ML18009A328
| ML18009A328 | |
| Person / Time | |
|---|---|
| Site: | Harris  |
| Issue date: | 12/29/1989 |
| From: | Cutter A CAROLINA POWER & LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-011, NLS-89-160, NUDOCS 9001100209 | |
| Download: ML18009A328 (8) | |
Text
ACCELERATED UTION DEMONSIATION SYSTEM REGULATORY. INFORMATION DISTRIBUTION SYSTEM (RIDS)
ACCESSION NBR:9001100209 DOC.DATE: 89/12/29 NOTARIZED: YES FACIL:50-400 Shearon Harris Nuclear Power Plant, Unit 1, Carolina AUTH.NAME AUTHOR AFFILIATION CUTTER,A.B.
Carolina Power
& Light Co.
RECIP.NAME RECIPIENT AFFILIATION Document Control Branch (Document Control Desk)
DOCKET 05000400 R
SUBJECT:
Responds to NRC Bulletin 88-011, "Pressurizer Surge Line Thermal Stratification."
DISTRIBUTION CODE:
IE30D COPIES RECEIVED:LTR ENCL SIZE:
TITLE: Bulletin 88-11 Pressurizer Surge Line Thermal Stratification NOTES:Application for permit renewal filed.
D S
05000400
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RECIPIENT ID CODE/NAME PD2-1 LA BECKER,D INTERNAL: AEOD/DOA AEOD/ROAB NRR HOU,S NRR KUO,P NRR/DOEA/OEAB11 NRR/DREP/PEPB9D zRE FILE 2
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NOTE TO ALL"RIDS" RECIPIENTS:
PLEASE HELP US TO REDUCE WAFfEt CONTACT THE.DOCUMENI'ONTROLDESK, ROOM Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAMEFROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!
TOTAL NUMBER OF COPIES REQUIRED:
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CML Carolina Power & Light Company P.O. Box 1SSt
~ Raleigh. N.C. 27602 DEC 2 9 jg89 A. 8 CUTTER Vice President Nuclear Services Department United States Nuclear Regulatory Commission ATTENTION: Document Control Desk Washington, DC 20555 SERIAL:
NLS-89-160 SHEARON HARRZS NUCLEAR POWER PLANT DOCKET NO. 50-400/LICENSE NO. NPF-63 JUSTIFICATION FOR CONTINUED OPERATION REGARDING PRESSURIZER SURGE LINE THERMAL STRATIFICATION Gentlemen:
On December'0,
- 1988, the NRC issued Bulletin 88-11 "Pressurizer Surge Line Thermal Stratification".
The Bulletin requests all addressees to establish and implement a program to confirm pressurizer surge line integrity for the design life of the plant in view of the occurrence of thermal stratification.
Licensees were also directed to inform the staff of the actions being taken to implement the Bulletin's requirements.
This letter provides the status of actions taken by Carolina Power
& Light Company (CP&L) for the Shearon Harris Nuclear Power Plant (SHNPP).
Item la of the Bulletin's Requested actions directed Licensees to
,conduct a visual inspection of the pressurizer surge line at the first available shutdown which exceeded seven days in length.
Inspection of the SHNPP surge line was completed during the recent refueling outage.
No discernable distress or structural-damage was identified.
Item 1b of the Bulletin required Licensees to demonstrate that the pressurizer surge line meets the applicable design codes and other FSAR and regulatory commitments for the licensed life of the plant, considering the phenomenon of thermal stratification and thermal striping in the fatigue and stress evaluations.
This analysis was to be completed within one year of reciept of the Bulletin for plants in operation less than 10 years, i.e.,
December 29, 1989 Carolina Power
& Light Company is participating in a program for partial resolution of this issue through the Westinghouse Owners'roup (WOG).
Pursuant to action 1.b of Bulletin 88-11, a bounding evaluation has been performed'or Westinghouse plants.
Since this evaluation provides less than full design life verification, a generic Justification For Continued Operation (JCO) has been developed for use by each of the WOG plants.
The technical basis for the JCO is the bounding evaluation which utilizes comparisons of the individual surge line design and plant operational data with those of plants for which analysis and/or monitoring has been performed.
,The bounding evaluation, 900110C1209 891229 PDR ADOCi' 000400 lg PDC.
Document Control Desk NLS-89-160 / Page 2
WCAP-12277/12278, was submitted to the staff on June 15, 1989 by the WOG1.
The enclosure to this letter provides the Justification for Continued Operation applicable to SHNPP regarding pressurizer surge line thermal stratification.
Since the analysis performed pursuant to 1b does not show conformance.
for the duration of the operating license, Items lc and 1d of the Bulletin require CP&L to obtain representative or plant specific surge line data and update the stress and fatigue analyses to ensure.
compliance with code requirements.
This'action is required to be
-. completed by December 29, 1990.
The Westinghouse Owners'roup is preparing a more detailed technical report,, into which plant specific information will be integrated, to show full design life verification.
This detailed technical report, to be submitted within the schedule specified for Bulletin Items 1c and 1d, is expected to resolve the surge line stratification issue for SHNPP.
Please refer any questions regarding this submittal to Mr. Steven Chaplin at (919) 546-6623.
Yours very tr A. B. Cutter ABC/SDC cc:
Mr. R. A. Becker Mr. S.
D. Ebneter Mr. J.
E. Tedrow A.
B Cutter, having been first duly sworn, did depose and say that the information contained herein is true and correct to the best of his information, knowledge and belief; and the sources of his information are officers, employees, contractors, and agents of Cgrc6PIVl~ower Light Company.
FRISE My commission expires:
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Noggin (Seal f-4
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WCAP-12277/12278 Westinghouse Owners'roup Bounding Evaluation For Pressurizer Surge Line Thermal Stratification, June 1989
JIJSTIFICATION FOR CONTINUED OPERATION REGARDING PRESSVRIZER SURGE LINE STRATIFICATION SHEARON HARRIS NUCLEAR POWER PLANT BACKGROUND It was first reported in INPO SER 25-87 that temperature measurements at a
German PWR indicated thermal transients different than design.
Recent measurements at several domestic PWRs have indicated that the temperature difference between the pressurizer and the hot leg results in stratified flow in the surge line, with the top of the flow stream being hot (pressurizer temperature) and the bottom being colder (hot ling temperature).
The top-to-bottom temperature difference can reach 250 F to 300 F in certain modes of operation, particularly during heatup and cooldown.
Surge line stratification causes two effects:
o Global bending of the pipe is different than that predicted.in the original design.
o Fatigue life of the piping could be reduced due to the global and local stresses from stratification and striping.
More recently, the NRC has issued Bulletin 88-11 "Pressurizer Surge Line Thermal Stratification," December 20, 1988, identifying actions to be taken by licensees.
a)
Conduct visual inspection walkdown b)
Update stress and fatigue analysis to account for stratification and striping c)
Obtain monitoring data, as necessary The bulletin encourages licensees to perform actions b) and c) above through collective efforts with other plants.
In October 1988, Carolina Power
& Light Company (CP&L) and other members of the Westinghouse Owners 'Group (WOG) authorized a program to perform a generic evaluation of surge line stratification in Westinghouse PWRs that will address portions of Bulletin 88-11.
The WOG program is designed to benefit from the experience gained in the performance of several plant specific analyses on Westinghouse PWR surge lines.
These detailed analyses included definition of revised thermal transients (including stratification) and evaluations of pipe stress, fatigue usage factor, thermal striping, fatigue crack growth, leak before-break, and support loads.
The overall analytical approach used in all of these analyses has been consistent and has been reviewed, in detail, by the NRC staff.
As of March 1989, plant-specific analyses have been performed on five domestic Westinghouse PWRs.
In addition, twelve Westinghouse plants have completed or (344CRS)
are currently performing an interim evaluation of surge line stratification which, includes finite element structural analysis of their specific configuration under stratified loading conditions.
WOG Pro ram Status
'I Surge line physical and operating data has been collected and sumnarized for 55 domestic Westinghouse PWRs.
Information relating to piping layout, supports and restraints, components, size, material, operating history, etc.,
has been obtained.
This data has been evaluated in conjunction with available monitoring data and plant-specific analyses performed by Westinghouse.
The results of this evaluation were presented to the NRC in a meeting on April ll, 1989.
The evaluation is, formalized in a Westinghouse topical report (WCAP-12277, Proprietary and WCAP-12278, Non"proprietary version) submitted to the NRC on June 15, 1989.
This topical report forms the basis for the following justification for continued operation.
JUSTIFICATION FOR CONTINUED OPERATION A.
Stratification Severit Thermal stratification (AT ) 100 F) has been measured on all surge lines for which monitoring has been performed and which have been reviewed by the WOG to date (eight surge lines).
The amount of stratification measured and its variation with time (cycling) varies.
This variation has been conservatively enveloped and applicability of these enveloping transients has been demonstrated for plant-specific analyses.
Various surge line design parameters were tabulated for each plant ~
From this, four parameters judged to be relatively significant were identified.
A.
B.
C.
D.
Pipe inside diameter Piping slope (average)
Entrance angle of hot leg nozzle Presence of mid-line vertical riser These parameters were used in a grouping evaluation which resulted in the definition of 10 monitoring groups corresponding to various combinations of these parameters at Westinghouse PWRs.
Approximately 40X of the plants fall into one group for which a large amount of monitoring data has already been received and for which the enveloping thermal transients, discussed
- above, are applicable.
The remaining 60X of Westinghouse PWRs are divided among the other nine additional groups.
Although monitoring data has not yet been received representative of all these groups, in general, the combination of significant parameters of these nine groups is expected to decrease the severity of stratification below that of the enveloping transients.
This conclusion is also supported by a comparison of available monitoring data.
(344CRS)
B.
Structural Effects Significant parameters which can influence the structural effects of stratification are:
4 a.
Location and design of rigid supports and pipe whip restraints
. b.
Pipe layout geometry and size c.
Type and location of piping components Although the material and fabrication techniques for Westinghouse surge lines are reasonably consistent and of high quality, the design parameters listed above varyamong Westinghouse PWRs
~
This variation in design is primarily a result of plant-specific routing requirements.
A preliminary evaluation, comparing the ranges of these parameters to those of plants for which plant-specific analysis and interim evaluations are available (approximately 20X of Westinghouse PWRs),
has been performed.
This comparison indicates a high degree of confidence that, from a combined transient severity and structural effects standpoint, the worst configuration has most likely been evaluated.
This con'elusion is supported, by plant-specific analyses covering five plants and interim evaluations of six additional plants.
These analyses and evaluations have included various piping layouts, pipe sizes, support and restraint designs and piping components.
Although the full range of variation in these parameters has not been evaluated, experience gained from these evaluations indicates that further evaluations will not result in a more limiting configuration than those already evaluated.
C.
0 eratin Procedures The WOG currently has available the surveys of operating procedures performed in support of existing plant"specific analyses.
Experience indicates that heatup and cooldown procedures have a significant effect on stratification in the surge line.
All conclusions reached by the WOG to date have assumed a
steam bubble mode heatup and cooldown procedure which may result in a temperature difference between the pressurizer and reactor coolant system (RCS) hot leg of more than 300 F.
In many cases, individual plant operating procedures and technical specifications provide limits on this value.
It is also known that some procedures utilize nitrogen, during at least part of the heatup/cooldown
- cycle, as a means of providing a pressure absorbing space in the pressurizer.
Based on information currently available to the
- WOG, a high confidence exists that the steam bubble mode heatup, assumed to date, is conservative with respect to Westinghouse PWRs
~
D.
Pi e Stress and Remainin Life The design codes for surge line piping have requirements for checking pipe stress limits and the effects of fatigue loadings.
These stress limits provide a means of controlling stress from primary loads such as pressure, deadweight, and design mechanical
- loading, as well as stress from secondary loads such as thermal and anchor motion effects.
(344CRS)
Stratification in the surge line is a secondary load which will only affect the qualification of secondary stresses.
The qualification of primary stresses is not affected by this loading.
Secondary stresses are controlled to prevent excessive displacements and gross plasticity and to prevent excessive fatigue loadings in the pipe.
The basic characteristic of a secondary stress is that it is self limiting; thus, a
failure from a single application of a secondary loading is not expected.
For the stratification issue, the potential effects of excessive displacements have been investigated through a detailed visual observation of the SHNPP surge line during the walkdown required per Bulletin 88-11 action l.a.
No gross discernible distress or structural damage was identified in the walkdown.
The effects of secondary stresses on the remaining life of the surge line have been evaluated on a generic basis through the WOG program.
The fol'lowing suranarizes the results of this evaluation.
All plant-specific analyses performed as of March 1989 have demonstrated compliance with applicable ASME Codes and a surge line fatigue life in excess of a 40-year plant life.
Review of plant-specific fatigue calculations indicates that the surge line fatigue life is primarily dependent on the number of heatup and cooldown cycles,'ather than years of operation.
Considering the worst case years of operation (28.5 yr.) in combination with the worst case number of heatup-cooldown cycles (75, at a different plant) at any Westinghouse
- PWR, and assuming a 40-year life for all surge lines, it is estimated that no more than approximately 50X of the fatigue life has been used at any Westinghouse plant to date.
For a design life considering 200 heatup-cooldown cycles (used in plant-specific analyses),
this would indicate approximately 100 remaining cycles'his number of remaining cycles far exceeds the postulated worst case number for the two-year time frame needed to resolve the stratification issue.
E.
Leak Before Break All the plant-specific analyses performed to date that have included the loadings due to stratification and striping have validated the "leak-before-break" concept and have substantiated a 40-year plant life.
Fatigue crack growth calculations, performed as part of these plant-specific
- analyses, have demonstrated that any undiscovered crack as large as 10K of the wall thickness would not grow to cause leakage within a 40-year plant life.
Nevertheless, any postulated through wall crack propagation would most likely result in "leak-before-break" and thus permit a safe an orderly shutdown.
F.
Ins ection Histor The NDE inspection history at Shearon Harris Nuclear Power Plant (SHNPP) as well as all other domestic Westinghouse designed
- PWRs, has not revealed any service induced degradation in the surge line piping that has been attributed to thermal stratification.
(344CRS)
Surrmar of Conclusions from WOG Pro ram Based on information. assembled on surge lines for all domestic Westinghouse
- PWRs, and evaluation of that information in conjunction with plant-specific and other interim evaluation results, the WOG concluded that:
o A high degree of confidence exists that further evaluation will confirm that=the worst combination has already been evaluated for stratification severity, structural effects and operating procedures.
o
,All plant-specific analysis, to date, have demonstrated a 40-year life of the surge line.
Assuming that further evaluation leads to the same conclusion for the remaining Westinghouse
- PWRs, the worst case remaining life is approximately 100 heatup-cooldown cycles' Through wall crack propagation is unlikely, however, "leak-before-break" would permit a safe and orderly shutdown if a through wall leak should develop.
o NDE inspection history demonstrates the present day integrity of Westinghouse PWR pressuiizer surge lines.
While additional monitoring, analyses, and surveys of operating procedures are expected to further substantiate the above conclusions, the presently available information on surge line stratification indicates that Westinghouse PWRs may be safely operated while additional data is obtained.
Overall Conclusion Based on the above discussions and results of the recent inspection, CP&L
'believes it is acceptable for SHNPP to continue power operation for at least ten additional heatup-cooldown cycles.
Carolina Power
& Light Company has conmitted to address the requirements of Bulletin 88-11 by January 1991.
(344CRS)