ML20235Y515
| ML20235Y515 | |
| Person / Time | |
|---|---|
| Site: | Beaver Valley |
| Issue date: | 03/01/1989 |
| From: | Sieber J DUQUESNE LIGHT CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-011, IEB-88-11, NUDOCS 8903140259 | |
| Download: ML20235Y515 (5) | |
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,o March 1, 1989
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U.
S. Nuclear Regulatory Commission l
Attn:
Document. Control Desk l
Washington, DC 20555 l
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Reference:
Beaver Valley Power Station, Unit No. 1 I
Docket No. 50-334, License No. DPR-66 l
Alternative Schedule for Evaluation of Pressurizer J
Surge Line Thermal Stratification l
Gentlemen:
i On December 20,
- 1988, the NRC issued Bulletin No.
88-11
" Pressurizer Surge Line Thermal Stratification".
It requests all' l
addressees to establish and imp 2ement a
program to confirm.
l pressurizer surge line integrity in view of the occurrence of thermal
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stratification, and requires'them to inform the staff of the actions taken to resolve this issue, i
Pursuant to satisfying the requirements and schedules of Bulletin 88-11, Duquesne Light Company (DLC) is participating in a program for
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partial resolution of this issue through the Westinghouse Owner's j
Group (WOG).
The WOG program was approved at the October 19E8 meeting and has I
the following objectives:
l Develop a
generic Justification for Continued Operation
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=
(JCO) to assure that plant safety is not compromised while the effects of thermal stratification are being determined.
Collect and summarize relevant
- design, operational, I
+
analytical, and test data for as mar,y WOG plants as I
possible.
In
- addition, a
representative
- sampling, of approximately ten
- plants, will be selected to perform a review of plant records and conduct interviews with Operations personnel.
Evaluate data and identify and prioritize significant parameters contributing to this issue.
Categorize (group) plants based on these parameters.
Recommend additional monitoring to supplement the existing transient database required to bound all WOG plants.
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BSQvor Valloy Pownr Station, Unit No. 1 Docket No. 50-334, License No. DPR-66 Page 2 Estimate the effect of thermal stratification on fatigue
+
life as a function of key parameters.
Recommend short term and long term actions.
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.
A significant amount of surge line thermal monitoring data has been obtained in support of these plant specific analyses.
Additional surge line thermal monitoring and plant system data continues to be made available within the
- WOG, resulting in a
steadily increasing database.
A significant amount of progress has been accomplished toward meeting these objectives.
To date, the WOG has completed approximately 80% of the effort of assembling plant specific design information on all domestic Westinghouse PWRs (55 units total).
This effort will establish the range of key design parameters and permit grouping of plants based on these parameters.
Based on the information assembled to date, and the experience gained in plant specific analyses and monitoring programs, the WOG evaluation has resulted in the following observations regarding plant similarity and thermal stratification:
0 1.
Thermal stratification
(>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 (7 plants).
2.
The amount of stratification measured and its variation with time (cycling) varies.
This variation has been conservatively enveloped and applicability demonstrated for plant specific analyses.
Additional monitoring data representing a
wider range of surge line configurations may be needed in order to demonstrate the applicability of these thermal stratification transients to other Westinghouse units.
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-5 raver Valley Power Station, Unit No. 1 i
Docket No. 50-334, License No. DPR-66 Page 3 3.
Significant factors which can influence the structural i
effects of stratification are:
a.
Location and design of rigid supports and restraints b.
Pipe layout geometry and size f
c.
Type and location of piping components
~
k 4.
Although the meterial and fabrication techniques for j
Westinghouse surge lines are reasonably consistent and'of high
- quality, the design parameters listed in Item 3 vary among Westingh0use~ PWRs.
This variation in design is j
primarily a
result of plant specific routing requirements.
This variability is currently being examined in order to assess the feasibility of a bounding analysis approach.
These observations developed through the on-going WOG program, indicate that the development of thermal stratification loadings and the evaluation of fatigue, considering these loadings, is a complex process.
Therefore, in order to precisely evaluate stratification, additional time is needed.
While more time is needed to evaluate the stratification issue in
- detail, the NDE inspection history at Beaver Valley Unit 1, as well as all other domestic Westinghouse designed PWR's, has not revealed any service induced degradation in the surge line piping that has been attributed to thermal stratification.
In
- addition, 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.
- Thus, a
prudent approach for providing a detailed evaluation of the effects of surgo line stratification would be to follow the WOG program grouping evaluation recommendations and monitor as determined to be appropriate.
The WOG expects to complete a
grouping evaluation, for the purpose of recommending a
list of additional plants where thermal monitoring is
- needed, by March 1, 1989.
The time required for this additional monitoring will be dependent on plant outage schedules.
To assure that the plant safety is not compromised within the requested period of schedule extension, a JCO will be submitted to l
the staff.
The JCO which is currently being developed, will be submitted by DLC to the staff by May 3, 1989.
The JCO will utilize the.information, experience, and monitoring data obtained through the WOG
- program, and will support the alternate schedule discussed herein.
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.. $ caver Valley Power Station, Unit No.
1 Docket No. 50-334, License No. DPR-66 Page 4 DLC hereby requests an alternate schedule for Beaver Valley Unit 1
to that requested in Bulletin 88-11.
A schedule of two years, from receipt of the Bulletin, is considered sufficient time to obtain the necessary additional monitoring
- data, define thermal transients, perform all required analyses and update the stress and fatigue analyses to ensure compliance with applicable code and regulatory requirements.
This schedule, though different from that requested in action 1.b of Bulletin 88-11, is consistent with the requirement to update the stress and. fatigue analyses within two years as stated in action 1.d of the Bulletin.
As previously stated, the JCO which is currently being developed, will be submitted by DLC to the staff by May 3, 1989.
l At this
- time, DLC's request for an alternate schedule applies only to Item 1.b of NRC Bulletin 88-11.
DLC intends to comply with all other requirements of the Bulletin.
Very truly yours, D.
Sieber
)VicePresident g Nuclear Group cc:
Mr. J.
Beall, Sr. Resident Inspector Mr.
W.
T. Russell, NRC Region I Administrator Mr.
P. Tam, Sr. Project Manager I
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f' p-COMMONWEALTH'OF PENNSYLVANIA)
CCUNTY OF BEAVER.
-). ss:
)
- On this'
//t[
day of effd2/
,.1989, before me, d 47 N,
a LNotary Public.'in'and for'.said
' Commonwealth-and. County, personally appeared J.
D. Sieber, who'being.
duly.' s w o r n,.: deposed, and said.that' (1).he is'Vice. President of-
- Duquesne
- Light,
.(2) he is. duly authorized to. execute and file the.
l
. foregoing" Submittal on behalf'of said Company, and (3) the statements set forth. in the Submittal are true and correct'to the best of-his
~
knowledge, information and belief.
L. k.'
Y Notarial Seat 8heila M. Fattore, Notary Pubic
$Nppingport Baro, Beaver County My Commission Expires Oct.23,1989
, Member,Penrsylvana Associabonof Notares 1
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