Service Water System

S. Arrington and G. Bradley, "Service Water System Cleaning with Ammoniated Citric Acid," paper presented at Corrosion 87-NACE, No. 387, San Francisco, Calif., 1987. 

Figure 3.1 Utility service water system pipe almost plugged by heavy tuberculation.

Figure 3.14 Small, hard tubercles on an essential service water system pipe in a nuclear utility.

Equipment in which water flow is slow or intermittent is subject to deposition and associated corrosion. Hence, service water-system components that operate intermittently frequently suffer attack. Deposits accumulate in narrow orifices, screens, long horizontal pipe runs, sumps, or at regions of constricted flow. 

Carbon steel heat exchangers, cast iron water boxes, screens, pump components, service water system piping, standpipes, fire protection systems, galvanized steel, engine components, and virtually all non-stainless ferrous components are subject to significant corrosion in oxygenated water. 

A typical microbiological analysis in a troubled carbon-steel service water system is given in Table 6.2. Table 6.3 shows a similar analysis for a cupronickel utility main condenser that showed no significant corrosion associated with sulfate reducers. When biological counts of sulfate reducers in solid materials scraped from corroded surfaces are more than about 10, significant attack is possible. Counts above 10 are common only in severely attacked systems. 

TABLE 6.2 Typical Microbiological Analysis In a Service Water System Pipe Experiencing Microbiologically Influenced Corrosion ... 

Clostridia frequently are found where sulfate-reducing bacteria are present, often in high numbers inside tubercles. A typical microbiological analysis of tubercular material removed from a troubled service water system main is given in Table 6.4. Clostridia counts above 10 /g of material are high enough to cause concern. When acid producers... 

Specimen Location Emergency service water system piping to reactor core spray... 

Specimen Location Service water system, branch line... 

JO r nntainmpnr nrftccnrf, j. oblems 32. Loss of service-water system... 

Improved service water reliability by elimination of rubber expansion joints in the recirculated cooling water system and minimization of their use in the raw service water systems... 

Problems related to microorganisms, sediment and water in fuels and fuel systems can develop for a variety of reasons. TABLE 4-10 describes a typical microbiological analysis in a service water system. Sources include ... 

Accidents originating inside the plant but which affect the entire plant area are termed area accidents. In particular, these maybe fires and internal floods, typically started by breaks in the service water system. 

We have identified 1 C equipment and the cooling water supply (in particular the service water system) as the systems most susceptible to impacts of harsh weather conditions. For these systems site specific analyses should be made to assess potential safety margins. 

Component cooling water system Spent fuel pool cooling and cleanup system Residual heat removal system Essential service water system... 

SERVICE WATER SYSTEMS CSA Class 6 These systems remov c heat from equipment including saictv related equipment and transfer this heat to the ultimate heat sink The sy stems are compnsed of a recirculated cooling water system (closed loq>) and a raw service water system (once-ihrough) connected to the ultimate heat sink... 

PROPOSED REQUIREMENTS FOR IMPROVING RELIABILITY OF OPEN CYCLE SERVICE WATER SYSTEMS... 

Calvert Cliffs Unit 1 experienced a loss of both redundant trains of service water when the Station Service Water System (SSWS) became air bound as a result of the failure of a non-safety-related instrument air compressor aftercooler. The significance of this event lies in the fact that it involved two fundamental aspects in the design of safety-related systems (l) interaction between safety and non-safety-related systems and components, and (2) single failure of redundant safety systems. 

Generic Safety Issue (GSI) 051 in NUREG-0933 (Reference 1), identifies the susceptibility of the Station Service Water System (SSWS) to fouling which leads to plant shutdowns and reduced power operation for repairs. 

As described above, the System 80+ Standard Design SSWS and CCWS include many design features which minimize the problems that certain plants have experienced with open cycle service water system fouling or flow blockage due to mud, silt, ice, corrosion products or aquatic bivalves. Therefore, this issue is resolved for the System 80+ Standard Design. 

Design of the SSWS (or service water system (SWS) as identified in NUREG-0933) varies considerably among existing plants. At... 

Dynamic loads, and the provision of vents and drains where appropriate, are also addressed in the design of the Shutdown Cooling, Safety Injection, Containment Spray, Component Cooling and Service Water Systems. These systems are described in CESSAR-DC, Sections 5.4.7, 6.3.1, 6.5.1, 9.2.1, and 9.2.2 respectively. 

The component cooling water system (CCWS) provides a continuous supply of cooling water to plant components which handle potentially radioactive fluids. In doing so, it forms an intermediate barrier between these potentially radioactive systems and the service water system, thereby reducing the possibility of discharging radioactivity to the environment. Component cooling water is supplied to NSSS as required by the following operations ... 

The closed cooling water system consists of a separate, forced circulation loop. This system uses water piped from the site service water source to provide a heat sink for selected nuclear system equipment. Its purpose is to provide a second barrier between the primary systems containing radioactive products and the service water system that is the final heat... 

Two medium-voltage buses supplied from the secondary windings of the two transformers on the Class IV primary medium-voltage buses, which supply power to the pumps in the service water system, ECCS, moderator circulation system, shutdown cooling system, HTS feed lines, steam generator auxiliary feed line, and the air compressors and chillers. 

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