ML20086J277

AO 74-16:on 741015,hydraulic Snubbers on Piping Between Bypass Valves & Condenser Failed.Caused by Acceleration Amplifiers Out of Calibr.Snubbers Repaired

ML20086J277
Person / Time
Site:	Peach Bottom
Issue date:	10/25/1974
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
References
AO-74-16, NUDOCS 8401230550
Download: ML20086J277 (3)

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y PHILADELPHIA ELECTRIC COMPANY 60-27* O 2301 MARKET STREET PHILADELPHIA, PA.19101 (215) c414oOO October 25, 1974 i). 'S. .

Mr. A. Giambusso '[\

Deputy Director of Reactor Projects l f,/p, O United States Atomic Energy Commission g/

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s ' ((4' - n 7 ,,O IN Directorate of Licensing g,O/'g Washington, D.C. 20545 ' D/.ft, /

Dear Mr. Giambusso:

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Subject:

Abnormal Occurrence Q.%-77..flv

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The following occurrence was reported to Mr. Walt Baunack, A.E.C. Regio n 1 Regulatory Operations Of fice on October 16, 1974.

Written notification was made to Mr. James P. O'Reilly, Region 1 Regulatory Operations Office en October 17, 1974. In accordance with Section 6.7 2.A of the Technical Specifications, Appendix A of DPR-56 for Unit 3 Peach Bottom Atomic Power Station, the following report is being submitted to the Directorate of Licensing as an Abnormal Occurrence.

Reference:

License Number DPR-56 Technical Specification Reference 3 11.D Report No.: 50-278-74-16 Report Date: October 25, 1974 Occurrence Date: October 15, 1974 Facility: Peach Bottom Atomic Power Station R.D. 1, Delta, Pennsylvania 17314 Identification of Occurrence:

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Failed hydraulic snubbers on piping between bypass valves and condenser.

Conditions Prior to Occurrence:

Reactor shutdown.. Primary system pressure 100 psig.

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Mr. A. Giambusso Octobcr 25, 1974 , ,

(a Pega 2 Description of Occurrence:

During a routine inspection of the pipe hanger system following a reactor shutdown on October 15, 1974, four snubbers on the piping between the bypass valves and the main condenser were found to be defective.

The snubber on the #1 bypass valve was physically detached from the piping. The nuts and bolt which hold the eye of the snubber piston to the pipe clamp had vibrated loose. The snubbers on the #2 and #3 bypass lines were connected to the piping, but the pipe clamp had rotated around the pipe approximately 1" to 1-1/2". The snubber on the

1. 6 bypass valve was broken at the point where the attaching eye screws into the end of the snubber piston. All other snubbers appeared to be satisfactory.

Designation of Aoparent Cause of Occurrence:

Out of calibration acceleration amplifiers in the EHC system caused bypass valve fluctuations cn the #1, #2 and #3 bypass valves during a main turbine startup on October 4,1974 and on the #6 bypass valve during a turbine overspeed test on October 7,1974. Cycling of these bypass valves on about a one second interval for several minutes is believed to have caused the daniage noted on the hydraulic snubbers.

Analysis of Occurrence:

It is believed that the cyclic operation of the bypass valve would cause excessive pipe motion. An inspection of the piping support system by the piping support designer following the snubber f ailure did not disclose any additional failures. It appears that no piping overstress occurred as a result of this effort. The type of operation experienced is not expected to reoccur. This occurrence, therefore, has minimal safety implications.

Corrective Action:

Repairs were made to the four snubbers noted. The pipe clamps were tightened and aligned properly. The bolts and nuts were secured such that vibration could not cause loosening. Individual valves were operated at 150 psig and full pressure during the plant startup on October 16, 1974. The full pressure test was observed by the piping support engineer. Piping supports and pipe motion were

. judged proper during these tests.

During the scheduled plant outage on October 19 and October 20, additional inspection of bypass lines #1 and #6 were conducted using both ultrasonic (UT) and magnetic particle (MPT) in spection techniques.

All elbows, plus nine (9) inches of pipe spool on either side of the

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elbows and five (5) feet back from each reducer were inspected. The k

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- - =.. Mr. A. Giambusso October 25, 1974 Page 3 Corrective Action: (con ' t) i UT inspections shows no recordable indications. Seven (7) mill' scale

indications were detected by MPT. All indications were removed by blending, re-inspected and found acceptable.

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The EHC system acceleration amplifiers were recalibrated to

preclude bypass valve fluctuation during future plant operations.

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4 Failure Data:

i i None.

. Very truly yours, 1

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u 7M. . Cooney 1 Asd t Gen'1 Superintendent Generation Division cc: Mr. J. P. O'Reilly Director, Region 1 United States Atomic Energy Conmission

! .i 631' Park Avenue King of Prussia, PA 19406 4

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