ML20002E389

Interim Deficiency Rept Re Apparent Disparity Between B&W Mathematical Model of Upper Steam Generator Support Sys & Actual Hardware,Initially Reported 801223.Caused by Manner in Which Forces Were Reported.Final Rept Expected by 810223

ML20002E389
Person / Time
Site:	North Anna
Issue date:	01/22/1981
From:	Spencer W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
044, 10CFR-050.55E, 10CFR-50.55E, NUDOCS 8101270707
Download: ML20002E389 (6)

Text

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VIRGINI A ELECTRIC AND POW ER COMP ANY, RICHMCNO. VIRGINI A 23261 January 22, 1981 Mr. James P. O'Reilly, Director Serial No. 044 Office of Inspection and Enforcement PSE&C/DCC:bw U.S. Nuclear Regulatory Connission Region II.

Docket Nos. 50-404 101 Marietta Street, Suite 3100 Atlanta, Georgial30303

Dear Mr. O'Reilly:

UPPER STEAM GENERATOR SUPPORT SYSTEM NORTH ANNA UNIT 3 On December 23, 1980, NRC Region II was notified under the provisions of 10CFR50.55(e) concerning an apparent disparity between the Babcock and Wilcox mathematical model of the Upper Steam Generator Support System and the actual hardware. This item was also reported as being covered by 10CFR21.

In accordance with the applicable reporting requirements, we submit this 30 day report as an Interim report on this disparity. A final report will be submitted no later than February 23, 1981.

The report stated that data, resulting from the use of this model for the required loading analysis, could be affected. Therefore, this data could potentially lead to unconservative results when used in the stress analysis of the supporting steel and concrete.

In subsequent telephone conversations with your Mr. P. K. VanDoorn on December 31, 1980 and January 2, 1981, it was confirmed that this potential deficiency was unique in nature and affected no other plants, either under construction or in operation. This is due primarily to the unique Babcock and Wilcox/ Stone and Webster interface that exists for North Anna Unit 3.

The apparent disparity resulted from the manner in which forces were reported in the Babcock and Wilcox Functional Specification 18-1235000017-09 for Reactor Coolant System Foundation and Nozzle Loadings. Forces in both the plus Z and minus Z directions were reported for Point 4 (see the attached figure). This loading point represents a compression connection between the trunnion support and the crane wall at Points A and B (also shown on the attached figure). From the design, the trunnion support can. transmit no tension load to the wall. However, since the analysis is based upon a linear, elastic mathematical model, each element transmitting axial loads must carry both tensile and compressive forces. When results are tabulated for a structure carrying only i

compressive forces, special care must be taken to ensure that the loads are reported properly.

S 81omo7o7

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2 VIRGINIA ELECTRIC AND POWER COMPANY To Mr. James P. O'Reilly The hardware configuration of the Upper Steam Generater Support System is beir.g carefully evaluated to ensure that the Babcock ani 'ilcox mathematical model is accurate and applicable to the analyses being performed. Primary concerns regard the nature of the connections at each end of the trunnion supports and their loading capabilities as bolted, friction connections. The outcome of this study will provide direction as to the proper manner in which to treat the loads being tabulated for Point 4 and other related support points.

As noted above, this letter represents an interim report on this matter. We do expect to submit the final report on or before February 23, 1981.

ruly, pours, Ver

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w W. C. Spencer

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Vice President - Power Statio Engineering and Construction Services cc: Mr. Harold R. Denton, Director Office of Nuclear Reactor Regulation

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