ML20244A675

Responds to NRC Re Safety Significant Matters Found in SSOMI During Wks of 890213 & 27

ML20244A675
Person / Time
Site:	North Anna
Issue date:	03/31/1989
From:	Cartwright W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
89-206, NUDOCS 8904180130
Download: ML20244A675 (7)

Text

'

r I

+

( ,

l VINGINIA ELECTRIC AND POWER COMPANY

- HrcnwoNn,VIHOINIA 20261 ad 31,1989

. w. n.ciarwnwar VICS PBBSEDEFT NUCLEAR U. S. Nuclear Regulatory Commission Serial No. L 89-206.

- Attn: Document Control Desk NO/SEC LIC:JmJ Washington, D. C. 20555 Docket Nos. 50-338-50-339 License Nos. N P F-4 N P F-7 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 SAFETY SYSTEM OUTAGE MODIFICATION INSPECTION SIGNIFICANT ITEMS During the weeks of February 13 and February 27,1989, the NRC conducted the design review

~ portion of the SSOMI for North Anna Power Station.

'in your letter of March 17,-1989, the NRC characterized four findings of the SSOMI as " safety

significant matters" and requested that we address them in an expeditious manner.

Enclosed is Virginia Electric and Power Company's response to these items. We will resolve -

these issues as addressed in the attachment, for each unit prior to the completion of the current refueling outage for that unit. - The current status of these items was discussed with members of the NRC staff in a conference call on March 30,1989. We will advise you of any significant changes.

If you have further questions, please contact us.

Very truly yours, m

W. R. Cartwright l-Attachment j;gusgsse8?88%ge o

'f

l 1, ,

cc: U. S. Nuclear Regulatory Commission 101 Marietta Street, N.W.

i -'

-Suite 2900 Atlanta, GA' 30323 .

Mr. J. L.' Caldwell

' NRC Senior Resident inspector North Anna Power Station l

gs

\

1 l

l l

l

4 9

8 e e

i RESPONSE TO SSOMI SAFETY SIGNIFICANT ISSUES l

9 l l p ,

l l

1 i

f Virginia Electric and Power Company  !

1 1 1

i ,

l l j L

q

f*

to ,

1 g .; ,

w

%f# * '

g ,4 g n

b ITEM 1

$ The inspection team identified that the service water system spray and bypass. valve h;' motor actuators were sized for an incorrect ' differential pressure rating of 50 psi, in addition, the corresponding torque switch settings for the actuators were also based on-g the 50 psi differential pressure rating. -This calls into question the ability of this safety system to operate if ~ called on to function. VEPCO was requested to verify the correct  ;

~

differential pressure rating for these valves and make any changes necessary to ensure JI h

1' the actuators would deliver. the required torque un' der all postulated design basis conditions.

7 RESPONSE

.The Service Water System spray array and bypass MOV actuators were sized for an incorrect differential pressure of 50 psi rather than the, maximum shut off head differential- pressures.

a An engineering review of the Service Water MOVs has determined that the installed spray array MOVs have' sufficient margin to develop the torque required to operate under.

all design basis conditions (including shut off head differential pressure) If the torque

. switch settings are set to the appropriate values. The torque switches for the spray array MOVs are being reset to the revised values.

The installed bypass MOVs require heavier spring packs in the motor operators as well as resetting the torque switches to the appropriate values to operate under the maximum differential pressure. ' Until the spring packs are replaced and the torques switches set, administrative controls will b'e implemented to prohibit operating in MODES 1 through 4 with the bypass MOVs throttled. This will insure that the bypass valve motor operators will have sufficient torque to operate under design basis conditions.

l We will revise the Setpoint Document and the MOV Specification to reflect the appropriate design differential pressures and torque switch settings.

1 i

l

ITEM 2 As a result of the inspection team's identification of various unjustified assumptions and omissions in setpoint calculations, the team.became concerned that a controlled methodology for performing setpoint calculations did not exist. To provide assurance - ,

that no safety system setting limits had been inadvertently compromised as a result of I design changes implemented since the plant was licensed, the inspection team requested that a specific sample of 10 setpoint calculations be- verified including proper consideration of instrument span, drift value, cable accuracy and measuring / test equipment accuracy. Also, VEPCO was requested to report any reduction in safety margin identified as a result of this verification.

RESPONSE

To provide assurance that safety system setting limits have not been inadvertently

. compromised, we will review the-10 specified setpoint calculations.

This review is to verify that proper consideration was given to uncertainty factors due -

to instrument span, instrument drift, instrumeet cables and measuring and test equipment.

DCPs and EWRs being implemented during the 1989 refueling outages will be reviewed to assure setpoint changes were adequately performed. A procedure for setpoint.

calculation and revision will be developed.

We will report any reduction in safety margins identified by this review process.

4

ITEM 3 The inspection team identified that non-Class 1E pressure transmitters for the service water system were powered from a Class 1E vital power source, without proper isolation. VEPCO was requested to Justify or correct the specific service water instrumentation as well as evaluate other possible instances of improper isolation i elsewhere in the facility.

> RESPONSE The design of the Service Water System pressure transmitter instrumentation will be reviewed to ensure that it meets the plant design basis. If necessary, modifications will be made to insure proper electrical isolation.

Additionally, we will evaluate other engineering packages being implemented during the 1989 refueling outages for proper isolation and adherence to plant design basis.

1 I

____-_____-____L

o

.i

,; j j

4 ITEM 4 I

The inspection team noted that design change packages (DCPs) did not explicitly prescribe the necessary testing required to demonstrate functionality of the system and affected components following the change. VEPCO has committed to update the associated i procedures to ensure that the required testing would be accomplished for future modifications. To insure that the modifications being installed during the current outage are functionally tested subsequent to the installation and to ensure that the capability of the affected systems to mitigate the design basis accidents has not been compromised, VEPCO was requested to incorporate the specific post modification testing requirements into the design change packages or engineering work request scheduled to be installed for this outage.

RESPONSE

Design Change Packages (DCPs) and Engineering Work Request (EWRs) being implemented during the 1989 refueling outages that affect system performance, are being reviewed to insure that the following functional criteria have been met:

a. The operational logic of the circuit is as intended by the design change for the Installed modification.

I

b. The operational logic of any other system input to or output from the circult(s) modified or installed is not altered by the design change except as noted in item c, below,

c. The modified circuit output operational logic remains unchanged unless it is specifically altered by the design change.

Procedures governing DCP and EWR preparation will be revised to assure that adequate functional testing for the modification and affected systems is both performed and documented. l

- _ _ _ _ _ -____- - ___ _____