ML20010E171

Part 21 Rept Re Load Transfer Design of Primary Loop Crohsover Leg Pipe Restraints,Initially Reported on 810706. Design Reanalyzed,Modified Restraints Installed & Review of NSSS Designs Initiated

ML20010E171
Person / Time
Site:	Vogtle
Issue date:	08/21/1981
From:	Randy Patterson BECHTEL GROUP, INC.
To:	Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
REF-PT21-81-489-000 PT21-81-489, PT21-81-489-000, NUDOCS 8109030167
Download: ML20010E171 (4)

Text

as at TE H $wst)6,DMU Gie Bechtel Power Corporation Engineers - Constructors 12400 East impenal High Aay Nor.va* Canfomia 90650 v An 4:x w ss F' O tv in N N#di f f H9 NA4 A%f s (! % AV .F l f 5 C Al et ( lMN. A a u sO Y{ Lif% 94 f 213 4M eni11

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August 21, 1981

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Mr. Karl Seyfrit

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t Director, Region IV I~j U c i' 0 219315 ,-

Office of Inspection and Enforcement ' 'i u.s."m* eA, mmy' U. S. Nuclear Regulatory Commission \ *

• 611 Ryan Plaza Drive Suite 1000 Arlington, Texas 76012 fkc N,'

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SUBJECT:

Deficiency Regarding Design of Primary Loop Crossover Leg Pipe Restraint

Dear Mr. Seyfrit:

Evaluation by Bechtel of the captioned condition indicates the condition is reportable under 10 CFR 21.

The attached report and the following paragrapn contains all the information required by 10 CFR 21, 21.21(b)(3).

Although the design is considered unique to the Vogtle project, other Bechtel Divisions were notified by copies of reports and correspondence of the deficiency. Should it be determined that this design concept has been or will be used on other Bechtel projects, the affected Division will report the condition according to the Regulation.

Very truly yours, BECHTEL POWER CORPORATION n.n f /f a+ - -

R. L. Patte, son Manager of Division Quality Assurance RLP:AGC:lm f, 0 8109030167 810821 O PDR ADOCK 05000424 AjU S PDR

' REPORT OF

! DEFICIENCY REGARDING DESIGN OF PRIMARY LOOP CROSSOVER LEG PIPE RESTRAINTS ALVIN W. V0GTLE ELECTRIC GENERATING PLANT - UNITS 1 AND 2

1.0 INTRODUCTION

This report is submitted pursuant to 10 CFR 21 and describes l actions undertaken to correct a potential substantial safety hazard /significant deficiency associated with primary loop cross-over leg pipe restraints designed by Bechtel Power Corporation and delivered to Georgia Power Company (GPC) for the Alvin W. Vogtle i Electric Generating Plant , Units 1 and 2, Docket Numbers 50-424 and 50-425. This potential deficiency was verbally reported to the NRC on July 6,1981 by Georgia Power Company and by letcer on July 31, i

1981.

2.0 INDIVIDUAL REPORTING R. L. Patterson, Bechtel Manager of QA 4

3.0 FACILITY Vogtle Electric Generating Plant, Units 1 and 2 (Georgia Power y

Company) , Burke County , Georgia.

1 j 4.0 SUPPLYING FIRMS Design: Bechtel Power Ccrporation, Los Angeles Power Division 5.0 BASIC COMPONENT IDENTIFICATION a

Primary loop crossover leg pipe restraints (4 per unit). The crossover leg restraints are rigid frame steel weldments consisting of a horizontal beam spanning three vertical colunns. The restraint is anchored through the containment liner into t?e basemat. A 2'-

i 9" fill slab is placed over the basemat liner, c abeding the restraint to within 2 inches from the top of the columns.

6.0 DEFICIENCY DESCRIPTION As a result of a request f rom GPC Construction to relax alignment and contact bearing requirements and an additional request to substitute connection bolting materials, the crossover leg restraint design calculation was reviewed. During the course of this review a deficiency was identified in the assumptions used in modeling the transfer of loads from the crossover leg restraint to the fill slab and containment basemat.

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6.0 DEFICIEhCY DESCRIPTION (cont.)

The assumed condition of a free standing crossover leg restraint fixed at the basemat, neglecting the presence of the surrounding 2'-9" thick fill slab, does not adequately represent the existing condition of a partially embedded frame. The presence of the fill slab reduces the flexibility of the crossover leg pipe restraint embedded columns. Because the restraint is a statically indeter-minate frame structure having more than one load carrying path to its anchorage, the externally applied load is distributed to each path in proportion to its relative stiffness. Neglecting the stif fening ef f ect of the fill slab concrete surrounding the columns causes an incorrect distribution of the load, underestimating the strecses in certain elements.

Because the crossover leg pipe restraints are the only statically indeterminate f rame structures in the fill slab, this deficiency is limited to the crossover leg restraint analysis.

70 ANALYSIS OF SAFETY IMPLICATIONS The use of tsre realistic boundary conditions results in stresses which would exceed allowables in bolted connections in the event of a postulated crossover leg pipe break. This condition represents a cubstantial safety hazard.

8.0 CORI:tC'IVE ACTION The following immediate corrective actions were initiated on the proj ect to address this condition:

8.1 The crossover leg restraint design has been reanalyzed to determine the sign stresses consistent with proper boundary conditions.

This reanalysis resulted in the addition of stiffener plates, splice plates, and the modification of bolts to change material and exclude threads from shear planes. These modifications reduce all calculated stresses below the allowable limits.

8.2 The required modifications to the crossover leg restraints were shown on Revision 4 of Drawing IX2D48 LOO 6 and Revision 3 of Drawing 2X2D48L006 which were issued for construction on June 8,1981. The crossover leg restraint modifications have been completed and the modified restraints installed.

8.3 The project has initiated a review of the remaining NSSS restraint and support designs to verify that similar deficiencies do not exist in their design. This evaluation involves technical spe-cialists f rom the Chief Civil / Structural Engineer's of fice as well as project civil engineers. Our review of the other NSSS restraint and support designs that are in the fill slab has been completed and no deficiencies were found. The expected completion date for the remaining designs is September 15, 1981.

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9.0 CONCI.USION This deficiency is considered reportable under 10 CFR Part 21. All applicable project documentation for this report is available for

inspection at Bechtel's facility in Building No. 46, 11445 South Lakewood Boulevard, Downey, California 90241.

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