ML15261A234
| ML15261A234 | |
| Person / Time | |
|---|---|
| Site: | Oconee  |
| Issue date: | 09/09/1999 |
| From: | Joseph Sebrosky NRC (Affiliation Not Assigned) |
| To: | NRC (Affiliation Not Assigned) |
| References | |
| REF-GTECI-***, REF-GTECI-NI, TASK-*****, TASK-OR NUDOCS 9909140168 | |
| Download: ML15261A234 (17) | |
Text
ON REG(,
UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 Septeniber 9, 1999 LICENSEE:
Duke Energy Corporation (Duke)
FACILITY:
Oconee Nuclear Station, Units 1, 2, and 3
SUBJECT:
SUMMARY
OF MEETING BETWEEN THE U.S. NUCLEAR REGULATORY COMMISSION (NRC) STAFF AND DUKE REPRESENTATIVES REGARDING FATIGUE RELATED ISSUES FOR THE OCONEE LICENSE RENEWAL APPLICATION (LRA)
On August 25, 1999, representatives of Duke met with the NRC staff at Rockville, Maryland, to discuss issues associated with fatigue for the LRA for Oconee Units 1, 2, and 3. A list of meeting attendees is provided in Enclosure 1. The purpose of the meeting was to discuss Duke's proposed responses to safety evaluation report (SER) open items 4.2.3-1 and 4.2.3-2.
Duke's proposed responses are provided in Enclosure 2.
Open item 4.2.3-1 relates to the fracture mechanics analysis status. In its LRA Duke identified flaw locations that were evaluated using the flaw growth procedures of ASME Section XI for the period of extended operation. The review identified several general flaw locations that were not demonstrated as acceptable for the number of controlling design basis transients. Duke's proposed response provided an update to the status of the analysis. Subsequent to the submittal of the LRA, several of the flaw locations were reanalyzed and found to be acceptable for the number of controlling design basis transients. For those locations that had not been reanalyzed, Duke stated that it either planned to do reanalysis or to replace the components, in which case reanalysis is not needed.
The only reanalysis that Duke has not completed to date is for the pressurizer upper head to shell weld at Unit 2. Duke stated that any revised design cycle limit resulting from reanalysis will be managed for this location by the Oconee thermal fatigue management program. The staff found the proposed response to SER open item 4.2.3-1 to be acceptable.
Subsequent to the meeting, the staff reviewed some of the calculations that were reanalyzed.
Any questions that the staff has regarding these calculations will be pursued separate from license renewal because the calculations are part of Oconee's current licensing basis. The staff expects Duke to formally submit its response to SER open item 4.2.3-1. The resolution of this open item will be documented in the final safety evaluation report for the Oconee LRA.
Open item 4.2.3-2 relates to generic safety issue (GSI) 190, "Fatigue Evaluation of Metal Components for 60-year Plant Life." The staff provided Duke with three options in its SER to resolve this issue for Oconee. The three options were: 1) develop an aging management program that incorporates a plant-specific resolution of GSI-190, 2) submit a technical rationale which demonstrates that the current licensing basis will be maintained until some later point in time at which point one or more reasonable options would be available to adequately manage the effects of aging, or 3) If GSI-190 is resolved prior to the period of extended operation, Oconee may follow the resolution of the GSI.
9909140168 990909 PDR ADOCK 05000269 P
PDR September 9, 1999 Duke's proposed response followed option 2. Duke stated that it considers modification of the Oconee thermal fatigue management program to account for environmental effects on fatigue life to be a feasible option to resolve GSI-190 for Oconee. The staff stated that this option would present it difficulties in closing out the SER open item because the selection criteria for the appropriate locations and the environmental penalty factors to be applied have not been specified. Duke stated that it did not want to specify the location and penalty factors to be used at this time because of the continuing research in this area.
The staff stated that Duke could pick the locations based on NUREG/CR-6260 and the penalty factors based on guidance it had provided the Nuclear Energy Institute in an August 6, 1999, letter. The staff stated that if GSI-190 can be resolved for Oconee on a plant-specific basis then it would lead to less regulatory uncertainty regarding the issue in the future. Duke stated that it would consider the information exchanged during the meeting and determine if it will revise its proposed response to SER open item 4.2.3-2. Nevertheless, Duke will provide a formal response to SER open item 4.2.3-2 by October 15, 1999, in accordance with the Oconee LRA schedule.
A draft of this meeting summary was provided to Duke to allow them the opportunity to comment on the summary prior to issuance.
Joseph M. Sebrosky, Project Manager License Renewal and Standardization Branch Division of Regulatory Improvement Programs Office of Nuclear Reactor Regulation Docket Nos. 50-269, 50-270, and 50-287
Enclosures:
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OFFICIAL RECORD COPY
0I Oconee Nuclear Station (License Renewal) cc:
Mr. Larry E. Nicholson Ms. Lisa F. Vaughn Duke Energy Corporation 422 South Church Street Oconee Nuclear Site Mail Stop PB-05E P. 0. Box 1439 Charlotte, North Carolina 28201-1006 Seneca, South Carolina 29679 Anne W. Cottingham, Esquire Ms. Karen E. Long Winston and Strawn Assistant Attorney General 1400 L Street, NW.
North Carolina Department of Justice Washington, DC 20005 P. 0. Box 629 Raleigh, North Carolina 27602 Mr. Rick N. Edwards Framatome Technologies L. A. Keller Suite 525 Manager - Nuclear Regulatory Licensing 1700 Rockville Pike Duke Energy Corporation Rockville, Maryland 20852-1631 526 South Church Street Charlotte, North Carolina 28201-1006 Manager, LIS NUS Corporation Mr. Richard M. Fry, Director 2650 McCormick Drive, 3rd Floor Division of Radiation Protection Clearwater, Florida 34619-1035 North Carolina Department of Environment, Health, and Senior Resident Inspector Natural Resources U. S. Nuclear Regulatory Commission 3825 Barrett Drive 7812B Rochester Highway Seneca, South Carolina 29672 Regional Administrator, Region GreIry oison U. S. Nuclear Regulatory Commission Mail Stop EC-12R Atlanta Federal Center P. 0. Box 1006 61 Forsyth Street, SW, Suite 23T85 Charlotte, North Carolina 28201-1006 Atlanta, Georgia 30303 Robert L. Gill, Jr.
Virgil R. Autry, Director Duke Energy Corporation Division of Radioactive Waste Management Mail Stop EC-12R Bureau of Land and Waste Management P. 0. Box 1006 Department of Health and Charlotte, North Carolina 28201-1006 Environmental Control RLGILL@DUKE-ENERGYCOM 2600 Bull Street Columbia, South Carolina 29201-1708 Douglas J. Waltes Nuclear Energy Institute W. R. McCollum, Jr., Vice President 1776 I Street, NW Oconee Site Suite 400 Duke Energy Corporation Washington, DC 20006-3708 P. 0. Box 1439 DJW@NEl.ORG Seneca, SC 29679 Chattooga River Watershed Coalition P. O. Box 2006 Clayton, GA 30525
NRC MEETING WITH DUKE ENERGY CORPORATION TO DISCUSS LICENSE RENEWAL ISSUES ASSOCIATED WITH FATIGUE ATTENDANCE LIST AUGUST 25, 1999 NAME ORGANIZATION ROBERT GILL DUKE ENERGY DOUG WALTERS NEI JENNY WElL MCGRAW-HILL ROBERT NICKELL EPRI CONSULTANT MICHAEL HENIG VIRGINIA POWER NITIN SHAH VIRGINIA POWER FRED POLASKI PECO ENERGY J. MICHAEL DAVIS DUKE ENERGY GREG ROBISON DUKE ENERGY JOHN CAREY EPRI NORIHISA YUKI NRC\\NRR\\DRIP\\RLSB.,
NANCY CHAPMAN SERCH\\BECHTEL PT KUO NRR\\DRIP\\RLSB COLLEEN AMORUSO NUS INFO. SERVICES JIT VORA NRC\\RES\\DET\\MEB SAM LEE NRC\\NRR\\DRIP\\RLSB KAMAL MANOLY NRC\\NRR\\DE\\EMEB CHRIS GRIMES NRC\\NRR\\DE\\EMEB ALLEN HISER NRC\\NRR\\DE\\EMCB JOHN FAIR NRC\\NRR\\DE\\EMEB GENE IMBRO NRC\\NRR\\DE\\EMEB
Oconee License Renewal Application NRC Safety Evaluation Report Fracture Mechanics Analysis Status SER Open Item 4.2.3-1 The applicant indicated that these locations would be managed by the ONS FMP. The adequacy of this program to address the flaw evaluation TLAA cannot be determined without additional information. The applicant should provide the following information relating to the locations identified in Section 5.4.1.2 of Exhibit A of the LRA that could not be demonstrated as acceptable for the number of controlling design basis transients:
- Characterize the indications identified by the ISI for each of the locations listed (i.e.,
nature, length, through-wall extent and through-wall location);
- From the results of successive ISI of the same flaw locations, characterize the extent of growth of the indication(s) as indicated by the successive examinations;
- For each of the fracture mechanics analyses, identify the transient and number of cycles assumed in the analyses, and the ASME Code Section XI, IWB-3600 criteria that was not satisfied at the end of the license renewal period;
- As of January 1, 1999, what is the status of the actual number of transient cycles for each location, the plant status regarding effective-full-power-years (EFPY), and the estimated EFPY at the end of the license renewal period?
- If the transient cycle count approaches or exceeds the allowable design limit, identify the corrective action steps that could be taken.
Duke Response to SER Open Item 4.2.3-1 Section 5.4.1.2 of the license renewal application (LRA) describes time-limited aging-analyses (TLAA) related to flaw growth acceptance for the reactor coolant system and Class 1 components at Oconee. As described in the LRA, inservice inspection (ISI) at Oconee, in accordance with ASME Section XI ISI requirements, has lead to the identification of crack-like indications, primarily in welds. The fracture mechanics analyses used for flaw acceptance through the current license period have been reviewed for acceptability for the period of extended operation.
This review identified several general flaw locations that could not immediately be demonstrated to be acceptable for the number of controlling design basis transients, but which will continue to be managed by the Oconee Thermal Fatigue Management Program.
Since the submittal of the application in July 1998, most of the locations identified in Section 5.4.1.2 of Exhibit A of the LRA that could not be demonstrated to be acceptable have been reanalyzed and found acceptable for the number of controlling design basis transients. The following locations were not reanalyzed: flaw in the pressurizer upper head to shell weld at Unit 2, flaw in the weld that connects the OTSG upper head to tubesheet at Unit 2, and the discontinuities in the CRDM motor
-1 FMA rev 1 draft 8-23-99.doc
0I tube housings at Units 1 and 2. At present, the pressurizer upper head to shell weld at Unit 2 is being evaluated for the period of extended operation. The current design cycle limit and any revised design cycle limit resulting from reanalysis will be managed for this location by the Oconee Thermal Fatigue Management Program.
The OTSGs at Unit 2 and CRDMs at Units 1 and 2 are in the process of being replaced, thus reanalysis was not needed. Therefore, all locations, with the exception of the flaw in the pressurizer upper head to shell weld on Unit 2, are acceptable for the period of extended operation. Table 1 provides a range of updated information (i.e., controlling transients and extent of growth) associated with each of the locations.
Note that Table 1 does not contain information associated with the CRDM motor tube housing. The CRDM motor tube housing indications are described in the BAW topical report entitled "A Study of Discontinuities in Control Rod drive Motor Tube Extensions," BAW-10047, Revision 1, August 1972. A fracture mechanics analysis, which applies to the Type A drives at Oconee Units 1 and 2, was performed to show that the CRDM motor tube extension fabrication discontinuities were acceptable for the design life of the plant. The CRDM fracture mechanics analysis will not be updated for license renewal since the Type A CRDMs at Units 1 and 2 will all be replaced with Type C drives prior to the end of the current term of operation. The Type C drives do not contain the subject fabrication discontinuities.
-2 FMA rev 1 draft 8-23-99.doc
Table
- 1.
Summary of Specific Oconee Fracture Mechanics Calculations of Flaw Indications Component Flaw Unit Flaw Size Controlling Inservice Inspection Results Controlling Total number of Accumulated Location Per IWA-3000 Transients design Transient Transient transient Cycles the Cycles when cycle limit indication is indication was for location acceptable for observed a(in.)
t (In.)
l(In.)
Pressurizer near 1
1.075 7.0 2.15 Heatup and B&W first reported this indication 360 448 88 heater bundle Cooldown in Outage 7 in 1983. The indication was sized at 12.33% a/t.
Monitoring of the indication in three successive outages, (Outage 9 March 1986, Outage 11 February 1989 and Outage 13 September 1991) showed no increase in size.
Pressurizer support 1
0.7 3.5 1.35 Heatup and B&W first reported two 360 425 65, lugs Cooldown unacceptable indications in Outage 6 in 1981. Fracture mechanics analysis accepted these indications.
Larger of two similar The support lug welds were indications reexamined in Outage 7 in 1983 and a second fracture mechanics analysis performed. The indications were acceptable. No monitoring was performed.
Steam generator at 1
0.57 8.05 6.1 Heatup and B&W first reported this indication 120 207 87 the upper head to Cooldown in Outage 12 in 1990. The tubesheet region indication was sized at 7.1% alt.
Monitoring of the indication in Outage 14, 1992 and Outage 17, 1997 showed no increase in size.
-3 FMA rev 1 draft 8-23-99.doc
Table 1. Summary of Specific Oconee Fracture Mechanics Calculations of Flaw Indications Component Flaw Unit Flaw Size Controlling Inservice Inspection Results Controlling Total number of Accumulated Location Per IWA-3000 Transients design Transient Transient transient Cycles the Cycles when cycle limit Indication is indication was for location acceptable for observed a(In.)
t (in.) 1(In.)
Reactor vessel at the 1
1.15 12.0 4.4 Heatup and B&W first reported thirteen Not Applicable Not Applicable Not Applicable reactor vessel flange Cooldown unacceptable indications in Outage to shell region 9 in 1986. The indications were re Inservice evaluated in 1987 and were finally Leak and resolved as geometry. No further Hydro action was taken.
Core flood tank 2
1.30 2.7 1.65 Heatup and B&W first reported fifteen 360 455 95 dump valve to Cooldown unacceptable indications in Outage nozzle 6 in 1983. Fracture mechanics analysis accepted these indications.
Largest flaw The indications were re-sized in reported is a=1.30 Outage 7 in 1985 with different inches and 1.65 transducers and consequently, inches twelve indications were found unacceptable. A second fracture mechanics analysis accepted these indications. Nuclear Energy Services (NES) was contracted to monitor these indications in Outage 8 in 1986. NES recorded nineteen indications of which only four were unacceptable. These four indications were correlated with the previous B&W data. Review of both sets of data show that the flaws had not increased in size.
-4 FMA rev 1 draft 8-23-99.doc
Table 1. Sunnary of Specific Oconee Fracture Mechanics Calculations of Flaw Indications Component Flaw Unit Flaw Size Controlling Inservice Inspection Results Controlling Total number of Accumulated Location Per IWA-3000 Transients design Transient Transient transient Cycles the Cycles when cycle limit indication is Indication was for location acceptable for observed a(in.)
t (in.)
1(in.)
1 Pressurizer upper 2
0.55 4.75 7.0 Heatup and B&W first reported two 240 279 39 head to shell region Cooldow unacceptable indications in Outage 1 in 1976. Fracture mechanics LOCA analysis performed on the larger of Larger of two similar the two indications shows it indications acceptable. Subsequent examinations in Outage 2 (1977).
Outage 3 (1979) and Outage 4 (1980) show no flaw growth.
-5 FMA rev 1 draft 8-23-99.doc
Oconee Nuclear Station NRC Safety Evaluation Report Duke Response to SER Open Item 4.2.3-2 (Generic Safety Issue (GSI) - 190)
Open Item 4.2.3-2 Since GSI-190 has not been resolved, the staff requested, in RAI 1.5.5-1, that the applicant discuss how it satisfies the relevant portion of paragraph 54.29 of the license renewal rule as discussed in the statement of considerations (SOC) (60 FR 22484, May 8, 1995) in the absence of the staff's endorsement of EPRI Report TR-105759. The applicant did not provide a technical rationale addressing the adequacy of components in the RCP boundary considering environmental fatigue effects pending the resolution of GSI-190. In its response to the RAI, the applicant stated that the concerns of GSI-190 are not directly related to the ONS thermal fatigue design and licensing basis. The applicant further indicated the application contains its technical rationale for concluding that the effects of thermal fatigue will be adequately managed for the period of extended operation or until GSI-190 is resolved. On this basis, the applicant concluded that the relevant portions of 50.29 of the license renewal rule as discussed in the statement of considerations (60 FR 22484, May 8, 1995) are met by the ONS FMP. The staff does not agree with the applicant's reasoning. As discussed above, the staff assessment for GSI 166 found that there is sufficient conservatism in the CLB for the 40-year design life.
However, this conclusion could not be extrapolated beyond the current facility design life. As a consequence, the staff recommended that a sample of components with high usage factors be evaluated using the latest available environmental fatigue data for any proposed period of extended operation. The staff also initiated GSI-1 90 to further evaluate this issue for license renewal.
On the basis of the preceding discussion, the staff concludes that the applicant's TLAA of the RCS is not adequate to address the fatigue concerns for operation beyond the current design life of 40 years. The applicant must either develop an aging management program that incorporates a plant-specific resolution of GSI-190 or submit a technical rationale which demonstrates that the CLB will be maintained until some later point in time in the period of extended operation, at which point one or more reasonable options would be available to adequately manage the effects of aging. If GSI-190 is resolved prior to the period of extended operation, the applicant may follow the resolution of the GSI.
GSI-190 draft 8-13-99 R 8-25-99G81 190 drA 8 13 99. 8 2s 99.
00 Duke Response to Open Item 4.2.3-2:
Overview In response to SER Open Item 4.2.3-2, the Oconee Thermal Fatigue Management Program can be modified in the future to incorporate a plant-specific resolution of GSI 190. GSI -190 pertains to the adequacy of fatigue design life when environmental effects are considered for light water reactor components beyond a 40 year operating period.
The purpose of proposing this future modification to the Thermal Fatigue Management Program is to offer a technically feasible option for resolving GSI-190 for Oconee which would assure that the current licensing basis is maintained during extended period of operation when modified design rules may show that operational fatigue is no longer bounded.
The current Oconee Thermal Fatigue Management Program relies on cycle counting to assure compliance with the current licensing basis. This technique has been accepted by NRC in the Oconee Safety Evaluation Report in Section 4.2.3.4. Any modifications to the Oconee Thermal Fatigue Management Program to account for environmental effects on fatigue life should consider the practical and reliable aspects of cycle counting.
Section 5.4.1 of the Oconee License Renewal Application provides further specifics on the Oconee design cycle basis.
Future modifications to the Oconee Thermal Fatigue Management Program will adjust the allowable design cycles limits being tracked by the program. These adjustments will involve the use of an environmental penalty factor and will be applied to selected, appropriate locations. The selection criteria for the appropriate locations and the environmental penalty factor remain to be agreed upon by Duke and the NRC prior to 2013. Further details on the process to modify the design cycle limits and the Thermal Fatigue Management Program are provided in the following discussion.
Details The current Oconee Thermal Fatigue Management Program relies on cycle counting to assure compliance with the current licensing basis. This technique has been accepted by NRC in the Oconee Safety Evaluation Report in Section 4.2.3.4. Any modifications to the Oconee Thermal Fatigue Management Program to account for environmental effects on fatigue life should consider the practical and reliable aspects of cycle counting.
Current Practice - In the analysis basis, a piecewise linear relationship exists between design c -les and cumulative usage factor which is defined by the Code. The relationsuip between design cycles and cumulative usage factor is considered piecewise linear because each stress range pair associated with a given transient produces its own linear rate. When pieced together these sets of stress range pairs add up to a value for an incremental usage at an allowable number of design cycles for that transient. The sum of all of the incremental usage factors for all of the transients will equal the cumulative usage factor (CUF) at the design number of occurrences of all of the transients.
GSI-190 draft 8-13-99 R 8-25-99G1 190 drAft R 3 C9 R R 21 a Figure I shows an illustrative transient where two stress range pairs are included in the transient of interest, giving a bi-linear relation between the number of cycles and usage factor. When pieced together the usage factor value at a given number of cycles is determined. Also it should be noted that the cumulative usage factor base for this transient is not zero. The base is the sum of the usage factors for all other transients.
Each individual transient thus contributes to the overall cumulative usage factor through its own set of piecewise rates. In Figure 1, by including the usage factor value for this transient with all others, the overall component design cumulative usage factor is determined. (For convenience, the transient of interest is shown as the last in the sum producing the CUF. This is an allowed technique since no modification is being made at this time to any stress range magnitudes or postulated occurrences, hence there is no order dependency.)
From the design, the postulated cycles for each appropriate design transient are known.
These cycles are the actual evaluated cycles and hence are the analysis allowable limit and are tracked via the Thermal Fatigue Management Program. Figure 2 shows the actual accumulation of cycles for an illustrative transient over time. The original analysis allowable cycle limit is noted. Figure 2 also shows a conservative projected cycle accumulation rate for 60 years of operation. In this example, the projection does not exceed the allowable number of cycles for the 60 year period.
Proposed Modified Practice - Specifically, a modification to the number of allowable design cycles will accommodate issues associated with environmental effects on fatigue life (also referred to as environmentally assisted fatigue). Accounting for environmental effects on fatigue life requires the application of an environmental penalty factor to the design. Current industry thinking on the analysis basis associated with environmental effects on fatigue life causes penalties to be applied to cumulative usage factor values determined during design analysis. This environmental penalty factor only needs to be applied to the usage factors for specific transients for selected components in order to find the lowest number of acceptable cycles for a given transient. The final focus will be to develop a modified analysis allowable cycle count limit to cover all RCS components that are managed by the Oconee Thermal Fatigue Management Program. The determination of the most limiting component for each transient can be made by examining the sensitivity of the individual transient on a component's CUF. Several components may require analytical examination in order to thus determine the most limiting component for each transient.
Figure 3 illustrates how the environmental penalty factor affects the incremental usage factor for an example transient. The penalty factor results in an increase in the rate of usage per cycle, thus for a given number of cycles, the incremental usage factor with the penalty factor becomes greater.
In this manner, this new Environmental Penalty CUF can be compared to the 1.0 Code allowable, and if greater, a new limit for the transient in question can be set such that this GSI-190 draft 8-13-99 R 8-25-99S1 190 does not occur. Further details and different possible outcomes of this exercise are given below.
The exercise of applying the environmental penalty factor and comparing the projected cycles to any modified analysis allowable cycle limit for years 40 through 60 would need to be performed at an appropriate time before year 40. If the projections will exceed the reduced allowables prior to 60 years of operation, further detailed planning and management is required within the Thermal Fatigue Management Program. The remaining margins identified by the projections will establish the urgency of required corrective actions. As with the current Oconee Thermal Fatigue Management Program, it remains the responsibility of the utility to maintain operation within analyzed limits.
Examples of Proposed Modified Practice - Several likely outcomes exist when the environmental penalty factor is applied:
Example 1: (Illustrated in Figure 3) Apply the environmental penalty factor to all of the appropriate stress range pairs (for all of the transients) comprising the original overall component design CUF and find that the cumulative usage factor with the penalty (Environmental Penalty CUF) is less than or equal to 1.0. Make no adjustments to the original analysis allowable cycle limit being tracked against (example shown in Figure 2) and continue to track the accumulation of these cycles through the Oconee Thermal Fatigue Management Program.
Example 2: (Illustrated in Figure 4) Apply the environmental penalty factor to all of the appropriate stress range pairs of the original overall component design CUF and find that the Environmental Penalty CUF is greater than 1.0. This case has several steps in order to resolve.
- 1. The first step is to determine the modified number of cycles needed to keep the Environmental Penalty CUF equal to 1.0. This can be done mathematically by using the linear relationships between the cumulative usage factor and the number of cycles. Here, a new piecewise, diagonal line, labeled [1] in Figure 4, defines the intersection of the original design cycles and the Environmental Penalty CUF portion attributable to this transient. Then associated lines are drawn at CUF =
1.0 and a new modified analysis allowable cycle limit (labeled [2] in Figure 4) is established. This modified analysis allowable cycle limit can now be used for comparison to actual accumulated and project cycles. As stated previously, the most limiting adjusted allowable for each transient will be determined by examining the sensitivity of this exercise on all of the individual components affected by that transient. This may be an iterative procedure involving spreading the cycle adjustments among several transients to keep all component CUFs less than or equal to 1.0.
GSI-190 draft 8-13-99 R 8-25-99GS1 190 draft 8 3 99 R 2 25 99.doe 0
- 2. The next step is review current actual accumulated thermal cycles previously recorded by the Thermal Fatigue Management Program and to project them at a conservative rate through 60 years of operation. The conservative rate is illustrated in Figure 2 by the increased slope of the cycle accumulation in the future.
- 3. The third step is to check the modified analysis allowable cycle limit against the projected cycle count. If the conservatively projected 60 year cycles are less than modified analysis allowable cycle limit, then the Thermal Fatigue Management Program simply needs to be adjusted to track against the modified analysis allowable cycle limit for the years 40 through 60. If the conservatively projected 60 year cycles are greater than the modified analysis allowable cycle limit, then a fourth step is needed.
- 4. The fourth step occurs only when the 60 year projected cycles are greater than the modified analysis allowable cycle limit. In this step, the Thermal Fatigue Management Program is adjusted to manage the reduced number of design cycles for the years 40 through 60. The program manager uses the amount of margin shown by the projections to gain a sense of urgency on when corrective actions are required to assure a valid design envelope remains for plant operation.
Corrective actions, as currently established within the Thermal Fatigue Management Program are taken if the number of events is expected to exceed the limits of design within a manageable time period. A manageable time period is the time needed to complete actions to ensure the affected components stay within acceptable limits.
Step 4 Note: - The number of cycles projected at step 2 may exceed the modified analysis allowable cycle limit for an Environmental Penalty CUF prior to 40 years of operation. This is simply a recognized discontinuity in the logic of applying the environmental penalty factor only to the 40 to 60 year operating period. This does not mean that the initial 40 year design envelope is somehow substandard.
Conclusion - Modifying the Oconee Thermal Fatigue Management Program to account for environmental effects on fatigue life is a feasible option to resolve GSI-190 for Oconee. Modifying the allowable design cycles managed within the program provides a specific means to account for environmental effects and to maintain plant operation within analyzed limits.
GSI-190 draft 8-13-99 R 8-25-99 drf 8 3 99 R a 2 99.dc CUMULATIVE USAGE FIGURE 1 FACTOR Illustrative Transient (CUF) 1.0 Overall Component Design CUF incremental usage due to this transient CUF "Base" w/o this transient DESIGN CYCLES FOR 0
nSPECIFIC cycles cycles TRANSIENF Figure 2 Illustrative Transient Cycles Projected for 60 Years 400 Onna And ysis Abmae Cyde Lsnit 3.50 Modifed Ansiym At*V4e Cyde Lrnit 250 6 200-E 150 -
100 50I GSI-190 draft 8-13-99 R 8-25-99991 490 2 12 99 R 2 -5 00.
CUMULATIVE USAGE FACTOR (CUF)
FIGURE 3 1.0 Modified Transient Environmental Not Requiring Cycle Penalty Count Adjustment CUF Overall Component Design CUF
[b CUF "Base" w/o this transient 0
n DESIGN CYCLES FOR cycles cycles SPECIFIC TRANSIENT CUMULATIVE USAGE FACTOR (CUF)
FIGURE 4 Modified Transient Environmental Requiring Cycle Count Penalt Adjustment CUF 1.0 -------------
Overall Component Design CUF CUF
[2)
"Base" w/o this transient 0
mn DESIGN CYCLES FOR cycles ycles SPECIFIC TRANSIENT GSI-190 draft 8-13-99 R 8-25-99gl 19 d" 9 13 99 R 8 25 99 Distribution: Hard copv PUBLIC EHylton Docket File RLSB RF N. Dudley, ACRS - T2E26 R. Zimmerman W. Kane D. Matthews S. Newberry C. Grimes C. Carpenter B. Zalcman J. Strosnider R. Wessman E. Imbro W. Bateman J. Calvo T. Hiltz G. Holahan T. Collins C. Gratton B. Boger R. Correia R. Latta J. Moore J. Rutberg R. Weisman M. Mayfield S. Bahadur N. Chokshi J. Vora A. Murphy D. Martin W. McDowell S. Droggitis M. Modes RLSB Staff R. Emch D. LaBarge L. Plisco C. Ogle R. Trojanowski M. Scott C. Julian J. Peralta J. Wilson C. Sochor D. Walters, NEI