Japan) in 1999 and Fukushima (Japan) 2011.

The danger of nuclear waste is a highly controversial topic. These are usually associated with the generation of nuclear fission energy, however there are countless radioactive sources used in various uses that are also buried in nuclear cemeteries. Most countries have national companies in charge of managing this waste. In Spain, nuclear power plants pay a fee that goes to a fund for the management of this waste and the dismantling of nuclear power plants when they end their life cycle. Currently there is a definitive storage facility for the burial of spent fuel (Onkalo Spent Nuclear Fuel Reservoir); previously, it was usually kept in pools at the reactor sites or in centralized warehouses. For many, this is the most reasonable option since the spent fuel preserves 95% of the uranium, which will allow its reuse in the future. In fact, some countries already do it, but the technique is expensive. Work is being done to make it cheaper, as is intended by the BN-800 Nuclear Reactor, which has a 1200 MW brother (BN-1200 Nuclear Reactor) under construction, whose objective is to make profitable and make a commercial reactor model that is fed by waste. nuclear reactors, reduce their radioactivity and at the end of the cycle in this type of reactor, be ready to be used again in a conventional nuclear reactor, this cycle would be repeated until the Uranium and Plutonium of the nuclear fuel is exhausted, which will turn it into waste again with the exception that its radioactivity will be substantially lower.