ML20196C025

SER Accepting Clarification on Calibration Tolerances on Trip Setpoints for Catawba Nuclear Station

ML20196C025
Person / Time
Site:	Catawba
Issue date:	11/27/1998
From:	NRC (Affiliation Not Assigned)
To:
Shared Package
ML20196C022	List: ML20196C017 ML20196C025
References
NUDOCS 9812010236
Download: ML20196C025 (3)

Text

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NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20066 0001

'+9 ***** ,o SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION CLARIFICATION ON CAllBRATION TOLERANCES ON TRIP SETPOINTS DUKE ENERGY CORPORATION CATAWBA NUCLEAR STATION. UNITS 1 AND 2 DOCKET NOS. 50-413 AND 50-414

1.0 INTRODUCTION

By letter dated August 20,1998, Duke Energy Corporation (DEC) requested clarification of the staff's position on DEC's current practice of setting trip setpoints within a two-sided tolerance band ( ) of the Technical Specification (TS) limit during instrument calibration. The Catawba Nuclear Station, Units 1 and 2 (Catawba), TS Tables 2.2-1* and 3.3-4* for the Reactor Trip System (RTS) and the Engineered Safety Feature Actuation System (ESFAS) specify limits that require that the trip setpoints be set "5" (less than or equal to) or "2" (greater than or equal to) the numerical values specified in the Trip Setpoint column. In a letter dated September 30, 1998, DEC stated that its existing setpoint calculations account for the two-sided calibration tolerance on trip setpoints.

2.0 EVALUATION DEC stated that the Catawba Engineering Directive Manual and the " Westinghouse Reactor Protection System / Engineered Safety Features Actuation Systems Setpoint Methodology" indicated that as long as the limiting safety system setting value was not exceeded, it was within assumptions of the calibration methodology for safety-related instrument as-found trip setpoints to be exceeded by the instrument calibration setting tolerances. Thus, even though the current trip setpoint calibration methodology includes limits that are different from the trip l setpoint setting set forth in the TS, DEC's setpoint calculations have accounted for the difference. The staff, therefore, determines that DEC's practice does not lead to any safety concern.

• On September 30,1998, the NRC staff issued Amendment Nos.173 and 165 to revise the TS of Catawba Nuclear Station, Units 1 and 2, respectively, to the " Standard Technical Specifications for Westinghouse Plants," NUREG-1431. As a result, the specifications of these tables have been largely relocated to Tables 3.3.1-1 and 3.3.2-1.

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The staff recognizes that the wording " TRIP SETPOINT" together with the inequality signs in 4

the TS tables has lead to confusion. Specifically, the combination states that the numerical l value specified for a given FUNCTION constitutes the absolute maximum or minimum trip setpoint allowed. This usage is unjustifiably more conservative than the staff-approved Westinghouse setpoint methodology, and was not so intended when the improved TS was issued by the staff. In fact, the staff recently resolved this problem in the Vogtle TS (see page 3.3-30 of the Vogtle TS attached) by changing " TRIP SETPOINT" to " NOMINAL TRIP i SETPOINT," by eliminating all inequality signs in that column, and by adding a footnote (i) to clarify operability of a channel. The current Catawba TS may be problematic when literal <

compliance is considered. Such literal compliance, however, does not contribute to additional l safety since DEC's current practice ensures that the systems and components would not ,

operate outside safety limits, as stated in the previous paragraph. For the long-term solution to '

the compliance concern, the licensee may evaluate the applicability of the Vogtle TS to Catawba.

3.0 CONCLUSION

The staff has reviewed the licensee's justification for using a two-sided tolerance on the trip setpoint settings for RTS and ESFAS TS instrumentation and, based on that review, the staff concludes that the current calibration methodology poses no safety concern. Nevertheless, the licensee's current calibration methodology may be problematic in literal compliance with the TS; the licensee should consider long-term solutions.

Attachment:

Vogtle TS page 3.3-30 Principal Contributors: Sabinoy Mazumdar Carl Schulten Peter Tam Date: November 27,1998

ESFAS Instrumentation 3.3.2 Table 3,3.2 1 (pege 1 of 7)

Engineered safsty Feature Actuation System Instrumentation APPLICABLE HCCES OR OTHER l

SPECIFIED NOMINAL REQUIRED SURVEILLANCE FUNCTION ALLOWA8LE TRIP CONDITIONS CHANNELS CONDITIONS REQUIREMENTS VALUE SETPOINTUI l

1. Safetyinjection

a. Manuet Initiation 1,2,3,4 2 5 st 3.3.2.6 NA NA

b. Automatic 1,2,3,4 2 Actuation Logic C SR 3.3.2.2 NA NA and Actuation st 3.3.2.3 Relays SR 3.3.2.5

c. Containment 1,2,3 3 Pressure-High 1 0 st 3.3.2.1 s 4.4 pelg 3.8 pets l st 3.3.2.4 SR 3.3.2.7 SR 3.3.2.8

d. Pressuriser 1,2,3C *) 4 D SR 3.3.2.1 2 1856 psig 1870 pels l Pressure - Low SR 3.3.2.4 SR 3.3.2.7 st 3.3.2.8

e. Steam Line 1,2,3(8I 3 per Pressure Low D st 3.3.2.1 2 570(b) $g5(b) g steen SR 3.3.2.4 psis pela line SR 3.3.2.7 SR 3.3.2.8 (continued)

(a) Above the P 11 (Pressuriger Pressure) Interlock.

(b) Time constants used in the lead /las controtter are t, t 50 seconds and t, s 5 seconds.

(1) A channet is OPERABLE with an actual Trip Setpoint value outalde its calibration tolerance bond provided the Trip setpoint value is conservative with respect to its associated Allowable Value and the channel is re-adjusted to within the established calibration tolerance band of the Wentnal Trip setpoint. A Trip setpoint may be set more conservative than the Weninal Trip Setpoint as necessary in response to plant conditions.

l Yogtle Units I and 2 3.3-30 Amendnunt No.101(Unit 1)

Amendment No. 79(Unit 2)

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