ML20197A404
| ML20197A404 | |
| Person / Time | |
|---|---|
| Site: | NuScale |
| Issue date: | 06/19/2020 |
| From: | Bergman T NuScale |
| To: | Office of Nuclear Reactor Regulation |
| Cranston G | |
| References | |
| NUSCALESMRDC, NUSCALESMRDC.SUBMISSION.12, NUSCALEPART02.NP, NUSCALEPART02.NP.5 | |
| Download: ML20197A404 (152) | |
Text
NuScale Standard Plant Design Certification Application Chapter Ten Steam and Power Conversion System PART 2 - TIER 2 Revision 4.1 June 2020
©2020, NuScale Power LLC. All Rights Reserved
COPYRIGHT NOTICE This document bears a NuScale Power, LLC, copyright notice. No right to disclose, use, or copy any of the information in this document, other than by the U.S. Nuclear Regulatory Commission (NRC), is authorized without the express, written permission of NuScale Power, LLC.
The NRC is permitted to make the number of copies of the information contained in these reports needed for its internal use in connection with generic and plant-specific reviews and approvals, as well as the issuance, denial, amendment, transfer, renewal, modification, suspension, revocation, or violation of a license, permit, order, or regulation subject to the requirements of 10 CFR 2.390 regarding restrictions on public disclosure to the extent such information has been identified as proprietary by NuScale Power, LLC, copyright protection notwithstanding. Regarding nonproprietary versions of these reports, the NRC is permitted to make the number of additional copies necessary to provide copies for public viewing in appropriate docket files in public document rooms in Washington, DC, and elsewhere as may be required by NRC regulations. Copies made by the NRC must include this copyright notice in all instances and the proprietary notice if the original was identified as proprietary.
TABLE OF CONTENTS NuScale Final Safety Analysis Report Table of Contents Tier 2 i
Revision 4.1 CHAPTER 10 STEAM AND POWER CONVERSION SYSTEM........................ 10.1-1 10.1 Summary Description...................................................... 10.1-1 10.1.1 General Description........................................................ 10.1-1 10.1.2 Protective Features........................................................ 10.1-2 10.2 Turbine Generator......................................................... 10.2-1 10.2.1 Design Bases.............................................................. 10.2-1 10.2.2 System Description........................................................ 10.2-1 10.2.3 Not Used.................................................................. 10.2-7 10.2.4 Safety Evaluation.......................................................... 10.2-8 10.2.5 References................................................................ 10.2-8 10.3 Main Steam System........................................................ 10.3-1 10.3.1 Design Bases.............................................................. 10.3-1 10.3.2 System Description........................................................ 10.3-2 10.3.3 Safety Evaluation.......................................................... 10.3-7 10.3.4 Inspections and Tests...................................................... 10.3-8 10.3.5 Water Chemistry........................................................... 10.3-9 10.3.6 Steam and Feedwater System Materials................................... 10.3-11 10.3.7 Instrumentation.......................................................... 10.3-13 10.3.8 References............................................................... 10.3-13 10.4 Other Features of Steam and Power Conversion System...................... 10.4-1 10.4.1 Main Condenser........................................................... 10.4-1 10.4.2 Condenser Air Removal System............................................ 10.4-6 10.4.3 Turbine Gland Sealing System............................................. 10.4-11 10.4.4 Turbine Bypass System.................................................... 10.4-14 10.4.5 Circulating Water System................................................. 10.4-17 10.4.6 Condensate Polishing System............................................. 10.4-23 10.4.7 Condensate and Feedwater System....................................... 10.4-28 10.4.8 Steam Generator Blowdown System....................................... 10.4-40 10.4.9 Auxiliary Feedwater System............................................... 10.4-40 10.4.10 Auxiliary Boiler System.................................................... 10.4-40 10.4.11 Feedwater Treatment System............................................. 10.4-47 10.4.12 References............................................................... 10.4-51
LIST OF TABLES NuScale Final Safety Analysis Report List of Tables Tier 2 ii Revision 4.1 Table 10.1-1:
Major Steam and Power Conversion System Parameters....................... 10.1-4 Table 10.2-1:
Turbine Generator Design Parameters........................................ 10.2-9 Table 10.2-2:
Not Used................................................................... 10.2-10 Table 10.2-3:
Turbine Generator System Instrument List................................... 10.2-11 Table 10.2-4:
Turbine Generator Control List.............................................. 10.2-12 Table 10.3-1:
Main Steam System Design Data (Single NuScale Power Module)............. 10.3-14 Table 10.3-2:
Main Steam System Failure Modes and Effects Analysis (Isolation Functions).................................................................. 10.3-15 Table 10.3-3a:
SG Sample (Wet Layup) (Reactor Coolant System 200°F).................... 10.3-18 Table 10.3-3b:
Feedwater Sample (Reactor Coolant System > 200°F to <15% reactor power)...................................................................... 10.3-19 Table 10.3-3c:
Feedwater Sample (15% reactor power).................................... 10.3-20 Table 10.3-3d:
Condensate Sample ( 15% reactor power).................................. 10.3-21 Table 10.3-3e:
Steam Generator Fill Water (initial fill subsequent to a shutdown)............. 10.3-22 Table 10.3-4:
Main Steam System Instrumentation........................................ 10.3-23 Table 10.3-5:
Power Conversion System Flow-Accelerated Corrosion Program Piping....... 10.3-25 Table 10.4-1:
Main Condenser Design Data................................................ 10.4-52 Table 10.4-2:
Main Condenser System Instrumentation.................................... 10.4-53 Table 10.4-3:
Condenser Air Removal System Design Data (Nominal)....................... 10.4-54 Table 10.4-4:
Condenser Air Removal System Instrumentation............................. 10.4-55 Table 10.4-5:
Gland Seal Steam Skid Design Data.......................................... 10.4-56 Table 10.4-6:
Gland Sealing System Instrumentation....................................... 10.4-57 Table 10.4-7:
Turbine Bypass System Component Details.................................. 10.4-58 Table 10.4-8:
Turbine Bypass System Instrumentation..................................... 10.4-59 Table 10.4-9:
Circulating Water System Design Parameters................................ 10.4-60 Table 10.4-10:
Circulating Water System Interfaces......................................... 10.4-61 Table 10.4-11:
Circulating Water System Instrumentation................................... 10.4-62 Table 10.4-12:
Circulating Water System Alarms............................................ 10.4-63 Table 10.4-13:
Condensate Polishing System Operating Parameters......................... 10.4-64 Table 10.4-14:
Condensate Polishing System Impurity Limits................................ 10.4-65 Table 10.4-15:
Condensate Polishing System Instrumentation............................... 10.4-66 Table 10.4-16:
Condensate Polishing System Alarms........................................ 10.4-67 Table 10.4-17:
Condensate and Feedwater System Component Design Data................ 10.4-68
LIST OF TABLES NuScale Final Safety Analysis Report List of Tables Tier 2 iii Revision 4.1 Table 10.4-18:
Condensate and Feedwater System Failure Modes and Effects Analysis....... 10.4-69 Table 10.4-19:
Condensate and Feedwater System Instrumentation......................... 10.4-88 Table 10.4-20:
Auxiliary Boiler System Component Design Parameters...................... 10.4-90 Table 10.4-21:
Auxiliary Boiler System Instrumentation..................................... 10.4-91 Table 10.4-22:
Not Used................................................................... 10.4-92 Table 10.4-23:
Feedwater Treatment System Component Design Data...................... 10.4-93 Table 10.4-24:
Feedwater Treatment System Instrumentation............................... 10.4-94
LIST OF FIGURES NuScale Final Safety Analysis Report List of Figures Tier 2 iv Revision 4.1 Figure 10.1-1:
Power Conversion System Block Flow Diagram................................ 10.1-5 Figure 10.1-2:
Flow Diagram and Heat Balance Diagram at Rated Power for Steam and Power Conversion System Cycle.......................................... 10.1-6 Figure 10.1-3:
Flow Diagram and Heat Balance Diagram at Stretch Power (valves wide open) for Steam and Power Conversion System Cycle.................... 10.1-7 Figure 10.2-1:
Turbine Generator System Piping and Instrumentation Diagram.............. 10.2-13 Figure 10.2-2:
Not Used................................................................... 10.2-14 Figure 10.3-1:
Main Steam System Piping and Instrumentation Diagram.................... 10.3-26 Figure 10.4-1:
Main Condenser Piping and Instrumentation Diagram....................... 10.4-95 Figure 10.4-2:
Condenser Air Removal System Piping and Instrumentation Diagram......... 10.4-96 Figure 10.4-3:
Circulating Water System Piping and Instrumentation Diagram (Typical of 2)........................................................................ 10.4-97 Figure 10.4-4a:
Auxiliary Boiler System Piping and Instrumentation Diagram................. 10.4-98 Figure 10.4-4b: Auxiliary Boiler System Piping and Instrumentation Diagram................. 10.4-99
NuScale Final Safety Analysis Report Summary Description Tier 2 10.1-1 Revision 4.1 CHAPTER 10 STEAM AND POWER CONVERSION SYSTEM 10.1 Summary Description The steam and power conversion system removes and directs heat energy from the reactor coolant system. The heat energy from the NuScale Power Module is transferred from the primary coolant by two helical-coil steam generators to convert the secondary coolant to steam. This steam energy is then converted to electrical power in the turbine generator. Each NuScale Power Module has its own steam and power conversion system. The steam and power conversion system has no safety-related function.
The steam and power conversion system includes the pipe, fittings, valves, and instruments from (and including) the removable pipe spools at the containment system main steam isolation valves (MSIVs), to (and including) the removable pipe spools at the containment system feedwater isolation valves. The steam and power conversion system is comprised of the following components and process systems:
turbine generator system (TGS) (Section 10.2) main steam system (MSS) (Section 10.3) main condenser (MC) (Section 10.4.1) condenser air removal system (CARS) (Section 10.4.2) turbine gland sealing system (Section 10.4.3) turbine bypass system (Section 10.4.4) circulating water system (CWS) (Section 10.4.5) condensate polishing system (CPS) (Section 10.4.6) condensate and feedwater system (CFWS) (Section 10.4.7) auxiliary boiler system (ABS) (Section 10.4.10) feedwater treatment system (FWT) (Section 10.4.11)
Table 10.1-1 provides the major system operating parameters at rated thermal power.
Table 10.2-1 provides turbine generator design parameters.
Figure 10.1-1 provides a power conversion system block flow diagram of a NuScale Power Module. Figure 10.1-2 provides a heat balance diagram at rated thermal power. Figure 10.1-3 provides a heat balance diagram at stretch power (valves wide open).
10.1.1 General Description During normal operation, steam generated in the two helical-coil steam generators is supplied by the MSS to the turbine through the turbine stop and control valves which regulate steam flow.
The turbine is a single-inlet design 10-stage condensing steam turbine with three uncontrolled extractions, one stop valve, and a steam chest with multiple inlet control
NuScale Final Safety Analysis Report Summary Description Tier 2 10.1-2 Revision 4.1 valves. The generator is a three-phase water to air cooled generator, directly coupled to the turbine with an operating speed provided in Table 10.2-1.
After expanding across the high-pressure and low-pressure turbine blading, the condenser receives the exhaust steam from the turbine.
The MC transfers the heat rejected in the cycle to the circulating water system. The MC operates at a vacuum maintained by the CARS. Extraction steam from the turbine is routed to three feedwater heaters (FWHs) where it is condensed. The FWHs are arranged to cascade the drains from the higher-pressure heaters to the lower-pressure heaters, returning the condensate through the lower-pressure FWH to the MC.
The condensate pumps take suction from the MC hotwell. From the condensate pumps, the feedwater is sent through the condensate polishers, gland steam condenser, the low-pressure and intermediate-pressure FWHs, and to the feedwater pumps. From the feedwater pumps, the feedwater passes through the high-pressure FWH and returns through the main feedwater lines to the steam generator.
Water quality in the steam-water cycle is maintained by the feedwater treatment subsystem in conjunction with the condensate polishing system. The condensate storage tank supplies makeup water for the steam cycle. The process sampling system monitors feedwater chemistry during normal operations.
The unique steam generator design minimizes water hammer as discussed in Section 5.4.1.
10.1.2 Protective Features 10.1.2.1 Loss of External Electrical Load or Turbine Trip In the event of a loss of external electrical load or turbine trip, steam is automatically dumped to the MC through the turbine bypass valve. Load rejection capabilities of the steam and power conversion system are further described in Section 10.3 and Section 10.4.4. See Section 15.2 for the associated safety analysis.
10.1.2.2 Overpressure Protection Overpressure protection of the steam and power conversion system is provided by main steam safety valves located on the MSS header downstream of the secondary main steam isolation valves, in accordance with the ASME B31.1. The valves are described in Section 10.3.2. Piping and components upstream of the secondary main steam isolation valves are provided with overpressure protection features as described in Section 5.2.2.
10.1.2.3 Loss of Main Feedwater Flow The decay heat removal system is automatically initiated by the engineered safety features actuation system for postulated transients in which a loss of normal cooling has occurred, including loss of main feedwater. For plant accidents and transients that result in a loss of feedwater to both of the steam generators, the decay heat removal
NuScale Final Safety Analysis Report Summary Description Tier 2 10.1-3 Revision 4.1 system cools the reactor coolant system. This event is further addressed in Section 10.4.7 and Section 15.2.7.
10.1.2.4 Turbine Overspeed Protection The turbine overspeed protection system provides protection from exceeding overspeed limits. The turbine stop and control valves, and the extraction steam block and non-return valves close upon actuation of the emergency trip system within a time period to preclude unsafe turbine overspeed. Additionally, the valve arrangements and valve closure times are such that a failure of a single valve to close will not result in unsafe turbine overspeed in the event of a trip signal. Turbine overspeed protection is further discussed in Section 10.2.2.
10.1.2.5 Turbine Missile Protection Turbine missiles are discussed in Section 3.5.
10.1.2.6 Radioactivity Protection Under normal operating conditions, radioactive contaminants are not expected to be present in the steam and power conversion system. However, it is possible for the system to become contaminated through primary-to-secondary side steam generator tube leakage or in the unlikely event of a steam generator tube failure. Radiation monitors in the MSS and the CARS alarm in the control room for operator action on a high radiation signal. Primary-to-secondary side leakage is specified in the Technical Specifications.
10.1.2.7 Flow-Accelerated Corrosion Protection The MSS and feedwater system piping is designed considering the effects of flow-accelerated corrosion and erosion/corrosion. Erosion/corrosion resistant chromium-molybdenum material has been selected for piping downstream of the MSIVs. The feedwater system piping is also designed with chromium-molybdenum to avoid erosion damage.
The process sampling system provides chemistry monitoring of the MSS and CFWS for corrosion products and other contaminants as discussed in Section 10.3.
NuScale Final Safety Analysis Report Summary Description Tier 2 10.1-4 Revision 4.1 Table 10.1-1: Major Steam and Power Conversion System Parameters Description Design Parameter Nominal Value Main Steam System Steam flow (full power) 532,300 lbm/hr Normal steam pressure 500 psia Normal steam temperature 584°F Design pressure upstream / downstream of the secondary MSIVs 2100 psia / 1000 psia Design temperature 650°F Normal feedwater temperature 300°F
NuScale Final Safety Analysis Report Summary Description Tier 2 10.1-5 Revision 4.1 Figure 10.1-1: Power Conversion System Block Flow Diagram 0DLQ6WHDP
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NuScale Final Safety Analysis Report Summary Description Tier 2 10.1-6 Revision 4.1 For reference only - actual values are site dependent.
Figure 10.1-2: Flow Diagram and Heat Balance Diagram at Rated Power for Steam and Power Conversion System Cycle Steam Turbine Gland Steam Condenser Ambient pressure 14.7 psia Ambient temperature 80 F Ambient relative humidity 61.18 %
Ambient wet bulb temperature 70 F Steam Turbine Gross power 50462 kW Steam Generator Total heat transfer to water side 150734 BTU/s 371.5 p 541 T 530.7 m 1274.9 h 74.34 p 307 T 504.1 m 1149.5 h 36 p 260.9 T 463.9 m 1101.9 h 9 p 188.3 T 456.1 m 1032.6 h 9 p 188.3 T 424.3 m 1032.6 h 27.99 p 100.1 T 18357 m 68.19 h 32.99 p 80.01 T 18357 m 48.13 h 27.71 p 100.1 T 18357 m 68.19 h 14.7 p 79.98 T 18357 m 48.06 h 3.122 p 107 T 532.3 m 75.03 h 14.1 p 295.2 T 1.331 m 1190.5 h 14.1 p 295.2 T 0.25 m 1190.5 h 8.42 p 185.2 T 31.83 m 1032.6 h 35.22 p 259.7 T 40.19 m 1100.9 h 72.21 p 305 T 26.61 m 1148.5 h 72.21 p 265.2 T 26.61 m 234.1 h 492.8 p 584.4 T 532.3 m 1290 h 3.87 p 151.6 T 1.331 m 178.1 h 3.87 p 151.6 T 21.71 m 275.6 h 3.87 p 151.6 T 414.8 m 1004.5 h 3.87 p 151.6 T 403.9 m 1024.7 h 3.87 p 151.6 T 10.91 m 258.2 h 19.6 p 226.9 T 463.9 m 1065.2 h 19.6 p 226.9 T 456.1 m 1076.7 h 19.6 p 190.2 T 66.8 m 158.3 h 19.6 p 226.9 T 7.812 m 394.2 h 19.6 p 214.8 T 74.61 m 183 h 7.5 p 179.9 T 424.3 m 1022.9 h 7.5 p 179.9 T 414.8 m 1039.2 h 7.5 p 179.9 T 9.468 m 309.1 h 536.9 p 300 T 532.3 m 270.6 h 1.17 p 107 T 128.2 m 120 h 1.17 p 107 T 128.2 m 120 h 366.4 p 107.8 T 532.3 m 76.7 h 358.4 p 110.3 T 532.3 m 79.23 h 351.4 p 110.3 T 532.3 m 79.23 h 339.4 p 180.2 T 532.3 m 149 h 336.4 p 180.2 T 532.3 m 149 h 325.4 p 254.7 T 532.3 m 223.9 h 323.4 p 254.7 T 532.3 m 223.9 h 1.17 p 107 T 404.3 m 971.7 h 444.6 p 107.6 T 532.3 m 76.7 h 437.6 p 107.6 T 532.3 m 76.7 h 549.6 p 255.2 T 532.3 m 224.9 h 545.9 p 255.2 T 532.3 m 224.9 h 373.6 p 107.7 T 532.3 m 76.7 h 14.1 p 295.2 T 1.081 m 1190.5 h 8.418 p 120.3 T 106.5 m 88.33 h 459.4 p 578.7 T 532.3 m 1289.5 h 510.4 p 300.1 T 532.3 m 270.6 h G1 50462 kW 41 41 12 12 55 55 53 53 51 51 3
4 5
6 7
8 9
10 11 12 13 14 15 16 17 Circulati...
18 Cooling Tower 19 20 Condensat...
21 22 23 ASY Packing exh 24 ASY Excess steam 25 Low Pressure Feedwater Heater 26 27 Intermediate Pressure Feedwater Heater 29 30 31 High Pressure Feedwater Heater 32 34 35 2
41 42 44 45 43 46 47 48 49 28 1
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NuScale Final Safety Analysis Report Summary Description Tier 2 10.1-7 Revision 4.1 For reference only - actual values are site dependent Figure 10.1-3: Flow Diagram and Heat Balance Diagram at Stretch Power (valves wide open) for Steam and Power Conversion System Cycle Steam Turbine Gland Steam Condenser Ambient pressure 14.7 psia Ambient temperature 80 F Ambient relative humidity 61.18 %
Ambient wet bulb temperature 70 F Steam Turbine Gross power 51478 kW Steam Generator Total heat transfer to water side 153568 BTU/s 378.9 p 542.2 T 541.3 m 1274.8 h 75.8 p 308.3 T 514 m 1149.4 h 36.7 p 262.1 T 472.9 m 1101.8 h 9.172 p 189.2 T 464.9 m 1032.5 h 9.172 p 189.2 T 432.3 m 1032.5 h 26.97 p 100.6 T 18357 m 68.65 h 35.75 p 80.09 T 18357 m 48.22 h 26.7 p 100.6 T 18357 m 68.65 h 14.7 p 80.07 T 18357 m 48.15 h 3.142 p 107.6 T 542.9 m 75.62 h 14.56 p 295.4 T 1.356 m 1190.5 h 14.56 p 295.4 T 0.25 m 1190.5 h 8.576 p 186 T 32.57 m 1032.5 h 35.9 p 260.8 T 41.16 m 1100.8 h 73.6 p 306.3 T 27.3 m 1148.4 h 73.6 p 266.3 T 27.3 m 235.3 h 494.2 p 584.5 T 542.9 m 1290 h 3.944 p 152.4 T 1.356 m 179.7 h 3.944 p 152.4 T 22.14 m 274.4 h 3.944 p 152.4 T 422.7 m 1004.5 h 3.944 p 152.4 T 411.5 m 1024.7 h 3.944 p 152.4 T 11.13 m 257.2 h 19.98 p 227.9 T 472.9 m 1065.1 h 19.98 p 227.9 T 464.9 m 1076.6 h 19.98 p 191.2 T 68.46 m 159.2 h 19.98 p 227.9 T 7.968 m 391.4 h 19.98 p 215.2 T 76.43 m 183.4 h 7.643 p 180.8 T 432.3 m 1022.8 h 7.643 p 180.8 T 422.7 m 1039.1 h 7.643 p 180.8 T 9.657 m 307.4 h 539.4 p 301.1 T 542.9 m 271.7 h 1.19 p 107.6 T 131.1 m 120.4 h 1.19 p 107.6 T 131.1 m 120.4 h 361.1 p 108.3 T 542.9 m 77.27 h 354.6 p 110.9 T 542.9 m 79.79 h 347.3 p 110.9 T 542.9 m 79.79 h 340.2 p 180.9 T 542.9 m 149.7 h 337 p 180.9 T 542.9 m 149.7 h 329.5 p 255.6 T 542.9 m 224.9 h 327.5 p 255.6 T 542.9 m 224.9 h 1.19 p 107.6 T 411.9 m 971.7 h 439.5 p 108.1 T 542.9 m 77.27 h 432.5 p 108.2 T 542.9 m 77.27 h 552.3 p 256.1 T 542.9 m 225.8 h 548.5 p 256.1 T 542.9 m 225.8 h 368.5 p 108.3 T 542.9 m 77.27 h 14.56 p 295.4 T 1.106 m 1190.5 h 8.576 p 121.1 T 109 m 89.11 h 459.5 p 578.6 T 542.9 m 1289.5 h 511.8 p 301.2 T 542.9 m 271.7 h G1 51478 kW 41 41 12 12 55 55 53 53 51 51 3
4 5
6 7
8 9
10 11 12 13 14 15 16 17 Circulati...
18 Cooling Tower 19 20 Condensat...
21 22 23 ASY Packing exh 24 ASY Excess steam 25 Low Pressure Feedwater Heater 26 27 Intermediate Pressure Feedwater Heater 29 30 31 High Pressure Feedwater Heater 32 34 35 2
41 42 44 45 43 46 47 48 49 28 1
50
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-1 Revision 4.1 10.2 Turbine Generator The primary function of the turbine generator system is to convert steam into electricity. Each turbine generator system services one NuScale Power Module (NPM). There are up to two turbine generator buildings, each with up to six separate turbine generator systems.
10.2.1 Design Bases This section identifies the turbine generator system (TGS) required or credited functions, the regulatory requirements that govern the performance of those functions, and the controlling parameters and associated values that ensure that the functions are fulfilled.
Together, this information represents the design bases (as defined in 10 CFR 50.2) for the TGS.
The TGS serves no safety-related functions, is not credited for mitigation of a design basis accident, and has no safe shutdown functions. General Design Criteria (GDC) 2, 4, and 5 were considered in the design of the TGS. No safety-related structures, systems, and components (SSC) are affected by natural phenomena such as earthquakes. Protection of essential SSC from turbine generator missiles is addressed in Section 3.5. The components in the TGS are not shared among NPMs; therefore failure of the TGS of one NPM does not impair the ability of other NPMs to perform their safety functions. Consistent with 10 CFR 20.1101(b), the TGS design supports keeping radiation exposures as low as reasonably achievable (ALARA). The TGS is designed consistent with the requirements of 10 CFR 20.1406 as it relates to minimization of contamination of the facility. See Section 10.2.4 for the safety evaluation.
The TGS control system is designed to automatically trip the turbine on the abnormal conditions listed in Section 10.2.2.4.
As discussed in Section 10.2.2.3.3, turbine overspeed protection ensures that a full-load turbine trip does not cause the turbine to overspeed beyond the acceptable limits. The single failure of a component or subsystem does not cause an unsafe turbine overspeed.
The TGS design parameters are listed in Table 10.2-1.
10.2.2
System Description
10.2.2.1 General Description The TGS for each NPM has three supporting subsystems: the turbine, the generator, and the turbine lube oil system. Figure 10.2-1 shows the TGS simplified piping and instrumentation diagram. The TGS and associated piping, valves, and controls are located completely within the turbine generator building. There are no safety-related systems or components located within the turbine generator building.
The TGS is Seismic Category III and TGS piping is designed to ASME B31.1. Components, piping, and structures are designed in accordance with applicable codes and standards as discussed in Section 3.9. Table 3.2-1 provides the seismic and quality group classifications for the TGS structures, systems, and components. High-energy and moderate-energy pipe breaks are addressed in Section 3.6.1. Protection against turbine missiles is discussed in Section 3.5.
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-2 Revision 4.1 The following areas address aspects of the TGS design:
Regulatory treatment of nonsafety systems equipment (Section 19.3)
Quality assurance (Chapter 17)
Fire protection (Section 9.5.1)
To maintain the radiation exposure to operating and maintenance personnel ALARA, the TGS is designed to facilitate maintenance, inspection, and testing in accordance with the guidance in Regulatory Guide 8.8.
There are no relevant generic letters or unresolved safety issues for this system.
Operating experience insights are incorporated into this system as noted. The system has no relevant TMI requirements.
10.2.2.1.1 Turbine Subsystem Description One turbine is utilized for each NPM. Superheated steam is provided to the turbine from the steam generator by the main steam system. The steam passes through the stages of the turbine converting the thermal energy to mechanical energy. The turbine subsystem performs the following functions:
converts thermal energy into rotational energy controls steam flow to match control system demand provides extraction steam for the feedwater heaters transports steam to the condenser supports major pipe connection reactions for main steam (Section 10.3),
extraction steam, and exhaust steam piping systems The components of the turbine subsystem include the turbine stop valve control valves turbine bypass valve and desuperheater steam piping between turbine valves and casing outlet connections for extraction steam drain and vent connections turbine shaft journal and thrust bearings and housings turning gear gland seal steam control skid turbine rotor grounding device turbine to generator shaft coupling
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-3 Revision 4.1 The boundary between the main steam system and TGS is the upstream side of the turbine generator vendor package interface, the upstream side of the gland steam condenser connection point, and downstream of the extraction line connection points. See Figure 10.2-1 and Section 10.3 for additional information.
The turbine generators employed in the NuScale design utilize an off the shelf condensing steam turbine with uncontrolled extractions. The turbine is a single inlet design with one stop valve and a steam chest with multiple inlet control valves.
The turbine shaft journal bearings are lubricated by the lube oil subsystem. The turbine is also restrained via a thrust bearing to absorb the axial thrust of the turbine.
The turbine generator design includes a spray system which provides cooling to the turbine exhaust hood upon sensing a high temperature condition.
The gland seal steam control skid (Section 10.4.3) is also a part of the turbine subsystem. The gland seal steam control skid performs the following functions:
prevents air leakage into the turbine under vacuum and prevents steam leakage out of the turbine under pressure for anticipated load conditions provides for the use of redundant steam supplies and controlling devices Areas of the turbine requiring attention during operation are accessible during expected plant operating conditions.
10.2.2.1.2 Generator Subsystem Description The generator takes the rotational mechanical energy from the turbine and converts it into electricity by spinning the generator rotor through a magnetic field.
The magnetic field is produced by self-excitation of the stator coils. The frequency is synchronized with the offsite transmission system and power is transferred to the grid. The generator is directly coupled to the turbine, and is air cooled. Cooling water for the generator air cooling is provided by the site cooling water system.
Components of the generator subsystem include the generator stator generator air coolers generator rotor brushless or static exciter shaft grounding devices high voltage bushings bushing current transformer assembly grounding system
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-4 Revision 4.1 10.2.2.1.3 Lube Oil Subsystem Description The turbine and generator each rotate with the support of journal bearings to maintain proper radial alignment of shaft components, as well as a thrust bearing to maintain axial alignment. The lube oil system provides lubrication and cooling to these bearings during normal operation. The lube oil system performs the following functions:
supplies normal and emergency lubrication needs of turbine, generator, and exciter maintains oil purity within operating limits maintains oil temperature within operating limits for normal operation and on turning gear Components of the lube oil subsystem include the lube oil tank alternating current (AC) motor driven primary oil pump AC motor driven back-up auxiliary oil pump direct current (DC) motor driven emergency oil pump shaft lift oil system lube oil coolers vapor extractor oil mist eliminator bearing oil header pressure regulator full flow filtration assemblies lube oil conditioner and purification system The lube oil subsystem is skid mounted and provides oil via the main or auxiliary lube oil pump. An emergency lube oil pump is also provided to protect the bearings from damage following a loss of the main pumps. Once the oil is returned to the reservoir, the oil is cooled, filtered, and conditioned to remove air and moisture. The lube oil subsystem heat exchangers are cooled by the site cooling water system.
10.2.2.2 Component Description Table 10.2-1 contains the TGS component design parameter details.
10.2.2.2.1 Turbine Stop Valve The steam flow to the turbine is controlled by a single stop valve, located adjacent to the turbine. The valve is used to control the flow entering the turbine during startup and shutdown.
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-5 Revision 4.1 The stop valve is hydraulically operated and isolates steam flow to the turbine upon receiving a trip signal. The stop valve also includes a throttling pilot to support startup and shutdown operations. If a loss of oil pressure occurs, an independent hydraulic trip relay closes the turbine stop and control valves.
Hydraulic fluid is supplied to the stop valve by a control oil skid.
10.2.2.2.2 Turbine Control Valves Multiple inlet control valves are used to throttle steam flow to the turbine during normal operation. These valves close upon actuation of the emergency trip signal within a time period to preclude unsafe turbine overspeed. The valve arrangements and valve closure times are designed such that a failure of a single valve to close will not result in unsafe turbine overspeed in the event of a trip signal. The turbine control valves are positionable by hydraulic operators. If a loss of oil pressure occurs, an independent hydraulic trip relay closes the valves.
Hydraulic fluid is supplied to the control valves by a control oil skid.
Turbine Bypass Valve and Desuperheater Turbine bypass is capable of transferring up to 100 percent of the main steam flow to the condenser to remove heat from the reactor and prevent overpressure following a reduction or loss of electrical load. A desuperheater is used downstream of the turbine bypass valve to reduce the steam temperature of bypassed steam. The design and operation of the turbine bypass valve and desuperheater is described in Section 10.4.4.
10.2.2.3 Control Functions The TGS is monitored and controlled by the main turbine control and diagnostics system, which is a subsystem of the TGS. The main turbine control and diagnostics system interfaces with the module control system (MCS). The turbine trip output from the main turbine control and diagnostics system to the MCS is redundant and hard wired. Alarm signals are transmitted from the main turbine control and diagnostics system to the MCS for monitoring and display. The MCS provides instrumentation and control of the TGS inside the main control room. The startup, shutdown, and normal operation functions of the TGS are controlled. The main control room also provides indication and control of turbine generator supporting systems such as the lube oil subsystem, stop valves and drain valves. The TGS instrument list is provided in Table 10.2-3. In addition to control room indication, local indication is provided within the turbine generator building. Additional information on the module MCS is provided in Chapter 7. A list of major TGS controls is provided in Table 10.2-4.
COL Item 10.2-1:
Not used.
10.2.2.3.1 Speed Control The module control system provides automatic turbine speed control. On startup, after the turbine reaches full speed, the governor maintains the speed and allows for generator synchronizing to begin.
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-6 Revision 4.1 After synchronizing, minimal operator action is necessary for the TGS when the control system is placed in automatic mode. Steam throttling via the TGS control valves is the primary method for power maneuvering.
10.2.2.3.2 Load Control Anticipated load profiles can be accommodated by the equipment. The TGS is designed to remain online following a sudden load reduction down to the minimum operating load.
base load operation and load follow operation.
electric power production consistent with the capability of the NPM and main steam system.
a 24-hour load operating cycle with the following profile: starting at 100 percent power, power ramps down to 50 percent power in two hours, power remains at 50 percent for two to ten hours, and then ramps up to 100 percent in two hours. Power remains at 100 percent for the remainder of the 24-hour cycle.
an automatic mode in response to grid frequency changes.
satisfy peak-to-peak power change demands of 10 percent of NPM rating at 2 percent of NPM rating per minute.
satisfy 20 percent of rated power step demand increase or decrease within ten minutes.
the capability to perform an increase or decrease of 10 percent in 60 seconds without trip while operating between 50 and 100 percent power.
the capability to remain online following a sudden load reduction down to the minimum operating load.
10.2.2.3.3 Overspeed Protection Turbine control and overspeed protection controls turbine action under normal or abnormal operating conditions and ensures that a full load turbine trip does not cause the turbine to overspeed beyond acceptable limits.
COL Item 10.2-2:
Not used.
10.2.2.3.4 Loading and Startup Controls The TGS is mainly an automatically operated system with turbine stop valve and control valves being the primary method for power maneuvers.
The turbine generator unit uses an automatic startup system. Using turbine overspeed sensors, the turbine control system manipulates the stop valve as well as the control valves in the steam chest to follow the startup curve for the turbine.
This is to ensure the speed probes in the overspeed control and governor are working properly. As speed increases, operations personnel verify that vibration measurements and rotor position indicators are acceptable. After the turbine
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-7 Revision 4.1 reaches 100 percent speed, the governor maintains the speed and allows for generator synchronizing to begin.
Before closing the generator breaker, the generator frequency, phase, and voltage must be matched to the grid. The generator can either be manually or automatically synchronized.
10.2.2.4 Turbine Protection System Automated operations trip the turbine or generator on trip set points, including:
reactor scram turbine overspeed low lube oil pressure high vibration low vacuum on condenser arcing on generator improper generator ground under or over voltage on generator from grid under or over frequency on generator from grid The loss of connection from generator to grid does not trip the turbine. The NuScale Power Plant is designed with the capability to operate independently from the offsite power system in island mode (Section 8.3).
A turbine or generator trip causes the turbine stop valve to quickly isolate, causing an increase in steam pressure. This pressure is managed using the turbine bypass valve (see Section 10.4.4), part of the TGS.
The turbine bypass valve is capable of transferring up to 100 percent of the main steam flow to the condenser following a turbine trip or loss of electrical load.
10.2.2.5 Inspection and Testing Major system components are accessible for inspection and are available for testing during normal plant operations. The governor and overspeed protection system are tested and inspected as recommended by the manufacturer. The stop valve and control valves are exercised at a frequency recommended by the turbine vendor or valve manufacturer.
10.2.3 Not Used COL Item 10.2-3:
Not used.
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-8 Revision 4.1 10.2.4 Safety Evaluation The TGS serves no safety-related functions, is not credited for mitigation of a design basis accident, and has no safe shutdown functions. General Design Criterion 2 was considered in the design of the TGS. The TGS system meets RG 1.29, in that the TGS is not located in areas that contain safety-related components and is not required to operate during or after an accident.
General Design Criterion 4 was considered in the design of the TGS. Appendix A of RG 1.115, Rev. 2 identifies SSC requiring protection from turbine missiles and defines those SSC as essential. Essential SSC are protected from high-trajectory and low-trajectory turbine rotor and blade fragments by using barriers in combination with physical separation of redundant safety-related equipment. Section 3.5.1 describes how the protection of essential SSC is accomplished using barriers.
General Design Criterion 5 was considered in the design of the TGS. The components of the TGS are not shared among NPMs, so their failure does not impair the ability of other NPMs to perform their safety functions.
The requirements of 10 CFR 20.1101(b) was considered in the design of the TGS.
Radiological considerations do not affect access to system components during normal conditions. Therefore, radiation shielding is not provided for the TGS and associated components. However, in the event of a primary to secondary system leak or steam generator tube failure, the steam could become contaminated. The Technical Specifications (Chapter 16) provide a maximum limit on secondary coolant activities. If a steam generator tube failure is detected, the secondary coolant is sampled and a radiation survey is completed for ALARA purposes before performing maintenance or modification work on the system. Access to the areas containing the system is restricted if required based on the survey results. The TGS provides for continuous monitoring for radioactivity in the effluent discharge.
Instrumentation is provided at the condenser air removal system discharge as described in Section 11.5. The TGS design satisfies 10 CFR 20.1406 requirements relating to minimization of contamination of the facility. Further discussion of the facility design features to protect against radioactive contamination is provided in Section 12.3.
Chapters 11 and 12 discuss the potential radiation of a primary to secondary coolant leak.
Section 15.0.3 discusses the radiological consequences of a steam generator tube failure.
10.2.5 References 10.2-1 Not used.
10.2-2 Not used.
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-9 Revision 4.1 Table 10.2-1: Turbine Generator Design Parameters Component Parameter Value Turbine Rotor
- Single Turbine
- 10 stage condensing
- Uncontrolled extraction
- Integrally forged
- ASTM A470 CL4 or equal Blades ASTM A276 - A403 or equal RPM 3600 rpm Generator Generator power output 50MWe Apparent Power Greater than 57,000 kVA Active Power Greater than 48,000 kWe Power Factor 0.85 p.f Phase/Frequency/Voltage 3PH/60Hz/13.8kV Cooling Type Air (TEWAC - Totally Enclosed Water to Air Cooling)
Lube Oil Oil Type ISO VG 32 Normal Power 3/60/460 VAC Emergency Power 250 VDC Valves Turbine control valves Multiple standard globe valves, with internal spring and yoke Stop valve One hydraulically operated positionable trip valve with throttling pilot for startup operation
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-10 Revision 4.1 Table 10.2-2: Not Used
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-11 Revision 4.1 Table 10.2-3: Turbine Generator System Instrument List Equipment Name Monitored Parameter Local Display Signal to Module Control System TG DSH Steam Supply MOV FCV Position Transmitter Valve Position Percent Yes Yes TG DSH FW Supply Pressure Transmitter Pressure PSIG Yes Yes TG DSH FW Supply MOV FCV Position Transmitter Valve Position Percent Yes Yes TG DSH Exit Steam Temperature Transmitter Temperature °F Yes Yes Voltage Meter (upstream & downstream of breaker)
V Yes Yes Generator Frequency cps Yes Yes VARS Meter vars Yes Yes MWe Indication MWe Yes Yes RPM rpm Yes Yes Vibration Monitoring Yes Yes Electrical System Lockouts Yes Yes Sync-Scope (synchronize with the grid)
Yes Yes Steam Pressure at Each Turbine Stage psia Yes Yes Stop Valve Position Yes Yes Control Valve Position Yes Yes Generator Ground N/A Yes Generator Arcing N/A Yes Anti-pumping/Reverse Motor N/A Yes
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-12 Revision 4.1 Table 10.2-4: Turbine Generator Control List Description Automatic/Manual Local Control Room RPM Automatic and Manual N
Y Frequency Control Automatic and Manual N
Y Electrical System Lockouts Manual N
Y Sync-Scope (synchronize with the grid)
Automatic and Manual N
Y Emergency Turbine Generator Trip Automatic and Manual N
Y Lube Oil Skid Operation Automatic and Manual N
Y
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-13 Revision 4.1 Figure 10.2-1: Turbine Generator System Piping and Instrumentation Diagram Turbine Condenser Desuperheater Notes:
1.
Vents and drains not shown.
- 2. Steam traps not shown.
- 3. A single inlet is shown for lube oil and gland sealing steam into the turbine even though there are multiple inlets.
- 4. single turbine control valve shown, may have multiple control valves in the steam chest depending on turbine vendor design.
- 5. For simplicity, a single instrument of each type is shown in each location.
LI Gland Seal Condensate Tank Gland Steam Condenser LI From Condensate Pump Gland Steam Condenser Exhaust Fans PI RE Sample Point Exhaust Vent Generator TE PI PI From Feedwater System Injection Cooling TGS CFWS Turbine Bypass Valve To HP Feedwater Heater To IP Feedwater Heater To LP Feedwater Heater MSS TGS MSS TGS FI TE PI PI TE Turbine Stop Valve PI TE Control Oil Skid PI TE Lube Oil Skid Gland Steam Desuperheater From Feedwater System Injection Cooling TGS CFWS PI Aux. Boiler Steam System TGS CFWS PI TE TGS CFWS TGS CFWS CFWS TGS Turbine Control Valve SE To LP FW Heater
NuScale Final Safety Analysis Report Turbine Generator Tier 2 10.2-14 Revision 4.1 Figure 10.2-2: Not Used
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-1 Revision 4.1 10.3 Main Steam System The primary function of the main steam system (MSS) is to transport steam from the steam generators to the turbine generator system. Each NuScale Power Module (NPM) is supplied with a separate MSS.
The containment-penetrating steam supply is divided into three portions: internal to containment discussed in Section 5.4, the containment and safety-related main steam isolation valves (MSIVs) discussed in Section 6.2, and the nonsafety-related portion discussed in this section.
The MSS extends from the flange immediately downstream of the MSIVs to the inlet of the turbine generator vendor package. The extraction points from the turbine to the feedwater heaters are also considered part of the MSS although there is no direct connection to the other MSS piping.
10.3.1 Design Bases This section identifies the MSS required or credited functions, the regulatory requirements that govern the performance of those functions, and the controlling parameters and associated values that ensure that the functions are fulfilled. Together, this information represents the design bases defined in 10 CFR 50.2 for the MSS, as required by 10 CFR 52.47(a) and 10 CFR 52.47(a)(3)(ii).
The MSS is nonsafety-related. One nonsafety-related secondary MSIV is located downstream of each containment system MSIV as backup for the performance of the containment system MSIV design bases functions as outlined in Section 6.2.4.
General Design Criteria (GDC) 2, 4, and 5 were considered in the design of the MSS. No safety-related structures, systems, and components (SSC) are affected by the effects of natural phenomena such as earthquakes. The design of the MSS provides protection of safety-related SSC from the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents. There are no safety-related components in the MSS that are shared among NPMs; therefore, the loss of components in one MSS does not impair the ability of other NPMs to perform their safety functions.
The NPM decay and residual heat removal safety function is performed by the decay heat removal system (DHRS) flowpath requiring containment isolation. Consistent with Principal Design Criteria (PDC) 34, the secondary MSIVs provide a nonsafety-related backup to the containment MSIVs, and provide additional assurance that the blowdown of a second steam generator (SG) is limited if a steamline were to break upstream of the MSIV.
Secondary system isolation (SSI) is provided to protect the steam generator inventory without an unnecessary cooldown. Conformance with PDC 34 is further discussed in Section 5.4 and Section 10.3.3.
Consistent with 10 CFR 50.63, the nonsafety-related portion of the MSS is not relied upon to operate in response to a station blackout (SBO). Rather, the DHRS operates in conjunction with the ultimate heat sink to fulfill the core cooling function in the event of an SBO.
Conformance with 10 CFR 50.63 and the guidelines of Regulatory Guide 1.155 are discussed in Section 8.4.2 and Section 10.3.3.
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-2 Revision 4.1 Consistent with 10 CFR 20.1101(b), the MSS design supports keeping radiation exposures as low as reasonably achievable (ALARA). Consistent with 10 CFR 52.47(a)(6), the MSS is designed to meet the requirements of 10 CFR 20.1406 as it relates to minimizing contamination of the facility. The MSS is not normally a radiation hazard in a pressurized water reactor. Further discussion of the facility design features to protect against contamination is provided in Section 12.3. See Section 10.3.3 for the MSS safety evaluation.
10.3.2
System Description
The MSS (one per NPM) performs a number of nonsafety-related functions including:
delivers steam from the steam generators
To the turbine generators for the entire range of flow rates, temperatures, and pressures from warming of the main steam piping to rated power conditions; the turbine generator is described in Section 10.2.
To the gland seal regulator; the gland sealing steam is described in Section 10.4.3.
Directly to the condenser through the turbine bypass valve. As described further in Section 10.4.4, the MSS, together with turbine bypass, is capable of accepting 100 percent load rejection without a reactor trip.
collects the drainage condensed in the main steam piping and delivers it to the main condenser provides a means of dissipating residual and sensible heat generated by the NPM during hot standby and cooldown operations by bypassing to the main condenser transports extraction steam from the turbine to the feedwater heaters and the gland seal condenser provides turbine bypass steam to the condenser provides steam header pressure to the feedwater system to support measurement of the differential pressure across the steam generator 10.3.2.1 General Description Each NPM has two steam generators and a dedicated MSS. The MSS includes pipe, fittings, drains, valves, main steam safety valves (MSSV), and instruments from the flanges immediately downstream of the containment system MSIVs up to the turbine stop valve. A common section of MSS piping is provided to mix and equalize the output of the two SG lines before the steam is directed to the turbine generator. The MSS also includes the extraction steam from the turbine generator to the three feedwater heaters located in the Turbine Generator Building (TGB) and the steam supply to the gland seal steam.
Figure 10.3-1 provides a simplified piping and instrumentation diagram for the main steam system. Table 10.3-1 provides design and operational data for the MSS.
Upstream of the secondary MSIVs, connections are provided for the removable pipe spool and the secondary main steam isolation bypass valves (MSIBV). Branch piping inside the reactor building (RXB) downstream of the secondary MSIVs is limited to the
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-3 Revision 4.1 nitrogen system (Section 9.3.1) connections for dry layup, and an additional safety valve in the secondary MSIV bypass line to protect the bypass piping during start-up operations.
The two steam lines combine to mix and equalize the output of the two SG coils. A pipe rack supports the MSS piping and components from the RXB wall to the ((TGB wall)).
Outside of the RXB, sampling points are provided on each main steam line. The MSS piping is protected from overpressure by MSSVs ((outside the TGB wall)) upstream of the sampling and auxiliary steam connections.
Branch piping inside the TGB for each MSS provides for turbine bypass to the main condenser, secondary sampling system, low point drains, feedwater heater steam, and backup auxiliary steam. The MSS provides gland steam through the auxiliary boiler system header. Connections allowing sampling are provided in appropriate locations in the secondary side piping. The secondary sampling system is described in Section 9.3.2.
As discussed in Section 10.3.1, the portion of each MSS up to and including the secondary MSIVs provides nonsafety-related backup to the MSIVs for safety-related isolation functions, and for the safety-related decay and residual heat removal safety function in PDC 34.
Design considerations of the MSS are reflected in the failure modes and effects analyses summarized in Section 5.4 (specific to providing backup to DHRS operation) and Table 10.3-2 (specific to providing backup of containment and secondary system isolation functions of the MSS). Failure modes and effects analysis for MSIV and MSIV bypass valves can be found in Table 6.2-6.
The MSS is designed to permit appropriate functional testing of system components as described further in Section 10.3.2.2 and Section 10.3.4.
The MSS piping upstream of the secondary MSIVs is designed to not exceed its service limits during a design basis event. Administrative procedures preclude filling the SG and MSS piping water-solid during normal operation, as well as during DHRS operation.
The MSS has leak detection capabilities. An MSS steam line break is detected as low steam line pressure by pressure sensors located on the DHRS steam piping section between the DHRS actuation valves and the CNTS steam line (Section 5.4.3). This causes an isolation signal to the MSIVs, and closure signals to the turbine bypass valve, turbine stop valve, and drain line isolation valves to limit blowdown of the system.
Section 5.4.1 provides a description of SG design features to minimize fluid flow water hammer. The design and layout of the MSS include provisions to minimize the potential for water hammer and other flow instabilities (Section 3.6.3).
10.3.2.2 Component Description The major components of the MSS include the piping, secondary MSIVs, secondary main steam isolation bypass valves, MSSVs, drains, and associated supports and
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-4 Revision 4.1 appurtenances. The design and operational characteristics of these components are described below. Design parameters and associated values are provided in Table 10.3-1.
The portion of the MSS from the outlets of the MSIVs to the first piping restraint downstream of the MSIVs is nonsafety-related, Seismic Category I, and quality group D.
The remainder of the MSS is classified as nonsafety-related, non-seismic, and quality group D. Consistent with Regulatory Guide 1.26, these portions are designed in accordance with the provisions of ASME Power Piping Code Section B31.1. Additional detail of the safety, quality, and seismic classification of the MSS components is provided in Section 3.2.
Main Steam Piping Figure 10.1-1 depicts the MSS boundaries, including interconnections with other systems.
The two steam lines combine to mix and equalize the output of the two SG coils.
Flanges immediately downstream of the MSIVs are provided to enable disconnection of the piping from the NPM in preparation for moving the module for refueling or maintenance. Immediately downstream of the flanges, the MSS lines pass through the secondary MSIV and secondary MSIBVs. Ball-joint type flanges are used downstream of the secondary MSIVs to reduce containment vessel nozzle stress.
The steam lines from six NPMs are then routed inside the RXB toward the center of the building and then exit the building above ground. They are supported on a pipe rack between the RXB and the TGB.
In the TGB, the MSS lines are each routed to their separate turbine generator set.
Secondary Main Steam Isolation Valves Design parameters and associated values for the secondary MSIVs are provided in Table 10.3-1.
Each secondary MSIV is provided with two independent actuator control systems to ensure successful performance of the secondary MSIV function, assuming a single failure. In response to a DHRS actuation signal and SSI signal, the secondary MSIVs automatically close. The secondary MSIVs are capable of closing in steam conditions.
The nonsafety-related secondary MSIVs are used for event mitigation as backup protection for the safety-related MSIVs as described in Section 15.0.0.6.6. The secondary MSIV is a commercially available valve that utilizes a proven design and demonstrates reliable operation based on operating experience in steam systems. A design with no previous operating experience may be proven through testing to demonstrate that the valve can reliably close within the required time specified in Table 10.3-1 at full power steam flow and pressure conditions.
Each secondary MSIV is periodically tested in accordance with the Augmented Valve Testing Program described in FSAR Section 3.9.6.5. These valves are designed with the
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-5 Revision 4.1 capability to periodically test the operability of the valve and associated apparatus, and to determine if valve leakage is within acceptable limits. Each secondary MSIV is seat leakage tested in the forward and reverse flow directions by the valve supplier. Valve functions and periodic testing requirements are specified in FSAR Table 3.9-17.
Secondary Main Steam Isolation Bypass Valves Each of the two secondary MSIVs has a bypass valve that may be used for pressure equalization and warming during NPM startup. The secondary MSIBVs are normally closed and are Seismic Category I, quality group D, ASME B31.1 components. An isolation valve is provided to allow secondary MSIV maintenance, and a safety valve is provided on the bypass line for overpressurization protection. The nonsafety-related secondary MSIBVs are used as backup protection for the safety-related MSIBVs as described in Section 15.0.0.6.6. The secondary MSIBV is a commercially available valve that utilizes a proven design and demonstrates reliable operation based on operating experience in steam systems. A less proven design can be utilized with qualification testing to demonstrate that the valve can reliably close within the time specified in Table 10.3-1 at full power steam flow and pressure conditions.
Each secondary MSIBV is periodically tested in accordance with the Augmented Valve Testing Program described in FSAR section 3.9.6.5. Valve functions and periodic testing requirements are specified in FSAR Table 3.9-17.
Main Steam Safety Valve The MSS piping is protected from overpressure by the use of 2 MSSVs located in the main steam header at the ((TGB wall)). The MSSVs exhaust steam to the atmosphere outside the TGB.
Condensate Drains The main steam piping layout provides for the collection and drainage of condensate to avoid water entrainment. The MSS lines are sloped in the direction of steam flow.
Drains are located and sized to allow the removal of water prior to and during initial rolling of the turbine and during MSS shutdown. Condensate from the MSS drains is routed to the main condenser.
10.3.2.3 System Operation NuScale Power Module and Main Steam System Startup The MSS startup coincides with startup of the associated NPM. Prior to reactor heat-up, the secondary MSIBVs are opened and the entire MSS is warmed at once. Condenser vacuum is established and MSS heat-up is controlled by turbine bypass (Section 10.4.4) to the main condenser. During plant startup, condensate is generated in the main steam piping and is removed through low point drains to prevent water hammer and turbine damage.
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-6 Revision 4.1 Main Steam System Operation During Power Operations During normal operation, the MSS supplies steam from the MSIV outlets to the turbine.
Steam flow is decreased by the turbine control valves to operate at partial load, as required. Both of the steam generators in the NPM reactor pressure vessel are in operation, discharging steam to the turbine. Extraction steam from the turbine is supplied to the feedwater heaters.
During normal power operation, main steam flow is a function of turbine load; steam pressure is not controlled, but varies with turbine load. In the case of core power exceeding turbine load, excess steam is dumped to the main condenser through the turbine bypass system (Section 10.4.4).
NuScale Power Module and Main Steam System Shutdown Main steam system shutdown coincides with shutdown of the associated NPM. The MSS and feedwater system (FWS) are used to provide cooldown from normal operating temperature to the cut-in temperature of the containment flooding and drain system as described in Section 9.3.6. Unit load is reduced to no-load, and the turbine and reactor are shut down. During shutdown and reactor cooldown, steam generated in the steam generators is dumped to the main condenser through the turbine bypass system (Section 10.4.4). During the cooldown process, the SG water inventories are maintained by the FWS.
Anticipated Operational Occurrences and Accidents Analyses of anticipated operational occurrences and postulated accidents are provided in Chapter 15. The events analyzed in Chapter 15 may be categorized as those that involve automatic closure of the MSIVs (i.e., isolation of the power conversion system) and certain abnormal conditions that do not involve automatic closure of the MSIVs. In the latter instance, operation of the MSS is similar to that described for NPM and MSS shutdown with the use of turbine bypass to remove core decay and primary system sensible heat. Off-normal operations for which the MSS and power conversion system may be used include:
turbine trip loss of grid loss of condenser vacuum The remaining events analyzed in Chapter 15 involve automatic closure of the MSIVs upon receipt of a plant signal by the engineered safety features actuation system (ESFAS). Input signals that result in an MSIV closure signal and associated actuation setpoints and time delays are addressed in Section 15.2.4. In these instances, either or both of the DHRS (Section 5.4.3) and the emergency core cooling system (Section 6.3) are relied upon to remove the reactor decay heat and primary system sensible heat.
The analyses in Chapter 15 further describe operation of the MSS in response to postulated events, including a main steam line break and steam generator tube failure.
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-7 Revision 4.1 10.3.3 Safety Evaluation The MSS is nonsafety-related. One nonsafety-related secondary MSIV is located downstream of each containment system MSIV as backup for the performance of the containment system MSIV design bases functions as outlined in Table 6.2-6. General Design Criterion 2 was considered in the design and arrangement of main steam components. The portions of the MSS downstream of the MSIVs to the secondary MSIVs are contained in the RXB, which is a Seismic Category I structure designed to withstand the effects of natural phenomena, such as earthquakes, tornadoes, hurricanes, floods, tsunamis, and seiches. The adequacy of the structural design of the RXB to withstand these phenomena is further described in Chapter 3. Thus, the portions of the MSS downstream of the MSIVs to the secondary MSIVs are designed to remain functional during and after a safe shutdown earthquake and meet the guidelines of Regulatory Guide 1.29. The RXB is designed as an engineered barrier to withstand a postulated design basis missile. Consistent with Regulatory Guide 1.117, this satisfies the criteria of GDC 2 by the proper design and use of missile barriers (i.e., the RXB) to protect essential SSC against potential missiles generated by tornado or hurricane winds.
The portion of the MSS that is outside of the RXB is nonsafety-related. The design of the portion of MSS contained outside of the RXB satisfies GDC 2 in that the nonsafety-related portions are not located in areas that contain safety-related components and are not required to operate during or after an accident. No safety-related SSC are affected by the effects of natural phenomena such as earthquakes. The seismic and quality classifications of main steam components are described in Section 3.2. Flooding is evaluated in Section 3.4.1.
General Design Criterion 4 was considered in the design and arrangement of main steam components. Portions of the MSS are located in the RXB; thus, internally generated missiles, pipe whip, and jet impingement forces associated with pipe breaks do not prevent the MSS from performing its safety function. The portions of the MSS downstream of the MSIVs to the secondary MSIVs are protected from pipe whip and jet impingement forces resulting from breaks in nearby systems (including the MSS of adjacent power modules) by the piping design layout. The portions of the MSS downstream of the MSIVs to the secondary MSIVs are physically separated from safety-related systems in the RXB by the use of walls and other restraints and have no adverse impacts on safety functions. Refer to Section 3.12 for a description of the design of piping systems and piping supports used in Seismic Category I, Seismic Category II, and non-seismic systems. The analysis of a postulated high-energy line break is provided in Section 3.6.1 and Section 3.6.2.
The portions of the MSS downstream of the MSIVs to the secondary MSIVs are also protected from the effects of missiles generated by plant equipment failures outside the RXB by the building itself. Specifically, portions of the MSS are inside the RXB, which is a Seismic Category I structure, designed as an engineered barrier to withstand a postulated design basis missile. See Section 3.5 for the discussion of missile protection.
General Design Criterion 5 was considered in the design of the MSS. There are no safety-related components in the MSS shared among NPMs, and therefore the MSS does not impair the ability of other NPMs to perform their safety functions.
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-8 Revision 4.1 Principal Design Criterion 34 was considered in the design of the MSS. The decay and residual heat removal safety function per PDC 34 is performed by the DHRS flowpath, and containment isolation function of the containment system performed by the MSIVs and the feedwater isolation valves. Secondary system isolation is provided to protect the steam generator inventory without an unnecessary cooldown. Consistent with PDC 34, the nonsafety-related secondary MSIVs downstream of the MSIVs are credited as backup isolation components in the event that an MSIV fails to close. Although not safety-related, the secondary MSIVs are designed to close under postulated worst-case conditions and are included in technical specification surveillance requirements to ensure their reliability and operability. Thus, consistent with the position established in NUREG-0138, Issue Number 1, the secondary MSIVs ensure that the blowdown is limited if a steamline were to break upstream of the MSIV. Conformance with PDC 34 is further discussed in Section 5.4.
The requirements of 10 CFR 20.1101(b) were considered in the design of the MSS. The MSS is not normally a radiation hazard in a pressurized water reactor. Radiological considerations do not affect access to system components during normal conditions.
Therefore, no radiation shielding is provided for the MSS and associated components. It is only in the unlikely event of a primary-to-secondary system leak or SG tube failure that the steam could become contaminated. If a SG tube failure is detected, the secondary coolant is sampled and a radiation survey completed before performing maintenance or modification work on the system. Access to the areas containing the system is restricted, if required, based on the survey results. The requirements of 10 CFR 20.1406 were considered in the design of the MSS. Consistent with 10 CFR 52.47(a)(6), the MSS is designed to meet the requirements of 10 CFR 20.1406 as it relates to minimizing contamination of the facility.
Further discussion of the facility design features to protect against contamination is provided in Section 12.3.
The requirements of 10 CFR 50.63 were considered in the design of the MSS. The nonsafety-related portion of the MSS is not relied upon to operate in response to an SBO to satisfy 10 CFR 50.63. Rather, the DHRS operates in conjunction with the ultimate heat sink to fulfill the core cooling function in the event of an SBO. Successful operation of the DHRS relies on the safety-related MSIVs, which form part of the DHRS flowpath and pressure boundary. The secondary MSIVs provide backup to the MSIVs, thus are also required to fail closed during an SBO. This functionality is ensured with or without the availability of electrical power. Conformance with 10 CFR 50.63 and the guidelines of Regulatory Guide 1.155 are discussed in Section 8.4.2.
10.3.4 Inspections and Tests The MSS components are inspected and tested as part of preoperational and startup tests, and are within the scope of the initial test program described in Section 14.2.
Nonsafety-related MSS piping and components are inspected and tested in accordance with the requirements of ASME B31.1.
The proposed Inspections, Tests, Analyses, and Acceptance Criteria required by 10 CFR 52.47(b)(1) and 10 CFR 52.80(a) are discussed in Section 14.3.
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-9 Revision 4.1 10.3.5 Water Chemistry 10.3.5.1 Chemistry Control Program The SG water and feedwater quality requirements are based on current water chemistry technology reflected in EPRI chemistry guidelines (Reference 10.3-1 and Reference 10.3-2) and NEI 97-06 (Reference 10.3-3).
Consistent with this guidance, the secondary water chemistry control program includes control and diagnostic parameters, and associated action limits. Additional control and diagnostic parameters have been included as appropriate based on industry experience and other available information.
The secondary water chemistry control program is implemented by plant operating procedures, which control the recording and management of data, and require appropriate corrective actions in response to abnormal chemistry conditions.
COL Item 10.3-1:
A COL applicant that references the NuScale Power Plant design certification will provide a site-specific chemistry control program based on the latest revision of the Electric Power Research Institute Pressurized Water Reactor Secondary Water Chemistry Guidelines and Nuclear Energy Institute (NEI) 97-06 at the time of the COL application.
10.3.5.1.1 Chemistry Control Objectives and Basis The objectives of the secondary water chemistry program are:
to protect the steam generators, turbine, and FWS from general and localized corrosion caused by the ingress of oxygen and other chemical contaminants to minimize the metal release rate from the steam-water cycle materials in order to reduce the transport of corrosion products into the steam generators The secondary chemistry program addresses these objectives by controlling system pH, controlling the amount of oxidants and minimizing the amount of contaminants in the system. Water chemistry recommendations for secondary systems invoke plant and operational philosophies that address the control of corrosion products and dissolved impurities by minimizing potential sources, and by implementing effective monitoring. Secondary system components and piping exposed to wet steam, flashing liquid flow, or turbulent single-phase flow where loss of material could occur use corrosion, erosion, and flow-accelerated corrosion (FAC) resistant materials. The degree of resistance of the material to FAC, corrosion, and erosion is consistent with specific conditions of the fluid stream involved.
Copper deposits are a major source of corrosion products in the steam generators in plants with copper alloys in their secondary system. The elimination of copper from the secondary system mitigates copper transport to the steam generators.
The use of ferrous materials allows the implementation of a higher feedwater pH target compared to systems that use copper. The use of a higher feedwater pH reduces iron corrosion and iron transport to the steam generators. Therefore,
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-10 Revision 4.1 emphasis is placed on excluding copper and copper alloy pipe, valves, and components from the secondary chemistry environment.
10.3.5.1.2 Water Chemistry Treatment and Monitoring The secondary water chemistry control program includes methods of treatment for corrosion control and proposed specification limits such that the barrier between the primary and secondary fluids maintains its integrity during operation (including design basis accidents), maintenance, and testing. Guidelines for secondary side water chemistry are addressed in Table 10.3-3a through Table 10.3-3e.
An all-volatile treatment amine, such as ammonium hydroxide is added to the feedwater to establish an optimum pH level. Hydrazine is also added to control the residual dissolved oxygen concentration and to maintain a passive protective film of magnetite on carbon steel surfaces.
10.3.5.1.3 Chemistry Sampling The secondary system for each NPM is designed to allow for chemistry sampling and analysis, both continuous and grab samples, from selected locations to monitor water quality. Analyses of the chemistry samples are used to control the secondary side water chemistry and to permit corrective actions to be taken in the event of contaminant ingress or other chemistry excursion.
Design of the secondary sampling system considers sampling flow velocities, sample tubing length, and routing of the sample tubing to prevent impurities from settling out in the tubing and to obtain representative samples for analysis.
Continuous sampling flows have bypass flow provisions to maintain flow velocities sufficient to prevent settling of suspended solids in the sample lines.
10.3.5.2 Contaminant Ingress There are several sources that may introduce contaminants into the secondary system during operation condenser cooling water in-leakage, poor quality makeup water, improperly regenerated condensate polishers, atmospheric leaks at the condenser or pump seals, and contaminated water treatment chemicals.
The contaminated water treatment chemicals as source of contaminants is controlled by the chemical use and control program.
The remaining sources of contaminants, described below, are detected by continuous monitoring or sample analysis, and appropriate action is taken following detection to locate and to correct the problem.
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-11 Revision 4.1 Contaminants that enter the system through condenser tube leaks are detected by continuous process monitoring of the condenser hotwells for cation conductivity and sodium and the condensate pump discharge for straight conductivity, cation conductivity, and dissolved oxygen.
The condensate polisher discharge is continuously monitored for cation conductivity, dissolved oxygen, and sodium when in use.
Demineralized water is continuously monitored as it is being produced and the demineralized water storage is routinely sampled to verify makeup water quality.
Air inleakage is detected by monitoring the condensate pump discharge for excessive dissolved oxygen and by monitoring the condenser air removal rate.
Condensate polishers are used in the condensate system during plant startup and shutdown to remove both dissolved and particulate contaminants prior to admitting feedwater to the steam generators. This practice achieves the required water purity in a shorter time and prevents these contaminants from entering the steam generators.
Condensate polishers are intended to be used continuously during power operation.
Their use is important in the event of an upset in chemistry conditions, for example, during periods of condenser cooling water leakage or when inadequate performance of the makeup water system would introduce impurities to the steam generators. They also assist in minimizing iron transport to the steam generators. Additional information on the condensate polishing system is provided in Section 10.4.6.
10.3.5.3 Primary-to-Secondary Leakage Leakage of primary water into the SG tubes from through-wall tube defects would represent a source of radioactive iodine to the secondary system. The volatility of radioactive iodine is increased by acidic and oxidizing solutions. The secondary side chemicals added (Section 10.3.5.1.2) make the secondary side chemistry both basic and reducing. These conditions suppress the volatility of radioactive iodine species, thus minimizing release through the main condenser evacuation system.
The implications of detecting radioactivity in the secondary side are addressed by the requirements identified in Section 11.5.
10.3.5.4 Chemical Addition System Equipment is provided to inject controlled quantities of treatment chemicals as part of the secondary water chemistry program. These treatment chemicals are injected into the condensate pump discharge header. See details for the feedwater treatment system in Section 10.4.11.
10.3.6 Steam and Feedwater System Materials The portion of the steam and power conversion system discussed under this section includes the turbine generator system (including the turbine bypass system and the turbine gland sealing system), the MSS (including extraction steam), the condensate and feedwater system (including the condensate polishing system), and the auxiliary boiler
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-12 Revision 4.1 system. This portion of the steam and power conversion system is outside containment, is nonsafety-related and is not relied upon to perform a nuclear safety function.
10.3.6.1 Fracture Toughness The quality group for the portions of the steam and power conversion system noted in Section 10.3.6 above is quality group D, thus the piping is non-nuclear safety ASME B31.1 piping. The piping materials for the portions of the steam and power conversion system noted in Section 10.3.6 above meet ASME B31.1 requirements.
10.3.6.2 Materials Selection and Fabrication Material selection and fabrication requirements for the steam and power conversion system conform to ASME B31.1 and are consistent with the quality group and seismic design classifications provided in Table 3.2-1.
The materials of the safety-related portions of the containment system, SGS and DHRS in conjunction with the secondary water chemistry control program described in Section 10.3.5 provide protection from contamination originating in the nonsafety steam and power conversion systems from impacting safety-related portions of the containment system, SGS or DHRS.
10.3.6.3 Flow-Accelerated Corrosion The design of the piping in the steam and power conversion systems incorporates considerations to prevent the occurrence of erosion and corrosion. These considerations include material selection, limits on flow velocity, inspection programs, and limits on water chemistry to reduce FAC. The design meets the guidance contained in Generic Letter 89-08 and NSAC-202L-R3 (Reference 10.3-1) governing design considerations to minimize FAC including FAC monitoring programs.
The steam and power conversion systems design and layout incorporate appropriate provisions to minimize FAC. These provisions are applied to the high-energy, nonsafety-related portions that could adversely impact safety-related systems susceptible to FAC and other flow-induced degradation mechanisms.
Table 10.3-5 provides a list of power conversion system piping which is within the scope of the flow-accelerated corrosion monitoring program.
In addition to design and layout provisions, flow-accelerated corrosion is minimized by the implementation of a secondary water chemistry control program as described in Section 10.3.5.
COL Item 10.3-2:
A COL Applicant that references the NuScale Power Plant design certification will provide a description of the flow-accelerated corrosion monitoring program for the steam and power conversion systems based on Generic Letter 89-08 and the latest revision of the Electric Power Research Institute NSAC-202L at the time of the COL application.
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-13 Revision 4.1 10.3.7 Instrumentation The main steam temperature, pressure, radiation, and flow instrumentation is designed to permit automatic plant operation, remote control, and continuous indication of system parameters. The remote instrumentation readouts required for monitoring the system are provided in the main control room. The ability to manually initiate MSS control actions is available in the main control room.
Table 10.3-4 shows the MSS instrumentation. A list of the instrumentation associated with SSI actuation and DHRS actuation and operation (including MSIV and secondary MSIV closure) is provided in Section 7.1.
The instrumentation and controls associated with turbine bypass are described in Section 10.4.4.
10.3.8 References 10.3-1 Electric Power Research Institute, "Recommendations for an Effective Flow-Accelerated Corrosion Program (NSAC-202L-R3) Non-Proprietary Version," EPRI #1015425, Final Report, Palo Alto, CA, 2007.
10.3-2 Electric Power Research Institute, "Pressurized Water Reactor Secondary Water Chemistry Guidelines, EPRI #1016555 Rev. 7, February 17, 2009, Palo Alto, CA.
10.3-3 Nuclear Energy Institute, "Steam Generator Program Guidelines," NEI 97-06, Rev 3, Washington, DC, January 2011.
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-14 Revision 4.1 Table 10.3-1: Main Steam System Design Data (Single NuScale Power Module)
Design Parameter Rated Conditions Full power steam flow Total 532,100 lbm/hr Design Conditions Design pressure upstream/downstream of the secondary MSIVs 2100 psia/ 1000 psia Design temperature 650 °F Operating Conditions Pressure at rated power 500 psia Temperature at rated power 575 °F Secondary Main Steam Isolation Valves Number per main steam line 1
Total number of valves / valve type 2/ gate valve Valve size 12 in.
Design code ASME B31.1 Seismic Category I
Actuator System hydraulic or pneumatic Closure speed Within 7 seconds Secondary Main Steam Isolation Bypass Valves Number per main steam line 1
Total number of valves 2
Valve size 4 in.
Design code ASME B31.1 Seismic Category I
Actuator System Air operated Closure speed Within 7 seconds Main Steam Safety Valves Total number of valves 2
Valve size 4 in. (inlet), 6 in. (outlet)
Valve capacity Greater than 50% of design steam flow
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-15 Revision 4.1 Table 10.3-2: Main Steam System Failure Modes and Effects Analysis (Isolation Functions)
Component Identification Function Failure Mode Failure Mechanism Effect on System Method of Failure Detection Remarks Secondary MSIVs (nonsafety-related)
XX*-MS-AOV-0102 XX*-MS-AOV-0202 (normally open, fail close)
XX* reserved for module number (01 - 12)
Isolate steam generators from each other by isolating MSS headers due to a module control system (MCS) close signal.
Fails open (steam line break)
Mechanical Electrical / I&C (failure to close)
Valve MS-AOV-0102 (0202) remains open.
- 1) If the break is upstream of MS-AOV-0102 (0202), then MS-HOV-0101 (0201) and MS-HOV-0103 (0203) close to isolate the steam line break. Both steam generators are isolated from the break.
- 2) If the break is downstream of MS-AOV-0102 (0202), then MS-HOV-0101 (0201) and MS-HOV-0103 (0203) close to isolate the steam line break. Both steam generators are isolated from the break.
Main control panel valve position indication Steam header pressure Steam flow For a break downstream of MS-HOV-0101 (0201),
the steam generators are isolated from the break and are available for heat removal via the DHRS.
Fails open (steam generator tube failure)
Valve MS-AOV-0102 (0202) remains open.
If the failure is on SG2 (1) (the SG without the tube failure) and MS-AOV-0202 (0102) remains open, then MS-HOV-0101 (0201) and MS-HOV-0103 (0203) closes to isolate the break.
MS-HOV-0201 (0101) and MS-HOV-0203 (0103) isolate the non-affected SG2 (1).
If the failure is on SG1 (the SG with the tube failure) and MS-AOV-0102 (0202) remains open, then MS-HOV-0101 (0201) and MS-HOV-0103 (0203) isolate the break.
MS-HOV-0201 (0101) and MS-HOV-0203 (0103) isolate the non-affected SG2 (1).
MS line radiation monitor Pressurizer level response Makeup flow ESFAS actuation The failed SG tube fills up the steam line to the closed MSIV (affected SG). The non-affected SG is available for heat removal via the DHRS.
Fails closed (during normal operation)
Mechanical Electrical / I&C (fails closed)
Operator error Valve MS-AOV-0102 (0202) closes.
Rapid decrease in steam flow and subsequent loss of reactor coolant heat removal capability. Bounded by turbine trip event.
Main control panel valve position indication Steam flow The turbine trip event bounds this scenario.
Fails partially closed (during normal operation)
Valve MS-AOV-0102 (0202) partially closes.
This could be seen as a small reduction in steam flow up to a large reduction in steam flow.
For a small reduction in steam flow, the reactor follows steam demand and stabilizes at a lower reactor power.
If the failure is significant enough, it is similar in response to the complete closure of the valve discussed above.
Main control panel valve position indication Steam flow The turbine trip event bounds this scenario.
Fails to close on demand Mechanical Electrical / I&C Valve MS-AOV-0102 (0202) fails open when commanded to close. MS-HOV-0101 (0201) and MS-HOV-0103 (0203) close on redundant signal and isolate the steam generators.
The turbine trip event bounds this scenario.
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-16 Revision 4.1 Secondary MSIBVs (nonsafety-related)
XX*-MS-AOV-0104 XX*-MS-AOV-0204 (normally closed, fail close)
XX* reserved for module number (01 - 12)
Isolate steam generators from each other by isolating MSS headers due to MCS close signal.
Spuriously opens (steam line break)
Mechanical There is no credible mechanism for this valve to mechanically fail open.
N/A Electrical / I&C Operator error Valve MS-AOV-0104 (0204) fails open
- 1) If the break is upstream of MS-AOV-0104 (0204), then MS-HOV-0101 (0201) and MS-HOV-0103 (0203) close to isolate the steam line break. Both steam generators are isolated from the break.
- 2) If the break is downstream of MS-AOV-0104 (0204), then MS-HOV-0101 (0201) and MS-HOV-0103 (0203) close to isolate the steam line break. Both steam generators are isolated from the break.
Main control panel valve position indication Steam header pressure Steam flow For a break downstream of MS-HOV-0101 (0201),
the steam generators are isolated from the break and are available for heat removal via the DHRS.
Spuriously opens (steam generator tube failure)
Electrical / I&C Operator error Valve MS-AOV-0104 (0204) opens.
If the failure is on SG2 (the SG without the tube failure) and MS-AOV-0204 (0104) opens, then MS-HOV-0101 (0201) and MS-HOV-0103 (0203) isolate the break. MS-HOV-0201 (0101) and MS-HOV-0203 (0103) isolate the non-affected SG2 (1).
If the failure is on SG1 (the SG with the tube failure) and MS-AOV-0104 (0204) opens, then MS-HOV-0101 (0201) and MS-HOV-0103 (0203) isolate the break. MS-HOV-0201 (0101) and MS-HOV-0203 (0103) isolate the non-affected SG2 (1).
MS line radiation monitor Pressurizer level response Makeup flow ESFAS actuation The failed SG tube will fill up the steam line to the closed MSIV (affected SG). The non-affected SG is available for heat removal via the DHRS.
Table 10.3-2: Main Steam System Failure Modes and Effects Analysis (Isolation Functions) (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-17 Revision 4.1 MSSVs (nonsafety-related)
XX*-MS-RV-0302 XX*-MS-RV-0304 Normally closed XX* reserved for module number (01 - 12)
Provide overpressure protection for steam lines downstream of secondary isolation valves (MS-AOV-0102/
0202)
Spuriously opens Mechanical (spring failure)
Valve MS-RV-0302 (0304) opens.
Each MSSV has a flow rate of greater than 50 percent flow.
Therefore, this failure causes a plant response that is similar to a steam line break event. This failure is bounded by the steam line break event Steam header pressure Decrease in turbine output due to loss of flow Feedwater heater isolation valve (nonsafety-related)
XX*- MS-MOV-0026 XX*- MS-MOV-0028 XX*- MS-MOV-0030 Normally closed, fails closed XX* reserved for module number (01 - 12)
Direct steam to feedwater heaters Spuriously closes Electrical / I&C Operator error Valve MS-MOV-0026 or 0028 or 0030 fails closed This failure would result in a loss of feedwater heating and a colder feedwater temperature to the steam generators. This is bounded by the decrease in feedwater temperature event.
Main control panel valve position indication Feedwater temperature Table 10.3-2: Main Steam System Failure Modes and Effects Analysis (Isolation Functions) (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-18 Revision 4.1 Notes:
a)
Alternative oxygen scavenger to hydrazine (if used) must be qualified by the utility prior to use. Revised limits applicable to the hydrazine alternative will be used.
Table 10.3-3a: SG Sample (Wet Layup) (Reactor Coolant System 200°F)
Parameter Normal Value Value Necessary Prior to Heatup Above >200°F pH @ 25°C 9.8 Hydrazinea, ppm 25
>3 x Oxygen (ppm)
Sodium, ppb 1000 100 Chloride, ppb 1000 100 Sulfate, ppb 1000 100 Diagnostic Parameters Analysis Basis Nitrogen overpressure, psig Minimize oxygen ingress to the SGs Hideout return Analysis (Na, Cl, SO4, SiO2, K, Mg, Ca, Al)
Assessment of steam generator impurity deposition
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-19 Revision 4.1 Notes:
a)
Normal value is determined by the site-specific chemistry control program.
Table 10.3-3b: Feedwater Sample (Reactor Coolant System > 200°F to <15% reactor power)
Control Parameters Normal Value pH agent (a)
Dissolved oxygen, ppb 200°F < RCS 350°F 100 RCS >350°F, Reactor-not-critical 10 Reactor critical at <15% Reactor power 5
Hydrazine, ppb 8 x condensate pump discharge (CPD)(O2), 50 Suspended solids, ppb 200°F < RCS 350°F 100 RCS >350°F and <15% power 10 Silica, ppb (Reactor Critical) 10 Diagnostic Parameters Analysis Basis pH at 25°C Minimize system corrosion Sodium, ppb Minimize contaminant transport to the steam generators Sulfate, ppb Minimize contaminant transport to the steam generators Chloride, ppb Minimize contaminant transport to the steam generators Cation conductivity, S/cm at 25°C Minimize contaminant transport to the steam generators
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-20 Revision 4.1 Notes:
a)
Normal value is determined by the site-specific chemistry control program.
Table 10.3-3c: Feedwater Sample (15% reactor power)
Control Parameters Normal Value pH Agent (a)
Hydrazine, ppb 8 x CPD O2, 20 ppb Dissolved oxygen, ppb 5
Sodium, ppb 1
Chloride, ppb 3
Sulfate, ppb 1
Silica, ppb 10 Total iron, ppb 5
Diagnostic Parameters Analysis Basis Specific conductivity, S/cm at 25°C Consistent with pH amine concentration Cation conductivity, S/cm at 25°C Monitor increase in anion concentration Fluoride, ppb Contribution to cation conductivity Copper, ppb Baseline analysis Lead, ppb Impact on Alloy 690 corrosion Reducible metal oxides, ppb Corrosion product impact on SG tubing Integrated corrosion product transport Assessment of corrosion product transport to the SG
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-21 Revision 4.1 Notes:
a)
Measured at the condensate polisher effluent Table 10.3-3d: Condensate Sample ( 15% reactor power)
Control/Diagnostic Parameters Normal Value Dissolved O2, ppb 10a
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-22 Revision 4.1 Notes:
a)
Deoxygenated condensate is typically used to fill the steam generators following shutdown, feed and bleed operations, or refill operations occurring while the condensate and feedwater system is connected to the module. An alternate source of fill water that is oxygenated may be used to fill the steam generators if actions are taken to minimize oxygen exposure to the SG tubes. These actions may include nitrogen sparging or the treatment of the fill water with an approved oxygen scavenger (e.g., hydrazine). The oxygen scavenger may be added to the fill water or directly to the SG using batch additions prior to recirculation.
b)
This value may be determined by calculation or measurement.
Table 10.3-3e: Steam Generator Fill Water (initial fill subsequent to a shutdown)
Control Parameter Normal Value Frequency Hydrazine (ppm)(a)
>3 times fill water oxygen (ppm)(b)
Prior to or during the fill
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-23 Revision 4.1 Table 10.3-4: Main Steam System Instrumentation Equipment Name Monitored Parameter Local Display Signal To MCS MSS radiation transmitters Radiation Yes Yes Secondary MSIV limit switches Valve position, open No Yes Secondary MSIV limit switches Valve position, percent No Yes Secondary MSIV limit switches Valve position, closed No Yes Secondary MSIV bypass valve limit switches Valve position, open No Yes Secondary MSIV bypass valve limit switches Valve position, percent No Yes Secondary MSIV bypass valve limit switches Valve position, closed No Yes Secondary MSIV bypass isolation valve limit switches Valve position, open No Yes Secondary MSIV bypass isolation valve limit switches Valve position, closed No Yes N2 valve limit switches Valve fully open No Yes N2 valve limit switches Valve fully closed No Yes MSS pressure transmitters Pressure Yes Yes MSS flow transmitters Mass flow rate Yes Yes MSS pressure gauges MSS pressure Yes No MSS thermal elements MSS temperature NA Yes Vent valve limit switch Valve fully open No Yes Vent valve limit switch Valve fully closed No Yes Auxiliary steam supply valve position transmitter Valve position, percent No Yes Auxiliary steam flow transmitters Mass flow rate Yes Yes Auxiliary steam pressure gauge Pressure Yes No Auxiliary steam thermal elements Temperature NA Yes Auxiliary steam warm-up valve position transmitter Valve position, percent No Yes Low pressure extraction steam pressure transmitter Pressure Yes Yes Low pressure extraction steam thermal element Temperature NA Yes Intermediate pressure extraction steam pressure transmitter Pressure Yes Yes Intermediate pressure extraction steam thermal element Temperature NA Yes High pressure extraction steam pressure transmitter Pressure Yes Yes High pressure extraction steam thermal element Temperature NA Yes Extraction steam check valve limit switches Valve fully open No Yes Extraction steam check valve limit switches Valve fully closed No Yes Extraction steam isolation valve limit switches Valve fully open No Yes Extraction steam isolation valve limit switches Valve fully closed No Yes Steam trap drip leg level transmitters Level No Yes Steam trap drip leg level switches Level No Yes
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-24 Revision 4.1 Steam trap drain valve limit switches Valve fully open No Yes Steam trap drain valve limit switches Valve fully closed No Yes FWS differential pressure transmitters SG inventory No Yes Table 10.3-4: Main Steam System Instrumentation (Continued)
Equipment Name Monitored Parameter Local Display Signal To MCS
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-25 Revision 4.1 Table 10.3-5: Power Conversion System Flow-Accelerated Corrosion Program Piping System Piping segment Condensate and Feedwater System Condenser to condensate pumps Condensate pumps to feedwater pumps Feedwater pumps to the connection on the module platform Main Steam System Secondary isolation valve to turbine Turbine extraction lines to feedwater heaters Turbine Generator, Turbine Gland Sealing, and Turbine Bypass Systems Auxiliary steam to gland seals Feedwater to gland steam desuperheater Turbine bypass to condenser Feedwater to turbine bypass desuperheater Auxiliary Boiler System Low pressure boiler to turbine building users High pressure boiler to module heatup system heat exchangers Auxiliary boiler to condenser deaerator
NuScale Final Safety Analysis Report Main Steam System Tier 2 10.3-26 Revision 4.1 Figure 10.3-1: Main Steam System Piping and Instrumentation Diagram Turbine To HP Feedwater Heater MSS TGS Turbine Stop Valve MSSVs (2)
To Sampling ABS MSS From Steam Generator #2 From Steam Generator #1 TE PI To IP Feedwater Heater To LP Feedwater Heater TE PI TE PI PI TE FI Turbine Building Reactor Building FI TE PI From Nitrogen Distribution System To Sampling RE Secondary Main Steam Isolation Valves MSS CNTS Turbine Control Valve MSS TGS NOTES:
1.
VENTS AND DRAINS NOT SHOWN.
2.
STEAM TRAPS NOT SHOWN.
3.
MSS SUPPLIES GLAND STEAM VIA ABS HEADER.
4.
FOR SIMPLICITY, A SINGLE INSTRUMENT OF EACH TYPE IS SHOWN IN EACH LOCATION.
OUTLET OF MSIV/MSIBV SEISMIC 1, ASME SECTION III CLASS 1, QUALITY GROUP A SEISMIC 1, ASME B31.1 QUALITY GROUP D SEISMIC 3, ASME B31.1, QUALITY GROUP D FIRST SEISMIC ANCHOR SEISMIC 1, ASME B31.1, QUALITY GROUP D TO DHR SYSTEM CNT VESSEL NOZZLE MAIN STEAM ISOLATION VALVE SEISMIC 1, ASME SECTION III CLASS 2, QUALITY GROUP B Auxiliary Steam Header
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-1 Revision 4.1 10.4 Other Features of Steam and Power Conversion System 10.4.1 Main Condenser Each NuScale Power Module (NPM) has a main condenser (MC), which is part of the condensate and feedwater system described in Section 10.4.7. Each MC functions to condense and deaerate the exhaust from the main turbine and the turbine bypass system (TBS).
10.4.1.1 Design Basis This section identifies the MC required or credited functions, the regulatory requirements that govern the performance of those functions, and the controlling parameters and associated values that ensure that the functions are fulfilled. Together, this information represents the design bases, defined in 10 CFR 50.2, as required by 10 CFR 52.47(a) and (a)(3)(ii).
The MC serves no safety-related functions, is not credited for mitigation of a design basis accident (DBA), and has no safe shutdown functions. General Design Criteria (GDC) 2, 3, 4, and 5 were considered in the design of the MC. No safety-related structures, systems, and components (SSC) are affected by the effects of natural phenomena such as earthquakes. The design of the MC protects SSC from the effects of fire and explosion, and minimizes the probability of fire and explosion. The design of the MC provides protection of safety-related SSC from the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents. The components in the MC are not shared among NPMs; therefore, the MC does not impair the ability of other NPMs to perform their safety functions. See Section 10.4.1.3 for the MC safety evaluation.
Consistent with GDC 60, the design of the MC ensures the capability to control releases of radioactive materials to the environment. Consistent with 10 CFR 20.1101(b), the MC design supports keeping radiation exposures as low as reasonably achievable (ALARA).
The MC is designed to meet the requirements of 10 CFR 20.1406 as it relates to minimization of contamination of the facility.
10.4.1.2
System Description
10.4.1.2.1 General Description The MC is part of the condensate and feedwater system (CFWS), which is described in Section 10.4.7. A simplified diagram of the condenser is shown in Figure 10.4-1.
The MC includes all components and equipment from the turbine exhaust to the connections and interfaces with the CFWS and other systems such as turbine bypass, feedwater heater vents and drains, and gland sealing steam spillover and drains. The main condenser design data are provided in Table 10.4-1.
The primary functions of the MC are to:
condense exhaust steam from the turbine exhaust using circulating water provide a heat sink for the turbine bypass system
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-2 Revision 4.1 The MC components include:
condenser deaerator instrumentation hotwell inlet and outlet connections The MC is designed to deaerate the condensate. The condenser air removal system (CARS) removes the dissolved oxygen as well as other non-condensable gases as described in Section 10.4.2.
10.4.1.2.2 System Operation For system startup, the CARS is used to establish vacuum in the condenser. Steam from the auxiliary steam header is used to deaerate the condensate water. The auxiliary steam header is supplied steam from either the auxiliary boiler system (ABS) or from the main steam system (MSS). The deaerated condensate is routed through the condensate polishers to adjust CFWS water chemistry within limits, then to a spray line in the condenser to facilitate cleaning of the condenser hotwell.
During normal power operation, exhaust steam from the turbine is directed into the MC where the steam is expanded, condensed, and collected in the MC hotwell.
The MC also receives auxiliary system flows, such as turbine bypass, feedwater heater vents and drains, and gland sealing steam spillover and drains. The condenser hotwell receives primary makeup from the condensate storage tank (CST). The condensate pumps transfer the condensate from the hotwell to the condensate polishing system.
The MC operates under a vacuum that is maintained by the CARS. Non-condensable gases and air inleakage are collected in the MC and removed by the CARS to control contaminants and maintain the secondary water chemistry within an acceptable range as described in Section 10.3.5. The system has sampling lines provided to monitor for radioactivity and water chemistry as described in Section 9.3.2.
For off-normal operations, the condenser hotwell provides excess capacity. The MC hotwell is designed to store extra full-load condensate system operating flow during normal operation. In addition, the hotwell has a standby surge storage capacity. See additional information in Table 10.4-1.
During anticipated operational occurrences (AOOs), the MC is capable of accepting full-load steam flow from the TBS in conjunction with residual turbine exhaust while maintaining a vacuum. Operation of the TBS is discussed in Section 10.4.4. To protect the MC from superheated steam from the turbine bypass, a desuperheater is installed that is capable of cooling the 100 percent turbine bypass flow of superheated steam to saturated conditions. Additionally, the main condenser contains a bypass steam distribution header that guides the bypass steam away
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-3 Revision 4.1 from the tubes and a baffle plate that shields the condenser tubes from high-pressure steam impingement coming from the bypass distribution header.
The combination of these features allows the condenser to receive bypass steam indefinitely without damage to the condenser tubes or internal components.
Air leakage is monitored and minimized to maintain acceptable water chemistry.
Continuous deaeration is performed. The CARS discharge is also monitored to detect radiation in the system. In the unlikely event of a primary-to-secondary side leak due to a steam generator tube failure (SGTF), it is possible for the steam and the resulting condensate to become contaminated. In the event of an SGTF, the MSS and CFWS provide secondary isolation capabilities to minimize contamination.
Several methods are used to detect, control, and facilitate correction of leakage of cooling water into the condensate. The condenser is constructed of materials expected to prevent inleakage, and the module control system (MCS) is used to monitor the CFWS for inleakage. The permitted inleakage rate based on the capacity of the condensate polishing system (CPS) is specified in Table 10.4-13.
To monitor for circulating water ingress, cation conductivity is measured in a number of locations in the hotwell and in the condensate lines with in-line samples.
Condensate water egress to the environment is monitored by radiation monitors on the balance-of-plant drain system (BPDS), providing a positive means of ensuring that inadvertent radioactive discharges to the environment do not occur.
The MC hotwell has water level control that provides automatic makeup or rejection of condensate water to maintain water levels within the normal operating ranges. On low water level, the makeup control valves automatically open and condensate water is gravity fed to the hotwell from the CST. On high water level the condensate reject control valves automatically open to divert water from the condensate pump discharge to the CST. Makeup and overflow needs are provided on a normal basis, with redundant emergency makeup and overflow provisions for rapid condensate level requirements during abnormal situations. The condensate storage tank is further discussed in Section 10.4.7.
The MC tubes and tubesheet overlay are constructed of materials to help prevent corrosion and erosion, compatible with the chemistry requirements for the feedwater treatment system (FWTS) and CPS. Other methods used to reduce the corrosion and erosion of MC tubes and components include:
chemical treatment of the circulating water system as addressed in Section 10.4.5 use of main condenser tube cleaning as described below control of secondary side water chemistry as described in Section 10.3.5 The condensers have two separate tube bundles with separate inlet and outlet connections for circulating water. This allows for potential inservice maintenance of the tubes (plugging or cleaning) at reduced operating power. Provision is made
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-4 Revision 4.1 for the addition of a condenser tube cleaning system to mechanically scrub the circulating water side of the main condenser tubes. The circulating water chemical treatment may need the assistance of site-specific mechanical tube cleaning to reduce deposits and maintain condenser thermal efficiency. Adequate space is provided for pulling tubes in the condenser.
Discussion of the MC design features to protect against contamination is provided in Section 12.3.
10.4.1.3 Safety Evaluation The MC serves no safety-related functions, is not credited for mitigation of a DBA, and has no safe shutdown functions. General Design Criterion 2 was considered in the design of the MC. No safety-related structures, systems, or components are affected by this system from the effects of natural phenomena such as earthquakes. The design and layout of the MC include provisions that ensure that a failure of the system will not adversely affect the functional performance of safety-related systems or components.
The MC meets RG 1.29 in that it is not located in areas that contain safety-related components and is not required to operate during or after an accident. The MC is non-seismic, Seismic Category III.
General Design Criterion 3 was considered in the design of the MC. The design of the MC protects SSC from the effects of fire and explosion, and minimizes the probability of fire and explosion. The MC has no hydrogen buildup. A negligible amount of dissolved oxygen is present in the condensate and MC hotwell inventory in comparison to the amount of gas and vapor being evacuated by the CARS. There is no potential for explosive mixtures within the MC. The fire protection program is described in Section 9.5.1.
General Design Criterion 4 was considered in the design of the MC. The design of the MC provides protection of safety-related SSC from the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents. A failure of the MC hotwell that releases the water inventory and the resulting flooding does not prevent the operation of a safety-related system because no such systems are located in the Turbine Generator Buildings (TGBs). The flooding evaluation is addressed in Section 3.4.
General Design Criterion 5 was considered in the design of the MC. The components in the MC are not shared among NPMs; therefore, the MC does not impair the ability of other NPMs to perform their safety functions. Redundant radiation monitors are located on each of the two steam lines upstream of the secondary main steam isolation valves as described in Section 11.5.2. If a high radiation condition is detected on the main steam line radiation monitors (see Table 10.3-2 and Table 10.3-4), an alarm in the main control room will cue the operators to take actions to mitigate the event per applicable operating procedures. The Condenser Air Removal System also includes a monitor on the gaseous effluent discharge line as described in Section 11.5.2 which actuates an alarm in the main control room when the high and high high set points are reached. (see Table 12.3-33). Operator action will include monitoring steam generator information to determine if a steam generator tube leak or break has occurred. Actions
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-5 Revision 4.1 may include shutting down the NuScale Power Module and isolating the main steam line for a leaking steam generator.
General Design Criterion 60 was considered in the design of the MC. The MC design satisfies GDC 60 with regard to control of radioactive material releases to the environment. The MC is anticipated to contain negligible quantities of radioactive contaminants during power operation and during shutdown. To control the releases of radioactive contaminants, the air and non-condensable gases in the condenser are removed by the condenser air removal system. There is no buildup of non-condensable gases in the MC during normal operations because the liquid ring vacuum pump operates continuously during operation of the MC. The CARS has process radiation monitors on the gaseous effluent lines that discharge to atmosphere capable of detecting radioactivity in the gaseous effluent. Primary-to-secondary leakage contamination and the radiological monitoring instrumentation are addressed in Section 11.5. Leakage from the hotwell is collected and retained by a leakage detection system.
Leakage from the condenser hotwell will flow into the BPDS via the turbine building floor drains as described in Section 9.3.3 and as shown on Figure 9.3.3-2. The BPDS drain tanks, located adjacent to each turbine building are equipped with radiation monitors to determine if contamination is present as described in Section 9.3.3. A high-level detection shuts down the sump pumps and alarms in the main control room.
Operations will then investigate and can reroute the discharge to the liquid radwaste system if the contamination is too high for offsite discharge. Once the source of contamination is determined and corrected, the BPDS sump discharge will be returned to the normal offsite discharge alignment.
Collection of condensate from a condenser hotwell leak is performed by the BPDS as described in Section 10.4.1.2.2, and is not connected to the Condensate and Feedwater system. However, frequent operation of the makeup water valves between the condensate storage tank and the hotwell, a monitored parameter, will provide indirect indication of a leak.
There is no potential for explosive mixtures within the MC that would result in the release of radioactivity above the regulatory limits. Therefore, the MC design satisfies GDC 60 and is not required to be designed to withstand the effects of an explosion. The fire hazards analysis for the MC and component area is described in Section 9.5.1.
Consistent with 10 CFR 20.1101(b), the MC design supports keeping radiation exposures ALARA. To maintain the radiation exposure to operating and maintenance personnel ALARA, the MC is designed to facilitate maintenance, inspection, and testing in accordance with the guidance in Regulatory Guide (RG) 8.8.
The MC design satisfies the requirements of 10 CFR 20.1406 as it relates to minimization of contamination of the facility and such that the release of radioactive materials is ALARA. The CARS monitors the removed gases for radioactivity and can be isolated. The steam source can isolate upon loss of condenser vacuum. Further discussion of the facility design features to protect against contamination is provided in Section 12.3.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-6 Revision 4.1 10.4.1.4 Inspection and Testing The MC components are inspected and tested as part of the initial testing and startup program as described in Section 14.2.
Inspections, tests, analyses, and acceptance criteria (ITAAC) are addressed in Section 14.3.
10.4.1.5 Instrumentation The hotwell is equipped with level control devices for control of automatic makeup and rejection of condensate. Water level in the hotwell is indicated in the main control room (MCR) and alarms on high-water level or low-water level.
The MC pressure is indicated in the MCR and alarms on high level. Also, pressure instrumentation is provided to alarm prior to reaching the maximum turbine operating backpressure limit. Pressure devices are provided to trip the turbine on high-turbine exhaust pressure. Conductivity sensors are installed to detect high conductivity.
Temperature sensors are provided for monitoring MC performance. MC instrumentation is listed in Table 10.4-2.
10.4.2 Condenser Air Removal System Each NPM has a condenser air removal system designed to establish and maintain main condenser vacuum, and to monitor for radioactive material.
10.4.2.1 Design Bases This section identifies the CARS required or credited functions, the regulatory requirements that govern the performance of those functions, and the controlling parameters and associated values that ensure that the functions are fulfilled. Together, this information represents the design bases, defined in 10 CFR 50.2, as required by 10 CFR 52.47(a) and (a)(3)(ii).
The CARS serves no safety-related functions, is not credited for mitigation of a design basis accident, and has no safe shutdown functions. GDC 2, 3, 4, and 5 were considered in the design of the CARS. No safety-related SSC are affected by the effects of natural phenomena such as earthquakes. The design of the CARS protects SSC from the effects of fire and explosion, and minimizes the probability of fire and explosion. The design of the CARS provides protection of safety-related SSC from the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents. The components in the CARS are not shared among NPMs; therefore, failure of the CARS does not impair the ability of other NPMs to perform their safety functions.
Consistent with GDC 60, the design of the CARS ensures the capability to control releases of radioactive materials to the environment. Consistent with GDC 64, the CARS design provides radioactive effluent monitoring in potential discharge pathways to the environment and is designed to meet the requirements of 10 CFR 20.1406 as it relates
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-7 Revision 4.1 to minimization of contamination of the facility. See Section 10.4.2.3 for the CARS safety evaluation.
10.4.2.2
System Description
10.4.2.2.1 General Description The condenser air removal system is used to remove air from the main condenser.
Each MC is provided with two 100 percent capacity condenser air removal systems in parallel. If one system is unavailable due to maintenance issues or lost during normal operation, the redundant system is started to prevent a loss of condenser vacuum.
The CARS primary functions are to:
remove air and non-condensable gases from the MC during plant startup, cooldown, and normal operation provide initial system vacuum for NPM startup maintain MC vacuum to support operation of the turbine at various turbine loads and during AOOs Components of the CARS include:
liquid ring vacuum pump heat exchanger seal water separator gaseous effluent discharge radiation monitor The condenser air removal system is located near each main condenser. The CARS design data are provided in Table 10.4-3 and a simplified functional arrangement is provided in Figure 10.4-2.
Systems interfacing with the CARS have isolation capabilities to reduce the potential for cross-contamination between systems.
The CARS materials are based on compatibility with temperature, pressure, and secondary loop water chemistry. The system piping complies with ASME B31.1 requirements.
The quality group for the CARS is Quality Group D as described in Section 3.2. The seismic category is Seismic Category III. Quality group and seismic category designations are in accordance with the guidance provided in RG 1.26 and RG 1.29.
In accordance with the guidance provided in RG 1.26, piping, components, and instruments that are Quality Group D correspond to non-nuclear safety piping that is not relied upon to perform a nuclear safety function.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-8 Revision 4.1 10.4.2.2.2 Component Description Liquid Ring Vacuum Pump The liquid ring vacuum pump (LRVP) removes gases and non-condensables from the MC and discharges the exhausted gases into the seal water separator. The LRVP is provided as part of a vendor skid and is designed based on Heat Exchanger Institute (HEI) performance standards (Reference 10.4-1).
Seal Water Heat Exchanger The process side of the seal water heat exchanger is supplied from the seal water separator tank. The seal water heat exchanger supplies cooled flow to the seal water connection on the LRVP. The seal water is cooled by site cooling water.
Seal Water Separator The seal water separator takes discharge from the LRVP and separates the water from the exhaust gases. The gases are monitored and vented directly to atmosphere. The seal water separator returns excess water to the MC when a high seal water tank level is detected. Initial fill of the seal water separator and liquid ring pumps is provided by the demineralized water system.
10.4.2.2.3 System Operation For system startup, both condenser air removal systems are used to pull the initial vacuum on an offline main condenser. Using the liquid ring vacuum pump from both CARS rapidly reduces the pressure in the MC. Once the MC has achieved the desired vacuum pressure, one LRVP is switched off.
During normal operation, only one CARS is operating. The primary flow path consists of piping from the MC to the LRVP. The LRVP continuously removes gases, including non-condensable gases from the MC, while maintaining a vacuum at the desired setpoint. The gases are exhausted through piping connected to the seal water separator tank, in which moisture and gases are separated. The separated moisture is recycled as seal water for the LRVP. The gases are routed through piping connected to a silencer and then exhausted to the atmosphere.
The MC vacuum conditions are monitored during normal operation. If the vacuum decreases below the setpoint, the LRVP on the second skid is started to maintain a vacuum in the MC. The connection of the MC to the vacuum pumps is controlled by valves at the inlet of each vacuum pump.
Level is maintained in the seal water separator tank by makeup from the demineralized water system or letdown back to the MC. Tank level and LRVP level are equalized when the equipment is not in operation. When the LRVP is started, seal water flow is initiated and tank level controlled to provide adequate seal water in the LRVP.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-9 Revision 4.1 The CARS is supplied with drains to the balance-of-plant drain system, which provides the capability during or after a contamination event to route liquid to the radioactive waste drain system. Before the air is exhausted, the radioactivity of the exhausted air is monitored. Instrumentation is provided for monitoring radiation levels at the discharge of the CARS by the radiation monitoring system as described in Section 11.5.
For system shutdown, the LRVP is stopped and the CARS is isolated from the MC.
Off-normal system operation is indicated by high system exhaust radiation or by degrading or lost condenser vacuum. Radiation indication is provided in the main control room. High level radiation may require NPM shutdown, including stopping the LRVP and closing the CARS isolation valves. The allowable radioactivity high-level alarm in the CARS exhaust is set in accordance with 10 CFR 50, Appendix I. Process effluent radiation monitoring and sampling is discussed in Section 11.5.
Degrading MC vacuum conditions initiate operator action to start the idle LRVP to augment or replace the original running pump as applicable. Loss of condenser vacuum is an anticipated operational occurrence discussed in Section 15.2.3.
10.4.2.3 Safety Evaluation The CARS serves no safety-related functions, is not credited for mitigation of a design basis accident, and has no safe shutdown functions. General Design Criterion 2 was considered in the design of the condenser air removal system. No safety-related structures, systems, or components are affected by this system from the effects of natural phenomena such as earthquakes. The design and layout of the CARS include provisions that ensure that a failure of the system will not adversely affect the functional performance of safety-related systems or components.
The CARS meets RG 1.29 in that it is not located in areas that contain safety-related components and is not required to operate during or after an accident. The CARS is Seismic Category III.
General Design Criterion 3 was considered in the design of the condenser air removal system. The design of the CARS protects SSC from the effects of fire and explosion, and minimizes the probability of fire and explosion. The condenser exhaust gas consists mainly of air and ammonia. Ammonia concentrations may be considered minimal since the source is from pH control of the condensate and feedwater system and from hydrazine reactions with oxygen in the CFWS. The source of the hydrazine is the feedwater treatment chemical skid. For a pressurized water reactor, no hydrogen buildup is anticipated and only trace amounts of oxygen are released in the condenser.
The amount of hydrogen and other potential explosive gases released in the condenser is negligible compared to the amount of air and steam being evacuated by the system. Therefore, the potential for explosive mixtures within the condenser air removal system does not exist. The fire protection program is described in Section 9.5.1.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-10 Revision 4.1 General Design Criterion 4 was considered in the design of the condenser air removal system. The design of the CARS provides protection of safety-related SSC from the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents. A failure of the CARS does not prevent the operation of a safety-related system because no safety-related systems are located in the TGB.
General Design Criterion 5 was considered in the design of the condenser air removal system. The components in the CARS are not shared among NPMs; therefore, failure of the CARS does not impair the ability of other NPMs to perform their safety functions.
General Design Criterion 60 was considered in the design of the condenser air removal system. Radiation monitoring equipment continuously monitors gaseous effluent with indication and high radiation alarms in the main control room. Isolation valves at the discharge of the seal water separator tank can be controlled from the main control room. A negligible amount of dissolved oxygen is present in the condensate and MC hotwell inventory in comparison to the amount of gas and vapor being evacuated by CARS. There is no potential for explosive mixtures within CARS that would result in the release of radioactivity above the regulatory limits. Therefore, the CARS design satisfies GDC 60 and is not required to be designed to withstand the effects of an explosion.
Design Criterion 64 was considered in the design of the condenser air removal system.
The CARS meets the requirements of GDC 64 for continuous monitoring for radioactivity in the effluent discharge. Instrumentation is provided at the discharge as described in Section 11.5. The non-condensable gases and vapor mixture discharged from the CARS normally contain negligible amounts of radioactivity during normal plant operation. However, it is possible for the discharged mixture to become contaminated in the event of primary-to-secondary system leakage, and provision is made to detect and isolate this flow and manually route it to BPDS.
Consistent with 10 CFR 20.1101(b), the MC design supports keeping radiation exposures ALARA. To maintain the radiation exposure to operating and maintenance personnel ALARA, the condenser air removal system is designed to facilitate maintenance, inspection, and testing in accordance with the guidance in RG 8.8.
The CARS design satisfies the requirements of 10 CFR 20.1406 as it relates to minimization of contamination of the facility. The CARS monitors the removed gases for radioactivity and transfers detected radioactive materials to the radwaste processing systems. Further discussion of the facility design features to protect against contamination is provided in Section 12.3.
Detected radioactive material at or above the limits established in 10 CFR 50, Appendix I is isolated in the CARS. The CARS normally drains to the condenser, but includes manually operated valves that allow contaminated fluids to be routed to the balance-of-plant drain system, which can then be routed to the liquid radioactive waste drain system for appropriate processing during or after a contamination event.
The CARS has redundant components to ensure that a single component failure does not lead to a loss of condenser vacuum and a subsequent turbine trip. A failure of the CARS does not impact the safe operation of the NPM nor affect safety-related equipment. The CARS has no direct impact on the primary system or the secondary
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-11 Revision 4.1 systems. A failure of the CARS results in a slow increase in MC pressure. The loss of MC vacuum trip setpoint is designed so that a turbine trip is initiated before a reactor trip.
The loss of MC vacuum condition is described in Section 15.2.3.
10.4.2.4 Inspection and Testing The CARS and its components are inspected and tested as part of the initial testing and startup program as described in Section 14.2. Plant startup testing and inspection is performed prior to plant operation. The CARS design provides for on-line testing to determine the amount of exhaust flow and monitor MC performance and leakage rates. Flow measuring instrumentation is provided to determine the exhaust flow from the NPM.
The ITAAC are addressed in Section 14.3.
10.4.2.5 Instrumentation The following instrumentation and controls are provided to monitor and control the system and components of the CARS. Details are shown in Table 10.4-4.
Temperature monitors are provided for the seal water loop at the inlet side of the LRVP to maintain the temperature below the MC temperature.
Pressure monitors are provided at the suction of the LRVP with differential pressure provided at the flow control valve.
The seal water separator tank is provided with level monitoring and level control for tank makeup and letdown. This controls the water for the seal in the LRVP as well.
A flow gauge is attached to the separator tank for manual measurement of the LRVP exhaust flow. It is used to quantify inleakage and gas, including non-condensable gas removed from the MC.
Indication is provided at the supply breaker and at the main control room for the LRVP for pump on or off verification.
10.4.3 Turbine Gland Sealing System The turbine gland sealing system (TGSS) is part of the turbine generator system (TGS) described in Section 10.2 and is shown on Figure 10.2-1. The primary function of the TGSS is to prevent air leakage into the turbine under vacuum and prevent steam leakage out of the turbine under pressure during load conditions.
10.4.3.1 Design Bases This section identifies the TGSS required or credited functions, the regulatory requirements that govern the performance of those functions, and the controlling parameters and associated values that ensure that the functions are fulfilled. Together, this information represents the design bases, as defined in 10 CFR 50.2, as required by 10 CFR 52.47(a) and (a)(3)(ii).
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-12 Revision 4.1 The TGSS is part of the TGS, serves no safety-related function, is not credited for mitigation of a DBA, and has no safe shutdown functions. See Section 10.2 for the discussion on how General Design Criteria 2, 4 and 5 were considered in the design of the TGS.
Consistent with GDC 60, the design of the TGSS ensures the capability to control releases of radioactive materials to the environment. Consistent with GDC 64, the TGSS design provides radioactive effluent monitoring in potential discharge pathways to the environment and is designed to meet the requirements of 10 CFR 20.1406 as it relates to minimization of contamination of the facility. See Section 10.4.3.3 for the TGSS safety evaluation.
10.4.3.2
System Description
10.4.3.2.1 General Description The TGSS performs the following functions:
prevents air leakage into the turbine under vacuum prevents steam leakage out of the turbine under pressure provides for the use of redundant steam supplies and controlling devices The TGSS is part of the TGS, and consists of the following components:
gland steam condenser two gland seal condenser exhauster blowers condenser drain hold tank desuperheater relief valves gland steam regulator The TGSS design details are provided in Table 10.4-5.
10.4.3.2.2 Component Description Gland Steam Condenser The gland steam condenser cools the gland steam using feedwater. It is equipped with high-point vents and a drain. Water level in the condenser is monitored.
Gland Seal Condenser Exhauster Blowers The gland seal condenser exhauster blowers maintain a partial vacuum in the gland steam condenser to prevent the entrainment of air in the gland steam condensate.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-13 Revision 4.1 Desuperheater The gland seal desuperheater uses feedwater to cool the steam fed to the TGSS to saturated conditions.
Relief Valves The relief valves provide overpressure protection to the TGSS.
Gland Steam Regulator The gland steam regulator maintains seal steam pressure.
10.4.3.2.3 System Operation The gland seal steam prevents the escape of steam from the turbine shaft and casing penetrations and the glands of large turbine valves. Sealing steam is distributed to the turbine shaft seals through the steam-seal header. This sealing steam is supplied from either the auxiliary boiler system or from the main steam system extracted ahead of the turbine control valves. Steam flow to the header is controlled by the steam-seal feed valve, which responds to maintain the steam-seal supply header pressure. The gland seal desuperheater uses feedwater to cool the steam fed to the TGSS to saturated conditions.
During plant startup, the ABS provides steam until sufficient steam flow is available from the MSS. The TGSS steam pressure is automatically maintained by pressure-regulating valves provided in both the MSS and auxiliary steam system supply piping. Excess steam is returned to the gland steam condenser through the spillover control valve, which automatically opens to bypass excess steam from the TGSS. Automatic and manual controls are provided to regulate gland steam pressure and temperature.
At the outer ends of the turbine glands, collection piping routes the mixture of air and excess seal steam to the gland steam condenser. The gland steam condenser internal pressure is maintained at a slight vacuum by motor driven blowers.
Condensate from the steam-air mixture drains to the MC while non-condensables are exhausted to the vents, drains, and relief system through a common discharge line shared by the vapor extractor blowers.
The mixture of non-condensable gases discharged from the gland steam condenser blower is not normally radioactive; however, in the event of primary-to-secondary system leakage due to an SGTF, it is possible to discharge radioactively contaminated gases. The TGSS effluents are monitored by a radiation monitor and grab sample point located on the exhaust line to the gland seal steam vent.
10.4.3.3 Safety Evaluation The turbine gland sealing system is part of the turbine generator system and has no safety-related functions, is not credited for mitigation of a DBA, and has no safe
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-14 Revision 4.1 shutdown functions. General Design Criterion 60 and 64 were considered in the design of the turbine gland sealing system. The TGSS design satisfies GDC 60 with regard to control of radioactive material releases to the environment and GDC 64 with regard to monitoring radioactive releases, and is designed to meet the requirements of 10 CFR 20.1406 as it relates to minimizing contamination of the facility. The TGSS is anticipated to contain negligible quantities of radioactive contaminants. However, in the event of primary-to-secondary system leakage due to a SGTF, the leakage can be isolated. The TGSS effluent duct is equipped with a radiation monitor and provision for grab sampling. The radiation monitor alarms at high and high-high levels in the MCR and the gland seal exhaust has remote manual isolation capabilities.
10.4.3.4 Inspection and Testing The TGSS is inspected and tested prior to plant operation as described in Section 14.2.
The ITAAC are addressed in Section 14.3.
10.4.3.5 Instrumentation Instrumentation is detailed in Table 10.4-6. Gland seal pressure is monitored and a pressure controller is provided to maintain the steam-seal supply header pressure by providing signals to the steam-seal supply valve. Control valves are used to regulate the appropriate pressure to the turbine glands.
10.4.4 Turbine Bypass System The turbine bypass system is provided as part of the turbine generator system described in Section 10.2 and is shown on Figure 10.2-1. The TBS provides main steam directly from the steam generators to the main condenser in a controlled manner to remove heat from the NPM following a reduction or loss of electrical load.
10.4.4.1 Design Bases This section identifies the TBS required or credited functions, the regulatory requirements that govern the performance of those functions, and the controlling parameters and associated values that ensure that the functions are fulfilled. Together, this information represents the design bases, as defined in 10 CFR 50.2, as required by 10 CFR 52.47(a) and (a)(3)(ii).
The TBS serves no safety-related function is not credited for mitigation of a DBA, and has no safe shutdown functions. It is part of the TGS discussed in Section 10.2. See Section 10.2 for discussion of GDC 2, 4, and 5 and additional design bases.
Although not credited for compliance with PDC 34, the TBS can be used to provide a residual heat removal function for normal NPM shutdown, eliminating the need to rely solely on safety systems or components. The decay and residual heat removal safety function per PDC 34 is performed by the decay heat removal flowpath and the containment isolation function of the containment system, that is, the main steam isolation valves (MSIVs) and the feedwater isolation valves. Conformance with PDC 34 is further discussed in Section 5.4.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-15 Revision 4.1 The TBS is designed to transfer steam to the condenser, bypassing the turbine, bypass steam automatically as needed, bypass steam for load rejection without additional release mechanisms, bypass steam to accommodate step-load changes at the required speeds, and provide NPM cooldown by steam bypass.
The TBS has the capacity to bypass the rated power steam flow to the MC at full power operation. The TBS total flow capacity, in combination with bypass valve opening time, pressurizer (PZR) size, and the reactor power control system is sufficient to sustain a rated power normal load rejection (electrical load), without generating a reactor trip, and without requiring actuation of the main steam safety valve.
The NPM design is capable of step load changes from steady state conditions, as described in Section 10.2.2, dumping the steam from the main steam header directly to the condenser. The turbine bypass valve is automatically controlled to protect the reactor during turbine load transients or loss of electrical load. For these load rejections, the TBS operates in conjunction with the control systems used for the load change to meet the design basis requirements without generating a reactor trip.
10.4.4.2
System Description
10.4.4.2.1 General Description The TBS is part of the turbine generator system described in Section 10.2 and is shown on Figure 10.1-1.
Turbine bypass components include:
turbine bypass valve turbine bypass desuperheater The TBS consists of a line connected to the main steam combined header, downstream of the MSIVs and upstream of the turbine stop valve, with a regulating valve and an inline desuperheater discharging to an MC.
For load rejections, the TBS operates in conjunction with the control systems used for the load change to meet the design basis requirements without generating a reactor trip.
Quality group standards and seismic design information for the TBS are provided in Section 3.2.
10.4.4.2.2 Component Description Table 10.4-7 provides the TBS component details.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-16 Revision 4.1 Turbine Bypass Valve The turbine bypass valve dumps steam from the main steam header, through the desuperheater to the condenser. It is located near the turbine and is capable of throttling the full bypass flow from the turbine to the condenser.
Desuperheater The desuperheater is downstream of the turbine bypass valve to reduce the steam temperature because highly superheated steam directly entering the condenser could damage the condenser tubes. The desuperheater cooling water is directly injected into the bypassed steam from the CFWS.
10.4.4.2.3 System Operation For NPM startup, the turbine bypass valve is open. The turbine bypass valve is used to control the steam generator (SG) pressure, which determines the highest achievable primary side temperature during heatup operations. The bypass valve pressure setpoint is adjusted during startup to control steam flow as required.
Operation during power descent is the reverse of power ascent. Decay heat and sensible heat is removed by the TBS to cool the plant and bring it to safe shutdown.
During normal operation, the TBS is not used.
The TBS is designed to reduce the possibility of reactor transients during off-normal operation. A turbine or generator trip causes the turbine stop valve to quickly isolate, causing an increase in steam pressure. The bypass valve then opens either on an anticipatory signal or on high steam line pressure. While the bypass line and MC are sized for bypass flow to prevent a reactor trip, continuous operation with high bypass flow is not desirable. Depending on the cause of the event and expected time to return to normal operation, the NPM can either be shut down or remain operating on bypass flow at full or reduced power.
A loss of circulating water flow or condenser vacuum triggers the control system to block opening the bypass valves and can trip the reactor.
An unintentional opening of the turbine bypass valve could cause an overcooling event and an increase in reactor power. Refer to Section 15.1.3 for more information.
10.4.4.3 Safety Evaluation The TBS has no safety-related function, is not credited for mitigation of a DBA, and has no safe shutdown functions. The TBS is part of the TGS. Refer to Section 10.2 for discussion concerning GDC 2, 4, and 5.
Compliance of the turbine bypass system with BTP 3-3 and BTP 3-4 is discussed in Section 3.6.1. A discussion of the effects of the TBS equipment malfunctions on the reactor coolant system (RCS) is provided in Section 15.1.3.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-17 Revision 4.1 Principal Design Criterion 34 was considered in the design of the turbine bypass system. Although not credited for PDC 34 compliance, the TBS can be used to provide a residual heat removal function for normal NPM shutdown, eliminating the need to rely solely on safety systems or components. The requirements of PDC 34 are performed by the decay heat removal flowpath and the containment isolation function of the containment system. Conformance to PDC 34 is further discussed in Section 5.4. The turbine bypass system design supports the intent of PDC 34 as it can provide a residual heat removal function for NPM shutdown, eliminating the need to rely solely on safety systems or components. The TBS can be used cool the NPM to safe shutdown heat levels. The TBS design also satisfies the requirements of 10 CFR 20.1406 as it relates to minimization of contamination of the facility.
10.4.4.4 Inspection and Testing Before the TBS is initially placed in service, the turbine bypass valve is tested as described in Section 14.2 to verify proper function. The TBS piping and valves are accessible for inspection. Inservice inspection or testing is not required except for the turbine bypass valve, which is included in the inservice inspection program.
The ITAAC are addressed in Section 14.3.
10.4.4.5 Instrumentation and Control Table 10.4-8 lists the instrumentation used to control the TBS. Pressure and valve position indications are also provided in the MCR.
The module protection system and module control system are used to control flow rate for warming of the MSS lines and establishing steam flow during startup. The bypass valve can divert main steam during normal operation while maintaining the required load operational backpressure at the SG. The MCS logic provides the ability to bypass low RCS average temperature control in order that the turbine bypass valve can be used to cool down the plant. Interlocks block actuation of the turbine bypass valve on high condenser pressure (low vacuum) or on a circulating water system trip.
10.4.5 Circulating Water System The principal function of the circulating water system (CWS) is to provide cooling water to the main condensers. The CWS consists of two duplicate cooling water subsystems, each designed to deliver cooling water to six main condensers. A single subsystem is discussed unless otherwise noted.
10.4.5.1 Design Bases This section identifies the CWS required or credited functions, the regulatory requirements that govern the performance of those functions, and the controlling parameters and associated values that ensure the functions are fulfilled. Together, this information represents the design bases, defined in 10 CFR 50.2, as required by 10 CFR 52.47(a) and (a)(3)(ii).
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-18 Revision 4.1 The CWS serves no safety function, is not credited for mitigation of a DBA, and has no safe shutdown functions. General Design Criteria 2, 4, and 5 were considered in the design of the CWS. No safety-related SSC are affected by the effects of natural phenomena such as earthquakes. The design of the CWS provides protection of safety-related SSC from the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents.
There are no safety-related components in the CWS that are shared among NPMs; therefore, failure of the CWS does not impair the ability of other NPMs to perform their safety functions. See Section 10.4.5.3 for the CWS safety evaluation.
Consistent with GDC 60, the design of the CWS ensures the capability to control releases of radioactive materials to the environment. Consistent with 10 CFR 20.1101(b), the CWS design supports keeping radiation exposures ALARA.
Consistent with 10 CFR 20.1406, the CWS is designed to meet the requirements as it relates to minimization of contamination of the facility. Further discussion of the facility design features to protect against contamination is provided in Section 12.3.
The CWS design parameters are provided in Table 10.4-9.
10.4.5.2
System Description
10.4.5.2.1 General Description The CWS is a nonsafety-related system that provides a continuous supply of cooling water to the main condensers and rejects heat to the environment. The CWS is the normal heat sink for the NuScale Power Plant. For the 12-NPM design, the CWS is composed of two identical circulating water subsystems, each responsible for delivering cooling water to the main condensers of six condensate and feedwater systems. There is no interconnected piping between the two subsystems. The CWS is shown in Figure 10.4-3 and a list of systems that the CWS interfaces with is shown in Table 10.4-10.
The components of the CWS consist of:
three circulating water pumps three traveling screens (one per pump) chemical injection system mechanical draft cooling tower banks and basin cooling tower makeup and blowdown The CWS is a moderate energy fluid system. Design considerations based on the effects of failures of moderate energy fluid systems on safety-related systems are addressed in Section 3.6.
10.4.5.2.2 Component Description The CWS component design parameters are provided in Table 10.4-9.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-19 Revision 4.1 Circulating Water Pumps Three 33 percent capacity circulating water pumps take suction, through a traveling screen, from dedicated CWS pump bays that are connected directly to the cooling tower basin. The pump discharge lines supply circulating water to two headers. Each header is responsible for maintaining circulating water flow to the two water boxes in each of three condensers. Each pump discharge line has a valve located between the pump discharge and the common header to permit two-pump operation during pump maintenance. The alpha pump of each subsystem has a minimum flow valve that returns flow to the cooling tower basin.
This valve is used during system filling.
Traveling Screens Continuously moving traveling screens located at the entrance to each individual pump bay prevent debris from entering the CWS pump bay from the cooling tower basin water.
Cooling Tower The CWS uses a single cooling tower arrangement to reject heat to the atmosphere, consisting of mechanical, induced-draft, counterflow cooling tower cells. Each of the cells includes a motor-driven, mechanical-draft fan and isolation valve. Each tower is sized to support the full-power operation of up to six NPMs during the summer months with one tower segment (cell) not operating during cooler months. The number of cooling tower cells and the horsepower of each cell's fan is site-specific, dependent on the design ambient temperature.
The tower cells may be bypassed, partially bypassed, or fully utilized as needed depending on the desired configuration, heat load, and ambient conditions.
During cold weather operations, the CWS provides the capability to reverse cooling tower airflow.
The cooling tower basin serves for collection and storage of the circulating water inventory, and is sized to provide surplus inventory for several hours of extended operation without makeup.
The cooling towers are physically located so that their failure has no physical interaction with other plant structures.
Cooling Tower Makeup and Blowdown Makeup water to the cooling tower basin is supplied by the utility water system (Section 9.2.9). Automatic makeup to the cooling tower basin is actuated by water level instrumentation.
Makeup to and blowdown from the CWS is controlled by the makeup and blowdown throttling control valves. These valves, along with a chemical feed system, provide chemistry control in the CWS in order to maintain a noncorrosive, nonscale-forming condition and limit biological growth in CWS components. Five
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-20 Revision 4.1 cycles of concentration for fresh water has been designed for sizing the cooling tower makeup and blowdown rates. The cycles of concentration is site-specific, dependent on makeup water quality.
The site's single point discharge to the environment accepts the cooling tower blowdown, and is located to prevent recirculation to the makeup water intake.
Chemical Treatment The CWS chemistry is maintained by a chemical treatment system located adjacent to the cooling tower basin, which includes tanks, pumps, and associated piping and components to inject biocide, dispersant chemical, and scale inhibitor into the cooling tower basin to maintain acceptable chemistry.
The chemicals used are dependent upon site selection and subsequent water analyses. Site selection determines the restrictions on the discharge of biocide.
Connections to the process sampling system (PSS) (Section 9.3) are provided for grab samples to monitor total dissolved solids, pH, conductivity, and biocide effectiveness. Chemistry control is maintained manually during startup, and with automated injection in the cooling tower basin during operation, adjusted through feedback from chemical analyzers in the cooling tower basin and in the CWS blowdown line.
Piping and Valves The underground portions of the CWS piping are constructed of pre-stressed concrete-lined pipe designed to AWWA standards. The remainder is carbon steel designed to ASME B31.1. The CWS piping is designed to withstand the maximum operating discharge pressure of the circulating water pumps. Piping includes the expansion joints, valves, condenser water boxes, and tube bundles.
Valves are provided in each of the circulating water lines at the inlet to and exit from the condenser waterboxes to allow isolation of portions of the condenser.
Provision is made for the addition of a site-specific condenser tube cleaning system. Throttling control valves regulate cooling tower blowdown and makeup.
10.4.5.2.3 System Operation Startup is accomplished with valve lineup and single pump initiation, followed by venting and chemistry adjustment as needed.
After startup, the CWS is designed for continuous operation with minimal operator involvement. The system is designed such that one circulating water pump is in operation for every two operating main condensers.
Operating circulating water pumps take suction from dedicated pump intake bays and circulate the water through the tube side of six operating main condensers and then back through a piping network to the cooling tower. A mechanical forced-draft cooling tower, described above, cools the circulating water by
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-21 Revision 4.1 discharging the water over a network of baffles, called fill. The water then cascades through fill material to the basin beneath the tower and, in the process, rejects heat to the atmosphere primarily via evaporation.
During normal operation, when five or six main condensers are in operation, three circulating water pumps provide full-rated flow to each main condenser to maintain adequate condenser vacuum for turbine operation. The rated flow to each condenser is site-specific, dependent on the design ambient temperature.
The CWS flow to the cooling tower can be diverted directly to the tower basin, through a cooling tower bypass valve, bypassing cooling tower cells to maintain basin temperatures during cold weather operations.
Makeup water to replace water losses due to evaporation, wind drift, and blowdown is supplied by the utility water system.
The CWS chemistry is monitored routinely during operation and controlled by the chemical injection and blowdown systems. A portion of the CWS flow is continuously blown down and replenished with makeup water to maintain acceptable chemistry levels.
During plant shutdown as total system heat load is reduced, portions of the CWS may be removed from service by shutting down cooling tower cells, fans, and circulating water pumps.
The three circulating water pumps are manifolded together and feed into two distribution lines. Each distribution line feeds three main condensers. If one pump trips, the remaining two pumps increase flow on pump runout and can continue to support six condensers at 70 to 80 percent of normal CWS flow. If two pumps trip, the remaining pump increases flow on pump runout to only 40 percent of normal CWS flow. To maintain adequate condenser backpressure for turbine operation, the six NPMs reduce power. If the three circulating water pumps trip, condenser backpressure is lost and the six NPMs associated with that circulating water subsystem trip.
If the circulating water pumps, the cooling tower, or the circulating water piping malfunctions such that condenser backpressure rises above the maximum allowable value, the MC is no longer able to adequately support NPM operation.
Because each loop of the CWS is shared by six NPMs a malfunction within a loop affects the operational capability of the associated NPMs.
A trip of one of the six NPMs served by the circulating water subsystem does not affect the other five. The design requires one CWS pump for every two main condensers that are online to provide full flow.
To accommodate flooding due to rain or makeup valve malfunction, basin overflow is piped to the single point discharge to the environment.
The circulating water pumps are not required during a DBA.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-22 Revision 4.1 10.4.5.3 Safety Evaluation The CWS serves no safety function, is not credited for mitigation of a DBA, and has no safe shutdown functions.
General Design Criterion 2 was considered in the design of the circulating water system. No safety-related structures, systems, or components are affected by this system from the effects of natural phenomena such as earthquakes. The design and layout of the CWS include provisions that ensure that a failure of the system will not adversely affect the functional performance of safety-related systems or components.
The CWS system meets RG 1.29 in that the CWS is not located in areas that contain safety-related components and is not required to operate during or after an accident.
General Design Criterion 4 was considered in the design of the circulating water system. The design of the CWS provides protection of safety-related SSC from the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents.
The TGB does not contain safety-related equipment; thereby eliminating the possibility of damage as a result of CWS line break. Large CWS leaks due to pipe failures will be indicated in the control room by a loss of MC vacuum. MC vacuum is a parameter that is monitored during normal operation (Section 10.4.2.2.3). Water from a circulating water pipe or expansion joint leak would drain through the building doors and vent openings, and then away from other buildings as controlled by the site grading. The soil around the TGB and the cooling towers is sloped away from structures, thus a failure of the water basin of the cooling towers has no effect on other structures. The flooding evaluation is addressed in Section 3.4.
General Design Criterion 5 was considered in the design of the circulating water system. The sharing of the CWS across six NPMs does not impair the ability of the other NPMs to perform their safety functions. The use of common CWS equipment to accomplish the cooling of six or less condensers does not have a effect on system availability and operability as described in Section 10.4.5.2.3.
General Design Criterion 60 was considered in the design of the circulating water system. Consistent with GDC 60, the CWS design controls radioactive material releases to the environment. The CWS is anticipated to contain negligible quantities of radioactive contaminants during power operation and during shutdown. Blowdown from the circulating water system is sent to the utility water system site liquid effluent release point. The discharge from this release point is monitored for radioactivity before discharge to the environment. If high radiation is detected at the single point effluent discharge path to the environment, the radiation monitoring system for the UWS provides an alarm in the main control room and locally.
Consistent with 10 CFR 20.1101(b), the CWS design supports keeping radiation exposures ALARA. To maintain the radiation exposure to operating and maintenance personnel ALARA, the CWS is designed to facilitate maintenance, inspection, and testing in accordance with the guidance in RG 8.8.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-23 Revision 4.1 The CWS design satisfies 10 CFR 20.1406 requirements relating to minimization of contamination of the facility. Further discussion of the facility design features to protect against contamination is provided in Section 12.3.
The CWS provides cooling water to the tube side of the main condensers. In the event of a SG tube leak, radioactive fluid would infiltrate the secondary loop, which would be detected in the MSS. There would have to be a simultaneous failure of the SG tubes and MC tube leak for radiation to leak into the CWS. However, during normal operation the CWS is kept at higher pressure than the condenser shell side, which keeps the leakage into the condenser rather than to the environment. Grab sample locations are checked and blowdown is monitored for radiation.
10.4.5.4 Inspection and Testing Components of the CWS are accessible for inspection during plant operation or during NPM refueling.
Performance, hydrostatic, and leakage tests associated with pre-installation and preoperational testing are performed on the CWS as described in Section 14.2. The system performance, structural and leaktight integrity of system components are demonstrated by continuous operation.
A test coupon exposure rack is provided in the pump basin for monitoring material performance in the CWS.
A full-power performance test of the CWS is performed prior to initial full-power operation in accordance with ASME PTC 23 (Reference 10.4-2). Inservice inspection is performed of the CWS components as described in Chapter 13.
The ITAAC are addressed in Section 14.3.
10.4.5.5 Instrumentation System operating parameters are monitored locally and in the MCR as part of the MCS.
Main control room alarms are also provided. The operating parameters include cooling tower and pump sump water levels, temperature, pump pressure, and system flow.
Instrumentation details are provided in Table 10.4-11. Alarm details are listed in Table 10.4-12.
The motor-operated valve at each pump discharge is interlocked with the pump so that the pump trips if the discharge valve fails to reach the full-open position shortly after starting the pump. Water chemistry is manually adjusted during startup, and monitored routinely during operation with the PSS (Section 9.3). Automatic chemical injection is adjusted with instrumentation in the cooling tower basin and blowdown line. Appropriate PSS indications and alarms are provided in the MCR.
10.4.6 Condensate Polishing System The condensate polishing system is part of the condensate and feedwater system. The condensate polishing system treats and cleans the feedwater to remove corrosion
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-24 Revision 4.1 products and ionic impurities. The feedwater treatment system (Section 10.4.11), a separate part of the condensate and feedwater system, manages chemical addition for pH control and oxygen scavenging.
10.4.6.1 Design Basis The CPS serves no safety-related functions, is not credited for mitigation of a DBA, and has no safe shutdown functions. See Section 10.4.7 for discussion of GDC 2, 4, and 5.
Consistent with GDC 14, the design of the CPS provides the means to maintain acceptable secondary water chemistry as discussed in the EPRI report series, "PWR Secondary Water Chemistry Guidelines" (Reference 10.4-3) as discussed in Section 10.3.5. This supports the overall objective of maintaining the reactor coolant pressure boundary integrity with an extremely low probability of abnormal leakage, rapidly propagating failure, or gross rupture.
Consistent with GDC 60, the design of the CPS ensures the capability to control releases of radioactive materials to the environment. Consistent with 10 CFR 20.1101(b), the CPS design supports keeping radiation exposures ALARA. The CPS is designed to meet the requirements of 10 CFR 20.1406 as it relates to minimization of contamination of the facility.
The operating parameters for the CPS are listed in Table 10.4-13.
10.4.6.2
System Description
10.4.6.2.1 General Description The CPS is nonsafety related, is part of the CFWS, and is located in the TGB. The CPS removes corrosion products and ionic impurities from the CFWS system, provides adequate capacity to treat feedwater at plant startup, and provides adequate capacity for treatment during a condenser leak that may contaminate the CFWS system. The CPS is supported by the condensate polisher resin regeneration system, which restores resin quality to polisher requirements for reuse.
The CPS consists of two skids near the turbine: one condensate polishing skid and one rinse recycle pump skid.
The CPS includes the following major equipment:
two condensate inlet filters condensate polishers (mixed bed deionizers) resin filters spent resin tanks resin supply tank resin replacement equipment (valves, hoppers, controls, etc.)
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-25 Revision 4.1 The CPS is Quality Group D, ASME B31.1. The system is designed to Seismic Category III requirements. Input to the CPS equipment is received from downstream of the condensate pumps. Processed flow is returned to the gland steam condenser. A full flow bypass path is provided around the CPS.
The CPS maintains water quality to the parameters shown in Table 10.4-14, to avoid corrosion-induced failure of the reactor coolant pressure boundary. The system is designed to control flow through the condensate polishers to avoid hydraulic surges and additional hydraulic loads due to flow as discussed in Section 10.4.6.2.2.
The adequacy of the design to withstand breaks and cracks in high-energy and moderate-energy system piping is discussed in Section 3.6.1.
Corrosion, erosion, and flow-accelerated corrosion (FAC) resistant materials are used for components exposed to wet steam, flashing liquid flow, or turbulent single phase flow where loss of material could occur. The degree of corrosion, erosion, and FAC resistance of the material is consistent with specific conditions of the fluid stream involved. A corrosion allowance is included on the design of carbon steel CFWS piping.
The system is designed such that the condensate temperature at the condensate polishers does not exceed the design temperature limit of the resin during normal operation or planned transients.
The PSS and CFWS monitor the CFWS for dilution due to condenser cooling water leakage.
10.4.6.2.2 Component Description Condensate Filter Two 100 percent flow condensate filters are upstream of the condensate polishers.
They have rinse piping for manual cleaning based on the differential pressure indication.
Condensate Polishers Two 100 percent redundant condensate polisher trains are provided per NPM. The condensate polisher is a mixed bed deionizer. The polishing capacity meets the feedwater chemistry requirements as specified in Section 10.3.5. CPS components are mounted on the condensate polishing skid and the rinse recycle pump skid.
Connections are provided for resin transfer with the resin regeneration equipment, condensate rinse, compressed air, drainage to balance of plant drains, and sampling.
Resin Trap The resin trap is located downstream of the condensate polisher and collects resin fines that have escaped the polisher.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-26 Revision 4.1 Resin Filter The resin filter is located on the condensate polishing skid to filter out potential foreign materials. Plugging is monitored with pressure differential measurement.
Spent Resin Tanks The spent resin tank is used to store spent resin for shipment offsite.
Resin Supply Tank The resin supply tank is used to store new resin for use onsite.
COL Item 10.4-1:
A COL applicant that references the NuScale Power Plant design certification will determine the size and number of new and spent resin tanks in the condensate polishing system.
Resin Replacement Equipment The resin replacement equipment is automated to minimize operator involvement.
The system is designed to allow use at each CPS through temporary connections.
One condensate polisher regeneration system is provided to service up to six CPS in each TGB.
Valves Ion exchanger isolation valves are designed to permit slow, controlled opening to minimize hydraulic surges on the resin bed, which could damage the resin.
10.4.6.2.3 System Operation The CPS cleans the CFWS water during startup to meet the secondary water chemistry specifications listed in Section 10.3.5. The water is recirculated between the MC hotwell and the CPS until the water quality is within the specifications. The FWTS (Section 10.4.11) manages chemical addition for pH control and oxygen scavenging. The remainder of the CFWS is described in Section 10.4.7.
During normal operation, the condensate pumps move 100 percent of the condensate flow from the hotwell through the CPS and into the gland steam condenser (Section 10.4.3). Several sampling points provide input to the PSS to monitor CPS performance. The CPS is capable of reducing anticipated impurity levels to the acceptable feedwater levels in Table 10.4-14.
Condensate polishing system bypass piping is provided.
The spent resin is removed from the polishers and replaced with new or regenerated resin. The replacement of resin is done with the polisher out of service.
The CPS uses demineralized water for transfer, flushing, and other resin regeneration processes. Spent resin is normally not radioactive. If primary-to-secondary leakage occurs, the CPS resin is transferred into a high
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-27 Revision 4.1 integrity container or another suitable container and transported to a storage area of the radioactive waste building for offsite disposal. No direct piping exists between the turbine building and radioactive waste building for this purpose. The resin replacement equipment is instrumented and valves can be remotely operated to allow automation of the entire process.
The Process Control Program (Section 11.4) governs the handling of spent resins and their removal from the site.
Condensate polisher regenerant waste is discharged to the BPDS where it is monitored for contamination. If radioactivity is detected above a predefined set point the regenerant waste is sent to the liquid radioactive waste system for treatment, else it is sent to the plant's single point of discharge to the environment.
The condensate polishers are expected to also be used in abnormal conditions such as MC tube leaks. This allows the plant to continue operation for a short time at full power before shutting down to repair the condenser tube leaks. The flow through the CPS is controlled by the condensate bypass valve.
Design features ensure that in the event of condenser tube leaks, concentrations of chloride and other contaminants are limited to allowable values until the CFWS is isolated.
10.4.6.3 Safety Evaluation The CPS serves no safety-related functions, is not credited for mitigation of a DBA, and has no safe shutdown functions.
The CPS functions to remove impurities and corrosion products to maintain water quality as specified in the Secondary Water Chemistry Program described in Section 10.3.5.
General Design Criterion 14 was considered in the design of the condensate polishing system. Consistent with GDC 14, the design of the CPS provides the means to maintain acceptable secondary water chemistry as discussed in the EPRI report series, "PWR Secondary Water Chemistry Guidelines." (Reference 10.4-3) as discussed in Section 10.3.5. This supports the overall requirements of GDC 14 of maintaining the reactor coolant pressure boundary integrity with an extremely low probability of abnormal leakage, rapidly propagating failure, or gross rupture. By controlling the water chemistry to avoid corrosion-induced failure of the reactor pressure boundary.
General Design Criterion 60 was considered in the design of the condensate polishing system. Consistent with GDC 60, the CPS design controls radioactive material releases to the environment. The CPS is anticipated to contain negligible quantities of radioactive contaminants during power operation and during shutdown. The system leakage, which may contain radioactivity, is collected and contained in the condensate sump. The leakage collected in the sump is monitored for radioactivity and routed if needed from the BPDS to the liquid waste management system for processing as described in Section 11.2.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-28 Revision 4.1 The effect of CPS on fission and corrosion product concentrations, and the effect of the quantity of spent resin and regenerant solution on radwaste system requirements is discussed in Sections 11.2, 11.3, and 11.4.
Consistent with 10 CFR 20.1101(b), the CPS design supports keeping radiation exposures ALARA. To maintain the radiation exposure to operating and maintenance personnel ALARA, the (system) is designed to facilitate maintenance, inspection, and testing in accordance with the guidance in RG 8.8. As the CPS is not normally a radiation hazard, no radiation shielding is provided for the CPS components.
Consistent with 10 CFR 20.1406, the CPS design supports minimization of contamination of the facility and the environment. Chapters 11 and 12 discuss the potential radiation of a primary to secondary coolant leak.
10.4.6.4 Inspection and Testing The CPS components are inspected and tested as part of the initial testing and startup program as described in Section 14.2.
The ITAAC are addressed in Section 14.3.
10.4.6.5 Instrumentation Instrumentation is provided to measure the pressure drop, flow, and outlet conductivity from each polisher to monitor performance. See instrumentation in Table 10.4-15, and see alarms in Table 10.4-16.
10.4.7 Condensate and Feedwater System The primary function of the CFWS is to supply feedwater with the necessary chemistry, temperature, and pressure to the SG.
Each NPM is supplied with a separate CFWS not shared with other NPMs.
The containment penetrating systems are divided into three portions: internal to containment, the containment and safety-related isolation valve(s), and the nonsafety-related portion external to the NPM.
The CFWS boundary extends from the MC to the flange immediately upstream of the SG feedwater isolation valves (FWIVs). The FWIVs are a part of the containment system.
10.4.7.1 Design Bases This section identifies the CFWS required or credited functions, the regulatory requirements that govern the performance of those functions, and the controlling parameters and associated values that ensure the functions are fulfilled. Together, this information represents the design bases, as defined in 10 CFR 50.2, as required by 10 CFR 52.47(a) and (a)(3)(ii).
Specific feedwater components provide a nonsafety-related, not risk-significant backup to plant safety features. One feedwater regulating valve (FWRV) is located
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-29 Revision 4.1 upstream of each containment system feedwater isolation valve (FWIV), as a means of backup isolation to the containment system FWIV as outlined in Section 6.2.4. Likewise, the feedwater check valve is used as a backup to the FWIV integral check valve to prevent SG backflow. Use of these valves as backup to plant safety features is discussed in Section 15.0.0.
General Design Criteria 2, 4, and 5 were considered in the design of the CFWS. No safety-related SSC are affected by the effects of natural phenomena such as earthquakes. The design of the CFWS provides protection of safety-related SSC from the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents. There are no safety-related components in the CFWS shared among NPMs, therefore failure of the CFWS does not impair the ability of other NPMs to perform their safety functions. See Section 10.4.7.3 for the CFWS safety evaluation.
The NPM decay and residual heat removal safety function is performed by the decay heat removal system (DHRS) flowpath requiring containment isolation. Consistent with PDC 34, the FWRVs provide a nonsafety-related backup to the FWIVs and provide additional assurance that the blowdown of a second steam generator (SG) is limited if a feedwater line were to break upstream of the FWIV. Secondary system isolation is provided to protect the steam generator inventory without an unnecessary cooldown.
Conformance with PDC 34 is further discussed in Section 5.4 and Section 10.4.7.3.
Consistent with GDC 60, the design of the CFWS ensures the capability to control releases of radioactive materials to the environment. Consistent with 10 CFR 20.1101(b), the CFWS design supports keeping radiation exposures ALARA. The CFWS is designed to meet the requirements of 10 CFR 20.1406 as it relates to minimization of contamination of the facility.
10.4.7.2
System Description
10.4.7.2.1 General Description The containment penetrating systems are divided into three portions: internal to containment, the containment and safety-related isolation valve(s), and the nonsafety-related portion external to the NPM. The three portions of the system are shown on Figure 10.1-1. The CFWS provides the upstream nonsafety-related portion.
The CFWS includes the following equipment and components:
condenser (Section 10.4.1) condenser hotwell (Section 10.4.1) condensate storage tank condensate pumps feedwater pumps feedwater heaters (closed-type) feedwater regulating and check valves
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-30 Revision 4.1 condensate polishing subsystem (Section 10.4.6)
FWTS (Section 10.4.11) providing pH and oxygen control The CFWS boundary extends from the MC to the upstream flanges of the FWIVs.
The CFWS is nonsafety-related and is primarily located within the TGB and reactor building (RXB), with the exception of some piping and the CST located outside.
The MC condenses turbine exhaust steam and collects it in the hotwell. The condenser hotwell can also receive makeup from the demineralized water system or the CST. The condensate pumps move the condensate from the hotwell through the condensate polishing subsystem (Section 10.4.6) and into the gland steam condenser (Section 10.4.3). After exiting the gland steam condenser, the water is treated by the FWTS (Section 10.4.11) to adjust the pH and to scavenge oxygen.
Following treatment, the condensate continues on into the feedwater portion of the system.
The system sends the feedwater through the feedwater heaters (FWHs), with the feedwater pumps raising system pressure prior to entry to the SGs. The feedwater continues into the SGs or returns to the condenser hotwell through the feedwater recirculation line. During plant startup, the recirculation path facilitates system chemical cleanup and adjustment of water quality prior to initiating feed to the SGs. Feedwater chemistry is maintained per the guidelines described in EPRI TR-1008224, Rev. 7 (Reference 10.4-3).
Downstream of the high-pressure feedwater heater (HP-FWH), the feedwater header divides into two lines. The feedwater flow in each line then passes through the FWRV, a check valve, the interface flanges, and the containment system FWIV.
See Figure 10.1-1.
Downstream of the FWIVs, each feedwater line penetrates the containment vessel (CNV) top head through separate CNV feedwater nozzles. Inside the CNV, each feedwater line is divided into two feedwater lines that connect to the respective SG feedwater plenums through reactor pressure vessel feedwater nozzles.
The redundant decay heat removal system (DHRS) return lines connect with each feedwater line upstream of the junction for the SG inlet lines inside the CNV.
Quality classification of the CFWS equipment and components is provided in Section 3.2. Components, piping, and structures are designed in accordance with applicable codes and standards as described in Sections 3.9.1 through 3.9.3.
Risk-significant equipment is addressed in Section 17.4. Regulatory treatment of nonsafety systems equipment is described in Section 19.3. Quality assurance is addressed in Chapter 17.
10.4.7.2.2 Component Description Component design data is provided in Table 10.4-17.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-31 Revision 4.1 Condenser and Condenser Hotwell A detailed description of the condenser and hotwell is provided in Section 10.4.1.
Condensate Storage Tank The CST is located external to the TGB. The CST provides a volume for makeup and rejection of condensate to and from the condenser hotwell based on hotwell level.
The CST includes the tank, piping, valves, and tank level instrumentation, and is maintained full with the demineralized water system. The necessary vents, drains, and piping connections to the hotwell are included.
Condensate Strainer A condensate strainer is located upstream of each condensate pump to filter out potential foreign materials.
Condensate Pumps Condensate pumps are located near the condenser hotwell. The condensate pumps are designed with positive shaft seals to minimize air inleakage. The seals are vented and drained to the MC.
The condensate pumps and pump control system are designed so that loss of one condensate pump does not result in trip of a feedwater pump.
Condensate pump flow is monitored for each pump with minimum flow protection provided through a common recirculation line to prevent pump damage. The recirculation line is sized to support the minimum required flow for two condensate pumps and the gland seal steam exhauster in operation.
The condensate pumps are protected from running with very low net positive suction head (NPSH) without tripping on short transient low levels in the hotwell.
Condensate Polishers The CPS maintains CFWS water quality in conjunction with the FWTS. The CPS is described in Section 10.4.6.
Gland Seal Condenser The gland seal condenser cools the gland sealing steam with condensate, and drains it to the condenser. The gland seal condenser is discussed in Section 10.4.3.
Feedwater Treatment System The FWTS maintains water quality in conjunction with the CPS. The FWTS is described in Section 10.4.11.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-32 Revision 4.1 Feedwater Heaters Feedwater heaters preheat the feedwater before returning to the steam generators. This improves the thermodynamic efficiency of the system, reduces plant operating costs, and helps reduce thermal stress on the steam generators.
Condensate is progressively warmed in the tube side of successive FWHs by turbine extraction steam. The FWHs can be isolated and have a full-flow bypass.
Level in each of the FWHs is automatically controlled using a modulating drain control valve on the downstream heater.
Feedwater Heater Vents and Drains The heater vents and drains subsystem manages the condensing extraction steam flow through the shell side of the FWHs. Cascading drains flow by gravity to the condenser. Drain coolers are used to remove excess heat. Each FWH is individually vented to the condenser.
Feedwater Pumps Three feedwater pumps are located downstream of the low-pressure feedwater heater (LP-FWH) and the intermediate-pressure FWH (IP-FWH), and upstream of the HP-FWH. Feedwater pump flow is monitored for each pump with minimum flow protection provided through a dedicated recirculation line sized for the pump required minimum flow. The feedwater pumps and pump control system are designed so that the trip of one feedwater pump does not result in a turbine generator trip or reactor trip. Standby feedwater pumps are provided with autostart capability on low pressure or pump trip.
Feedwater Regulating Valves The FWRVs are used during normal and transient operation to control and equalize feedwater flow to the steam generators. The FWRVs are located in the RXB and are upstream of the FWIVs.
Normal control of the FWRVs is through the MCS. In off-normal conditions the MPS overrides normal control of the valves and can force closure. Each FWRV is designed to close on loss of power or control signal of DHRS actuation and secondary system isolation, regardless of the operating mode, and performs a feedwater isolation function as a backup to the FWIV. As such, the FWRVs meet the same flow requirements as the FWIVs.
The nonsafety-related FWRVs are used for event mitigation as backup protection for the safety-related FWIVs as described in Section 15.0.0.6.6. The FWRV is a commercially available valve that utilizes a proven design and demonstrates reliable operation based on operating experience in feedwater systems. A design with no previous operating experience may be proven through testing to demonstrate that the valve actuates as expected at operating conditions.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-33 Revision 4.1 Each secondary FWRV is periodically tested in accordance with the Augmented Valve Testing Program described in FSAR Section 3.9.6.5. Valve functions and periodic testing requirements are specified in FSAR Table 3.9-17.
Feedwater Check Valves Two check valves are installed in each feedwater line. Both feedwater check valves prevent reverse flow from the steam generators whenever the feedwater system is not in operation and are designed to withstand the forces of closing after a CFWS line rupture.
The first check valve is upstream of and integral with the FWIV, providing backflow prevention. The second is downstream of the FWRV and is provided for secondary backflow prevention.
The nonsafety-related secondary FW check valves are used for event mitigation as backup protection for the safety-related FW check valves as described in Section 15.0.0.6.6. The secondary FW check valve is a commercially available valve that utilizes a proven design and demonstrates reliable operation based on operating experience in water systems. A design with no previous operating experience may be proven through testing to demonstrate that the valve actuates as expected at operating conditions.
Each secondary FW check valve is periodically tested in accordance with the Augmented Valve Testing Program described in FSAR Section 3.9.6.5. Valve functions and periodic testing requirements are specified in FSAR Table 3.9-17.
Condensate and Feedwater Piping The CFWS piping layout between components is shown in Figure 10.1-1. The CFWS and SG design include features that minimize the potential for water hammer and subsequent effects. Additional detail is provided in Section 3.6.3.
The CFWS piping meets ASME B31.1 (Reference 10.4-5) requirements. CFWS piping materials are further described in Section 10.3.6 and descriptions of piping and support design are provided in Section 3.6.
The design of the CFWS incorporates considerations to prevent the occurrence of erosion and corrosion. These considerations include material selection, limits on flow velocity, inspection programs, and limits on water chemistry to reduce FAC, erosion, and corrosion of piping and piping components. See Section 10.3.6 for a discussion of FAC.
10.4.7.2.3 System Operation Following refueling and reconnection of the NPM, the SG is placed in a startup cleanup mode using a condensate pump to circulate condensate through the condensate polishers, the feedwater system, the SG, into the steam lines and back to the condenser hotwell through a steam line low point drain. This alignment serves to fill the SG and set chemistry conditions in the SG and feedwater system.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-34 Revision 4.1 The DHRS isolation valves are opened simultaneously to also fill and clean the DHRS heat exchanger.
Startup and normal operation of the CFWS is an automated process. During plant startup, the CFWS is operated in several different configurations. Two standard recirculation configurations, short-cycle and long-cycle cleanup, are provided to allow for system cleanup and adjustment of water chemistry prior to initiating feed to the SG, as described above.
In the short-cycle cleanup alignment, condensate pumps supply condensate through the polishers, gland seal condenser, low-pressure feedwater heaters, intermediate-pressure feedwater heaters, and back to the condenser through the short-cycle recirculation valve, which is also the condensate pump minimum flow line. During short-cycle cleanup operation, the performance of the condensate polishers is verified, hotwell inventory is deaerated, and CFWS chemistry is brought into specification. In the long-cycle cleanup alignment, the short-cycle cleanup alignment is extended to bypass the feedwater pumps and flow is allowed to pass through the HP-FWH by opening the long-cycle cleanup recirculation valve to the condenser and closing the short-cycle cleanup recirculation valve.
While in long-cycle cleanup, the first feedwater pump is started with the FWIV remaining closed. In this lineup, with at least one condensate and feedwater pump operating and flow directed to the condenser, the CFWS is ready to be placed in service supplying feed to the SG.
Reactor startup can commence after the CFWS has been operating in long-cycle cleanup and chemistry is within allowable limits. The FWIVs are opened and FWRVs placed in service. As feedwater flow through the SGs increases, the long-cycle recirculation valve is closed.
The introduction of steam and roll of the turbine provide extraction steam to the shell side of the FWHs, raising feedwater temperature as CFWS flow through the tube side of the heater increases. Condensate from condensed extraction steam is drained to the condenser as FWH level is stabilized and heater startup vents are closed.
An additional condensate pump and feedwater pump is placed in service to support SG flow requirements (Table 10.4-17). The third condensate and feedwater pumps are set to automatically start (standby).
The CFWS is capable of 100 percent power operation with two condensate pumps and two feedwater pumps in service. The CFWS is able to accommodate the step load changes (Section 10.2.2) without significant deviation from programmed SG water level or a major effect on the feedwater system. The CFWS has the capability of accommodating the necessary changes in feedwater flow to the SG with the steam pressure increase resulting from a 100 percent load rejection.
During normal operation, two condensate pumps take suction from the hotwell providing flow through the CPS, gland sealing steam condenser, low-pressure feedwater heaters, and intermediate-pressure feedwater heaters to the suction of
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-35 Revision 4.1 the feedwater pumps. The feedwater pumps take suction from the discharge of the IP-FWH driving flow through the HP-FWH to the FWRVs.
For normal operating conditions between 0 and 100 percent load, system operation is primarily automatic. Automatic level controls maintain inventory levels in the condenser hotwell, FWHs, and the condensate storage.
The CFWS also provides cooling flow to the turbine bypass desuperheater to cool the up to 100 percent superheated bypass steam to saturated conditions.
The PSS (Section 9.3.2) continuously monitors pH, conductivity, and oxygen concentration through sample points within the FWS. The PSS also provides the capability to pull and analyze grab samples.
The FWTS (Section 10.4.11) provides pH and oxygen control. In conjunction with the CPS. The FWTS maintains CFWS and SG water quality when connected to the NPM. Secondary water chemistry is discussed in more detail in Section 10.3.5.
Shutdown and cooldown of the NPM is an automated process accomplished through coordinated turbine control, feedwater control, and reactivity control. As NPM power is lowered, the FWRV and feedwater pump speed control modulate consistent with SG feed demand as power is reduced.
The automated shutdown lowers power to a hold point, when one feedwater and condensate pump can be secured. Automated shutdown is continued to a second hold point when the turbine is tripped, diverting steam flow through the bypass valve to the condenser. Following turbine trip, the automated shutdown is continued with control rod insertion until the reactor is tripped. Subsequently, a second feedwater pump is shut down when it is no longer needed to support SG feed demand and pressure.
As the reactor is cooled down, feedwater flow is adjusted by condensate pump operation to maintain SG inventory. As the RCS cools and steam generation diminishes SG feed, demand lowers to the SG switchover point, at which feedwater flow is raised to fill the SG and overflow the steam line with flow back to the condenser through the steam line drip leg trap.
The condenser hotwell capacity, CST inlet to the hotwell, and the demineralized makeup water inlet to the CST provide capacity for additional feedwater to the SG to maintain inventory during an off-normal reduction of inventory. The CFWS is designed and operated to prevent transients that could allow steam to enter the feedwater piping.
The condensate pumps are configured to provide redundancy to ensure operations are not interrupted or reduced in the event of a pump failure or trip.
Upon loss of an operating condensate pump a standby pump is aligned to start automatically in sufficient time that steady flow to the SG is maintained and no trip of a feedwater pump occurs.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-36 Revision 4.1 The feedwater pumps are configured with a standby pump that starts automatically on a running feedwater pump trip with sufficient response time to maintain steady system flow. The loss of a single feedwater pump does not result in a turbine generator or reactor trip.
Loss of normal AC power results in a loss of feedwater to the SG. A reactor trip occurs on low steam pressure or low feedwater flow as a result. The sudden loss of feedwater flow and termination of steam flow to the turbine causes the SG heat removal rates to decrease, which results in an increase in the reactor coolant temperature. As a result, the reactor coolant expands and surges into the PZR. The DHRS initiates and establishes decay heat removal. The RCS pressure and temperature are maintained within required limits. See Section 15.2.7 for a discussion of the loss of normal feedwater.
An excessive feedwater flow malfunction causes an increase in feedwater flow resulting in a reduction of steam superheat, increased SG inventory, and reduction in outlet temperature. If overcooling of the RCS occurs, a negative moderator temperature coefficient causes an increase in reactor power and potentially leads to a reactor trip on a high steam pressure or power increase signal. See Section 15.1.2 for a discussion of an increase in feedwater flow.
The loss of feedwater heating malfunction causes a decrease in feedwater temperature that increases heat removal from the RCS and lowers the RCS temperature. A negative moderator temperature coefficient causes a positive reactivity insertion that increases the reactor power and potentially leads to a reactor trip on a power increase signal. See Section 15.1.1 for a discussion of a loss of feedwater heating.
A feedwater line break outside of containment is isolated by the FWIVs. The FWRVs provide a backup isolation to the FWIVs. See Section 15.2.8 for a discussion of feedwater line breaks.
Inadvertent DHRS actuation and secondary system isolation causes closure of the MSIV and MFIV on the affected side of the secondary system. This increases the secondary side pressure on the affected SG. The RCS pressure and temperature increases at a lower rate. The unaffected SG train steam production is lower than the turbine steam demand. The reactor trips on high steam pressure, high PZR pressure, or high PZR level. See Section 15.6.1 for the inadvertent opening of a reactor safety valve.
A steam line break event refers to a main steam line break ranging from a small break to a double-ended rupture of a main steam line. Initially, the steam flow is increased before the affected steam line is isolated and depressurizes. After a short time of overcooling, the RCS temperature and pressure increase. If the steam line break is inside the containment, the reactor trips on high containment pressure. If the steam line break is outside the containment, the reactor trips on low steam pressure or low PZR level or pressure. For breaks outside containment, the break flow is terminated by closure of the MSIV on the affected SG or after CFWS is isolated and the SG boils dry. For breaks inside the containment, the break flow is
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-37 Revision 4.1 terminated after feedwater flow is isolated and the SG dries out. A steam line break is discussed in Section 15.1.5.
The SGTF is defined as a double-ended rupture of a single SG tube. Primary coolant from the RCS enters the secondary system, driven by the pressure difference between the RCS and the secondary side of the SG. As a result, the inventory, pressure, and activity in the affected SG increase. The break flow depressurizes the RCS and decreases the PZR level. On the secondary side, the FWIVs and FWRVs isolate on a low-low PZR level containment isolation signal to prevent excessive loss of RCS inventory. The reactor trips on high steam pressure, low PZR pressure, or low PZR level. An SGTF is discussed in Section 15.6.3.
The sudden loss of CFWS flow at power causes the SG heat removal rates to decrease, which causes the reactor coolant temperature to increase. The RCS fluid expands, flows into the PZR, thereby increasing the pressure. The SG liquid levels decrease following the termination of feedwater flow. The reactor trips on high PZR level and pressure, or low feedwater flow. This event results in the closure of the MSIVs and the actuation of the DHRS. The DHRS initiates and establishes decay heat removal and control RCS pressure and temperature within required limits. A loss of feedwater flow is discussed in Section 15.2.7.
10.4.7.3 Safety Evaluation The portion of the feedwater piping from the SG feedwater nozzles to the outermost FWIV flange is classified as safety-related Quality Group B. This portion of the system is designed to ensure feedwater system isolation in accident situations, such as a feedwater line break, and containment isolation in cases in which the feedwater system could potentially become a containment bypass pathway (e.g., SGTF) and is included in the containment system described in Section 6.2. One FWRV is located upstream of each containment system FWIV as back up for the performance of the FWIV design bases functions. Likewise, the feedwater check valve is used as a back up to the FWIV integral check valve to prevent SG backflow. Both valves are nonsafety-related and not risk significant.
General Design Criterion 2 was considered in the design and arrangement of the condensate and feedwater system. No safety-related structures, systems, or components are affected by this system from the effects of natural phenomena such as earthquakes. The isolation backup portions of CFWS are contained in the RXB, which is a Seismic Category I structure designed to withstand the effects of natural phenomena, such as earthquakes, tornadoes, hurricanes, floods, tsunamis and seiches. The adequacy of the structural design of the RXB to withstand these phenomena is further described in Section 3.3 for wind and tornadoes, Section 3.4 for flooding, Section 3.5 for missile protection, and Section 3.7 for earthquakes. Thus, these backup portions of CFWS are designed to remain functional during and after a safe shutdown earthquake and meet the guidelines of RG 1.29. The RXB is designed as an engineered barrier to withstand a postulated design basis missile. Consistent with RG 1.117, this satisfies GDC 2 by the proper design and use of missile barriers (i.e., the RXB) to protect essential SSC against potential missiles generated by tornado or hurricane winds.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-38 Revision 4.1 The nonsafety-related portions of the CFWS are not located in areas that contain safety-related components and are not required to operate during or after an accident.
No safety-related SSC are affected by the effects of natural phenomena such as earthquakes. The seismic and quality classifications of CFWS components are described in Section 3.2. Flooding is evaluated in Section 3.4.1.
General Design Criterion 4 was considered in the design and arrangement of the condensate and feedwater system. The design of the CFWS provides protection of safety-related SSC from the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents. Internally generated missiles, pipe whip, and jet impingement forces associated with pipe breaks do not prevent the CFWS from performing safety functions. Isolation backup portions of the CFWS are protected from pipe whip and jet impingement forces resulting from breaks in nearby systems (including the CFWS of adjacent NPMs) by the piping design layout.
These portions of the CFWS are physically separated from safety-related systems in the RXB and have no adverse impacts on safety functions. Refer to Section 3.12 for a description of the design of piping systems and piping supports used in Seismic Category I, Seismic Category II and non-seismic systems. Feedwater components and piping located outside of the RXB are classified Quality Group D and Seismic Category III. The analysis of a postulated high-energy line failure is provided in Section 3.6.1 and Section 3.6.2.
Isolation backup portions of the CFWS which are located within the RXB are protected from the effects of missiles generated by plant equipment failures outside the RXB. See Section 3.5 for the discussion of missile protection.
Refer to Section 3.6.3 for a description of SG design features implemented to prevent fluid flow water hammer. The potential for water hammer in the CFWS is minimized by design features such as pipe slope, the use of available drains before startup, and adjustment of valve closure timing. The potential for water hammer can be further reduced through the use of operating and maintenance procedures as described in NUREG 0927, Evaluation of Water Hammer Occurrence in Nuclear Power Plants.
General Design Criterion 5 was considered in the design of the condensate and feedwater system. The components in the CFWS are not shared among NPMs; therefore, failure of the CFWS does not impair the ability of other NPMs to perform their safety functions.
The condensate and feedwater system is designed to avoid FAC:
feedwater piping and components are constructed using material resistant to FAC flow velocity and changes in flow direction is limited consistent with the guidance of NSAC-202L (Reference 10.4-4) feedwater chemistry is continuously monitored and controlled The CFWS and supporting systems monitor and control secondary water chemistry to maintain water quality specifications during normal operation and AOOs.
Flow-accelerated corrosion is discussed further in Section 10.3.6.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-39 Revision 4.1 Principal Design Criterion 34 was considered in the design of the MSS. The decay and residual heat removal safety function per PDC 34 is performed by the DHRS flowpath, and containment isolation function of the containment system, along with the secondary system isolation function, are performed by the MSIVs and the feedwater isolation valves. Secondary system isolation is provided to protect the steam generator inventory without an unnecessary cooldown. Consistent with PDC 34, the nonsafety-related secondary MSIVs downstream of the MSIVs are credited as backup isolation components in the event that an MSIV fails to close.
General Design Criterion 60 was considered in the design of the condensate and feedwater system. Consistent with GDC 60, the CFWS design controls radioactive material releases to the environment. Consistent with 10 CFR 20.1101(b), the CFWS design supports keeping radiation exposures ALARA. To maintain the radiation exposure to operating and maintenance personnel ALARA, the CFWS is designed to facilitate maintenance, inspection, and testing in accordance with the guidance in RG 8.8. The CFWS design satisfies the requirements of 10 CFR 20.1406 in that it supports minimization of contamination of the facility and the environment.
Primary-to-secondary leakage from an SGTF has the potential to introduce radioactive material into the CFWS. Main steam and condensate monitoring with MSS and CFWS isolation capabilities minimize the contamination and release to the environment. The CFWS drains to the BPDS, which discharges to the radioactive waste drain system should the CFWS become contaminated.
Detected radioactive material in the condenser is managed by the CARS (Section 10.4.2). Radiation monitors are also provided on the exhaust from the gland seal condenser (Section 10.4.3).
The results of the CFWS failure modes and effects analysis is presented in Table 10.4-18.
Failure modes and effects analysis for FWIV valves can be found in Table 6.2-6.
10.4.7.4 Inspection and Testing Requirements The CFWS is inspected and tested prior to plant operation as described in Section 14.2.
Because the CFWS is in use and essential parameters are monitored during normal plant operation, the satisfactory operation of the system components demonstrates system operability.
The ITAAC are addressed in Section 14.3.
10.4.7.5 Instrumentation Requirements Feedwater instrumentation is designed to facilitate automatic operation, remote control, and monitoring of system parameters. Instrumentation and controls are provided in the MCS to monitor variables and control CFWS operation over its anticipated range of normal operation, AOOs, and accident conditions to ensure adequate safety. Feedwater parameters monitored and instrumentation details are listed in Table 10.4-19.
Positioning of the FWRVs and speed control of the feedwater pumps are functions of the MCS. For each SG, the feedwater control system maintains the feedwater flow
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-40 Revision 4.1 supply. The MCS is able to accommodate specified step load changes without a significant deviation from the programmed control band or major effect on the feed system. See Table 10.4-17. Chapter 7 describes the MCS.
10.4.8 Steam Generator Blowdown System This section is applicable only to pressurized water reactor SG designs that incorporate a blowdown system. As described in Section 5.4.1, the NuScale Power Plant SG design does not use a blowdown system. Therefore, this section is not applicable to the NuScale design.
10.4.9 Auxiliary Feedwater System The NuScale Power Plant design neither requires nor uses an auxiliary feedwater system.
Therefore, this section is not applicable to the NuScale design.
The DHRS (Section 5.4.3) performs some functions similar to an auxiliary feedwater system.
However, as compared to an auxiliary feedwater system, the DHRS differs substantially in its design, operation, and relationship to the small break loss-of-coolant accident plant response.
10.4.10 Auxiliary Boiler System The ABS is a nonsafety-related non-seismic system designed to supply steam to systems where main steam is not available or not preferred.
10.4.10.1 Design Bases This section identifies the ABS required or credited functions, the regulatory requirements that govern the performance of those functions, and the controlling parameters and associated values that ensure that the functions are fulfilled. Together, this information represents the design bases, as defined in 10 CFR 50.2, as required by 10 CFR 52.47(a) and (a)(3)(ii).
The ABS serves no safety function, is not credited for mitigation of a DBA, and has no safe shutdown functions.
General Design Criteria 2, 4, and 5 are considered in the design of the ABS. No safety-related SSC are affected by the effects of natural phenomena such as earthquakes. The design of the ABS provides protection of safety-related SSC from the environmental conditions associated with normal operation, maintenance, testing and postulated accidents. There are no safety-related components in the ABS that are shared among NPMs; therefore, failure of the ABS does not impair the ability of other NPMs to perform their safety functions.
Consistent with GDC 60, the design of the ABS ensures the capability to control releases of radioactive materials to the environment. Consistent with GDC 64, the system is monitored for radioactivity that may be released from normal operations, including anticipated operational occurrences, and from postulated accidents.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-41 Revision 4.1 Consistent with 10 CFR 20.1101(b), the (system) design supports keeping radiation exposures ALARA. Consistent with 10 CFR 20.1406, the ABS is designed to preclude contamination of connecting systems, and thus minimize contamination of the associated systems, facility, and the environment.
The ABS component design parameters are shown in Table 10.4-20.
10.4.10.2
System Description
The ABS is a nonsafety-related non-seismic system designed to supply steam to systems where main steam is not available or not preferred. The ABS consists of two separate systems. The high-pressure system is dedicated to supplying steam to the module heatup system (MHS) heat exchangers during startup and shutdown. The primary functions of the low-pressure system are to provide steam to the turbine gland seals, the MC for deaeration, and to the condensate polishing resin regeneration system.
The high-pressure and low-pressure system configurations are depicted on Figure 10.4-4a and Figure 10.4-4b and are comprised of vendor-supplied boiler skid packages. The ABS provides 18,000 lb/hr of 575-degree steam at 1100 psig and 4600 lb/hr of 575-degree steam at 500 psig at the required chemistry quality, during all modes of plant operation including AOOs, for the following functions:
the MHS, described in Section 9.3.4, to heat the primary coolant to initiate natural circulation during startup and shutdown turbine gland sealing sparging steam for MC deaeration at lower loads resin regeneration for the CPS 10.4.10.2.1 General Description The high-pressure ABS supply header is protected by pressure relief valves and monitored by pressure and temperature transmitters. Supply lines off the header distribute the steam to the MHS. Two high-pressure boilers (one primary and one redundant) supply steam to the MHS. One boiler supports heatup of a single NPM.
The simultaneous heatup of an NPM from each group of up to six NPMs can be supported using both high-pressure auxiliary boilers.
The pressure of the returning MHS steam is reduced by a pressure control valve and a flash tank, and collected as condensate in a condensate collection tank with relief valve. Excess steam pressure is vented. The demineralized water system feeds makeup water as needed, and the outlet of the CST flows to the inlet suction of redundant boiler feedwater pumps. Upstream of the feedwater pumps, a chemical addition system injects chemicals for water quality. Feedwater pumps supply redundant ABS boilers with water at the required pressure, and check valves downstream of each pump prevent backflow through the idle pump.
Boiler blowdown is monitored with a flow meter control valve, and the common blowdown header is cooled by a heat exchanger and discharged to the BPDS. Each
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-42 Revision 4.1 blowdown stream has a sampling line routed to the PSS to monitor and maintain water quality for the ABS.
A line off the high-pressure steam header is routed to the low-pressure steam header for when the low pressure boiler is out of service. Protected by double blocking valves, a pressure reducer and relief valves, the pressure and temperature downstream of the pressure reducing valve is monitored.
The ABS has provisions for chemical addition for chemistry control of the steam from the auxiliary boiler. During boiler operations, water makeup is provided from a non-radioactive demineralized water source. In order to maintain the chemistry requirements of the system, appropriate additives are used to control oxygen and pH consistent with secondary side chemistry requirements described in Section 10.3.5. Each boiler system (low-pressure and high-pressure) has a blowdown line connected to the BPDS. The blowdown is cooled by a heat exchanger after entering the BPDS. Each boiler system has a sample line from the steam supply and the blowdown to the PSS.
COL Item 10.4-2:
A COL applicant that references the NuScale Power Plant design certification will describe the type of fuel supply for the auxiliary boilers.
During operation, the low-pressure ABS supply header provides steam to the turbine gland seals during NPM startup, the MC, and the CPS for resin regeneration.
It is protected by triple pressure relief valves and monitored by pressure and temperature transmitters. During NPM startup, the MSS flow is not established, and thus the ABS must supply gland seal steam to the TGSS. This function is transferred to the individual NuScale Power Module MSS when sufficient supply is generated.
For the low-pressure ABS, the flow is monitored by a flow transmitter which is used to control the amount of steam fed to the gland seals. The backup steam supply from the high-pressure boiler system is isolated by double block valves and a pressure-reducing valve. The supply line downstream of the pressure-reducing valve is protected by double pressure relief valves. The pressure and temperature downstream of the pressure-reducing valve is monitored by a pressure transmitter and a temperature transmitter.
The steam to the gland seals is routed to the MC, and does not return to the ABS.
The condensate tank is protected by a pressure relief valve. The pressure-regulating valve vents steam to maintain pressure which is monitored by a pressure transmitter.
The level inside the tank is measured and monitored by a level transmitter. The demineralized water system, through a level control valve, feeds makeup water into the condensate tank to compensate for the blowdown out of the boiler or boiler drum and the gland seal steam. The outlet of the condensate tank flows to the inlet suction of redundant boiler feedwater pumps. Upstream of the feedwater pumps, a chemical addition system injects essential chemicals required for water quality.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-43 Revision 4.1 The redundant feedwater pumps supply the boiler and boiler drum with water at the required pressure.
Blowdown from the boiler and boiler drum is measured by an inline flow meter and controlled by a flow control valve. The blowdown from the low-pressure boiler flows into a single header and is discharged to the BPDS. The blowdown stream has a sampling line routed to the PSS to monitor and maintain water quality for the ABS.
The ABS is designed to the requirements of Quality Group D and Seismic Category III. Section 3.2 shows the seismic design and quality group classifications for each major component.
10.4.10.2.2 Component Description For both the high-pressure and low-pressure portions, the major ABS components include boiler skids, a condensate collection tank, and chemical addition skids.
Specific components include:
packaged boiler with:
redundant feedwater pumps
deaerator
pressure relief
fuel supply valves steam supply piping and fittings flash tank condensate return tank, piping and fittings associated controls The ABS component design parameters are shown in Table 10.4-20.
Material selection is compatible with operating conditions. See Table 10.4-20 for ABS material.
Boiler Each ABS boiler generates steam with a site-specific fuel supply.
Feedwater Pumps For each system, the ABS feedwater pumps provide sufficient capacity for the maximum expected steam makeup from the ABS boiler with sufficient reserve. A redundant pump allows for component service during operation.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-44 Revision 4.1 Deaerator A deaerator is provided in each ABSs to remove excess gases during operation of the system.
Pressure Relief A pressure-relief valve is installed on each ABS boiler. It maintains the system pressure below the design maximum and can manage the maximum expected flow from the worst transient.
Valves The ABS valves are provided on serviced components to allow component selection and servicing during operation. Valves are also provided to seamlessly integrate the use of ABS steam with main steam as desired.
Flash Tank and Condensate Return Tank A flash tank is used to vaporize and condense hot condensate before returning the liquid to the system. A condensate return tank is provided for each boiler system. It is sized to accommodate the condensate return from the maximum expected number of simultaneous components.
10.4.10.2.3 System Operation Operations are described as those supporting a single NPM operation status, even if a single NPM is shutdown while the other NPMs are running.
During normal operation, the low-pressure ABS supplies steam to the TGSS gland seals during NPM startup, the MC, and the CPS for resin regeneration. During NPM startup and shutdown when the MSS flow is not established, the ABS supplies gland seal steam to the TGSS. This function is transferred to the MSS of the individual NPM when sufficient supply is generated. The high-pressure ABS supplies steam to the MHS for NPM heatup and shutdown. When the NPM temperature reaches a set point, the ABS supply to the heat exchangers is discontinued and the inlet valve to the MHS heat exchanger isolated. The high pressure ABS can supply steam to the low-pressure header if needed (for backup only) through a pressure-reducing valve.
The ABS does not run continuously, but is brought online when needed. The system is monitored locally and in the MCR. Pressure, temperature, level, flow, remotely-operated valve position transmitters supply the operators with necessary system information.
The ABS is equipped with protective features that activate should the pressure increase beyond allowable limits. Pressure-relief valves automatically vent steam if the pressure increases above a set point to protect the system and prevent overpressure failure. If the water level in the boiler or condensate tank is too high or too low, or if flow rates or temperatures are out of safe operating limits, alarms
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-45 Revision 4.1 sound locally in the auxiliary boiler building and in the MCR to alert the operator that attention or action is required. Level transmitters monitor the condensate level inside the condensate collection tanks. If the level falls below a lower limit, the level control valve in the demineralized water supply line modulates open to add water to the tank. If the water level rises above an upper limit, the level control valve modulates closed to allow the boiler feedwater pumps to lower the level in the condensate tank. Flow transmitters on the blowdown of the boilers modulate the downstream flow control valve to regulate the volume of blowdown of the boilers.
The ABS does not need to maintain essential functions in the event of adverse environmental phenomena, pipe breaks, or loss of normal AC power. The ABS is nonsafety-related and is not needed post-DBA.
10.4.10.3 Safety Evaluation The ABS serves no safety function, is not credited for mitigation of a DBA, and has no safe shutdown functions.
GDC 2 was considered in the design and arrangement of ABS components. The ABS is nonsafety-related, but portions of the ABS are contained in the RXB, which is a Seismic Category I structure, designed to withstand the effects of natural phenomena, such as earthquakes, tornadoes, hurricanes, floods, tsunamis and seiches. Thus the portions of the ABS inside the RXB are designed to preclude adverse seismic interactions during and after a safe shutdown earthquake (SSE) consistent with Regulatory Guide 1.29. The RXB is designed as an engineered barrier to withstand a postulated design basis missile. Consistent with Regulatory Guide 1.117, this satisfies the criteria of GDC 2 by the proper design and use of missile barriers (i.e., the RXB) to protect essential SSC against potential missiles generated by tornado or hurricane winds.
The portions of ABS that are housed in the TGB are nonsafety-related and are not located in areas that contain safety-related components and are not required to operate during or after an accident. No safety-related SSC are affected by the effects of natural phenomena such as earthquakes on the ABS.
General Design Criterion 4 was considered in the design of the auxiliary boiler system.
The design of the ABS provides protection of safety-related SSC from the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents. A failure of the ABS that releases the water inventory and the resulting flooding does not prevent the operation of safety-related SSC. The plant flooding evaluation is addressed in Section 3.4. The dynamic impacts from missiles, water and steam system failures are addressed in Sections 3.5 and 3.6, respectively.
General Design Criterion 5 was considered in the design of the auxiliary boiler system.
There are no safety-related components in the ABS that are shared among NPMs; therefore, failure of the ABS does not impair the ability of other NPMs to perform their safety functions.
General Design Criteria 60 and 64 were considered in the design of the auxiliary boiler system. Consistent with GDC 60, the design of the ABS ensures the capability to control releases of radioactive materials to the environment. Consistent with GDC 64, the
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-46 Revision 4.1 system is monitored for radioactivity that may be released from normal operations, including anticipated operational occurrences, and from postulated accidents.
Process radiation monitors on each high-pressure return line from the MHS heat exchangers monitor the steam or condensate exiting, and a process radiation monitor on the vent of the pressure regulating valve on the high-pressure condensate collection tank monitors the steam venting from the tank. If radiation is detected in the ABS that is greater than the high-high radiation isolation or if system power is lost, the ABS flash tank pressure regulating valve and the steam supply valves from both boilers isolate.
An adjacent-to-line radiation detector monitors the cross-tie line from the high-pressure to low-pressure ABS and isolates the high-pressure to low-pressure ABS cross-tie valve if the high-high radiation isolation setpoint is exceeded or if system power is lost.
Blowdown from the ABS is delivered to the BPDS south turbine building drain tank.
This tank provides a means to monitor for radioactive contaminants in the ABS blowdown line. If a high radiation condition is detected, an alarm is initiated in the MCR, the north waste water sump pumps and north oily waste pump automatically shut down and the discharge flow path to the balance of plant drain system collection tanks automatically isolates. Sufficient holdup capacity is provided for retention of liquid effluents containing radioactive materials in the 25,000 gallon BPDS south turbine building drain tank.
Consistent with 10 CFR 20.1101(b), the (system) design supports keeping radiation exposures ALARA. The ABS is normally a non-radioactive system; however, ABS interfaces with the MHS heaters which contain radioactive fluid. To maintain the radiation exposure to operating and maintenance personnel ALARA, the auxiliary boiler system is designed to facilitate maintenance, inspection, and testing in accordance with the guidance in RG 8.8. The ABS returns from the MHS heaters are equipped with radiation monitoring equipment and provisions for sampling by the Process Sampling System. The radiation monitors have high and high-high set points, both of which alarm in the MCR. Remote manual isolation capabilities of the gland steam exhaust system are available in the MCR. The PSS provides a safe means of sampling of condensate return from the MHS heaters for radiological contamination.
Where there is a risk of high radiation at interfaces with the ABS, shielding, pipe and valve galleries or labyrinth pathways are incorporated into pipe routes as needed.
Consistent with 10 CFR 20.1406, the auxiliary boiler system design supports minimization of contamination of the facility and the environment. The steam or condensate return from the module heatup system heat exchangers has radiation monitors that send a signal to the chemical and volume control system to isolate the affected module heatup system heat exchanger to prevent the flow of contamination and protect the remaining ABS from becoming contaminated. Additionally, the cross-tie line from the high-pressure to the low-pressure ABS and the blowdown line to the BPDS have radiation monitors to isolate the flowpath to prevent contamination of downstream components. Leaks and spills in the ABS are minimized and contained.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-47 Revision 4.1 The design features addressing the provisions of RG 4.21 are discussed in Section 12.3.6.
10.4.10.4 Inspection and Testing The ABS components are inspected and tested as part of the initial testing and startup program as described in Section 14.2.
The ABS is designed to be tested and inspected per the original equipment manufacturer inservice inspection and testing plan.
The ITAAC are addressed in Section 14.3.
10.4.10.5 Instrumentation Instrumentation is described in Table 10.4-21.
Pressure, temperature, flow, tank level, and valve position are provided on both the high-pressure and low-pressure ABS components.
A single adjacent-to-line radiation monitor is located on the cross-tie line from the high-pressure to low-pressure ABS. If radiation is detected in the ABS greater than the high radiation alarm setpoint, the system initiates a MCR alarm notifying the operators to investigate and initiate mitigating actions. If radiation is detected in the ABS that is greater than the high-high radiation isolation setpoint or if system power is lost, the high-pressure to low-pressure ABS cross-tie valve isolates. There are process radiation monitors on each high-pressure return line from the MHS heat exchangers to monitor the steam or condensate exiting, and a process radiation monitor on the vent of the pressure regulating valve on the high-pressure condensate collection tank to monitor the steam venting from the tank. If radiation is detected in the ABS that is greater than the high-high radiation isolation setpoint or if system power is lost, a signal is sent to the chemical and volume control system to isolate the affected module heatup system heat exchanger.
10.4.11 Feedwater Treatment System The FWTS treats and cleans the feedwater in conjunction with the CPS (Section 10.4.6) to maintain secondary water quality. The FWTS is part of the CFWS.
10.4.11.1 Design Basis This section identifies the FWTS required or credited functions, the regulatory requirements that govern the performance of those functions, and the controlling parameters and associated values that ensure the functions are fulfilled. Together, this information represents the design bases, as defined in 10 CFR 50.2, as required by 10 CFR 52.47(a) and (a)(3)(ii).
The FWTS is designed to provide for chemical addition and feedwater sampling during plant modes (except NPM transport), to maintain feedwater pH and dissolved oxygen levels.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-48 Revision 4.1 The FWTS serves no safety-related functions, is not credited for mitigation of a DBA, and has no safe shutdown functions. General Design Criteria 2, 4, and 5 were considered in the design of the FWTS. No safety-related SSC are affected by the effects of natural phenomena such as earthquakes. The design of the FWTS provides protection of safety-related SSC from the environmental conditions associated with normal operation, maintenance, testing and postulated accidents.
There are no safety-related components in the FWTS shared among modules; therefore, the FWTS does not impair the ability of other systems to perform their safety functions.
Consistent with GDC 60, the design of the FWTS ensures the capability to control releases of radioactive materials to the environment. Consistent with 10 CFR 20.1101(b), the FWTS design supports keeping radiation exposures ALARA.
Consistent with 10 CFR 20.1406, the FWTS is designed to preclude contamination of connecting systems, and thus minimize contamination of the associated systems, facility, and the environment.
10.4.11.2
System Description
10.4.11.2.1 General Description The FWTS is part of the CFWS described in Section 10.4.7 and is designed to control erosion and corrosion of CFWS components by monitoring and maintaining feedwater pH and dissolved oxygen levels during plant modes except NPM transport. See Section 10.4.7 for a discussion of seismic and quality group, equipment qualification, and applicable codes and standards for the FWTS.
Two chemical injection points are provided downstream of the CFWS condensate pumps. The FWTS includes separate equipment for pH control and oxygen scavenger injection. The equipment includes tanks, valves, piping, pumps, and instrumentation for each chemical addition.
10.4.11.2.2 Component Description The FWTS component design data is provided in Table 10.4-23.
Feedwater Treatment Tanks The FWTS has one tank for pH control and one tank for oxygen control that service up to six turbine generators in each TGB. Each tank is constructed of corrosion-resistant material that is compatible with the chemicals used. Each chemical addition tank includes connections for chemical fill, demineralized water supply, pump suction, pump relief valve return, level instrumentation, drain and loop seal overflows.
Chemical injection equipment is capable of independently injecting controlled amounts of oxygen scavenger and pH agent. The chemical addition portions of the CFWS system have capacity for at least 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of continuous chemical injection at
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-49 Revision 4.1 normal feed rates. Chemical addition tank overflows, drains, etc. are routed to the BPDS chemical waste collection sumps.
COL Item 10.4-3:
A COL applicant that references the NuScale Power Plant design certification will provide a secondary water chemistry analysis. This analysis will show that the size, materials, and capacity of the feedwater treatment system equipment and components satisfies the water quality requirements of the secondary water chemistry program described in Section 10.3.5, and that it is compatible with the chemicals used.
Feedwater Treatment Pumps The FWTS pumps are diaphragm simplex-type pumps with the wetted parts, except for the diaphragm, constructed of the appropriate grade of stainless steel for the chemical service and conditions. Redundant pumps are provided to support isolation for maintenance. Each pump or common line has a filter (or strainer) to filter out foreign materials. Each chemical addition pump has a discharge pressure greater than the condensate pump shutoff head. A pulsation dampener oil trap is provided in the discharge line of each chemical addition pump.
Feedwater Treatment Valves and Piping The FWTS valves and piping are designed to preclude water hammer.
10.4.11.2.3 System Operation 10.4.11.2.3.1 Startup Recirculation capability back to the condenser after the FWTS chemical addition is provided by the feedwater system. Reactor startup may commence after the CFWS system is operating in long-cycle cleanup and chemistry is within allowable limits.
10.4.11.2.3.2 Normal Operation The PSS continuously monitors the feedwater. When the feedwater quality is outside the parameters specified in the secondary water program described in Section 10.3.5, the FWTS provides chemical injections from the treatment tanks as appropriate to control water chemistry.
The chemical tanks receive concentrated chemicals that are diluted to normal service levels, as determined by the secondary water chemistry program, in the tanks by the addition of demineralized water.
Components are constructed out of materials compatible with higher concentrations of the chemicals used.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-50 Revision 4.1 10.4.11.2.3.3 Shutdown The FWTS maintains water quality suitable for long-term plant operation for plant conditions, including power operation, startup, shutdowns, and extended outages.
10.4.11.2.3.4 Off-Normal Operation - Extended Outages Connections are provided to allow for wet-storage or dry-storage of the condenser based upon water chemistry effects during short-term or long-term condenser shutdown.
10.4.11.3 Safety Evaluation The FWTS serves no safety-related functions, is not credited for mitigation of a DBA, and has no safe shutdown functions.
General Design Criterion 2 was considered in the design of the feedwater treatment system. No safety-related structures, systems, or components are affected by this system from the effects of natural phenomena such as earthquakes. The design and layout of the FWTS include provisions that ensure that a failure of the system will not adversely affect the functional performance of safety-related SSC.
The FWTS meets RG 1.29 in that it is not located in areas that contain safety-related or risk-significant components and is not required to operate during or after an accident.
The FWTS is Seismic Category III.
General Design Criterion 4 was considered in the design of the feedwater treatment system. The design of the FWTS provides protection of safety-related SSC from the environmental conditions associated with normal operation, maintenance, testing, and postulated accidents. The FWTS has been designed for the dynamic effects associated with possible fluid flow instabilities (e.g., water hammer) by having the FWTS designed in accordance with the guidance contained in NUREG-0927 and thereby eliminating or reducing the possibility of water hammer in SGs. See Section 3.6 for discussion of high-energy and moderate-energy pipe breaks.
GDC 5 was considered in the design of the feedwater treatment system. The FWTS has no safety-related components shared among modules and the FWTS does not impair the ability of other systems to perform their safety functions.
The FWTS functions to control pH and scavenge free oxygen to maintain water quality as specified in the secondary water chemistry program described in Section 10.3.5.
General Design Criterion 60 was considered in the design of the feedwater treatment system. Consistent with GDC 60, the FWTS design controls radioactive material releases to the environment. The FWTS is anticipated to contain negligible quantities of radioactive contaminants during power operation and during shutdown.
Consistent with 10 CFR 20.1101(b), the (system) design supports keeping radiation exposures ALARA. To maintain the radiation exposure to operating and maintenance
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-51 Revision 4.1 personnel ALARA, the FWTS is designed to facilitate maintenance, inspection, and testing in accordance with the guidance in RG 8.8. The FWTS design satisfies the requirements of 10 CFR 20.1406. Release of radioactivity to the environment by the CFWS (Section 10.4.7) is precluded in the event of a pipe leak, or break, or degradation of the integrity of safety-related equipment by monitoring and isolation valves. The FWTS portion is not expected to receive backflow, so should not become contaminated. Further discussion of the facility design features to protect against contamination is shown in Section 12.3.
10.4.11.4 Inspection and Testing The FWTS components are inspected and tested as part of the initial testing and startup program as described in Section 14.2. Preservice inspection requirements are discussed in Section 6.6.
The inservice testing program of FWTS pumps and valves is performed per Section 3.9.6.
The ITAAC are addressed in Section 14.3.
10.4.11.5 Instrumentation The pumps of the FWTS have controls to allow for automatic and manual operation.
Instrumentation provides tank level indication for proper water inventory and pump pressure to ensure the proper discharge pressure for chemical injection into the feedwater lines. See Table 10.4-24.
Samples are monitored to adjust chemical feed.
10.4.12 References 10.4-1 Heat Exchange Institute, Performance Standards for Liquid Ring Vacuum Pumps, HEI-2854, 4th Edition, 2011.
10.4-2 American Society of Mechanical Engineers, Atmospheric Water Cooling Requirement, ASME PTC 23 (R2009).
10.4-3 Electric Power Research Institute, Pressurized Water Reactor Secondary Water Chemistry Guidelines - Revision 7," TR-1008224, Palo Alto, CA.
10.4-4 Electric Power Research Institute, Recommendations for an Effective Flow-Accelerated Corrosion Program, EPRI #1015425 (NSAC-202L-R3), Palo Alto, CA, August 2007.
10.4-5 American Society of Mechanical Engineers, Code for Pressure Piping, B31, Section B31.1, Power Piping, New York, NY.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-52 Revision 4.1 Table 10.4-1: Main Condenser Design Data Parameter Data Condenser type Single pass Hotwell storage capacity Equivalent to at least three minutes of full-load condensate system operating flow during normal operation and a standby surge storage capacity equivalent to two minutes of full-load normal condensate flow Heat transfer duty See heat balance in Figure 10.1-2 Shell design pressure / temperature 5 psig / 250°F Tube design pressure / temperature 150 psig / 150°F Tube-side inlet temperature See heat balance in Figure 10.1-2 Approximate tube-side temperature rise See heat balance in Figure 10.1-2 Condenser outlet temperature See heat balance in Figure 10.1-2 Condenser tube data Tube material (main section)
High alloy of stainless steel or titanium (based on site circulating water conditions)
Tube sheet material Carbon steel-clad with the same material composition used for tube materials
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-53 Revision 4.1 Table 10.4-2: Main Condenser System Instrumentation Equipment Name Monitored Parameter (Units)
Local Display Signal to MCS MC pressure indicating transmitters A/B/C MC pressure (psia)
Yes Yes MC temperature indicating transmitter A/B/C MC temperature (°F)
Yes Yes MC hotwell level indicating transmitter A/B/C MC level (inches of H2O)
Yes Yes MC condensate emergency makeup line flow element Condensate flow (gpm)
N/A No MC condensate makeup emergency line flow transmitter Condensate flow (gpm)
No Yes MC emergency makeup level control valve position indicating transmitter Level control valve position
(%)
No Yes MC normal makeup level control valve position indicating transmitter Level control valve position
(%)
No Yes MC condensate normal makeup line flow element Condensate flow (gpm)
N/A No MC condensate makeup normal line flow transmitter Condensate flow (gpm)
Yes Yes MC hotwell cation conductivity analyzer Hotwell cation conductivity (microsiemens per centimeter
@ 25°C)
No Yes MC hotwell sodium analyzer Parts per billion (ppb)
No Yes Main steam deaeration isolation valve position switch open Valve not fully open No Yes Main steam deaeration isolation valve position switch closed Valve not fully closed No Yes Main steam deaeration flow control valve position indicating transmitter Valve position No Yes Main steam deaeration flow element Flow rate (lb/hr)
No Yes Main steam deaeration flow indicating transmitter Flow rate (lb/hr)
Yes Yes Auxiliary boiler system sparging steam isolation valve position switch open Valve not fully open No Yes Auxiliary boiler system sparging steam isolation valve position switch closed Valve not fully closed No Yes Auxiliary boiler system sparging steam flow control valve position indicating transmitter Valve position No Yes Auxiliary boiler system sparging steam flow element Flow rate (lb/hr)
No Yes Auxiliary boiler system sparging steam flow indicating transmitter Flow rate (lb/hr)
Yes Yes
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-54 Revision 4.1 Table 10.4-3: Condenser Air Removal System Design Data (Nominal)
Liquid Ring Vacuum Pumps Number 2
Capacity 100%
Operating capacity 12.5 SCFM of gas at an inlet pressure of 2.5 inches HgA Startup capacity 350 SCFM during condenser evacuation in preparation for operation Input 75 horsepower Seal water heat exchangers Number 2
Capacity / duty cycle 350,000 BTU/hr / 100%
Cooling input 60 gpm cooling water flow at 90°F or below Cooling capacity 30 gpm flow Seal water separator tanks Number 2
Size 100 gal
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-55 Revision 4.1 Table 10.4-4: Condenser Air Removal System Instrumentation Type Location Local Main Control Room Temperature indication Seal water inlet to LRVP Yes No Pressure gauge (vacuum)
LRVP suction Yes Yes Differential pressure Across LRVP inlet control valve Yes (control panel)
No Level gauge Seal water separator tank Yes No Level switch (low)
Seal water separator tank Yes Yes Flow gauge (rotometer)
Seal water separator tank Yes Yes Motor power (on/off)
Power breaker Yes Yes Radiation monitor Radioactive contamination CARS gaseous effluent Yes Yes
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-56 Revision 4.1 Table 10.4-5: Gland Seal Steam Skid Design Data Parameter Value Gland seal flow Sufficient for 1.5 to 2 times the normal gland clearances and maximum allowable auxiliary steam supply pressure Gland steam condenser Type Shell-and-tube type heat exchanger Gland seal condenser exhauster blowers Capacity 100%
Number 2
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-57 Revision 4.1 Table 10.4-6: Gland Sealing System Instrumentation Equipment Name Monitored Parameter Local Display Signal to MCS GS desuperheater feedwater supply isolation valve limit switch Valve fully open No Yes GS desuperheater feedwater supply isolation valve limit switch Valve fully closed No Yes GS desuperheater feedwater supply pressure transmitter Pressure psig Yes Yes GS desuperheater feedwater supply flow control valve (FCV) position transmitter Valve position %
Yes Yes GS desuperheater feedwater supply FCV position transmitter Valve position %
Yes Yes GS desuperheater feedwater supply pressure transmitter Pressure psig Yes Yes GS desuperheater steam supply pressure transmitter Pressure psig Yes Yes GS desuperheater steam supply pressure transmitter Pressure psig Yes Yes GS desuperheater steam supply temperature transmitter Temperature °F Yes Yes GS desuperheater steam supply temperature transmitter Temperature °F Yes Yes GS supply pressure transmitter Pressure psig Yes Yes GS supply flow element Steam flow lb/hr No Yes GS supply flow transmitter Steam flow lb/hr No Yes GS supply temperature transmitter Temperature °F Yes Yes GS condenser condensate flow element Steam flow lb/hr No Yes GS condenser condensate flow transmitter Steam flow lb/hr No Yes GS condenser condensate FCV position transmitter Valve position %
Yes Yes GS condenser isolation valve limit switch Valve fully open No Yes GS condenser isolation valve limit switch Valve fully closed No Yes TG lube oil supply pressure transmitter Pressure psig Yes Yes GS condenser condensate level indicator/transmitter Level indication Yes Yes GS desuperheater feedwater supply FCV position transmitter Valve position %
Yes Yes GS desuperheater feedwater supply FCV position transmitter Valve position %
Yes Yes
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-58 Revision 4.1 Table 10.4-7: Turbine Bypass System Component Details Turbine bypass valve Number 1 (per NPM)
Normal capability 10% step load change from steady state conditions in 60 seconds when the power level is in the range of 50 to 100 percent without necessitating a turbine trip.
Normal load rejection 100 percent Turbine bypass desuperheater Capacity Reduce full power steam flow 532,100 lbm/hr, normal pressure 500 psia, normal temperature 575°F to saturation
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-59 Revision 4.1 Table 10.4-8: Turbine Bypass System Instrumentation Equipment Name Monitored Parameter Local Display Signal to MCS MSS desuperheater steam supply FCV position transmitter Valve position %
Yes Yes MSS pressure transmitter (downstream of turbine bypass line)
Pressure psig Yes Yes Turbine bypass pressure transmitter (after DSH)
Pressure (psig)
Yes Yes MSS desuperheater feedwater supply pressure transmitter (before DSH)
Pressure (psig)
Yes Yes DSH feedwater isolation valve limit switch Valve fully closed No Yes MSS desuperheater feedwater FCV position transmitter Valve position (%)
Yes Yes
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-60 Revision 4.1 Table 10.4-9: Circulating Water System Design Parameters Circulating Water Pumps, per six NPMs Number 3 pumps per loop Capacity
((76353 gpm)) / 33% capacity Type Vertical, wet pit Motor horsepower (nameplate)
((1750 hp))
Limitations 3 pumps are sufficient when assuming loss of a single pump Traveling Screens Type Continuously moving Number 1 per pump Cooling Tower Cells per tower
((14))
Type Mechanical draft, induced One percent annual exceedance non-coincident wet bulb temperature
((80°F))
Range
((20°F))
Approach
((10°F))
Flow, each CWS loop
((228,000 gpm))
Construction code ACI 318 standards Testing standard Cooling tower performance standard ASME PTC 23 Cooling Tower Makeup and Blowdown Rate
((5320 gpm per loop))
Cycles of concentration
((5))
Chemical Treatment Materials
((biocide (typically sodium hypochlorite), algaecide, pH adjuster, corrosion inhibitor, scale inhibitor, and dispersant.))
Piping, including the expansion joints, butterfly valves, condenser water boxes, and tube bundles.
Size
((9-foot diameter))
Material Prestressed concrete lined pipe (underground); carbon steel pipe (above ground).
Code ASME B31.1 (above ground)
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-61 Revision 4.1 Table 10.4-10: Circulating Water System Interfaces System Function Condensate and feedwater system (CFWS)
Removes heat from the MCs, which are part of the CFWS Utility water system (UWS)
Provides makeup water and receives blowdown water Site drainage system (SDS)
Receives drain water from the cooling tower basin Process sampling system (PSS)
Takes samples from the CWS to monitor for pH, free chloride, total dissolved solids, and other chemical concentrations Electrical systems Provide power to components Control systems Control individual and shared component operation
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-62 Revision 4.1 Table 10.4-11: Circulating Water System Instrumentation Instruments Indication Type Location Local Main Control Room Level Transmitter Cooling tower basin, the common intake structure, and each individual pump bay Yes Yes Pressure Differential Indicating Transmitter Across the condensers No Yes Pressure Indicating Transmitter CWS piping Yes Yes Temperature Indicating Transmitter CWS water temperature Yes Yes Flow Indicating Transmitter CWS supply header No Yes Flow Indicating Transmitter Blowdown line Yes Yes Flow Indicating Transmitter CWS Cooling Tower Startup Flow Confirmation No Yes Valve Position Switch -- Open On MOVs responsible for equipment isolation Yes Yes Valve Position Switch -- Closed On MOVs responsible for equipment isolation Yes Yes Position Indicating Transmitter Flow Control Valve Percent Open Yes Yes Level Gauges Condenser water boxes Yes Yes Chlorine Monitor Cooling tower basin No Yes Total Dissolved Solids Monitor Cooling tower basin No Yes Total pH Monitor Cooling tower basin No Yes Chlorine Monitor CWS blowndown line No Yes
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-63 Revision 4.1 Table 10.4-12: Circulating Water System Alarms Instruments Indication Type Location Local Main Control Room Level alarm low/high Cooling tower basin No Yes Temperature alarm low/high Cooling Tower Basin No Yes Flow alarm low/high Circulating water pump discharge common header No Yes Flow alarm low/high Blowdown line No Yes Pressure differential alarm high Across condensers No Yes Level alarm low Condenser waterbox No Yes Temperature alarm high (2)
Cooling tower inlet No Yes
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-64 Revision 4.1 Table 10.4-13: Condensate Polishing System Operating Parameters Condensate polisher Type Ion exchange Number of trains 2 at 100% capacity per NPM Flow total Full (100%) condensate flow in each train Flow per NPM 100% of the condensate and feedwater flow at the design operating pressure and temperature Operating limits Freshwater plant: maintain chemistry with a continuous condenser tube leak of 0.001 gpm, or an increased leak rate of 0.2 gpm until repaired Brackish or seawater plant: maintain water chemistry during an orderly shutdown (8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />) with a leak rate of 0.1 gpm Resin Regeneration Subsystem Number 1 per TGB to service up to 6 NPMs
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-65 Revision 4.1 Table 10.4-14: Condensate Polishing System Impurity Limits Item Limit Sodium
< 1 ppb Chloride
< 3 ppb Sulfate
< 1 ppb Silica
< 10 ppb Total iron
< 5 ppb
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-66 Revision 4.1 Table 10.4-15: Condensate Polishing System Instrumentation Equipment Name Monitored Parameter (Units)
Local Display Signal To MCS Condensate polishing system bypass air operated valve open position switch Valve not fully open No Yes Condensate polishing system bypass air operated valve closed position switch Valve not fully closed No Yes Condensate polishing system filter pressure differential indicating transmitter Equipment pressure drop (psid)
Yes Yes Condensate polishing system inlet flow meter Condensate flow rate (gpm)
No Yes Condensate polishing system inlet flow indicator/
transmitter (redundant)
Condensate flow rate (gpm)
Yes Yes Condensate polishing system inlet temperature indicating transmitter Condensate temperature (°F)
Yes Yes Condensate polishing system rinse inlet flow meter Condensate flow rate (gpm)
No No Condensate polishing system rinse inlet flow indicator/transmitter Condensate flow rate (gpm)
Yes Yes Condensate polishing system verification flow control valve position indicating transmitter Flow control valve position (%)
No Yes
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-67 Revision 4.1 Table 10.4-16: Condensate Polishing System Alarms Instruments Indication Type Local Main Control room Condensate polishing system high inlet temperature Yes Yes Condensate polishing system inlet filter high pressure differential Yes Yes
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-68 Revision 4.1 Table 10.4-17: Condensate and Feedwater System Component Design Data Component / Parameter Value Condenser See Section 10.4.1.
Condensate storage tank Size 1000 ft3 Material/code stainless steel / API 620 Location site yard, see Figure 1.2-4 Condensate strainer Detail 1/8 inch stainless steel mesh Condensate pumps Number Three, 50% capacity Type vertical, single speed, multistage, (480vac) motor driven Use 1 pump used below 50% power 2 pumps used between 50% and 100% power One pump set to autostart (standby)
Condensate filter Condensate polishers See Section 10.4.6 Storage capacity 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of continuous chemical injection at the normal feed rates Gland seal condenser - see Section 10.4.3 Type shell and tube design condenser Condensate On the tube side Gland sealing steam on the shell side Feedwater treatment system (See Section 10.4.11)
Storage capacity for 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> of continuous chemical injection at the normal feed rates Feedwater heaters (closed type)
Number 3 (high-, intermediate-, and low-pressure)
Type horizontal shell and tube design Material constructed of carbon steel with stainless steel tubes Condensate Tube side Extraction steam Shell side Final outlet temperature 300°F Feedwater pumps Use 1 pump used below 50% power 2 pumps used between 50% and 100% power One pump set to start automatically (standby)
Number 3, 50% capacity Type Horizontal, multistage 480V with variable frequency drive Feedwater regulating valves Number of valves 2
Closure type air-operated Design spec in accordance with ASME BPVC 2013, 2011 Addenda,Section VIII and Heat Exchanger Institute 2622, 8th Edition
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-69 Revision 4.1 Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks Main Condenser xx*-FW-CND-0001
- reserved for module number (01 - 12)
- 1) The main condenser is responsible for condensing low pressure exhaust steam from the turbine.
A) Slow Loss of Condenser Vacuum Mechanical Condenser vacuum pressure plays an integral part in turbine performance and energy production. There are multiple innate chronic problems that can develop in the condenser over normal power production operations. These problems include, but are not limited to, air ingress, tube plugging, and tube bundle corrosion.
As these problems develop the amount of vacuum the condenser can pull decreases, reducing the efficiency of the system. Small decreases in condenser vacuum do not detrimentally effect plant operation; loss of vacuum above the required turbine back pressure causes a turbine trip.
As condenser backpressure increases it is possible to start the standby condenser air removal system to reduce vacuum.
Failure is identified by high pressure measurements from PIT-1002 A/B/C If the turbine trips due to a loss of condenser vacuum, the main steam header pressure increases rapidly. This results in a reactor trip due to high steam line pressure or high pressurizer pressure. The loss of condenser vacuum prevents the condenser from being used to remove heat generated by the reactor. The turbine bypass valve closes, and the DHRS actuates to remove decay heat after control rod insertion. No safety-related components are affected by loss of condenser vacuum.
This is an anticipated operational occurrence (AOO) for a NuScale Power Module.
B) Immediate Loss of Condenser Vacuum Mechanical Electrical/ I&C Operator Error Condenser vacuum pressure plays an integral part in turbine performance and energy production. Loss of vacuum above the required turbine back pressure causes a turbine trip.
Causes of this type of trip are loss of normal heat sink, loss of condenser air removal system. This results in a loss of condenser vacuum, and a turbine trip.
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-70 Revision 4.1 Main Condenser xx*-FW-CND-0001
- reserved for module number (01 - 12)
(cont)
- 2) Maintain purity of the condensate A) Minor Leak of Condenser Tubes Mechanical Circulating water enters the CFWS contaminating the system. Condensate polishers remove the contaminants.
Leaky tube is identified by taking tube bundles off line one at a time to determine leak source. Leaking tube is identified and repaired. Operating with one water box offline requires a module to be operated at a reduced load, but does not result in a turbine trip.
Failure detected by measurements from analyzers AIT-1005 for conductivity and AIT-1004 for sodium concentration.
None B) Major Leak of Condenser Tubes Mechanical A major leak of the condenser tubes results in a higher condensate level in the hotwell and an increase in condenser back pressure as circulating water enters the condenser.
A major leak of the condenser tubes introduces quantities of contaminants which may overwhelm the CPS and foul the CFWS.
Also, high main condenser level is measured by instruments LIT-1001 A/B/C in the main condenser hotwell.
Failure detected by measurements from analyzers AIT-1005 for conductivity and AIT-1004 for sodium concentration. AIT 1016 detects resin depletion and breakthrough occurring.
A major condenser tube leak results in a turbine trip and reactor trip due to detection of contamination in the CFWS. Operators are responsible for locating the damaged tubes for replacement.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-71 Revision 4.1 Main Condenser xx*-FW-CND-0001
- reserved for module number (01 - 12)
(cont)
- 3) Designed for full flow bypass following a turbine trip.
A) Failure of Bypass valve to open.
B) Failure of Bypass valve to close when needed.
Mechanical The effect is dependent on the reason for the valve open requirement. If the valve open requirement is because of a need to reduce power output (for example load following etc), a different reactor need to be selected for power reduction. If the valve open requirement is due to a turbine generator trip then the reactor needs to be tripped and steam pressure controlled by main steam safety valve.
Failure of bypass valve to close results in loss of power generation. The valve needs to be either manually closed or repaired.
Bypass valve position indicator shows valve failed to respond when valve fails to open/close. The turbine either fails to start/stop.
Bypass valve failure has no impact on safety-related components.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-72 Revision 4.1 Condensate Pumps xx*-FW-P-0005 A/B/C
- reserved for module number (01 - 12)
- 1) Draws suction from the main condenser.
Delivers condensate to the feedwater pumps with adequate pressure.
A) Fail to Start Mechanical Electrical/ I&C Failure of a condensate pump to start upon the trip of one of the operational condensate pumps results in a decreased supply pressure to the feedwater pumps.
If adequate supply pressure and flow rate to the feedwater pumps is not achieved then one or both of the feedwater pumps trip due to low suction pressure. This event results in a loss of feedwater flow to the SGs.
Failure would be detected by downstream instruments PIT-1009 A/B/C and FE/FIT-1010 A/B/C.
A decrease in feedwater flow to the SGs because of a condensate pump trip causes the RCS temperature to increase. This leads to the feedwater pump variable frequency drives (VFDs) increasing their motor output to increase the flow. If one condensate pump is not able to supply adequate pressure to the inlet of the feedwater pumps, one or both of the feedwater pumps trip and this incident is consistent with a loss of feed water flow. A loss of feed water flow results in a reactor trip due to high pressurizer pressure.
Loss of feedwater is an AOO for a NuScale module.
B) Pump Trip Mechanical Electrical/ I&C Operator Error If one condensate pump trips during normal operation the STANDBY condensate pump starts with enough response time to avoid feedwater pump trip.
Failure would be detected by downstream instruments PIT-1009 A/B/C and FE/FIT-1010 A/B/C.
There is a temporary decrease in feedwater flow rate to the SGs. The remaining online pump runs out on its pump curve, but is not capable of supplying the full load flow rate requirements. As the standby condensate pump comes online, the system returns to normal operation.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-73 Revision 4.1 Condensate Polishing System Bypass Valve xx*-FW-AOV-0040 (normally closed, fail open)
- reserved for module number (01 - 12)
- 1) Bypasses condensate polishing system upon high condensate temperature.
A) Failure to Open Mechanical Electrical/ I&C A failure of the condensate polishing bypass valve to open upon a high condensate temperature signal causes the resin in the condensate polisher to be damaged.
Limit switches ZSO-0040 and ZSC-0040 position indication.
Failure of the condensate polishing system bypass valve could cause damage to the polishing resin. The effect this transient would have on the primary side is dependent on the cause of the increased condensate temperature.
If condensate temperature is too high and there is a risk of damaging polishing resin, operators can make the choice to shutdown the module, preserving the integrity of the polishers.
B) Partial Opening Partial opening of the bypass valve causes condensate to bypass the polishers resulting in degrading water chemistry.
Analyzers downstream of the condensate polishing system show increased amounts of contaminants in the CFWS. Operators are responsible for diagnosing the problem and making the correct actions to fix.
C) Spurious Opening Mechanical Electrical/ I&C Operator Error Spurious opening causes condensate to bypass the polishers resulting in degrading water chemistry.
Limit switches ZSO-0040 and ZSC-0040 position indication.
Reduced flow rate through FE-1013.
Large amount of condensate bypassing the condensate polishers could result in the CFWS being operated outside of water chemistry limits. Operators are responsible for making the decision to remain in operation based on water chemistry.
Condensate Polishing Skid xx*-FW-SKD-0013
- reserved for module number (01 - 12)
- 1) Maintains water chemistry limits by removing dissolved solids and by products of hydrazine reactions.
A) Failure resulting in polishing resin entering the feedwater system.
Mechanical Failure of the condensate polishing system resulting in resin entering the CFWS is captured in a downstream filter. A high pressure drop reading across the filter alerts operators to this occurrence and prompts a switch to the standby unit. The condensate polishing system is designed with two 100 percent capacity ion exchangers, so this switch does not result in a reactor trip.
Filters are located downstream of each condensate polisher. A high differential pressure indication across the filters indicates resin carry over from the polishers.
CFWS and primary side experience a temporary transient as flow is transferred from the online polisher to the standby polisher. As flow is returned to normal through the condensate polishing system, the CFWS and primary side return to steady state operations.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-74 Revision 4.1 Gland Steam Condenser xx*-TG-CND-0032
- reserved for module number (01 - 12)
- 1) Uses condensate to condense the low-pressure steam supplied to the turbine seals.
A) Tube Failure Mechanical Actions taken during a gland steam condenser (GSC) tube failure are dependent on the severity of the leak. For minor leaks, operators may decide to remain in operation.
Major tube failure of the GSC requires a turbine trip to prevent water from entering the turbine seals.
For a failure of the gland steam condenser the NuScale Power Module is taken offline through the use of the DHRS.
Level indication on the shell side of the gland steam condenser is the primary means of detecting gland steam condenser tube failure.
For a minor leak, the feedwater system is available and operating under normal conditions. As the leak increases in severity the decision to trip the turbine is an operator decision.
A substantial tube failure of the GSC results in the inability to supply steam to the turbine seals. Without this capability the turbine and the reactor are tripped. The condenser is also isolated from potential steam sources.
This incident is consistent with a loss of feedwater flow transient.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-75 Revision 4.1 Low-Pressure Feedwater Heater xx*-FW-HX-0019
- reserved for module number (01 - 12)
- 1) Heats condensate to increase NuScale Power Module thermal efficiency.
A) Shell Side Failure High.
Mechanical Electrical/ I&C Operator Error Failure of the LP FWH shell side in the high causes high level notifications. If the normal level control valve is not capable of reducing the water level in the heater, the emergency level control valve attempts to reduce level. At some high-high liquid level turbine water induction interlocks are initiated protecting the turbine from damage. Turbine water induction protection includes isolating the heater from its steam supply source. If this is done the temperature delivered to the SG is decreased.
If level control of the heater cannot be established operators make the decision to bypass the LP FWH on the condensate side.
This reduces the temperature of the feedwater entering the SGs.
Level indication on the shell side of the feedwater heater is the primary means of detecting level fluctuations on the shell sided of the LP FWH.
Decreasing feedwater temperature being supplied to the SGs results in the SG going through a power transient.
The higher level of heat removal from the SGs causes a decrease in primary side temperature. As the colder temperatures pass over the core the reactivity increases as does the reactor power level. If the temperature drops low enough the reactor trips based on a high reactor power set point.
Decrease in feedwater supply temperature is an AOO for a NuScale module.
B) Shell Side Failure Low Failure of the LP FWH shell side in the low causes low level notifications. The emergency level control valve and the normal level control valve modulate closed in an effort to increase the liquid level in the feedwater heater. Without an established water level in the heater, the feedwater supply temperature decreases.
If the problem persists operators are responsible for determining the problem and deciding the best course of action.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-76 Revision 4.1 Intermediate-Pressure Feedwater Heater xx*-FW-HX-0023
- reserved for module number (01 - 12)
- 1) Heats condensate to increase NuScale Power Module thermal efficiency.
A) Shell Side Failure High Mechanical Electrical/ I&C Operator Error Failure of the IP FWH shell side in the high causes high level notifications. If the normal level control valve is not capable of reducing the water level in the heater, the emergency level control valve attempts to reduce level. At some high-high liquid level turbine water induction interlocks are initiated protecting the turbine from damage. Turbine water induction protection includes isolating the heater from its steam supply source. If this is done the temperature delivered to the SG is decreased.
If level control of the heater cannot be established operators make the decision to bypass the IP FWH on the condensate side.
This reduces the temperature of the feedwater entering the SGs.
Level indication on the shell side of the feedwater heater is the primary means of detecting level fluctuations on the shell sided of the IP FWH.
Decreasing feedwater temperature being supplied to the SGs results in the SG going through a power transient.
The higher level of heat removal from the SGs causes a decrease in primary side temperature. As the colder temperatures pass over the core the reactivity increases as does the reactor power level. If the temperature drops low enough the reactor trips based on a high reactor power set point.
Decrease in feedwater supply temperature is an AOO for a NuScale module.
B) Shell Side Failure Low Failure of the IP FWH shell side in the low causes low level notifications. The emergency level control valve and the normal level control valve modulate closed in an effort to increase the liquid level in the feedwater heater. Without an established water level in the heater, the feedwater supply temperature decreases.
If the problem persists operators are responsible for determining the problem and deciding the best course of action.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-77 Revision 4.1 Short-Cycle Recirculation Flow Control Valve xx*-FW-AOV-0052 (normally closed, fail closed)
- reserved for module number (01 - 12)
- 1) Provides condensate pump minimum flow protection.
A) Failure to Open Mechanical Electrical/ I&C Short-cycle recirculation flow control valve acts as the primary means of minimum flow protection for the condensate pumps during normal operation. A failure of the short-cycle recirculation flow control valve causes the redundant condensate pump minimum flow protection lines to open.
Low flow rate measured by FE-1010 A/B/C Position switches ZSO-0038 A/B/C or ZSC-0038 A/B/C indicating PIT-1028 A/B/C measuring low suction pressure.
ZT-0052 shows incorrect valve position vs expected position.
If this valve is being commanded to open, then a plant transient is taking place that is forcing the condensate pump to approach minimum flow conditions. This incident is consistent with a loss of feedwater flow if the reactor is at full power. During a loss of feedwater flow, the primary side temperature and pressure increases as the amount of heat removed decreases. The reactor trips due to a high primary side pressure set point.
Loss of feedwater is an AOO for a NuScale module.
B) Partial Opening Partial opening of the short-cycle recirculation valve could cause the redundant condensate pump minimum flow protection lines to open.
C) Spurious Closure Mechanical Electrical/ I&C Operator Error Spurious closure of the short-cycle recirculation valve during condensate pump protection operations causes the redundant condensate pump minimum flow protection lines to open.
D) Spurious Opening Spurious opening of the short-cycle recirculation valve during normal operation results in condensate being diverted back to the condenser. This reduces the flow rate and the suction pressure supplied to the feedwater pumps. There is a reduced feedwater flow rate to the steam generators.
PIT-1028 A/B/C measuring low suction pressure.
Flow rate through FE-1010 A/B/C shows an increase over normal amount.
ZT-0052 shows incorrect valve position vs expected position.
As the feed flow rate and pressure supplied to the feedwater pumps decreases the VFDs on the feedwater pumps begin to speed the pumps up to maintain normal flow to the SGs. If supply pressure drops to the set point for low supply pressure protection of the feedwater pumps the feedwater pumps trip. This results in a loss of feedwater, and the tripping of both the NuScale Power Module and the turbine.
Loss of feedwater is an AOO for a NuScale module.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-78 Revision 4.1 Feedwater Pump xx*-FW-P-0027 A/B/C
- reserved for module number (01 - 12)
A) Failure to Start Mechanical Electrical/ I&C Failure of a feedwater pump to start after one of the two operational pumps trip could result in a reactor trip due to high pressurizer pressure. If feedwater flow to the reactor can be maintained via the online feedwater pump and reactor automation controls primary side parameters correctly, safety-related portions of the NSSS should not be affected. If the reactor trips due to decreased feedwater flow, the safety systems are available for decay heat removal.
Low pressure reading on feedwater pump discharge PIT-1029 A/B/C Low feedwater flow rate at downstream flow instrument FE-1030 A/B/C Decreased feedwater flow rate as measured by FE-1036 and FE-2036.
If the primary side temperature and pressure result in a reactor trip due to the high pressurizer pressure set point cause DHRS actuation/SG isolation, decay heat is removed via the DHRS exchanger. No safety-related NSSS equipment is prevented from performing its safety function by a feedwater pump trip.
Loss of feedwater is an AOO for a NuScale module.
B) Pump Trip Mechanical Electrical/ I&C Operator Error Pump trip causes a temporary reduced flow rate to the SGs while the standby feedwater pump starts up.
The standby feedwater pump is designed to startup without causing a reactor trip. DHRS is not actuated and no safety-related portions of the NSSS are affected.
C) VFD failure of both operating VFDs resulting in increased pump speed operations.
Mechanical Electrical/ I&C Increased feedwater flow rate to the SGs increases the amount of heat removed from the RCS via the secondary side.
High feedwater flow rate at instruments FE-1030 A/B/C Increased feedwater flow rate as measured by FE-1036 and FE-2036.
Low primary side temperature.
Decreased RCS temperature causes the core reactivity to increase, in turn increasing the reactor output. If reactor power increases above some set point without actions being taken (e.g.,
reduced turbine load, increased pressurizer spray) reactor trips due to high reactor power output. DHRS, FWIV and MSIV are available to maintain SG water level and remove decay heat following a reactor trip.
Increase in feedwater flow is an AOO for a NuScale module.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-79 Revision 4.1 Feedwater Pump xx*-FW-P-0027 A/B/C
- reserved for module number (01 - 12)
(cont)
(cont)
D) VFD failure increasing the pumping speed of operating feedwater pump.
Mechanical Electrical/ I&C Increased speed for one of the two feedwater pumps results in the other operating pump being ramped down to the appropriate speed to return flow to steady state values.
Uneven flow rate can be determined from measurements from instruments FE-1030 A/B/C As the one pump begins to ramp up in speed, the flow rate to the SGs increases temporarily. The MCS reduces the speed of the other operating feedwater pump to an acceptable level returning the feedwater flow rate to the steady state value.
E) VFD failure of both operating VFDs resulting in decreased pump speed operations.
Decreased feedwater flow rate to the SGs.
As the feedwater flow begins to decrease the supply pressure to the feedwater pumps begins to increase. If the flow rate falls below some low flow set point, the third feedwater pump is started automatically by the MCS.
Inability to restore normal feedwater flow rate to the SGs results in reduced power operations or NuScale Power Module trip based on decision from operations.
Low feedwater flow rate measured by FE-1030 A/B/C Decreased feedwater flow rate measured by FE-1036 and FE-2036.
Increase in primary side temperature Decreased feedwater flow rate causes the primary side temperature and pressure to increase as the amount of heat removed from the primary side decreases. If a third feedwater pump is started and flow can be returned to normal operating conditions the system remains online. If flow cannot be returned to normal, operation can be continued at a reduced power or module can be removed from operation due to a loss of feedwater flow. If the loss of feedwater flow is substantial, the reactor could trip due to a high primary side pressure set point.
Loss of feedwater is an AOO for a NuScale module.
F) VFD failure decreasing the pumping speed of one operating feedwater pump.
When the VFD fails, decreasing the speed of one of the two pumps, the control system attempts to increase the speed of the other online pump. There is a limit to how much the second pump can be ramped up, while there is no limit to the reduced speed of the affected pump. If the feedwater flow rate drops enough, the standby pump starts in order to make up the difference in flows.
Uneven flow rate can be determined from measurements from instruments FE-1030 A/B/C The primary side temperature and pressure is temporarily affected as the MCS changes the feedwater pump speeds to accommodate the decreased speed of one of the two pumps.
If the feedwater flow drops too rapidly it could result in a reactor trip due to high primary side pressure trip point.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-80 Revision 4.1 Feedwater Pump Minimum Flow Protection Flow Control Valve xx*-FW-AOV-0056 A/B/C (normally closed, fail closed)
- reserved for module number (01 - 12)
- 1) Modulates open based on measurement s from FE-1030 A/B/C to provide minimum flow protection to the feedwater pumps.
A) Failure to Open Mechanical Electrical/ I&C Failure of the feedwater pump minimum flow protection valve to open causes feedwater pump damage and results in a feedwater pump trip. A pump trip of both of the running feedwater pumps would cause a reactor trip due to insufficient feedwater flow and pressure.
FE-1030 A/B/C is used to determine a failure of this valve.
Valve position can be identified using ZT-0056 A/B/C No safety-related feedwater equipment is affected by a feedwater pump trip based on the failure of the minimum flow protection valves. Both SGs are still available for decay heat removal.
Loss of feedwater is an AOO for a NuScale module.
B) Partial Opening A partial opening of the feedwater pump minimum flow control valve, instead of full opening could cause the affected feedwater pump to overheat leading to a single feedwater pump trip C) Spurious Closure Mechanical Electrical/ I&C Operator Error Spurious closure of the minimum flow protection valves could cause the feedwater pumps to trip. If the two operational feedwater pumps trip, the reactor trips.
D) Spurious Opening Spurious opening of the minimum flow protection valve/valves results in a reduced feedwater flow rate to the SGs. Reduced feedwater flow rates result in an increased RCS temperature and pressure.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-81 Revision 4.1 High-Pressure Feedwater Heater xx*-FW-HX-0031
- reserved for module number (01 - 12)
- 1) Heats condensate to increase NuScale Power Module thermal efficiency.
A) Shell Side Failure High Mechanical Electrical/ I&C Operator Error Failure of the HP FWH shell side in the high causes high level notifications. If the normal level control valve is not capable of reducing the water level in the heater, the emergency level control valve attempts to reduce level. At some high-high liquid level turbine water induction interlocks are initiated protecting the turbine from damage. Turbine water induction protection includes isolating the heater from its steam supply source. If this is done the temperature delivered to the SG is decreased.
If level control of the heater cannot be established operators make the decision to bypass the HP FWH on the condensate side.
This reduces the temperature of the feedwater entering the SGs.
Level indication on the shell side of the feedwater heater is the primary means of detecting level fluctuations on the shell sided of the HP FWH.
Decreasing feedwater temperature being supplied to the SGs results in the SG going through a power transient.
The higher level of heat removal from the SGs causes a decrease in primary side temperature. As the colder temperatures pass over the core the reactivity increases as does the reactor power level. If the temperature drops low enough the reactor trips based on a high reactor power set point.
Decrease in feedwater supply temperature is an AOO for a NuScale module.
B) Shell Side Failure Low Failure of the HP FWH shell side in the low causes low level notifications. The emergency level control valve and the normal level control valve modulate closed in an effort to increase the liquid level in the feedwater heater. Without an established water level in the heater, the feedwater supply temperature decreases.
If the problem persists operators are responsible for determining the problem and deciding the best course of action.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-82 Revision 4.1 Long-Cycle Recirculation Flow Control Valve xx*-FW-AOV-0060 (normally closed, fail closed)
- reserved for module number (01 - 12)
- 1) Opens for flow path during system flushing during startup.
During normal operation the valve is normally closed A) Failure to Close Mechanical Electrical/ I&C There are two valves in series on the long cycle recirculation path. One for isolation purposes, one for flow control. If AOV-0060 fails to close, AOV-0059 closes preventing condensate from returning to the condenser instead of going to the steam generator.
Position of valve as measured by ZT-0060.
When the reactor is critical during normal operation, the long cycle recirculation path is not in use.
Therefore, a failure to open event or a partial opening of one of the two valves is not analyzed.
Because there are two valves operating in series, a failure of one of the two valves does not result in a CFWS transient.
B) Spurious Opening Mechanical Electrical/ I&C Operator Error There are two valves in series on the long cycle recirculation path. One for isolation purposes, one for flow control. If AOV-0060 spuriously opens, AOV-0059 remains closed preventing condensate from returning to the condenser instead of going to the steam generator.
Long-Cycle Cleanup Air Operated Valve xx*-FW-AOV-0059 (normally closed, fail closed)
- reserved for module number (01 - 12)
- 1) Opens for flow path during system flushing during startup.
During normal operation the valve is normally closed A) Failure to Close Mechanical Electrical/ I&C There are two valves in series on the long cycle recirculation path. One for isolation purposes, one for flow control. If AOV-0059 fails to close, AOV-0060 closes preventing condensate from returning to the condenser instead of going to the steam generator.
Position of valve as measured by ZSO-0059 and ZSC-0059.
B) Spurious Opening Mechanical Electrical/ I&C Operator Error There are two valves in series on the long cycle recirculation path. One for isolation purposes, one for flow control. If AOV-0059 spuriously opens, AOV-0060 remains closed preventing condensate from returning to the condenser instead of going to the steam generator.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-83 Revision 4.1 Feedwater Regulating Valve xx*-FW-AOV-0134 xx*-FW-AOV-0234 (normally open, fail closed)
- reserved for module number (01 - 12)
- 1) Controls feedwater flow to the SGs during low flow operations below the feedwater pump VFDs abilities.
A) Spurious Opening Mechanical Electrical/ I&C Operator Error Uneven feedwater flow rate to one of the two SG headers.
Feedwater flow rate as measured by FE-1036 and FE-2036.
Position indication by ZT-0134 and ZT-0234.
Primary side temperature and pressure.
During startup, and during other low feedwater flow rate operations, the spurious opening of the FWRV results in an increase in flow through the spuriously opened path. If the increase in flow to the SG results in over cooling of the primary side the reactor trips due to high reactor power.
With the inability to control the feedwater flow rate to one of the two steam generators, the DHRS is actuated and the NuScale Power Module is isolated for decay heat removal.
No safety related portions of the NSSS are affected, as SGs can be isolated by the FWIVs. Decay heat is removed by the DHRS exchanger.
B) Spurious Closing Mechanical Electrical/ I&C Operator Error No feedwater flow to one of the two SG headers.
Feedwater flow rate as measured by FE-1036 and FE-2036.
Position indication by ZT-0134 and ZT-0234.
Primary side temperature and pressure.
During startup, and during other low feedwater flow rate operations, the spurious closing of the FWRV results in the termination of flow through one of the two SGs. There is no plan to maintain operation if one of the two SGs is unavailable. If the decrease in feedwater flow does not cause a reactor trip due to high pressure on the primary side, the decision is made by operators to trip the reactor due to regulating valve failure.
No safety related portions of the NSSS are affected, as SGs can be isolated by the FWIVs. Decay heat is removed by the DHRS exchanger.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-84 Revision 4.1 Feedwater Regulating Valve xx*-FW-AOV-0134 xx*-FW-AOV-0234 (normally open, fail closed)
- reserved for module number (01 - 12)
(cont)
- 2) Provides redundant isolation for FWIV actuation events.
A) Failure to Close Mechanical Electrical/ I&C Not available for containment isolation, not providing redundant containment isolation.
Position indication by ZT-0134 and ZT-0234.
Position indication from ZSO-0134 A/B, ZSC-0134 A/B, ZSO-0234 A/B, ZSC-0234 A/B The FWIVs are the primary method for providing steam generator isolation.
There is no effect on reactor safety if the FWRVs fail with the FWIVs operating correctly. Additional protection is provided by the feedwater safety and nonsafety check valves.
B) Slow Closing C) Spurious Opening Mechanical Electrical/ I&C Operator Error Feedwater Check Valve xx*-FW-CKV-0135/
0235
- 1) Provides redundant isolation for safety-related check valve.
A) Failure to Close Mechanical Not available for containment isolation, not providing redundant containment isolation or maintaining level in the steam generators.
N/A The safety related check valve is the primary method for maintaining steam generator inventory during a feedwater line break. There is no effect on reactor safety if the feedwater check valve were to fail with the safety related check valve operating correctly.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-85 Revision 4.1 Condensate Header Emergency Rejection Level Control Valve xx*-FW-AOV-0044 (normally closed, fail closed)
- reserved for module number (01 - 12)
- 1) Provides emergency level control of condensate inventory.
A) Spurious Opening Mechanical Electrical/ I&C Operator Error Condensate flow is diverted to the condensate storage tank. Low condensate flow and pressure is delivered to the feedwater pumps and subsequently the steam generators. The feedwater pumps increase in speed in an attempt to make up the difference in flow rate. It is possible that the third condensate pump is started to ensure adequate flow is supplied to the feedwater pumps.
Condenser level reading by LIT-1001 A/B/C Valve position as measured by ZT-0044 Feedwater Pump Supply Pressure as measured by PIT-1028 A/B/C Safety-related portions of the NSSS remain available for decay heat removal if reactor trips without the ability to remove decay heat with the CFWS. No impact on the primary isolation valves or the DHRS exchanger which remain available to remove decay heat.
B) Fail to open Mechanical Electrical/ I&C If this valve fails to open, level in the condenser rises (i.e., major tube rupture in the condenser). If level rises above high-high set point, the CFWS is tripped, and the reactor must be isolated.
Condenser level reading by LIT-1001 A/B/C Valve position as measured by ZT-0044 Condensate Header Normal Rejection Level Control Valve xx*-FW-AOV-0046 (normally closed, fail closed)
- reserved for module number (01 - 12)
- 1) Provides normal level control of condensate inventory.
A) Spurious opening Mechanical Electrical/ I&C Operator Error Condensate flow is diverted to the condensate storage tank. Low condensate flow and pressure is delivered to the feedwater pumps and subsequently the steam generators. The feedwater pumps increase in speed in an attempt to make up the difference in flow rate. It is possible that the third condensate pump is started to ensure adequate flow is supplied to the feedwater pumps.
Condenser level reading by LIT-1001 A/B/C Valve position as measured by ZT-0046 Feedwater Pump Supply Pressure as measured by PIT-1028 A/B/C Safety-related portions of the NSSS remain available for decay heat removal if reactor trips without the ability to remove decay heat with the CFWS. No impact on the primary isolation valves or the DHRS exchanger which remain available to remove decay heat.
B) Fail to open Mechanical Electrical/ I&C Condensate level in the main condenser rises. High condenser level alarms go off in the control room. The condensate header emergency rejection level control valve (AOV-0044) opens, lowering the level in the condenser Condenser level reading by LIT-1001 A/B/C Valve position as measured by ZT-0044 None Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-86 Revision 4.1 Main Condenser Hotwell Emergency Make up Level Control Valve xx*-FW-AOV-0070 (normally closed, fail closed)
- reserved for module number (01 - 12)
- 1) Provides emergency level control of condensate inventory.
A) Spurious Opening Mechanical Electrical/ I&C Operator Error Condensate is gravity feed to the main condenser hotwell. High level in the condenser causes the condensate header normal rejection level control valve (LCV-0071) to actuate open to reduce hotwell level Condenser level reading by LIT-1001 A/B/C Valve position as measured by ZT-0070 Safety-related portions of the NSSS remain available for decay heat removal if reactor trips without the ability to remove decay heat with the CFWS. No impact on the primary isolation valves or the DHRS exchanger which remain available to remove decay heat.
B) Fail to open Mechanical Electrical/ I&C Main condenser hotwell level continues to fall. Low condenser hotwell level causes MCS to close both the condensate header normal and emergency level control valves (AOV-0044 and AOV-0046). If level continues to drop, condensate pumps could be tripped based on low NPSH due to low condenser level.
Main Condenser Hotwell Normal Make up Flow Control Valve xx*-FW-AOV-0069 (normally closed, fail closed)
- reserved for module number (01 - 12)
- 1) Provides normal level control of condensate inventory.
A) Spurious Opening Mechanical Electrical/ I&C Operator Error Condensate is gravity feed to the main condenser hotwell. High level in the condenser causes the condensate header normal level control valve (AOV-0046) to actuate open to reduce hotwell level.
Condenser level reading by LIT-1001 A/B/C Valve position as measured by ZT-0044 None C) Fail to open Mechanical Electrical/ I&C Main condenser hotwell level continues to fall. Low condenser hotwell level measurements cause the main condenser hotwell emergency make up level control valve (AOV-0070) to open.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-87 Revision 4.1 Condensate Storage Tank Make up Level Control Valve xx*-FW-AOV-0064 (normally closed, fail closed)
- reserved for module number (01 - 12)
- 1) Provides level control of the condensate storage tank inventory.
A) Spurious Opening Mechanical Electrical/ I&C Operator Error Cause high level alarms to trigger for the Condensate storage tank. It is possible that the tank overflows.
Level indication as measured by LIT-1040 and LIT-1041 None C) Fail to open Mechanical Electrical/ I&C Level in the condensate storage tank drops as no make up water is being supplied to the condensate and feedwater system. If the level in the condenser continues to fall operators are responsible for determining the cause and taking the appropriate actions.
Feedwater Lines Outside of Containment (Including ball joints).
Supplies feedwater to the steam generators A) Main feedwater header line break outside of containment Mechanical Operator Error A major feedwater header line break outside of containment causes a reactor trip.
Increased CFWS flow rate.
Decreased CFWS header pressure Rapid increase in primary side temperature and pressure.
For feedwater line breaks, the decreased amount of heat removal results in a rapid increase in RCS temperature. This transient results in a reactor trip due to high pressurizer pressure signal.
Flow reversal is prevented by the feedwater check valves and the DHRS is actuated to remove decay heat.
Feedwater line break outside containment is an accident condition for a NuScale module.
Table 10.4-18: Condensate and Feedwater System Failure Modes and Effects Analysis (Continued)
Component Identification Function Failure Mode Failure Mechanism Effect on the Condensate and Feedwater System Method of Failure Detection Remarks
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-88 Revision 4.1 Table 10.4-19: Condensate and Feedwater System Instrumentation Equipment Name Monitored Parameter (NPMs)
Local Display Signal To MCS Condensate pump inlet temperature indicating transmitter Condensate pump suction temperature (°F)
Yes Yes Condensate pump startup strainer pressure differential indicating transmitter Equipment pressure drop (psid)
Yes No Condensate pump inlet pressure indicating transmitter A/B/C Condensate pump suction pressure (psia)
Yes Yes Condensate pump outlet flow meter A/B/C Condensate pump discharge flow rate (gpm)
No No Condensate outlet flow transmitter A/B/C (redundant)
Condensate pump discharge Flow Rate (gpm)
Yes Yes Condensate pump outlet pressure indicating transmitter A/B/C Condensate pump discharge pressure (psia)
Yes Yes Condensate conductivity analyzer Micro Siemens per centimeter
@ 25°C (S/cm)
Yes Yes Condensate flow meter Condensate flow rate (gpm)
No No Condensate flow indicating transmitter Condensate flow rate (gpm)
Yes Yes Condensate oxygen concentration analyzer ppb No Yes Gland steam condenser inlet pressure indicating transmitter Piping system pressure (psia)
Yes Yes Gland steam condenser outlet temperature indicating transmitter Condensate temperature (°F)
Yes Yes Gland steam condenser outlet pressure indicating transmitter Piping system pressure (psia)
Yes Yes Condensate storage tank inlet flow meter Condensate flow rate (gpm)
No No Condensate storage tank inlet flow transmitter Condensate flow rate (gpm)
Yes Yes LP-FWH outlet temperature indicator transmitter Condensate temperature (°F)
Yes Yes LP-FWH outlet pressure indicating transmitter Piping system pressure (psia)
Yes Yes IP-FWH outlet temperature indicator/transmitter Condensate temperature (°F)
Yes Yes IP FWHIP-FWH outlet pressure indicating transmitter Piping system pressure (psia)
Yes Yes Short cycle cleanup flow control valve position indicator Flow control valve position
(%)
No Yes Feedwater pump inlet pressure indicating transmitter piping system pressure (psia) Yes Yes Feedwater pump inlet manual valve open position switch valve not fully open No Yes Feedwater pump outlet pressure indicating transmitter A/B/C Piping system pressure (psia)
Yes Yes Feedwater pump outlet flow meter A/B/C Feedwater flow rate (gpm)
No Yes Feedwater pump outlet flow indicator/
transmitter Feedwater flow rate (gpm)
Yes Yes Feedwater pumps minimum flow protection flow control valve open position transmitter A/B/C Flow control valve position
(%)
No Yes HP-FWH outlet temperature indicating transmitter Feedwater temperature Yes Yes Long cycle cleanup flow control valve position transmitter Flow control valve position
(%)
No Yes Feedwater header pressure indicating transmitter Piping system pressure (psia)
Yes Yes Feedwater header flow meter A/B/C Feedwater flow rate (gpm)
No No Feedwater header flow meter indicating transmitter (duplicate)
Feedwater flow rate (gpm)
Yes Yes
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-89 Revision 4.1 Feedwater regulating valve A/B position indicating transmitter Flow control valve position
(%)
No Yes Feedwater regulating valve A/B position switch open indicators Valve not fully open No Note 1 Feedwater regulating valve A/B position switch closed indicators Valve not fully closed No Note 2 Condensate header emergency rejection level control valve position indicating transmitter Level control valve position
(%)
No Yes Condensate header normal rejection level control valve position indicating transmitter Level control valve position
(%)
No Yes Condensate storage tank level indicating transmitter Vessel level (inches of H2O)
Yes Yes Condensate makeup conductivity analyzer Condensate conductivity
[microsiemens per centimeter
@ 25°C (S/cm)]
Yes Yes Condensate storage tank makeup level control valve position indicating transmitter Level control valve position
(%)
No Yes Condensate pump inlet manual valve position switch open Valve not fully open No Yes Long cycle cleanup air operated valve position switch open Valve not fully open No Yes Long cycle cleanup air operated valve position switch closed Valve not fully closed No Yes Condensate pump redundant minimum flow protection valve position switch open Valve not fully open No Yes Condensate pump redundant minimum flow protection valve position switch closed Valve not fully closed No Yes Long cycle recirculation flow element Flow rate (lb/hr)
No Yes Long cycle recirculation flow indicating transmitter Flow rate (lb/hr)
Yes Yes FWS differential pressure transmitters SG inventory No Yes Notes:
(1) Signal to MPS for valve timing technical specification.
(2) Signal to Safety Display & Indication (SDI, system E014), via MPS to indicate that the FWRV is fully closed.
Table 10.4-19: Condensate and Feedwater System Instrumentation (Continued)
Equipment Name Monitored Parameter (NPMs)
Local Display Signal To MCS
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-90 Revision 4.1 Table 10.4-20: Auxiliary Boiler System Component Design Parameters Parameter High-Pressure Auxiliary Boiler Low-Pressure Auxiliary Boiler Fuel Site-specific Site-specific Number of boilers 2
1 Steam supply pressure 1100 psig 500 psig Steam rate and temperature 18,000 lb/hr at 575°F 4,600 lb/hr at 575°F Feedwater pump rate 80 gpm 10 gpm Pipe code / material ASME B31.1 / SA-335 P11 or equivalent ASME B31.1 / SA-335 P11 or equivalent Estimated blowdown (demineralized feed, 10 cycles) 17.3 gpm 9.2 gpm Boiler code / material ASME Boiler and Pressure Vessel Code,Section I, Power Boilers ASME Boiler and Pressure Vessel Code,Section I, Power Boilers
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-91 Revision 4.1 Table 10.4-21: Auxiliary Boiler System Instrumentation System Type Location Indication Local MCR HP Radiation ind trans Exit of MHS heat exchangers Yes Yes HP Valve open Exit of MHS heat exchangers No Yes HP Valve closed Exit of MHS heat exchangers No Yes HP Valve pos trans Demineralized water supply No Yes HP Radiation ind trans Vent of high-pressure condensate tank pressure regulating valve Yes Yes HP Valve pos trans High-pressure condensate tank pressure regulating valve No Yes HP Level indicator trans High-pressure condensate tank Yes Yes HP Pressure ind trans High-pressure condensate tank Yes Yes HP Valve open Steam supply from high-pressure boiler A No Yes HP Valve closed Steam supply from high-pressure boiler A No Yes HP Valve open Steam supply from high-pressure boiler B No Yes HP Valve closed Steam supply from high-pressure boiler B No Yes HP Pressure ind trans High-pressure steam supply header Yes Yes HP Temp ind trans High-pressure steam supply header Yes Yes HP Valve open Supply to MHS heat exchangers No Yes HP Valve closed Supply to MHS heat exchangers No Yes HP Flow ind trans Blowdown from boiler B Yes Yes HP Valve pos trans Blowdown from boiler B No Yes HP Valve open Blowdown from boiler B to PSS No Yes HP Valve closed Blowdown from boiler B to PSS No Yes HP Flow ind trans Blowdown from boiler A Yes Yes HP Valve pos trans Blowdown from boiler A No Yes HP Valve open Blowdown from boiler A to PSS No Yes HP Valve closed Blowdown from boiler A to PSS No Yes LP Flow ind trans Main Steam/ABS supply to TGS gland steam Yes Yes LP Pressure ind trans Main Steam/ABS supply to TGS gland steam Yes Yes LP Temp ind trans Main Steam/ABS supply to TGS gland steam Yes Yes LP Valve pos trans Cross over from HP to LP system No Yes LP Pressure ind trans Cross over from HP to LP system Yes Yes LP Temp ind trans Cross over from HP to LP system Yes Yes LP Valve pos trans Demineralized water supply No Yes LP Radiation ind trans Vent of low-pressure condensate tank pressure regulating valve Yes Yes LP Valve pos trans Low-pressure condensate tank pressure regulating valve No Yes LP Level indicator trans Low-pressure condensate tank Yes Yes LP Pressure ind trans Low-pressure condensate tank Yes Yes LP Valve open Steam supply from low-pressure boiler No Yes LP Valve closed Steam supply from low-pressure boiler No Yes LP Flow ind trans Blowdown from LP boiler Yes Yes LP Valve pos trans Blowdown from LP boiler No Yes LP Valve open Blowdown from LP boiler to PSS No Yes LP Valve closed Blowdown from LP boiler to PSS No Yes LP Valve open Cross feed with MS to TGS gland seals No Yes LP Valve closed Cross feed with MS to TGS gland seals No Yes LP Valve open Feed to TGS gland seals No Yes LP Valve closed Feed to TGS gland seals No Yes
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-92 Revision 4.1 Table 10.4-22: Not Used
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-93 Revision 4.1 Table 10.4-23: Feedwater Treatment System Component Design Data Item Value Hydrazine tank (oxygen scavenging)
Volume Site-specific Material Type 304 stainless steel Amine tank (pH control)
Volume Site-specific Material Type 304 stainless steel Pumps Material Type 316 stainless steel Type Diaphragm simplex-type Flow rate Variable
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-94 Revision 4.1 Table 10.4-24: Feedwater Treatment System Instrumentation Equipment Name Monitored Parameter (Units) Local Display Signal to MCS Feedwater header oxygen analyzer ppb Yes Yes Mass hydrazine addition flow control valve Valve position No Yes Mass amine addition flow control valve Valve position No Yes Shutdown hydrazine addition flow element Flow rate (lb/hr)
No Yes Shutdown hydrazine addition flow indicating transmitter Flow rate (lb/hr)
Yes Yes Shutdown amine addition flow element Flow rate (lb/hr)
No Yes Shutdown amine addition flow indicating transmitter Flow rate (lb/hr)
Yes Yes
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-95 Revision 4.1 Figure 10.4-1: Main Condenser Piping and Instrumentation Diagram Main Condenser TG exhaust steam Main steam deaerator TG bypass FW heater vents Seal separator Seal water system level control Process sampling Feedwater heater emergency drains LP FWH drain Condensate pump vents Gland steam condenser drain Main steam line drains Condenser air removal Short cycle recirculation Condensate pumps Long cycle recirculation Feedwater pumps Auxiliary boiler system Condensate emergency makeup Condensate normal makeup Process sampling Condensate pumps Hydrazine addition Demineralized water Amine addition Drain Vent CFWS CARS CFWS CARS CFWS PSS CFWS HVD CFWS HVD CFWS TGS CFWS MSS HVD CFWS TGS CFWS MSS CFWS PI TI AI LI CFWS FWTS FWS FWTS FE FE FE TI FE ABS CFWS Condensate polisher recirculation FE MSS CFWS FE Notes:
1.
For simplicity, a single instrument of each type is shown in each location.
CFWS DWS PSS CFWS 1"-3/4" CARS CFWS
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-96 Revision 4.1 Figure 10.4-2: Condenser Air Removal System Piping and Instrumentation Diagram Condenser Air Removal Liquid Ring Vacuum Pump Condenser Air Removal Liquid Ring Vacuum Pump Condenser Air Removal Seal Water Heat Exchanger Condenser Air Removal Seal Water Heat Exchanger Condenser Air Removal Seal Water Separator Tank Condenser Air Removal Seal Water Separator Tank LI LI From Main Condenser To Atmosphere RE To Main Condenser From Site Cooling Water To Site Cooling Water From Site Cooling Water To Site Cooling Water From Demineralized Water System TI TI Notes:
- 1. System vents and drains not shown. Drains go to balance of plant drain.
- 2. Orifices not shown.
- 3. Additional instrumentation not shown.
4.Tank isolation valves are manually controlled from Control Room during emergency operations.
Gaseous Effluent Discharge Radiation Monitor To Main Condenser To Main Condenser S
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-97 Revision 4.1 Figure 10.4-3: Circulating Water System Piping and Instrumentation Diagram (Typical of 2)
BLOWDOWN TO UWS COOLING TOWER
INTAKE STRUCTURE 3 BAYS, 3 PUMPS, 3 SCREENS 6 CONDENSERS (NOT PART OF CW SYSTEM)
MAKEUP FROM UWS LC AC SOLIDS CIRCULATING WATER SYSTEM CHEMICAL TREATMENT BUILDING
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-98 Revision 4.1 Figure 10.4-4a: Auxiliary Boiler System Piping and Instrumentation Diagram From MHS Heat Exchangers High Pressure Boiler (1100 psi)
To MHS Heat Exchangers To Low Pressure Boiler (500 psi)
High Pressure Boilers (1100 psi)
ABS HP Feed Pumps High Pressure Boiler Condensate Tank Flash Tank RE RE Chemical Addition Skid Notes:
Vents not shown.
Drainage to balance of plant drains not shown.
Component recirculation loops not shown Deaerator not shown Additional instrumentation not shown TIT PIT To Process Sampling To Process Sampling To Common ABS Blowdown Line To Atmosphere To Atmosphere From Demineralized Water
NuScale Final Safety Analysis Report Other Features of Steam and Power Conversion System Tier 2 10.4-99 Revision 4.1 Figure 10.4-4b: Auxiliary Boiler System Piping and Instrumentation Diagram PRESSURE RELIEF VALVES FOR HP HEADER FIT PIT TIT TO TURBINE GLAND SEALS TO CONDENSER SPARGER FROM MAIN STREAM ONE UNIT SHOWN, TYPICAL FOR ALL UNITS FROM HIGH PRESSURE BOILER TO ATMOSPHERE RE TIT PIT FROM DEMINERALIZED WATER PIT TO ATMOSPHERE LOW PRESSURE BOILER (500 PSI)
TO PROCESS SAMPLING TO COMMON ABS BLOWNDOWN LINE LOW PRESSURE BOILER CONDENSATE TANK LIT ABS LP FEED PUMPS CHEMICAL ADDITION SKID NOTES:
VENTS NOT SHOWN.
DRAINAGE TO BALANCE OF PLANT.
DRAINS NOT SHOWN.
COMPONENT RECIRCULATION LOOPS NOT SHOWN DEAERATOR NOT SHOWN.
ADDITIONAL INSTRUMENTATION NOT SHOWN.