ML19273A998

LER 79-001/03L-0 on 790106:excessive Reactor Coolant Sys Unidentified Leakage.Caused by Cracked Weld on Socket Weld Downstream of Second Isolation Valve.Study Planned to Propose Design Changes to Correct Fatigue Problem

ML19273A998
Person / Time
Site:	Calvert Cliffs
Issue date:	01/24/1979
From:	Davis S, Watkins K BALTIMORE GAS & ELECTRIC CO.
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
Shared Package
ML19273A996	List: ML19273A995 ML19273A998
References
LER-79-001-03L, LER-79-1-3L, NUDOCS 7902010182
Download: ML19273A998 (2)

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(PLEASE PRINT OR TYPE ALL REQUIRED INFORMATION) 7 o 1 8 9 l M lLICENSEE 0 I CCODE l C l N I N l@l 0 0l-10l0101010l-14 15 LICENSE NUMBEM 010l@l42b 26 11111Ill@l LICENSE TYPE 40 l

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74 75 REPORT DATE 80 7 8 61 NUMBER DATE EVENT DESCRIPTION AND PROBABLE CONSEQUENCES h O 2 l At 0900 Reactor Coolant System (RCS) unidentified leakage was 1.546 ann, exceedino I O 3 lthe amount allowed by T.S. 3.4.6.2.C. At 0930 commenced power decrease to l o 4 l'investicate leakaoe around 21 A reactor coolant oumo (RCP). 21A RCP middle 1 0 s Iseal pressure sensing line was found to have a cracked weld and was isolated. j O 6 lRCS leakage was determined to be less than 1 apm at 1448. LERs 77-15 (U-1) l 0 7 land 78-50 (U-2) describe similar events. I O 8 l l 7 8 9 80 C DE CODE SUBCO E COMPONENT CODE SUB CO D'E SU E 7

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c' LER 79-01/3L EVENT DATE 1/6/79 REPORT DATE 1/24/79 DOCKET NO. 50-318 ATTACHMENT CAUSE DESCRIPTION AND CORRECTIVE ACTIONS: (CONTINUED)

Upon investigation the cracked weld was found to be located on a socket weld downstream of the second isolation valve. Weld repairs were performed for return to service. A vibration analysis performed during the past refueling outage determined that fatigue levels of vibration existed at several locations on RCP instrument piping / tubing. Braces added to this piping have reduced but not eliminated vibration. An engineer 219 study is underway to propose design changes to correct the fatigue problem.

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