ML18139A610

LER 80-009/01T-0:on 800718,Westinghouse LOCA ECCS Reanalysis Indicated Error in Fuel Clad Burst Model.Caused by Reduction in Clad Heatup Rate Which Shifts Fuel Clad Burst Curve & Results in Earlier Clad Burst.Limit Will Be Controlled

ML18139A610
Person / Time
Site:	Surry
Issue date:	07/31/1980
From:	Joshua Wilson VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
Shared Package
ML18139A609	List: ML18139A608 ML18139A610
References
LER-80-009-01T, LER-80-9-1T, NUDOCS 8008040118
Download: ML18139A610 (3)

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I Westinghouse LOCA-ECCS reanalysis indicates that a residual penalty of O .007 i=- FQ exists from the fuel rod burst model. The error in the fuel clad burst model was rep:rted 11-26-79 in Unit 1 LERNO. 79-032/0lT-0. As a result, the FQ Limit (T.S.3.12.~.l) must be reduced. This is reportable as per T.S. 6.6.2.a.8.

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0 I The* fuel clad burst error wa~ caused .by :a reduction in clad heatup rate which shifts the

}] !fuel clad burst curve and results in earlier clad burst. The FQ.lirnit will be TI _ladrninistratively controlled at 2.18 pending NRC evaluation of the Fuel Clad burst* model 3 jand possible LOCA-ECCS Reanalysis.

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ATTACHI-IENT 1

• SURRY POWER STATION DOCKET NO: 50-281 REPORT NO: 80-009 /0lT-0 EVENT DATE: 7-14-80 TITLE OF EVENT : FQ LIMIT RESTRICTION

1. Description of Event:

On November 9, 1979, VEPCO was notified of an unreviewed safety question by Westinghouse Electric Corporation. The unreviewed safety question concerned a potential non-conservative feature of the Westinghouse ECCS large break evaluatio~ model which could affect the peak clad temperature calculated for the tOCA. transient, specificly in the fuel clad burst model.

Westinghouse,in evaluating their fuel Clad Burst model,has recommended a conservative, interim limit 'Be 9-pplied--to* ~the. mode.1--pending *NRG approval of their new Fuel Clad Burst model.

Westinghouse analysis (with the interim** limits) of Surry Unit 1 indicated that sufficient margin existed in the FQ- limit, but for Surry Unit 2, there existed a ,_ residual penalty of O. 007 in Fq based on the present Fq "limit of 2*:.19. ' This event is reportable in accordance wit:h Technical Specification 6.6.2.a.8.

2. Prob ab le Consequences/Status of Redundant Sys terns-:

The Westinghouse evaluation revealed that heatup rates could be <25°F/second During the LOCA transient, the fuel clad burst curve establishes the time of clad burst and the post-burst conditions of the c.lad. The fu~l clad burst curve is dependent on the clad heatup rate prior to burst, and a reduction in clad heatup rate causes earlier cla~ burst, Since Surry Unit 2 has not operated since this event was reported, the health and safety of the general public have not been affected.

3. Cause The potential non-conservative feature of the Westinghouse large break ECCS evaluation utilized a model which uses a curve that represents fuel clad burst conditions for clad heatup rates of > 25°F /second .. The* fuel clad burst curve is dependent on the clad heatup rate prior to burst and a redu*ction in heatup rate causes earlier clad burst.' A shift in clad burst time can affect the peak clad temperature (PCT) calculated for the LOCA-transient.

4. Immediate Corrective Actions:

Since the current Surry LOCA-ECCS analyses exhibited heatup rates less than 25°F/sec., a specific reanalysis was performed to ascertain the effect on PCT for the Surry Unit 2 analysis. The Fq limit will be administratively restricted to 2.18 as an interim measure until NRC fuel +9d burst mpdeling co~c~rns_are r~ 9 o~ye9. ~lJ ijo~ ~hannel factor surveillance will be analyzed based *on this interim li:r.n.t.

5. Scheduled Corrective Action:

Once the Fuel Rod Burst model concerns are -resolved-, the model will be evaluated for Surry to determine if LOCA-ECCs analysis and possible Technical Specifications changes will be required. for present Fq limits.

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• Action Taken to Prevent Recurrence:

e No other action will be necessary to prevent recurrence.

7. Generic Implications This event was a Westinghouse identified generic item and was reported under LER No. 79-032/0lT-0 for Surry Unit 1 and 2.