RS-13-176, Response to Request to Additional Information - Overall Integrated Plan in Response to Commission Order Modifying License Requirements for Reliable Spent Fuel Pool Instrumentation (Order No. EA-12-051)

Response to Request to Additional Information - Overall Integrated Plan in Response to Commission Order Modifying License Requirements for Reliable Spent Fuel Pool Instrumentation (Order No. EA-12-051)

ML13200A125
Person / Time
Site:	Dresden
Issue date:	07/18/2013
From:	Kaegi G Exelon Generation Co
To:	Office of Nuclear Reactor Regulation, Document Control Desk
References
RS-13-176
Download: ML13200A125 (15)

Text

Exeton Generation RS-13-176 Order No. EA-12-051 July 18, 2013 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001 Dresden Nuclear Power Station, Units 2 and 3 Renewed Facility Operating License Nos. DPR-19 and DPR-25 NRC Docket Nos. 50-237 and 50-249

Subject:

Response to Request for Additional Information - Overall Integrated Plan in Response to Commission Order Modifying License Requirements for Reliable Spent Fuel Pool Instrumentation (Order No. EA-12-051)

References:

1. Exelon Generation Company, LLC letter to USNRC, "Overall Integrated Plan in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051)," dated February 28, 2013 (RS-13-030)

2. NRC Order Number EA-12-051, "Issuance of Order to Modify Licenses with Regard to Reliable Spent Fuel Pool Instrumentation," dated March 12, 2012

3. USNRC letter to Exelon Generation Company, LLC, "Request for Additional Information Regarding Overall Integrated Plan for Reliable Spent Fuel Pool Instrumentation," dated June 26, 2013 In Reference 1, Exelon Generation Company, LLC (EGC) provided the Dresden Nuclear Power Station, Units 2 and 3, Overall Integrated Plan in Response to the March 12, 2012, Commission Order Modifying Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation, pursuant to NRC Order No. EA 051 (Reference 2).

The purpose of this letter is to provide the response to the NRC request for additional information (Reference 3) regarding the Dresden Nuclear Power Station, Units 2 and 3, Overall Integrated Plan in Response to the Commission Order Modifying Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation (Order No. EA-12-051).

The Dresden Nuclear Power Station, Units 2 and 3, Spent Fuel Pool Instrumentation design is proceeding on the schedule identified in the Overall Integrated Plan provided in Reference 1.

The enclosed responses to the NRC request for additional information are intended not to provide preliminary or conceptual information. The requested information, when fully developed, will be provided upon detailed design completion based on the milestone schedule dates provided in each response.

U.S. Nuclear Regulatory Commission Response to Request for Additional Information (Order EA-1 2-051)

July 18, 2013 Page 2 This letter contains no new regulatory commitments. If you have any questions regarding this response, please contact David P. Helker at 610-765-5525.

I declare under penalty of perjury that the foregoing is true and correct. Executed on the 18tr' day of July 2013.

Respectfully submitted, Glen T. Kaegi Director - Licensing & Regulatory Affairs Exelon Generation Company, LLC

Enclosure:

Dresden Nuclear Power Station, Units 2 and 3 - Response to Request for Additional Information - Overall Integrated Plan in Response to Commission Order Modifying License Requirements for Reliable Spent Fuel Pool Instrumentation (Order No. EA-1 2-051) cc: Director, Office of Nuclear Reactor Regulation NRC Regional Administrator - Region III NRC Senior Resident Inspector - Dresden Nuclear Power Station, Units 2 and 3 NRC Project Manager, NRR - Dresden Nuclear Power Station, Units 2 and 3 Mr. Robert J. Fretz, Jr, NRRIJLD/PMB, NRC Mr. Robert L. Dennig, NRRIDSS/SCVB, NRC Mr. Blake Purnell, NRC Project Manager, NRR Illinois Emergency Management Agency - Division of Nuclear Safety

U.S. Nuclear Regulatory Commission Response to Request for Additional Information (Order EA-12-051)

July 18, 2013 Page 3 bcc: Site Vice President - Dresden Nuclear Power Station, Units 2 and 3 Vice President Operations Support Site Engineering Director - Dresden Nuclear Power Station, Units 2 and 3 Regulatory Affairs Manager Regulatory Assurance Manager - Dresden Nuclear Power Station, Units 2 and 3 Severe Accident Management Director Site Operations Director - Dresden Nuclear Power Station, Units 2 and 3 Corporate Licensing Manager - West Corporate Licensing Director - West Exelon Records Management Vinod Aggarwal Roger Schiavoni Jonathan Hodapp Thomas J. Griffith

Enclosure 1 Dresden Nuclear Power Station, Units 2 and 3 Response to Request for Additional Information Overall Integrated Plan in Response to Commission Order Modifying License Requirements for Reliable Spent Fuel Pool Instrumentation (Order No. EA-12-051)

(11 pages)

Response to Request for Additional Information (Order EA-1 2-051)

Page 1 of 11

1.0 INTRODUCTION

By letter dated February 28, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13060A125), Exelon Generation Company, LLC, submitted an overall integrated plan (OIP) in response to the March 12, 2012, U.S. Nuclear Regulatory Commission (NRC) Order modifying licenses with regard to reliable spent fuel pool (SFP) instrumentation (Order EA-12-051; ADAMS Accession No. ML12054A679) for Dresden Nuclear Power Station, Units 2 and 3. The NRC staff endorsed Nuclear Energy Institute, NEI 12-02, "Industry Guidance for Compliance with NRC Order EA-12-051, to Modify Licenses with Regard to Reliable SFP Instrumentation," Revision 1, dated August 2012 (ADAMS Accession No. ML12240A307), with exceptions as documented in NRC Interim Staff Guidance, JLD-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.

2.0 LEVELS OF REQUIRED MONITORING The OIP states, in part, that:

Key spent fuel pool water 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 (elevation 612') 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 the primary and backup instrument channels. This is based on the height of the SFP weirs, demonstrating a water level of 23 feet (elevation 612') above the top of the storage racks is adequate for normal fuel pool cooling system operation.

Level adequate to provide substantial radiation shielding for a person standing on the spent fuel pool operating (Level 2): For both units, indicated level on either the primary or backup instrument channel of greater than 10 feet (elevation 599') plus instrument channel accuracy above the top of the storage racks based on the specification of this level as adequate in JLD-ISG-2012-03 and NEI 12-02, 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 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 589') 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.

Response to Request for Additional Information (Order EA-12-051)

Page 2 of 11

RAI-1

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. Indicate on this sketch the 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.

Response

a) Fuel Pool water level is normally maintained at approximately elevation 612' as indicated in the Overall Integrated Plan (OIP). Based on the following discussion, Level 1 is being designated to be approximately elevation 611'-3". This represents a small change from the OI P. The Spent Fuel Pool at Dresden Station has skimmers and scuppers located at an approximate 611'-3" elevation that water must flow into. From there the water is routed to the surge tanks from which the Fuel Pool Cooling Pumps draw suction. The suction trip is at an approximate 595'-0" elevation. Thus the approximate 611'-3" elevation reflects the higher of the two points noted in NEI 12-02, Section 2.3.1.

b) Please reference the sketch below. Instrument probe mounting details in the Spent Fuel Pool area will be provided in accordance with the response to RAI-3. Please note that the 23'-0" level sensor instrument range indicated below represents a small change from that discussed in the OIP.

Response to Request for Additional Information (Order EA-12-©51)

Page 3of11 Curb EL 613'-4"  ::f ___ rworrLoi3_u Floor EL 613'-0' Normal Water Level: EL 612'-0" Normal Water Level: EL 612'-0" l 1:

^ L 617'-3"

^L-m C

0 ar N

N m

Level 2:

EL 599'-0" EL EL 594'6" a 594' 6° Level 3:

EL 539'-0" Top of Fuel Rack: EL 589°-0" Top of Fuel Rack: EL 587-0" Bottom of SFP: EL 574'-Cr' Bottom of SFP: EL 574'-0" 33"-0" 33'-0 Unit 3 SFP Unit 2 SFP Spent Fuel Pool Elevation View Sketch NOTE: All elevations and distances are approximate

Response to Request for Additional Information (Order EA-12-051)

Page 4 of 11 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 northeast and southeast areas of the Unit 2 SFP separated by a distance in excess of 20 feet and in the northwest and southwest areas of the Unit 3 SFP separated by a distance in excess of 20 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 RB [Reactor Building]. 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 each 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.

Response

The current plan for the design of the SFPI system based on the current Exelon Nuclear program schedule for Dresden is to begin the design phase in September of 2014 with design completion and 100% acceptance of the design in December 2014 for Unit 2 and December 2015 for Unit 3. The requested information will be provided in the February 2015, 6-month Integrated Plan Update for Unit 2 and February 2016, 6-month Integrated Plan Update for Unit 3.

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.

RAI-3

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

Response to Request for Additional Information (Order EA-12-051)

Page 5 of 11 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.

Response

The current plan for the design of the SFPI system based on the current Exelon Nuclear program schedule for Dresden is to begin the design phase in September of 2014 with design completion and 100% acceptance of the design in December 2014 for Unit 2 and December 2015 for Unit 3. The requested information will be provided in the February 2015, 6-month Integrated Plan Update for Unit 2 and February 2016, 6-month Integrated Plan Update for Unit 3.

3.4 Qualification The OI P states, in part, that:

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

• components are supplied by manufacturers using commercial quality programs (such as ISO9001, "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:...

Response to Request for Additional Information (Order EA-1 2-051)

Page 6 of 11 RAE-4 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 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 a) the level sensor mounted in the SFP area, and b) 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.

Response

The current plan for the design of the SFPI system based on the current Exelon Nuclear program schedule for Dresden is to begin the design phase in September of 2014 with design completion and 100% acceptance of the design in December 2014 for Unit 2 and December 2015 for Unit 3. The requested information will be provided in the February 2015, 6-month Integrated Plan Update for Unit 2 and February 2016, 6-month Integrated Plan Update for Unit 3.

3.5 Independence The Ol P 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.

RAI-5

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

Response to Request for Additional Information (Order EA-1 2-051)

Page 7 of 11 separation, independence of signals sent to the location(s) of the readout devices, and the independence of the displays.

Response

The current plan for the design of the SFPI system based on the current Exelon Nuclear program schedule for Dresden is to begin the design phase in September of 2014 with design completion and 100% acceptance of the design in December 2014 for Unit 2 and December 2015 for Unit 3. The requested information will be provided in the February 2015, 6-month Integrated Plan Update for Unit 2 and February 2016, 6-month Integrated Plan Update for Unit 3.

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

Each channel will be normally powered from a different 120Vac [120 volts-alternating current] 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 until off-site resources can be deployed by the mitigating strategies resulting from Order EA-12-0494. Additionally, each channel will have provisions for connection to another suitable power source.

RAI-6

Please provide the following:

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 following the onset of the beyond-design-basis event for the minimum duration needed, consistent with the plant mitigation strategies for beyond-design-basis external events (Order EA-12-049).

Response

The current plan for the design of the SFPI system based on the current Exelon Nuclear program schedule for Dresden is to begin the design phase in September of 2014 with design completion and 100% acceptance of the design in December 2014 for Unit 2 and December 2015 for Unit 3. The requested information will be provided in the February 2015, 6-month Integrated Plan Update for Unit 2 and February 2016, 6-month Integrated Plan Update for Unit 3.

Response to Request for Additional Information (Order EA-1 2-051)

Page 8of 11 3.7 Accuracy The OI P 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 the specified lower level of each indicating range (levels 1, 2 or 3) without conflicting or ambiguous indications.

RAI-7

Please provide the following:

a) An estimate of the expected instrument channel accuracy performance (e.g., in percent of span) under both a) normal SFP level conditions (approximately Level 1 or higher) and b) at the beyond design-basis 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.

Response

The current plan for the design of the SFPI system based on the current Exelon Nuclear program schedule for Dresden is to begin the design phase in September of 2014 with design completion and 100% acceptance of the design in December 2014 for Unit 2 and December 2015 for Unit 3. The requested information will be provided in the February 2015, 6-month Integrated Plan Update for Unit 2 and February 2016, 6-month Integrated Plan Update for Unit 3.

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- 032 and NEI 12-023. Details will be determined during detailed design engineering.

Response to Request for Additional Information (Order EA-1 2-051)

Page 9 of 11

RAI-8

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 preventative 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.

Response

The current plan for the design of the SFPI system based on the current Exelon Nuclear program schedule for Dresden is to begin the design phase in September of 2014 with design completion and 100% acceptance of the design in December 2014 for Unit 2 and December 2015 for Unit 3. Following the issue of the design, procedures will start being developed with a projected July 2015 or 2016 completion date, respectively. The requested information will be provided in the August 2015, 6-month Integrated Plan Update for Unit 2 and August 2016, 6-month Integrated Plan Update for Unit 3.

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.

RAI-9

Please provide the following:

a) The specific location for each of the primary and backup instrument channel displays.

b) If the primary and backup display location is other than the main control room, 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.

Response to Request for Additional Information (Order EA-1 2-051)

Page 10 of 11 c) The reasons justifying why the locations selected enable the information from these instruments to be considered "promptly accessible." Include consideration of various drain-down scenarios.

Response

The current plan for the design of the SFPI system based on the current Exelon Nuclear program schedule for Dresden is to begin the design phase in September of 2014 with design completion and 100% acceptance of the design in December 2014 for Unit 2 and December 2015 for Unit 3. The requested information will be provided in the February 2015, 6-month Integrated Plan Update for Unit 2 and February 2016, 6-month Integrated Plan Update for Unit 3.

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.

Response

The current plan for the design of the SFPI system based on the current Exelon Nuclear program schedule for Dresden is to begin the design phase in September of 2014 with design completion and 100% acceptance of the design in December 2014 for Unit 2 and December 2015 for Unit 3. Following the issue of the design, procedures will start being developed with a projected July 2015 or 2016 completion date, respectively. The requested information will be provided in the August 2015, 6-month Integrated Plan Update for Unit 2 and August 2016, 6-month Integrated Plan Update for Unit 3.

Response to Request for Additional Information ((Order EA-12-051)

Page 11 of 11 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 Maintenance Procedure will be written to direct calibration and repair of the instruments. Passport will be used to control the calibration and setpoint parameters. The Passport PMID system 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) A description of how the guidance in NEI 12-02, Section 4.3, regarding compensatory actions for one or both non-functioning channels will be addressed.

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

Response

The current plan for the design of the SFPI system based on the current Exelon Nuclear program schedule for Dresden is to begin the design phase in September of 2014 with design completion and 100% acceptance of the design in December 2014 for Unit 2 and December 2015 for Unit 3. Following the issue of the design, procedures will start being developed with a projected July 2015 or 2016 completion date, respectively. The requested information will be provided in the August 2015, 6-month Integrated Plan Update for Unit 2 and August 2016, 6-month Integrated Plan Update for Unit 3.

It is noted that the above wording for RAI-1 1 is editorially corrected to identify parts (a), (b), and (c) to be consistent with the NRC draft email RAI issued on June 19, 2013. The NRC RAI letter to Exelon, dated June 26, 2013 (Reference 3), incorrectly listed parts (a), (b), (c), and (d).