NG-17-0111, Duane Arnold Energy Center, Revision 24 to Updated Final Safety Analysis Report, Chapter 10, Steam and Power Conversion
Text
UFSAR/DAEC-1 Chapter 10: STEAM AND POWER CONVERSION TABLE OF CONTENTS 10-i Revision 17 - 10/03 Section Title Page
10.1
SUMMARY
DESCRIPTION ...................................................................... 10.1-1
10.2 TURBINE-GENERATOR ........................................................................... 10.2-1
10.2.1 Design Basis ............................................................................................. 10.2-1 10.2.1.1 Power Generation Objective .................................................................. 10.2-1 10.2.1.2 Power Generation Design Basis ............................................................ 10.2-1 10.2.2 Description ................................................................................................ 10.2-1 10.2.3 Turbine Disk Integrity .............................................................................. 10.2-4 10.2.3.1 Design .................................................................................................... 10.2-4 10.2.3.2 Inservice Inspection ............................................................................... 10.2-4 10.2.4 Evaluation ................................................................................................ 10.2-5
10.3 MAIN STEAM SUPPLY SYSTEM ............................................................ 10.3-1
10.3.1 Design Bases ............................................................................................. 10.3-1 10.3.1.1 Power Generation Objective .................................................................. 10.3-1 10.3.1.2 Power Generation Design Bases ............................................................ 10.3-1 10.3.1.3 Safety Design Basis ............................................................................... 10.3-1 10.3.2 Description ................................................................................................ 10.3-1 10.3.3 Safety Evaluation ...................................................................................... 10.3-3 10.3.4 Inspection and Testing .............................................................................. 10.3-3 10.3.5 Steam and Feedwater Materials ................................................................ 10.3-4 10.3.5.1 Fracture Toughness ................................................................................ 10.3-4
10.3.5.2 Material Selection and Fabrication ........................................................ 10.3-5
10.4 OTHER FEATURES OF STEAM AND POWER CONVERSION SYSTEM .................................................................................................... 10.4-1 10.4.1 Main Condenser ....................................................................................... .10.4-1 10.4.1.1 Design Bases .......................................................................................... 10.4-1 10.4.1.1.1 Power Generation Objective ............................................................... 10.4-1 10.4.1.1.2 Power Generation Design Bases ......................................................... 10.4-1 10.4.1.2 Description ............................................................................................ 10.4-1 10.4.2 Main Condenser Gas Removal System ..................................................... 10.4-2 10.4.2.1 Design Bases ......................................................................................... .10.4-2 10.4.2.1.1 Power Generation Objective ............................................................... 10.4-2 10.4.2.1.2 Power Generation Design Bases. ....................................................... 10.4-2 10.4.2.2 System Description ................................................................................ 10.4-2 UFSAR/DAEC-1 Chapter 10: STEAM AND POWER CONVERSION TABLE OF CONTENTS 10-ii Revision 17 -10/03 Section Title Page
10.4.2.2.1 Steam Jet Air Ejector .......................................................................... 10.4-2 10.4.2.2.2 Mechanical Vacuum Pump ................................................................. 10.4-2 10.4.3 Turbine Gland Sealing System ................................................................. 10.4-3 10.4.3.1 Design Bases ......................................................................................... .10.4-3 10.4.3.1.1 Power Generation Objective ............................................................... 10.4-3 10.4.3.1.2 Power Generation Design Bases ......................................................... 10.4-3 10.4.3.2 Description ............................................................................................. 10.4-3 10.4.4 Turbine Bypass System............................................................................. 10.4-3 10.4.4.1 Design Bases ........................................................................................ 10.4-3 10.4.4.1.1 Power Generation Objective ............................................................... 10.4-3 10.4.4.1.2 Power Generation Design Bases ......................................................... 10.4-3 10.4.4.1.3 Safety Design Bases ............................................................................ 10.4-4 10.4.4.2 Description ............................................................................................. 10.4-4 10.4.5 Circulating Water System ........................................................................ .10.4-4 10.4.5.1 Design Bases ........................................................................................ 10.4-4 10.4.5.1.1 Power Generation Objective ............................................................... 10.4-5 10.4.5.1.2 Power Generation Design Bases ......................................................... 10.4-5 10.4.5.2 Description ............................................................................................. 10.4-5 10.4.5.3 Safety Evaluation ................................................................................... 10.4-6 10.4.6 Condensate Cleanup System ..................................................................... 10.4-7 10.4.6.1 Design Bases ........................................................................................ 10.4-7 10.4.6.1.1 Power Generation Objective ............................................................... 10.4-7 10.4.6.1.2 Power Generation Design Bases ........................................................ .10.4-7 10.4.6.2 Description ..............................................................................................10.4.7 10.4.7 Condensate and Reactor Feedwater Systems .......................................... 10.4-10 10.4.7.1 Design Bases ...................................................................................... 10.4-10 10.4.7.1.1 Power Generation Objective ............................................................. 10.4-10 10.4.7.1.2 Power Generation Design Bases ....................................................... 10.4-10 10.4.7.1.3 Safety Design Basis .......................................................................... 10.4-10 10.4.7.2 Description ........................................................................................... 10.4-10 10.4.7.2.1 Condensate Pumps ............................................................................ 10.4-11 10.4.7.2.2 Feedwater Heaters ............................................................................. 10.4-11 10.4.7.2.3 Reactor Feedwater Pumps................................................................. 10.4-11 10.4.7.2.4 Feedwater Piping .............................................................................. 10.4-11 10.4.7.2.5 Hotwell Transfer System .................................................................. 10.4-12 10.4.7.3 Piping Inspections ................................................................................ 10.4-12
REFERENCES FOR SECTION 10.4 ................................................................. 10.4-13 UFSAR/DAEC-1 Chapter 10: STEAM AND POWER CONVERSION LIST OF TABLES 10-iii Revision 17 - 10/03
Tables Title Page 10.2-1 TURBINE - GENERATOR OPERATING CONDITIONS . . T10.2-1 UFSAR/DAEC-1 Chapter 10: STEAM AND POWER CONVERSION LIST OF FIGURES 10-iv Revision 16 - 11/01
Figures Title 10.2-1 Turbine - Generator Heat Balance Rated Power
10.2-2 Turbine Shielding Modificaitons
10.2-3 Site Plan Showing Site Boundary Doses
10.3-1 Sheet 1 Main Steam System P&ID
10.3-1 Sheet 2 Main Steam System P&ID
10.3-1 Sheet 3 Main Steam System P&ID
10.4-1 Sheet 1 Turbine Extraction Steam and Drains P&ID
10.4-1 Sheet 2 Turbine Extraction Steam and Drains P&ID
10.4-1 Sheet 3 Turbine Extraction Steam and Drains P&ID
10.4-1 Sheet 4 Turbine Extraction Steam and Drains P&ID
10.4-1 Sheet 5 Turbine Extraction Steam and Drains P&ID
10.4-1 Sheet 6 Turbine Extraction Steam and Drains P&ID
10.4-2 Circulating Water System P&ID
10.4-3 Condensate Demineralizer System P&ID
10.4-4 Sheet 1 Condensate and feedwater P&ID
10.4-4 Sheet 2 Condensate and feedwater P&ID
UFSAR/DAEC - 1 10.1-1 Revision 17 - 10/03 Chapter 10 STEAM AND POWER CONVERSION 10.1
SUMMARY
DESCRIPTION
The power conversion systems are designed to produce electrical energy through the conversion of a portion of the thermal energy contained in the steam supplied from the reactor, to condense the turbine exhaust steam into water and to return the water to
the reactor as heated feedwater with essentially all of its gaseous, dissolved, and particulate impurities removed. The power conversion systems include the turbine-generator, main condenser, main condenser gas removal and turbine sealing equipment, turbine bypass system, circulating water system, condensate demineralizer, condensate and reactor feedwater systems, and the condensate storage and transfer system. These subsystems are required for the energy conversion of high-pressure steam to electric
power.
The heat rejected to the main condenser is removed by the circulating water system. The saturated steam produced by the boiling water reactor (BWR) is passed through the high-pressure turbine where the steam is expanded and then exhausted through the moisture separator/reheaters. Moisture is removed in the moisture separators, and the steam is superheated in the reheaters and then passed through the low-pressure turbines where the steam is again expanded. From the low-pressure turbines, the steam is exhausted into the condenser where the steam is condensed and deaerated. A small part of the main steam supply is continuously used by the steam jet air ejectors offgas jet compressor and the steam seal regulator (see Figure 10.2-1). The condensate pumps, taking suction from the condenser hotwell, deliver the condensate through the air ejector condensers, steam packing exhauster condenser, condensate demineralizer, and
five stages of low-pressure feedwater heaters to the reactor feed pumps. The reactor feed pumps supply feedwater through a high-pressure feedwater heater and the feedwater control valves to the reactor. Steam for heating the feedwater in the heating cycle is supplied from turbine extractions. The feedwater heaters also provide the means of handling the moisture separated from the steam in the turbine and in the moisture separators. Normally, the above requirements use all steam being generated by the reactor, but an automatic pressure-controlled steam bypass system is provided to discharge excess steam (up to 20.6% of the design flow) directly to the condenser.
UFSAR/DAEC - 1 10.2-1 Revision 17 - 10/03 10.2 TURBINE-GENERATOR
10.2.1 DESIGN BASIS
10.2.1.1 Power Generation Objective
The power generation objective of the turbine-generator is to receive steam from the BWR and to convert a portion of the thermal energy to electric power.
10.2.1.2 Power Generation Design Basis
The turbine-generator is designed for the conditions shown in Table 10.2-1. (See
also Figure 10.2-1.)
10.
2.2 DESCRIPTION
The turbine is a General Electric Company M6R 1800 rpm, tandem-compound, four-flow, three casing, condensing, two stage reheat unit with 38 in. last-stage buckets.
The turbine consists of one single-flow high-pressure shell plus two double-flow low-pressure shells. Steam from the high-pressure shell is reheated with extraction steam and main steam in two stages before entering the low-pressure sections. There are six
extraction stages used in reactor feedwater heating, as shown in detail in Figure 10.2-1.
Turbine controls include an electrohydraulic control system, control valves, main stop valves, combined stop-intercept valves, initial pressure regulator and backup controller, steam bypass system, and emergency mechanical overspeed trip.
There is a stop valve and a turbine control valve in each of the four main steam lines. With the stop valves open, steam flow to the high-pressure turbine shell is controlled by the turbine control valves. The DAEC utilizes partial-arc admission turbine control. The electrohydraulic control system operates these four valves sequentially.
Three of the four control valves open simultaneously. Once these three control valves are fully opened the fourth control valve opens to deliver 100% steam flow. All four control valves are equipped with mechanical stops to prevent over travel.
The generator is a direct-driven, three-phase, 60-Hz, 1800-rpm, 22,000-V, conductor-cooled generator rated at 715,225 kVa with a hydrogen pressure of 45 psig, and a 0.95 power factor, and a 0.58 short-circuit ratio. The exciter system is a mechanically connected alternator with solid-state rectifiers. The exciter is rated at 500-V, 1375-kW.
UFSAR/DAEC - 1 10.2-2 Revision 17 - 10/03 The reactor power level is varied to meet electrical system demand. It is regulated by control rod position and reactor r ecirculation flow. Control rod position is manually adjusted during normal operation; recirculation flow control is also adjusted to
raise or lower electrical output. The initial pressure regulator adjusts turbine control valve position to maintain constant steam pressure at the turbine stop valves.
The turbine is equipped with a steam bypass system that will bypass up to 20.6% of rated flow to the condenser to control steam pressure during load rejections, reactor heatup, turbine startup, and reactor cooldown. The turbine bypass system minimizes the
reactor vessel pressure rise, thus reducing reactor safety relief valve operation. The reactor will scram because of high pressure resulting from load rejections of magnitudes greater than the capacity of the turbine bypass system.
Hydrogen for the main generator cooling system is supplied from the Hydrogen Water Chemistry system, described in Section 9.3.5.
The turbine-generator is equipped with alarms and interlocks for lube-oil pressure, seal-oil pressure, exhaust vacuum, generator cooling, vibration, and field
excitation.
The turbine-generator is a base-load-type machine. Because of the cyclic nature of the system, and particularly in the early years of the plant operation, base-load power level will be changed as required by system demands. Other considerations that will impact on the amount and frequency of the cyclic loading are system reliability considerations and any operating limitations that my be imposed by the plant design.
The turbine-generator operation is limited by its design as follows:
Maximum gross generation 693,768 kW Maximum rotor speed 1980 rpm Maximum exhaust pressure (at rated power) 5.75 in. Hg absolute Maximum momentary throttle pressure 1255 psia Maximum continuous throttle pressure 994 psia Maximum momentary throttle temperature 573
°F Maximum continuous throttle temperature 544
°F Turbine-Generator Overspeed Control
The turbine control system provides two independent valves for defense against overspeed in each admission line to each turbine: a main stop valve and main control valve in series before the high-pressure turbine and a combined intermediate valve in series, one called an intercept valve and the other called an intermediate stop valve, at the inlet to each low-pressure turbine. On a moderate speed increase, the normal speed control system tends to close the control valve. During a higher overspeed, the UFSAR/DAEC - 1 10.2-3 Revision 13 - 5/97 intermediate stop, main stop, main control valve, and intercept valve are tripped closed rapidly on the removal of the fluid pressure in the emergency trip system. Valve opening actuation is provided by a 1600-psig hydraulic system that is totally independent of the bearing lubrication system. Valve-closing actuation is provided by springs and steam forces on the reduction or relief of fluid pressure. The system is designed so that a loss
of fluid pressure for any reason leads to valve closing and consequent shutdown. All valves, including their rapid-closing devices, can be tested during normal operation with minor load perturbation. The fast-closing feature of any valve is fully operative while the
valves are being tested.
The sensing of turbine-generator overspeed is accomplished by the elctrohydraulic control (EHC) system providing the following three independent means
of speed sensing:
- 1. The operating speed signal is obtained from two magnetic pickups on a toothed wheel at the high-pressure turbine shaft. An increase in either of the speed signals tends to close the control valves. The loss of both speed signals will trip the emergency trip system within the electrohydraulic control system. The operation of both speed signals is continuously monitored by the alarm circuit within the electrohydraulic system.
- 2. The mechanical overspeed trip uses an unbalanced rotating ring and a stationary trip finger to dump the emergency trip fluid system pressure
directly on reaching its set speed, typically 110% of rated speed. The main stop, intermediate stop, intercept, and control valves are tripped.
The operation of the overspeed trip mechanism and the mechanical trip valve can be tested during normal operation.
- 3. The electrical backup overspeed trip will trip the emergency trip fluid system that is within the electrohydraulic control system. The trip signals are generated on reaching the trip speed, typically 111.5% of rated speed. The operation of the backup overspeed trip and the electrically operated master trip solenoid valves can be tested during normal operation.
To prevent overspeed, the turbine generator is equipped with a sequential tripping circuit and a reverse power relay in series. It is designed to trip the generator line breaker only after all of the valves in the steam lines to the turbine have been closed and the generator begins to act like a motor and use electrical power instead of producing power.
Under these circumstances, steam flow is below a level that could produce an overspeed and the generator line breakers are opened. The reverse power relay has a 2-min time delay in parallel with it that will open the breakers after 2 min in case the reverse power
relay does not function.
UFSAR/DAEC - 1 10.2-4 Revision 13 - 5/97 The potential for overspeed of the turbine-gneator from energy stored in the
extraction lines and feedwater heaters has been reviewed by the turbine manufacturer during the design stages and it was determined that the entrained steam does not have potential to overspeed the unit beyond a safe limit. Free-swing check valves are used in
the turbine extraction lines in lieu of positive closing nonreturn valves because of the small overspeed potential of the feedwater heater system.
The conformance of the overspeed protection system to the applicable requirements of the IEEE 279 is a follows: A single failure of any component will not lead to destructive overspeed. A multiple failure, involving preexisting combinations of undetected electronic faults and/or mechanical stuck valves at the instant of load loss, is required. The probability of such joint occurrences is extremely low, resulting from both the inherently high reliability of the components and the frequent inservice testing of all
valves.
There had been 71 turbine trips from the time that the plant went into operation through June 1980. These included normal shutdowns. None of these trips were caused
by inadvertent turbine overspeeds. A turbine overspeed trip test is usually conducted in conjunction with turbine maintenance.
10.2.3 TURBINE DISK INTEGRITY
10.2.3.1 Design
The DAEC turbine is a GE M6R, tandem-compound, four-flow machine, with 38-
in. last-stage buckets and two-stage reheat.
The low-pressure rotors have been replaced with rotors of "monoblock" design, which have wheels that are integral to the shaft
10.2.3.2 Inservice Inspection
Although there are no code requirements for inservice inspection of the turbine-generator or the steam lines outside the isolation valves, inspections and monitoring of operation are conducted. During operation the turbine is monitored by a series of temperature, pressure, vibration, and differential expansion sensors which enable the operator to detect any malfunction. In addition, recorders are provided to give permanent records of vibration-eccentricity and temperature-expansion. The operator also has monitors on auxiliary systems of the turbine, such as valve and switch positions, thrust bearing wear, and pump operation. During operation on a routine basis, visual inspections are made. Photography and video recording are used on a routine basis to compare the condition of components with previous known conditions. Also, periodically the turbine will be completely dismantled during a planned outage and complete inspection made of its normally inaccessible parts. The inspection utilizes UFSAR/DAEC - 1 10.2-5 Revision 18 - 10/05 magnetic particle, magnoglo, dye penetrant, or ultrasonic methods as required, and will be conducted by DAEC personnel or consultants as deemed necessary. Any indications from these inspections which are determined to be flaws or cracks, will be analyzed for
their properties and effects, taking into account their location and the stresses at those
locations.
10.2.4 EVALUATION
A turbine missile analysis was performed for the original rotors, which is assumed to be bounding for the monoblock design. The results are presented in Section 3.5.1.3.
A comprehensive study was undertaken to determine, by calculational methods, what the site boundary dose was expected to be from direct and sky-shine radiation. This included a Monte Carlo-type calculation for determining the appropriate source terms.
As the results of this study became available, a decision had to be made as to
whether additional shielding was necessary to reduce the calculated dose. However, because of the inaccuracies inherent even in sophisticated shielding calculations, a comprehensive program to measure the site boundary dose was initiated after the plant began commercial operation. The results of this program form the basis for the final turbine shielding configuration. The comprehensive Monte Carlo-type study was conducted to determine, by calculational method, the site boundary dose from expected
direct and sky-shine radiation.
As a result, additional shielding was installed These changes are shown in Figure 10.2-2. Turbine-generator shielding is shown in Figure 1.2-5.
In order to reduce outage duration and dose, the 3" thick upper sections of the south and north turbine steel shield wall were removed in 2001. The effect of the removal on the site boundary dose was confirmed to be negligible by the DAEC Annual Report to USNRC, Radiation Environmental Monitoring Program, January 1 to December 31, 2002. The report concluded that no plant effect was indicated by the TLDs when dose results were compared to the estimated average natural background for Middle America.
Dose point locations are shown in Figure 10.2-3. The conservatism in the calculations have been confirmed by the actual dose measurement program offsite dose measurements continue to demonstrate that even with the advent of the use of Hydrogen Water Chemistry, as well as the Extended Power Uprate program, offsite radiation levels due to sky-shine undetectable compared to background radiation.
UFSAR/DAEC - 1 T10.2-1 Revision 17 - 10/03 Table 10.2-1 TURBINE-GENERATOR OPERATING CONDITIONS
Parameter Rated Power
Steam flow to HP Turbine (983 psia and 0.41% moisture at the TSV) 7,983,655 lb/hr
Back pressure 2.0/2.75 in. Hg abs
System makeup 0%
Feedwater temperature to reactor 431.4°F
Generator output 676,425 kW
Stages of feedwater heating 6
TURBINEANDEXTRACTIONARRANGEMENTISSCHEMATICONLYTurbineAssumedtobeinNewandCleanConditionTHEVALUEOfGENERATOROUTPUTSHOWNONTHISHEATBALANCEISAfTERALLPOWERfOR353343M9683PEXCITATIONANDOTHERTUR8INE-GENERATORAUXILIARIESHASBEENDEDUCTEDriil1ii90f'.;i-B552.0P967.0HAT1.5INHeHOODAHOODB2257101.M2257101.MELEP=979.3H993.3HUEEP=994.1H1000.0H2.00INHG2.75INHGBASEELEP=940.6HGenerator-715225.*KVAGENERATOROUTPUT676425.KWAT.9SPOWERfACTORANO45.0PSIGH2PRES2525.KWfIXEDLOSSES7948.KWGENLOSSES1800.RPM205.2PB5907745.M212.31283.1HPIVSTEAMREHEATER12.4TID353343.M967.1P537.4H'"P=52;:qDqv,....,,...,....,-17.3P-8.02P---"'=fP"'220.5TlB3.0TSJAENSP£N300.0PNI'---.r-'"'"5.0TO'"="'6H=1.12"5.0TO-¢10.0DC'""'-10.0DCn--;;:0='"=a=J-"'",'"P=N=.=.97="'.="'0ToCondensoteStorogetonk1157.9Ht.STEAM10-REHEATERt::i17.2TTD*r;407006.M549.0P46D.7H"'F-,:CF-63.1P296.0TN787364.M363.1H(5l001STURESEPARATOR977.Effective220.2P1098.0H6695109.M6341.M1190.8Hi:a:::fL_-,:::;;;310540.M1171.2HfP.::213.0P121O.DP387.IT'"'"5.0TO'"'"6H=3.67=5.0TO*c:5.0TO".:-¢10.0DC-10.0DC-10.0OC"'"'=N'"'"",,,,J-",,,,f-.Icc..",=lSiN-'""'=NNAssumedFPDriveEfficiencies:95%Molor98%Tronstormer-0-5TOM.SEPARATOR(77'r>-'"'"i"'"t'0-367.3P="=436.3T-'"5.0TO-=10.0DC'"'"f-=.-7983655.M542.5T983.0PSIA1190.BH'"='"={g=0F5156l"!"!rVALVEBESTPOINTNETHEATRATE7962655.{1190.8-410.1I+353343.{1190.8-410.1I:.-+-=2.,.,1O"f00ii*"lrll",90",.8'o*,,-",48"";:.09772I676425.-9624.IBTUKW-HRLEGENO-CALCULATIONSBASEDON1967ASMESTEAMTABLESM-fLiJll-LBIHRP-PRESSURE-PSIAH-ENTHALPY-8TUIl8T-TEMPERATURE-fOEGREESDUANEARNOLDENERGYCENTERIESUTILITIES.INC.UPDATEDFiNALSAFETYANALYSISREPORTTurbine-GeneratorHeatBalanceRatedPowerFigure10.2-1Revision17-10/03
UFSAR/DAEC - 1 10.3-1 Revision 13 - 5/97 10.3 MAIN STEAM SUPPLY SYSTEM
10.3.1 DESIGN BASES
10.3.1.1 Power Generation Objective
The power generation objective of the main steam lines is to conduct steam from the reactor vessel through the primary containment to the steam turbine.
10.3.1.2 Power Generation Design Bases
- 1. The main steam lines are designed with suitable accesses to allow inservice testing and inspections.
- 2. The main steam lines are designed to conduct steam from the reactor vessel over the full range of reactor power operation.
10.3.1.3 Safety Design Basis
The main steam lines are designed to accommodate operational stresses, such as
internal pressures, without a failure that could lead to a release of radioactivity in excess
of the guideline values in published regulations.
10.
3.2 DESCRIPTION
All main steam piping is classified according to service and location. The materials used in piping are in accordance with the applicable design code and supplementary requirements. The main steam system piping and instrumentation diagram (P&ID) is shown in Figure 10.3-1.
The main steam lines meet Seismic Category I requirements up to, but not
including, the turbine stop and control valves.
The reheater steam lines and turbine bypass lines also meet Seismic Category I requirements.
UFSAR/DAEC - 1 10.3-2 Revision 13 - 5/97 The nuclear piping for the DAEC main steam line, reheater steam line, turbine bypass lines, and all branch lines 2.5 in. or larger in diameter is designed in accordance
with ANSI B31.1.0 and the applicable Code Cases N-2, 7, 9, and 10 with the following
exceptions to the nuclear code cases applied to branch line vales larger than 2.5 in. in diameter:
- 1. Comply with the positive sealing requirements for bonnet and stem leaks as specified in Code Case N-2. Conventional valve design in accordance
with ANSI valve standards is provided.
- 2. Provide full radiography of valve pressure boundary castings because Code Case N-2 makes this a requirement only for cast austenitic materials.
The imposition of this requirement on the standard carbon steel valves used in most of the systems, other than Class 1, creates a question of doubt as to acceptability because of standard manufacturing practices for this
valving application. This is because these valves for such low-pressure/low-temperature systems in a BWR are standard shelf-type valves that have conformed with ANSI (formerly ASA) standards for many years, and as such, the body castings are not amenable to passing a Class 1 radiography inspection. Dye penetrant or magnetic particle inspection of the body castings is employed inside and out to achieve a full surface inspection. The carbon steel valves used in Class 2 systems
receive a shop hydrostatic test in accordance with the applicable standards
and codes.
For operational and functional reasons, the turbine stop valves are 100%
volumetrically examined by GE.
Nondestructive examinations before initial plant startup of pressure boundary weldments were performed in the main steam line and on branch lines larger than 2.5 in.
in nominal diameter up to the first branch valve.
The main steam lines down through the turbine stop and control valves and including the turbine steam leads up to the turbine inlet have been subjected to a seismic analysis. Branches connecting to the main steam line of a size, configuration, and/or mass that may have a significant contribution have also been included, such as piping to the steam bypass valve chest. The analysis of these lines encompasses the piping and inline components (principally valves) between anchor points. The downstream anchor point has been chosen to include the first valve downstream of the second main steam
line isolation valve. This includes the consideration of all branch lines 2.5 in. or larger in diameter.
- 1. The analysis uses a multi-degree-of-freedom dynamic model in accordance with the requirements of Section 3.7.1.
UFSAR/DAEC - 1 10.3-3 Revision 17 - 10/03
- 2. The turbine building is designed to Uniform Building Code (UBC) Zone 1 as a minimum. However, in order to determine the end displacements and seismic forces on the main steam piping, analyses were performed to determine needed response spectra at the pipe anchor points.
A simplified lumped-mass mathematical model employing response spectra inputs to simulate earthquake response of the turbine building was used to determine the response of the main steam line support system for an OBE. After determining the response of the support system, a response spectra diagram was prepared to show relative response motion acceleration and velocity as a function of the main steam piping system
frequencies.
The forces induced by the earthquake loading in the main steam piping were
included with other operating loads to properly design the pipe supports and anchors.
10.3.3 SAFETY EVALUATION
Differential pressures on reactor internals under the assumed accident conditions of ruptured steam line are limited by the utilization of flow restrictors and the utilization of four main steam lines.
All main steam and feedwater piping is designed as described in Sections 3.2.1, 3.2.2 , and 5.2.1.
10.3.4 INSPECTION AND TESTING
For that portion of the main steam line downstream of the second isolation valve, inspections have been performed visually and with appropriate testing when a steam line
has been operated beyond its design (although it was not Iowa Electric practice to perform scheduled inspections of steam lines in power-producing facilities). The same practice has been continued for the DAEC steam lines. In order to allow inspection when necessary, essentially 100% access has been provided for the main steam lines and branch connections 2.5. in. in diameter or larger.
Further details on preoperational and inservice inspection are described in
Sections 6.6, 5.2.4, and 3.9.6.
In addition, due to the increase in steam flowrate due to Extended Power Uprate, vibration monitoring was performed to assure that unacceptable flow-induced vibrations were not present (Reference Section 14.2).
UFSAR/DAEC - 1 10.3-4 Revision 18 - 10/05 The type and extent of nondestructive examination applied to the pipe, valves, and fittings in the main steam lines up to and including the turbine stop valves were as follows:
- 1. All circumferential and longitudinal full penetration welds on pressure-retaining components were fully examined by radiography. Accessible surfaces of each weld were examined by either liquid penetrant or magnetic particle methods.
- 2. All branch connection welds larger than 4 in. were fully examined by radiography. Accessible surfaces of all branch connection welds were examined by either liquid penetrant or magnetic particle methods.
- 3. Fillet welds, socket welds, and attachment welds such as supports, lugs, anchors, and guides were examined on all accessible surfaces by either liquid penetrant or magnetic particle methods.
- 4. Seamless pipe was ultrasonically examined by the angle beam method. Plate for welded pipe, including fittings, was ultrasonically examined by the straight beam method.
- 5. Castings for pressure-retaining components were fully examined by radiography. All castings for pressure-retaining components were examined on all accessible surfaces by either liquid penetrant or magnetic particle methods.
- 6. Forgings for pressure-retaining components were ultrasonically examined by angle beam and/or straight beam methods and by the liquid penetrant or magnetic particle methods. Forged fittings were examined by the liquid penetrant or magnetic particle methods.
Visual inspections of the steam lines and turbine stop valves are conducted during
outages. Special attention is given to detecting indications of leakage and changes in position of pipe hangers. Photography is used to compare existing conditions with
previous ones. Also, periodically (in accordance with the Nuclear Insurers Machinery Loss Control Program) the turbine stop valves will be completely dismantled during a planned outage for a complete inspection of their normally inaccessible parts.
10.3.5 STEAM AND FEEDWATER MATERIALS
10.3.5.1 Fracture Toughness
See Section 5.2.
UFSAR/DAEC - 1 10.3-5 Revision 13 - 5/97 10.3.5.2 Material Selection and Fabrication
Seamless pipe is ASTM A-106, Grade B. Rolled and welded pipe is ASTM A-
155, Class 1, Grade KC 70.
Certification in writing is required form the manufacturer that all pipe, fittings, flanges, bolting materials, valves, and welding wire meet applicable material specifications along with mill test reports.
One hundred percent radiography was required on all butt welds during
fabrication and erection. See Section 17.1.9 for further details on fabrication assembly and erection.