ML051920358

Proposed Technical Specification Amendment Re Nuclear Service Water System Headers

ML051920358
Person / Time
Site:	Catawba
Issue date:	07/06/2005
From:	Jamil D Duke Energy Corp, Duke Power Co
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML051920358 (16)

Text

7 Pkuke D.M. JAMIL Vice President OrPowere Duke Power Catawba Nuclear Station 4800 Concord Road / CN01 VP York, SC 29745-9635 803 831 4251 803 831 3221 fax July 6, 2005 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, D.C. 20555

Subject:

Duke Energy Corporation Catawba Nuclear Station, Units 1 and 2 Docket Numbers 50-413 and 50-414 Proposed Technical Specification Amendment Technical Specification 3.5.2, Emergency Core Cooling System; 3.6.6, Containment Spray System; 3.6.17, Containment Valve Injection Water System; 3.7.5, Auxiliary Feedwater System; 3.7.7, Component Cooling Water System; 3.7.8, Nuclear Service Water System; 3.7.10, Control Room Area Ventilation System; 3.7.12, Auxiliary Building Filtered Ventilation Exhaust System; & 3.8.1, AC Sources - Operating

Reference:

1) Letter from Dhiaa Jamil to U.S. Nuclear Regulatory Commission dated November 16, 2004.

2) Letter from Sean Peters, U.S. Nuclear Regulatory Commission, to Duke Energy Corporation dated February 16, 2005.

3) Letter from Dhiaa Jamil to U.S. Nuclear Regulatory Commission dated May 4, 2005.

Pursuant to 10 CFR 50.90, Duke Energy Corporation is submitting a revision to an amendment request submitted on November 16, 2004 to the Catawba Nuclear Station Facility Operating License and Technical Specifications (TS). The proposed TS changes will allow the "A" and "B" Nuclear Service Water System (NSWS) headers for each unit to be taken out of service for up to 14 days each for system upgrades.

Catawba Nudear Staion2Oth Anni95Yat www.dukepower. cor n 1985 -2005

U.S. Nuclear Regulatory Commission Page 2 July 6, 2005 This revision is based on discussions with the NRC after submittal of reference 3. These discussions concerned the probabilistic risk assessment (PRA) analysis for the proposed amendment. Catawba evaluated the dominant sequences and identified some additional actions that could be taken to reduce the overall plant risk.

The revisions are in sections 4.3, 4.6, and 4.7 of Enclosure 1.0. Attachment 1 to this letter contains those sections in their entirety. The revised sections supersede the respective sections from reference 3.

The conclusions reached in the original determination that the amendment contains No Significant Hazards Considerations pursuant to 10 CFR 50.92, and the basis for the categorical exclusion from performing an Environmental Assessment/Impact Statement pursuant to 10 CFR 51.22(c).(9) have not been changed based on the revisions in the attachment to this letter.

Pursuant to 10 CFR 50.91, a copy of this proposed amendment is being sent to the appropriate State of South Carolina official.

Inquiries on this matter should be directed to R. D. Hart at (803) 831-3622.

Very truly yours, Dhiaa Jamil RDH/s Attachments: 1) - REVISED SECTIONS

U.S. Nuclear Regulatory Commission Page 3 July 6, 2005 Dhiaa Jamil affirms that he is the person who subscribed his name to the foregoing statement, and that all the matters and facts set forth herein are true and correct to the best of his knowledge.

Subscribed and sworn to me:

l / Date My commission expires:

-* /D Date,,e 1 3, P SEAL

U.S. Nuclear Regulatory Commission Page 4 July 6, 2005 xc (with attachments):

W.D. Travers U.S. Nuclear Regulatory Commission Regional Administrator, Region II Atlanta Federal Center 61 Forsyth St., SW, Suite 23T85 Atlanta, GA 30303 E.F. Guthrie Senior Resident Inspector (CNS)

U.S. Nuclear Regulatory Commission Catawba Nuclear Station S.E. Peters (addressee only)

NRC Project Manager (CNS)

U.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08-G9 11555 Rockville Pike Rockville, MD 20852-2738 H.J. Porter Assistant Director Department of Health and Environmental Control 2600 Bull St.

Columbia, SC 29201

ATTACHEMENT 1 REVISED SECTIONS

4.3 Defense in Depth The proposed change to extend the AOT for each NSWS header and affected systems maintains the system redundancy, independence, and diversity commensurate with the expected challenges to system operation. The opposite train of emergency power and the associated engineered safety equipment remain operable during each NSWS train outage to mitigate the consequences of any previously analyzed accident.

In addition to the TS, the Work Control Program, Work Process Manual and associated procedures & programs that implement the Maintenance Rule (a)(4) Program provide for controls and assessments to preclude the possibility of simultaneous outages of redundant trains and to ensure system reliability. The proposed change to extend the AOT for each NSWS header will not alter the assumptions relative to the causes or mitigation of an accident.

The proposed change is required to meet the defense-in-depth principle consisting of a number of elements. These elements and the impact of the proposed change on each of these elements are as follows:

• A reasonable balance among prevention of core damage, prevention of containment failure, and consequence mitigation is preserved.

The proposed Allowed Outage Time change does have an impact on CDF and large early release frequency (LERF).

This impact is offset by the additional actions taken as described in the following bullet. Also, because this is a temporary and not a permanent change, the time averaged risk increase is acceptable. The increase in the overall reliability of the NSWS along with the decreased unavailability in the future because of this project will result in an overall increase in the safety of both Catawba units. Therefore, the change does not degrade core damage prevention and compensate with improved containment integrity nor do these changes degrade containment integrity and compensate with improved core damage prevention. The balance between prevention of core damage and prevention of containment failure is maintained.

Consequence mitigation remains unaffected by the proposed changes. Furthermore, no new accident or transients are introduced with the requested change.

Page 1

• Over-reliance on programmatic activities to compensate for weaknesses in plant design.

Safety systems will still function in the same manner with the same reliability. The following compensatory measures will be taken to provide additional assurance that public health and safety will not be adversely affected by this request. These actions will be applied to both Units 1 and 2 as necessary unless otherwise specified.

> During each 14-day period when operating with only one operable NSWS header, no major maintenance or testing will be planned on the remaining operable NSWS header. In addition, during each 14-day period, no major maintenance or testing will be planned on the operable equipment that relies upon NSWS as a support system. To the maximum extent practicable, routine tests (e.g. quarterly pump tests) and preventive maintenance work (e.g. motor checks) will be scheduled prior to or following each 14-day period. Certain tests may have to be performed during each 14-day period.

> Diesel Generator Jacket Water Heat Exchanger - A temporary Engineering Change will be installed on each train of EDGs on both units to maintain the technically inoperable EDG capable of being manually started while the normal NSWS supply piping is out of service. This will be accomplished by using water from the fire protection system.

> Diesel Generator Starting Air - An Engineering Change will be installed on each train of EDGs on both units to maintain the cooling water to the diesel generator starting air system aftercoolers while the normal NSWS supply piping is out of service. This will be accomplished by using drinking water to supply the aftercooler. This cooling water flow rate is adequate to maintain the non safety-related function of the starting air compressors.

> No major maintenance or testing will be planned on the operable offsite power sources during each 14 day period. Switchyard activities will be coordinated to ensure that the operable offsite power supply and main transformer on both units are protected to the maximum extent practicable.

Page 2

Appropriate training will be provided to Operations personnel on this TS change, contingency measures to be implemented during each 14 day period, and actions to be taken in the event of flooding in the turbine building. Also, Operations will review the loss of NSWS and loss of CCW procedures as well as perform extra rounds on the CCW system.

During each 14-day period, no major maintenance or testing will be planned on the Standby Shutdown Facility (SSF). To the maximum extent practicable, routine tests and preventive maintenance work for the SSF will be scheduled prior to or following each 14-day period.

> During each 14-day period, no major maintenance or testing will be planned on the operable trains of ECCS, CSS, CVIWS, AFW, CCW, CRAVS, ABFVES, and EDG.

Routine tests and preventive maintenance work for these systems will be scheduled prior to or following each 14-day period. These items are being done to ensure the operable trains are protected to the maximum extent practicable.

During each 14-day period that a NSWS header is out of service, the operable trains remaining in service will be considered protected trains. Operations will increase their routine monitoring of these trains to help ensure their operability. This increase in routine monitoring will also include the Turbine Building to ensure no flooding in this area.

Plant procedures will be used to cross tie selected CCW system loads during the time period a CCW heat exchanger will be out of service during each NSWS header outage.

The Turbine Building flooding comprises several of the accident sequences. Catawba has installed permanent flood protection barriers in the turbine building to mitigate this issue. In addition, to help reduce any potential flooding issues, no major maintenance or testing will be planned on the Condenser Circulating Water System. Operators will also review actions to be taken in the event of flooding in the Turbine Building. These actions decrease the time to react to internal flooding Page 3

transients and therefore result in a reduction of risk.

> An action taken by Catawba to reduce the likelihood of an operator failing to get to the SSF and performing the required actions is to station an individual in the SSF continuously. This individual is trained on how to operate the SSF diesel generator and the standby makeup pump to establish an alternate method of reactor coolant pump seal injection. This will provide additional assurance that the SSF will be available during each NSWS header outage.

> The PRA model has been revised since the first submittal on November 16, 2004. The revised model was used for a new PRA calculation. Previous analyses indicated that the dominant accident sequences involved a loss of normal power to the operable 4160V ac bus during the NSWS header outage(s). To mitigate the risk of a potential core damage event, two separate operator actions have been identified that will be incorporated into existing plant procedures. The first one involves dispatching operators to throttle key Auxiliary Feedwater valves to supply the flow to the steam generators prior to the depletion of the vital batteries preventing steam generator overfill and thus protecting the steam supplies to the AFW turbine driven pump. The second operator action involves the CCW system in cross-train alignment, where if the operable 4160V ac bus is lost, operators would be instructed to align the available CCW pumps in the maintenance train through the CCW heat exchanger corresponding to the train without power. This will provide cooling to a CCW essential header. These procedure changes will ensure that the importance of this action is communicated to Operations and the improved operator response to these events results in a reduction of risk over that identified in the PRA.

• System redundancy, independence, and diversity are maintained commensurate with the expected frequency and consequences of challenges to the system.

There is no impact on the redundancy, independence, or diversity of the systems described in this TS amendment or on the ability of the plant to respond to Page 4

events with diverse systems. The systems described in this TS amendment are diverse and redundant systems and will remain so. The following discussion addresses each system affected by this TS change.

NSWS During this time period the operable NSWS loop will be protected to the extent practical by minimizing any maintenance on the system for either unit. In this configuration, the operable loop will still respond as designed during design basis events.

ECCS During the time when a NSWS loop is out of service, the respective ECCS equipment on the CCW train without NSWS cooling will be supplied from the opposite CCW train via a cross train alignment. In this cross train alignment selected essential heat loads, except for the heat exchangers associated with the RHR and CCW systems, for the CCW train made inoperable will be supplied by the operable CCW train.

During this time period the operable ECCS train will be protected to the extent practical by minimizing any maintenance on the system for either unit. In this configuration, the operable train will still respond as designed during design basis events.

CS During this time period the operable containment spray system train will be protected to the extent practical by minimizing any maintenance on the system for either unit. In this configuration, the operable train will still respond as designed during design basis events.

CVIWS During the NSWS system upgrades this assured makeup flow would not be available during the time frame that each NSWS loop is out of service. However this does not affect the operation of the system during the initial phase of a postulated accident.

During this time period the operable CVIWS train will be protected to the extent practical by minimizing any maintenance on the system for either unit. In this configuration, the operable train will still respond as designed during design basis events.

Page 5

AFW During this time period the operable AFW trains will be protected to the extent practical by minimizing any maintenance on the system for either unit. In this configuration, the operable trains will still respond as designed during design basis events.

CCw During this time period the operable CCW train will be protected to the extent practical by minimizing any maintenance on the system for either unit. In this configuration, the operable train will still respond as designed during design basis events.

The CCW trains are independent of each other to the degree that each has separate controls and power supplies and the operation of one does not depend on the other. In the event of a DBA, one CCW train is required to provide the minimum heat removal capability assumed in the safety analysis for the systems to which it supplies cooling water. In this Condition, the remaining operable CCW train is adequate to perform the heat removal function.

CRAVS During this time period the operable CRAVS train will be protected to the extent practical by minimizing any maintenance on the system for either unit. In this configuration, the operable train will still respond as designed during design basis events.

ABFVES During this time period the operable ABFVES train will be protected to the extent practical by minimizing any maintenance on the system for either unit. In this configuration, the operable train will still respond as designed during design basis events.

EDGs During the NSWS project, the NSWS supply to one EDG on each unit will be inoperable. A temporary Engineering Change will be implemented for the EDGs on each unit without their NSWS supply to supply an alternate, non-safety related, source of cooling to the EDG with the inoperable NSWS supply. The EDG will be considered inoperable, but it will be technically capable of being manually started to perform its intended function.

Page 6

During this time period the operable EDG will be protected to the extent practical by minimizing any maintenance on the system for either unit. In this configuration, the operable train will still respond as designed during design basis events.

• Defenses against potential common cause failures are maintained and the potential for introduction of new common cause failure mechanisms is assessed.

Defenses against common cause failures are maintained.

The extended AOT for each NSWS train requested is not sufficiently long to expect new common cause failure mechanisms to arise. In addition, the operating environment for these components remains the same so; again, new common cause failures modes are not expected. In addition, backup systems are not impacted by this change and no new common cause links between the primary and backup systems are introduced.

Therefore, no new potential common cause failure mechanisms have been introduced by the proposed change.

• Independence of barriers is not degraded.

The barriers protecting the public and the independence of these barriers are maintained. Multiple systems will not be taken out of service simultaneously that could lead to degradation of these barriers and an increase in risk to the public. During each NSWS header outage, the redundant train of equipment will remain operable and capable of performing its intended function. In addition, the extended AOT for each NSWS train does not provide a mechanism that degrades the independence of the barriers, fuel cladding, reactor coolant system, and containment.

• Defenses against human errors are maintained.

Administrative controls have been implemented to reflect the contingency measures that are being established. The increase in the AOT for each NSWS header outage will provide the necessary time to implement system upgrades which include activities associated with cleaning, inspection, and coating of NSWS piping welds, and necessary system repairs, replacement, or modifications. This will reduce time pressure during this project which will facilitate improved operator and maintenance personnel performance Page 7

resulting in reduced system alignments and assembly errors.

Performing the work with both units at 100% power allows more flexibility in scheduling around inclement weather periods and allows for more focused management and site attention. Thus, the whole site can be focused on this project as opposed to several projects that are typically occurring during a refueling outage.

It is concluded that defense-in-depth was not impacted by the proposed changes.

4.6 Evaluation of Risk Impact Duke Power has used a risk-informed approach to determine the risk significance of taking a loop of NSWS out of service for up to 11 days beyond its current TS limit of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. The acceptance guidelines given in the EPRI PSA Applications Guide were used as a gauge to determine the significance of the short-term risk increase from the outage extension.

The current PRA model was used to perform the risk evaluation for taking a train of NSWS out of service beyond its TS limit. The quantification has taken into account the following specific conditions:

• No discretionary maintenance is planned for risk significant components such as AFW, RHR, NV, CCW, 4160V ac power, DGs, and the SSF.

• Historically, the major source of flooding in the Turbine Building has been the Condenser Circulating Water (RC) System. Flood walls have recently been installed in the Turbine Building to protect the station transformers that feed the 4160 volt busses (SATA, SATB, 1(2) ATC, and 1(2) ATD). In the current model, the flood initiator as currently defined would be eliminated; however, some new less severe flooding events may be created. The impact of turbine building flooding given the new walls has been included in the assessment. In addition, to help reduce any potential flooding issues, it is assumed that the Condenser Circulating Water System will have no planned discretionary maintenance.

Page 8

In addition, other compensatory measures are credited to reduce the overall risk during the NSWS AOTs. Previous analyses indicated that the dominant accident sequences involved a loss of normal power to the operable 4160V ac bus. To mitigate the risk of a potential core damage event, operators would be dispatched to throttle key Auxiliary Feedwater valves to supply the flow to the steam generators prior to the depletion of the vital batteries. Furthermore, with the CCW system in cross-train alignment, operators would be instructed to align the available CCW pumps in the maintenance train through the CCW heat exchanger corresponding to the train without power. This would provide cooling to a CCW essential header.

The estimated increase in the core damage probability (CDP) for Catawba during the NSWS loop outage ranges from 9.8E-07 for a 2-day extension up to 5.8E-06 for an 11-day extension.

The impact to the seismically-induced core damage risk was also considered. The resulting increase in the conditional core damage probability (CCDP) was much less than the non-seismic portion and therefore has no impact on the overall results. In the seismic PRA model, the NSWS components and piping are considered to be seismically-rugged (since they are rated at a >2g seismic capacity) and the electrical systems thus become the only failure mechanism. Given that the DGs and switchyard will be available during the piping replacement, there are no new failure modes introduced and consideration of the seismic impact is not a factor for this assessment.

It is also recognized that reductions in risk can be achieved by the consideration of several other non-quantifiable risk reduction factors:

• Based upon a review of the cut sets, a substantial portion of the accident sequences involve a loss of 4160V ac power, NSWS or CCW. Therefore, it would be prudent for the operators to review the loss of power, loss of NSWS and loss of CCW procedures as well as perform extra rounds on the CCW System.

• No maintenance or testing should be performed on the offsite power system (switchyard). The operability of required offsite circuits should also be maintained. These actions would reduce the likelihood of losing off site power and therefore reduce risk.

Page 9

• Note that the peak season for tornadoes tends to be in the spring and the peak season for thunderstorms tends to be in the summer. Since the incidence of severe weather would be greater than at other times of the year, the risk of a LOOP during these time periods is also greater. (The PRA uses a yearly average initiating event frequency.) The NSWS piping AOTs are scheduled to be performed during a time of the year when severe weather is not normally an issue; hence, the risk of a severe weather-related LOOP is minimized. (It is noted, however, that the site has developed contingency plans to react as needed to unforeseen weather changes.)

• Entry into and operation of shutdown cooling is not without risk and involves significant plant manipulations and evolutions on both the primary and secondary side by Operations personnel. This risk is averted by remaining at power.

The change in the conditional large early release probability (CLERP) was also evaluated. The estimated increase in the large early release probability for Catawba during the NSWS loop outage ranges from 2.9E-08 for a 2-day extension up to 1.9E-07 for an 11-day extension. It is concluded that the large early release probability (LERP) implications of the extended LCO are not significant.

The core damage frequency contribution from the proposed outage extension is judged to be acceptable for a one-time, or rare, evolution. As stated above, the estimated increase in the core damage probability for Catawba during the NSWS loop outage ranges from 9.8E-07 for a 2-day extension up to 5.8E-06 for an 11-day extension. These are low-to-moderate increases in the CDP for consideration of temporary changes to the licensing basis and are acceptable based on consideration of other non-quantifiable factors discussed previously.

Page 10

4.7 Summary The "A" & "B" train NSWS pipe cleaning and weld coating project and the proposed temporary changes to TS 3.5.2, 3.6.6, 3.6.17, 3.7.5, 3.7.7, 3.7.8, 3.7.10, 3.7.12, and 3.8.1 have been evaluated to assess their impact on the normal operation of the affected systems and to ensure that the design basis of these functions are preserved.

The requested period of 14 days (336 hours0.00389 days <br />0.0933 hours <br />5.555556e-4 weeks <br />1.27848e-4 months <br />) for completing the Required Action is reasonable considering the redundant capabilities of the system, the proposed contingency measures that will be taken as discussed in section 4.3 of this Enclosure, the additional plant systems discussed in section 4.5 of this Enclosure, and the risk considerations discussed in section 4.6 of this Enclosure.

Therefore, for the ECCS, CSS, AFW, CCW, NSWS, and EDG systems, the requested extension of the Required Action time from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 336 hours0.00389 days <br />0.0933 hours <br />5.555556e-4 weeks <br />1.27848e-4 months <br /> is acceptable.

Therefore, for the CVIWS, CRAVS, and ABFVES systems, the requested extension of the Required Action time from 168 hours0.00194 days <br />0.0467 hours <br />2.777778e-4 weeks <br />6.3924e-5 months <br /> to 336 hours0.00389 days <br />0.0933 hours <br />5.555556e-4 weeks <br />1.27848e-4 months <br /> is acceptable.

Page 11