ML20086L030

Final Deficiency Rept Re Main Steam Line piping-external Surface Indications.Caused by Hot Tears in High Strain Areas of Pipe Induced During,Bending Process.Program for Exam of High Strain Areas Implemented

ML20086L030
Person / Time
Site:	Peach Bottom
Issue date:	05/20/1974
From:	Boyer V PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Knuth D US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086L017	List: ML20086L030 ML20086L039
References
NUDOCS 8402070118
Download: ML20086L030 (4)

Text

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. O O PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET PHILADELPHIA. PA.19101 (215)841-4500 v.a r.. ... r May 20, 1974 Dr. D. F. Knuth, Director Directorate of Regulatory Operations United States Atomic Energy Commission Washington, D.C. 205h5

SUBJECT:

Significant Deficiency Final Report Main Steam Line Piping-External Surface Indications Peach Bottom Atomic Power Station, Unit No. 3 AEC Construction Permit No. CPPR-38 File: QUAL 2-10-2 SDR No. 7 Roference: Interim Report submitted by V.S. Boyer letter dated February 6,197h

Dear Dr. Knuth:

In compliance with 100FR$0.55 paragraph (e), we are submitting the attached Significant Deficiency Final Report concerning the sub-ject piping indications.

An interim report was previously submitted to your office.

We trust that this satisfactorily resolves the item. If further infomation is required, please do not hesitate to contact us.

Sincerely, Attachment RAN:lew Copy to J.P. O'Reilly, USAEC

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. O O Significant Deficiency Final Repor' - SDR No. 7 Unit No. 3 Main Steam Line Piping External Surface Indications Peach Bottom Atomic Power Station - Unit 3 AEC Construction Permit No. CPPR - 33 Description of Deficiency It was reported to Philadelphia Electric Company the latter part of December,1973, that some extemal surface indications had been visually identified on Unit 3 main steam piping within the primary containment be-tween the reactor vessel and the inner main steam isolation valves. The surface indications were identified by persennel of the examination agency contracted by Philadelphia Electric Company to perfom the pre-opemtional baseline examination of the Units 2 and 3 reactor vessel, piping and equip-nent per ASME Section II requirements. Prior to the perfomance of the actual examination of piping and equipment welds and heat affected zones, the examination agency personnel walk down piping systems to visually examine surfac9 conditions. It was during this walk dcwn that the initially reported indications were observed.

Several initially identified surface indications were reported to AEC DIC f by telecon on January 7,197h and in writing with Philadelphia Electric' Mr. V. S. Boyer letter of February 6,197h, which included as an attachment Sig nificant Deficiency Interim Report - SDR No. 7.

The main steam piping is carbon steel (ASTM A-155 made fmm ASTM A-516, Grade KCF 70 plate) and was supplied by the NSSS vendor. The ring headers and bends in the downcomers are fomed by an incremental bending process during manufactum. Both the piping fabricator and the NSSS vendor con-clude that the indications which have been noted are the result of " hot tears" in the high strain areas of the pipe which were induced during the bending process. Surface indications of this nature if they occur are nomally identified in the manufacturer's shop and repaired prior to shipment to the plant site. A dry powder magnetic particle examination of the pipe was required before shipment. The shop records show that the required magnetic particle examination was perfomed on the Unit 3 piping and no defects were reported or repaired prior to release of the piping from the shop.

Corrective Action

1. A program for examination of the high strain areas of the incremental bended main steam piping on Unit 3 was implemented by NSSS vendor and Philadelphia Electric .9ite personnel. There are a total of four main steam line safety valve ring headers with downcomers on Unit 3 which were examined for " hot tears".

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. O 2- O A total of twenty-seven defects were identified on the main steam piping.

a. Two defacts were located at, the 1200 bend outside radius on "C" and "D" down comers. The largest was approxinately 1" long and 1/8" wide on the "D" downcomer.

b. Twenty-five defects were found on the "A", "B" and "C" loops outside bend radii of the main steam safety valvo ring headers.

The defects were of variable length and depth and the largest was approximately 1" long by 0.080" deep.

Repair procedures for the defects were developed by the NSSS vendor with review and approval of Philadelphia Electric Engineering and Research Department personnel as well as the cognizant Pennsylvania Authorized ASME Code inspector.

A total of 25 defects which wem excavated to below design minimum wall thickness (0.950") were weld repaired with approved qualified personnel and procedures. The data package is available for review at the site.

2. For Unit No. 2, the NSSS vendor and steam piping manufacturer rechecked the Shop Quality Assurance records to assure that hot tears were not in evidence en Peach Bottom Unit 2 piping during fabrication.

Unit No. 2 received a walkdown and baseline examination by the same Section II examination agency personnel who identified the initially reported indications on Unit 3. There were no indications of the nature described above found on Unit 2 piping.

3. Peach Botton Units 2 and 3 steam piping fabrication was completed and shipped appmximately April,1970 and February,1971, respectively.

The NSSS vendor has infomed Philadelphia Electric that similar steam piping systems fabricated in late 1969 and the summer of 1970 have been visually examined using the same technique as that used on Unit 3 with no " hot tears" found.

h. Because of the above reasons Philadelphia Electric engineering and NSSS vendor personnel believe the " hot tear" condition found is unique to Unit 3 main steam piping. Further examination of Unit 2 piping is not doomed necessary at this time, however, future examination of the main steam piping during normal Section II inservice inspection of these areas will be provided.

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Safety Innlications The NSSS vendor has perfomed a fatigue stress analysis for the Unit 3 piping based upon the "as found" defect sizes on a worst case basis and have detemined that the pipe would not have failed in service had the defects been left unrepaired. The analysis detemined that the worst case usage factor is .013 (with 1.0 usage factor the maximum allowable).

The main steam headers were monitored with acoustic mission analysis during the field hydrostatic test, prior to fiE.ing the surface defects.

The surface defects were not recorded by the acoustic analysis indicating that the defects did not propagate during the pressurization of the piping to lh times the vessel design pressure (nominally 1565 psig).

The effects of the Unit No. 3 main steam piping surface defects on safety, utility and operating life has been considered and found acceptable.

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