ML20086J162

AO 74-34:on 741207,hydraulic Snubber Found Inoperable on Main Steam Relief Valve Discharge Piping.Caused by Loosening of Lock Nuts Due to Vibration.Snubbers Associated W/Discharge Lines RV-71E & RV-71J That Were Rotated Removed

ML20086J162
Person / Time
Site:	Peach Bottom
Issue date:	12/17/1974
From:	Cooney M PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Giambusso A US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086J166	List: ML20086J162 ML20086J167
References
AO-74-34, NUDOCS 8401230272
Download: ML20086J162 (3)

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Mr. A. Giambusso Deputy Director of Reactor Projects U.S. Atomic Energy Conmission Directorate of Licensing Washington, DC 20545

Subject:

Abnormal Occurrence , The following occurrence was reported to Mr. Walt Baunack, A.E.C. Region 1 Regulatory Operations Office on December 8,1974. < Written notification was made to Mr. James P. O'Reilly, Region 1 Regu- e latory Operations Of fice on December 9,1974. In accordance with Section 6.7 2.A of the Technical Specifications, Appendix A of DPR-44 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 3 11.D.1 Report No.: 50-278-74-34 y Report Date: December 17, 1974 ) Occurrence Date: December 7, 1974 5 Facility: Peach Bottom Atomic Power Station Unit #3 $ R.D. #1, Delta, Pennsylvania 17314 Identification of Occurrence: Inoperable hydraulic snubbers on main steam relief valve dis-charge piping. Conditions Prior to Occurrence: Reactor shutdown. Description of Occurrence: During a routine inspection of Unit #3 drywell hydraulic snubbers, in conjunction with a unit outage, six hydraulic snubbers on p329-{j/*[ 0 the main steam relief valve discharge piping were found inoperable. 70 8401230272 741217 PDR ADOCK 05000278 PDR 12855 ( 6 COPY 9ENT REGION ,

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Mr. A. Giambusso tj December 17, 1974 Page 2 These were associated with the E, J, and F relief valve discharge lines. Two snubbers were found to be rotated such that the reservoir was below the hydraulic cylinder and were, therefore, empty. They were on RV-71E (3-1-GG-S-2) and RV-71J (3-1-GG-S-8) discharge lines. Faur snubbers on RV-71F discharge line were found to be in-operable for the following reasons: one reservoir was found empty (3-1-GG-S-68); on one snubber (3-1-GG-S-10) the threaded extension to i the cylinder was bent at approximately 150 from its original alignment and the reservoir was moved out of position and empty; another snubber (3-I-GG-S-69) had f ailed at the point where the piston rod connects to the pipe clamp and the clamp had moved down the discharge line approx-imately one foot; the fourth snubber (3-1-GG-S-9) had failed at the point where the rod end attaches to the piston rod. 4 Designation of the Apparent Cause of Occurrence: The snubbers which were found inverted (3-1-GG-S-2 and 3 GG-S-8) have lock nuts provided on the cylinder extensions to maintain . the snubber assembly in the proper orientation. The loosening of these {'~ ~ nuts, due to vibration, is the most probable cause of the rotation of the two snubbers. These are the snubbers associated with RV-71E and RV-71J respectively. Snubbers associated with the RV-71F relief valve discharge piping were investigated by Philadelphia Electric Company's Engineering f~ Department and the Architect Engineer to determine the probable cause of failure. The snubber 3-1-GG-S-10 was found rotated so that the re-servoir was empty and the rod end was bent. The loosening of fasteners on other snubbers arid pipe clamps could result in bending stress in snubber parts causing their f ailure. Either rotation and emptying of the reservoir, or bending stress failure in any given snubber would result in unanticipated loads on the remaining snubbers thus causing the observed failures. Analysis of Occurrence: No discharge of steam to the drywell resulted from the snubber deficiencies. An inspection of the piping has revealed no failures. _ Safety implications are, therefore, minimal. ' Corrective Action: The snubbers associated with the RV-71E and RV-71J discharge lines that were found rotated were removed, returned to operable con-dition, tested, and reinstalled. The pipe clamp associated with snubber

   '3-1-GG-S-69 was repositioned and tightened. Manger 3-1-GG-H-323 was realigned and clamps tightened. One cylinder assembly was replaced.

One rod end attachment was repaired. The damaged cylinder extension and reservoir support were straightened. Following repairs, the snubbers were filled, tested, and reinstalled. The lock nuts on all snubbers in the drywell were checked for tightness to preclude future rotation of,snubters.

I l Mr. A. Giambusso__ ' <-

   .      D ccmber 17, I S'     :                               (v )        Pcg] 3
      ,                    v A volumetric and surface inspection of the RV-71F piping from the main steam header to the valve was performed by Southwest
 ,        Research Institute in conjunction with Philadelphia Electric Company's Engineering and Research Department. A surface inspection of the re-lief valve discharge piping was also performed. No significant defects were found. Wall thickness measurements indicate that wall thickness exceeds minimum wall requirements. Consequently, the piping system remains capable of performing i t, operating service as designed.

An Engineering review of the support system for this particular dis-charge line was performed and it has been found to be adequate. Failure Data: Abnormal Occurrence Reoort Numbers 50-278-74-8, 50-278-74-16, and 50-277-74-45 Very truly yours, M I L c' H. J. Cooney

                                                                  .g A'ss ' t Gen' t Superintendent Generation Division cc:   Mr. J. P. O'Reilly Director, Region 1 U. S. Atomic Energy Commission 631 Park Avenue King of Prussia, PA    19406 O

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