ML20202B623
| ML20202B623 | |
| Person / Time | |
|---|---|
| Site: | Limerick  |
| Issue date: | 01/23/1998 |
| From: | SIEMENS POWER CORP. (FORMERLY SIEMENS NUCLEAR POWER |
| To: | |
| Shared Package | |
| ML20070L459 | List: |
| References | |
| ER-9605NP, ER-9605NP-R01, ER-9605NP-R1, NUDOCS 9802120061 | |
| Download: ML20202B623 (57) | |
Text
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SIEMENS .
ER 9605NP -
ENGINEERING REPORT ER-9605NP (Non Proprietary Version)
MISSILE PROBABILITY ANALYSIS METHODOLOGY FOR LIMERICK GENERATING STATION, UNITS 1 & 2 WITH SIEMENS RETROFIT TURBINES REVISION NO.1 ,
January 23,1998 l
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9802120061 980204 DR ADOCK 050003 2 D \ SIEMENS POWER CORPORATION FOSSIL DMSION ENGINEERING DEPARTMENT
, . January 9,1998 Rev.1 PAGE 1OF45 ER 9605NP l}qD3')cO ,;gy {
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SIEMENS ER 9605NP I TABLE OF CONTENTS PAGE 1.0
SUMMARY
AND RESULTS BASED ON DESIGN SPECIFICATIONS 5
2.0 INTRODUCTION
5 3.0 MISSILE PROBABILITY ANALYSIS 7 4.0 PROBABILITY OF DISK BURST UP TO 120% OF RATED SPEED 8 4.1 CRITERION FOR BURST 8 4.2 STRESS CORROSION CRACKING BEHAVIOR OF ROTOR 10 DISK MATERIALS 4.3 SIEMENS/KWU DESIGN FEATURES 11 4.4 SCC INITIATION MODEL 13 4.5 SCC GROWTH RATE MODEL 14 4.6 EVALUATION PROCEDURE FOR DISK BURST 15 4.7 MONTE-CARLO METHOD FOR PROBABILISTIC 15 ANALYSIS 5.0 PROBABILITY OF CASING PENETRATION FOR SPEEDS UP TO 16 120% OF RATED SPEED.
6.0 PROBABILITY OF A RUN-AWAY OVERSPEED >120% 17 7.0 DISCUSSION OF RESULTS 18 C.0 CONSERVATISM IN METHODOLOGY 19
9.0 REFERENCES
21 SIEMENS POWER CORPORATION FOSSIL DMSION ENGINEERING DEPARTMENT January 9.1998 Rev.1 PAGE 2 OF 45 ER 9605NP
SIEMENS ER 9605NP APPENDIX OF TABLES AND FIGURES List of Tables:
Table 1. Tangential Surface Stress Levels of Disk #1 With & Without Additional Measures (Also see Figure 9).
Table 2.
Table 3.
Table 4.
List of Figures:
- Figure 1 Figure 2 Figure 3.
t Figure 4. Siemens Design Evolution from Ten Disks to Six Disks Configuration.
Figure 5. Schematic Showing Favorable and Unfavorable Nuclear Tur-bine Unit Orientation.
F;gure 6. Typical Stress Corrosion Crack Growth Rate vs. Stress Inten-sity Factor.
Figure 7. Influence of 0.2% Offset Yield Strength on Crack initiation Time in Pure Water for LP Disk Materials.
Figure 8. Stress Corrosion Crack initiation of LP Turbine Rotor Steels, 0.2% Yield Strength Less than 1000 Mpa.
SIEMENS POWER CORPORATION FosslL DMSION ENGINEERING DEPARTMENT January 9,1998 Rev.1 PAGE 3oF 45 ER 9605NP
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Figure 9.-
Figure 10.
Figure 11.
Figure 12.
Figure 13.
l Attachment A:
SIEMENS POWER CORPORATION FOSSIL DMSION ENGINEERING DEPARTMENT January 9,1998 Rev.1 - PAGE 4 OF 45 ER 9605NP
SIEMENS
___ ER 9605NP 1.0
SUMMARY
AND RESULTS BASED ON DESIGN SPECIFICATIONS: l Siemens methodology for the missile probability evaluation of the Limerick generat-ing station, turbine-generator units No.1 & 2 to be retrofitted with the advanced design Siemens turbines is described. Results based on design specifications for material properties and operating conditions are included. These results will be updated as needed, after the manufacture of the turbine, using actual measured properties and data.
The basic principles of the methodology are the same as those used by Siemens in previous studies which included Grand Gulf, Comanche Peak, and Connecticut Yankee ( 1-3 ), and which have been reviewed and accepted by the NRC. How-ever, in this report, a Monte-Carlo simulation technique has been developed and utilized for probabilistic computations. With the utilization of this technique, it is now possible to easily incorporate the statistical variability of each of the variables l involved and to improve the accuracy of analysis.
1 As detailed in the proprietary version of this report, the external missile probability of the unit at O/QlO valve test interval is well below the NRC criterion for startup and continued operation up to 100,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> interval between disk inspections, provided no cracking is detected. The internal disk burst probability is also below the NRC allowable limit.
2.0 INTRODUCTION
Siemens Power Corporation (SPC) and Siemens/KWU will manufacture and install the newly designed advanced Siemens LP turbine rotors in the Limerick Generating Station, Units Nos.1 & 2, which are presently General Electric units. The units are identical in design with each unit consisting of an HP and three double flow LP turbines tehich are tandem compounded with a rated speed of 1800 RPM. Each LP turbine consists of a total of six shrunk-on disks (three per flow).
slEMENs POWER CORPORATION FOSStL DMSION ENGINEERING DEPARTMENT January 9,19% Rev.1 PAGE 5 OF45 ER 960SNP
SIEMENS ER 9605NP The most significant source of turbine missile is a burst type failure of one or more of the bladed disks of an LP rotor due to stress corrosion cracking (SCC). Over the last 30 years, Siemenn has continua!!y advanced its LP turbine design from a ten disk, to en eight disk, to the present six disk configumtion (see Figure 4). For LP disk type rotors, Slemens introduced in the late 1960's, a ten disk design (five per flow) with the first two disks carrying the Integral shroud or " drum" type blading and i the last three disks carrying one free standing blade row each. In 1986, with the advent of improved forging proces*as, Siemens introduced the eight disk design l (four per flow). The first two diskt, of the ten disk design were combined into one disk to carry all rows of drum type blading. This design was improved by additlanal measures against stress corrosion cracking by inducing compressive residual stresses on the surface of disks, keyways and the blade attachment caulking area.
Twenty nine rotors of this design have been manufactured and installed. In 1995 the present six disk design (three per flow) was introducod, which combines the number two and three disks of the eight disk design into one (new No. 2) to carry two rows of free standing blatag. This newly developed design provides improved thermal performance, while maintaining and onhancing the already high degree of reliability and availability of previous designs. Additionally, residual compressive stresses are induced in the radil of the blade attachment area of those disks that are susceptible to SCC. Replacement of existing turbines (Glemens or other OEM's) with improved six disk LP turbines results in a gain of power plant output.
SPC and Siemens/KWU are offering tc. apgrade existing units with these new LP turb!nes. Current upgrade projects include Almaraz Units Nos.1 & 2 and Limerick Units Nos.1 & 2.
At described later, the newly c'eveloped clx disk LP turbine, significantly reduces the missile probability in the following ways:
- 1. Fewer disks, six instead of the previous eight, reduces the missile probability.
- 2. Disks Nos. 2 and 3 are not keyed, which reduces the stress concentration factor which in turn reduces th. probability of disk burst due to stress cor-rosion cracking.
- 3. No.1 disks are keyed on the down stream side of steam flow, which reduces the probability of burst due to reduced stress corrosion crack growth rates at reduced temperature.
- 4. Incroased residual compressive stresses made possible due to larger disk s sizes reduces the probability of disk burst due to stress corrosion cracking.
1 stCMENS POWER CORPORATION FOSSIL DMSION ENGINEErJNG DEPARTMENT January 9.1998 Rev.1 PAGE 6 OF 45 ER 9605NP
SIEMENS i
ER 9605NP For stearn turbines at nuclear power plants, the Nuclear Regulatory Commission (NRC) requires the equipment manufacturer to perform a probability study to con-firm that the likelihood of producing an external missile remains below the value of 1E 5 per year for a turbine with an unfavorable orientation (such as Limerick #1 and
- 2 ) and 1E-4 per year for a turbine with a favorable orientation with respect to the reactor containment (Figure 5). Turbine inspection intervals and overspeed protection system test intervals are set to insure that the external missile probabili-i ties remain below the NRC's required limits.
3.0 MISSILE Pi!9BABILITY ANALYSIS:
The most significant source of a turbine missile is a bu'st type failure of one or more bladed disks of an LP rotor. Failures of other ro' ors including the HP and generator rotor would be contained by relatively ma641ve and strong turbine cas-ings, sven if failure occurred at maximum conceivahe overspeed of the unit. There is a remote possibility that some minor missiles cotid result from the failuro of cou-plings or portions of rotors which extend outside th a casings. Also, failure of exciter rotating elements could produce missiles because the exciter housing is relatively I
light. However, both exciter and coupling missiles wobid be much less hazardous l than the LP disk missiles, due to low mass and e.1ergy and therefore, will not be considered. Compressive stresses are Induced in the blade attachment area and blade loading is limited by design to minimize the possibility of blade attachment crack initiation and blade detachment as described later.
The probability of an external missile (P,)is evaluated by considering two distinct types of LP rotor disk failures, namely; 1) failure at normal operating speed up to 120% of the rated speed, and c) failure due to run away overspeed greater than 120% of rated speed as follows.
P, = P,+ Po = E(P,,
- P 2,
- P 3,) + E(P o
- P,o
- P30) for all LP d,sks i (1)
Where:
P = Probability of an external misslie.
3 P, = Probability of an external missile fur speeds up to 120% rated speed. ,
P, = Probability of an external missile for speeds greater than 120% rated speed. '
E = Sum of probabilities for all disks (6 disks per rotor x 3 rotors = 18 disks).
P,, = Probability of turbine running up to 120% rated speed = 1.0 (conservatively assumed). ,
P,, = Probability of disk burst up to 120% of rated speed due to stress corrosion '
crack growth to critical size.
SIEMENS POWER CORPORATION FOSSIL DMstoN ENGINEERING DEPARTMENT January 9.1998 Rev.1 PAGE 7 oF 45 ER 900$NP
SIEMENS ER 9605NP D.,, = Probability of casing penetration given a burst up to 120% of rated speed.
P,o = Probability of a run away overspe6J incident (>120% of rated speed),
due to failure of overspeed protection system.
P,3 = Probability of disk burst given run away overspeed >120% = 1.0 (conservatively assumed).
Po= 3 Probability of casing penetration given a burst at run away overspeed
>120% = 1.0 (conservatively assumed).
The probability of normal operating speeds u, 420% of the rated speed is con-servatively assumed to be 1.0. Similarly it is awu conservatively assumed that, given that the overspeed protection system falls, the probability of a disk burst and that of casing penetration of the burst fragments are also 1.0 each for all disks.
Therefore, the only remaining values that need to be quantified to solve equation (1) are, P,,, P3, , and P, . The methodology for evaluating these probabilities are discussed in the following sections.
4.0 PROBABILITY OF DISK BURST UP TO 120% OF RATED SPEED (P,,):
The probability of a disk burst increases with operating hours due to the potential for stress corrosion crack growth radially extendin from the boro. Such cracking has been experienced in the bore and keyway regions of LP shrunk-on disks in service, both in nuclear and fossil steam turbine unito. The contribution of fatigue to crack growth due to start-stop cyclic operations is considered minimal because of low fatigue crack growth rates and the relatively few start-stop cycles expected between inspections.
In this section, the basic equations governing stress corrosion crack growth and disk burst are first reviewed. The dcaign features of the newly developed six disk (three per flow) configuration such as the ones to be installed in Limerick #1 and #2 to eliminate stress corrosion cracking are described. Then, assumptions and pro-cedure for conservatively estimating the probability of disk burst up to 120% of the rated speed are outlined.
4.1 CRITERlON FOR BURST:
When materials such as used in turbine disks are exposed to sustained high tensile stress and an aggressive moist environment, cracks initiate and grow with time.
This phenomenon is known as S'ress Corrosion Cracking (SCC). Low pressure steam turbine shrunk-on disks with high stresses at the bore are susceptible to stress corrosion cracking. As a crack initiates and then grows with operating time, the stress interisity factor associated with the crack also increases. Finally, when the stress intensity factor approaches and equals the critical stress intensity factor SIEMENS POWER CORPORATION FosslL DIVISloN ENGINEERING DEPARTMENT January 9,1998 Rev.1 PAGc 8 oF 45 ER 9605NP
SIEMENS ER 9605NP for the material which is the fracture toughness property, a disk buret condition occurs. Alternatively, a critical crack corresponding to the material fracture tough-ness is calculated, and a burst condition considered to occur when the crack size approaches and equals the crlilcal crack size. This is illustrated by the following equations.
a, s a ... . ............ ........ ........... .. . . .. ... .. .re p re se n ts bu rst (2) a = a, + f (daldt)* dt (3) a, = f (K ,ic o, Q, k/K, d/2) (4) l K(a) = 9 (o, a, Q, k/K) (S)
Where:
l a, = Critical crack Size, a = Current crack Size, a, = lnitial crack Size, K(a) = Stress intensity factor for the current crack, a, da/dt = Stress corrosion crack growth rate, t = Operating time d'et;on, O = Aspect ratio factor of crack, K ic = Fracture toughness, k/K = Crack branching factor, o = Tangential stress at bore, and d/2 r- Keyway radius only where applicable.
The tangential stress due to rotation is maximum at the bore and reduces with radial distance from the bore (see Figure 9). However, when superimposed with the compressive residual stress induced during manufacture, the combined stress is more or less constant with depth. Based on this, the following equation for the critical crack size is obtained from the published stress intensity factor solution, a, = (Q/(1.21*n))*(Kic/((k/K)*o))^2 - d/2 (6)
A crack branching factor (k/K)is used to account for the effect of crack branching that is invariably associated with stress corrosion cracking.
SIEWlENs POWER CORPORATION FOSSIL DMSloN ENGINEERING DEPARTMENT January 9,1908 Rev.1 PAGE 9 OF 45 ER 960$NP
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For probabilistic analysis appropriate statistical distributions are assumed for the crack shape and crack branching factors.
For probabilistic analysis, the critical crack size is defined as that given by equation (6) or 100 mm, whichever is smaller. The 100 mm limit is purely based ori the applicability limitation of equation (6) for the six disk design and does not neces-sarily represent an imminent burst condition.
K,i values are individually calculated for each disk from the actually measured yield strength and the room temperature Charpy V notch impact energy using Rolfe-Novak( 5 ) equation for upper shelf behavior. The maximum specified FATT for the Siemona disks is low enough to ensure that the ambient tempera-l ture Cht .py impact energies and K,, are in the upper shelf range. The material l used is a NICrMoV steel forging which has excel-lent hardenability. However, even if an increase in FATT is conservatively assumed for the disk interior, the material toughness will still be in the upper shelf region at ambient temperature.
4.2 STRESS CORROSION CRACKING BEHAVIOR OF ROTOR DISK MATERIALS:
Slemens has conducted extensive studies into the SCC behavior n'.oaterials used for rotor disks (6-g ). Based on these studies and available data ftom technical lit-erature (10-12 ) in general, it is of Interest to note the following information about the SCC behavior .
SCC consists of an initial crack initiation period in which pitting or cracks are formed which is followed by a crack growth period. SCO initiation is not understood well enough to quantify its timo dependent behavior. However, SCC crack growth behavior can be modeled using linear elastic fracture mechanics. Figure 6 shows a schematic showing the SCC growth rate (da/dt) as a function of the applied stress intensity factor (K), which exhibits three distinct regions. Region I shows that daldt rapidly decreases with decreasing K, approaching no crack growth below a threshold value of K, defined as K isce. During Region 11, daldt is viitually independ-ent of the K level, until K approaches the material fracture toughness level. Then in Region Ill, the daldt approaches unstable high values leading to fracture. K sce i is typically of the order of about 20 30 MPaVm. This mear.s that a finite threshold i
crack size has to be either initiate or be present in order for crack growth to con-
- tinue. The lower the stress, the targer is this threshold crack size.
SIEMENS POWER CORPORATION FOSSIL DivlSION ENGINEERING DEPARTMENT Jantary ').1998 Rev.1 PAGE 10 oF 45 ER 960$NP
SIEMENS ER 9605NP Impurities in steam, conditions promoting flow stagnation such as crevices, steam condensation, ratio of stress to yleid strength and level of yloid strength cignificantly influence the potent'al for SCC.
In high purity water with a conductivity of < 0.2pS/cm, stress corrosion crack initla-tion is influenced only by the quenching and tempering process which establishes the material's yleid strength value. If the yleid strength exceeds approximately 1085 MPa (157 ksi), the material becomas susceptible to SCC due to hydrogen embrittlement (Figuro 7) Up to this threshold, no stress corrosion crack initiation occurred even when operating stresses exceeded the yloid strength In notched specimens. This result is also not affected by the purity of stcel. Materials con-ventionally smelted 25 years ago behaved in high purity water as well as today's steels which are smelted in accordance with the electrostag remelting process.
Under high purity water conditions, even nonmetallic inclusions (e.g. Al,0 3, MnS, etc.) do not act as crack starters at the material surface. Such inclusions do not influence the resistance to stress corrosion cracking. This even applies to water with low oxygen content as well as to oxygen saturated water. Pit formation was also not found under these corrosive conditions.
Findings from extensive testing, power plant experience and review of literature leads to Figure 8. For yield strengths less than 1000 Mpa , this figure shows at what operating stress to yield strength rat!os, stress corrosion crack initiation can be expected for specific environment conaitions. As shown in the figure, an improvement of the operating environment permits high stress levels up to and above the yleid strength level of the material. The diagram also reveals that with stresi levels below 50% of the yield strength, stress corrosion cracking has not occurred even under severe corrosion conditions.
4.3 SIEMENS/KWU DESIGN FEATURES:
Specified yield strengths are below 1000 MPa, which minimizes he material's stress corrosion crack initiation potential.
The six disk design feature has eliminated the need for keys in disks #2 and #3.
The locatior and design feature of the keyways in Disk #1 minimizes steam condensation and stagnant conditions and thus reducing SCC potentialin service.
Operating stress levels are reduced by eliminating keyways in Disks Nos. 2 and 3 and by introducing significant compressive stresses through heat treatment of all the disks, shot peening of surfaces including the blade attachment area, and rolling to induce compressive residual stresses following by honing of keyways (cee Table 1). Tho operating stress levels at or near the surface are well below 50% of the yield strength thus virtually eliminating stress corrosion crack ini.
tlation (see Figure 9).
- SIEMENs POWER CORPORATION FOSSIL D!vlSION ENGINEERING DEPARTMENT January 9.1998 Rev.1 PAGE 11 OF 45 ER 900$NP
. - . . . ~ - - . .. _ - - _ . _ _ _ _ _ _ _ _ _ . . - . -
SIEMENS ER 9605NP Siemena has used the same general blade attachment arrangement for both inte-gral shroud or " drum" stage and free standing blading for more than thirty years for both nuclear and fossil units. Some nuclear units are approaching 200,000 operat-Ing hours without blade attochment failure, Inspections to date have not found crack initiation in the blade attachment area of disks or rotor forgings of either nuclear or fossil units. Because nuclear unP. LP disks are operating in conditions where stress corrosion cracking is possible, blade loading on disk surfaces in the present design is maintained such that the stresses are less than 50% of material yleid strength.
SIEMENS POWER CORPORATION FOSSIL DMSION ENGINEERING DEPARTMENT January 9,1996 Rev 1. PAGE 12 OF 45 ER 960$NP
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4.4 SCC INITIATION MODEL:
Since SCC initiation is not understood well enough to be quantifiable as a function of time, h is modeled based on the observed cracking experience of the turbine disks in the field.
Based on conservative statistical analysis of the service experience with Slemens Units and corresponding reported GE and Westinghouse data, the probability of crack initiation for Siemens design is estimated to be about 3 7 times lower than those for GE and Westinghouse units. The actual details are included in the proprietary version of this report.
l l
l stEMENs POWER CORPORATION FOSSIL DIVISION ENGINEERING DEPARTMENT January 9,1998 Rev.1 PAGE 13 oF 45 ER 9005NP
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SIEMENS ER 9605NP 4.5 SCC GROWTH RATE MODEL:
As illustrated in Figure 6, da/dt is assumed to be Independent of the K level. How-ever, it is found to be a function of temperature, material yield strength and water chemistry.
Based in Slemens field experience and the available SCC growth data from literature, SPC has developed a SCC growth rate model which is appropriate for original GE unit steam conditions. This model is used for the SCC growth analysis.
Further details are discussed in the proprietary version of this report.
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. . ~ . _ _ _ _ .
SIEMENS ER 9605NP F j 4.6 EVALUATION PROCEDURE FOR P,,,
Based on the above discussion, the probability of a disk burst at speeds up to 120% of the rated speed is expressed as P2, = Pu ' P g (8)
Where:
Pu = Probability of initiation Pg = Probability of Crack growth to Critical size = Probability of (a, s a).
During initial installation, and as long as no crack indications are detected during subsequent inspections, the same values of Puare assumed. However, after the initial operating period, even if no indications are detected by the nondestructive examination, an initiated crack (a,) is assumed to be present in each of the six disks at critical locations with a probability of Pu, for the evaluation of P2 ,. The default size was conservatively based on Siemens ultrasonic examination capability evaluation", if an indication is detected during the inspection, then Pu= ,
1, and the detocted indication size is used in the calculation of P .
w 4.7 MONTE-CARLO METHOD FOR PROBABILISTIC ANALYSIS:
For probabilistic computations, SPC has developed a numerical Monte-Carlo simulation procedure. Monte-Carlo method is a highly popular, simple and versatile technique for probabilistic analyses when multiple variables are associated with different types of statistical distributions. Since this method requires a large num-ber of computational operations, it is only now more feasible than in the past due to the availability of high speed computers, SIEMENs POWER CORPORATION FOSSIL DMSiON ENGINEERING DEPARTMENT January 9,1998 Rev,1 PAGE 15 oF 45 ER 9605NP Y
SIEMENS ER 9605NP i Two computer programs have been developed, one for calculating the probability of disk burst (Pg) and the second for calculating the probability of casing penetration given a disk burst (P,).
{ 5.0 PROBABILITY OF CASING PENETRATION FOR SPEEDS UP TO 120%
OF RATED SPEED (Pu):
Siemens LP turbines are designed with " crash rings". These rings which are part of the LP turbine casings, are designed to prevent extemal mist"es up to at least 120% of the rated speed.
Casing penetration occurs when the kinetic energy of the rotating disk fragment /s from an intemal burst exceeds the energy dissipated due to various factors such as blade crushing, blade bending, loss of blade mass due to break off, friction between missile fragment and inner casing structure, deformation of the stationary blade ring and inner casing up to breakage, and penetration through the outer casing structure Assumptions and mathematical models oeveloped to perform these calculations are based on experience and have been designed to yield maximum net energy and thus yield conservative results. For probabilistic analysis us!rg Mount Carl simulation, a tclal of 25 input variables are identified with appropriate statistical distributions.
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SIEMENS ER 9605NP 6.0 PROBABILITY OF A RUN AWAY OVERSPEED >120% (P,,):
Run away overspeed events >120% are due to failure of the overspeed protection system which consists of speed monitoring devices, trip devices and fast closura of steam stop and control valves.
The Limerick Unit 1 & 2 control system components that protect against overspeed i
events rems ln without modification. Thus, there is no change to P,ofrom current values.
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in general probability of overspeed is developed from the history of field experience combined with fault tree failure analyses. SPC has developed equations for the probability of runaway oversspeed as a function of the valve test interval. Further details are included in the proprietary version of this report.
s 4
7.0 DISCUSSION OF RESULTS:
A detailed discussion of the results for Limerick #1 and #2 is included in the proprietary version of the report. This discussion clearly illustrates that the unit can be safely operated for 100,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> between disk inspections provided no disk cracking is detected by the UT examinations.
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SIEMENS ER 9605NP 8.0 CONSERVATISM IN METHODOLOGY:
Some conservatism's used in this report's assumptions and the analysis are:
- 1. Residual compressive stresses introduced during manufacturing are conserva-tively assumed to be much lower than the actual values. The shrink fit and centrifuge.1 stresses during normal operation, when combined with the residual compressive stresses, will reduce the final stresses to well below the threshold for stress corrosion cracking.
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- 2. The creek initiation probabilities which are based on the ten and eight disk desigris are assumed for the new six-disk design. This is conservative because the older design disks did not have the beneficial compressive residual stresses that the new design has. The crack initiation probability for the new six disk design is expected to be practically zero.
- 4. The probability of achieving speeds up to 120% of rated speed during normal operating conditions is conservatively assumed to be 1.0. More realistically this probability is a small value typically less than about 2E-3' Speeds exceeding 107% to 110% by control system design are uncommon. Speeds above 100%
are limited by generator synchronization.
- 5. Although not a requirement, the internal disk burst probability under normal operation up to 120% speed is less than the NRC probability limit for an extemal missile up to about 100,000 hours0 days <br />0 hours <br />0 weeks <br />0 months <br /> of operation between inspections, provided no cracking is detected.
7.
- 8. The probabilities of both burst and casing penetration for a run-away overspeed event >120% of the rated speed are conservatively assumed to be 1.0 for all disks. In reality, only heavy pieces with the worst geometry of the burst disks at SIEMENS POWER CORPORATION FOSSIL DMSloN ENGINEERINo DEPARTMENT January 9,1998 Rev.1 PAGE 20 OF 45 ER 9605NP
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significantly higher than 120% speed would penetrate the casing below the final burst speed. And then less than 50% of those missiles would be thrown upward as downward trajectory missile. would impact balance of plant equipment only .,
such as the condenser.
- 9. Use of Siemens overspeed probability (Pw)value ados a conservatism factor of about two or more to tho OEM's value for the current system, and this OEM value is already above the performance based, recently updated value for con-trol systems at similar nuclear sites. Adequate time is available to respond to any change in original control system OEM reliability, should there be future change for the worse. With respect to original control system OEM calcuations, for O/0/0 valve tests inspections, the prnbability of an external missile due to overspeed is about 1/10 of the NRC limn.
9.0 REFERENCES
- 1. " Engineering Report ER-8402 Probability of Disk Cracking Due to Stress Corrosion -- Comanche Peak Unit 1" Utility Power Corporation Proprietary l Information, August 1984,
- 2. " Engineering Report ER 8605a Probability of Disk Cracking Due to Stress Corrosion -- Connecticut Yankee Replacement LP Rotors", Utility Power Corporation Proprietary Information, July 1986, Rev A, June 1987,
" Engineering Poport ER 8611 Turbine Missile Analysis for 1800 rpm Nuclear LP-Turbines with 44-inch Last Stage Blades", Utility Power Corporation Proprietary Information, July 1986, Rev 1, June 1987.
- 3. " Engineering Report ER-8503 Probability of Disk Cracking Due to Stress Corrosion - Grand Gulf Unit 1", Utility Power Corporation Proprietary information, March 1985.
" Energy Analysis in the Hypothetical Case of a Wheel Disk Burst in the LP Sections 1 to 3 of the New Design Series - Nuclear Power Plant Grand Gulf, 7153", Siemens Power Corporation Proprietary Information, June 1995.
" Proposed Change to the Operating License Closure and Deletion of License Condition 2.C (26) Turbine Disc Integrity, PCLO-94/01"
" Issuance of Amendment No.121 To Facility Operating License No NPF-29
- Grand Gulf Nuclear Station, Unit 1 (TAC No. M90673)." GNRI - 95/00083.
- 4. U.S. Nuclear Regulatory Commission, Regulatory Guide (RG) 1.115 U.S. Nuclear Regulatory Commission, NUREG-0800, " Standard Review Plan for the Review of Safety Analysis Reports for Nuclear Power Plants",
July 1981.
U.S. Nuclear Regulatory Commission, NUREG - 1048 including Appendix U
& Table U.1 SIEMENS POWER CORPORATION FOSSIL DMStoN ENGINEERING DEPARTMENT January 9.1999 Rev,1 PAGE 21 oF 45 IIR 9605NP
SIEMENS ER 9605NP _
- 5. S. T. Rolfe and S. R. Novak," Slow Bend KoTesting of Medium-Strength !
High Toughness Steels",in " Review of Developments in Plane Strain Frac-ture-Toughness Testing" ASTM STP 463, American Societ/ for Testing and Materials, Philadolphia,1970.
l 6 Oeynhausen, Roottger, Ewald, Schleithoff & Termuelhen, " Reliable Disk Type Rotors for Nuclear Power Plants"- Siemens Paper presented at the American Power Conference, April,1987.
- 7. Muehto, Kelenburg & Termuehlen, " Considerations to Achieve Reliable Long Time Turbine Operation" ASME 87-JPGC-Pwr-55.
- 8. Termuchlen, Schleithoff & Neumann," Advanced Disk-Type LP Turbine Rotors"- Paper presented at the EPRI Workshop - Stress Corrosion Crack-Ing in Steam Turbines on October 10-11,1990.
9 Roettger & Termuehlen," Disk Type LP Turbine Rotor Experiance", Pre-sented at 1993 International Joint Power Generation Conference.
- 10. N. G. Clark etc., ASME Paper " Procedures for Estimating the Probability of Steam Turbine Disc Rupture from Stress Corrosion Cracking", October 4-8, 1981.
- 11. McMinn etal, " Stress Corrosion Crack Growth in NICrMoV Turbine Disc Steels", NACE, Vol 41, No. 9, Sept.1985.
- 12. Fred Lyle, " Low Pressure Rotor Disc Cracking and Remaining Life Analysis", SwRI Report.
l
- 13. " Engineering Report ER-8401 Ultrasonic Disk inspection" Utility Power Cob poration Proprieta y Information, August 1984.
, T. Streiner, etc. " Ultrasonic In Service Inspection of Shrunk-on LP Turbine l Disks", EPRI NDE Nnter, July 16-19,1991.
l 14. " Engineering Ret 48611 Turbine Missile Analysis for 1800 rpm Nuclear l
LP-Turbines wit' .ch Last Stage Blades", Utility Power Corporation Pro-I prietary Ir.formi July 1986, Rev 1 June 1987,
- 15. DeCesare & Blevenue, "PECO Energy Limerick #1, TB.170x463 Low Pres-sure Turbine Wheel Missile Probabilities for Extended Valve Testing Inter-vals", December 9,1994.
- 16. DeCesare & Blevenue,"PECO Energy Limerick #2, TB.170x464 Low Pres-sure Turbine Wheel Missile Probabilities for Extended Valve Testing Inter-vals", December 13,1994.
- 17. " Probability of Missile G_.ieration in General Electric Nuclear Turbines -
Supplementary Report: Steam Valve Surveillance Test Interval Extension -
Non-Proprietary Version GET-8039.1", September 1993.
- 18. Racic & Lehnst," Theoretical Basis And Calculations For Extending The Interval Between Testing Of The Turbine Va'.ves", Siemens Power Corpora-tion Proprietary Information, August 11,1992, slEMENS POWER CORPORATION FOSSIL DMSION ENGINEERINo DEPARTMENT January 9,1998 Rev.1 PAGE 22 OF 45 ER 9S05NP g <
SIEMENS ER 9605NP -
APPENDIX OF TABLES AND FIGURES List of Tables:
Table 1. Tangential Surface Stress Levels of Disk #1 With & Without Additional Measures (Also see Figure 9).
Table 2.
Table 3.
Table 4.
I List of Figures:
Figure 1 Figure 2 Figure 3.
Figure 4. Siemens Design Evolution from Ten Disks to Six Disks Configuration.
Figure S. Schematic Showing Favorable and Unfavorable Nuclear Tur-bine Unit Orientation.
Figure 6. Typical Stress Corrosion Crack Growth Rate vs. Stress inten-sity Factor.
Figure 7. Influence of 0.2% Offset Yield Strength on Crack initiation Time in Pure Water for LP Disk Materials.
Figure 8. Stress Corrosion Crack initiation of LP Turbine Rotor Steels, 0.2% Yield Strength Less than 1000 Mpa, slEMENS POWER CORPORATION FOSSIL DMSloN ENGINEERING DEPARTMENT January 9,1998 Rev.1 PAGE 23oF 45 ER 960$NP
SIEMENS ER9605NP Figure 9.
Figure 10.
Figure 11.
Figure 12.
Figure 13.
Attachment A:
SIEMENS POWER CORPORATION FOSSIL DMSION ENGINEERINO DEPARTMENT January 9,1998 Rev.1 PAGE 24 OF 45 ER 960$NF
SIEMENS ER 9605NP TABLE 1 TANGENTIAL SURFACE STRESS LEVELS OF DISK #1 WITH & WITHOUT ADDITIONAL MEASURES.
Sourco of Stress / Stress Reduction Tangential Stress Levels Mpa (Ksi).
Desbn Featuro l Manufacture Toctink ue t Effect Disk Rim Hub Boro Keyway Centrifugal and Slirink Fit Stresses at +300 4-540 4800 Rated Spood without Additional Measures (44) (+00) .. (+110) ,,
Heat Residual Stresses due to -100 -200 -400 Treatment Heat Treatment ( 15) (-29) (-59)
Shot Residual Stresses due to -
-350 -
Pooning Shot Pooning
(-51)
Rolling Residual Stresses due to - -
-520 s Rolling after Shrinking
.' (-76)
Tangential Stresses with all +200 4200
-200 St/ess Patterns Superimposed (29)
(29) (-29) -
SIEMENS POWER CORPORATION FOSSIL DMSION ENGINEERING DEPARTMENT January 9,1990 Rev.1 PAGE 25 OF 45 ER 9605NP
SIEMENS ER 9605NP TABLE 2 l
SIEMENS POWER CORPORATION FOSSIL DMSION ENGINEERING DEPARTMENT January 9,1998 Rev.1 PAGE 26 OF 45 ER 960$NP J
SIEMENS ER 9605NP T (BLE 3 SIEMENS POWER CORPORAT)ON FOSSIL DMSION ENGINEERING DEPARTMENT January 9,1996 Rev.1 PAGE 27 OF 45 ER 900$NP
SIEMENS ER 9605NP TABLE 4 I
I 1
t i
SIEMENS POWER CORPORATION FOSSIL DMSION ENGINEERING DEPARTMENT January 9,1998 Rev.1 PAGE 28 OF 45 ER 9605NP l ..
SIEMENS ER 9605NP
_ _ _ . .~
FIGURE 1 i
'SIEMENS POWER CORPORATION FOSSIL OMSION ENGINEERING DEPARTMENT
- January 9,1998 Rev 1 PAGE 29 OF 45 ER 960$NP
SIEMENS i ER 9605NP FIGURE 2 i
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SIEMENS ER 9605NP FIGURE 3 w
SIEMENS POWER CORPORATION FOSSIL DMSION ENGINEERING DEPARTMENT January 9,1998 Rev.1 PAGE 31 OF 45 ER 9605NP T --
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SIEMENS ER 9605NP FIGURE 4 i
SIEMENS DESIGN EVOLUTION FRGi!, TEN DISKS :
TO SIX DISKS CONFIGURATION.
\ 7 8 '
_q_ldJ3Qv - f ,
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Ten Disk Rotor Design D .
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l- N %g i i
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SIEMENS ER 9605NP -
FIGURE 5 SCHEMATIC SHOWING FAVORABLE AND UNFAVORABLE NUCLEAR TURBINE UNIT ORIENTATION, l
Unfavorable Orientation Favorable Orientation l 1
\ Reactor
\
Reactor
\
4 4
Turbino Turbino T
i SIEMENS POWER CORPOP.ATION FOSSIL DMSION ENGINEERING DEPARTMENT January 9,1998 Rev.1 PAGE 33 OF 45 ER 9005NP
SIEMENS ER 9605NP FIGURE 6 TYPICAL STRESS CORROSION CRACK GF.OWTH RATE VS. STRESS INTENSIT( FACTOR.
Specimen Under a Static Load in an Aggressive Enviornment K '
I 7c I
g Region 3 >
a Approaching Final i Failure E
eg. -
2 0
is r E'
\
Region 2 r Constant Grow 4h Rate
) i Regioni p K Dependent K Region Isco 45 -
Stress intensity Factor, K SIEMENS POWER CORPORATION FOS 31L DMS!ON ENGINEERING DEPARTMEffT January 9, '998 Rev.1 PAGE 34 OF 45 ER 9605NP
SIEMENS ER 9605NP FIGURE 7 I
INFLUENCE OF 0.2% OFFSET YlELD STRENGTH I ON CRACK INITIATION TIME IN PURE WATER FOR LP DISK MATERIALS.
Hours 8
10 - - y h
f4o Crack initiation ^ ' ~~
Stress CorrosionJ
.- t ,' Cracking due to h t,
j, L % liydrogen f< p' ?['7[ j)f ; -
t gf' /f _
Embrittlement '... ; .
c
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E Aluminum Oxide Enclosures Suricce Enclosures
/ .
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, y 4
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g m
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g .
wa
~
Pure Water I~
Smooth and Notched Specimens *> /lggf v ts>
'/'/.1 e
. .09 to 1.0 Test Stress to f+,/
Yield Strength Ratio .' '
r;*Ma
- ,+
4 p')jZ, . .-
4 e<
?( o h 10,- i c . i w&f"dAl 1
~
i k ,
600 800 1000 1200 1400 troa i i i i i i i i i i i i 100 120 140 160 180 200 Ks1 Yield Strength' SIEMENS I'OWER CORPORATION FOSSIL DIVISION ENGINEERING DEPARTMENT January 9,1998 Rev.1 PAGE 35 OF 45 ER 9605NP
SIEMENS ER 9605NP FIGURE 8 STRESS CORROSION CRACK INITIATION OF LP TURBINE ROTOR STEELS WITH 0.2% YlELD STRENGTH LESS THAN 1000 MPA.
^ Stress . Stress Corrosion Crack i 0.2% Yield Strengtti Initiation High Purity Water RsccI>1,1
{
1,2 -
Condensing Steam Rscci>0,9 7 . .. ;
~'a.
l 0,9 - ;g ,
~' No Pits -
Severe Corros, ton 5'
4 & .
Conditions
- Rscct>0,S-0,6 -
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SIEMENS POWER CORPORATION FOSSIL DMSION ENGINEERING DEPARTMENT January P,1998 Rev.1 PAGE 36 OF 45 ER 9605NP
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SIEMENS ER 9605NP _
FIGURE 9 l
f SIEMEN3 POWER CORPORATION FOSSIL GMSION ENGINEERING DEPARTMdNT January 9,1998 Rev.1 PAGE 17 OF 45 ER 9605NP
SIEMENS ER 9605NP FIGURE 10 i
SIEMENS POWER CORPORATION FOSSIL DMSION ENGINEERING DEPARTMENT January 9,1998 Rev.1 PAGE 38 OF 45 ER 9605NP
SIEMENS
,, ,, osse FIGURE 11 SIEMENS POWER CORPORATION FOSSIL DMSiON ENGINEERING DEPARTMENT January 9.1990 Rev.1 PAGE 39 OF 45 ER 960SNP
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SIEMENS ER 9605NP FIGURE 12 l
SIEMENS POWER CORPORATIO;4 FOSSIL DIVISION ENGINEERING DEPARTMENT January 9,1998 Rev.1 PAGE 40 OF 45 ER 9605NP
SIEMENS
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ER 9605NP -
. FIGURE 13 I i
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SIEMENS POWER CORPORATION FOSSIL DNISION ENGtNEERING DEPARTMENT January 9,1998 Rev.1 PAGE 41 OF 45 ER 9605NP
e SIEMENS 4N-ER 9605NP ATTACHMENT A SIEMENS POWER CORPORATION FOSS!L DMSION ENGINEERING DEPARTMENT i January 9,1998 Rev.1 PAGE 42 OF 45 '
ER 9605NP l
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SIEMENS POVvER CORPORATION FOSSIL DMSION ENGINEERING DEPARTMENT January 9,1998 Rev.1 PAGE 43 OF 45 ER 9605NP
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l SIEMENS POWER CORPORATION FOSSIL DMSION ENGINEERING DEPARTMENT January 9,1998 Rev.1 PAGE 45 OF 45 ER 9605NP
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6 t I L
ENGINEERING REPORT ER-8503
- PROBABILITY OF DISK CRACKING DUE .
TO STRESS CORROSION ~
- GRAND GULF UNIT 1
,e e
4
'l.
ENGINEERING REPORT ER-8503 -
l PROBABILYrY OF DISK CRACKING DUE TO STRESS CORROSION l
GRAND GULF UNIT I e
t MARCII 1985 -
l' e
PROPRIETARY INFORMATION OF -
UTILITY POWER CORPORATION Not to be reproduced, copied of dissocnineted without the est toss ptfor written consent of UtHity Power Corporetloct.
Siemens Power Corporation I
Engineering Report ER 8503 Probability of Disk Cracking Due to Stress Corrosion, Grand Gulf Unit 1 March 1985 This engineering reoort contains propcictary information of Siemens Power Corporation. It was provided to Entetgy Operations, Inc. for the Grand Gulf Nuclear Station, Unit 1 and is considered as proprietary property of the utility. This document was submitted to the NRC previously on the Entergy's docket.
Page 1 of 1
i ENGINEERING REPORT ER-8505A
{-
' PROBABILITY OF DISK CRACKING DUE '
TO STRESS CORROSION CONNECTICUT YANKEE
[-.
. - Utility PowerCorporation b)
)
l 9
ENGINEERING REPORT ER-8605a PROBADILITY OF DISK CRACKING DUE TO STRESS CORROSION l
! CONNECTICUT YANKEE REPLACEMENT LP ROTORS ,
JULY 1986 ,
Revision 1, June 1987 9
PROPRIETARY INFORMATION OF
. UTILITY POWER COr.POR ATION Not to be reproduced cooled or dissaminated without the express prior written consent c?
, Utility Power Corporation.
N J
t
Sirm:n3 Pcw:r Corporation Engineerinc deport ER - 8605a Probability of Disk Cracking Due to Stress Corrosion, Connecticut Yankee Replacement LP Rotors July 1986, Revision 1 (June 1987)
This engineering report contains proprietary information of Slemens Power Corporation it was provided to Connecticut Yankee Atomic Power Company (Northeast Utilities) for the Connecticut Yankee (Haddam Neck) Nuclear Plant and is considered as proprietary property of the utility.
This document was submitted to the NRC previously on the Northeast Utilities' docket.
l l-Page 1 of 1
i
.c l
L ENGINEERING REPORT ER 8402
- PROBABILITY OF DISK CRACKING DUE -
. TO STRESS CORROSION COMANCHE PEAK UNIT 1
t
- e
, Utiliay PowerCorporaaion k .J ENGINEERING REPORT ER-8402 i
PROBABILITY OF DISK CRACKING l
DUE TO STRESS CORROSION l
l' COMANCHE PEAK UNIT I Ausrust 1984 4
PROPRIETARY INFORMATION OF UTILITY POWER CORPORATION f.0 t to be teproduced, copied Or disseminated without the esprett $*f lof written Consent of
~
Utill%Y P0 wet COfpOfstlOn.
i
Si m:n3 Psw:r Corporation-Engineering Report ER-8402 Probability of Disk Cracking Due to Stress Cort asion, Comanche Peak Unit 1 August 1984 This engineering report contains psprietary information of Ssmens Power Corporation, it was provided to _ Texas Utilities for the Comanche Peak Steam Electric Station Unit 1 and is considered as proprietary property of the utility. This document was submitted to the NRC previously on the Texas Utilities' docket.
l Page 1 of 1 g ,
,,7- , , - - , - - - - - - - - - - - - -
5
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UPC ENGINEERING REPORT ER 8611
-- TURBINE MISSILE ANALYSIS FOR 1800 RPM -
NUCLEAR LP-TURBINES WITH 44-INCH -
LAST STAGE BLADES k
O Technical Report Turbine Missile Analysis for 1800 rpm Nuclear LP-Turbines with 44-inch Last O Stage Blades K W U / T M / T D M / 86 / 024
. U P C Engineering Report ER 8611 Revision I / June 87 ,
V i
i e
0 .
. i 6
UtilityPower P ]J Corporation i-1 PROF 881ETARY INFORMATION OF UTILITY POWER CORPORATION l
u i to de ..<ooo..o. ..o..a or ci-in.ieo without the capress pr6ot weltt+n consent of Utility Power Corpot. tion.
a SI:m:n3 Pcw:r Ccrponti n UPC Engineering Report ER - 8611 KWU/TM/TDM/86/024 Turbine Missile Analysis for 1800 rpm Nuclear LP - Turbines with 44 Inch Last Stage Blades -
June 1987, Revision i This engineering report contains proprietary it. formation of Siemens Power Corporation. It was provided to Connecticut Yankee Atomic Power Company (Northeast Utilities) for the Connecticut Yankee (Haddam Neck) Nuclear Plant and is considered as proprietary property of the utility.
This document was submitted to the NRC previously on the Northeast Utilities' docket.
l l
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Page 1 of 1
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