ML19322B514

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Chapter 10 of Oconee 1,2 & 3 PSAR, Steam & Power Conversion Sys. Includes Revisions 1-6
ML19322B514
Person / Time
Site: Oconee  Duke Energy icon.png
Issue date: 12/01/1966
From:
DUKE POWER CO.
To:
References
NUDOCS 7912040282
Download: ML19322B514 (9)
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O TABLE OF CONTENTS Section g

10 STEAM AND POWER CONVERSION SYSTEM 10-1 10.1 DESIGN BASES 10-1 10.1.1 OPERATING AND PERFORNANCE REQUIREMENTS 10-1 10.1.2 ELECTRICAL SYSTEM CHARACTERISTICS 10-1 10.1.3 FUNCTIONAL LIMITATIONS 10-1 10.1.4 SECONDARY FUNCTIONS 10-1 10.2 SYSTEM DESIGN AND OPERATION 10-2 10.2.1 SCHEMATIC FLOW DIAGRAM 10-2 10.2.2 CODES AND STANDARDS 10-2 10.2.3 DESIGN FEATURES 10-3 10.2.4 SHIELDING 10'-3 a

10.2.5 CORROSION PROTECTION 10-3 10.2.6 IMPURITIES CONTROL 10-3 J

10.2.7 RADIOACTIVITY 10-3 10.3 SYSTEM ANALYSIS 10-3 l 10.3.1 TRIPS, AUTOMATIC CONTROL ACTIONS AND ALARNS 10-3 10.3.2 TRANSIENT CONDITIONS 10-4 10.3.3 MALFUNCTIONS 10-4 10.3.4 OVERPRESSURE PROTECTION 10-5 10.3.5 INTERACTIONS 10-5 10.3.6 OPERATIONAL LIMITS 10-5 10.4 TESTS AND INSPECTIONS 10-5 O .

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LIST OF FIGURES Figure No. Title l 10-1 Steam and Power Conversion System i i

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10 STEAM AND POWER CONVERSION SYSTEM 10.1 DESIGN BASES 10.1.1 OPERATING AND PERFORMANCE REQUIREMENTS The steam and power conversion system for each unit will be designed to remove heat energy from the reactor coolant in the two steam generators and convert it to electrical energy. The closed feedwater cycle will condense the steam, and the heated feedwater will be returned to the steam generators.

The entire system will be designed for the maximum expected energy from the nuclear steam supply system.

At levels above 40 per cent full load, the turbine will accept instantaneous load changes of 40 per cent of full load. Below 40 per cent full load, the turbine will accept instantaneous load changes of varying magnitudes ranging down to a change of 20 per cent of full load at la per cent full load. Upon loss of full load, the system will dissipate all the energy existent or pro-duced in the reactor coolant system through steam relief to the condenser and the atmosphere. The unit will be designed to maintain station auxiliary load without a reactor trip on loss of full load. The steam bypass to the condenser and atmospheric relief valves will be utilized as necessary to achieve this load reduction.

10.1.2 ELECTRICAL SYSTEM CHARACTERISTICS I

The station will be designed for load following operation. The maximum rate of change of load is noted in 10.1.1 and 10.1.3.

10.1.3 FUNCTIOMAL

  • IMITATIONS The rate of change of reactor power will be limited to values consistent with the characteristics of the reactor coolant system and its control systems.

These limitations in the reactor coolant system will be reflected as func-tional limitations in the steam and power conversion system. Increasing reactor power transients between 20 and 90 per cent of full load will be limited to ramp changes of 10 per cent per minute and step increases of 10 per cent. Power increases above 90 per cent will be limited to 5 per cent per minute. Decreasing reactor power transients between 100 and 20 per cent of full load will be limited to ramp changes of 10 per cent per minute and step decreases of 10 per cent.

10.1.4 SECONDARY FUNCTIONS The steam and power conversion system will provide steam for driving the two one-half capacity feedwater pumps for each unit. Steam will also be used for the condenser air removal equipment and the 5 per cent emergency feed-water pump when required.

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10.2 SYSTEM DESIGN AND OPERATION 9

10.2.1 SCHEMATIC FLOW DIAGRAM The steam und power conversion system is shown in Figure 10-1. The closed cycle feedwater heaters will be half-size units (two parallel strings).

Deaeration will be accomplished in the condenser hotwell. A bypass of 25 per cent of full load main steam flow to the condenser will be provided.

Two of the three one-half capacity hotwell pumps and two of the three one-half capacity condensate booster pumps will be in normal use. Each of two feedwater pumps will be at least one-half capacity.

There will be a total of ten minutes condensa g ,sfprage at full load in the condenser hotwells. The upper surge tank of w ,v00 gallons capacity will provide 0-6 minutes of additional condensate storage at full load.

50 There will also be a 5 per cent capacity, turbine driven, emergency feedwater pump which takes its suction directly from the hotwell discharge and pumps to the steam generators. Steam for the turbine drive will come from the main steam line and exhaust to the condenser.

The main steam lines and the feedwater lines will be the only lines of the steam and power conversion system which penetrate the Reactor Building.

These lines can be isolated by the main stop valves and the feedwater line valving. Each of the lines leaving the main steam line before the main stop valves has valves to complete the isolation of a steam generator. These lines are:

(a) Steam bypass.

(b) Supply to feed pump turbines.

(c) Supply to steam reheaters.

(d) Supply to condenser air ejectors.

(e) Supply to emergency feed pump turbine.

The arrangement of the valving and parallel piping shown schematically in Figure 10-1 prevents blowdown of both steam generators from a single leak in the system.

10.2.2 CODES AND STANDARDS The turbine-generator equipment will conform to the applicable ASA, ASME and IEEE standards.

The design, materials and details of construction of the feedwater heaters will be in accordance with both the ASME Code,Section VIII, Unfired Pres--

sure vessels and the Standards of Feedwater Heater Manufacturers Association, '

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e The condenser equipment will be in accordance with the Standards for Steam Surface condensers as published by the Heat ExcLenge Institute.

The tanks associated with the steam and power conversion system will be in accordance with the ASME Code,Section VIII.

10.2.3 DESIGN FEATURES The condenser air ejector off-gas will be continuously monitored with an alarm to indicate high radiation levels. The air ejector off-gas will be released through the station vent.

10.2.4 , SHIELDING No radiation shielding will be required for the components of the steam and power conversion system. Continuous access to the components of this system will be possible during normal conditions.

10.2.5 CORROSION PROTECTION Hydrazine will be added to the feedwater for oxygen control, and ammonia will be used to maintain the pH at the optimum value for the materials of construc-tion for the system. No other additives are contemplated.

10.2.6 IMPURITIES CONTROL

, Impurities in the steam and power conversion system will be controlled by a polishing demineralizer sized for at least one-half flow. The makeup water to the steam and power conversion system will be treated by a separate demineralizer.

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10.2.7 RADI0 ACTIVITY l Under normal operating conditions, there will be no radioactive contaminants present in the steam and power conversion system. It is possible for this system to become contaminated only through steam generator tube leaks. In this event, monitoring of the steam generator shell side sample points and the air ejector off-gas will detect any contamination.

10.3 SYSTEM ANALYSIS 10.3.1 TRIPS, AUTOMATIC CONTROL ACTIONS AND A1 ARMS i Trips, automatic control actions and alarms will be initiated by deviations' l of system variables within the steam and power conversion system. In the l case of automatic corrective action in the steam and power conversion system, appropriate corrective action will be taken to protect the reactor coolant system. The more significant malfunctions or faults which cause trips, auto-matic actions or alarms in the steam and power conversion system are:

(a) Turbine Trips

1. Generator / electrical faults.

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2. Loss of condenser vacuum.

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3. Thrust bearing wear.
4. Loss of generator stator coolant.
5. Loss of both feedwater pumps.
6. Turbine overspeed.
7. Reactor trip.

(b) Automatic Control Actions

1. Feedwater flow lagging feedwater demand results in a reduction in power demand.
2. Low feedwater temperature results in a reduction in power demand.
3. High level in steam generator results in a reduction in feedwater flow. '
4. Low level in steam generator results in an increase in feedwater flew.

(c) Principal Alarms

1. Low pressure at feedwater pump suction.
2. Low vacuum in condenser.
3. Low water level in condenser hotwell.
4. High water level in condenser hotwell.
5. High water level in steam generator.
6. Lov water level in steam generator.
7. High pressure in steam generator.
8. Low pressure in steam generator.
9. Low feedwater temperature.

10.3.2 TRANSIENT CONDITIONS The analysis of the effects of loss of full load on the reactor coolant system is discussed in 14.1.2.8. Analysis of the effects of partial loss of load on the reactor coolant system is discussed in 7.2.3.4.

10.3.3 MALFUNCTIONS The effects of inadvertent steam relief or steam bypass are covered by the -

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O, analysis of the steam line failure given in 14.1.2.9. The effects of an inadvertent rapid throttle valve closure are covered by the loss of full load discussion in 14.1.2.8.

10.3.4 OVERPRESSURE PROTECTION Pressure relief is required at the system design pressure of 1050 psig, and the first safety valve bank will be set to relieve at this pressure. The design pressure is based on the operating pressure of 925 psia plus a 10 per cent allowance for transients and a 4 per cent allowance for blowdown. Addi-tional safety valve banks will be set at pressures up to 1104 psig, as allowed by the ASME Code.

The pressure relief capacity will be such that the energy generated at the ,

reactor high power level trip setting can be dissipated through this system. '

10.3.5 INTERACTIONS J Following a turbine trip, the control system will reduce reactor power outt ut immediately. The safety valves will relieve excess steam until the output is reduced to the point at which the steam bypass to the condenser can handle all the steam generated.

In the event of failure of a single feedwater pump, there will be an automa-tic runback of the power demand. The one feedwater pump remaining in service J will carry approximately 60 per cent of full load feedwater flow. If both

" feedwater pumps fail, the turbine will be tripped, and the emergency feed-water pump started. If reactor coolant system conditions reach trip limits, the reactor will trip.

On failure of a hotwell pump or a condensate booster pu.np, the spare hotwell ,

pump or the spare condensate booster pump will be automatically started. I 10.3.6 OPERATIONAL LIMITS The air ejector off-gas will be monitored for radioactivity, and safe operating limits will be established for the station. i 10.4 TESTS AND INSPECTIONS j i

As is essential in successful operation of any modern power station, frequent functional operational checks will be made on vital valves, control systems and protective equipment.

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