ML20236D814
| ML20236D814 | |
| Person / Time | |
|---|---|
| Site: | Calvert Cliffs  |
| Issue date: | 03/13/1989 |
| From: | Russell L BALTIMORE GAS & ELECTRIC CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 8903230282 | |
| Download: ML20236D814 (4) | |
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i BALTIMORE G AS' AND ELECTRIC CHARLES CENTER. P.O. BOX 1475 BALTIMORE, MARYLAND 21203 LEON B. RUSSELL MANAGER CALVERT CUFF 8 NUCLEAR POWER PLANT DEPARTMENT I
March 13,1989 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION:
Document Control Desk
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SUBJECT:
Calvert Cliffs Nuclear Power Plant Unit No. 2; Docket No. 50-318 Reauest for Relief from ASME Code Section XI Requirements
REFERENCE:
(a) NRC Staff Guidance Letter on ASME _ Relief Requests dated January 1978 Gentlemen:
j in accordance with 10 CFR 50.55a(g)(6)(i), we are requesting relief from an ASME Code I
Section XI requirement that we have determined to be impractical. In accordance ivith
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Reference (a), the information concerning this relief request is represented herein, d
1 The repair or replacement-of a Steam Generator Blowdown Line elbow in accordance with j
l ASME requirements is deemed impractical. To effect repair or. replacement would 1
l require an unscheduled shutdown of Unit 2 'within two weeks of a refueling outage. We request permission 'to defer the repair or replacement of the - elbow. until the next refueling outage, presently scheduled to commence on March 25,' 1989.
Our position is that the evaluation required in IWA-5250(a) of the Code allows the owner to determine the - significance of the leakage without requiring immediate implementation of corrective measures described in IWA-5250(a)(1) or (2). Neverthe-less, we are submitting this relief request as agreed upon in our discussions with you i
on March 10, 1989. An ASME Code inquiry that addresses this issue will be submitted to ASME in the near future.
4 1.
Components for Which Relief is Reauested A two-inch pipe elbow (2" EB-6-2008) on Unit 2 Steam Generator No. 22 Blowdown.
Line is the component for which relief is requested.
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J DocEment Control Desh March 13,1989
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II.
ASME Requirement from Which Relief is Reauested Technical Specification 3.4.10.l(b) requires that ASME Class 2 components j
meet the inspection requirements of ASME Section XI (Technical Specification l
4.0.5) in the Inservice Inspection Program. Article IWC-1220(c) exempts the j
blowdown line from NDE requirements (for less than four-inch lines). Table I
IWC-2500-1, Examination Category C-H requires this blowdown line be subjected to a hydrostatic test' (IWC-5222) every 10 years and a system pressure test (IWC-5221) each period. The acceptance standard for these tests. is in Article l
IWA-5250, Corrective Measures.
l We request relief to allow deferral of immediate implementation ' of
-6 IWA-5250(a)(2), repairs or replacements of components performed in accordance with IWA-4000 or IWA-7000, based on results of our evaluation.
l Ill.
11 asis for Relief On March 7, 1989, Unit 2 was taken off line to test a feedwater regulating l
valve. A routine containment walkdown identified leakage from Steam Generator l
No. 22 Blowdown piping near the 10' Elevation steam generator chemical lay-up
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equipment. On March 8, 1989, we examined the leak to evaluate the service-ability of the system and any need for corrective action. Our review is as follows:
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i 1.
Examination of the blowdown pipe leak revealed that the leak originated l
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at a pin hole which is localized and is not likely to appreciably l
l propagate within the next two weeks. The leak is next to, and associated with, the toe of a socket weld on a two-inch schedule 80 pipe at a 90 elbow. The~ leak is next to and associated with the weld start /stop point where excess reinforcement weld material is present, along with slight undercut. This is a likely location for a welding flaw.
No linear crack-like appearance is associated with the leakage l
stream. The leak is on the side of the pipe not associated with the l
intrados or extrados of the elbow.
Attempts were unsuccessful to take thickness readings on the pipe and elbow due to high temperatures. It is our opinion that the evidence demonstrates that this leak has been primarily caused by slag or porosity from a welding flaw. The location of the pin hole is away from the geometric discontinuity of the toe of the socket weld beads. The leak is not located at the position of maximum bending stress as would be most likely for fatigue cracking. Therefore, neither crack growth nor abrupt fracture are expected with continued service. The location of the leak is not in ' a position of maximum erosion damage, therefore, i
only minor increased leakage is expected during continued service.
2.
The system is constrained from bending out of the plane of the elbow by two restraints on the vertical leg of this pipe. The pipe is motionless and not subject to any sensible vibration during operation.
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Document Coatrol Desk March 13,1989 '
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3.
This - elbow has not been. measured in the past for erosion / corrosion -
damage. The adjacent elbow on this line (21' upstream of the line) has j
a. documented-wall thickness history for erosion / corrosion loss. The i
history. indicates clearly that the maximum wall loss which. may be projected from this data is negligible and approximately 0.0002"--in a two-week period.
4.
Total containment sump accumulation is approximately two. _ gallons / hour l
based on the ' latest drainage frequency 'of once' per - 25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />.. In the l,
fall of '1986, we experienced a through-wall leak _on a similar - elbow on i
No. 21 Steam Generator Bottom Blowdown Line. We experienced a leak. rate as high' as 44 gallons / hour.
The hole size was approximately I
0.0625 inches. Subsequent examination of the elbow revealed more than.
adequate structural integrity remained to prevent catastrophic failure.
5.
Although. extremely unlikely, catastrophic failure of the. entire line is -
bounded by the FSAR Chapter 14. Feedwater Line Break Analysis.
6.
. There will be no adverse effects from the steam impingement on the concrete wall adjacent to the elbow. There. may be some minor cosmetic damage. Before any structural damage could possibly occur. in this wall, the outer two inches of the concrete would have to be removed, a most improbable consequence of this small leak.
1 7.
The Environmental Qualification Design Manual for Calvert Cliffs lists 70% as the maximum containment humidity. This is substantially higher than the normal 15-40 %
range. observed in the containment.
10 CFR 50.45(e)(5) states that consideration must be given. to all significant (emphasis added) types of degradation which _can have an effect on the functional capability of the equipment. Degradation due to normal humidity is not considered to be significant since normal
.triations in the relative humidity in the ranges identified at Calvert l
Cliffs are enveloped by the steam temperature / pressure / relative humidity testing performed for post-accident. qualification. The steam generator blowdown line pinhole leak does not impinge on any qualified equipment.
l Considering these factors, the break has no adverse effect on EQ equipment.
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l 8.
This _ line successfully passed the ' last Inservice I..spection hydrostatic test in the spring 1987. The pressure was 1250 psig. Design pressure is 1000 psig and normal operating pressure is 850 psig. Pressure at the time o' Pak detection was approximately 900 psig. A slight decrease in sump hequer.c was noted when the plant returned to normel operating pressure.
Based on' the abovs discusse. we have concluded that the leak in the blowdown line is not susceptibk to eider catastrophic failure or a major increase in leakage rate. Operation wb th.s leak until the Unit 2 spring _1989 refueling outage presene, no risk to ' the health and safety of' the public. Repairing or replacing this elbow before ' the: refueling outage would require an unscheduled shutdown and cooldown. This would result in an hardship (plant thermal cycle) without a compensating increase in the level of quality and safety.
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Document Control Desk March 13,1989 1
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IV.
Alternate Testina j
The leak will be monitored via the containment normal sump (approximately 44-gallon capacity) drainage frequency.
Either of two redundant level switches located approximately 5 inches above the bottom of the sump actuate an audio-visual alarm in the Control Room to notify the Control Room Operator of the need to drain the sump. Given the latest drainage frequency of once every 25 hours2.893519e-4 days <br />0.00694 hours <br />4.133598e-5 weeks <br />9.5125e-6 months <br />, we will notify the System Engineer, the Resident Inspector and NRC Region I'should the frequency increase to once per eight hours. At this point, a visual inspection will be conducted to determine the characteristics l
of the leakage.
The Unit will be shutdown in approximately two weeks for a refueling outage at which time the pipe will be repaired or replaced.
1 I
This relief is requested immediately in order that Unit 2 may continue operating until the scheduled refueling outage.
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Pursuant to 10 CFR 170.21, we are including BG&E Check No. 1920662 in the amount of
$150.00 to the NRC to cover the application fee for this request.
1 Should you have any further questions regarding this request, we will be pleased to discuss them with you.
Very truly yours,
)
LBR/dtm i
1 Attachment cc:
D. A. Brune, Esquire J. E.
Silberg, Esquire R. A.Capra, NRC S. A. McNeil, NRC W. T. Russell, NRC II. Eichenholz/V. L. Pritchett, NRC T. Magette, DNR l
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