TXX-6180, Final Deficiency Rept CP-86-17 Re Min Concrete Coverage of Reinforced Steel in Walls & Floors Required to Maintain 3 H Fire Rating.Initially Reported on 860321.Facility Design Complies W/Bldg Code.Item Not Reportable Per 10CFR50.55(e)

Final Deficiency Rept CP-86-17 Re Min Concrete Coverage of Reinforced Steel in Walls & Floors Required to Maintain 3 H Fire Rating.Initially Reported on 860321.Facility Design Complies W/Bldg Code.Item Not Reportable Per 10CFR50.55(e)

ML20212E178
Person / Time
Site:	Comanche Peak
Issue date:	12/23/1986
From:	Counsil W, Keeley G TEXAS UTILITIES ELECTRIC CO. (TU ELECTRIC)
To:	Johnson E NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV)
References
CP-86-17, TXX-6180, NUDOCS 8701050269
Download: ML20212E178 (2)

Text

Log # TXX-6180 File # 10110

. 909.5 TEXAS UTILITIES GENERATING COMPANY SKYWAY TOWER . 400190RT,6 OLIVE ErrREE"F. L.B. 88 DABAAS. TEXAS 75398 December 23, 1986

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Mr. Eric H. Johnson, Director l4l OEC 2 9126 t, Division of Reactor Safety and Projects 'g 'g i'

U. S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 1000 Arlington, Texas 76011

SUBJECT:

COMANCHE PEAK STEAM ELECTRIC STATION (CPSES)

DOCKET NOS. 50-445 AND 50-446 MINIMUM CONCRETE COVERAGE SDAR: CP-86-17 (FINAL REPORT)

Dear Mr. Johnson:

On March 21, 1986, we verbally notified your Mr. R. Hall of a deficiency concerning the minimum concrete coverage required for reinforcing steel in the walls and floors necessary to maintain a three-hour fire rating. Our last interim report was logged TXX-6111, dated November 24, 1986.

Our evaluation of the subject walls and floors indicated that postulated temperatures would not adversely affect the structural capacity of the reinforced concrete elements.

The FSAR (Section 9.5.1.5.2) requires that reinforced concrete fire walls, floors and ceilings comply with either Underwriters Laboratories Listed Designs, the Uniform Building Code (UBC), or be of a tested configuration in regard to minimum concrete cover for reinforcing steel. The CPSES fire rated walls and floors were designed to ACI 318-71, Section 7.14.1 which requires a 3/4 inch concrete cover over reinforcing steel. The following evaluation of UBC provisions has concluded that a 3/4 inch concrete cover is adequate for a~

3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> fire barrier. Neither the code nor the standards specifically address cover requirements for walls as they pertain to fire resistance.

UBC Chapter 43 (Table 43-A) requires a 1 inch concrete cover to attain a 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> rating for certain grades of concrete. The UBC Standards allow for an alternative i.ethod (Section 4302) to determine fire resistance. Section 43.908 establishes that the minimum thickness of cover over reinforcing steel in slabs should comply with Table No. 43-9-J which requires a 3/4 inch concrete cover for a 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> rating (restrained construction). For the purpose of the UBC Standards, an unrestrained condition is one in which the load-carrying element is free to expand and rotate at its supports. UBC Section 2607(h) does require a minimum concrete cover for reinforcing steel for corrosion protection which is the same cover requirement as ACI 318-71.

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TXX-6180 December 23, 1986 Page '2 UBC Table 43-A provides general requirements. The UBC also recognizes that the alternative requirements are equally acceptable and, at least in this particular case, may provide more specific requirements for the conditions of restrained /understrained elements, while Table 43-A does not make any such distinction.

TUGC0 received a clarification of UBC requirements in July 1986. UBC acknowledged that they did not specifically address cover requirements for walls insofar as fire considerations were concerned. They further stated that ACI ?.16 (ACI 216R-81, " Guide for Determining the Fire Endurance of Concrete Elements") indicated that fire endurance of concrete walls is generally governed by heat transmission through the wall, and not by structural conditions. The letter stated that the cover required by Section 2607 (h) was adequate, meaning that 3/4 inch cover was adequate for a 3 hour3.472222e-5 days <br />8.333333e-4 hours <br />4.960317e-6 weeks <br />1.1415e-6 months <br /> rated barrier.

We have concluded that the CPSES design is in compliance with the UBC. This issue is not reportable under the provisions of 10CFR50.55(e). Records supporting this conclusion are available for your inspectors to review at the CPSES project site.

Very truly yours, h fM'sY W. G. Counsil By: - '

6 G. S. Keeley Manager, Nuclear censing JCH/gj c - Region IV (0 + 1 copy)

Director, Inspection and Enforcement (15 copies)

U. S. Nuclear Regulatory Commission Washington, D. C. 20555 1

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