ML20012E995

LER 89-014-01:on 890723,determined That Salt Water Header Not Capable of Withstanding Seismic Event Intact.Caused by Inadequate Welding of Blind Spool Pieces in Pipe.Insp Revealed Spools Capable as installed.W/900328 Ltr

ML20012E995
Person / Time
Site:	Calvert Cliffs
Issue date:	03/28/1990
From:	Denton R, Furio P BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-89-014, LER-89-14, NUDOCS 9004090272
Download: ML20012E995 (4)

Text

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AB ALTIMORE CASAND ELECTRIC CHARLES CENTER e P.O. DOX 1475

• DALTIMORE. MARYLAND 21203 1475 CALVERT Cliff t NUCLEAR POWER PLANT DEPARTIAINT CALytRf CLIFF b NUCLE AR l'OWtp PLAN 1 LLf89T h4ARVAND RL*M March 28, 1990 U. S. Nuclear Regulatory Conunission Docket No. 50 317 Document Control Desk License No. DPR 53 Washington, D. C. 20555

Dear Sirs:

The attached LER 89 14 Revision 1, is being sent to you as required under 10 CFR 50.73 guidelines.

This event was determined to be not reportable under the requirements of 10CFR50.73. However, due to the construction related nature of the event and the need for investigation into similar systems, we believed it was prudent to inform the NRC of this event.

Should you have any questions regarding this report, we would be pleased to discuss them with you.

Very truly yours, (w>~h -

R. E. Denton Manager PJIB/lr cc: William T. Russell Director, Office of Management Information and Program Control Messrs: G. C. Creel C. 11 . Cruse L. . 1 Q,M f 39E bb 7 WE R. P. lleibel 900409017; 9003;g PDR ADOCK 05000317 en [h k M S PDC p/

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\ tS II* ves temsuste ExPECTIO SL'OstisSION OA rti ko l l l At$T A ACT (& f,Nr te f EIO .peces e e . .ea,osewww terreea empre apere typee,etsen 8, nest nel on July 23, 1989, while Unit I was in cold shutdown, it was determined that the No. 12 saltwater header was not capable of withstanding a seismic event intact.

If the No. 12 saltwater header failed, it would have resulted in the failure of the No. 12 service water heat exchanger and the No. 12 component cooling water heat exchanger. The failure van determined to be caused by inadequate welding of the blind spool pieces in the pipe.

Walkdowns were pe rfornied on the other blind spool pieces in the Salt Water System, Service Water System, and the Component Cooling Water System. The inspection and analysis of these spool pieces determined they were capable of withstanding a seismic event as installed. The spool pieces in the Salt Water System have been repaired with continuous welds. Analysis shows that the piping will now remain intact during a seismic event.

This event was determined to be not reportable under the requirements of 10CFR50.73. Iloweve r , due to the construction related nature of the event and the need for investigation into similar systems, we believed it was prudent to inform the NRC of this event.

NaC P.,. a..

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I. DESCRIPTION OF EVENTS On July 23, 1909, while Unit 1 was in cold shutdown, it was determined that the No. 12 saltwater header (EIIS KE PSX) was not capable of withstanding a seismic event intact. If the No. 12 saltwater header failed, it would have resulted in the failure of the No. 12 service water heat exchanger (EIIS BI ilX) and the No. 12 component cooling water heat exchanger (EIIS CC HX).

The failure was determined to be caused by inadequate welding of the blind spool pieces (EIIS RE PSP) in the pipe.

Blind spool pieces were installed in the saltwater piping to remove the cross tie capability that had been designed into the system. To install a spool piece, a valve was removed and blind flanges were bolted onto each end of the pipe opening. A piece of pipe was then welded to the blind flange to provide structural support for the ends of the pipe.

In the spring of 1989, a walkdown of the saltwater piping to support an unrelated design effort revealed that the welds on th9 spool pieces were not continuous welds, but only tack welds. The tack welds are not considered structurally adequate. The tack welds were replaced with continuous welds. An analysis was then performed to determine the effect of a seismic event assuming no support would be provided by the tack welded pipe sections. The analysis assumed that the blind spool pieces did not exist during a seismic event. This analysis revealed that the loose pipe ends would not f ail, with the exception of the No.12 header. The analysis determined that the header would fail somewhere between the loose pipe end and the first seismic pipe support. Even though the section of pipe that fails is blind flanged, back flow from the No. 12 saltwater pump (EIIS KE-P) would cause the header to lose pressure. The header would fail to provide cooling water to the service water train and the component cooling water train that it normally feeds.

These modifications were made during the original construction of the plant. It is not known if the blind spool pieces were designed to be tack welded or if personnel error was involved. The thirty (30) other blind spool pieces in the Salt Water System, Service Water System, and the Component Cooling Water System were inspected and determined to be capable of withste.nding a seismic event as installed.

This event was determined to be not reportable under the requirements of 10CFR50.73. However, due to the construction related nature of the event and the need for investigation into similar systems, we believed it was prudent to inform the NRC of this event.

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0 l1 0l 3 0F 0 l3 mt w,s . w. .am.* Naci mmon II. ANAINSI S The Salt Water System provides cooling water to the service water heat l exchangers and the component cooling water heat exchangers. The design basis for the system, as stated in the FSAR, is that one saltwater pump has sufficient head and capacity to provide cooling water for the Service Water and Component Cooling Water Systems as required by 10CFR50 Appendix A. A single failure analysis done for the Salt Water System assumes a passive failure (pipe rupture) could occur anywhere in the system without signi f-icant consequences. For post LOCA operation, the Salt W cer System is assumed to have only one header available to provide cooling water to meet the accident unit's cooling requirements. Technical Specification 3.7.5.1 requires that two Salt Water Systems be maintained operable during Modes 1, 2, 3, and 4. The action statement requires that the Unit be brought to cold shutdown if a Salt Water System remains inoperable longer than 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. This action statement does not allow long outage times for maintenance of the Salt Water System. Therefore, this has minimized the  !

plant operating time .;ith only the No. 12 header in service, and minimized the risk of losing saltwater cooling capability during a postulated seismic event.  :

III. CORRECTIVE ACTION The spool pieces in the Salt Water System have been repa!*cd with continuous welds. Analysis shows that the piping will now remain intact during a seismic event. The thirty (30) other spool pieces in the Saltwater System, Service Water System, and Component Cooling Water System were inspected and determined to be capable of withstanding a seismic event.

NRC Pense 304A 4640)

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