ML20004D896

Updated Deficiency Rept Re Power Block Pipe Whip Restraint Design Discrepancies.Design of Potentially Affected Restraints Has Been Reviewed & Revised,Where Necessary.Final Rept Will Be Provided by 810601

ML20004D896
Person / Time
Site:	Wolf Creek, Callaway
Issue date:	03/16/1981
From:	Seiken S STANDARDIZED NUCLEAR UNIT POWER PLANT SYSTEM
To:	James Keppler, Seyfrit K NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III), NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
10CFR-050.55E, 10CFR-50.55E, SLNRC-81-014, SLNRC-81-14, NUDOCS 8106100278
Download: ML20004D896 (2)

Text

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O SNUPPS I suas.,via.s we , unit Po-** Puai sn=a Mardh 16, 1981

'.n U I N U aceso SLNRC 81- 014 FILE: 0491.10.2/M-202B D013 888 8010 SUBJ: Follow-up Report on SNUPPS Pipe Whip Restraint Design Discrepancies "Mr. James G. Keppler Director, Region III Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, Illinois 60137 Mr. Kar i Seyfrit

, Director, Region IV U.S. Nuclear Regulatory Commission Suite 1000, Parkway Central Plaza 611 Ryan Plaza Arlington, Texas 76012 Ref: SNLNC 81-003 dtd. 1/23/81: Pipe Whip Restraint Design Discrepancies Gentlemen:

The reference letter forwarded to NRC, a preliminary report concerning

. a potential discrepancy in the design of SNUPPS standard power block pipe whip restraints. The purpose of this letter is to update the reference report and to provide a sumary of actions being taken by the Architect-Engineer, Bechtel Power Corporation, to resolve this matter. At the suggestion of Mr. R. T. Carlson, Region I, this follow-up report is being issued simultaneously to Regions III and IV. Future reports in-volving generic SNUPPS defects and/or discrepancies and responses to IE Bulletins will be handled similarly.

The reference letter indicated concer: sith the analytical techniques used by Bechtel in the design of thE SNUPFS pipe whip restraints. The design concept of the SNUPPS restraints accounts for dynamic impact effects by the use of an energy-absorbing device [ stainless steel honey-comb energy-absorbing material (EAM) or stainless steel upset U-bolts).

These energy-absorbing devices are attached to carbon steel support structures which transfer the loads into the primary building structure.

Design criteria developed for the SNUPPS project' impose the requirement that dynamic impact effects be analyzed in accordance with Bechtel Topical BN TOP 2 and energy balance equations developed specifically for the energy-absorbing device applications. .

Althoughenergy-absorbingdevicesareemployedasreouired7thesiefg"y[st 3j balance analysis was not conducted properly on restraints.which%y-Tt i '

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( analysis port could develop structure. a plastic A total of hinge on of 103 restraints the242ruptured pipe 3at previous'if the sup id6edt 7 1981 g Genhersburg Pcwe Div.

Swb?S hm.ica 1M55 8106100 29T

a SLNRC 81- 014 Page Two I

for construction had the potential of'being affected, primarily for smaller size piping. The design of these restraints has been reviewed and revisions, where necessary, are currently being made to properly satisfy energy balance considerations. This discrepancy was found during 1 an internal Bechtel review of the design criteria.

Ouring the review of the potentially affected restraints, a second ques-tion arose when it became apparent that, in some cases, the size of the U-bolts (diameter) was increased after the computed diameter was deter-mined; or, in some instances, the cross-sectional area of the EAM was similarly increased without a corresponding increase in the support structure strength. Such action has the potential of making the U-bolt or EAM ineffective in absorbing energy. The design of all restraints has since been reviewed and revisions, where necessary, are presently being made. A total of 43 restraints have been modified to address the first two items of concern.

While the above concerns appear to have been adequately addressed, it has been determined that additional information must now be generated to re-solve a third item. Specifically, the support structures for all pipe whip restraints are designed, using elastic design :pethods, for a strength at least 10% greater than the strength of the EAM, or the upper bound l

strength of the U-bolt. During the review of the total restraint design ~

' it was determined that additional information is required to demonstrate

( that the support structures have sufficient ductility to absorb the loads imposed by the energy-absorbing device. Further analysis is required to address this matter and to confirm the load transfer capability of the support structures. In the event adequate confirmation cannot be pro-vided, the required ductility of the support structure can be obtained after the restraint is installed. Depending on the final.results of the Bechtel study, this could result in direction to the field to make minor on-site modifications such as cutting the flange of a support structure.

As discussed with Mr. Carlson on Feb. 26, 1981, several weeks of addi-tional analysis and study will be required to resolve the outstanding concerns regarding support structure ductility. At the present time, we anticipate a final report being available bi June 1st. We will notify each of you promptly in the event this target date requires change. In the interim, please direct any questions on this matter to the undersigned.

Very truly yours, 1

C1

. J. Seiken Quality Assurance Manager SJS:dek:6a14 cc: G. L. Koester, KGE J. Konklin, NRC Region III D. T. McPhee, KCPL T. Vandel, NRC Wolf Creek J. K. Bryan, UE Victor Stello, Jr., Director, Office of W. Hansen, NRC/Callaway I t, E. USNRC, Washington 0.C.

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