ML19325C406

LER 89-003-00:on 890808,subsequent Sys Walkdown & Analysis Revealed That as-found Configuration Would Result in Piping Stresses Adjacent to Valves Exceeding Code Limits.Caused by Design & Installation error.W/891006 Ltr

ML19325C406
Person / Time
Site:	Peach Bottom
Issue date:	10/06/1989
From:	Cribbe T, Danni Smith PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-003-03, LER-89-3-3, NUDOCS 8910160183
Download: ML19325C406 (4)

Text

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e \' PHILADELPHIA ELECTRIC COMPANY TdIDs PIACil IK7FIUM ATOMIC POWl:R SlWTION l R. D.1, Ikix 208 '

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D. M. Smith j Vice Psuklent i i

October 6, 1989 l Docket No. 50-278

' Document Control Desk- )

U. S. Nuclear Regulatory Cor. mission l Washington, DC 20555  !

SUBJECT:

Licensee Event Report  !

Peach Bottom Atomic Power Station - Unit 3 ,

This LER concerns the configuration of seismic supports associated with i the Unit 3 Containment Atmospheric Control (CAC) System not being per the r applicable design criteria. ,

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Reference:

Docket No. 50-278 Report Number: 3-89-003 Revision Number: 00 '

Event Date: 08/08/89 Reportability Date: 09/06/89 >

Report Date: 10/06/89  :

Facility: Peach Bottom Atomic Power Station RD 1. Box 208A, Delta PA 17314 This LER is being submitted pursuant to the requirements of 10 CFR 50.73(a)(2)(v).

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Sincerely.

I cc: T. P. Johnson, USNRC Senior Resident Inspector W. T. Russell, USNRC, Region !  ;

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On June 16, 1989, a design contractor performing calculations for a pneumatic tubing modificationtotheContainmentAtmosphericControl(CAC)systemidentifiedthat cperators for two valves would have excessive displacements during a postulated seismic event. The Operators for valves A0-3509 and A0-3510 were lacking seismic supports. Additionally, three piping supports were not in accordance with design field sketches. Subsequent system walkdown and analysis revealed on August 8, 1989, that the as-found configuration, including seven additional deficient existing piping supports, would result in piping stresses adjacent to the valves exceeding Code limits. Evaluation concluded that system operability could not be assured during an operating basis earthquake since loading conditions would exceed the yield stress of the piping material. The deficiencies have existed since initial plant construction, and~are'due to design and installation errors. No adverse safety consequences occurred as a result of this condition. Failure of the 1 inch CAC system piping during a design basis earthquake could have resulted in a loss of primary containment integrity. The deficiencies will be corrected prior to Unit 3 restart. A small bore piping (3 inch nominal or less) survey will be conducted for Unit 2 and Unit 3 to assure the integrity of small bore piping. The delay in assessing reportability of this condition is being addressed in accordance with the site Corrective Action Request program. There were two previous similar LERs.

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-Requirements for the Report This report is required per 10CFR50.73(a)(2)(v) because of the potential for the affected piping not to fulfill its design safety function during required design basis conditions.

Unit Status at Time of Event Unit 2 was in the Run Mode at 100% power. Unit 3 was in the Refuel Mode with the core offloaded.

Description of Event On June 16, 1989 a design contractor performing design calculations for a pneumatic  ;

tubing (EIIS:TBG) modification identified excessive displacements for Containment  ;

Atmospheric Control (CAC) system (EIIS:BB) valves (E!!S:V) A0-3509 and A0-3510. The i calculated large displacements were due to the response of unsupported valve eperators during a postulated seismic event. The valve operators lacked seismic  ;

supports'(EIIS:SPT). These supports were not shown on the design field sketches. ,

Additionally, three piping supports were identified as not in accordance with the >

design field sketches. Two of these were shown on the s. ketches but not installed, cne was installed but not shown on the sketches. Subseyuent system walkdown and l analysis by the contractor on August 8. 1989 avealed taat with the as-found '

configuration of the CAC system supports, cons vering effects from seven additional ,

existing supports which were inadequate fo* selsmic loads, piping stresses adjacent to valves A0-3509 and A0-3510 would exceed Code limits. Subsequent evaluation i concluded that system operability could not be assuret. during an operating basis earthquake since loading conditions would exceed the / 'ield stress of the piping material. System inspection has confirmed that the corresponding Unit 2 CAC piping l 1s supported in accordance with design drawings which include supports on the valve  !

l cperators. l The event date. August 8. 1989, differs from the reportability date September 6. 1989  ;

by 29 dayc. This was the result of delays in evaluating the deficiencies and )

~recognizi y them as potentially reportable.

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Cause'of the Event 1 The cause of the deficient support configuration was a combination of design and installation errors. The deficiencies have existed since initial plant construction. i The valve operator supports were not provided in the initial design. Two pipe I supports were included in the design but not installed, one was installed but not included in the design. The remaining seven supports were installed as designed but their design was deficient.

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0l0 0l 3 OF 0 l3 Analysis of the Event  !

No actual safety consequences occurred as a result of this conditien.

l The supports for CAC system piping are intended to ensure the system will pertorm its  !

design safety function. Valves A0-3509 and A0-L510 are normally closed valves which j ensure primary containment integrity on a 1 inch CAC system vent line. These valves ,

fail closed and have a post LOCA function to relieve excessive drywell pressure. i Failure of the pneumatic tubing alone would allow the valves to either stroke closed normally or fail to the isolate position preventing their reopening and use for the ,

containment vent function. However, the containment vent functithn could be achieved .

via each of two alternate vent paths. i Failure of the 1 inch CAC piping upstream of A0-3509 could compromise primary '

containment integrity and result in leakage from the primary containment to the secondary containment in excess of that assumed in the Final Safety Analysis Report.  ;

Piping failure between the valves or downstream of A0-3510 would be isolated by the closed upstream valve.

Corrective Actions i The identified CAC system support deficiencies are being upgra: led to meet Code li requirements. This work will be completed prior to Unit 3 reste.rt.

A short term small bore piping (3 inch nominal or less) assess, ment program was conducted for both units prior to Unit 2 restart in April, 1909, which indicated a high confidence level in the functional adequacy of small bore piping.

A long term small bore piping survey will be conducted for Unit 2 and Unit 3. This program will involve comparison of selected drawings of record with the as-found ,

configuration to provide additional assurance of the integrity of small bore piping.

The delay in assessing reportability of this condition is being addressed in accordance with the site Corrective Action Pequest program,. ,

Previous Similar Events Two previous similar LERs have been identified. LER 2-88-05 involved non-conformance of the as-built configuration of the Main Control Panels to original installation  ;

requirements. LER 2-89-06 involved nonconformance of the as-built configuration of CAC system pneumatic tubing to modification specificatitsns. Corrective actions for these events could not have prevented this condition because it occurred at initial plant construction.

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