ML20086Q598

Final Significant Deficiency Rept SDR 3 Re Main Steam Line Restraints.Caused by Design Error.Affected Restraints Will Be Abandoned & Replaced W/Restraints Designed to Original Criteria & Allowable Stresses

ML20086Q598
Person / Time
Site:	Peach Bottom
Issue date:	03/23/1973
From:	Boyer V PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Kreusi F US ATOMIC ENERGY COMMISSION (AEC)
Shared Package
ML20086Q560	List: ML20086Q598 ML20086Q603 ML20086Q615
References
SDR-3, NUDOCS 8402270640
Download: ML20086Q598 (4)

Text

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O O PHILADELPHIA ELECTRIC COMPANY 2301 MARKET STREET PHILADELPHIA PA.19101 V.S.BoYER 1

Mr. F. Kreusi, Director fd - 42. 7 'l '

Directorate of Regulatory Operations yq United States Atomic Energy Commission Washington, D.C. 20545

Subject:

Significant Deficiency Report - Main Steam Line Restraints Peach Bottom Atomic Power Station - Units 2 and 3 AEC Construction Permit Nos. CPPR-37 and CPPR-38 File: QUAL 2-10-2 SDR No. 3

References:

a) Interim Significant Deficiency Report dated December 7, 1972 b) F. E. Kreusi letter to V. S. Boyer dated December 26, 1972 c) V. S. Boyer letter to F. E. Kreusi dated February 1. 1973

Dear Sir:

In compliance with 10CFR50.55 paragraph (e) we are submitting the attached Significant Deficiency Report concerning the-subject Main Steam Line Restraints.

An Interim Report (Reference a) and status report (Reference c) were submitted to your office previously.

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

We appreciate your extending the time for our response to March 23, 1973 as agreed by telecon of March 13, 1973 between Mr. H. B. Winitsky and Mr. R. Heischman, USAEC DRO I.

Sincerely, tp%

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

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Q) G Significant Deficiency Report - SDR No. 3 Main Stean Line Restraints Peach Bottom Atomic Power Station - Units 2 & 3 AEC Construction Permit Nos. CPPR-37 and CPPR-38 INTRODUCTION AND BACKGROUND Five restraints were specified for each of the four main steam lines to limit the movement of these lines in the event of a postulated pipe rupture. These restraints are located outside of the primary containment in a tunnel down stream of the main steam isolation valves. See Figure 1 attached. The restraints were designed by the Architect-Engineer and the components fabricated off-site by a local vendor. These assemblies were fabricated from plates welded into the two major components of each set of restraints: those assemblies to be embedded in the concrete structure and those which would be field welded to the embeds and act to restrain the pipe.

In November,1971 drawings and specifications were issued for field procurement. Selection of the vendor and approvals for fabrication were made in late 1971. The material to be supplied by the fabricator was specified as ASTM-A-441. Welding details required double bevel, full penetration welds. The specification also required full QA/QC documen-tation. The vendor furnished the Unit 2 assemblies to be embedded with a statement of conformance in late January, W12. Receipt inspection, at the Peach Bottom Site, identified defective welds .7 the sections to be embedded; these welds were subsequently repaired prior to installa-tion. Mill certifications submitted irdicated conformanco to material requirements. These assemblies were installed and embedded in concrete in May, 1972.

During field welding of the restraint assemblies to the embedded assemblies of restraints #2 and #3 for Unit 2, in August 1972, weld toe cracking was observed in the heat affected zone of some field weldc.

This welding problem was resolved by improving the method of preheating the thick base plate material of the embedded portion. In conjunction with this investigation, material samples were taken from the base plate.

DESCRIPTION OF DEFICIENCY Results of the metallurgical investigations indicated that some com-ponents of the embedded material did not conform to the material require-ments as specified by ASTM-A-441. An in-depth metallurgical sampling program was initiated to e:rnmine all plates furnished in the assemblies for chemical properties; selected specimens were also taken for mechanical, physical and microscopic analyses. A metallurgical evaluaticn of these samples and of representative samples of vendor welds also confirmed non-compliance with the project specification.

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ANALYSIS OF SAFETY IMPLICATIONS The main steam lines and their supports are designed to accommodate the effects of and to be compatible with the environmental conditions associated with the normal operation, maintenance, testing and postulated accidents including pipe failure. The restraints adequately protect other structures, systems and components important to safety, against dynamic effects; including, the effects of pipe whipping and discharging fluids that may result from pipe failures and from events and conditions out-side the nuclear power unit.

Failure of a Main Steam Line Restraint due to pipe whip in the event of a postulated rupture of a main steam line could possibly cause distortion in the second Main Steam Isolation Valve (outside of containment) which could affect valve closure. Unrestrained whipping of a main steam line could possibly damage other steam lines or feed water lines outside of containment.

CORRECTIVE ACTION The results of the material tests, analysis of sampled welds, and asso-

! ciated investigations did not provide the required level of confidence in the adequacy of restraints #2, #3 and #4 for Unit 2. Evaluation of Restraints

1. 1 and #5 indicate that they do meet design requirements.

Restraints #2, #3 and #4 for Unit 2 as shown on Figure 1 vill be aban-doned and replaced with restraints designed to the same criteria and allow-able stresses as originnily employed. The new restraints will be anchored to the structure by the use of post-tensioned rods, which eliminate the need for embedments. This new configuration will also be used in Unit 3 for h atraints #2, #3 and #4 To prevent recurrence of similar situations, the following steps have been taken by the Architect-Engineer:

1. An additional review has been performed of all outstanding specifications and purchase orders for Q-Listed materials to ensure that proper documentation requirements are incor-porated and complied with. This was completed on February 20, 1973

2. Ey letter from the Project Manager dated December 15, 1972, Shop Inspection procedures have been strengthened to include formal inspection plans which identify specific documentation requirements, inspection witness points, etc. in order to assure conformance with project requirements.

3 Site Management and QA/QC personnel have received reinforced directives from the Peach Bottom Project Manager, on December 7, 1972, to ensure that they have positive evidence that components are in accordance with applicable codes, design drawings and specifications, prior to their use or installation.

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