ML19207A120

Final Rept on Potentially Reportable Deficiency 77-15.Design of Unit 1 Turbine Bldg Roof Will Withstand Seismic But Not Tornado Wind Loads. Roof Bracing Repair Drawings Have Been Developed and Issued for Const

ML19207A120
Person / Time
Site:	Grand Gulf
Issue date:	08/28/1978
From:	MISSISSIPPI POWER & LIGHT CO.
To:
Shared Package
ML19207A121	List: ML19207A120 ML19208D883
References
NUDOCS 7901050225
Download: ML19207A120 (2)

Text

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4 FINAL REPORT TURBINE BUILDING DESIGN POTENTIALLY REPORTABLE DEFICIENCY No. 77/15 1.

Description of the Deficiency 1 Turbine Building roof was checked and found The design of the Unit withstand tornado wind loads.

to be defici nt in that the roof will not it will, however, withstand Detailed analysis of the roof indicates that The seismic design is dependent upon structural rein-seismic loads. This design would f orcement f rom both the Q-decki..g and roof bracing.

l the be acceptably weakened if a tornado were to remove and sweep away Q-decking and roofing.

11. Safety Implications _

design does The analysis concluded that the existing turbine building nearby saf ety related (Category I) buildings would not not assure that This be adversely affected under design basis tornado vind loads.

h Grand Gulf PSAR, conclusion is contrary to the consitment stated in t e Based on this information, MP&L volume 10, Appendix R, page R3.3.1-1.

( )(1)(ii) on reported the deficiency to the NRC under 10CFR50.55 e December 14, 1977.

III. Corrective Action in Progress _ f the (a)

The detailed analysis of tornado effects on all portions o 31, 1978 and Unit 1 Turbine Building was co=pleted on January disclosed that only the roof bracitg had inadequate capacity.

I roof bracing repair drawings had been By March 15, 1978, Unit Drawings reflecting developed and issued for construction.

(line 11 frame I the strengthening of the floor beam connections i l forces at elevations 133' -0" and 166' -0") to resist the ax a 1032 3.yoLorogar

f from the tornado wind loads were issued for construction by May 15, 1978. Some additional but minor revisions on purlin connections in the Unit 1 Turbine Building are scheduled for completion during the first half of September 1978.

(b) The analysis of tornado wind loads ef fects on the Unit 2 Turbine Building is presently in progress. Unit 2 structural steel drawings issued f or construction have been revised and re-issued where analysis is complete or are "on hold" where analysis is still in progress. These "on hold" drawings will be revised j

and reissued for construction consistent with the Unit 2 Turbine Building Engineering schedule.

IV. Corrective Action Taken Details of the corrective cetion taken for this deficiency and documentation regarding action taken to prevent recurrence vill be documented in Bechtel's Management Corrective Action Report (MCAR)

GGNS No. 37. Upon completion of all corrective action the subject MCAR will be available for NRC review.

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