Feedwater pump

This approach will provide a number aecurate enough for initial planning. For detailed design, the proeess engineer should work elosely with the meehanieal engineer and/or vendor representative involved to set exact requirements, ineluding orifice type and size for the minimum flow line. Also, a eooler may be required in the minimum flow line or it may need to be routed to a vessel. For boiler feedwater pumps, a special stepped type orifice is often used to eontrol flashing. 

Figure 6,1-2 is a simplified illustration of a BWR. The pressure of the moderator-cooling water at about half the pressure in a PWR forms steam as it flows upward through the core. Steam passes through a moisture separator (shown as vertical lines just above the core) exits the containment through Main Steam Isolation Valves (MSIV) drives the turbine and generates electricity. After the steam is cooled by the turbine, it is condensed, and pumped back to the reactor by the feedwater pump. 

Trip of one feedwater pump (or condensate pump) 24. Feedwater low flow... 

Adjustable speed motor driven feedwater pumps and high-capacity control rod drive pumps with backup power improve the safety margin by improving correct operator response to non-routine events. 

Resin blockage caused trip of the condensate pump and main feedwater pumps,... 

F.xamples of initiating events considered in five PRAs are provided by Joksimovich et al. (lhS3) and presented as Table 6.3-5. The occurrence frequencies vary from a high of 3.7/yr for turbine and reactor trip at Zion to a low of lE-6/yr for a large steam line break outside of containment at Big Rock Point. Another low frequency is 2E-6/yr for ATWS from the loss of one feedwater pump, also at Big Rock Point. Surprisingly, these are less than a large LOCA (IE- 5/yr) at the same plant. Except for Big Rock Point, this table provides no information on externalities. 

Turbine-driven auxiliary feedwater pump reliability-from design and maintenance is... 

Four onsite power diesel generators that start automatically on loss of offsite power to reduce the frequency of the loss of station AC by an order of magnitude compared with ( , NDl 1 -6. This with the diesel driven auxiliary feedwater pump provides ample recovery imie... 

This is a condition which occurs when the feedwater pump is unable to deliver feedwater to the boiler although the feed tank has water available. The temperature of the feed-water coupled with the possible suction effect from the feedwater pump in the line between the feed tank and the pump effectively drops the pressure, causing the feed-water to flash to steam. The pump then loses its water supply. 

These are available for steam raising up to 3600 kg/h and manufacture is to two designs. The smaller units are element boilers with evaporation less than 500 kg/h. In these, an immersed electric element heats the water and a set of water-level probes positioned above the element controls the water level being interconnected to the feedwater pump and the element electrical supply. 

The boilers are normally dispatched to site as a packaged unit with the shell and smokeboxes fully insulated, painted, and mounted on a base frame. The combustion appliance and control panel will be fitted together with the feedwater pump, water-level controls, gauges, and a full complement of boiler valves. Additional equipment may be specified and incorporated during construction. Larger boilers may have to have certain items fitted at site due to site restriction or weight. 

The second area will be feedwater pumps. It is normal to have a duplicate standby feedwater pump. Sometimes this may be two for each boiler or one duplicate pump to serve any selected boiler. These will usually require manual changeover in the even of failure of the duty pump. It is practical to automate this changeover by using pressure sensors and motorized valves. The same can apply to oil-circulating pumps, gas boosters, water-treatment plant and any other valves and motors. It is possible to do most things, but in the end there is the cost to be considered. An... 

Feedwater pumps will not normally constitute a noise problem unless the area is particularly sensitive. Two alternatives are then available. One is to install reduced-speed pumps and the other is to site the pumps in a separate acoustic enclosure within the boiler house. Oil-circulating pumps are usually low speed and, as such, do not cause a noise problem. 

Water-treatment plant may include one or more electric motors driving feedwater pumps or dosing pumps. Dosing pumps are usually very small and will not cause noise problems. Water pumps may be considered as for the feedwater pumps already described. 

Feedwater pump turbines typically receive steam from the main turbine (at the IP to LP crossover stage) at 100 to 200 psia (6.9-13.8 bar), and condense the steam to 2 to 3 inches of mercury absolute (0.07-0.10 bar) exhaust pressure, either to the main turbine condenser or to separate condensers. 

Conventional nuclear reactors and advanced breeder reactors were America s primary energy strategy since the 1950s to resolve the fossil fuel problem but when a reactor accident occurred in 1979 at Three Mile Island in Pennsylvania, public and investor confidence in nuclear fission dropped. The accident was triggered by the failure of a feedwater pump that supplied water to the steam generators. The backup feedwater pumps were not connected to the system as required, which caused the reactor to heat up. The safety valve then failed to act which allowed a radioactive water and gas leak. This was the worst nuclear power accident in the U.S., but in this accident no one was killed and no one was directly injured. At Three Mile Island faulty instrumentation gave incorrect readings for the... 

In a plant with a shaft-driven boiler feedwater pump, problems had historically occurred with failure of the bearing in the hydraulic coupling. There was no apparent cause, but throughout the 12-year life of the equipment, the failure occurred about once every 1 or 2 years and resulted in an outage of about 5 weeks. 

Concrete Shield Building 12. Integrated Head Package 22. Feedwater Pumps... 

The boiler is provided with a three-element feedwater control system, which was described in detail in Chapter 2, Section 2.2, in connection with Figure 2.1. The boiler is also provided with a variable-speed feedwater pump station, having the controls described in Chapter 2, Section 2.17.2 (see Figures 2.123 and 2.124). 

Figure 1. An abbreviated representation of a steam power plant cycle. The numbers 1,2,3,4,5,6, and 7 correspond respectively to the boiler, first turbine stage, second turbine stage, condenser, first feedwater pump, feedwater heater, and second feedwater pump. This first and second turbine stages may both lie inside a single-turbine (viewed as a single piece of equipment) with steam being tapped from a point near the middle of the turbine.

The conditions of steam generation in the boiler are the same as in Example 8.1 8,600 kPa and 500°C. The exhaust pressure of the turbine, lOkPa, is also the same. The saturation temperature of the exhaust steam is therefore 45.83°C. Allowing for slight subcooling of the condensate, we fix the temperature of the liquid water from the condenser at 45°C. The feedwater pump, which operates under exactly the conditions of the pump in Example 7.10, causes a temperature rise of about 1°C, making the temperature of the feedwater entering the series of heaters equal to 46°C. 

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