ML20082K956
| ML20082K956 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 08/27/1991 |
| From: | Creel G BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| Shared Package | |
| ML20082K959 | List: |
| References | |
| GL-91-04, GL-91-4, NUDOCS 9109030131 | |
| Download: ML20082K956 (6) | |
Text
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l' 13 ALTIMORE l
GAS AND ELECTRIC CHARLES CENTER e P.O. DOX 1475
- DALTIMORE, MARYLAND 21203 1475 i
Gtomot C Cntti YtCt PatsittNt Nvet t am (.6,t mue 13 00 a s o e e t> s August 27,1991 U. S. Nuclear Regulatory Commission Washington,DC 20555 A'lTENTION:
Document Control Desk t
SUI 13ECT:
Calvert Cliffs Nuclear Power Plant Unit Nos.1 & 2: Docket Nos. 50 317 & 50 318
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llenuest for Amendment: Snubber Fultetional Testinc Inten ak
REFERENCE:
(a)
Generic Letter 91 04, " Changes in Technical Specification Surveillance intervals to Accommodate a 24 Month Fuel Cycle,"
i dated April 2,1991 l
Gentlemen:
The 11altimore Gas and Electric Company hereby requests an Amendment to its Operating License Nos. DPR 53 and DPR49 for Calvert Cliffs Unit Nos.1 & 2, respectively, with the submittal of the proposed changes to the Technical Specifications.
r DESCRIPTION The proposed amendment would revise the Technical Specifications for both Units 1 and 2 to increase the specined snubber functional testing and service life monitoring surveillance intenals to.
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accommodate the 24 month fuel cycles currently in use at Calvert Cliffs. This requested change is based on a history of low snubber failure rates and an effective snubber maintenance program. As requested in Generic Letter (GL) 91-04, an evaluation in support of the change concludes that the cffect on safety is small and does not invalidate any assumption in the plant licensing basis.
l Additionally, an update is requested to the HASES for Specification 4.0.2 to renect the wording proposed by the recently issued GL 9104.
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liydraulic snubbers are provided as movement restraints on plant systems to provide protection of i
system structural integrity during and following an event involving dynamic loading of that system, yet allow for thermal movement during normal plant temperature nuctuations.
The Technical S,ccifications impose suncillance requirements for visual inspection, functional testing, and service life monitoring of these safety related snubbers. To verify that a snubber can operate within speci0c 9109030131 910827 i
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Document Control Desk August 27,1991 Page 2 performance limits, functional testing is periodically performed that invoh'es remosing the snubber from its installation and performing bench testin: to verify that the activation acceleration and the bleed rate are within their s,eciDed ranges.
Junctional testing is intended to provide a high confidence level that the snu >bers would operate within these specined acceptance limbs. The performance of visual examinations is a separate process that complements the functional testing program and provides additional con 0dence of snubber operability (1 rough periodic examination to verify that the general mechanical and structural condition of the support is acceptable, in addition, senice life monitoring is conducted to assure that the snubber's indicated service life will not be exceeded prior to its next review. This monitoring consists of a documentation review of the expected service life and the testing and maintenance records, and an evaluation of capabilities until the next scheduled functional testing.
Iti?OUl?NTl?!) CII ANGl?
Change pages 3/4 7 26 and 3/4 7 26b, and Bases, ages B3/4 0 3 and B3/4 7 5 of the Unit I and Unit 2 Technical Specifications as shown on the markeoup pages attached to this transmittal.
The frequency for conducting Surveillance llequirement 4.7.8.1.c would be tevised from a once per every 18 months to require functional testing on a once per itefueling Interval (24 months) to accommodate the current 24-month fuel cycle m use at Calvert Cliffs. The term during shutdown" would also be deleted to avoid confusion with the operating conditions defined as llot Shutdown and Cold Shutdown.
The frequency for conducting Surveillance Requirement 4.7.8.1.e would be similarly revised from a once per every 18 months to require service life monitoring on a once per Refueling Interval (24 months) to accommodate the current 24 month fuel cycle.
Changes to the Bases are included to reflect these requested revisions to the Specifications as identified in the guidance provided by GL 91-04. Also, the Bases for Specification 4.0.2 are requested to be updated to reflect the proposed wording of GL 91-04.
sal'l IY ANAINSl:SiltISTil'ICATION The current Calvert Cliffs Technical Specifications specify a schedule for snubber functional testing and service life monitoring that is based on an 18-month fuel cycle, llowever, Calvert Cliffs has changed fuel design and is now operating on a 24-month fuel cycle. Since several Technical Specification surveillances have required frequencies of every 18 months, the operating cycles currently include a mid cycle outage to conduct the required surveillances.
Two of these surveillances are functional testing and the associated senice life monitoring of snubbers. Therefore, extended functional testing and senice life monitoring surveillance frequencies are proposed to accommodate the longer fuel cycle.
Calvert Cliffs Unit 1 contains 108 accessible snubbers and 218 snubbers which are inaccessible during power operation. Unit 2 similarly contains 109 accessible snubbers and 172 inaccessible snubbers, in accordance with the Technical Speci0 cations, BOAE periodically conducts both visual inspections I
and functional testing of specified snubbers. Functional testing provides direct indication of the capabilities of the snubber to perform its function. Visual inspections provide an additional l
mechanism for identincation of degraded snubbers which complements the functional testing l
program and provides additional confidence in snubber operability.
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Daltimore Gas and lilectric Company has reviewed historical failure data for these hydraulic snubbets at Calvert Cliffs and found them to be very reliable. Visual inspections at Calvert Cliffs have identified twu or fewer unacceptable snubbers during each impection. Of the 6,881 visual inspections conducted at Calvert Clif fs, there have been a total of only 19 failures (less than 0.28%).
Functional testing results have also been excellent. A total of 614 snubbers have undergone functional testing at Calvert Cliffs (both units combined). Of these, only seven have been identified as failures, for a functional test failure rate of approximately 1.14%.
We have also compared the failute rates for Calvert Cliffs snubbers to the failure rates for the industiy utilizing data from the Snubber Utility Group' data base. 1he industry has reported approximately 35,850 visual inspections of hydraulic snubbers since 1975, with only approximately 870 repried as failed or degraded, or less than 2.5%,
Further, the industry has reported approx mately 10.000 functional tests of hydraulic snubbers, with only approximately 1200 reported fai utes, or approximately 12.1%. Comparison of the visual inspection and functional testing failure rates of Calvert Cliffs with those of the industry indicates that the snubber maintenance program in place at Calvert Cliffr has been very effective.
The structure of the existing Technical Specifications for snubber visual inspection and functional
- testing (i.e., increased failure rates will lead to increased frequency of inspections or additional snubbeis tested) 3rovides significant incentive for a proper installation and maintenance program.
Our review of int ustry's reported failure rucchanisms for hydraulic snubbers indicates that snubber failure is typically not age related, but rather due to outside influences, such as poor installation, failure to maintain proper fluid level and purity, or an ineffective seal maintenance program. These factors have led DG&li to develop careful installation practices and an effective maintenance pregram which are evidenced by the low failure rate at Calvert Cliffs. lixtending the functional testing surveillance intenal to 24 months would not effect the continuation of these installation and maintenance practices, and would therefore not have a significant effect on the failure mechanism of hydraulic snubbers at Calvert Cliffs.
The service life monitoring program provides for a periodie snubber performance evaluation to determine which snubbers would reach the end of their expected service hfe prior to the next review.
1hese snubbers are replaced or refurbished to extend their service life, lixtending the monitoring program intervals from 18 to 24 months would essentially be an administrative change to include the i
new interval icngth into the program. The performance evaluations would then consider snubbers whose expected service life wouhl be reached during the next 24 months instead of during the next 18 months. Ilowever, with the proposed change, the first of these 24 month evaluations would bc l
performed within 18 inonths of the previous evaluation to provide a continuous monitoring program.
The Bases far Surveillance Requirement 4.0.2 are revised to be consistent with the proposed wording of GL 91-04. Surveillance Requirement 4.0.2 and its Bases were previously revised in Unit 1/ Unit 2 Amendment Nos.150!!32 prior to the issuance of GL 91-04 with slightly different woiding. The revised wurding would provide consisteney with the industry guidance and provide a statement regarding the performance of surveillances during operation if the surveillance is normally required to be performed during an outage.
An industry organization formed Io share technical intorrnation about the maintenance, inyction and testing of snubters.
Document Control Desk l
August 27,1991 Page 4 L
11121;14 M l N ATLDILQlMlHFi11CA NT I I WilllS:
'lhe proposed change has been evaluated against the standards in 10 CI R $0.92 and has been I
determined to not involve a significant hatards consideration, in that operation of the facility in accordance with the proposed amendment:
i (1)
It'ould not hoolve a significant increase in the probability or consequencn of an accident previously craluated.
'lhe snubbers at Calvert Cliffs have been highly reliable as evidenced by a cornparison of
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failure rates with the industry average. Also, the typical failure mechanism is not time
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dependent, but is due to outside influences, such as poor installation, failure to maintain 1 roper iluid level and purity, or an ineffective seal maintenance program. I urther, the small i
netease in the surveillance interval is expected to be offset by reducing the number of
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shutdowns and potential challenges to safety systems that would be required to conduct the t
functional testing on an 1& month basis. The change to the service life nonitoring interval is essentially administrative since the program assures the indicated operating life of the snubber will not be exceeded prior to the next review. 'therefore, the proposed change does not involve a signi'icant incicase in the probability of an accident previously evaluated.
Also, the change in the functional testing and scivice life monitoring frequency does not
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irnpact the response of any equipment to previously analped accidents. 'thesefore, the proposed change does not involve a sigr.ilicant increase in tfic consequences of an accident I
previously evaluated.
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(2) ll'ould not create the possibility of a new or different type of accident front any accident i
previously evaluated.
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-The revised testing interval will continue to demonstrate the ability of the equipment to
-l 1rovide dynamic load support during and following a seismic event, No new equ pment is 3eing added to the plant and no change is Seing made in the way existing equipment is being operated er m:inta ned. Therefore, the proposed increase in the snubber tunctional testing and sc.vice life monitoring intervals does not create the possibility of a new or dif ferent type j
of accident from any accident previously evaluted.
k (3)
Ii'ould not involve a significant reduction in a margin ofsafety,
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The proposed extension of the snubber functional testing and service life monitoring f
intervals continues to provide protection of the functional reliability of the systems which the snubbers support.
The testing program continues to provide incentive for proper-maintenance of the snubbers. Therefore, the proposed change does not involve a significant L
reduction in the margin of safety, f
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Document Control Desk August 27,1W1 Page 5 i
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t This change h requested to be approved and issued by October 30, lWl, to allow time for i
appropriate planning of the next outage during which functional testing is scheduled.
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!!bFl7lT COMhKilliGRQ'lM l
These p oposed chan es to the Technical Specifications and our determination of signincant huards have been reviewed y our Plant Operations and Safety lleview Committee and Oll Site Safety i
iteview Committee, and they have concluded that implementation of these changes will not result in l
an undue risk to the health and safety of the public.
Very truly yours, 6
DTATE OF MARYLAND i
TO WIT t i
COUNTY OF CALVERT i
I hereby certify that on the 27^da of h%d
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, before me, the subscriber, a Notary Public of the State of hfaryland in innd for (S /ve r (b erh/
personally appeared George C. Creel, being duly sworn, andTlates that he is Vicd Prerident of the
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i Baltimore Gas and lilectric Company, a corpo,ation of the State of Maryland; that he provides the I
foregoing information for the purposes therein set forth; that the statements made are true and t
correct to the best cf his knowledge,information, and belief; and that he was authorized to provide the information on behalf of said Corporation.
i WITNESS my lland and Notarial Scal:
$MJ /
Notary Public i
My Commission Expires:
Adhtt4ek /ff Daic i
GCC/EllO/crg/dtm Attachinents
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Document Control Desk j
August 27,1991 i
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D. A. litune, thquire
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J. IL Silberg, thquite
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- 11. A. Capra, NilC j
D. O. Mcdonald, Jr., NitC l
T. T, Martin, NitC L li Nicholson, NltC 11.1. Mclean, DNil J. I1. Walter, l'SC l
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