ML19209A426

Forwards Response to IE Bulletin 79-21, Temp Effects on Level Measurements. Describes Sys Used to Initiate Safety Actions or Provide post-accident Info

ML19209A426
Person / Time
Site:	North Anna
Issue date:	09/14/1979
From:	Stallings C VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	James O'Reilly NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II)
References
678-081379, 678-81379, NUDOCS 7910030842
Download: ML19209A426 (3)

Text

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. Il nio ; g g September 14, 1979 Mr. James P. O'Reilly, Director Serial No. 678/081379 Office of Inspection and Enforcement P0/FHT:baw U. S. Nuclear Regulatory Com=ission Docket Nos. 50-338 Region II 50-339 101 Marietta Street, Suite 3100 License Nos. NPF-4 Atlanta, Georgia 30303 CPPR-78

Subject:

IE Bulletin 79-21 North Anna Power Station Units 1 and 2

Dear Mr. O'Reilly:

We have reviewed the subject bulletin, " Temperature Effects on Level Measurements",

and herewith forward the attached response for North Anna Power Station Units 1 and 2.

Very truly yours, W'Nf C. M. Stallings Vice President-Power Supply and Production Operations cc: Director Office of Inspection and Enforcement Division of Reactor Operations Inspection Washington, D. C. 20555 1086 159 7910080 # 9 ~

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• IE BULLETIN 79-21 NORTH ANNA POWER STATION UNITS 1 AND 2 In response to IE Bulletin 79-21, the following liquid ilevelormeasuring are systems within the containment are used to initiate safety Also actare included ons used to provide post-accident monitoring information.

descriptions of the systems and the effect upon those systems,of a high energy line break inside the containment.

tive actions for these systems are included.

1.

The Steam Generator (S/G) Level provides a reactor trip during a major secondary line break accident. S/G 1evel is also used to monitor i

the heat transfer capability of the secondary system follow ng any plant transients or accidents.

The S/G 1evel measuring system is an open-column reference leg system providing a signal to a 2 out of 3 logic activation system.

The effects of post-accident ambient temperatures following h a high energy line break inside containment were determined by Westing ouse VPA-79-36 and the results were forwarded to Vepco in Westinghouse line break letterT dated August 29 , 19 79 .

temperature of up. to 280*F may occur following a high energy l error of within 20% span.

contain=ent which may result in an indicated S/G Le 10% error in reference leg heatup effects.

North Anna initiated a satpoint change on the S/G On July 23, 1979, This change was to correct for the

'l Level Trip frcm 5% span to 15% span. A further change is not environmental effects on the S/G 1evel transmitters.

to the setpoint to correct for the reference leg heatup effects In the case necessary because a redundant reactor trip d by is provide a Safety Injection and subsequent reactor trip will be initiate i ment the Righ Containment Pressure signal which hoccurs t t of at a conta nN pressure of 17 PSIA.this trip will initiate approximately one second after t e will the transient and the maximum ambient containment temperatureThis reactor trip h ssure be approximately 180*F at the time of this trip.will not be a transmitters are located outside the containment.

Further corrective actions have been taken by incorporating precautions into breaks.

North Anna Emergency Procedures dealing wit possibility of erroneous S/G Level indications during post-accident conditions.

2.

The Pressurizer Level measuring system is a sealed reference leg syste providing a signal to a 2 out of 3 logic activation system.

No credit is taken in the safety analysis for this reactor Thus, trip the following a high energy line break inside containment. P environmental errors.

i086 i60

The initial post-accident containment temperatures may cause an erroneous indication of pressurizer level but further analysis is required to quantify the effects.

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