ML20055H565

Requests for Temporary Waiver of Compliance from Requirement of Tech Spec 3.3.1.1,Table 2.3-2 Re Response Time Testing. Request Does Not Pose Significant Hazards Consideration

ML20055H565
Person / Time
Site:	North Anna
Issue date:	07/20/1990
From:	Stewart W VIRGINIA POWER (VIRGINIA ELECTRIC & POWER CO.)
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
90-459, NUDOCS 9007270005
Download: ML20055H565 (4)

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, VIwo,uA ELacTurc Awn Pownu CouPAxy Ricnwoxu,Vimoix A voces July 20, 1990 United States Nuclear Regulatory Commission Serial No.: 90 459 Attention: Document Control Desk NAPS /JHL R5 Washington, D.C 20555 Docket Nos.: 50 338 50 339 License Nos.: NPF-4 L NPF 7 Gentlemen:

- MbidNIA ELECTRIC AND POWER COMPANY NORTH ANNA POWER STATION UNITS 1 AND 2 REQUEST FOR TEMPORARY WAIVER OF COMPLIANCE I

Technical Specification 3.3.1.1, Table 3.2 2 requires time response testing of the pressurizer high level reactor trip function be performed on at least one channel every 18 months such that all 3 channels are tested at least once every 54 months. In addition, the Specification requires that the response time for each channel be less than or equal to 2 seconJs. A temporary waiver of compliance is requested to allow continued operation of North Anna Units 1 and 2 until response time testing of these a chancais can be performed during the next refueling outages. Response time testing of the pressur!zer water level channels is not desired during power operations and would increase the potential for an unnecessary reactor trip.

o On January 3,1989, the NRC issued License Amendment No.112 for North Anna Unit

1. The issuance of the amendment allowed a less restrictive negative moderator temperature coefficient for the remainder of the operating cycle. The letter transmitting the amendment indicated that an identical amendment for North Anna Unit 2 and for '

_ future cycles of Unit 1 would be issued at a later date. On June 30,1989, the NRC issued Amendment No.100 for North Anna Unit 2. This amtndment allowed the same revisions to the Technical Specifications as Amendment No.112 for Unit 1 and was applicable to all future operating cycles. The amendment also granted the continued use of License Amendment No 112 for future cycles of North Anna Unit 1.

Amendment No.112 added the requirement to response time test the pressurizer high level reactor trip channels to ensure they would respond within 2 seconds. This k response time testing requirement was added to protect against overfilling the pressurizer prior to the actuation of the overtemperature delta T reactor trip. Under e certain plant conditions with channel response times greater than 2 seconds it is

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i possible to overfill the pressurizer before the overtemperature delta T aacter trip function would initiate.

North Anna Unit 1 was operating ,n a power coastdown mode when Amendment No.

112 was received. From February 25,1989 to July 16,1989, North Anna Unit 1 was in a maintenance and refueling outage. During this refueling outage, the pressurizer high level reactor trip channels were not response time tested in accordance with Technical Specification 3.3.1.1. This was due to an administrative error in not effectively Jmplementing License Amendment No.112. North Anna Unit 2 was operating at 100% powcr when License Amendment No.100 was received on June 30,1989 and has continued operating since that time. There has been no c'pportunity to perform the response time testing.

Response time testing of the pressurizer high level reactor trip channels is not desired at this time. Currently, testing would have to be performed during power operations while Technical Specification 3.3.1.1, Table 4.31 requires testing to be performed every 18 months. Testing during power operations would increase the potential for an unnecessary reactor trip.

The accident analysis for North Anna takes credit for the pressurizer high level channels only for one ANS Condition ll event, namely the uncontrolled control rod withdrawal at power. (The rod withdrawal has been shown to bound boron dilution events.) Virginia Power determined via the analyses suppolting Amendment Nos.112 and 100 that the high level channel with a response time less than 2 seconds was required to prevent overfilling the pressurizer with liquid for a small subset of the spectrum of possible rod withdrawal at power cases. Filling the pressurizer is a violation of one of the safety analysis criteria for ANS Condition ll (moderate frequency) events set forth in the UFSAR. This criterion is based on the concern that liquid relief from the pressurizer power operated relief or safety valves could resJllin the malfunction of those components. This could possibly cause a more severe event (l. e, smalt loss of coolant accident, classified as ANS Condition Ill).

The analys9s show that filling the pressurizer is a potential concern for on'.y the following narrow subset of reactivity insertion events:

1) Reduced power operation in the power range. Operation at full rated power precludes the concern. In addition, operation in the startup or shutdown modes is protected by diverse r -actor protection system functions (e.g.,  ;

source range, intermediato range, power range low setpoint high flux trips).

2) Two of the three pressurizer high level trip channels with total channel response times in excess of 2 seconds or otherwise inoperable.

3) Large integrated reactivity insertions. Detailed review of the analyses showed that for current cycle burnup and beyond, the amou:11 of reactivity insertion from rod withdrawal required to fill the pressurizer exceeded the reactivity associated with the control banks at their respective insertion limits by a significant amount (l. E. by a factor of approximattely 2 at all conditions). >

) Currently, Unit 1 is at a low boron concentration (246 ppm) and Unit 2 is at

% zero boron in a power coastdown. As a result, there is not enough boron in either unit's core to create the concern of overfilling the pressurizer prior to

actuation of the ovenemperature delta T reactor trip function during a boron d!!ution event. Therefore, the 2 second response time test of the pressurizer high level reactor trip channels is not a concern at this time in core life for j either North Anna 1 or 2.

For events not meeting these criteria, the analyses show that the reactor will trip on  :

diverse sources of pro %ction (either overtemperature delta T or power range high i neutron flux) before the reactor coolant system can heat up enough to fill the i pressurizer.

Approximately 80 transmitters of similar design and function have besn previously respMse time tested during the last refueling outage for each unit. Typical response  ;

times for the channels is less than 0.5 seconds. Based on this data, there is t reasonable assurance that the pressurizer high water level reactor trip channels will function within the required 2 seconds. In addition, channel functional tests are l l performed on a monthly frequency and test the operability of the alarm and/or trip i function by injection of a simulated signal as close to the sensor as practical. Also, a channel calibration is performed each refueling outage which encompasses the entire channel which includes the sensor, alarm and/or trip functions.

Based on the abovo information, continued operation until the next refueling outage of Unit 1 and 2 without performing the pressurizer level responto time test is acceptable ,

based on the following:

1) An assessment of the available data for similar channels (l. e. the narrow range steam generator low. low level channels) indicates a high degree of i confidence that the total response time for the channel will be significantly less than 2 seconds.

2) For current core conditions, the safety analysis shows that no credit has to be taken for the pressurizer high level trips. This conclusion is valid throughout the remainder of cycle life for both units.

The ,iealth and safety of the general public are not affected by this request for  !

temporary waiver of compliance. This request does not pose a significant hazards

consideration.

This request has been reviewed and approved by the Station Nuclear Safety and Operatirg Committee. If you have any questions or require additional information, pl ease contact us.

Very truly yours, W. L. Stewart Senior Vice President Nuclear L .

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oc: U. S. Nuciser Regulatory Commission Region ll 101 Marietta Street, N. W.

Suite 2900 Atlanta, Georgia 30323 Mr. M. S. Lesser NRC Senior Resident inspector North Anna Power Station