TECHNOLOGY

Generation II

PWR (Pressurized Water Reactor)

Figure 13. Schematic diagram of PWR construction
Source: "Power Reactors - Characteristics. 2010 WNA Pocket Guide", World Nuclear Association, July 2010 [25]

PWR (Pressurized Water Reactor) is water cooled and moderate reactor. It has a endure vessel to ensure high pressure of collant in the primary cirucit. Only 5%-evaporation of coolant in the core is allowed. Steam has a significant worse cooling parameters and its apearing in the primary circuit can cause reactor overheating and disturbance while operating . Heat from the core is passed to collant, so water has a very high temperature (about 300ºC). Therefore, to avoid the evaporation, high pressure at level 15 - 20 MPa is needed. Pressuriser controls pressure in the primary circuit. Steam is produced indirectly. Water flowing through the core, transfer heat in steam generator to the secondary circuit, where a turbine and a condenser are located. Existing of two separated circuits brings very important advantage of PWR - water in secondary circuit is devoid of fission, radioactive products. For that reason biological shield have to contain only primary circuit with reactor, pumps, pressurisers and steam generators. It is important to admit, that for water flow required in the core, high power pumps are necessary. However their maximum power are limited. Additionally, water warming up in the core is only by 20 - 30 ºC. Thus primary circuit is most often separated in a few loops (usually 2,3,4 but also 6 as in WWER). Characteristic of PWR is substantial power density at level of 100 MW/m3 and fuel burn-up at 40 MWd/kg. They are the highest values among thermal reactors. These features together with a quite simple and compact construction has made PWR the most widespread asset, with number of 265 reactors operating in the world. Their net efficiency is around of 30 - 33 %. PWR uses enriched fuel in uranium dioxide. An enrichment level is 3 - 4 % U-235. [15],[16],[21],[22],[24],[31]

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