ML20010B399

Interim Deficiency Rept Re Containment Box Beam Design. Reanalysis of Affected Beams Underway Using Updated Criteria.Next Rept by 811101

ML20010B399
Person / Time
Site:	Limerick
Issue date:	08/07/1981
From:	Kemper J PECO ENERGY CO., (FORMERLY PHILADELPHIA ELECTRIC
To:	Grier B NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION I)
References
10CFR-050.55E, 10CFR-50.55E, NUDOCS 8108140440
Download: ML20010B399 (2)

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'2**'-4= 2 t/33f AUG 7 - 19M Mr. Boyce Grier, Director United States Nuclear Regulatory Commission Office of Inspection and Enforcement, Region I 631 Park Avenue King of Prussia, PA 19h06

Subject:

Significant Deficiency Report Wh5 Interim Report of Containment Bol:

Beam Design Deficiencies Limerick Generating Station Units 1 & 2 NRC Construction Fermit Nos. CPPR 106 & 107

Reference:

Telecon of July 9, 1981 H.R.Walters(PECo.) toe.B.McCabe(NRC)

File: QUAL 2-10-2 (SDR #h5)

Dear Mr. Grier This is an interim report regarding the design of the containment box beams. We have been unable as yet to determine if this is reportable under 10 CFR $0.55(e).

The subject box beams are structural supporting elements inside  ;

containment. They support pipe whip restraints, snubber loads, pipe supports, equipment, and grating. The most significant design loads for the majority of the beams are the jet impingement / pipe whip restraint loads.

There are 77 box beams per unit on four elevations inside the drywell.

The Unit 1 beams are presently erected; approximately 15 out of the 77 beams are presently erected in Unit 2. All beams are fabricated and 2elivered to the jobsite.

The beams range in cross-section from 8-1/2" x 8-1/2" to 2h" x 2h".

Beam vabs rarge in thickness from 1/2" to 1-1/2", while beam flanges range in tLtekness from 1/2" to 2-1/h".

During fit-up of the Unit 2 box beams, a nonconformance report was issued by Site Quality Control personnel which described what appeared to be undersized welds at the flange-web interface on some of the box beams.

These welds were subsequently determined to conform to approved project requirements; however, it was discovered during a review of the original calculations for those beams that the shear stresses for most of the box beams nad not be6n appropriately comb'.ned.

1. 1. f 8108140440 810507 PDR ADOCK 05000352

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, 4 Mr. Boyca Gritr, Direct::r

-Page 2 Subsequent to the referenced telecon we have continued our analysis of the effects of failure to appropriately combine shear stresses'in most of the subject beams during the performance of the original calculations.

It has not been determined that failure to detect the problem would have affected the functional safety of the plant.

The original pipe whip loads on the box beams were established based on the criteria available at that time. Presently available methodology, committed to by the FSAR and which is consistent with NRC Standard Review Plans, will probably yield higher loads than used in the original design.

A complete reanalysis of all affected' box beamo.is presently being done to the latest criteria to determine if any of the beams, in view of the problem noted, would experience a loss of function. Separate from the safety / loss-of-function question, preliminary analysis to date indicates that the beams could possibly exceed allowable stresses. If this is the case, such beams will be modified as required.

In summary, a complete reanalysis of the affected box beams is presently being done, taking into account the as built conditions and loads which are consistent with FSAR requirements. Design of modifications which may be necessary is proceeding. This work will consider refined analysis of beam capabilities, best current load definitions, additional bracing, and beam reinforcement. It is expected that this reanalysis will be completed by mid-October, 1981. Our next report of this effort will be submitted to you on or before November 1, 1981.

Sincerely, S $;b JJW/ dmo Copy to: Direetcr of Inspection and Enforcement United States Nuclear Regulatory Commission Washington, DC 20555 J. P. Durr, Resident NRC Inspector i

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