ML18023B254
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BFN-25 11.7-1 11.7 CONDENSATE FILTER-DEMINERALIZER SYSTEM 11.7.1 Power Generation Objective The objective of the Condensate Filter-Demineralizer System is to treat the flow of condensate from the condenser hotwell to remove dissolved and suspended solids which result from corrosion in the condenser and associated piping systems and from leakage of cooling water into the condenser.
11.7.2 Power Generation Design Basis
- 1. The system will be capable of proce ssing the full flow of condensate under normal operating conditions.
- 2. The system will be capable of handling, at less than full flow, the high concentrations of dissolved and particulate material present in the condensate during startup and restart operations.
- 3. The system will be capable of handling so me inleakage of condenser cooling water with only a minimal increase in effluent conductivity.
11.7.3 System Description The Condensate Filter-Demineralizer Syst em for each reactor unit consists of ten filter-demineralizer units, a backwash system, a precoat system, and a bodycoat system (Figures 11.7-1, 11.7-2, and 11.7-3).
Nine filter-demineralizer units are located in individual concrete cells. No valves or other equipment with moving parts are loca ted within the cells. Holding pumps, which serve to keep the precoat in place while their associated units are out of
service, are located in a pump and valve r oom adjacent to the demineralizer units.
The tenth filter-deminizeralizer unit is located in an area adjacent to the nine filter-demineralizers. It is enclosed by a radiological shield.
There are no valves or other equipment with moving parts located within the shield.
The filter-demineralizer units, arranged in parallel, are supplied by the condensate pumps via an inlet header. An outlet header collects the effluent from the individual filter demineralizer. When the unit is s hut down for refueling, one or more filter-demineralizer units may be used to polish condensate for filling the reactor well and dryer-separator pit. The fill water is normally supplied from condensate storage to the reactor via the condenser hotwell and the condensate and feedwater lines or via the Core Spray System.
At the end of the refueling per iod, filter-demineralizer units may be used to treat water drained from the reactor well and dryer-separator
pit before it is returned to condensate storage.
BFN-25 11.7-2 The filter-demineralizer system effluent water should meet the following minimum expected quality criteria during power operation:
Loading Effluent Specific conductivity .................................................. Less than 0.1 micromho/cm Total iron ................................................................................... Less than 10 ppb Total copper .................................................................................. Less t han 2 ppb The filter-demineralizer vessels are vertical cylinders with dished heads. They are 6 feet in diameter by 6 feet 6 inches straight side height or as described in the vendor manual. The tenth filter-demi neralizer vessel is a segmented vertical cynlinder with a flat head. It is 6 feet in diameter by 8 feet 8 inches high. Each vessel contains 302 filter elements which are removable for inspection or replacement. The system is designed for a total flow of 26,800 gpm (pre-uprated). The normal (extended uprated) flow rate is approximately 33,250 gpm. Flow rates are approximately equal through each filter-demineralizer unit.
The filter-demineralizer filt er elements are coated with a mi xture of cation and anion exchange resins in hydrogen and hydroxyl forms, respectively. The coating is applied to the filter elements in thicknesse s of up to about 1/4 inch. This coating serves the dual functions of filtration and ion exchange.
A filter-demineralizer unit may be remov ed from service when its pressure drop exceeds operational requirem ents or when the effluent conductivity increases above water chemistry specification. The exh austed unit is backwashed to remove the spent resin, which is flushed to a backwash receiver tank. Fresh resin slurry is prepared as required and pumped to the unit, where the resin particles are deposited on the filter element
- s. Backwash and precoating operations are normally performed automatically but may be performed manually. After precoating is completed, flow produced by the holding pump keeps the resin coating in place on the filter elements until the unit is placed in service. Backwash receiver tank contents are pumped to one of the condens ate phase separator tanks in the Radwaste Building.
A strainer which serves as a resin trap is located in the effluent line from each filter-demineralizer unit.
The resin trap is designed to stop particulates that might leak through in the event of a failure of one or more filt er support elements.
Instrumentation and controls are provi ded to perform the following functions:
- a. Measure electrical conductivity of wa ter in the influent header, effluent line of each filter-demineralizer, and effluent header. Alarms ar e provided for each of the effluent points.
BFN-25 11.7-3 b. Measure pressure drop across each filter-demineralizer, and alarm on high differential pressure.
- c. Measure pressure differential bet ween influent and effluent headers, and open the system bypass valve on system high-differential signal.
- d. Measure flow rates.
- e. Start holding pump when flow rate through any filter-demineralizer unit decreases to a preset setpoint.
- f. Alarm high-pressure drop across resin traps.
Controls and local instrumentation for the system are mounted on a panel located near the precoat system. Recorders [Unit 1 only] / Monitors [Units 2 and 3] and alarms are on this panel for Unit 2 only. Fo r Units 1 and 3, ala rms and monitors are provided on the panel. In t he Main Control Room, an alarm indicates trouble in the condensate demineralizer syst em. A hand switch whic h operates the system bypass valve is also located in the Main Control Room. Recorders and alarms for conductivity are also located in the analytical laboratory.
Decontamination of filter-demineralizer units can be performed using the precoat system to make up and circulate decontaminating solutions.
11.7.4 Power Generation Evaluation In the event of a complete power failure, the condensate pumps stop, and flow through the filter-demineralizers ceases.
The holding pumps are not supplied with emergency power, so that they are unable to maintain a minimum flow. Under no-flow conditions, the coating on the filter elements tends to fall to the bottom of the vessel. Before the filter-demineralizers are returned to service, after power is restored, they should be backwashed and precoated.
11.7.5 Inspection and Testing The filter-demineralizer syst em is used extensively durin g preoperational testing and during startup operations. This use provides thorough testing of the system.
Filter-demineralizer element s are replaced by high differential pressure across a filter demineralizer unit or due to resin leakage. Other equipment in the system receives routine maintenance.