ML103120455

Response to Request for Additional Information Concerning - Technical Specifications Change WBN-TS-09-16 - Main Control Room Chiller Completion Time Extension

ML103120455
Person / Time
Site:	Watts Bar
Issue date:	11/05/2010
From:	Krich R Tennessee Valley Authority
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
TAC ME3429, WBN-TS-09-16
Download: ML103120455 (12)

Text

Tennessee Valley Authority 1101 Market Street, LP 3R Chattanooga, Tennessee 37402-2801 R. M. Krich Vice President Nuclear Licensing November 5, 2010 10 CFR 50.90 ATTN: Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Watts Bar Nuclear Plant, Unit 1 Facility Operating License No. NPF-90 NRC Docket No. 50-390

Subject:

Response to Request for Additional Information Concerning -

Technical Specifications Change WBN-TS-09 Main Control Room Chiller Completion Time Extension (TAC No. ME3429)

References:

1. Letter from TVA to NRC, "Watts Bar Nuclear Plant Unit 1 - Technical Specification Change - Main Control Room Chiller Completion Time Extension," dated February 24, 2010

2. Letter from NRC to TVA, "Watts Bar Nuclear Plant, Unit 1 - Request for Additional Information Regarding The Proposed Allowed Outage Time One-Time Extension for the Chiller Upgrade Project (TAC No. ME3429)," dated October 8, 2010 By letter dated February 24, 2010 (Reference 1), the Tennessee Valley Authority (TVA) submitted a license amendment application to revise the Watts Bar Nuclear Plant (WBN),

Unit 1 Technical Specifications (TS) to allow a one-time extension of the Completion Time in Technical Specification 3.7.11, "Control Room Emergency Air Temperature Control System (CREATCS)." The change was proposed to be applicable during plant modifications to upgrade the CREATCS chillers. By letter dated October 8, 2010 (Reference 2), the NRC requested that additional information be submitted to support their review of the license amendment application. Enclosure 1 provides the TVA responses to the NRC requests for additional information provided in Reference 2. Enclosure 2 provides revisions to the proposed TS and TS Bases pages.

printed on recycled paper

U.S. Nuclear Regulatory Commission Page 2 November 5, 2010 In Reference 1, TVA requested approval of the proposed TS change by December 1, 2010 to support chiller on-line modification activities. As a result of a change in the schedule for commencing Phase 1 activities, TVA now requests approval of this TS change by February 18, 2011.

TVA has determined that the additional information provided by this letter does not affect the no significant hazards considerations associated with the proposed TS changes. The proposed TS changes still qualify for a categorical exclusion from environmental review pursuant to the provisions of 10 CFR 51.22(c)(9).

There are no commitments associated with this letter. If you have any questions about this change, please contact Kevin Casey at (423) 751-8523.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on the 5th day of November, 2010.

~ctfly, R. M. Krich 4

Enclosures:

Enclosure 1 - Response to NRC Request for Additional Information Concerning Technical Specifications Change WBN-TS-09-16 -Watts Bar Nuclear Plant, Unit 1 -

Technical Specifications Change - Main Control Room Chiller Completion Time Extension Enclosure 2 - Proposed Technical Specifications Changes (Mark-up) cc (Enclosures):

Regional Administrator - Region II NRC Senior Resident Inspector - Watts Bar Nuclear Plant Director, Division of Radiological Health - State of Tennessee

ENCLOSURE1 RESPONSE TO NRC REQUEST FOR ADDITIONAL INFORMATION CONCERNING TECHNICAL SPECIFICATIONS CHANGE WBN-TS-09-16 -WATTS BAR NUCLEAR PLANT, UNIT I - MAIN CONTROL ROOM CHILLER COMPLETION TIME EXTENSION NRC Question 1 In your applicationdated February24, 2010, the Note associatedwith TS 3.7.11 could potentially allow one CREA TCS train to be taken out of service multiple times. Do you intend to remove one CREA TCS train from service multiple times? If not, please revise the Note to limit each train to be out of service one time only.

TVA Response TVA intends to perform the replacement of the Main Control Room (MCR) chillers in phases as described in the Sections 2.1.1 - 2.1.3 of the License Amendment Request (LAR). Each phase of MCR chiller replacement (Phase 2 and 3) will require an entry in the associated Technical Specifications 3.7.11 Condition. The proposed 60-day completion time was evaluated to provide sufficient time to complete the detailed removal and replacement activities with some margin for contingencies as described in Section 3.1.2 of the LAR. The 60-day Completion time was proposed to allow for a single Technical Specification Condition entry for each of the affected MCR chiller replacement phases.

More practically, the demolition and replacement activities do not allow for the system to be restored to an operable status without completion of the Post Modification Testing (PMT) in each phase. The PMT can only be completed at the full completion of the demolition and reinstallation activities. Thus, multiple entries into the TS Condition for any one phase of the project are not feasible.

As a result of minor shifts in the schedule for the modification, TVA now requests approval of this TS change by February 18, 2011. The start and end dates referenced in the Note has also been revised from December 1, 2010 to March 1, 2011, and January 29, 2012 to April 30, 2012, respectively, due to this schedule change.

In response to RAI Question 1, TVA has modified the proposed Note to TS 3.7.11 to read:

An allowance is permitted for one CREA TCS train to be inoperablefor 60 days. This TS provision is only authorizedfor one entry per train during modification activities planned for the upgrade of the MCR chillers beginning no earlierthan March 1, 2011 and ending April 30, 2012, and provided compensatory measures are implemented. provides the revised TS pages and TS Bases pages. The TS and TS Bases pages submitted in this enclosure supersede in their entirety those submitted in Enclosure 2 of Reference 1.

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NRC Question 2 Section 1.0 (4th paragraph)indicates that one main control room (MCR) chiller train can maintain the ambient temperature in the MCR and its associatedspaces below their design limit (less than 104 OF). Section 2.1.2 (1st paragraph)indicates that the temporary chilled water package will also maintain the personnel comfort temperatureless than or equal to 90°F.

Section 3.2 (1st paragraph)makes a reference to WBN CalculationMDQ00003120090157and states that "The calculation concluded that with the initial ambient temperatureat 75°F, it would take at least 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br /> upon the loss of cooling before the maximum environmental temperature of 104°F would be exceeded in the MCR." From this statement, it appears that the MCR cooling system normally maintainsthe MCR at 75°F. Since the nominal rating of the temporary chiller is considerably largerthan the loss-of-coolant accident (LOCA) heat load (as indicated in Section

3. 1.4, Table 4), it also appears that the temporary chilled water system can maintain the control room below all the temperature criteriadiscussed above. Table I also references a calculated room temperature of less than 85°F with the temporary equipment. Please provide a perspective of all the different temperatures noted above and clarify if the temporary chilled water system is capable of fulfilling all the cooling functions of the permanent system.

TVA Response The Control Building HVAC systems are designed to maintain temperature and humidity conditions throughout the Control Building for the protection, operation, and maintenance and testing of plant controls, and for the safe, uninterrupted occupancy of the MCR habitability system area during an accident and subsequent recovery period.

As described in Section 9.4.1 of the WBN Updated Final Safety Analysis Report (UFSAR), the Control Building HVAC system includes the MCR air conditioning system as well as HVAC systems for other portions of the Control Building. (The MCR Air Conditioning system discussed in the FSAR includes the systems and components, and provides the functions, described in the Technical Specification Bases as the Control Room Emergency Air Temperature Control System (CREACTS).) The MCR (CREACTS) air conditioning chillers are being replaced as part of this project. During the period of time that the permanent MCR chiller is being removed and replaced, the temporary chiller package described in the LAR will be connected and available to be placed into service should the remaining in-service permanent chiller train fail or become degraded.

The design of the Control Building HVAC systems is to maintain air conditioned equipment spaces and normally occupied personnel spaces in the range of 60'F minimum to 104 0 F maximum during all modes of operation. In sizing the temporary chiller system, TVA elected to size the system such that it had the capacity to maintain main control room habitability zone temperatures less than the design basis limit of 104 0 F and also maintain personnel comfort temperature less than or equal to 90°F (which is based on TVA Safety Manual, Procedure 806, "Heat Stress" as further discussed in the LAR). To demonstrate that these design objectives could be achieved, TVA performed calculations (discussed in Section 3.1.4 of the LAR) which considered LOCA heat loads, the nominal rating of the temporary chiller system and nominal temporary chiller water pump ratings. This calculation concluded that room temperatures would remain below 85°F, thus meeting design objectives.

The LAR also provided a perspective of what would be the consequences of the failure of the HVAC systems under accident conditions. The referenced temperature transient analysis shows E1-2 of 6

that if both trains of safety-related HVAC fail and a LOCA occurs, the estimated time to reach the design basis limit (104 0 F) is approximately 7 hours8.101852e-5 days <br />0.00194 hours <br />1.157407e-5 weeks <br />2.6635e-6 months <br />.

NRC Question 3 Please explain if the temporary chilled water system for the MCR has any impact on the control room habitability. Include in your response, a discussion of the control room envelope boundary, control room emergency filtration system and post-accident radiologicalprotection, fire and flood, and how they might be impacted. Also, include a discussion on the precautions taken to protect other equipment in the plant from fire, physical damage, movement of portable equipment, etc. during construction activities.

TVA Response The main control room habitability zone (MCRHZ) (also referred to as the main control room habitability system area or MCRHS area) is described in Section 6.4.1 of the WBN UFSAR. It is the envelope of spaces which are maintained habitable by pressurization to 1/8 inch water gage above atmospheric to minimize infiltration of airborne contaminants. The MCRHZ includes all rooms on the plan Elevation 755 of the Control Room Building. All rooms to which MCR personnel may require access during emergency operations are included within this envelope.

The specific rooms in the MCRHZ are discussed in UFSAR Section 6.4.2.1.

The control room envelope is unaffected by this temporary chilled water system. No new penetrations are added; no air handling unit characteristics are changed; no air flows are changed; and no ductwork is impacted. No changes are made to the control room emergency ventilation system. The temporary chilled water connection to the safety related air handling unit simply changes the source of the chilled water. There are no impacts to post accident dose analyses.

The only temporary equipment in the plant is the flexible hoses, pipe, fittings, and valves. The hoses, pipe, and fittings are qualified for adequate pressure to protect against rupture and pipe whip. The valves at the penetrations are qualified for seismic retention to maintain the integrity of the MCRHZ. A transient combustible loading evaluation has been performed and verifies the fire severity indices of the spaces are not impacted by the temporary hose material. Spill containment is provided beneath the chiller skid to contain any spillage from the chiller skid.

The temporary equipment is located the required safe distance from permanent plant equipment and structures in the yard.

NRC Question 4 There is a statement in the second paragraphof Section 3.1.3, "CompensatoryMeasures"that reads "Qualifiedpersonnel will be provided with informal training on these instructions." Explain the difference between "informaltraining"and any other types of trainingat WBN Unit I and provide yourjustification why "informaltraining"is deemed to be adequate,keeping in context that the temporary cooling equipment performs important safety-relatedfunction if it is called upon to operate during post-accident conditions.

TVA Response The training that will be provided for the operation of the temporary chiller system will be conducted by task supervisors and field engineers and will use appropriate material including E1-3 of 6

vendor manuals, start-up procedures, work instructions, and OJT (On The Job) training. This training will be documented in the associated work instruction package. This type of training (which was what the term "informal" used in the LAR referred to) is used routinely and successfully for a range of important maintenance activities across the site and is thus deemed adequate for the chiller replacement project. This approach to training is contrasted with training activities for which TVA has established specific qualification numbers, lesson plans, and tracking via TVA's enterprise wide training tracking system (referred to as ATIS).

NRC Question 5 The statement in Requirement 2 under Section 3.1.3 indicates that qualified personnel will be stationedin the area whenever the valves are in the "Open"position and the temporary cooling system is in service. Confirm that qualified personnel will be stationed throughout the 60-day period,even when the temporary system is not operating during this period. Also, provide details about the additionalareas where qualified personnel will be stationed and the purpose of theirpresence during this period.

TVA Response Qualified personnel will be onsite during the 60-day period; however, they will not be stationed at the penetration locations unless the valves are open and the system is operating.

Qualified personnel will not be stationed at the isolation valves and temporary chiller when it is not operating, but will be onsite with communication devices (with the control room) and they will be briefed daily on their duties.

Additional plant staff will be stationed to monitor for leaks and other abnormalities any time the temporary chiller is in service. Supervisors will also be notified of the need for the temporary chiller and will be overseeing all temporary chiller activities.

NRC Question 6 The statement in Requirement 4 under Section 3.1.3 states that no planned maintenance activity, except for Surveillance Requirements (SRs) 3.8.1.2, 3.8.1.3, and 3.8.1.7, that could impact the operability of the diesel generators(DGs) that provide emergency power to the operable MCR chiller train will be performed. Based on TS 3.7.11, Condition A, if the only qualified MCR cooling system available during the 60-day period becomes inoperable, WBN Unit I will enter limiting condition of operation (LCO) 3.0.3 immediately. If the DG SRs result in immediate maintenance to the DGs, explain the impact on the operability of the MCR cooling system in TS 3.7.11. Include in your response, any other systems that support the MCR cooling system and how theirmaintenance or surveillance could also impact TS 3.7.11.

TVA Response If SR 3.8.1.2, "DG Auto Start," SR 3.8.1.3, "DG Load Capacity Test," or SR 3.8.1.7, "DG Fast Auto Start," is in progress, the affected MCR chiller train would remain OPERABLE provided that two qualified offsite circuits are available. This is based on the TS Definition for "OPERABLE-OPERABILITY," which states, in part, that a system, subsystem, train, component, or device is OPERABLE provided that normal or emergency electrical power are also capable of performing their related support function(s). The qualified offsite circuits are the normal electrical power source for the MCR chillers.

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If one offsite power source is lost, the plant would enter LCO 3.8.1, Required Action A.2, "Declare required features(s) with no offsite power available inoperable when its required redundant feature(s) is inoperable." The required feature in this case is the MCR chiller in service and since the redundant MCR chiller is out-of-service due to replacement activities, the Completion Time for Required Action A.2 would require that the affected MCR train be declared inoperable within 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> if an offsite power source cannot be restored for the MCR chillers.

TS 3.7.11, Required Action E, would subsequently require that the plant enter TS 3.0.3 immediately. (In the event of a loss of one offsite power source, the plant would, of course, review TS requirements for all TS features and take all required actions.)

If the Diesel Generator (DG) surveillance results in immediate maintenance to the DG that provides backup power to qualified MCR chiller that is in service, the qualified MCR chiller is OPERABLE provided that offsite power is available. However, for this condition the plant would also enter LCO 3.8.1, Required Action B.2, "Declare required features(s) supported by the inoperable DG inoperable when its required redundant feature(s) is inoperable." The required feature in this case is the MCR chiller in service and since the redundant MCR chiller is out-of-service due to replacement activities, the Completion Time for Required Action B.2 will require that the plant declare the in service MCR chiller inoperable within 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br />. Subsequent to declaring the in-service MCR chiller inoperable, the plant would~enter TS 3.7.11, Required Action E, which would require that the plant enter TS 3.0.3 immediately.

Maintenance or surveillance on any other TS support systems for the in-service MCR chiller such as the ERCW supply that results in the inoperability of the in-service MCR chiller will require the plant to evaluate the impact on safety function in accordance with LCO 3.0.6 and TS Section 5.7.2.18, Safety Function Determination Program (SFDP) as described in Section 3.4 of the LAR.

NRC Question 7 The shutdown board room (SDBR) cooling system is not a TS support system. However, in Section 4.1, "Applicable Regulatory Requirements/Criteria,"there is a reference made to 6.9 KiloVolts (kV) SDBR TSs. Further,in Section 2.1.3 "Phase3 SDBR ChillerA and MCR ChillerA Replacement," it is stated that "If train-B SDBR chiller were to fail during installation of the new train-A SDBR chiller package, the plant will evaluate the impact and enter the appropriateTS action if required." Please explain how the 6.9 kV SDBR or any other TSs is impacted by the SDBR cooling system failures. Include in your response, a discussion of the processes in place that would lead you from the time the failures are discovered to when the determinationis made that TSs are impacted.

TVA Response The SDBR chillers are a non-TS support system with two 100% capacity subsystems. The chillers are designed such that one chiller can maintain the environmental conditions (humidity and ambient temperature) for the supported systems (i.e., Class 1E Distribution System Train A and B) within design limits for all DBAs. Loss of one support train does not result in a loss of safety function for the supported systems. However, in this situation, the supported systems (i.e., Class 1 E switchgears, motor control centers, distribution panels, cables, instrumentation, etc.) are vulnerable due to failure of the support system to meet the single failure criteria. To compensate for this potential failure mode, TVA performs a risk assessment in accordance with Section (a)(4) of the Maintenance Rule (MR) to determine the appropriate risk-informed Allowed E1-5 of 6

Outage Time (AOT) for one support train inoperable. (An NRC evaluation of this approach was documented in a letter from NRC to First Energy Nuclear Operating Company, "Application of Generic Letter 80-30 Guidance to an Inoperable Non-Technical Specification Support Subsystem," dated April 5, 2002.) A risk-informed AOT would be reflective of the existing plant configuration which is subject to change based on emergent plant conditions. Based on the AOT estimate provided in the license amendment request, the risk-informed AOT for the SDBR chillers will have a duration of 60 days.

In the event that both trains of the SDBR chillers were to become inoperable during Phase 1 or Phase 3, the plant will conduct an operability evaluation of the supported Shutdown Boards in accordance with the guidance in NRC Inspection Manual 9900. If the evaluation determines that the Shutdown Boards are inoperable, the plant will enter LCO 3.8.9, Condition E. Condition E requires that the plant enter LCO 3.0.3 immediately whenever two trains with one or more inoperable distribution subsystems result in a loss of safety function.

NRC Question 8 The temporary chillers will be located outside in the yard. The License Amendment Request did not provide any discussion on how the plant deals with adverse weather conditions such as thunderstorms,tornado watches or tornado warnings, hurricanes,high winds, etc. Provide a discussion of how the temporary equipment could be affected under these conditions, and the processes in place at WBN Unit I to address these conditions, and how the temporary equipment is protected and downtime minimized.

TVA Response The temporary chiller, chilled water pump, and diesel generator will be skid-mounted to a flat bed trailer in the yard. The equipment is designed for outside installation. No additional weather protection is planned for this equipment, as it is designed for outdoor installation. Missile protection is not provided. The hoses are to be constrained every 50 feet to prevent pipe whip and protected from foot traffic. Caution markers will also be used in the vicinity.

The temporary chiller equipment is intended as a measure to mitigate the risk (assessed in a qualitative manner as described in the LAR) associated with the extended period of time required to replace the MCR chiller trains and thus provide a basis for the requested 60-day TS Completion time. The temporary chillers are not proposed as safety-related substitutes for the permanent MCR chillers. Consequently, TVA did not propose that the temporary chillers be allowed to substitute in the existing TS Condition for one inoperable CREACTS train. Thus, for the one time extension, the installation of the temporary chiller system, without the application of all safety related design criteria associated with weather and missile protection, is appropriate.

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ENCLOSURE 2 TENNESSEE VALLEY AUTHORITY (TVA)

WATTS BAR NUCLEAR PLANT, UNIT 1 WBN TS-09-16 PROPOSED TECHNICAL SPECIFICATION (TS) CHANGES (MARK-UP)

AFFECTED PAGE LIST TS page 3.7-25 Bases pages B 3.7-59 and B 3.7-59a MARKED PAGES See attached.

Note: Additions are shown in bold italics.

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3.7 PLANT SYSTEMS 3.7.11 Control Room Emergency Air Temperature Control System (CREATCS)

LCO 3.7.11 Two CREATCS trains shall be OPERABLE.

APPLICABILITY: MODES 1, 2, 3, 4, 5, and 6 During movement of irradiated fuel assemblies.

ACTIONS CONDITION REQUIRED ACTION COMPLETION TIME A. One CREATCS train A. 1 Restore CREATCS train to 30 days*

inoperable. OPERABLE status.

B. Required Action and associated B.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 /> Completion Time of Condition A not met in MODE 1, 2, 3, or 4. AND B.2 Be in MODE 5. 36 hours4.166667e-4 days <br />0.01 hours <br />5.952381e-5 weeks <br />1.3698e-5 months <br /> C. Required Action and associated C.1 Place OPERABLE CREATCS Immediately Completion Time of Condition A train in operation.

not met in MODE 5 or 6, or during movement of irradiated OR fuel assemblies.

C.2 Suspend movement of irradiated fuel assemblies. Immediately (continued)

• An allowance is permitted for one CREA TCS train to be inoperablefor 60 days. This TS provision is only authorized for one entry per train during modification activities planned for the upgrade of the MCR chillers beginning no earlierthan March 1, 2011 and ending April 30, 2012 and provided compensatory measures are implemented.

Watts Bar-Unit 1 3.7-25 E2-2 of 4

CREATCS B 3.7.11 BASES APPLICABLE heat loads from the control room, which include consideration of equipment SAFETY ANALYSES heat loads and personnel occupancy requirements, to ensure equipment (continued) OPERABILITY (Ref. 3).

The CREATCS satisfies Criterion 3 of the NRC Policy Statement.

LCO Two independent and redundant trains of the CREATCS are required to be OPERABLE to ensure that at least one is available, assuming a single failure disabling the other train. Total system failure could result in the equipment operating temperature exceeding limits in the event of an accident.

The CREATCS is considered to be OPERABLE when the individual components necessary to maintain the control room temperature are OPERABLE in both trains. These components include the chillers, AHUs, and associated temperature control instrumentation. In addition, the CREATCS must be operable to the extent that air circulation can be maintained.

APPLICABILITY In MODES 1, 2, 3, 4, 5, and 6, and during movement of irradiated fuel assemblies, the CREATCS must be OPERABLE to ensure that the control room temperature will not exceed equipment operational requirements following isolation of the control room.

In MODE 5 or 6, CREATCS is required during a control room isolation following a waste gas decay tank rupture.

ACTIONS A.1 With one CREATCS train inoperable, action must be taken to restore OPERABLE status within 30 days. In this Condition, the remaining OPERABLE CREATCS train is adequate to maintain the control room temperature within limits. However, the overall reliability is reduced because a single failure in the OPERABLE CREATCS train could result in loss of CREATCS function. The 30 day Completion Time is based on the low probability of an event requiring control room isolation, the consideration that the remaining train can provide the required protection, and that alternate safety or nonsafety related cooling means are available.

(continued)

Watts Bar-Unit 1 B 3.7-59 Revision 64 Amendment 50 E2-3 of 4

ACTIONS A.1 (continued)

During modification activities to replace the CREA TCS chillers, an allowance is permittedfor one CREA TCS train to be inoperablefor 60 days provided the following compensatory measures are in place:

A temporarychilled water package,will be installed and maintainedin a "standby" condition. During the initial installation,the chillerskids and chilled waterpumps will be stationed in the yard with the chilled water lines filled and vented at the manifolds in the Control Building Mechanical Equipment Room located on Elevation 755.0 and the Shutdown Board Room Mechanical Equipment Rooms located on Elevation 757.0. Final connection of the chilled waterhoses to the SDBR or MCR AHUs will not occur until that particularHVAC train is taken out of service for chiller replacement. All necessary hardware, hoses, and fittings will be stationedat the AHUs for rapid deployment in order to connect, fill and vent the temporary chilled water hoses to the AHUs. Procedureswill be provided as part of Work Order documents to include instructionsfor startup, operation,preventative maintenance, and shutdown of the temporary cooling equipment.

Qualified personnel will be provided training on these procedures.

Furthermore,to provide additionaldefense-in-depth, the following requirements would also be implemented:

1. If a temporary chilled water system hose breaks in the Control Building during the timeframe that the temporary equipment is installed,the two manual isolationball valves located at the MCRHZ boundary will be closed immediately. Qualifiedpersonnel will be capable of closing the valves and will be stationedin the area whenever the valves are in the "Open" position and the temporary cooling system is in service.

2. If a temporary chilled water system hose breaks in the Auxiliary Building or Shutdown Board Room during the timeframe that the temporary equipment is installed,the manual isolation valves will be closed immediately. Qualifiedpersonnel will be capable of closing the valves and will be stationedin the area whenever the valves are in the "Open" position and the temporary cooling system is in service.

3. Due to lack of operatingdata, the availabilityor reliabilityof the new MCR chillerpackages are unknown. To compensate for this uncertainty the new train-B chiller packages will be operated for a minimum of 2 weeks priorto removing the train-A MCR chillers from service for replacement.

4. During replacementof the MCR chillers, no plannedmaintenance activity, except for SRs 3.8.1.2, 3.8.1.3, and 3.8.1.7, that could impact the OPERABILITY of the DG's that provide emergency power to the OPERABLE MCR chiller train will be performed.

This TS provision is only authorizedfor one entry per train during modification activities planned for the upgrade of the MCR chillers beginning no earlierthan March 1, 2011 and ending April 30, 2012.

(continued)

Watts Bar-Unit 1 B 3.7-59a E2-4 of 4