ML20198A027

Responds to NRC 860219 Questions Re Bldg 10 & Walkover Structure.Walkover Structure & Bldg 10 Designed Such That Structural Elements Will Not Impact on Adjacent Bldgs During Seismic Event

ML20198A027
Person / Time
Site:	Fort Saint Vrain
Issue date:	05/12/1986
From:	Warembourg D PUBLIC SERVICE CO. OF COLORADO
To:	Berkow H Office of Nuclear Reactor Regulation
References
P-86240, TAC-55287, NUDOCS 8605200306
Download: ML20198A027 (2)

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p OPublic Service-Company of Colorado 2420 W. 26th Avenue, Suite 1000, Denver, Colorado 80211 May 12, 1986 Fort St. Vrain Unit No. 1 P-86240 Director of Nuclear Reactor Regulation U.S. Nuclear Regulatory Commission Washington, D.C.

20555 Attn: Mr. H.N. Berkow, Director Standardization and Special Projects Directorate Docket No. 50-267

SUBJECT:

Structural Evaluation of Fort St. Vrain Building 10 and Walkover Structure

REFERENCE:

1) NRC Letter Berkow to Walker, dated 2/19/86 (G-86087)

Dear Mr. Berkow:

This letter is in response to NRC questions, regarding Building 10 and Walkover Structure at Fort St. Vrain, as indicated in the referenced letter.

These questions and PSC's response are listed below.

ITEM 1 Clarify how the largest computed absolute differential displacement of 0.81 inches in the east-west direction was determined.

PSC RESPONSE The maximum east-west displacement of the walkover structure, resulting from design basis earthquake (DBE) input ground motion, is calculated to be 0.60 inches.

The maximum east-west DBE displacement of the Turbine Reactor Building, at elevations of

concern, is calculated to be 0.10 inches. The maximum east-west displacement of Building 10, resulting from DBE seismic loading, is 0.21 inches.

go y8 8605200306 860512 PDR ADOCK 05000267 P

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P-86240 May 12, 1986 Therefore, the maximum absolute differential displacement between two adjacent structures will occur between the Walkover Structure and Building 10 and is determined as follows:

MAX. ABSOLUTE DISPLACEMENT = 0.60 in. + 0.21 in. = 0.81 in.

ITEM 2 Address the apparent impact potential between Building 10, Turbine Reactor Building, and Walkover Structure.

ECdESPONSE All structural elements of the three adjacent buildings are separated by a minimum distance of 1 inch.

This provides adequate clearance to prevent impact resulting from the maximum seismic displacement of 0.81 inch discussed in ITEM 1.

Although the checkered plate located at intermediate floors in the Walkover Structure is separated by 1/4" from adjacent structures, it is not considered a structural element but rather an architectural finish.

Calculations are available in our office which show that the checkered plate and/or attachment bolts would fail prior to inflicting damage on the adjacent buildings during a seismic event.

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As indicated in the discussion of the above two items, the Walkover Structure and Building 10 have been designed such that structural elements will not impact on adjacent buildings during a seismic event.

I If you have any questions, please contact Mr. M.H. Holmes at (303) 480-6960.

Very truly yours, d) W Wwdx D. W. Warembourg, Ma er Nuclear Engineering Division DWW/MM:bt

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