ML13191B255
| ML13191B255 | |
| Person / Time | |
|---|---|
| Site: | Braidwood  |
| Issue date: | 07/11/2013 |
| From: | Purnell B A Plant Licensing Branch III |
| To: | Pacilio M J Exelon Generation Co |
| Blake Purnell, NRR/DORL 415-1380 | |
| References | |
| EA-12-051, TAC MF0821, TAC MF0822 | |
| Download: ML13191B255 (10) | |
Text
UNITED NUCLEAR REGULATORY WASHINGTON, D.C. 20555-0001 July 11, 2013 Mr. Michael J. Pacilio Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555 BRAIDWOOD STATION, UNITS 1 AND 2 -REQUEST FOR ADDITIONAL INFORMATION REGARDING OVERALL INTEGRATED PLAN FOR RELIABLE SPENT FUEL POOL INSTRUMENTATION (TACNOS. MF0821 AND MF0822) Dear Mr. Pacilio: By letter dated February 28, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 13059A265), Exelon Generation Company, LLC submitted the overall integrated plan for Braidwood Station, Units 1 and 2, to the U.S. Nuclear Regulatory Commission (NRC) in response to the March 12, 2012. Order modifying licenses with regard to requirements for reliable spent fuel pool instrumentation (Order EA-12-051). The NRC staff is reviewing your submittal and has determined that additional information is required to complete its review. The specific information requested is addressed in the enclosure to this letter. Please provide a response to this information request by July 3"i, 2013. If some information is unavailable by July 31,2013, then provide the date when any'additional information will be submitted. Should you have any questions, please feel free to contact me at 301-415-1380. Sincerely,tA Blak.e Purnell, Project Manager Plant Licensing 111-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. STN 50-456 and STN 50-457 RAI for Braidwood Station, Units 1 and cc w/encl: Distribution via REQUEST FOR ADDITIONAL INFORMATION OVERALL INTEGRATED PLAN IN RESPONSE TO COMMISSION ORDER MODIFYING LICENSE REQUIREMENTS FOR RELIABLE SPENT FUEL POOL INSTRUMENTATION (ORDER EA-12-051) EXELON GENERATION COMPANY, LLC BRAIDWOOD STATION, UNITS 1 AND 2 DOCKET NOS. STN 50-456 AND 50-457 1.0 INTRODUCTION By letter dated February 28, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML 13059A265), 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. ML 12054A679) for Braidwood Station, Units 1 and 2. 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. ML 12240A307), with exceptions as documented in NRC Interim Staff Guidance, 2012-03, "Compliance with Order EA-12-051, Reliable Spent Fuel Pool Instrumentation," Revision 0, dated August 29,2012 (ADAMS Accession No. ML 12221A339). 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: Level adequate to support operation of the normal fuel pool cooling system (Level 1): Indicated level on either primary or backup instrument channel of greater than 18 feet (elevation 418'-1 %") above the top of the storage racks based on the design accuracy of the instrument channel (which will be determined in the detailed design phase) and a resolution of 1 foot or better of both the primary and backup instrument channels. This is based on Spent Fuel Pool Cooling Pump suction strainer elevation. A calculation demonstrating adequate water level will be performed as part of the detailed engineering Enclosure
-design phase to ensure the level 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 deck (Level 2): Indicated level on either the primary or backup instrument channel of greater than 10 feet (elevation 410'-1 %") plus instrument channel accuracy (which will determined in the detailed design phase) 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): Indicated level on either the primary or backup instrument channel of greater than 0 feet (elevation 400'-1 %") plus instrument channel accuracy above the top of the storage racks based upon the design accuracy (which will determined in the detailed design phase) 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 rack. 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 the 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. 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 southwest and northwest corners of the 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 at an elevation below the SFP operating floor or in buildings other than the FHB [Fuel Handling 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 sensors, and the proposed routing of the cables that will extend from the sensors toward the location of the local electronics cabinets and read-out/display devices in the main control room or alternate accessible location. 3.3 Mounting The alP states, in part, that: Design of the mounti'ng 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 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 alP states, in part, that: Reliability of both instrument channels will be demonstrated via an appropriate combination of design, analyses, operating experience, and/or testing of channel components ....
Temperature, humidity and radiation levels consistent with the conditions in the vicinity of the SFP and the area of use considering normal operation, event and post-event conditions for no fewer than seven days post-event or until off-site resources can be deployed by the mitigating strategies resulting from Order EA-12-049 (Ref. 4), will be addressed in the detailed design engineering phase of the project. 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 .... RAI-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 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. 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.
-5 RAI-5 Please provide the following: (a) A description of how the two channels of the proposed level measurement system in each pool 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 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-12-049 (Ref. 4). 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 capacittes 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). 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 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 (Le., radiation, temperature, humidity, 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 (Ref. 2) and NEI 12-02 (Ref. 3). Details will be determined during detailed design engineering phase. 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.
-7 3.9 Display The alP 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. 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. (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. 4.0 PROGRAM FEATURES 4.2 Procedures The alP 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 Spent Fuel Pool 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.
-8 4.3 Testing and Calibration The DIP 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. Calibration will be performed to an Instrument Maintenance Procedure (BIP/BISR series). A Passport PMID will be used to direct frequency for performance of the instrument calibration. Both primary and backup instrumentation channels will be functional at all times when there is fuel in the SFP with allowance for testing, maintenance or repair per NEI 12-02 (Ref. 3). 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.
Mr. Michael J. Pacilio Senior Vice President Exelon Generation Company, LLC President and Chief Nuclear Officer Exelon Nuclear 4300 Winfield Road Warrenville, IL 60555 BRAIDWOOD STATION, UNITS 1 AND 2 -REQUEST FOR ADDITIONAL INFORMATION REGARDING OVERALL INTEGRATED PLAN FOR RELIABLE SPENT FUEL POOL INSTRUMENTATION (TAC NOS. MF0821 AND MF0822) Dear Mr. Pacilio: By letter dated February 28, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. IVIL13059A265). Exelon Generation Company. LLC submitted the overall integrated plan for Braidwood Station. Units 1 and 2. to the U.S. Nuclear Regulatory Commission (NRC) in response to the March 12. 2012. Order modifying licenses with regard to requirements for reliable spent fuel pool instrumentation (Order EA-12-051). The NRC staff is reviewing your submittal and has determined that additional information is required to complete its review. The specific information requested is addressed in the enclosure to this letter. Please provide a response to this information request by July 31. 2013. If some information is unavailable by July 31, 2013. then provide the date when any additional information will be submitted. Should you have any questions. please feel free to contact me at 301-415-1380. Sincerely, / RA / Blake Purnell. Project Manager Plant Licensing Branch 111-2 Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket Nos. STN 50-456 and STN RAI for Braidwood Station. Units 1 and cc w/encl: Distribution via DISTRIBUTION: PUBLIC LPL3-2 RlF RidsAcrsAcnwMailCenter JEvans, NRR RidsNrrDorlLpl3-2 RidsNrrPMBraidwood BPurneil, NRR RidsRgn3MailCenter RidsNrrLASRohrer RidsNrrDeEicb SJones, NRR GSingh, NRR DRahn, NRR RidsNrrDssSbpb ADAMS Accession No.: ML 13191B255 "by memo dated OFFICE ,LPL3-2/PM LPL3-2/LA LPL3-2/BC NAME BPurneil SRohrer JBowen DATE 71 11 113 7/11/13 7/11/13 OFFICE NRR/DSS/SBPB:BC" NRRlDE/EICB:BC" LPL3-2/PM INAME IGCasto JThorp BPurnell IDATE 6/27113" 6/27/13 OFFICIAL RECORD COpy