school energy&environment

The past and the future of reactors

Nuclear reactors can be classified into four generations, depending on some common characteristics and depending on the period in which they were designed and built.
Currently, 436 reactors, mainly of the first and second generation, and some units of the third generation are operating.
The first generation includes prototypes and reactors for the production of electric power or plutonium for nuclear weapons, designed and built before the 70s. Generally these reactors are characterized by low thermal power which, in the case of commercial power reactors means power generally lower than 300 MWe. In Italy, there are three nuclear power plants (Latina – 210 MWe, Garigliano – 160 MWe and Trino 270 MWe) which we can consider of the first generation. The plants were shut down in 1986 and at present are being dismantled.
The second generation mainly includes light water reactors, built and utilized starting from the 70s and 80s and which are still operating. Generally these reactors are characterized by  electric power ranging from 300 MWe to 1000 MWe.  In Italy, the nuclear power plant in Caorso (860 MWe) can be considered a second generation reactor even if at present it is shut down and it  is being dismantled.
The third generation refers to the advanced type of rectors which derive from the optimization, in terms of economy and safety, of the current light water reactors. Generally, third generation reactors are characterized by electric power over 1000 MWe. Often 3+ generation reactors are also mentioned. These include  systems that may be introduced in the next 10-15 years, and therefore much before the fourth generation reactors, and meanwhile, these can also lead to advantages in the development of the same.
The  fourth generation includes innovative nuclear systems which probably will reach a technical maturity after 2030. These nuclear systems are designed to supply energy in a very competitive manner from an economic point of view, and to extend and improve safety in case of accidents, to minimize radioactive waste, (in particular waste that remains radioactive for a long time), and to promote the rational use of natural resources (with a greater exploitation of fertile and fissile materials), to produce hydrogen directly (without having to pass through the production of electric energy) and to guarantee greater reliability.
Source: Agi Energia