ML20235L942

Application for Amend to License NPF-1,consisting of License Change Application 174.Amend Revises Tech Specs to Allow Mods to Control Auxiliary Fuel Bldg Complex Resulting in Increase in Lateral Shear Forces of Any Story

ML20235L942
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	02/10/1989
From:	Cockfield D PORTLAND GENERAL ELECTRIC CO.
To:
Shared Package
ML20235L932	List: ML20235L928 ML20235L942 ML20235L944
References
NUDOCS 8902280053
Download: ML20235L942 (5)

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PORTLAND CENERAL ' ELECTRIC COMPANY EUGENE WATER & ELECTRIC BOARD AND PACIFIC POWER & LIGHT COMPANY Operating License NPF-1 Docket. 50-344

- License Change Application 174 i

This License Change Application requests modifications to Operating License NPF-1 for the Trojan Nuclear Plant to revise the Trojan Technical Specifications to allow modifications to the Control-Auxiliary-Fuel Building Complex which result in up to a net three percent increase in  !

lateral shear forces on any story.

PORTLAND GENERAL ELECTRIC COMPANY By L

D. W. Cockf d Vice Pres,1 ent Nuclear i

Subscribed and sworn to before me this 10th day of February 1989.

J3 dr_-- ~

i H Notary Public of Oregon My Commission Expires: Mr.d 0

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I h

i 8902280053 890210 i PDR ADOCK 05000344 j P PDC

Attachment A LCA 174

. Page 1 of 4 DESCRIPTION OF CHANGE Trojan Technical Specification (TTS) 5.7.2 provides restrictions on the design provisions of the Control-Auxiliary-Fuel Building Complex (here-after referred to as the " Complex"). One of these restrictions, as stated in TTS 5.7.2.2.a. is that no modifications watch will result in a not 1 percent increase in lateral shear forces on any story of the Complex shall be performed without prior approval by the Nuclear Regulatory Commission.

This change revises TTS 5.7.2.2.a to allow modifications to the Complex which result in up to a not 3 percent increase in lateral shear forces on any story.

REASON FOR CHANGE TTS 5.7.2 was added to the TTS in TTS Amendment 47 (July 1980). Since that time, weight additions to each story of the complex have been tracked to ensure that TTS 5.7.2 is satisfied. These weight additions have been due to plant modifications over the years.

Recognizing that weight additions were resulting in approaching the 1 percent limit for additional lateral shear forces cited in TTS 5.7.2.2.a, a revised analysis was performed of the Complex using a 3 percent limit for additional lateral shear forces. This revised analysis was submitted to the NRC in Reference 1 as a request to allow excceding the 1 percent limit. The purpose of this License Change Application (I.CA) is to formally request that the TTS be changed to allow a 3 percent limit for additional lateral shear forces consistent with Reference 1.

SIGNIFICANT HAZARDS CONSIDERATION DETERMINATION The proposed change does not involve a significant hazard for the reasons discussed below:

1. This change does not involve a significant increase in the probability or consequences of an accident previously evaluated.

The addition of weight to the Complex is of concern for its effect on: (a) shear force in the walls, (b) interstructure displacement, and (c) floor response spectra. Each of these effects was analyzed in detail in Reference 1 and is summarized below.

Shear Wall Evaluation The vertical load carrying system for the Complex consists of rein-forced concrete slabs, a vertical load carrying steel space frame, and masonry, concrete, or composite masonry-concrete walls. All of the walls where they are developed with the slabs or steel frame

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l I Attachment A

• LCA 174 page 2 of 4 l

l are considered to be shear walls to resist lateral loads. The total weight, including the 3 percent weight addition, remains well within the capacity of all components of the vertical load carrying system. '

i A seismic spectral analysis of the Complex was performed using the STARDYNE finite element computer code. When performing a seismic spectral analysis of a structure, the analytically determined shear forces are essentially a function of the spectral acceleration and the weight of the structure. The spectral acceleration, in turn, depends upon the period (frequency) of the modes of vibration. A 3 percent increase in the weight would' result in a 1.5 percent increase in the period of the structure. The dominant periods of the i Complex in the north-south and east-west directions, based on the  !

original STARDYNE analycos, were compared with the periods corres-ponding to the 3 percent weight increase. The results showed that the change in spectral acceleration is negligible.

The other factor influencing the shear forces is the building weight. Its effect was considered directly through the 3 percent increase in weight, since the shear forces vary linearly with the weight. New shear forces for the 3 percent increase in the weight of the complex were obtained by increasing the original STARDYNE shear forces by 3 percent.

Comparison of the increased shear wall forces and previously calcu-lated shear wall capacities was performed. With the exception of four locations, the capacities of the shear walls exceed the increased shear forces. The conditions where shear wall forces exceed the shear wall capacities existed, even under the 1 percent limit and were previously documented in pCE-1020, " Report on Design Modifications for the Trojan Control Building", January 1979, and PGE to NRC letter of February 13, 1980.

Two of these locations involve minor shear walls which will undergo inelastic deformation, and redistribution of loads will occur to adjacent walls. The amount of redistributed load, which is approxi-mately 1 percent of the total base shear, does not exceed the reserve capacities which exist in the adjacent major shear walls.

At the remaining two locations, a small amount of tension will develop to mobilize the excess shear resistance from below. In both cases, the total vertical capacity along the entire vertical plane is more than the vertical shear force demand. ,

Interstructure Displacement With a 3 percent increase in the weight of the Compicx, the displacement of the Control Building would increase linearly by 3 percent (the Control, Auxiliary, and Fuel Buildings are connected by diaphragms). The maximum increase in displacement was calculated  ;

to be 0.6 percent, well within the 5 percent limit of TTS 5.7.2.2.c.  !

Attachment A

- LCA 174 page 3 of 4 Floor Response Spectra Floor response spectra used in seismic analysis of individuni structural components, piping, equipment, and mechanical a-d electrical components located in the Complex are generated from the analytical models used for the structural analysis of the complex.

An artificial time history record is synthesized which will produce a spectrum enveloping the design ground response spectrum. This time history is then used as input into the analytical models to generate responso time history records at selected points on each floor elevation. Floor response spectra are then generated from the floor response time histories at each selected point. These spectra from several locations are first combined for each floor and the resulting envolcpe spectra are then broadened, based upon the frequency of each peak. This spectra broadening is performed to account for possibic frequency variations that may result from uncertainties in material proporties, structural mass and stiffness characteristics, and ,

seismic analysis techniques. This spproach yields floor response  !

spectra for subsequent use in analysis and design which have a substantial amount of conservatism.

A uniform 3 percent increaso in weight would represent an approximate 1.5 percent increase in response periods, or decrease in the response frequencies of the Complex. Because of the spectra broadening, a frequency shift of this small magnitude would have no noticeable effect on the floor response spectra curves.

The results of the reanalysis of the Complex show that the proposed change will have no adverse effects on shear forces, interstructure  !

displacement, or floor. response spectra. Since the Complex response following a design basis seismic event will not change significantly from that previously analyzed, this change does not involve a significant increase in the probabil.ity or consequences of an accident previously evaluated.

2. This change does not create the possibility of a new or different kind of accident from any accident previously evaluated.

The proposed change relates to the ability of the Complex to respond to a design basis scismic event. A scismic event is a design basis event previously evaluated for Trojan. The reanalysis of the Complex using a 3 percent increase in lateral shear forces, as detailed in Reference 1, determined that the Complex seismic response character-istics were essentially unchanged. Therefore, this change does not create the possibility of a new or different kind of accident from any accident previously evaluated.

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Attachment A

- LCA 174 Page 4 of 4

3. This change does not involve a significant reduction in a margin of safety.

Under the present TTS limit of 1 percent for additional shear forces, the capacity of the shear walls exceeds shear forces with four exceptions. With the proposed TTS limit of 3 percent for additional shear forces, the capacity of the shear wad _s exceeds shear forces with the same four exceptions. As previously discussed and detailed  !

in Reference 1, the minor shear walls will undergo inelastic defor- l mation, and redistribution of forces will occur in adjacent major shear walls with adequate capacity remaining. For the major shear wall., the total vertical capacity along the entire vertical plane will still exceed tho vertical shear force demand. The ultimate capacity of the major shear walls of the Complex remains greater than the loads imposed by the design basis earthquake. Therefore, this change does not involve a significant reduction in a margin of safety.

In the March 6, 1986 Federal Register, the NRC published a list of examples of amendments that are not likely to involve a significant hazards consideration. Example No. 6 from this list states:

"A change which either may result in some increasa to the probability or consequences of a previously analyzed accident or may reduce in some way a safety margin, but where the results of the change are clearly within all acceptable criteria with respect to the system or component specified in the Standard Review Plan, e.g., a change resulting from the epyli-cation of a small refinement of a previously used calculational model or design method."

This example applies to the change proposed herein.

SA'TY/ ENVIRONMENTAL EVALUATION Safety and environmental evaluations were performed as required by Title 10, Code of Federal Regulations,-Part 50 and the TTS. This review determined that the proposed changes do not create an unreviewed safety question, nor do they create an unreviewed environmental question.

SCHEDULE CONSIDERATION It is requested that the effective date of this amendment be the date of issuance by the NRC.

REFERENCE

1. PCE to NRC letter regarding Control Building structural analysis, September 2, 1988.

BLK/ maw 2820W.0289

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