ML042190342

License Amendment Request: Change a Surveillance Requirement for Reactor Trip Circuit Breakers

ML042190342
Person / Time
Site:	Calvert Cliffs
Issue date:	08/03/2004
From:	Vanderheyden G Constellation Energy Group
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML042190342 (9)

Text

i George Vanderheyden 1650 Calvert Cliffs Parkway Vice President Lusby, Maryland 20657 Calvert Cliffs Nuclear Power Plant 410.495.4455 Constellation Generation Group, LLC 410.495.3500 Fax Constellation Energy August 3, 2004 U. S. Nuclear Regulatory Commission Washington, DC 20555 ATTENTION: Document Control Desk

SUBJECT:

Calvert Cliffs Nuclear Power Plant Unit Nos. 1 & 2; Docket Nos. 50-317 & 50-318 License Amendment Request: Change a Surveillance Requirement for Reactor Trip Circuit Breakers Pursuant to 10 CFR 50.90, Calvert Cliffs Nuclear Power Plant, Inc (CCNPP) hereby requests an amendment to Renewed Operating License Nos. DPR-53 and DPR-69 to extend the surveillance test interval for reactor trip circuit breakers from 31 days to 92 days. This change is based on Topical Report CE NPSD-95 1-A, Revision 01, "Reactor Trip Circuit Breakers Surveillance Frequency Extension." The increased surveillance interval will increase the reliability of the circuit breakers by reducing wear through less frequent cycling of the breakers.

The evaluation of the proposed change is included as Attachment (1) and the proposed Technical Specification page changes are shown in Attachment (2). The Technical Specification Bases will be changed as appropriate to support this amendment. We have considered the possibility of significant hazards associated with this change and have determined there are none (see Attachment 1 for a complete discussion).

Our Plant Operations Safety Review Committee and Nuclear Safety Review Board have reviewed these proposed changes to the Technical Specifications and our determination of significant hazards. They have concluded that implementation of these changes will not result in an undue risk to the health and safety of the public.

We request approval of the proposed license amendment as soon as possible so we may reduce the number of tests the breakers are undergoing and no later than August 1, 2004, with the amendment being implemented within 60 days.

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Document Control Desk August 3, 2004 Page 2 Should you have questions regarding this matter, we will be pleased to dis ss them with you.

Very t u a_._

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S1 ATE OF MAKYLAND

TO WIT:

COUNTY OF CALVERT I, George Vanderheyden, being duly sworn, state that I am Vice President - Calvert Cliffs Nuclear Power Plant, Inc. (CCNPP), and that I am duly authorized to execute and file this License Amendment Request on behalf of CCNPP. To the best of my knowledge and belief, the statements contained in this document are true and correct. To the extent that these statements are not based on my personal knowledge, they are based upon information provided by other CCNPP employees and/or onsultants. Such information has been reviewed in accordance with company practice and I bel to reliable.

Subscribed and sworn before nS a Notary Public in and for the State of Maryland and County of

'5Othis 3 day of 9 t ,2004.

I /

WITNESS my Hand and Notarial Seal: WITNESS ~~ mye HadnNtrilSel Notary P My Colnmissrodh.Expires:

2t Dafe 7

by 6X,3/jd 1-I-Attachmnenfs' (1) Tecchnical Basis and No Significant Hazards Consideration (2) Marked-up Technical Specification Pages cc: J. Petro, Esquire H. J. Miller, NRC J. E. Silberg, Esquire Resident Inspector, NRC Director, Project Directorate I-1, NRC R. I. McLean, DNR R. V. Guzman, NRC

A¶TACHMENT (1)

TECHNICAL BASIS AND NO SIGNIFICANT HAZARDS CONSIDERATION TABLE OF CONTENTS

3.0 PROPOSED CHANGE

4.0 PROBABILISTIC RISK ANALYSIS 5.0 TOPICAL REPORT 6.0 NO SIGNIFICANT HAZARDS CONSIDERATION

7.0 ENVIRONMENTAL CONSIDERATION

8.0 PRECEDENT 9.0 REFERENCE Calvert Cliffs Nuclear Power Plant, Inc.

August 3,2004

ATTACHMENT (1)

TECHNICAL BASIS AND NO SIGNIFICANT HIAZAIIDS CONSIDERATION

1.0 DESCRIPTION

The function of the reactor trip circuit breakers (RTCB) is to open, creating a reactor trip by interrupting power to the control element drive mechanisms. There are two diverse devices in each RTCB to perform this function. The first is a shunt trip device that has an actuation coil that is normally deenergized. A Reactor Protective System (RPS) trip signal energizes the shunt trip device to open the RTCB. The second is an undervoltage device that has an actuation coil, which is normally energized. A trip signal or loss of voltage on a vital DC bus will interrupt power to the undervoltage device, causing it to open the RTCB.

The functional tests independently cycle each breaker under-voltage and shunt trip devices. Therefore, each RTCB experiences a minimum of 66 trips during a refueling cycle, consisting of 48 monthly trips because of the RTCB tests [Surveillance Requirement (SR) 3.3.3.1], 16 quarterly trips because of RPS logic tests (SR 3.3.3.2), and 2 trips because of the post-refueling outage RPS manual test (SR 3.3.3.3).

We consider this number of trips to be excessive as frequent operation is causing undue wear of the mechanisms and is detrimental to the reliability of the breakers.

2.0 BACKGROUND

The RPS initiates a reactor trip to protect against violating the core specified acceptable fuel design limits and reactor coolant pressure boundary integrity during anticipated operational occurrences. By tripping the reactor, the RPS also assists the engineered safety features systems in mitigating accidents. The RTCBs are a module of the RPS that open to trip the reactor. They are configured in four channels with two breakers in each channel.

All of the Updated Final Safety Analysis Report Chapter 14 transient and accident analyses that call for a reactor trip assume that the RTCBs operate and interrupt power to the control element drive mechanisms.

Consequently a Technical Specification channel functional test is performed on each RTCB channel every 31 days to verify proper operation. The channel functional test is performed manually by actuating the breaker's associated trip pushbuttons. Calvert Cliffs' Technical Specifications also require testing the RPS logic and manual trip channels, which cause tripping of the associated RTCB.

3.0 PROPOSED CHANGE

This letter requests an amendment to change Technical Specification SR 3.3.3.1 from 31 days to 92 days.

The description of the surveillance in the Technical Specification Bases will include direction to test the RTCBs on a staggered basis with the RPS logic channel functional test (SR 3.3.3.2). The request utilizes Combustion Engineering (CE) Owners Group Topical Report NPSD-95 1-A (Reference 1), which was reviewed and accepted by the Nuclear Regulatory Commission. Calvert Cliffs is one of the plants included in the study that resulted in the topical report.

Changing the test interval to 92 days and staggering it with SR 3.3.3.2 will reduce the number of manual trips from 66 to 34 trips per refueling cycle. The new number consists of 16 SR 3.3.3.1 tests, 16 SR 3.3.3.2 tests and 2 SR 3.3.3.3 tests. These numbers are different from the number of tests in the topical report because the topical assumes an 18-month refueling cycle and Calvert Cliffs is on a 24-month cycle.

4.0 PROBABILISTIC RISK ANALYSIS We have conducted a probabilistic risk analysis to determine the change in average risk, consisting of core damage frequency (CDF) and large early release frequency (LERF), associated with increasing the SR 3.3.3.1 surveillance interval and making the interval staggered with SR 3.3.3.2.

1

ATTACHMENT (1)

TECHNICAL BASIS AND NO SIGNIFICANT HAZARDS CONSIDERATION The results of the analysis are:

1. The change in CDF is <1.OE-6.

2. The change in large early release frequency (LERF) is <1.OE-7.

The calculations are based on proportional increases of the demand failure value. That is, a tripling of the test interval is evaluated by tripling the demand failure value. Proportional adjustments tend to be conservative for demand failure cases because an embedded failure will appear on the next demand regardless of how much time has elapsed between tests.

The probabilistic risk analysis utilizes the acceptance criteria in Regulatory Guide 1.174 as they pertain to Calvert Cliffs. The acceptance criteria are conditional on the value of the baseline risk metric in that, if the CDF is considerably higher than 1.OE-4 per reactor year, then the focus should be on finding ways to decrease rather than increase it. Calvert Cliffs has a calculated internal and external event CDF of less than L.OE-4 per reactor year. Therefore, the guidance in Regulatory Guide 1.174 indicates that the increases in CDF and LERF shown above are very small. We consider the change in average risk associated with the proposed amendment is acceptable.

5.0 TOPICAL REPORT Topical Report CE NPSD-951-A "examined the operating history of reactor trip circuit breakers and recommended changes in surveillances to reduce overtesting, which should increase the reliability of the RTCBs, while minimizing the potential for challenges to plant systems through inadvertent scrams." The study recorded in the report included data from Calvert Cliffs as well as other Combustion Engineering plants. We have reviewed the topical report and find it still applies to Calvert Cliffs. The topical report reviewed the Institute of Nuclear Power Operation's Nuclear Plant Reliability Data System and identified that, from 1986 to 1993, there was only one total failure of a breaker to open of all the breakers in 13 CE power plants. In addition to the data in the topical report, we have conducted a review of Calvert Cliffs' test records and found no recorded failures for both units from 1994 through 2003. The result documented in the topical report gives a failure rate of 0.6E-4 per demand, which compares favorably with the failure rate of 5.3E-4 in NUREG/CR-4639, "Nuclear Computerized Library for Assessing Reactor Reliability (NUCLARR)." The topical report concluded that the lower failure rate in the topical report compared to the NUCLARR value justifies the extension of the RTCB functional test (Calvert Cliffs SR 3.3.3.1) from one month to quarterly. Additionally, the topical report noted that the RTCB reliability to trip on demand will actually be verified every six weeks instead of every three months when the proposed quarterly surveillance is staggered with the quarterly RPS logic functional test (Calvert Cliffs SR 3.3.3.2).

6.0 NO SIGNIFICANT HAZARDS CONSIDERATION The proposed changes have been evaluated against the standards in 10 CFR 50.92 and have been determined to not involve a significant hazards consideration in that operation of the facility in accordance with the proposed amendment:

1. Would not involve a significant increase in the probability or consequences of an accident previously evaluated The reactor trip circuit breakers (RTCB) are part of the Reactor Protective System (RPS). The RPS initiates a reactor trip to protect against violating the core specified acceptable fuel design limits and reactor coolant pressure boundary integrity during anticipated operational occurrences. By opening the RTCBs to trip the reactor, the RPS also assists the engineered safety features systems 2

ATTACHMENT (1)

TECHNICAL BASIS AND NO SIGNIFICANT HAZARDS CONSIDERATION in mitigating accidents. All of the accident analyses that call for a reactor trip assume that the RTCBs operate and interrupt power to the control element drive mechanisms. The proposed testing interval will result in less wear on the RTCBs and, thereby, increase breaker reliability.

The RTCBs are accident mitigators and do not affect the probability of an accident.

Topical Report CE NPSD-951-A shows only one failure up to 1993 in the plants studied. Calvert Cliffs' surveillance records show no failures from 1994 to 2003. This data demonstrates that the consequences of an accident will not be significantly increased by extending the surveillance interval and imposing a staggered test interval.

Therefore, extending the surveillance interval and imposing a staggered test interval does not involve a significant increase in the probability or consequences of an accident previously evaluated.

2. Would not create the possibility of a new or different type of accidentfrom any accidentpreviously evaluated.

There is no change in plant equipment or operation related to this license amendment request. The RTCBs are accident mitigators and extending the surveillance interval and imposing a staggered test interval does not adversely affect their operation.

Therefore, this proposed amendment does not create the possibility of a new or different type of accident from any accident previously evaluated.

3. Would not involve asignificant reduction in the margin ofsafety.

The margin of safety in this case is the reliance on the RTCBs to open on a signal from the RPS.

Extending the surveillance frequency and imposing a staggered test interval results in a test every six weeks as opposed to the current monthly test. The new interval will result in less wear on the RTCBs, thereby improving the margin of safety.

Therefore, extending the surveillance interval and imposing a staggered test interval will not involve a significant reduction in the margin of safety.

Based on the above discussion, the proposed amendment presents no significant hazards consideration under the standards set forth in 10 CFR 50.92(c), and a finding of "no significant hazards consideration" is justified.

7.0 ENVIRONMENTAL CONSIDERATION

We have determined that operation with the proposed change would not result in any significant change in the types or amounts of any effluents that may be released offsite, nor would it result in any significant increase in individual or cumulative occupational radiation exposure. Therefore, the proposed amendment is eligible for categorical exclusion as set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b), no environmental impact statement or environmental assessment is needed in connection with the proposed amendment.

8.0 PRECEDENT Waterford Steam Electric Station, approved by the NRC on June 29, 1999 3

ATTACHMENT (1)

TECHNICAL BASIS AND NO SIGNIFICANT HAZARDS CONSIDERATION 9.0 REFERENCE I. Combustion Engineering Owners Group Topical Report CE NPSD-951-A, Revision 1, "Reactor Trip Circuit Breakers Surveillance Frequency Extension," dated September 1999 4

ATTACHMENT (2)

MARKED UP TECHNICAL SPECIFICATION PAGES Calvert Cliffs Nudear Power Plant, Inc.

August 3, 2004

, I I .

RPS Logic and Trip Initiation 3.3.3 ACTIONS (continued) .. _-_._-.

CONDITION REQUIRED ACTION COMPLETION TIME D. Two channels of RTCBs D.1 Open the affected Immediately or Trip Path Logic RTCBs.

affecting the same trip leg inoperable.

E. Required Action and E.1 Be in MODE 3. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> associated Completion Time of Condition A, AND B, or D not met.

E.2 Open all RTCBs. 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> OR One or more Functions with two or more Manual Trip. Matrix Logic, Trip Path Logic, or RTCB channels inoperable for reasons other than Condition A or D.

SURVEILLANCE REQUIREMENTS SURVEILLANCE FREQUENCY SR 3.3.3.1 Perform a CHANNEL FUNCTIONAL TEST on each days RTCB channel.

SR 3.3.3.2 Perform.a CHANNEL FUNCTIONAL TEST on each 92 days RPS Logic channel.

CALVERT CLIFFS - UNIT 1 3.3.3-2 Amendment No. 227 CALVERT CLIFFS - UNIT 2 Amendment No. 201