ML18153B964

Forwards DHR Instrumentation Study of Instrumentation Programmed Enhancements,Per Util 890203 Commitment in Response to Generic Ltr 88-17, Loss of Dhr.

ML18153B964
Person / Time
Site:	Surry, North Anna, 05000000
Issue date:	10/31/1989
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
88-737C, GL-88-17, NUDOCS 8911080166
Download: ML18153B964 (5)

Text

e e VIRGINIA ELECTRIC AND POWER COMPANY RICHMOND, VIRGINIA 23261 October 31, 1989 United States Nuclear Regulatory Commission Serial No. 88-737C Attention: Document Control Desk NO/JZL:vlh Washington, D. C. 20555 Docket Nos. 50-280 50-281 50-338 50-339 License Nos. DPR-32 DPR-37 NPF-4 NPF-7 Gentlemen:

VIRGINIA ELECTRIC AND POWER COMPANY SURRY POWER STATION UNITS 1 AND 2 NORTH ANNA POWER STATION UNITS 1 AND 2 GENERIC LETTER 88-17: LOSS OF DECAY HEAT REMOVAL PROGRAMMED ENHANCEMENTS FOR INSTRUMENTATION On February 3, 1989, Virginia Electric and Power Company submitted our response for the six programmed enhancements recommended in Generic Letter 88-17, Loss of Decay Heat Removal. In the above submittal, we committed to performing a Decay Heat Removal Instrumentation Study to fully evaluate the instrumentation programmed enhancements. We have completed our study and the results of our final evaluation of the instrumentation programmed enhancements are attached.

Should you have any questions concerning this submittal, please contact us.

Very truly yours,

~~-

Senior Vice President - Power Attachment

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

Suite 2900 Atlanta, Georgia 30323 Mr. W. E. Holland NRC Senior Resident Inspector Surry Power Station Mr. J. L. Caldwell NRC Senior Resident Inspector North Anna Power Station

PROGRAMMED ENHANCEMENTS FOR INSTRUMENTATION Provide reliable indication of parameters that describe the state of the reactor coolant system (RCS) and the performance of systems normally used to cool the RCS for both normal and accident conditions. At a minimum, provide the following in the control room (CR):

(a) two independent RCS level indications

Response

Surry Power Station (SPS) has a permanent standpipe reactor vessel level indication system for use during cold shutdown conditions. The RCS standpipe level indication system provides local level indication as well as remote level indication in the control room and annunciation of low RCS level. North Anna Power Station (NAPS) has a similar permanent standpipe reactor level indication system partially installed. The NAPS permanent RCS standpipe level indication system will be completed prior to the next entry into a reduced inventory condition.

Various means of providing a second independent level indication were evaluated during our Decay Heat Removal Instrumentation Study. As a result, we have selected an ultrasonic level detector which will measure the water level in the C loop hot leg.

Hot leg level will be indicated in the control room with annunciation of low RCS level.

We believe that the combination of the RCS standpipe level indication and the ultrasonic hot leg level indication provides for reliable indication of RCS level under diverse operating conditions, including abnormal conditions. To further enhance RCS level indication reliability, it is our intent to provide power to at least one system from a vital bus. The ultrasonic level detection system will be installed during the next refueling outage at each station.

(b) . at least two independent temperature measurements representative of the core exit whenever the reactor vessel (RV) head is located on top of the RV. (We suggest that temperature indications be provided at all times.)

Response

Our previous submittals have noted that both SPS and NAPS utilize at least two independent core exit thermocouples to provide indication of core exit temperature in the control room. The core exit thermocouples are required to be operable prior to and during reduced inventory operation with the reactor vessel head in place. The core exit thermocouples are periodically monitored and recorded by the control room operators.

When the core exit thermocouples are not available and the reactor head is still in place, reduced inventory operation will not be allowed. Once the reactor head is removed from the reactor vessel, the residual heat removal (RHR) system temperature indications are adequate to monitor core cooling. Should a loss of RHR occur with the

reactor vessel head removed, procedures exist to provide alternate RCS cooling until RHR can be restored.

The Decay Heat Removal Instrumentation Study evaluated the temperature monitoring systems described above, as well as alternative methods available to provide core exit temperature. It was concluded that existing temperature measurement systems were adequate and that they comply with the requirements of Generic Letter 88-17.

Accordingly, no additional temperature monitoring systems are required.

(c) the capability of continuously monitoring the decay heat removal (DHR) system performance whenever a DHR system is being used for cooling the RCS and (d) visible and audible indications of abnormal conditions in temperature, level, and DHR system performance.

Response

The Decay Heat Removal Instrumentation Study evaluated the existing RHR system instrumentation for the capability of continuously monitoring RHR system performance and the ability to detect abnormal conditions. It is noted that RHR temperature is monitored at the common discharge of the RHR pumps and at the system discharge to the RCS. RHR system flow is also monitored. The above temperature indications and the flow indication are available in the control room, and provide the primary means of monitoring system performance. In addition, a low flow condition is visually and audibly annunciated in the control room to alert operators of abnormal system conditions. Experience has proven that the low flow alarm is an effective and reliable indicator of RHR system trouble. SPS has the additional feature of annunciating high temperature at the RHR system discharge to the RCS system.

The above instrumentation, in conjunction with the RCS level instrumentation previously discussed, provides an adequate capability to continuously monitor RHR system performance and to detect and annunciate abnormal conditions. Additional indications are also available in the control room which may assist the operators in diagnosing system problems. These indications include RHR pump motor current, RHR pump auto trip alarm, RHR suction and discharge motor operated valve position indication when energized, and RHR pump discharge high pressure alarm. Based on our evaluation of the available instrumentation, we have concluded that additional instrumentation beyond the ultrasonic hot leg level system is not required.

(

1, I

' V e e COMMONWEALTH OF VIRGINIA )

)

COUN1Y OF HENRICO )

The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by W. L. Stewart who is Senior Vice President - Power, of Virginia Electric and Power Company. He is duly authorized to execute and file the foregoing document in behalf of that Company, and the statements in the document are true to the best of his knowledge and belief.

Acknowledged before me this .3L day 01 LO~. 1glz'.

My Commission Expires: d!t.b!JLt_a,11} d5, 19*-_.

&~- Notary Public (SEAL) ,~