NRC-92-0089, Advises That Util Planning to Implement Design Mod to High Pressure Turbine Control Valves to Assure That Steam Flow Capacity,W/Adequate Throttle Margin,Exists Coincident W/ Original Design Capacity of 105% Steam Flow

Advises That Util Planning to Implement Design Mod to High Pressure Turbine Control Valves to Assure That Steam Flow Capacity,W/Adequate Throttle Margin,Exists Coincident W/ Original Design Capacity of 105% Steam Flow

ML20113H585
Person / Time
Site:	Fermi
Issue date:	07/31/1992
From:	Gipson D DETROIT EDISON CO.
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
CON-NRC-92-0089, CON-NRC-92-89 TAC-M82102, NUDOCS 9208050060
Download: ML20113H585 (2)

Text

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Detro.dison E- t mwmo,,cse+or nome July 31,1992 NRC-92-0089 U. S. Nuclear Regulatory Commission Attn.: Document Control Desk Washington, D. C. 20555

References:

1) Fermi 2 NRC Docket No. 50-341 NRC License No. NPF-43

2) Detroit Edison Letter, NRC-91-0102, " Proposed License Amendment - Uprated Power Operation", dated September 24, 1991.

3) Detroit Edison Letter, NRC-92-0048. " Revision to Proposed License Amendment for Uprated Power Operation and to the Fetmi 2 Power Uprate Safety Analysis (TAC No, M82102)", dated April 30, 1992.

Subject:

Modification to the High Pressure Turbine Control Valves The purpose of this letter is to inform the NRC Staf f that Detroit Edison is . planning to implement a design modification to the high pressure turbine control valves (TCV). The modification is being implemented to provide assurance that steam flow capacity with adequate throttle margin exists consistent with the original design capacity of 105% steam flow and 103% steam pressure when operating at uprated conditions. This modification, therefore, restores the original design capacity under which power uprate was evaluated.

The modification is minor in scope. The existing TCV spindles, valve heads, and valve stems will be retained; 'only the existing sleeves will be replaced with new shorter sleeves that will allow increased steam flow as the valves-are opened. This modification was discussed with the NRC Staf f during the May 1992 NRC/ Detroit Edison Management Meeting held at Fermi 2.

' Prior to initial plant startup, the high pressure' turbine control valves were modified to correct a flow vibration problem experienced at a-similar unit. The design change _ developed by the turbine manuf acturer was also intended to maintain the original steam flow capacity for the TCVs. While 100% flow capability was confirmed, data was not tsken with the valves wide open to determine maximum flow capacity. Recent plant operation indicated that the TCV flow capacity may be less than the-original design capacity. To ensure that the TCV steam flow capacity is 9208050060 920731 PDR ADOCK 05000341' U

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e i USNRC July 31,1992 NRC-92-0089 Page 2 consistent with the original design, the niodification to the TGVs, ao previously deceribed, will be irrplemented during RE03 f or all four valves based on parts availability and adequate recources to accomplish the change.

Detroit Edison is inplementing the modification to restore the original design capacity of the TCVc under the provisions of 10CFR50.59. Because the modification does not involve a Technical Specification change and as being made to rectore the basis under which power uprate was originally _

evaluated, the change does not f all within the ocepe of the license amendment and its associated no significant hazards analysis. Therefore.

Detroit Edison believec that the modification t.hould not affeet the NRC Staf f review and approval of the power uprate license an>endn:ent (Referenceo 2 and 3).

Please contact Mr. Terry L. Riley, Supervisor Nuclear Licensing, at (313) 586-1684, should you require any additional inf ormation on this matter, r

Sincerely.

cc T. G. Colburn -

A. B. Davis M. P. Phillips S. Stasek R. Stransky i

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