ML20090A818
| ML20090A818 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 02/25/1992 |
| From: | Creel G BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9203030109 | |
| Download: ML20090A818 (5) | |
Text
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s 13 ALTIMORC GAS AND ELECTHIC 1650 CALVERT CLIF FS PARKWAY
- LUSBY, MARYLAND 20057 4702 Gronot C Cntit vira Pas siotut Nuct t An teethov
- 4. a e.>...
February 25,1992 U. S. Nuclear Regulatory Commission l
Washington, DC 20$55 NITENTION:
Document Control Desk SUlijEC):
Calvert Cliffs Nuclear Power Plant Unit No.1: Docket No. 50 317 Request for Temporary Relief from ASME Iloiler & Pressure Vessel Code Section XI Requiremsnt IAE950 Gentlemen:
Baltimore Gas and Electric Company requests temporary relief from ASME Iloiler & Pressure Vessel Code Section XI (1983 Edition) requirement LAW 5250, as allowed by 10 CFR 50.55a(a)(3).
We specifically request permission to delay the repair of the weld between the discharge piping from t'.c No.11 saltwater pump and the half coupling for a pressure tap until its currently scheduled sepair during the next Unit i refueling outage (spring 1992) and to accept the as-is condition of the piping for use in the event that performance of either of the other saltwater pumps (Nos.12 or 13)is degraded. Compliance with the requirement for repair prior to use would result in haidship without a compensatory quality or safety improvement.
1.
Component for WhlehJiLkf b Hoquested i
Temporary relief is requested for the weld between the discharge piping for the No.11 saltwater pump and the half coupling for a pressure tap. A smallleak has been discovered in the area of the weld, The saltwater system provides the cooling medium for the component cooling and service water heat exchangers, and ECCS pump room air coolers. The component cooling and service water systems are designed to remove heat frorn various auxiliary systems. The ECCS pump room air coolers provide additional cooling to the ECCS pump rooms during ECCS pump operation. The saltwater piping in this area is a Class 3 component under the requirements of Section XI and Regulatory Guide 1.26.
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Document Control Desk Febmary 25,1992 t
Page 2 t
I 11.
Code itequirtments for Which litlict is lleguested ash 1E Iloiler & Pressure Vessel Code Section XI (1983 edition), requirement IAW.5250, f
states:
- (a) The source of leakages detected during the conduct of a system pressure test j
shall be located and evaluated by 'he Owner for corrective measures as follows:
... (2) repairs or icplacer..ents of components shall be performed in accordance with I AW-4(XK) or IAW.7(XXI, respectively.'
111.
Proonsed Allanathe n
t No.11 saltwater pump is currently isolated. It our is intention to leave it isolated until Unit l's spring outage unless the capability of No.12 or 13 saltwater pump degrades. In the event that either No.12 or 13 pump unexpectedly degrades, we intend to unisolate No.11 pump in order to maintain a fully capable second train of saltwater cooling. We intend to retain No.11 pump in this standby configuration, available to be restored on short notice.
This standby capabilit); provides a safety benefit which would be unavailable for the duration of No.11 pump's repmr ifit were repaired now. Considering the duration and extent of such a repair and the low likelihood of No.11 pump's required use during the short period until the outage, we consider deferring 'he repair to be the appropriate course of action from a safety perspective.
When the No.11 saltwater pump is declared operable and is in service we propose to 3erform periodic visual examinations to ensure that the leakage from the half-coupling weld las not significantly increased. This provides appropriate safety assurance until Unit l's next scheduled refueling outage (spring 1W2), at w hich time a code repair will be made, IV.
Supportine informalbn A.
Spjuuence of Evenu During a pre-outage system walkdown on February 10,1W2, evidence of seepage from the Unit 1 No.11 saltwater pump discha i was found This evidence consisted of a brown stain and wetness in the area of the weld for a pressure top half coupling.
No active leakage (drops er strearn of water) was observed. The area continued to be observed periodicelly for the next several days On February 12,1992, an ultrasonic exarnination of the weld area was performed. The piping in the area of the weld was found to exceed the required minimum wall thickness. The following day, our metallurgical specialists examined the veld visually and determined that a leak did,in fact, exist. An Issue Report was written, and on February 14,1992, No.11 saltwater pump was isolated. Technical Specification Action Statement 3.4.10, ' Structural Integrity of ash 1E Code Class 1,2 and 3 Components," was entered.
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i Document Control Desk Feb,rgary 25, IW2 Page 3 i
An initial o perability assessment for the No.11 saltwater pump discharge piping was performed ay evaluating the leakage from the saltwater system if the half-coupling should shear off. 'the evaluation showed that there is adequate margin in the l
l capacity of the saltwater r,ystem so that the postulated leak would not affect the ability of the saltwater sptem to perform its safety function.
Ilased on this evaluation, an initial determination was made that the No.11 saltwater pump was able to perform its safety function.1herefore, the system is determined to be operable. Ilowever, because of the identified leakage in the weld, we remained in the Technical Specification Action Statement 3.4.10,
- Structural Integrity of ASME j
Code Class 1, 2 and 3 Components.". 1his Action Statement does not restrict
~
continued power operation: however, it does require that the affected component have its structuralintegrity restored or be isolated. The pump is currently Isalated. If we need to unisolate the pump and operate it, daily visual examinations will be performed instead of restoring the discharge pipe weld to full structuralintegrity, II.
Anahsis ne piping around the leaking weld was examined ultrasonically, he pipe wall thickness at each examination location was found to be significantly gre ier t.ian the minimum allowable wall thickness. No stress analyses were performeo because we have no means to accurately quantify the site of the leakage path. Subsequent t
analyses were performed assuming a complete faJ te of the weld, C.
Mety Significance The operability of the saltwater system ensmes that suf0cient cooling capacity is available for v.>ntinued operation of equipment during normal and accident conditions. To ensure that the system's function was addressed, a total failure of the half coupling weld was assumed and the subsequent leakage was calculated. At the design pressure for the system, the maximum leakage from Ac failed half-coupling was evaluated to be approximately 250 ppm. Currently, a 7 0 rpm capacity margin exists for the No.11 saltwater pump. Assuming the maximeu leakage, the margin i
would be reduced to approximately 740 gpm. 'lherefore, adequate capacity still exists for the No.11 saltwater system to perform its safety function. Additionally, the intake structure has been analyzed for a flooding rate of 447 gpm. Ilecause the postulated flooding rate from the failed half-coupling is less than the allowed Dooding rate, the f ailure of the half-coupling has no safety impact on the intake structure.
Additionally, due to the location of the failed half coupling. it was determined that spray from this leak would not affect any Motor Control Centers or vital components.
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Feb.ripiry 25,1W2 Page 4 DAe Requirement l'nformance Ingar.1
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'lle repair of the weld on the saltwater pipe requires that the affected section of pipe be drained and opened. To drain the pipe and gain access to the weld requires that 4
the expansion joint at the saltwater pump discharge be removed. Additionally, at least one of the sluice gates on the intake structure must be closed and the intake r
cavity rnust be drained. This requires a power reduction on Unit 1 Meause of the loss of at least one circulating water pump during the repair. We. stimate that the replacement of the half coupling could be accomplished within seven days, l
During modes 1 through 4. twu independent saltwater hiops must be operable, Number 11 saltwater pump could be fully isolated and drained to repair the saltwater pipe and replace the half coupling while Unit 1 is operating at reduced power as long as the other two saltwater pumps remain operahle. If one of the other saltwater 1
pumps become3 inoperable while we were repairing No.11 saltwater pump discharge piping. Unit 1 could be forced into an unscheduled shutdown.
This section of pipe is scheduled to be examined and repaired during the next Unit 1 refueling outage. 'llat outage is scheduled to begin on March 20,1W2. To perform 7
a repair which will require a power reduction and has the potential to force Unit 1 into an unscheden:d shutdown, so close to a scheduled outage, is a hardship without a l
compensating increase in the lei :1 of quality and safety.
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l Y.
Comgunilory Actions We will perform periodic visual examinations to veify that the leakage frou the half.
coupthg weld has not significantly increased. These examinatior s will only be performed when s.se No.11 saltwater pump is declared operable and is in service.
i i
VI.
[tJjpji[!10niatl0n Sthtdule l
t i
A.
Visual examination to monitor leakage from the weld -- Daily 13.
Repair or replacement - Next scheduled Unit I refueling outage (spring IW2)
SAITlY COMN11'ITEliFVIEW The proposed relief request has been reviewed by our plant Oyerations and Safety Review Committee and they concluded that compliance with I AW 5250 wou d result in a hardship without a compensatory improvement in quality or safety.
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. Muary 25,1992 4' age 5 s
f Should you have any questions regarding this matter, we will be pleased to discuss them with you.
Very truly yours,
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MW for G. C. Creel Vice President Nuclear IIncrgy GCC/ PSF / psf / dim cc:
D. A.13 rune, Esquire J. E. Silberg, Esquire it A. Capra, NRC D. O. Mcdonald, Jr., NRC T. T. Martin, NRC P. R. Wilson, NRC lt 1. McLean, DNR J. It Walter, P. C z~.
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