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LAR 99-19 for License NPF-86,increasing AOT for Cracs from 30 Days to 60 Days on One Time Basis for Each Train to Facilitate on-line Implementation of Design Enhancements During Current Operating Cycle
	ML20196G353
Person / Time
Site:	Seabrook
Issue date:	06/23/1999
From:	Feigenbaum T; NORTH ATLANTIC ENERGY SERVICE CORP. (NAESCO)
To:	;
Shared Package
ML20196G342	List: ML20196G338; ML20196G353; ML20196G367;
References
	NUDOCS 9907010134
	Download: ML20196G353 (7)
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.s This License Amendment Request is submitted by North Atlantic Energy Service Corporation pursuant to 10CFR50.90. The following information is enclosed in support of this License Amendment Request:

. Section I - Introduction and Safety Assessment for Proposed Change i

. Section 11 - Markup of Proposed Change

. Section lli - Retype of Proposed Change

. Section IV -

Determination of Significant Hazarde for Proposed Change

. Section V - Proposed Schedule for License Amendment issuance and Effectiveness

. Section VI - EnvironmentalImpact Assessment The information and statements contained within this License Amendment Request are bcsed on facts and circumstances which are true and accurate to the best of my knowledge and belief.

Sworn and Subscribed befgre io me thisdayof bl/I@.1999 ~ '

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> Jh 6 Mb "M4Q Ted '.Feigenbaun[

V 4~ Notary Public Exect. live Vice President and Chief Nuclear Officer 9907010134 990623 PDR ADOCK 05000443 P PDR

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l Section I I

Introduction and Safety Assessment for the Proposed Change :

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r 1 L INTRODUCTION AND SAFETY ASSESSMENT OF THE PROPOSED CHANGE A. Introduction License Amendment Request (LAR) 99-19 proposes addition of a note to the Seabrook Station Technical Specification (TS) 3.7.6.2 to extend, on a one time basis (per train), the allowable outage time (AOT) with one Control Room Air Conditioning Subsystem (CRACS) inoperable from 30 days to 60 days. This change is necessary in order to facilitate the implementation of design enhancements that will improve maintainability and reliability of the safety-related CRACS. Also proposed is an exception to the requirements of TS 3.0.4 and Surveillance Requirement (SR) 4.0.4 as they apply to TS 3.7.6.2 during the implementation of the modification to the CRACS.

B. Proposed Specifications To Be Revised 3.7.6.2 Control Room Subsystems Air Conditioning C. Safety Assessment i J

BACKGROUND The functions of the CRACS are to provide a controlled environment inside of the control room complex I to ensure the comfort of the plant operatora and to ensure adequate climate conditions for the operability of equipment. The CRACS is designed to handle 100% of the heat load postulated for a design basis accident and is expected to run on demand for a period of 30 days following an accident.

The CRACS consists of two independent safety-related air conditioning subsystems (trains) that provide cooling of recirculated control room air. Availability of the CRACS is necessary on a continuous 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months per day basis during all modes of plant operation in order to comply with the requirements of Technical Specification 3.7.6.2.

The original plant design of the CRACS included only two safety-related refrigerant trains. Each train consists of an electric motor driven refrigerant compressor, an air-cooled refrigeration condensing coil with an electric motor-driven centrifugal fan. and a direct expansion evaporator with an electric motor-driven centrifugal fan. The continuous duty requirement for the CRACS has necessitated a significant amount of maintenance for refrigeration system components in the safety-related trains and had been the cause of two unplanned plant shutdowns. These shutdowns were identified in Licensee Event Reports (LERs)97-018 and 98-006. The safety-related trains are American Nuclear Society Safety (ANS) Class 3, Seismic Category 1.

l In order to reduce the operational load on the safety-related refrigerant trains and to improve overall l CRACS reliability, a non-safety-related chilled water subsystem has been installed. The non-safety- l related chilled water system includes two chiller units, two chilled water pumps, two air cooling coils, an l expansion tank, valves and associated controls and instrumentation. The non-safety-related subsystem is designated as non-nuclear safety-related (NNS). Piping and valves located within the Control Building are designed and installed in accordance American National Standards Institute (ANSI) standard B31.1 l with Regulatory Guide 1.29 seismic supports (Seismic Category NNS-1). Piping and valves located on the Non-Essential Switchgear Building roof, and in the Administration Building and the Administration Building's Mechanical Equipment Room 18 are classified as non-seismic and are designed and installed Page 2

in accordance with ANSI B31.1. Expansion and air separator tanks are designed and fabricated to ASME Section Vill. There are no Technical Specifications associated with the operation of the non-safety-related chilled water subsystem.

A new plant design is under development to delete the existing safety-related refrigerant subsystem and replace it with a safety-related chilled water system. The existing direct expansion refrigerant evaporators, refrigerant compressors, and condensers will be deleted from the new design. The direct expansion coils will be removed from the fan units and be replaced with safety-related chilled water coils.

Each independent train will be supplied chilled water from its own safety-related refrigerant chiller and pump.

The proposed plant design change to install a new safety-related chilled water system for the CRACS is a substantial task and will be performed on each train individually during separate AOT periods. North Atlantic has established a specific project team to manage and oversee the revised design of the system, procurement of components and installation and testing of the redesigned system. In order to permit installation of the re:ised design on an individual train basis, it is necessary that the associated installed safety-related train of CRACS be declared inoperable which requires entry into the applicable action requirements of Technical Specification 3.7.6.2.

In order to minimize the time required to install and test the redesigned system, North Atlantic plans to pre-stage certain design change implementation activities to the degrec possible. These activities include the prefabrication of pipe and pipe supports, the establishment of plant laydown areas for equipment, the installation of certain piping and supports, the installation of certain electrical equipment, and the delivery and testing of the replacement chiller units.

During the AOT period, it is expected that the following activities will be required to be performed to implement the design change:

Isolation and tagout of the applicable train and associated support components, e Electrical determination of refrigeration skid and associated components.

Evacuation of the refrigerant from the applicable train, i I

e Removal of condenser fan housing ducting, e Installation of the chiller, pumps and associated piping, e Completion of piping tie-in to the chiller and pump skid, 1 e Installation of chiller and pump skid power cable and termination work, o Performance of wiring verifications, e Removal of the existing evaporator coil piping and supports, e Removal of the existing evaporator housing, coil and frame,

Installation of a new chilled water coil, frame, coil piping and piping supports,

Fill of the new chilled water system with glycol, e Modification of existing duct supports, e Installation of new duct sections, supports, hood and fan,

Performance of system testing, and e Clearance of safety tags.

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I s Based upon the number and complexity of the activities described above (much of which will be done in series), it is expected that the present 30 day AOT period identified in Technical Specification 3.7.6.2 may be challenged during the implementation of this design change. The estimated completion time of these AOT period activities is approximately 19 days. This time estimate assumes that work will be performed on a 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months per day,7 days per week schedule. The requested 60 day AOT period is based on the uncertainty in the present implementation schedule, the potential work complications associated with implementing the modification for the first time and to provide the flexibility to implement the modification on each train in a controlled manner utilizing a less aggressive schedule.

North Atlantic will not enter the subject action statements to initiate installation of the design changes to CRACS unless the non-safety related chilled water subsystem is functional. Additionally, North Atlantic will not exercise the exceptions to TS 3.0.4 and SR 4.0.4 during implementation of the modification unless the non-safety related chilled water subsystem is functional.

DESCRIPTION OF THE TECHNICAL SPECIFICATION CHANGE REQUEST The operational requirements for the Control Room Air Conditioning Subsystems (CRACS) are contained in Technical Specification 3.7.6.2 " Control Room Subsystems Air Conditioning." This Limiting Condition for Operation (LCO) requires that two independent Control Room Air Conditioning 1 Subsystems (trains) be operable during all modes of operation. The LCO action statement for operational modes 1, 2, 3 and 4, with one Control Room Air Conditioning Subsystem (train) inoperable, states:

" restore the inoperable system to operable status within 30 days or be in at least Hot Standby [ Mode 3]

within the next 6 hours6.944444e-5 days 0.00167 hours 9.920635e-6 weeks 2.283e-6 months and in Cold Shutdown within the following 30 hours3.472222e-4 days 0.00833 hours 4.960317e-5 weeks 1.1415e-5 months ." The LCO action statement for operational modes 5 and 6 with one Control Room Air Conditioning Subsystem inoperable, states:

" restore the inoperable system to operable within 30 days or initiate and maintain operation of the j remaining OPERABLE Control Room Air Conditioning Subsystem or immediately suspend all J operations involving CORE ALTERATIONS or positive reactivity changes."

The proposed change adds the following note:"* For cycle 7, the allowable outage time may be extended to 60 days, on a one-time basis, for each train, to implement modifications to the control room air conditioning subsystems. The provisions of specifications 3.0.4 and 4.0.4 are not applicable during the implementation of modifications to the air conditioning subsystems."

This change is considered a one-time only change to Technical Specification 3.7.6.2 in order to facilitate the installation of a design change to the CRACS during the present operating cycle. This change will not affect the existing 30 day AOT period presently in place in Technical Specification 3.7.6.2. which requires specific actions in the event that the CRACS is determined to be inoperable for any other reason.

It has been detennined that since this change to the Technical Specification 3.7.6.2 is limited to periods when the design change is being implemented during the current operating cycle, no changes to the bases section B3/4. 7.6 " Control Room Subsystems" are necessary.

SAFETY ASSESSMENT:

The system description and safety analysis for the present safety-related CRACS are provided in section 9.4.1 of the Updated Final Safety Analysis Report. The control of temperature in the control room is achieved primarily by the CRACS. Each train of the safety related CRACS is conservatively sized to handle the worst heat load conditions. The actual heat load on the system can vary greatly. Temperature changes in the control room are gradual even under degraded conditions. Time is available and station i i

procedures exist to utilize alternate trains of the CRACS or alternate methods to cool the control room. In

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the unlikely event that alternate cooling methode "nnot maintain control room temperature, such that the l control room cannot be inhabited, the plant et w sr.atdown from the Remote Safe Shutdown Panel. The l proposed change to increase the AOT fror.. .w to 60 days for Technical Specification 3.7.6.2 is to be i I

utilized only during the present operating cycle, in order to facilitate the implementation of an extensive design change to delete the existing safety-related refrigerant subsystem and replace it with a safety-related chilled water system. Under normal circumstances, the existing 30 day AOT specified in Technical Specification 3.7.6.2 is a reasonable time frame to allow for the repair or maintenance of a CRACS train. However, based upon the number and complexity of the activities associated with the design change, it is expected that the 30 day AOT period identified in Technical Specification 3.7.6.2 may be challenged.

The original plant design of the CRACS included only two redundant, separated safety-related refrigerant trains. Each train consists of an electric motor driven refrigerant compressor, an air-cooled refrigeration condensing coil with an electric motor-driven centrifugal fan, and a direct expansion evaporator with an electric motor-driven centrifugal fan. The 24 hour2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months per day continuous duty requirements for the CRACS necessitated a significant amount of maintenance for refrigeration system components and reduced the long-term reliability of the system.

In order to reduce the operational load on the safety-related refrigerant trains and to improve overall CRACS reliability, a non-safety-related chilled water subsystem has been installed. Base load operation of the non-safety-related chilled water subsystem allows the two safety-related refrigerant trains to remain in the standby condition under normal plant conditions.

Removal of one of the safety-related trains of CRACS to implement the proposed design change to remove the existing safety-related refrigerant equipment and replace it with a safety-related chilled water equipment is a substantial task to perform within the existing 30 day AOT of Technical Specification 3.7.6.2. The existing direct expansion refrigerant evaporators, refrigerant compressors, and condensers will be removed upon implementation of the new design. The direct expansion coil will be removed from the fan unit and be replaced with a safety-related chilled water coil. Each independent train will be supplied chilled water from its own independent safety-related refrigerant chiller and pump.

Even though the proposed design involves a significant amount of work, the risk significance involved l with removing a safety-related train of the CRACS is extremely low based on the short period (60 days per train) and consequences of losing this function. The CRACS is excluded from modeling in the f

j Seabrook Station Probabilistic Risk Assessment (PRA) due to its extremely low risk significance. The i safety-related CRACS are support subsystems which control the temperature in the control room to assist in maintaining a habitable environment for personnel and to protect the equipment qualification of safety- j related components in the control room envelope. CRACS does not perform actions required to mitigate g the consequences of an accident.

The extended loss of the operating CRACS train, would result in a slow gradual rise in control room i temperature. The temperature of the control room is normally maintained between 70 to 72 F at the l discretion of the Unit Shift Supervisor utilizing a non-safety-related train of CRACS. In the event that j the control room temperature increased to a temperature greater than 75 F, plant procedures require l starting other equipment in the non-safety-related subsystem or a safety-related train of CRACS to restore ;

control room temperature to its normal operating band. In addition to the above, Technical Specification 3.7.10 (Area Temperature Monitoring) requires that an analysis be performed, if the 75 F limit is l

I exceeded for more than 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months to demonstrate continued operability of the equipment. An engineering Page 5

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evaluation has been - performed which concluded that safety-related equipment can be operated continuously up to 90*F in an environment without afTecting the capability of the equipment.

In the unlikely event that the non-safety-related chilled water subsystem and the operable safety related train of CRACS fait during the proposed 60 day AOT period, the Technical Specification 3.7.6.2 would require that actions be commenced to place the plant in a shutdown condition. Additionally, alternative actions to reduce control room temperature could also be initiated as identified in a plant procedure.

The risk significance involved with removing a safety-related train of the CRACS is extremely low based on the short period (60 days per train) and the consequences oflosing this function. The potential that the non-safety-related chilled . water subsystem and the operable safety-related train of CRACS simultaneously fail during the proposed 60 day AOT period of each safety-related train (120 days total) is considered unlikely. - North Atlantic has performed a risk evaluation of the potential of a simultaneous failure of the non-safety-related chilled water subsystem and the operable safety-related train of CRACS during the total 120 day period. This evaluation concluded that while the loss of equipment in the non-safety-related chilled water subsystem is not unlikely over the 120 day total period, based on generic component failure rates, the likelihood of loss of both of the non-safety related chilled water subsystem d

and the operable safety-related train of CRACS is low (7.4E ). There is no impact to the core damage frequency because the plant operators would restore the function or shutdown the plant before control room temperatures reached the point where equipment operation would be affected.

The second sentence of the proposed note identifies that the provisions of specifications 3.0.4 and 4.0.4 are not applicable during the AOT periods. TS 3.0.4 prohibits entry into a mode when the conditions for the LCO are not met and the associated action (s) requires a shutdown if they are not met within a specified time interval. Surveillance Requirement 4.0.4 prohibits entry into a mode unless the associated -

surveillance requirement (s) has been performed within the stated interval. During the implementation of the modification, when one safety-related train of CRACS is inoperable, it would not be possible to satisfy TS 3.0.4 and SR 4.0.4 following an unplanned plant shutdown. This restriction would unnecessarily restrict a restart of the plant. The conditions established by the note are necessary to allow

' the plant to restart without meeting the surveillance and LCO requirements of Technical Specification 3.7.6.2, in the event of a plant shutdown' while the design change is being implemented. During implementation of the design change, there will be two other means to cool the control room, one safety related train of CRACS and the non-safety-related chilled water subsystem.

In conclusion, the proposed one-time change to the Technical Specifications to extend the AOT period for Technical Specification 3.7.6.2 isjustified. The risk significance involved with removing a safety-related train of the CRACS during plant operation or shutdown conditians is low based on the short

. period (60 days per train) and consequences oflosing this function.

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ML20196G353

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