# A Global Review of PWR Nuclear Power Plants
## 3 Discussion
### Technical Aspect  
If we analyze the different relationships throughout the evolution of American, French, Russian, and Chinese PWR designs (Figure 11), we observe the existence of different technical influences throughout history, which have given rise to a large number of variety of designs with different related technical aspects. The beginnings of the PWR design are found in the different Westinghouse versions, in which both the number of loops and the size of the main components (reactor vessel, steam generator, reactor coolant pump and fuel assemblies) increased as new reactors were redesigned. These changes mainly favored an increase in electricity generation capacity. As has already been shown, the 2-loop Westinghouse PWR was the reference for the development of two fundamental PWR designs in Generation II: Babcock & Wilcox and Combustion Engineering CE80. Subsequently, CE80 was the reference model for the development of the Korean design OPR1000. However, these designs have as a fundamental difference the incorporation of a second cold branch in each of the loops. Therefore, this technical modification involved the second RCP. In the case of Babcock & Wilcox, another fundamental modification of the original design was the addition of a once-through steam generator. All these modifications again meant an increase in power generation capacity. Initially, Framatome opted for collaboration with Westinghouse to develop an entire nuclear industry around PWR design. Within Generation II, the French CP0 series features the 3-loop Westinghouse design, while the following CP1 and CP2 begin to include aspects typical of the French nuclear industry. These changes were further noted in the later P4 series--still in collaboration with Westinghouse--and on French P'4 and N4--100%. These new PWR series increase primary circuits and power generation capacity to 4, but also expanded design safety, for example, increasing the redundancies of safety systems or improving the strength of the containment building. In the case of the Russian VVER versions, it is more difficult to find similarities with other, Western PWR versions, since these designs have characteristics and differentiating aspects: (i) the hexagonal geometry of their fuel elements; (ii) the horizontal steam generators; and (iii) the increase in the number of loops. Lastly, the Chinese nuclear industry has been able to join this technological race, despite being 20 years behind. Initially, it opted for collaboration with the great western powers to develop the first PWR Generation II designs, but nowadays it has been able to generate enough autonomy to develop its designs. To know more about this topic, the main parameters of the final Generation II designs are described in Table 2.  
Figure 11: Evolution of PWR designs in the United States, France, Russia, and China. In Generation III, the differences between the current PWR designs are maintained, although it is possible to establish certain relationships between the reference designs: AP1000, EPR, VVER-1200, HPR1000, and CAP1400 [46; 47]. Thus, according to the data collected from [15; 46; 48], the main parameters of these designs are described in Table 3. Furthermore, in these PWR Generation III the core damage frequency considering the contribution from internal and external events is less than \(10^{-5}\) events per reactor-year. Westinghouse continues its commitment to the inherent safety--or passive safety--and the modular construction and simplicity of the AP1000 design. This AP1000 design is the reference for the Chinese PWR Generation III design, the CAP1400. The CAP1400 maintains the AP1000 design philosophy, increasing electrical generating capacity. Both designs, AP1000 and CAP1400 have a core-catcher; if there was a core meltdown, the core would be \"caught\" and prevented from entering the environment. In the case of the Russian VVER-1200, this design has technical aspects similar to the French EPR, e.g., 4 independent trains of emergency safeguards and double containment building.