ML20040D098
| ML20040D098 | |
| Person / Time | |
|---|---|
| Site: | McGuire  |
| Issue date: | 01/19/1982 |
| From: | Tedesco R Office of Nuclear Reactor Regulation |
| To: | Parker W DUKE POWER CO. |
| References | |
| NUDOCS 8201300145 | |
| Download: ML20040D098 (8) | |
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j t0uncan NRC PDR Mr. William O. Parker, Jr.
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a" r al PDR Vice President - Steam Production e o Duke Power Conpany N
RVollmer NSIC cn P.O. Box 2178 422 South Church Street TMurley ACRS (16)
Charlotte, North Carolina 28242 R rt Id, MPA Technical Assistants to 0ELO Chairman & Commissioners
Dear Mr. Parker:
0IE (3)
Subject:
Revicu of Power Ascension / Inspection Program Utilizing Westinghouse Model D Steam Generator (McGuire Nuclear Station, Unit 1)
By letter dated October 30, 1981, you informed us of the action you intended to take following notification from Westinghouse of adverse steam generator experience on a Westinghouse non-domestic plant. On Noverrber 20, 1981, we mt with you and Westinghouse to obtain a detailed briefing and status of the Model D steam gener-ator vibration phenomenon.
By letter dated Novenber 30, 1981, you provided us with copies of the information presented during the Noveirber 20 meeting. Much of this inforcation was proprietary to the Westinghouse Electric Corporation.
In your recent letter of December 29, 1981, you provided us with a status report of your power ascension / inspection program. We have also conferred with you by telephone on aspects of your program.
Cased on the information provided thus far, we find that your proposed inspection program and plans for operation of McGuire Unit 1 are acceptable througn February 15, 1982. A summary of the results of our review is presented in the enclosure..ik request that you keep us informed in a timely manner, by telephone and correspond-ence, of any new information that you receive or any significant changes in either your prograu or ongoing testing at the plant as well as the results of prograns at Westinghouse and others related to this matter.
The reporting and/or recordkeeping requirements contained in this letter affect fewer than ten respondents; therefore 0:0 clearance is not required under P.L.96-511.
We appreciate your continued cooperation.
Sincerely.
Orfgtnal signed by gobert L Tedesso 8201300145 820119 Robert L. Tedesco, Assistant Director PDR ADOCK 05000 for Licensing P
Division of Licensing
Enclosures:
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Docket Nos. 50-390/391 LB #4 r/f dei senhut Docket No. 50-369 EAdensam bec: TERA KJabbour NRC/PDR Mr. Willian 0. Pdrker, Jr.
MDuncan Local /PDR Vice President - Steam Production SHanauer NSIC Duke Power Company RTedesco TIC P.O. Box 2178 P,Vollmer ACRS (10) 422 South Church Stre't TMurley Technical Assistants to e
Charlotte, North Carolina 28242 RMattson Chairman & Commissioners RHartfield, MPA
Dear Mr. Parker:
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OIE (3)
Subject:
Review of Power Ascension / Inspection Program Utilizing Westit:3 ouse Model D Stean Generator (McGuire Nuclear h
Station, Unit 1)
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By letter dated October 30, 1981, y nformed us of the action you intended to take following notification from West house of adverse steam generator experience on a Westinghouse non-donestic plant. Oh November 20, 1981, we met with you and Westinghouse to obtain a detailed briefin d status of the Model 0 stean gener-ator vibration phenonenon. By letter dat November 30, 1981, you provided us with copies of the information presented during th November 20 meeting. Huch of this information was proprietary to the Westinghous Electric Corp. In your recent letter of December 29, 1981, you provided us wi a status report of your power ascension / inspection progran. We have also conferred with you by telephone on aspects of your program.
Based on the information provided thus far, we find t at your proposed inspection program and plans for operation of McGuire Unit 1 are ceptable through February 15, 1982. A suonary of the results of our review is present in the enclosure. We request that you keep us infonted in a timely manner, by elephone and correspond-ence, as to the results of your ongoing progran as well as se of Westinghouse and efforts by others related to this matter.
The reporting and/or recordkeeping requirements contained in th letter affect fewer than ten respondents; therefore, OMB clearance is not required unhr P.L.96-511.
We appreciate your continued cooperation.
Sincerely, Robert L. Tedesco, Assistant Director for Licensing Division of Licensing
Enclosures:
As stated t ;,O 1
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b REVIEW OF McGUIRE UNIT NO. 1 POWER ESCALATION / TEST PROGRAM UTILIZING T'ESTINGHOUSE MODEL D STEAM GEHERATORS On October 30, 1981, the staff was forna11y notified by Duke Power Company of the potential for stean generator tube degradation at the McGuire Nuclear Station.
The potential degradation has recently been detected in the econonizer sections of non-donestic Westinghouse Model D-3 steam generators (Ringhals 3 and Almaraz 1) which are similar to Model D-2 stean generators at McGuire. The degradation was and is currently confined to the outer three rows of tubes where the feedwater enters the tube bundle and is attributed to flow induced vibration of the tubes and subsequent wear at the support plate intersections. This vibration induced wear phenomenon caused a 2.6 gpn prinary to secondary leak at Ringhals 3 neces-sitating a plant shutdown on October 21, 1981.
As a consequence of this information, a power escalation / test program was established for the McGuire Station, which included shutdowns and steam generator eddy current testing (ECT) after various power plateaus. By letter, on December 29, 1981, and telecons, January 7 and January 15, 1982, the Duke Power Company updated the status of power escalation and testing as sumnarized below:
Af ter approxicately two weeks at 50% power, eddy current test (ECT) inspection of the "A" steam generator showed no indications of degradation.
Subsequent to the inspection outage, power was escalated to 75% for approximately four days. Again, the ECT showed no indications of degradation.
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. During this shutdown a minimum of three noise transducers were installed on each steam generator near the feedwater inlet nozzle to detect gross tube vibration if it occurs. Additionally, two high -
frequency transducers were installed on one stean generator to pro-vide a detectable noise band for 0 khz to 1 nega bz.
On startup the tranducers were stabilized and baseline readings f
taken at hot standby.
McGuire has since operated for approximately 3 to 5 days at 90%
3 power, and one day at 100% power. !!o significant increase above baseline readings was observed with the high frequency external transducers through 1005 power. Data from the other (lower frequency) noise transducers are under evaluation by Westinghouse.
Current plans are to operate at 50% power (with approximately one day at 75% power) through February 15, 1982. It is expected that operation at 50% power will reduce any potential for flow induced vibration danage as a result of the lower feedwater inlet flow vel ocities. At the completion of this phase, all four steam generators will be eddy current inspected.
The Alnaraz plant (a non-domestic unit of sinilar design which has shown flow induced vibration degradation) is currently conducting testing with both external and
. internal transducers to detemine if onset of flow induced vibration can be detected.
The external instrunentation at Alnaraz does not include the high frequency type transducers which have been installed at McGuire. If the internal transducers are proven effective, two of them will be installed at licGuire during the next shutdown.
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. Westinghouse is currently evaluating the Alnaraz data, but does not expect to have any final conclusions regarding the capabilities of the instrumentation to detect vibration until approximately mid-February. However, Duke Power will be meeting with Westinghouse on or around January 22, 1982, to discuss any prelinary findings In addition, Duke Power has established direct connunications with the Almaraz plant and will factor any infomation gained into the McGuire test progran. Duke Power Company will keep the staff inforned of developrtents at Alnaraz.
As a precautionary neasure by Duke Power, FtGuire will be shutdown in the event of any detectable primary to secondary leakage. Detectable leakage is estinated to be approxicately.05 gpn (gallons per ninute) compared to the allowable leakage of.35 gpn as specified in the Plant Technical Specifications. Additionally, because the possibility exists for prinary to secondary leakage if undetected flow induced vibration occurs, each operator will re-review the appropriate shutdown procedures to be used in the event of a primary to secondary leak.
Discussion The following Table compares the operating times which have been acctmulated at various power levels at McGuire with those which have accumulated at Ringhals 3 and Almaraz 1.
Accumulated Operatino Tine at Various Power Levels No. Days (approximately) at Power Levels I
As of
> 50%
> 7 5%
> 90%
> 95%
e McGuire November 1981 13 4
0 0
Proposed 60 18 3 to 5 1
Ringhals April 1981 62 40 19 19 October 1981 150 90 68 57 Alnaraz November 1981 80 65 61 21 omcc>
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This table shows that the operating time accumulated to date at ItcGuire, for I
power levels ranging to 75%, are small compared.to those which have been accumu-lated at Ringhals and Almaraz. Although no wear indications have yet been observed i
at McGuire, there are insufficient data at this tine to indicate that McGuire is significantly less prone to the vibration damage which has been observed at the lead !!odel D units (Ringhals 'and Almaraz). Operating time accumulated at > 50%
and > 75% power levels, respectively, at ficGuire is less than 10% to 20% of the -
corresponding operating time accumulated at each cf the non-domestic units. Con-sidering that the first leak (i.e., first 100% through wall defect) developed at J
Ringhals only after operating in excess of ten times the operating time at power accumulated to date at ticGuire, it is possible that any vibration damage at ticGuire 1
i has had insufficient time to be detectable with ECT. It must also be considered that the non-donestic units have operated for several weeks at power levels near 100%.
In assessing the potential for vibration danage at !!cGuire, it should be con-sidered that initial analyses and tests perfonned by Westinghouse indicate the potential for local flow velocities in excess of the critical velocity. Although the feedwater inlet flow at ficGuire is 7% less than that at the lead units and, in 4
addition, some hardware differences exist between the !!odel D-2 steam generators at ticGuire and the Model D-3 stean generators at the lead units, we do not yet know whether these differences will significantly reduce the potential for vibration at IicGuire relative to the lead units. Clearly, therefore, it is prudent to proceed cautiously at ficGuire as indicated in the above test progran. This tesc proaram i
provides for approximately five days operation at 90% power followed by one day at omcc>
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. 100% power. This is less than 10% of the total time which has been accumulated at similar power levels at the lead units. Based upon the vibration damage which has been obsened at the lead units, we do not expect significant through wall penetra-tion of the ItcGuire tubing can be achieved during this short time intenal. The absence of any indication of significant vibration through 100% power, as detemined by the high frequency transducers at ttcGuire, tends to support this conclusion.
However, the capabilities of the instrumentation to detect high energy vibrations is very uncertain at this tine.
It is our conclusion that the proposed program for interin operation of ticGuire Unit 1 is acceptable. We base this conclusion upon the following:
(1) the absence of detectable vibration damage to date after limited operation at 50% and 75% power levels, (2) the planned tube reinspection following a short six week operating interval (to end not later than February 15,1982),
(3) the liraitation of operation at power levels between 90 and 100% to less than one week, which is considerable less that operating time at similar power levels already accumulated at Ringhals and Almaraz, (4) operation during four of the six operating weeks prior to performing the next eddy current inspection will be at a 50% pc er level. This is expected to further reduce the potential for significant vibration degradation as a result of reduced feedwater inlet flow velocities.
(5) no indications of significant vibration through 100% power have been observed as indicated by high frequency transducers mounted externally on the itcGuire steam generators.
(The capabilities of this instrumen-tation to detect high energy vibration is very uncertain at this tine),
(6) the program makes provision for early shutdown in the event of any detectable primary to secondary leakage, even if less than the Tech-nical Specification limits, and (7) plant shutdowb procedures in the event of steam generator tube tube failures have been re-reviewed by the plant operating personel.
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The staff is closely monitoring developments at McGuire. The staff is request-ing tinely notification from the licensee of any change in status of the McGuire stean generators, including any unusual instrumentation data which nay indicate significant vibration and any indication of prinary to secondary leakage, or any new information obtained fron Westinghouse of Almaraz which may have a bearing on possible tube degradation at McGuire. If dictated by further developments or new infornation, the staff will take appropriate action on McGuire.
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