ML20054E655

Forwards Complete Responses to NRC Questions Re Util 820226 General Design Criteria 17 Submittal.Mods Will Be Completed by Second Refueling Outage After 820901

ML20054E655
Person / Time
Site:	North Anna
Issue date:	06/04/1982
From:	Leasburg R VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	Clark R, Harold Denton Office of Nuclear Reactor Regulation
References
316, NUDOCS 8206140035
Download: ML20054E655 (5)

Text

o VINGINIA ELECTRIC A lD Powen CoxPANY RicnMono, VistointA 20261

} H. II. Lua ss u no vice Pansseser h etnam Oramarson.

June 4, 1982 Mr. Itarold R. Denton, Director Serial No. 316 Ofx' ice of Nuclear Reactor Regulation PSE&CS/WCS/KSB:cdk Attn: Mr. Robert A. Clark, Chief Docket Nos. 50-338 Operating Reactors Branch No. 3 50-339 Division of Licensing U. S. Nuclear Regulatory Commission License Nos. -NPF-4 Washington, D. C. 20555 NPF-7 Gentlemen:

4 GENERAL DESIGN CRITERIA 17 ANALYSIS NORTH AhTA UNIT NOS. 1 AND 2 The purpose of this letter is to complete our responses to your questions concerning our General Design Criteria 17 submittal, Serial No. 076, dated February 26, 1982. The responses provided are those which were outstanding in our May 20, 1982 letter, Serial No. 233. The questions and responses are provided in Attachment I entitled " General Design Criteria 17 - Response to NRC Questions".

In review of our schedule submitted in our February 26, 1982 letter, we l

believe we should revise our targeted completion dates to provide for the possibility of an unanticipated response from the valve manufacturer regarding rerating motor operated valves at North Anna. A more realistic construction schedule in view of currently scheduled projects will be to complete all modifications by the second refueling o2tage of each unit after September 1, 1982.

Yours very truly, b' t > w R. H. Leasburg a o o/

KSB:cdk:2448A Attachment cc: Mr. J. P. O'Reilly Regional Administrator Office of Inspection and Enforcement Region II 92%MM3 gg PDR ADOCK 05000338 P

PDR

, s ATTACIMENT I GENERAL DESIGN CRITERIA 17 RESPONSE '10 NRC QUESTIONS NORTH ANNA UNIT NOS. 1 AND 2 i

NRC Question E "What will be the setpoints for your overvoltage alarms?

Will there be coincidence logic on each bus? Will they be designed to IEEE Std. 279?"

l Vepco Response Preliminary design indicates the overvoltage setpoints will be 4400 V on the 4160 V emergency buses and 506 V on the 480 V emergency buses. 'Ihese settings are based on 110% of the nominal voltage retings for the IE motors.

Coincident logic will not be used on each bus. One relay will be installed on each 480 V bus, with an overvoltage setpoint as indicated above. A relay from the existing loss of voltage / degraded voltage protection will be used to alarm overvoltage on its respective 4 KV bus. This design provides three overvoltage monitors per protective train (H i

or J), which is sufficient protection. Upon receipt of an overvoltage alarm, manual action will be taken within 15 minutes to alleviate the overvoltage condition.

Additionally, coincident logic is not required because manual, rather than automatic, action results from the e

cdk/2448A/3 }

r-6 . -s relay operation. Since the operator will check the bus voltage after receipt of an alarm, no spurious actions (e. g. , separation from the offsite source) will occur.

The modification will not be in strict compliance with IEEE 279, although it will meet the intent of IEEE 279. With overvoltage monitoring of 3 buses per protective train, the single failure criteria of IEEE 279 is me,t and protective action at the system level will be maintained.

Additionally, a channel may be removed from service without initiating protective action at the systems level. A channel may be tested with the unit operating at 100% power.

NRC Question 7 "What is the typical feeder voltage drop (both steady-state and transient conditions) from a 480 V bus to

a. a MCC contactor

b. a nonHMOV load, and

c. a MOV load And from a 480 V MCC to:

a. a non-MOV load, and

b. a MOV load?"

Vepco Regponse The voltage drops requested are listed in the table below, along with additional voltage drops which are included to provide a more complete view of our system.

cdk/2448A/4 s .c

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. . ~ . . . . . .

. . D TYPICAL FEEDER VOLTAGE DROPS 480 V SYSTEM STEADY STATE TRANSIENT I. From a 480 V Ioad Center Bus To A) An MCC Contactor Coil 4V** 9V**

B) A non-MOV Ioad (Fed From a Ioad Center) 13V 23V C) A non-MOV Ioad (Fed From an MCC) 16V 20V D) An MOV Icad

• 22V II. From a 480 V MCC Bus To:

A) A non-MOV Ioad 10V 8V B) An MOV Ioad

• 10V C) An MCC Contactor Coil 2V** 6V**

• An MOV operates for a short time (e.g. , 30 seconds) only; therefore, a steady state voltage drop was not calculated.

• • These voltages are referenced to the 120 V system.

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.. 6 NRC Question 9 "What is the current schedule for the review being conducted by the MOV and valve manufacturers?"

Vepco Response Staggered receipt of information from the valve manufacturer is expected over the next two months. Review by the MOV manufacturers is ongoing and will continue as additional information is supplied by Vepco and/or the valve manufacturer. Vepco is committed to the rurating and/or replacement of the MOV's identified in our analysis.

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