LIC-13-0144, Omaha Public Power District Response to NRC Request for Additional Information Regarding the Overall Integrated Plan in Response to Order EA-12-051 Reliable Spent Fuel Pool Instrumentation
| ML13294A338 | |
| Person / Time | |
|---|---|
| Site: | Fort Calhoun  |
| Issue date: | 10/18/2013 |
| From: | Cortopassi L Omaha Public Power District |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| EA-12-051, LIC-13-0144 | |
| Download: ML13294A338 (29) | |
Text
444 South 16th Street Mall Omaha, NE 68102-2247 October 18, 2013 LIC-13-0144 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555-0001
References:
- 1. Docket No. 50-285
- 2. NRC Order Number EA-12-051, Order Modifying Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation, dated March 12, 2012 (ML12056A044) (NRC-12-0023)
- 3. Letter from OPPD (L. P. Cortopassi) to NRC (Document Control Desk) Fort Calhoun Station Spent Fuel Pool Instrumentation Overall Integrated Plan, dated February 28, 2013 (ML13059A268) (LIC-13-0011)
- 4. Email from NRC (L. Wilkins) to OPPD (B. R. Hansher), DRAFT: RAI for Fort Calhoun Station Re: Reliable Spent Fuel Pool Instrumentation Order Response (Overall Integrated Plan) (MF0968), dated August 29, 2013
SUBJECT:
Omaha Public Power District Response to NRC Request for Additional Information Regarding the Overall Integrated Plan in Response to Order EA-12-051 Reliable Spent Fuel Pool Instrumentation On March 12, 2012, the Nuclear Regulatory Commission (NRC) issued an Order (Reference 2) to all power reactor licensees and holders of construction permits in active or deferred status.
The Order was immediately effective and requires the Omaha Public Power District (OPPD) to have a reliable indication of the water level in Fort Calhoun Stations spent fuel storage pool.
Specific requirements for such indication are described in Attachment 2 of the Order. The Order also required that an overall integrated plan for achieving compliance with these requirements be submitted by February 28, 2013.
In Reference 3, OPPD submitted its overall integrated plan (OIP) and the NRC requested additional information in Reference 4. OPPDs response to Reference 4 is attached.
No new commitments to the NRC are contained in this submittal.
If you have any additional questions, or require further information, please contact Mr. Bill R.
Hansher at (402) 533-6894.
Employment with Equal Opportunity
U. S. Nuclear Regulatory Commission LlC-13-0144 Page 2 I declare under penalty of perjury that the foregoing is true and correct; executed on October 18, 2013.
Louis P. Cortopassi Site Vice President and CND LPC/JKG/mle
Enclosure:
DPPD Response to NRC Request for Additional Information c: M. L. Dapas, NRC Regional Administrator, Region IV J. M. Sebrosky, NRC Senior Project Manager L. E. Wilkins, NRC Project Manager J. C. Kirkland, NRC Senior Resident Inspector
LIC-13-0144 Enclosure Page 1 OPPD Response to NRC Request for Additional Information
LIC-13-0144 Enclosure Page 2 REQUEST FOR ADDITIONAL INFORMATION OVERALL INTEGRATED PLAN IN RESPONSE TO ORDER EA-12-051 RELIABLE SPENT FUEL POOL INSTRUMENTATION OMAHA PUBLIC POWER DISTRICT FORT CALHOUN STATION DOCKET NUMBER 50-285
1.0 INTRODUCTION
By letter dated February 28, 2013(Agency wide Documents Access and Management System (ADAMS) Accession No. ML13059A268), Omaha Public Power District submitted an Overall Integrated Plan (OIP) in response to the March 12, 2012, Commission Order licenses with regard to requirements for Reliable Spent Fuel Pool (SFP) Instrumentation (Order Number EA-12-051; ADAMS Accession No. ML12054A679) for Fort Calhoun Station. The U.S. Nuclear Regulatory Commission (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 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 information is needed to complete its review.
2.0 LEVELS OF REQUIRED MONITORING The OIP states, in part, that Key spent fuel pool water levels:
- 1. Level adequate to support operation of the normal fuel pool cooling system -
Indicated level on either the primary or backup instrument channel will be approximately elevation 1034.6 (existing low level alarm LIA-2846, 39.1 feet above pool floor) plus the accuracy of the SFP level instrument channel and the current LIA-2846 low water level alarm. The Level 1 elevation is approximately 23 feet above the lowest spent fuel pool cooling suction line, and is a conservative elevation that has been established above the lowest spent fuel pool cooling suction line. The exact elevation for Level 1 will be determined during the detailed design and engineering phase, but will be approximately the same as the low-level alarm elevation of the current LIA-2846 instrument.
- 2. Level adequate to provide substantial radiation shielding for a person standing on the spent fuel pool operating deck - Indicated level on either the primary or backup instrument channel will be approximately elevation 1020 plus the accuracy of the SFP level instrument channel, which is to be determined. This elevation is approximately 10 above the top of the spent fuel storage racks (Reference 7). The top of the spent fuel storage racks is approximately at elevation 1009-7 (per Reference 7). The top of the active fuel area is approximately elevation 1007-5 and
LIC-13-0144 Enclosure Page 3 as such approximately an additional 2.5 of water shielding is available through setting the Level 2 elevation at 1020. The Level 2 elevation of 1020 is approximately 12-7 above the top of the active fuel. This water level should provide substantial radiation shielding for personnel to respond to Beyond-Design-Basis external events and initiate any SFP makeup strategies.
- 3. Level where fuel remains covered - Indicated level on either the primary or backup instrument channel will be approximately elevation 1011 (approximately one foot above the top of the highest spent fuel rack) plus the accuracy of the SFP level instrument channel, which is to be determined. This elevation is approximately 1 above the top of the spent fuel rack. This monitoring level assures that there is adequate water level above the stored fuel seated in the rack. Setting Level 3 elevation at 1011 provides a water level of approximately 3.5 over the top of the active fuel region.
RAI-1
Please provide the following:
a) For level 1, specify how the identified elevation 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 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.
OPPD RAI-1a Response The proposed Level 1 elevation is to coincide with the existing low level spent fuel pool instrument alarm setpoint. Details regarding this elevation selection related to the two points described in the NEI 12-02 guidance have not been completed and will be part of the detailed design modification process. The elevation selected will be consistent with the guidance in NEI 12-02.
The Fort Calhoun Station (FCS) spent fuel pool (SFP) has two (2) cooling suction inlet locations, upper and lower. The upper suction inlet is at 1,034 centerline and the lower suction inlet centerline is at 1,011-4. The FCS SFP cooling pumps are located near the 989 floor elevation, with the pump suction centerline at 991-3 elevation. The distance from the pump centerline to the upper inlet suction centerline is 42.75. The Level 1 elevation will be set near the existing low level alarm, which is approximately 43.25 above the SFP pump suction centerline. This elevation meets the guidance identified in NEI 12-02, but formal verification has not been completed. The cooling discharge line to the SFP is at 1,031-7 and is an open-ended pipe. Details regarding the exact Level 1 location in regards to the guidance of NEI 12-02 will be provided in a future Omaha Public Power District (OPPD) six-month update.
LIC-13-0144 Enclosure Page 4 OPPD RAI-1b Response Details for the proposed mounting arrangement and portions of the instrument channel equipment have not been finalized in regards to elevation view. Details for the proposed typical mounting arrangement will be provided in a future OPPD six-month update. Conceptually, the mounting bracket is to be placed at or near the pool deck elevation. The detailed datum values will be provided in a future OPPD six-month update as part of the detailed design modification phase. The following sketch provides the proposed Level elevation datum points.
LIC-13-0144 Enclosure Page 5 Sketch of Level Elevation Datum Points
LIC-13-0144 Enclosure Page 6 3.0 INSTRUMENTATION DESIGN FEATURES 3.2 Arrangement The OIP states, in part, that SFP level probes are proposed to be installed in the southwest and northeast corners of the SFP (diagonally opposite corners).
Details of the probe locations will be finalized in the design and engineering phase.
Details related to location of the transmitters and the cabling have not been finalized at this point in time and will be part of the design and engineering phase of the project.
Supports for the probes will be designed to shield the components from event-generated missiles. In the conceptual design, the SFP probes bolt to a mounting plate for installation at the corner of the SFP, or a plate for mounting near the side of the SFP. This mounting option will allow the probe to be installed within a few inches of the SFP liner, minimizing the chances of interference with other structures, and occupying limited space on the SFP deck. To the greatest extent possible, the supports will allow the fuel-handling machine to pass over them without interference.
Details of the supports will be addressed in the design and engineering phase of the project. The location of the probes will not interfere with fuel cask handling transfers.
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.
OPPD RAI-2 Response The SFP inside dimensions and anticipated probe locations were transmitted in OPPDs OIP (Reference 1). The sketch provided in Section XVIII of the OIP, indicates the width of the SFP is 20-7, and the length of the pool is 33-3. The exact routing of the cables has not been determined.
The SFP level read out display devices are to be mounted in separate locations. One readout device is proposed to be located in Room 57 near the auxiliary shutdown panel as shown in Attachment A. The other readout device is proposed to be mounted on a wall in Room 69 (upper auxiliary building area) as shown in Attachment C. Note that each sketch is a subset of larger architectural drawings which are provided to illustrate the relationship of the SFP to the general areas proposed for readout displays. The Room 57 sketch is from drawing 11405-A-6 (Attachment B) and the Room 69 sketch is from drawing 11405-A-7 (Attachment D). Note that Room 57 and Room 69 are on different elevations of the plant.
The exact locations have not been determined and are subject to change during the modification design process. Information regarding the exact location of the sensors, read-out display devices, and cable routing will be provided in a future OPPD six-month update.
LIC-13-0144 Enclosure Page 7 3.3 Mounting The OIP states, in part, that Both the primary and backup system will be installed as Seismic Class I to meet the NRC JLD-ISG-2012-03 and NEI 12-02 guidance requirements.
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 connection 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.
OPPD RAI-3a Response The loading on the probe mount and probe body includes both seismic and hydrodynamic loading using seismic response spectra that bounds the site design basis maximum seismic loads applicable to the installation location(s). The static weight load is also accounted for in the modeling described below but is insignificant in comparison to seismic and hydrodynamic loads. Analytic modeling is being performed by the instrument vendor using Institute of Electrical and Electronic Engineers (IEEE)-344:2004 methodology.
The simple unibody structure of the probe assembly make it a candidate for analytic modeling and the dimensions of the probe and complex hydrodynamic loading terms in any case preclude meaningful physical testing.
A detailed computational SFP hydrodynamic model has been developed for the instrument vendor by Numerical Applications, Inc., author of the GOTHIC computational fluid dynamics code. The computational model accounts for multi-dimensional fluid motion, pool sloshing, and loss of water from the pool.
Seismic loading response of the probe and mount is separately modeled using finite element modeling software. The GOTHIC-derived fluid motion profile in the pool at the installation site and resultant distributed hydrodynamic loading terms are added to the calculated seismic loading terms in the finite element model to provide a conservative
LIC-13-0144 Enclosure Page 8 estimate of the combined seismic and hydrodynamic loading terms for the probe and probe mount, specific to the chosen installation location for the probe.
OPPD RAI-3b Response The proximal portion of the level probe is designed to be attached to a Seismic Category I mounting bracket configured to suit the requirements of the FCS SFP. The bracket may be bolted and/or welded to the SFP deck and/or SFP liner/wall according to the requirements of the detailed design and modification process. At this time, detailed information is not available but will be provided in a future OPPD six-month update.
OPPD RAI-3c Response See response to RAI-3b above. At this time, detailed information is not available but will be provided in a future OPPD six-month update.
3.4 Qualification The OIP states, in part, that Instrument channel reliability will be demonstrated via an appropriate combination of design, analyses, operating experience, and/or testing of channel components for the following sets of parameters:
conditions in the area of instrument channel component use for all instrument components, effects of shock and vibration on all instrument channel components, and seismic effects on instrument channel components used during and following a potential seismic event for only installed components.
Augmented quality requirements, similar to those applied to fire protection, will be applied to this project.
Temperature, humidity, and radiation levels consistent with conditions in the vicinity of the SFP and the area of use considering normal operational, event and post-event conditions for no fewer than seven days post-event will be addressed in the engineering and design phase. Examples of post-event (beyond-design-basis) conditions that will be considered are:
radiological conditions for a normal refueling quantity of fuel in the pool.
temperatures of 212°F and 100% relative humidity environment, boiling water and/or steam environment, a concentrated borated water environment.
LIC-13-0144 Enclosure Page 9 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 of the instrument channels 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 [methods listed].
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 Beyond-Design-Basis (BDB) 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.
OPPD RAI-4a Response Temperature: Signal processor: Designed for mild environment installation. Physical testing in an environmental chamber to demonstrate normal operation at the operating temperatures specified for the instrument.
Probe assembly: Qualification by materials properties and use history of substantially similar probe designs in steam generator applications at significantly higher temperatures and pressures and saturated steam environments.
Humidity: Signal processor: Designed for mild environment installation. Physical testing in an environmental chamber to demonstrate normal operation at the operating temperatures specified for the instrument.
Probe assembly: Qualification by materials properties and use history as noted above.
Shock: Signal processor: Physical testing to commercial and/or military standards using shake-table and drop testing.
LIC-13-0144 Enclosure Page 10 Probe assembly: Finite element analysis in conjunction with seismic modeling described in RAI-3a response.
Vibration: Signal processor: Physical testing to applicable commercial and/or military standards using shake-table and drop testing.
Probe assembly: The probe assembly and bracket together form a simple static unibody structure with intrinsic vibration resistance that is additionally subject to substantial damping due to the surrounding water medium. This is planned to be modeled using finite element modeling in conjunction with seismic modeling described above.
Radiation: Signal processor: The Electrical Field Perturbation (EFP) guided radar technology signal processor is installed in a mild environment with radiation levels similar to background radiation, with the acknowledgement that the radiation limit for the signal processor is similar to other commercial-grade complementary-metal-oxide-semiconductor (CMOS)-based electronics. Radiation testing is not planned. It should be noted that the instrument performs self-diagnostics before measurements are obtained and the electronics are easily accessible for periodic replacement.
Probe assembly: Materials properties qualification is used.
OPPD RAI-4b Response These instruments are not required for design basis accidents and as such are not to be designed to worst-case credible design basis loading. They are designed to be reliable as augmented quality systems in accordance with NEI 12-02 guidance.
Signal processor (electronics):
Triaxial shake-table testing is to be performed by the vendor to envelope Seismic Category 1 safe shutdown earthquake (SSE) conditions or site design basis maximum seismic loads (relative to the location where the equipment is mounted) using IEEE-344:2004 methodology.
Probe assembly (level sensor):
Seismic and hydrodynamic finite element analysis is performed by the vendor using relevant IEEE-344:2004 methodology (using enveloping Seismic Category 1 SSE conditions or site design basis maximum seismic loads relative to the location where the equipment is mounted), as described in the RAI-3 response.
OPPD RAI-4c Response With respect to the probe assembly, combined seismic and hydrodynamic analysis will be used to demonstrate that the probe waveguides geometric dimensions do not change significantly as a result of the seismic conditions. In the absence of alteration to the geometric configuration of the probe waveguide there is no mechanism for seismic excitation of the probe assembly to alter system accuracy.
LIC-13-0144 Enclosure Page 11 The accuracy of system electronics will be demonstrated following seismic excitation as part of the seismic testing protocol.
3.5 Independence The OIP states, in part, that The primary and backup instrument channels are of the same technology, are permanently installed, separated by distance and utilize independent power supplies.
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.
OPPD RAI-5a Response FCS has a single spent fuel pool. As shown in Section XVIII of the OIP (Reference 1), the FCS spent fuel pool is between column line 5d and approximately column line 4b. The area noted on the right hand side of the sketch New Fuel Storage & Crating is an open area used only for new fuel receipt/storage and is not flooded. As such, the probes will be installed in only one pool, and are planned to be set at the furthest distance possible from each other in the pool, (i.e., diagonal corners). This anticipated location for each probe is intended to minimize to the greatest extent possible, the potential for falling debris to impact both probes. The vendor will perform additional detailed failures modes and event analysis, and the information will be provided in a future OPPD six-month update.
OPPD RAI-5b Response Detailed information is not available regarding the independent power sources since the modification design process has not been started. The information will be provided in a future OPPD six-month update.
3.6 Power Supplies The OIP states, in part, that
LIC-13-0144 Enclosure Page 12 The two instrumentation channels will each be powered normally by a separate power supply and will have dedicated batteries and local battery chargers. Minimum battery life of 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> will be provided. The battery systems will include provision for battery replacement should the battery charger be unavailable following the event.
Spare batteries will be available. In the event of a loss of normal power, the battery chargers could be connected 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, for normal, post-event, and recovery from the event.
b) If the level measurement channels are to be powered through a battery system (either directly or through an Uninterruptible Power Supply (UPS)), 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 BDB event for the minimum duration needed, consistent with the plant mitigation strategies for BDB external events (Order EA-12-049).
OPPD RAI-6a Response Since the modification design process has not been started, OPPD does not have details regarding electrical AC power sources and capacities for the primary and backup channels.
That information will be provided in a future OPPD six-month update.
OPPD RAI-6b Response When the instrument is powered through the battery, the instrument configuration is to be established with an automated sample rate consistent with seven days continuous operation. The sample rate estimates have been developed by the vendor using conservative instrument power requirements and measured battery capacity with drawdowns during and following exposure of the batteries to their maximum operating temperature for up to seven days. Permanent installed battery capacity for seven days continuous operation is planned consistent with NEI 12-02 duration without reliance on or crediting of potentially more rapid FLEX Program power restoration. Batteries are readily replaceable via spare stock without the need for recalibration to maintain instrument accuracy.
3.7 Accuracy The OIP states, in part, that Instrument channels will be designed such that they will maintain their design accuracy following a power interruption or change in power source without recalibration.
LIC-13-0144 Enclosure Page 13 Accuracy will consider SFP conditions, e.g., saturated water, steam environment, or concentrated borated water. Additionally, instrument accuracy will be sufficient to allow trained personnel using plant procedures to determine when the actual level exceeds the specified lower level of each indicating range (levels 1, 2, and 3) without conflicting or ambiguous indication. The accuracy will be within the resolution requirements of Figure 1 of NEI 12-02.
RAI-7
Please provide the following:
a) An estimate of the expected instrument channel accuracy performance (e.g., in %
of span) under both: (a) normal SFP level conditions (approximately Level 1 or higher) and (b) at the BDB 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.
OPPD RAI-7a Response
- a. The expected instrument channel absolute accuracy under normal spent fuel pool level conditions (Level 1 or higher) is approximately +/- 0.3% of the span.
- b. Expected absolute accuracy under beyond-design-basis conditions is approximately
+/- 0.3% of the span at Level 2 and 3 datum points.
OPPD RAI-7b Response In general, relative to normal operating conditions, any applicable calibration procedure tolerances (or acceptance criterion) are planned to be established based on manufacturers stated/recommended reference accuracy (or design accuracy). The methodology used is planned to be captured in plant procedures and/or programs that are yet to be developed.
More information will be provided in a future OPPD six-month update regarding plant procedures and/or programs related to channel design accuracy.
3.8 Testing The OIP states, in part, that Instrument channel design will provide for routine testing and calibration consistent with Order EA-12-051 and the guidance in NEI 12-02.
LIC-13-0144 Enclosure Page 14
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.
OPPD RAI-8a Response The instrument automatically monitors the integrity of its level measurement system using in-situ capability. Deviation of measured test parameters from manufactured or as-installed configuration beyond a configurable threshold prompts operator intervention.
Periodic calibration checks of the signal processor electronics to extrinsic National Metrology Institute (NMI) traceable standards can be achieved with standard measurement and test equipment.
The probe itself is a perforated tubular coaxial waveguide with defined geometry and is not calibrated. It is to be periodically inspected electromagnetically using Time Domain Reflectometry (TDR) to demonstrate that the probe assembly meets manufactured specification and visually to demonstrate that there has been no mechanical deformation or fouling.
Each instrument electronically logs a record of measurement values over time in non-volatile memory that can be compared to demonstrate constancy, including any changes in pool level, such as that associated with the normal evaporative loss/refilling cycle. The channel level measurements can be directly compared to each other (i.e., regular cross-channel comparisons). Existing permanently installed SFP level instrumentation or other direct measurements of SFP level may be used for diagnostic purposes if cross-channel comparisons are anomalous.
OPPD RAI-8b Response As stated above, each instrument electronically logs a record of measurement values over time in non-volatile memory that can be compared to demonstrate constancy, including any
LIC-13-0144 Enclosure Page 15 changes in pool level, such as that associated with the normal evaporative loss/refilling cycle. The channel level measurements can be directly compared to each other (i.e.,
regular cross-channel comparisons). Existing permanently installed SFP level instrumentation or other direct measurements of SFP level may be used for diagnostic purposes if cross-channel comparisons are anomalous.
OPPD RAI-8c Response Operator performance tests (functional checks) are automated and/or semi-automated (i.e.,
require limited operator interaction) and are performed through the instrument menu software as initiated by the operator. There are a number of other internal system tests that are performed by system software on an essentially continuous basis without user intervention but can also be performed on an on-demand basis with diagnostic output to the display for the operator to review. Other tests such as menu button tests, level alarm, and alarm relay tests are initiated manually by the operator. Operator performance checks are described in detail in the Vendor Operators Manual, and the applicable information will be transferred to plant operating procedures.
Operator performance tests are planned to be performed periodically as recommended by the equipment vendor, (e.g., quarterly) but no less often than the calibration interval of two years.
Channel functional tests with limits established in consideration of vendor equipment specifications are to be performed using Operations procedures at appropriate frequencies established equivalent to or more frequently than existing spent fuel pool instrumentation (SFPI). Details regarding the frequency of channel functional testing will be established as part of the detailed design process and will be provided in a future OPPD six-month update.
Manual calibration tests are as described in the response to RAI-7b above.
Manual calibration and operator performance checks are to be performed in a periodic scheduled fashion with additional maintenance as needed when flagged by the systems automated diagnostic testing features. Details regarding the manual calibration and operator performance checks will be established as part of the detailed design process and will be provided in a future OPPD six-month update.
Channel calibration tests per maintenance procedures with limits established in consideration of vendor equipment specifications are to be performed at frequencies established in consideration of vendor recommendations.
OPPD RAI-8d Response Periodic (e.g., quarterly or monthly) review of the system level history and log files and routine attention to any warning message on the system display is recommended by the vendor. Formal calibration checks are recommended by the vendor on a two-year interval to demonstrate calibration to external National Institute of Standards and Technology (NIST) traceable standards. Formal calibration check surveillance interval and timing would be established consistent with applicable guidance [i.e., NEI 12-02 Section 4.3:, on a refueling outage interval basis and within 60 days of a planned refueling outage considering normal
LIC-13-0144 Enclosure Page 16 testing scheduling allowances (e.g., +/- 25%)]. Items such as system batteries are to be assessed under the Preventive Maintenance (PM) Program for establishment of replacement frequency with PM timing/performance being controlled via tasks in the PM Program.
3.9 Display The OIP states, in part, Planned locations for SFP level displays will be in a mild environment of the Auxiliary Building providing adequate protection from temperature, humidity, and radiation.
Preliminarily, one channel will be located in a remote location in the Ventilation Equipment Room near FLEX strategy equipment, and one SFP level display is to be mounted in the Alternate Shutdown Panel in the Upper Electrical Penetration Room.
Both locations have ready access by operators.
Remote indication will be provided in the alternate safe shutdown panel in the Auxiliary Building Upper Electrical Penetration Room. The other remote indication will be provided with portable equipment located near FLEX equipment along the north wall of the Ventilation Equipment Room. It has not been determined at this point in time if a readout will be provided in the control room or with the plant computer display system. That determination will be made during the design and engineering phase.
The display in the alternate shutdown panel Upper Electrical Penetration Room will be:
promptly accessible to the appropriate plant staff giving appropriate consideration to various drain down scenarios, outside of the area surrounding the SFP floor, e.g., an appropriate distance from the radiological sources resulting from an event impacting the SFP, inside a structure providing protection against adverse weather, and outside of any very high radiation areas or LOCKED HIGH RAD AREA during normal operation.
Each instrument channel (Primary and Backup) will have the capability to drive an external remote 4 - 20 milliamp (ma) loop that can be used to provide level indication at a second display location or be used as an input to the plant computer. Failure of the external remote 4 - 20 ma signal will not adversely impact the primary display located in the transmitter (electronics) enclosure.
RAI-9
Please provide the following:
LIC-13-0144 Enclosure Page 17 a) Since both the primary and backup display locations are not in the main control room, provide a description of the display location that addresses primary and alternate access route evaluation continuous, 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.
b) The reasons justifying why the locations selected will enable the information from these instruments to be considered promptly accessible. Include consideration of various drain-down scenarios.
c) Justification for use of the process computer system for relaying information to emergency decision makers, and describe the reliability design criteria applicable to the process computer system under BDB conditions.
OPPD RAI-9a Response The primary and backup display locations were selected because those locations are in close proximity to where the personnel primarily responsible for FLEX equipment deployment and operation will be located. Spent fuel pool level control will be the responsibility of the Auxiliary Building Operator also known as the Equipment Operator Nuclear Auxiliary (EONA) position, who will normally be stationed at the location where the primary display will be mounted. A preliminary walkdown was performed to ensure that short-term (< 24 hour2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />) FLEX deployment actions could be accomplished using existing personnel. The primary and secondary displays are located in FLEX equipment deployment paths, located entirely within Seismic Class 1 structures and are either adjacent to or closer to the location where local makeup flow to the spent fuel pool will be controlled than is the control room. This improves resource availability and response time for monitoring SFP level. Primary and alternate access and egress paths to the display locations are provided in the FCS FLEX Overall Integrated Plan (Reference 2, Enclosure, Attachment 3, Section A).
The primary display location will be located on the upper level of the auxiliary building adjacent to the proposed location of the manifold that will be used to control the distribution of water from FLEX pumps to the emergency feedwater storage tank (EFWST), the reactor coolant system (RCS) and the spent fuel pool (SFP). This location was selected due to its proximity to a current Appendix R access path (inside a Seismic Class 1 structure) and the intended FLEX water supply (the safety injection refueling water tank - SIRWT). The exact location for the secondary display is on the wall north of the FLEX Valve Station Deployment Location, which can be seen in Reference 2, Enclosure, Attachment 3, Figure A-4, Section B-8. OPPD is evaluating habitability of this location as part of the FLEX implementation project and will perform modifications if necessary to ensure prompt access will be maintained throughout any postulated event where flow control and monitoring of SFP level is necessary.
The secondary display location is adjacent to the electrical switchgear room where installed electrical equipment would be manually operated in support of FLEX deployment and implementation. This location at the remote shutdown panel in the upper electrical penetration room is in an area that is physically separated from the primary monitoring location, to allow for scenarios where continuous manning of the primary control location is
LIC-13-0144 Enclosure Page 18 not warranted or desirable. The secondary monitoring location allows rapid access to and egress from the control room (CR) and the primary FLEX control station in the auxiliary building via pathways that are enclosed within seismically qualified structures. The location for the secondary display is near panel AI-185 which can be seen in Reference 2, Enclosure, Attachment 3, Figure A-3, Section E-6. OPPD is evaluating habitability of this location as part of the FLEX implementation project. Due to the separation of this location from hot components and fluid systems, OPPD does not expect that any modifications will be necessary to ensure habitability in this area.
It is not anticipated that the SFP level would change rapidly enough to demand the need for rapid communications. The operators would first employ radio communications or the Spectralink system as a means of communication. If the radio communications or Spectralink systems are non-functional, the gai-tronics system is assumed available because it is powered from the station batteries and is located in Seismic Class 1 structures.
The operators can walk to the CR if they need to talk to Command and Control personnel.
Since the EONA will be the person primarily responsible for maintaining SFP level and will have procedural direction for maintaining said level within a certain band, there is no need for immediate direction from the CR. If the secondary location has to be used, the EONA and Turbine Building Operator also known as the Equipment Operator Nuclear Turbine (EONT) can communicate face-to-face at the radiologically controlled area (RCA) access point, which is easily reachable from the switchgear room via the back door next to the FCS radiological area. There are at least three (3) exit points: two (2) within a Seismic Class 1 structure that has access to the alternate shutdown panel.
If, during FLEX project development, OPPD determines that habitability of either the primary or secondary SFP monitoring location cannot be supported, a suitable alternate location will be selected. Should that happen, the new location will be provided in a future OPPD six-month update.
OPPD RAI-9b Response The RAI-9a response provides justification for the information from these instruments to be promptly accessible. Aside from the habitability issues discussed above, various drain-down scenarios were considered and the dose at the primary and secondary monitoring locations was found to be within acceptable limits.
OPPD RAI-9c Response Inputs to the process computer system are not intended to be used for Beyond Design Basis (BDB) events. This discussion was provided in the submittal only as supporting information.
4.0 PROGRAM FEATURES 4.1 Procedures The OIP states, in part, that
LIC-13-0144 Enclosure Page 19 Procedures will be developed using guidelines and vendor instructions to address the maintenance, operation, and abnormal response issues associated with the new SFP instrumentation consistent with NEI 12-02.
Procedures will address a strategy to ensure SFP water level addition is initiated at an appropriate time consistent with implementation of NEI 12-06, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide (Reference 6). The details of the procedure implementation will be linked to NRC Order 12-049, Issuance of Order to Modify Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Reference 8). Procedures will address the following situations:
If, at the time of an event or thereafter until the unit is returned to normal service, an instrument channel ceases to function, its function will be recovered within a period of time consistent with the emergency conditions that may apply at the time.
If, at the time of an event or thereafter until the unit is returned to normal service, an instrument channel component must be replaced, we may use commercially available components that may or may not meet all of the qualifications (Section IX) to maintain the instrument channel functionality.
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.
OPPD RAI-10a Response Development of operating, calibration/test, maintenance, and inspection procedures will be performed as part of the detailed design process. The procedures will be subject to the programmatic controls of the FCS FLEX Program as described in the FCS FLEX OIP (Reference 2).
OPPD RAI-10b Response Specific technical objectives for the above procedures will be developed as part of the detailed design process. OPPD does not anticipate using portable spent fuel level monitoring equipment. A description of the objectives and a brief outline of the procedures to be developed will be provided in a future OPPD six-month update.
LIC-13-0144 Enclosure Page 20 4.2 Testing and Calibration The OIP states, in part, that Processes will be established and maintained for scheduling and implementing necessary testing and calibration of the primary and backup spent fuel pool level instrument channels to maintain the instrument channels at the design accuracy.
Testing and calibration of the instrumentation will be consistent with vendor recommendations and any other documented basis. Calibration will be specific to the mounted instrument and the monitor.
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 the compensatory actions to be taken in the event that one of the instrument channels cannot be restored to functional status within 90 days.
OPPD RAI-11a Response SFPI channel/equipment maintenance/preventative maintenance and testing program requirements to ensure design and system readiness are to be established in accordance with utility processes and procedures and in consideration of vendor recommendations to ensure that appropriate regular testing, channel checks, functional tests, periodic calibration, and maintenance is performed. Subject maintenance and testing program requirements are to be developed during the SFPI modification design process. Specific details regarding the maintenance and testing program will be provided in a future OPPD six-month update when the information becomes available.
OPPD RAI-11b Response Detailed information is not available at this time but will be provided in a future OPPD six-month update.
OPPD RAI-11c Response Both primary and backup SFPI channels incorporate permanent installation (with no reliance on portable, post-event installation) of relatively simple and robust augmented quality equipment.
Permanent installation coupled with the stocking of adequate spare parts reasonably diminishes
LIC-13-0144 Enclosure Page 21 the likelihood that a single channel is out of service for an extended period. It follows that this also greatly diminishes the likelihood that both channels are out-of-service for an extended period.
References
- 1. Letter from OPPD (L. P. Cortopassi) to NRC (Document Control Desk), Fort Calhoun Station Spent Fuel Pool Instrumentation Overall Integrated Plan, dated February 28, 2013 (ML13059A268) (LIC-13-0011)
- 2. Letter from OPPD (L. P. Cortopassi) to NRC (Document Control Desk), Omaha Public Power Districts Overall Integrated Plan in Response to March 12, 2012, Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond Design Basis External Events (Order Number EA-12-049), dated February 28, 2013 (ML13064A298) (LIC-13-0019)
LIC-13-0144 Enclosure Attachment A Page 1 Proposed Location in Room 57
LIC-13-0144 Enclosure Attachment B Page 1 Drawing 11405-A-6 R87 Primary Plant Ground Floor Plan El. 1,013 ft.
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LIC-13-0144 Enclosure Attachment C Page 1 Proposed Location in Room 69
LIC-13-0144 Enclosure Attachment D Page 1 Drawing 11405-A-7 R31 Primary Plant Intermediate & Operating Floor Plans El. 1,025 ft.