Firewater reliability

Firewater Reliability - A mathematical model of the ability of the firewater system to provide firewater upon demand as required by the design of the system without a component failure, e.g., a Mean Time Between Failure (MTBF) analysis. 

Some licensees have a switch to bypass RCIC high steam tunnel temperature trips. Some licensees are evaluating improvements to prevent seal LOCAs from loss of seal cooling which are most important for W plants, but B W licensees identified improvements related to alternate seal flow capability under loss of power conditions. The use of high temperature seals is noted for some W plants. Many PWR IPEs identify AFWS improvements. These include additional backup water supplies such as the firewater system and redundant pump cooling capability. Other reliability... 

Similarly, if a vessel is provided with a reliable and dependable water cooling system, i.e., firewater deluge spray, according to recognized... 

Small capacity pumps, commonly referred to as jockey pumps, are provided on a firewater system to compensate for small leakages and incidental usage without the main pump(s) startup. They are set to start at 0.70-1.05kg/sq.cm. (10-15psi) above the startup pressure of main firewater pumps. In some cases, a cross-over from the utility water system can be used in place of a jockey pump, but a check valve is installed to prevent drain down of the firewater system by the utiHty water system. Jockey pumps do not require the same reliability of firewater pumps and should not be credited for firewater supply when calculating firewater supplies available. 

In an emergency when water is required to extinguish a fire, having a reliable firewater system that can handle stagnant water is of vital importance. Figures 7.1 la and b show two examples of MIC within such systems. 

Virtually all facilities need pumps to ensure that the firewater is supplied at sufficient pressure. These pumps must be highly reliable and spared where possible. The pumps should also be in different locations, as illustrated in Figure 9.1, so... 

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