ML20245E809

Safety Evaluation Supporting Amend 154 to License NPF-1

ML20245E809
Person / Time
Site:	Trojan File:Portland General Electric icon.png
Issue date:	06/20/1989
From:	Office of Nuclear Reactor Regulation
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ML20245E641	List: ML20245E637 ML20245E649 ML20245E652 ML20245E809
References
NUDOCS 8906270458
Download: ML20245E809 (4)

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/ UNITED STATES

j. ,g. NUCLEAR REGULATORY COMMISSION WASHINGTON, D. C. 20555

.e SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO.154 TO FACILITY OPERATING LICENSE NO. NPF-1 PORTLAND GENERAL ELECTRIC COMPANY l l'

THE CITY OF EUGENE, OREGON PACIFIC POWER AND LIGHT COMPANY TROJAN NUCLEAR PLANT j DOCKET NO. 50-344 l l

1.0 INTRODUCTION

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By letter dated September 2, 1988, Portland General Electric Company (PGE, the licensee) proposed a modification at Trojan Nuclear Plant that would result in an increase of up to 3 percent in lateral shear force for the Control Building walls. By a licensee change application (LCA 174)  ;

dated February 10, 1989, PGE proposed a net 3 sercent increase in the t allowed lateral shear forces on any story of t1e Control-Auxiliary-Fuel Building Complex (the Complex). The staff reviewed the PGE proposal and raised some technical concerns. These were discussed during a telephone conference of February 8, 1989, and were addressed in a licensee submittal dated February 15, 1989.

2.0 EVALUATION t Section 5.7.2.2 of the Trojan Technical Specifications states the require-ments controlling modification to Category I structures for Trojan.

Specifically, Item (a) of Section 5.7.2.2 states one of the conditions barring structural modification to Categnry I structure as, "1 percent increase in lateral shear forces on any story of the Compicx". PGE proposed a modification to the ventilation system in the Control Building that would result in an increase of lateral shear fortes in excess of one percent for the walls supporting the roof of the building. Also, Section 5.7.2.2 allows an increase in equipment weight not to exceed 10 percent on a per story, per building basis. However, PGE cannot utilize this provision to accommodate the needed increase in equipment weight because there was originally minimal equipment weight contributing to the Control Building roof loads.

PGE has determined that current and future modifications would require consideration for a 3 percent increase in lateral shear forces for the walls in the Control Building, and that the value of increase in lateral shear force is directly proportional to the increase in weight.

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1 The licensee originally analyzed the structure utilizing the STARDYNE finite element computer code as documented in their report PGE-1020,

" Report on the Design Modification for Trojan Control Building, July 14, 1978." For the reevaluation, the licensee has increased all of the weights used in the original STARDYNE Code by 3 percent and has evaluated ,

the effects of these weight increases on the shear wall capacity-to-force i ratios, floor response spectra, and interstructure displacements. The ,

results of the reevaluation based on an effective increase by 3 percent of l all shear forces indicate that all of the structural components remain well within their allowable stresses and their load capacities are greater than their load demands.

The licensee has justified tne above assumed linear relationship between the weight increase and the equival.ent increase in lateral shear forces 1

based on an argument that the story shear forces are essentially a l function of the spectral acceleration and weight of the structure. The i licensee further states that the spectral acceleration depends on the period j (frequency) of the modes of vibration, and the first and second modes of  ;

vibration control the overall structural responses in the north-south and j east-west directions. A 3 percent increase in weight will result in a 1.5  !

percent increase in the value of the fundamental period of the structure.

A check on the change in ground response spectra based on the 1.5 percent change in fundamental period of the structure (FSAR Figure 3.7-1) resulted j in nondetectable differences. Therefore, the licensee concluded that a direct relationship between the weight and the lateral shear forces is justifiable. The staff finds the above justification reasonable and convincing.

The licensee has determined that the controlling locations for the old  !

and new evaluations of shear wall capacity-to-force ratios, when consider-ing the Operating Basis Earthquake (0BE) load combination, include the following wall components:

a. Walls No. 6 and 8 between Elevation 45 and 61.

b. Wall R at Elevation 93 along column line 46.

c. Wall N between Elevations 61 and 93 and along column line 46.

Items (c) and (d) to Section 5.7.2.2 of the Trojan Technical Specifications identify limitations in displacements between the Control and Turbine Buildings. The licensee reported that the above limits are not exceeded by the pertinent relative displacements determined, based on the assumed increase in allowable lateral shear fcrces.

During its review, the staff requested the licensee to address three issues: (a) The effects of selecting a larger change in weight than currently identified and its effects on the fundamental frequency of the j structure, (b) the identification of the specific structural components

l that would be structurally modified to provide the ventilation requirements, and (c) an explanation of why the results were based on the OBE load combina- l tions rather then the SSE load combinations. PGE addressed these issues in  !

their submittal of February 15, 1989, to the satisfaction of the staff. The licensee's identification of (from 1 percent to 3 percent) and planned current the very low and effectfuture of theload changes 3 percent weight change on the period of the structure and spectral accelerations i resolved the first issue. Also, the licensee has stated that no alteration  :

of major structural members will take place and that planned attachments to  !

structural members will follow the structural design requirements stated '

in Trojan's FSAR Section 3.8, " Design of Seismic Category I Structures." l This licensee commitment will be properly documented in a future FSAR. '

Finally, in responding to the last staff concern, the licensee stated  ;

that the technical specifications original requirements limiting the lateral shear force increase to one percent resulted from an evaluation utilizing the OBE load combinations. The evaluation that considered the Safe Shutdown Earthquake (SSE) load combinations satisfied the capacity requirements stated in the Trojan FSAR. Since the licensee has demonstrated that the margins for the SSE are larger than those for the OBE, the staff considers the third concern resolved. '

Based on the foregoing considerations, the staff concludes that the effect of a 3 percent increase in weight to the Control Building roof could be reasonably accounted for by addition of 3 percent weight at all mass points in the STARDYNE Computer Code model. The results of the ,

evaluation of the proposed niodification have indicated that: (a) there is minimal effect on the seismic response characteristics of the structure, (b) there is essentially no change on the overall structural load demand for each structural component, and (c) the interstructural relative dis-la p(c) and cements (d) ofremain small Section to comply 5.7.2.2 of the with the related Trojan's T>chnicalrequirements of items Specifications.

Based on the evaluation of the licensee submittals, the supplementary information provided by the licensee and telephone discussions with the licensee which served to clarify some issues associated with this proposed activity, the staff concludes that the licensee's structural analyses of the applicable components are in compliance with the acceptance criteria set forth in the FSAR and consistent with current licensing practice.

Therefore, the licensee's proposed modification to the Control Building is acceptable, and the proposed technical specification change is acceptable.

3.0 CONTACT WITH STATE OFFICIAL The NRC staff has notified the Oregon Department of Energy of the proposed issuance of this amendment along with the proposed determination of no significant hazards consideration. No comments were received.

4.0 ENVIRONMENTAL CONSIDERATION

Pursuant to 10 CFR Part 51.21,(51.31 and 51.35, an environmental 54 FR 24432) in assessment has been published

, June 7, 1989. Accordingly, based upon the environmental assessment, the Commission has determined that the issuance of the amendments will not have a significant effect on the quality of the human environment.

5.0 CONCLUSION

We have concluded, based on the considerations discussed above, that (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations,and(3)theissuanceoftheamendmentwillnotbeinimical to the common defense and security or to the health and safety of the public.

PRINCIPAL CONTRIBUTORS: Frank Rinald' Roby Bevan Dated: June 20, 1989 i

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