Pressurized water reactors coolant pumps

Fig. 1. Pressurized water reactor (PWR) coolant system having U-tube steam generators typical of the 3—4 loops in nuclear power plants. PWR plants having once-through steam generators contain two reactor coolant pump-steam generator loops. CVCS = chemical and volume-control system.

Thermocyclic cracks were revealed in pipes connecting a reactor with pressurizers, in internal headers for water supply from purification system to reactor coolant pumps, in internal shells of pumps flow chambers, etc. The indicated defects became the reason for in-depth analytical and experimental studies of equipment operating conditions in the propulsion and test reactor plants, particularly thermal and strain parameters monitoring. 

Two-circuit reactor plant (RP) with a vessel-type pressurized water reactor is used for floating power unit of nuclear head and power station. Basic RP components reactor, steam generators and primary coolant pumps are incorporated by pressure nozzles in a compact steam-generating block. KLT-40C RP characteristics are given in Table 1. 

Provide sufficient pressurizer heater capacity to heat up the pressurizer, filled with water at the zero power level, at a rate that ensures a pressurizer temperature (and thus pressure) which will maintain an adequate degree of subcooling of the water in the reactor coolant loop as it is heated by core decay heat and/or pump work from the reactor coolant pumps. 

In a nuclear power station, there are several ion-exchange systems for water clean-up. In a typical BWR there are purification circuits after the steam condenser, in a small stream from the reactor vessel and for the water in the fuel storage pool. In a pressurized water reactor (PWR), part of the coolant in the primary circuit is withdrawn, cooled, and pumped through an ion-exchange filter. As indicated by the word filter, these ion exchangers are also used to remove particles from the liquids. They often consist of mixed cation and anion exchangers that are very finely ground bead sizes of 400 mesh are common. 

Figure 1.1. Four-loop primary coolant system of a 1300 MWe pressurized water reactor a) Reactor pressure vessel b) Steam generator c) Reactor coolant pump d) Pressurizer e) Pressurizer relief tank (Meyer, 1991)...

The Fixed Bed Nuclear Reactor (FBNR) concept assumes the use pressurized water reactor (PWR) technology, but incorporates hi temperature gas cooled reactor (HTGR) type fuel and the concept of a suspended fixed bed core. Spherical fuel elements are fixed in the suspended core by the flow of water coolant. Any accident signal will cut off the power to the coolant pump causing a stop in the flow. This would make the fuel elements fall out of the reactor core, driven by gravity, and enter a passively cooled fuel chamber where they would reside in a subcritical condition. The Fixed Bed Nuclear Reactor (FBNR) is a simplified version of the fluidized bed nuclear reactor concept [XII-1 to XII-9]. In the FBNR, spherical fuel elements are in a fixed position in the core therefore, there is no concern about the consequences of multiple collisions between them, an issue that may be raised about the fluidized bed concept. Relatively little work has been done for the fixed bed nuclear reactor so far, but the experiences gained from the development of a fluidized bed reactor can facilitate the development of the FBNR. 

Severe Accident Before Core Damage Core Cooling at High Pressure (maintain reactor coolant) PCIV (PCV Boundary) IC High Pressure Make-up Water Pump RCIC HPCF ADS High Pressure Sequence... 

Figure 2.4-8 depicts the condition in the reactor coolant system at 90 min (1 h 30 min). The reactor coolant pressure was 1050 psig. The pressurizer was nearly full. The loop B reactor coolant pumps were off, the B steam generator was isolated, and the steam and liquid phases had separated in loop B. The reactor coolant pumps in loop A were still on, circulating the steam-water mixture through steam generator A. 

At about 120 min (2 h), a conference phone call began between the control-room technical superintendent and (at their homes) the station superintendent, the vice president of generation, and the Babcock Wilcox site representative. The conference call lasted 38 min. Conferees realized that something was abnormal since the reactor coolant pumps were off yet they were unable to get a steam bubble in the pressurizer. The blown out rupture disk on the reactor coolant drain tank and the water on the reactor building floor did not seem surprising, since this had happened before. The condition of the block valve upstream of the PORV was questioned. It was reported to be shut, but it was not. The conferees decided to restart a reactor coolant pump, and all officials planned to report to the control room. 

A Steam cooled fast reactor is defined as one in which the core inlet coolant is steam , not water. Blowers are required for steam cooled reactors instead of reactor coolant pumps. The pumping power of blowers is huge. Some supercritical pressure water cooled reactors have adopted pressure tubes instead of the RPV and have separate moderator and coolant. Indirect cycle reactors with a RPV are also found. 

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