ML13171A315

Request for Additional Information Overall Integrated Plan in Response to Order EA-12-051, Reliable Spent Fuel Pool Instrumentation

ML13171A315
Person / Time
Site:	Limerick
Issue date:	06/24/2013
From:	Richard Ennis Plant Licensing Branch 1
To:	Pacilio M Exelon Generation Co
Ennis R
References
EA-12-051, TAC MF0854, TAC MF0855
Download: ML13171A315 (10)

Text

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UNITED STATES NUCLEAR REGULATORY COMMISSION WASHINGTON, D.C. 20555-0001 June 24, 2013 Mr. Michael J. Pacilio President and Chief Nuclear Officer Exelon Generation Company, LLC 4300 Winfield Road Warrenville, IL 60555

SUBJECT:

LIMERICK GENERATING STATION, UNITS 1 AND 2- REQUEST FOR ADDITIONAL INFORMATION RE: OVERALL INTEGRATED PLAN IN RESPONSE TO ORDER EA-12-051, "RELIABLE SPENT FUEL POOL INSTRUMENTATION" (TAC NOS. MF0854 AND MF0855)

Dear Mr. Pacilio:

By letterdated February 28, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13059A391 ), Exelon Generation Company, LLC submitted an Overall Integrated Plan, for Limerick Generating Station, Units 1 and 2, in response to the March 12, 2012, U.S. Nuclear Regulatory Commission (NRC) Order modifying licenses with regard to requirements for reliable spent fuel pool instrumentation (Order Number EA-12-051; ADAMS Accession No. ML12054A679).

The NRC staff is reviewing your submittal and has determined that additional information is needed to complete its review. The specific questions are found in the enclosed request for

. additional information (RAI). The RAI questions were provided in draft form to Mr. David Helker of your staff via e-mail on June 19, 2013, with a request to respond by July 19, 2013. Note, if any part of the information requested is not available by the July 19, 2013, response date for this RAI, please provide the date the mformation will be submitted in your response.

If you have any questions, please contact me at (301) 415-1420.

Sincerely,

• -eE~

Richard B. Ennis, Senior Project Manager Plant Licensing Branch 1-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-352 and 50-353

Enclosure:

Request for Additional Information cc wiencl: DistributiOr! via Listserv

REQUEST FOR ADDITIONAL INFORMATION OVERALL INTEGRATED PLAN IN RESPONSE TO ORDER EA-12-051. "RELIABLE SPENT FUEL POOL INSTRUMENTATION" EXELON GENERATION COMPANY. LLC LIMERICK GENERATING STATION. UNITS 1 AND 2 DOCKET NOS. 50-352 AND 50-353

1.0 INTRODUCTION

By letter dated February 28, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13059A391 ), Exelon Generation Company, LLC (the licensee) submitted an Overall Integrated Plan (OIP), for Limerick Generating Station, Units 1 and 2, in response to the March 12, 2012, U.S. Nuclear Regulatory Commission (NRC) Order modifying licenses with regard to requirements for reliable spent fuel pool (SFP) instrumentation (Order Number EA-12-051; ADAMS Accession No. ML12054A679). The NRC staff endorsed Nuclear Energy Institute (NEI) 12-02, "Industry Guidar:~ce for Compliance with NRC Order EA-12-051, To Modify Licenses with Regard to Reliable Spent Fuel Pool Instrumentation," Revision 1, dated August 2012 (ADAMS Accession No. ML12240A307), with exceptions, as documented in Interim Staff Guidance (ISG) 2012-03, "Compliance with Order EA-12-051, Reliable Spent Fuel Pool Instrumentation," Revision 0, dated August 29, 2012 (ADAMS Accession No. ML12221A339).

The NRC staff has reviewed the February 28, 2013, response by the licensee and determined that the following Request for Additional Information (RAI) is needed to complete its technical review. The sections that follow are numbered to coincide with the arrangement presented in NEI 12-02.

2.0 LEVELS OF REQUIRED MONITORING The OIP states, in part, that key SFP levels will be identified as follows:

Level adequate to support operation of the normal fuel pool cooling system (Level 1): For both units, indicated level on either primary or backup instrument channel of greater than 23 feet 6 inches (approximately 351 ft elevation) plus instrument channel accuracy above the top of the storage racks based on the design accuracy of the instrument channel (which is to be determined) and a resolution of 1 foot or better for both tlile primary and backup instrument channels. This is based on the height of the SFP weirs, demonstrating a water level of 23 feet 6 inches (approx. 351 ft elevation) is adequate for normal fuel

.pool cooling system operation.

Enclosure

Level adequate to provide substantial radiation shielding for a person standing on the spent fuel pool operating deck (Level 2): For both units, indicated level on either the primary or backup instrument channel of greater than 10 feet (elevation 337.5') plus instrument channel accuracy above the top of the storage racks based on specification of this level as adequate in NRC JLD-ISG-2012-03 (Ref. 2) and NEI 12-02 (Ref. 3), the specified design accuracy of the instrument channel, and the relatively low sensitivity of dose rates to changes in water depth at this level. This monitoring level ensures there is an adequate water level to provide substantial radiation shielding for a person standing on the spent fuel pool operating deck from direct gamma radiation from stored spent fuel.

Level where fuel remains covered (Level 3): For both units, indicated level on either the primary or backup instrument channel of greater than 0 feet (elevation 327.5') plus instrument channel accuracy above the top of the storage racks based upon the design accuracy (which is to be determined) of the instrument channel for both the primary and backup instrument channels. This monitoring level assures that water is covering the stored fuel seated in the racks.

Please provide the following:

a) For level 1, specify how the identified location represents the HIGHER of the two points described in the NEI 12-02 guidance for this level.

b) A clearly labeled sketch depicting the elevation view of the proposed typical mounting arrangement for the portions of instrument channel consisting of permanent measurement channel equipment (e.g., fixed level-sensors and/or stilling wells, and mounting brackets). Indicate on this sketch the datum values representing Level 1, Level 2, and Level 3, as well as the top of the fuel racks. Indicate on this sketch th~

portion of the level sensor measurement range that is sensitive to measurement of the fuel pool level, with respect to the Level 1, Level 2, and Level 3 datum points. Indicate on this sketch, the elevation of the bottom opening of the gates that connect the two pools.

3.0 INSTRUMENTATION.DESIGN FEATURES 3.2 Arrangement The OIP states, in part, that:

The current plan is to install SFP level sensors in the northwest corner of the Unit 1 SFP and in the northeast corner of the Unit 2 SFP separated by a distance in excess of 50 feet. The sensors themselves will be mounted, to the extent practical, near the pool walls and below the pool curb to minimize their exposure to damaging debris and not interfere with SFP activities. Instrument channel electronics and power supplies will be located in seismic and missile protected

areas either below the SFP operating floor or in buildings other than the RE

[reactor enclosure]. The areas to be. selected will provide suitable radiation shielding and environmental conditions for the equipment consistent with instrument manufacturer's recommendations. Equipment and cabling for power supplies and indication for channel will be separated equivalent to that provided for redundant safety related services.

RAI-2

Please provide a clearly labeled sketch or marked-up plant drawing of the plan view of the SFP area, depicting the SFP inside dimensions, the planned locations/placement of the primary and back-up SFP level sensor, and the proposed routing of the cables that will extend from the sensors toward the location of the read-out/display device.

3.3 Mounting The OIP states, in part, that:

Design of the mounting of the sensors in the SFP shall be consistent with the seismic Class I criteria. Installed equipment will be verified to be seismically adequate for the seismic motions associated with the maximum seismic ground motion considered in the design of the plant area in which it is installed.

Please provide the following:

a) The design criteria that will be used to estimate the total loading on the mounting device(s), inCluding static weight loads and dynamic loads. Describe the methodology that will be used to estimate the total loading, inclusive of design-basis maximum seismic loads and the hydrodynamic loads that could result from pool sloshing or other effects that could accompany such seismic forces.

b) A description of the manner in which the level sensor (and stilling well, if appropriate) will be attached to the refueling floor and/or other support structures for each planned point of attachment of the probe assembly. Indicate in a schematic, the portions of the level sensor that will serve as points of attachment for mechanical/mounting or electrical connections.

c) A description of the manner by which the mechanical connections will attach the level instrument to permanent SFP structures so as to support the level sensor assembly.

3.4 Qualification The OIP states, in part, that:

Components of the instrument channels will be qualified for shock and vfbration, using one or more of the following methods:

-4,.

• components are supplied by manufacturers using commercial quality programs (such as 1809001, "Quality management systems-Requirements") with shock and vibration requirements included in the purchase specification at levels commensurate with portable hand-held device or transportation applications;

• components have substantial history of operational reliability in environments with significant shock and vibration loadings, such as portable hand-held device or transportation applications; or

• components are inherently resistant to shock and vibration loadings, such as cables.

For seismic effects on instrument channel components used after a potential seismic event for only installed components (with the exception of battery chargers and replaceable batteries), the following measures will be used to verify that the design and installation is adequate. Applicable components are rated by

• the manufacturer (or otherwise tested) for seismic effects at levels commensurate with those of postulated design basis event conditions in the area of instrument channel component use using one or more of the following methods: ...

Please provide the following:

a) A description of the specific method or combination of methods you intend to apply to demonstrate the reliability of the permanently installed equipment under Beyond-Design-Basis (BOB) ambient temperature, humidity, shock, vibration, and radiation conditions.

b) A description of the testing and/or analyses that will be conducted to provide assurance that the equipment will perform reliably under the worst-case credible design-basis loading at the location where the equipment will be mounted. Include a discussion of this seismic reliability demonstration as it applies to (i) the level sensor mounted in the SFP area, and (ii) any control boxes, electronics, or read-out and re-transmitting devices that will be employed to convey the level information from the level sensor to the plant operators or emergency responders.

c) A description of the specific method or combination of methods that will be used to confirm the reliability of the permanently installed equipment such that following a seismic event the instrument will maintain its required accuracy.

3.5 Independence The OIP states, in part, that:

The primary instrument channel will be independent of the backup instrument channel. This independence will be achieved through physical and electrical

separation of each channels' components commensurate with hazard and electrical isolation needs.

Please provide the following:

a) A description of how the two channels of the proposed level measurement system meet this requirement so that the potential for a common cause event to adversely affect both channels is minimized to the extent practicable.

b) Further information describing the design and installation of each level measurement system, consisting of level sensor electronics, cabling, and readout devices. Please address how independence of these components of the primary and back-up channels is achieved through the application of independent power sources, physical and spatial

, separation, independence of signals sent to the location(s) of the readout devices, and the independence of the displays.

3.6 Power Supplies The OIP states, in part, that:

Each channel will be normally powered from a different 120 [volts alternating current] Vac bus. Upon loss of normal ac power, individual channel installed batteries will automatically maintain continuous channel operation. The batteries will be replaceable and be sized to maintain channel operation unti.l off-site resources can be deployed by the mitigating strategies resulting from Order EA-12-049. Additionally, each channel will have provisions for connection to another suitable power source. *

RAI-6

Please provide thefollowing:

a) A description of the electrical AC power sources and capacities for the primary and backup channels.

b) If the level measurement channels are to be powered through a battery system (either directly or through an Uninterruptible Power Supply}, please provide the design criteria that will be applied to size the battery in a manner that ensures, with margin, that the channel will be available to run reliably and continuously followi[lg the onset of the BOB event for the minimum duration needed, consistent with the plant mitigation strategies for BOB external events (Order EA-12-049).

3. 7 Accuracy The OIP states, in part, that:

The instrument channels will be designed to maintain their design accuracy following a power interruption or change in power source without recalibration.

Instrument channel accuracy, to be determined during detailed design, will consider Spent Fuel Pool conditions (e.g., saturated water, steam environment, concentrated borated water), as well as, other applicable radiological and environmental conditions and include display accuracy. Instrument channel accuracy will be sufficient to allow trained personnel to determine when the actual level exceeds t~e specified lower level of each indicating range (levels 1, 2 or 3) without conflicting or ambiguous indications.

Please provide the following:

a) An estimate of the expected instrument channel accuracy performance (e.g., in % of span) under both: (i) normal SFP level conditions (approximately Level 1 or higher); and (ii) at the BOB conditions (i.e., radiation, temperature, humidity, post-seismic and post-shock conditions) that would be present if the SFP level were at the Level 2 and Level 3 datum points.

• b) A description of the methodology that will be used for determining the maximum allowed deviation from the instrument channel design accuracy that will be employed under normal operating conditions as an acceptance criterion for a calibration procedure to flag to. operators and to technicians that the channel requires adjustment to within the normal condition design accuracy.

3.8 Testing The OIP states, in part, that:

Instrument channel design will provide for routine testing and calibration consistent with the guidelines of NRC JLD-ISG-2012-03 and NEI 12-02 .. Details will be determined during detailed design engineering.

Please provide the following:

a) A description of the capability and provisions the proposed level sensing equipment will have to enable periodic testing and calibration, including how this capability enables the equipment to be tested in-situ.

• b) A description of how such testing and calibration will enable the conduct of regular channel checks of each independent channel against the other, and against any other permanently-installed SFP level instrumentation.

• c) A description of how calibration tests and functional checks will be performed and the frequency at which they will be conducted. Discuss how these surveillances will be incorporated into the plant surveillance program.

d) A description of what preventive maintenance tasks are required to be performed during normal operation, and the planned maximum surveillance interval that is necessary to ensure that the channels are fully conditioned to accurately and reliably perform their functions when needed.

3.9 Display The OIP states, in part, that:

The primary and backup instrument displays will be located at the control room, alternate shutdown panel, or other appropriate and accessible location. The specific location will be determined during detailed design.

Please provide the following:

a) The specific location for the primary and backup instrument channel display.

b) If the primary or backup display location is other than the main control room, then provide justification for prompt accessibility to displays including primary and alternate route evaluation, habitability at display location(s), continual resource availability for personnel responsible to promptly read displays, and provisions for communications with decision makers for the various SFP drain-down scenarios and external events.

c) The reasons justifying why the locations selected enable the information from these instruments to be considered "promptly accessible" to various drain-down scenarios and external events.

4.0 PROGRAM FEATURES 4.2 Procedures The OIP states, in part, that:

Procedures will be developed using guidelines and vendor instructions to address the maintenance, operation and abnormal response issues associated with the primary and backup channels of SFP instrumentation.

RAI-10

Please provide the following:

a) A list of the operating (both normal and abnormal response) procedures, calibration/test procedures, maintenance procedures, and inspection procedures that will be developed for use of the SFP instrumentation in a manner that addresses the order requirements.

b) A brief description of the specific technical objectives to be achieved within each procedure. If your plan incorporates the use of portable spent fuel level monitoring components, please include a description of the objectives to be achieved with regard to the storage location and provisions for installation of the portable components when needed. ,

4.3 Testing and Calibration The OIP states, in part, that:

The testing and calibration of the instrumentation will be consistent with vendor recommendations or other documented basis. Calibration will be specific to the mounted instruments and the displays. A procedure will be written to direct calibration and repair of the instruments. Preventive Maintenance (PM) program will be used to direct the calibration frequency of the instruments.

RAI-11

Please provide the following:

a) Further information describing the maintenance and testing program the licensee will establish and implement to ensure that regular testing and calibration is performed and verified by inspection and audit to demonstrate conformance with design and system readiness requirements. Include a description of your plans for ensuring that necessary channel checks, functional tests, periodic calibration, and maintenance will be conducted for the level measurement system and its supporting equipment.

b) Describe how the guidance in NEI12-02, Section 4.3, regarding compensatory actions for one or both non-functioning channels will be addressed. ,

c) Describe what compensatory actions are planned in the event that one of the instrument channels cannot be restored to functional status within 90 days.

ML12054A679).

The NRC staff is reviewing your submittal and has determined that additional information is needed to complete its review. The specific questions are found in the enclosed request for additional information (RAI). The RAI questions were provided in draft form to Mr. David Helker of your staff via e-mail on June 19, 2013, with a request to respond by July 19, 2013. Note, if any part of the information requested is not available by the July 19, 2013, response date for this RAI, please provide the date the information will be submitted in your response. *.

If you have any questions, please contact me at (301) 415-1420.

Sincerely,

/RAJ Richard B. Ennis, Senior Project Manager Plant Licensing Branch 1-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. 50-352 and 50-353

Enclosure:

Request for Additional Information cc w/encl: Distribution via Listserv DISTRIBUTION:

PUBLIC JEvans, NRR/DRA/APLA LPL 1-2 R/F SDarbali, NRR/DE/EICB RidsNrrDorllpl1-2 Resource CRoque-Cruz, NRR/DSS/SBPB RidsNrrPMLimerick Resource RidsNrrDssSbpb Resource RidsNrrLAABaxter Resource RidsNrrDeEicb Resource JWhited, NRR/DORL RidsAcrsAcnw_MaiiCTR Resource RidsRgn1 MaiiCenter Resource ADAMS Accession No*.. ML13171A315 *via memo dated 5/30/13 OFFICE LPL 1-2/PM LPL 1-2/LA SBPB/BC* LPL 1-2/BC(A)

NAME HEnnis ABaxter GCasto VRodriguez DATE 06/24/13 06/24/13 05/30/13 06/24/13