ML20010G819

Final Deficiency Rept Re Unconservative Mass Load Ratings for Cantilever Supports Supplied by Bechtel,Initially Reported 810810.Also Reported Per Part 21.Bechtel Has Modified Computer Code Input & Sent Corrected Data to Util

ML20010G819
Person / Time
Site:	Yellow Creek
Issue date:	09/09/1981
From:	Mills L TENNESSEE VALLEY AUTHORITY
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
REF-PT21-81 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8109220552
Download: ML20010G819 (2)

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, .. TENNESSEE VALLEY AUTHORITY CH ATTANOOGA. TENNESSEE 37401 400 Chestnut Street Tower II September 9, 1981 YCRD-50-566/81-23 Mr. James P. O'Reilly, Director

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. Office of Inspection and Enforcement Y2 '

U.S. Nuclear Regulatory Commission E - ,

Region II - Suite 3100  ;- ' _;

101 Marietta 'treet 5 Atlanta, Georgia 30303 > 2 co

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Dear Mr. O'Reilly:

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YELLOW CREEK NUCLEAR PLANT UNIT 1 - CANTILEVER SUPPORTS SUPPLIED BY BECHTEL

- YCRD-50-566/81 FINAL REPORT _,

The subject deficiency was initially reported to WRC-0IE Inspector D. Quick on August 10, 198* in accordance with 10 CFR 50 55(e) as NCR YCN YCP 8105. Enclosed is our final report. We consider 10 CFR Part 21 to be applicable to this deficiency.

If you have any questiens concerning this matter, please get in touch with D. L. Lambert at FTS 857-2581.

Very truly yours, TENNESSEE VALLEY AUTHORITY 4 to

• 0 }e L.M. Mills,Mankger$ - -

Nuclear Regulation and Safe @f P 2 21981 u s. r ga ni aiont 7

Enclosure

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cc: Mr. Victor Stello, Jr., Director (Enclosure) ffj -Nu- (@

Office of Inspection and Enforcement U.S. Nuclear Regulatory Commission .

Washington, DC 20555

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i 8109220552 810909' PDR ADOCK 05000566 S pDR An Equal Opportunity Employer L

ENCLLSURE YELLOW CREEK N" CLEAR PLANT UNIT 1 CANTILEVER PIPE SUPPORTS SUPPLIED BY BECHTEL YCRD-50-S66/81-20 10 CFR 50.55(e)

FINAL REPORT reacription of Deficiency Values for mass load ratings for "L," T," and simple typical ' cantilever support structures supplied to TVA by the Bechtel Corporction, Gaithersburg, Maryland, were found to be unconservative when compared to -

results obtained by TVA using GTSTRUDL program. Mass load ratings are used by TVA to obtain a spring rate for each of the above structure types. The mass load ratings are structural load capacities which correspond to 33 Hz and 20 Hz minimum support natural fecquencies. Minimum natural frequency requirements and minimum spring rates for structural pipe supports are required in TVA Design Criteria N8-50-D716 for piping analysis.

The deficiency was discovered by TVA while reviewing the spring rates for the "L" type cantilever typical support drawings (TVA YCP draw $ng series 3GB0160-00, sheets 75-78, and 80-84). All information from Bechtel was compared to GTSTRUDL runs made by TVA, and Bechtel was notified of the error. This error affects 852 supports on 27 sheets of the YCP drawing series 3GB0160-00. None of these drawings have been issued for construction.

Upon notification of the error, Bechtel immediately investigated the problem. They discovered that the base plate flexibility values supplied by TVA were incorrectly input into their computer programs.

Safety Implications If the described deficiency had gone uncorrected, it could have caused the "L," "T," and simple typical cantilever supports to be fabricated such that they would not meet the 33 Hz minimum natural frequency. This would not create any safety-related problems since supports with lower natural frequencies can be justified if the support spring rate is determined and documented by the piping analyst.

However, since minimum spring rates are required for rigorous piping analysis, the integrity of rigorously analyzed piping and support systems could have been compromised. Supports would have had actual spring rates -

lower than those represented in the rigorous piping analysis. Use of incorrect spring rates in the design of pipe supports could result _ in overstress of piping systems, thus adversely affecting the safety of operations of the plant.

Corrective Action Bechtel has modified their computer code input and has transmitted i ccrrected data.to TVA. ,TVA is performing the necessary calculations and will revise the drawing series 3GB0160-00, sheets 60-63, 65-69, 75-78, 80-84, 90-93, 95-99. This work is expected to be completo by December 1, 1981. To prevent recurrence of this situation, TVA will continue to spot .

check work performed by outside- firms before issuance of affected - - ~ ~ ~ -

construction drawings.

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