ML20236B590
| ML20236B590 | |
| Person / Time | |
|---|---|
| Site: | Callaway  |
| Issue date: | 03/10/1989 |
| From: | Schnell D UNION ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| IEB-88-011, IEB-88-11, ULNRC-1936, NUDOCS 8903210180 | |
| Download: ML20236B590 (6) | |
Text
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1901 Gratiot Street;
- Post Ottice Box 149 h
St. Louis, Mascuri 63166 314 554-2650 s.
UNION March. 14 1989 8 "8/" 3'#"#
Etucruic Senior Vice President
- mee, 33 U.
S Nuclear Regulatory Commission Attn:
Document' Control Desk Mail Station Pl-137 Washington, DC 20555 Gentlemen:
ULNRC-19 36 DOCKET NO. 50-483
]
CALLAWAY PLANT l
ALTERNATIVE SCHEDULE FOR EVALUATION OF i
PRESSURIZER SURGE LINE THERMAL STRATIFICATION On December 20, 1988, the NRC issued Bulletin No. 88-11 " Pressurizer Surge Line Thermal Stratifi-cation."- Tt requects all addressees to establish and.
implement a progrant to confirm pressurizer surge line integrity in sicw of the occurrence of thermal i
stratification, and requires them to inform the staff of the actions taxen to resolve thit; issue.
Action ', tem 1-b ef the Bulletin requests that a bounding ana?.ysis be performed within one. year which demonstrates that the pressurizer surge line meets the applicable design codes, considering the phenomenon of thermal stratification.
If code compliance cannot be shown by this method, then the stress and fatigue analyses for the surge line must be updated based on callaway specific data on thermal stratification, thermal striping, and line deflections.
The updated analyses are requested by action item 1-d to be completed within two years of receipt of the Bulletin.
Pursuant to satisfying the requirements of Bulletin 88-11, Union Electric is participating in a progtam for resolution of this issue through the Westinghouse Owner's Group (WOG).
As a participant in the WOG program, Union Electric hereby requests an alternate schedule to that outlined 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 L
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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.
To assure that the plant safety is not comprised within the requested. period of' schedule extension, a Justification 4
for Continued Operation-(JCO) will be submitted to.the
]
staff.
The JCO, which is currently being devel< ed, will be submitted by Union Electric to the staff within 1 year of receipt of Bulletin 88-11.
The JCO will utilize the information,. experience, and monitoring data obtained through the WOG program,.and will support the alternate schedule discussed-herein.
The WOG program was approved at the October 1988 meeting and has the following objectives:
o Develop a' generic Justification for Continued Operation (JCO).to assure that plant safety is not compromised while the effects of thermal stratification are being determined.
o Collect and summarize relevant design, operational, analytical, and test data for as many WOG plants as 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.
i o
Evaluate data and identify and prioritize significant parameters contributing to this issue.
Categorize (group) plants based on these parameters, o
Recommend additional monitoring to supplement the existing transient database required to bound all WOG plants.
o Estimate the effect of thermal stratification on fatigue life as a function of key parameters.
o Recommend short term and long term actions.
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i 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 include definition of revised thermal transients (including _____
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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 dom;stic 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:
1.
Thermal stratification (>100 F) has been measured on all surge lines for which monitoring has been performed (7 plants to date).
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.
3.
Significant factors which can influence the structural effects of stratification are:
a.
Location and design of rigid supports and restraints b.
Pipe layout geometry and size c.
Type and location of piping components 4.
Although the material and fabrication techniques for Westinghouse surge lines are reasonably consistent and of high quality, the design parameters listed in item 3 vary among Westinghouse PWRs.
This variation in design is primarily a result of plant specific routing l
requirements.
This variability is currently being examined in order to assess the feasibility of bounding analysis approach.
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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.
A prudent approach for providing a detailed evaluation of the effects of surge line stratification would be to follow the WOG program grouping evaluation reconinendations.
The WOG has completed a grouping evaluation for the purpose of recommending a list of additional plants where thermal monitoring is needed.
The time required for this additional monitoring will be dependent on plant outage schedules.
At this time, Union Electric's request for an alternate schedule applies only to item 1.b of NRC Bulletin 88-11.
Union Electric intends to comply with all other requirements of the
- Bulletin, j
Very truly yours
/
(97 Donald F.
Schnell AAK/plh i
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l STATE OF MISSOURI ).
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S.S f
CITY OF ST. LOUIS )
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Donald F.
Schnell, of lawful age, being first duly sworn upon oath says-that he is Senior Vice President-Nuclear'and an
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officer of Union Electric Company; that he has read the foregoing document and knows the content thereof; that he has executed the same for and on behalf of said company with full power and authority to.do so; and that the facts'therein stated are true and correct to the best of his. knowledge, information and belief.
P By j
Donald F.~ Schnell Senior Vice President Nuclear SUBSCRIBED and sworn to before me this /8M day of /
,1989, i
fjy BARBARA,J. PFAFF NOTARY PUBLIC, STATE OF MISSOURI MY COMMISSION EXPIRES APRIL 22. 1989 ST LOUIS COUNTY i
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cc:
Gerald Charnoff, Esq.
Shaw, Pittman, Potts & Trowbridge 2300 N.
- Street, N.W..
Washington,'D.C.
20037' Dr. J. O. Cermak CFA, Inc.
'4 Professional Drive (Suite 110)
Gaithersburg, MD' 20879 R. C. Knop Chief, Reactor Project Branch l1 U.S.. Nuclear Regulatory Commission-
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Region III 799 Roosevelt Road Glen'Ellyn, Illinois 60137
~
Bruce Little Callaway Resident Office U.S.
Nuclear Regulatory Commission RRil Steedman, Missouri 65077 Tbm Alexion (2)'
Office of Nuclear Reactor Regulation-U.S.' Nuclear Regulatory Commission Mail Stop 316 7920 Norfolk Avenue Bethesda, MD 20014-Manager, Electric Department i
I Missouri Public Service Commission P.O. Box 360 Jefferson City, MO 65102 U.S.
Nuclear Regulatory Commission l
ATTN:
Document Control Desk L
Washington, D.C.
20555 1
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