GNRO-2013/00057, Response to Request for Additional Information Regarding Overall Integrated Plan for Reliable Spent Fuel Pool Instrumentation (Order EA-12-051)
| ML13246A175 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 08/29/2013 |
| From: | Kevin Mulligan Entergy Nuclear Operations |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| EA-12-051, GNRO-2013/00057 | |
| Download: ML13246A175 (24) | |
Text
Entergy Operations, Inc.
P. O. Box 756 Port Gibson, MS 39150 Kevin J. Mulligan Site Vice President Grand Gulf Nuclear Station Tel. (601) 437-7500 GNRO-2013/00057 August 29, 2013 U.S. Nuclear Regulatory Commission AnN: Document Control Desk Washington, DC 20555-0001
SUBJECT:
Response to Request for Additional Information Regarding Overall Integrated Plan for Reliable Spent Fuel Pool Instrumentation (Order EA-12-051 )
Grand Gulf Nuclear Station, Unit 1 Docket No. 50-416 License No. NPF-29
REFERENCES:
- 1. NRC Order Number EA-12-051, Order to Modify Licenses with Regard to Reliable Spent Fuel Pool (SFP) Instrumentation, dated March 12, 2012 (GNRI-2012/00057, ML12054A682)
- 2. Entergy Letter to NRC, Overall Integrated Plan in Response to March 12,2012, Commission Order Modifying License with Regard to Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051), dated February 26,2013 (GNRO-2013/00016, ML13064A417)
- 3. NRC Letter to Entergy, Request for Additional Information Regarding Overall Integrated Plan for Reliable Spent Fuel Pool Instrumentation (Order EA-12-051), dated July 30,2013 (GNRI-2013/00129, ML13207A124)
Dear Sir or Madam:
On March 12, 2012, the U.S. Nuclear Regulatory Commission (NRC) issued an order (Reference 1) to Entergy Operations, Inc. (Entergy). Reference 1 required submission of an overall integrated plan (OIP) which was provided via Reference 2. By Reference 3, the NRC issued requests for additional information (RAls). The attachment provides the responses to these RAls for Grand Gulf Nuclear Station (GGNS). The RAI responses provided in the attachment are based on the current preliminary design information/vendor input which is subject to change as the design is finalized.
This letter contains no new regulatory commitments. Should you have any questions regarding this submittal, please contact Mr. Christopher R. Robinson, Licensing Manager, at (601) 437-7326.
GNRO-2013/00057 Page 2 of 2 I declare under penalty of perjury that the foregoing is true and correct; executed on August 29, 2013.
Sincerely, KJM/slw
Attachment:
Response to Request for Additional Information cc: U. S. Nuclear Regulatory Commission ATTN: Steven A. Reynolds Acting Regional Administrator, Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 U. S. Nuclear Regulatory Commission ATTN: Mr. Alan Wang, NRRlDORL Mail Stop OWFN/8 B1 Washington, DC 20555-0001 NRC Senior Resident Inspector Grand Gulf Nuclear Station Port Gibson, MS 39150
Attachment to GNRO-2013/00057 Response to Request for Additional Information
Attachment to GNRO-2013/00057 Page 1 of 21 RESPONSE TO REQUEST FOR ADDITIONAL INFORMATiON OVERALL INTEGRATED PLAN FOR RELIABLE SPENT FUEL POOL INSTRUMENTATION (ORDER EA-12-051)
GRAND GULF NUCLEAR STATION, UNIT NO.1 50-416 The format for the Request for Additional Information (RAI) responses below is as follows. The RAI is listed in its entirety as received from the U.S. Nuclear Regulatory Commission (NRC).
This is followed by the Grand Gulf Nuclear Station (GGNS) RAI response to the individual question.
1.0 INTRODUCTION
By letter dated February 26, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13064A417), Entergy Operations, Inc. (Entergy, the licensee),
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 requirements for Reliable Spent Fuel Pool (SFP) Instrumentation (Order Number EA-12-051; ADAMS Accession No. ML12054A679) for Grand Gulf Nuclear Station, Unit 1 (GGNS). 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 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 Poollnstrumentation," Revision 0, dated August 29, 2012 (ADAMS Accession No. ML12221A339).
The NRC staff has reviewed your February 26, 2013, response and determined that the following request for additional information (RAI) is needed to complete its technical review. The NRC staff requests that you respond within the 30 days or provide the date this information will be submitted.
2.0 LEVELS OF REQUIRED MONITORING The OIP states, in part, that Level 1 is the level adequate to support operation of the normal fuel pool cooling system. It is the higher of the following two points:
The level at which reliable suction loss occurs due to uncovering the coolant inlet pipe or any weirs or vacuum breakers associated with suction loss. For GGNS, this level, (1) is established based on the level at which siphon break occurs which is at elevation 204' feet 8" inches (Reference 6). This elevation is above the point where the fuel pool cooling pumps trip (Reference 7).
(2) The level at which the normal fuel pool cooling pumps lose required NPSH [net positive suction head] assuming saturated conditions in the pool. The fuel pool cooling pumps would trip
Attachment to GNRO-2013/00057 Page 2 of 21 based on water level in pool drain tank. This level would be lower than the level determined in (1) above.
The higher of the above points is (1). Therefore, LEVEL 1 is elevation 204 feet 8 inches.
Level 2 is the level adequate to provide substantial radiation shielding for a person standing on the spent fuel pool operating deck. Level 2 may be based on either of the following:
(1) 10 feet +/- 1 foot above the highest point of any fuel rack seated in the spent fuel pool. The elevation associated with this level is 192 feet 2.125 inches +/- 1 foot (Le., Level 3 + 10 feet).
(2) A designated level that provides adequate radiation shielding to maintain personnel dose within acceptable limits while performing local operations in the vicinity of the pool. This level is based on plant-specific or appropriate generic shielding calculations. The elevation associated with this level is not calculated since item (1) is used to establish Level 2 as permitted by NEI 12-02 Revision 1.
Therefore, LEVEL 2 is elevation 192 feet - 2.125 inches (Le., 10 feet above Level 3.)
The equipment and instructions to reestablish SFP inventory will be provided as required by NE112-06 Revision 1 (Reference 3). This guidance will require action to reestablish SFP inventory upon or before reaching Level 3.
Level 3 is the level where fuel remains covered. It is defined as the highest point of any fuel rack seated in the spent fuel pool (within +/- 1 foot).
The highest point of any fuel rack seated in the spent fuel pool is elevation 182 feet 2.125 inches (References 8 and 9). Therefore, Level 3 is elevation 182 feet 2.125 inches +/- 1 foot band.
The SFP level instrument span will extend down to at least 3 inches below the upper limit of the range of LEVEL 3 to account for accuracy or instrument loop uncertainty. Therefore, the SFP level probe will extend down to at least elevation 182 feet 11.125 inches.
RAI-1
Please provide the following:
a) 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). Please 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.
Attachment to GNRO-2013/00057 Page 3 of 21 b) The OIP states, in part, in Section 8, Mounting, Other hardware stored in the SFP will be evaluated to ensure that it does not adversely interact with the SFP instrument probes during a seismic event.
Please provide a discussion regarding dose rates for stored spent fuel versus that of other material that may be stored in the pool and the potential impact on the evaluation for Level 2.
Response to RAI-1 a:
The requested information is provided in Figure 1. The figure indicates Levels 1, 2, and 3 as well as the approximate location of the proposed mounting bracket incorporating the Seismic Category I attachment. The sensor is a perforated tubular coaxial waveguide that provides continuous level measurement axially and is sensitive over its entire length. These sketches apply to both the primary and backup channels.
The spent fuel pool (SFP) level lower instrument span or probe bottom extends down to at least three inches below the upper limit of the range of Level 3 to account for channel accuracy or instrument loop uncertainty. Therefore, the SFP level probe bottom/span extends down to at least elevation 182'-11 1/8" (see Figure 1). The SFP level upper instrument span includes the high water level alarm elevation.
Response to RAI-1 b:
Section 2.3.2 of NEI 12-02 states that Level 2 represents the range of water level where any necessary operations in the vicinity of the spent fuel pool can be completed without significant dose consequences from direct gamma radiation from the stored spent fuel. NEI 12-02 gives two options to determine Level 2. The first option defines Level 2 as ten feet above the highest point of any fuel rack. The second option states that Level 2 is based on the need to provide adequate radiation shielding to maintain personnel radiological dose levels within acceptable limits while performing local operations in the vicinity of the pool. The evaluation of the level needed to provide personnel protection should consider the scope of the local operations, including installation of portable SFP instrument channel components, along with the emergency conditions that may apply at the time of operator actions.
Level 2 is not adjusted for hardware stored in the spent fuel pool, since NEI 12-02 states that Level 2 is based on the dose consequences from direct gamma radiation from the stored spent fuel.
3.0 INSTRUMENTATION DESIGN FEATURES 3.2 Arrangement The OIP states, in part, that Level instruments will be installed in the approximate locations shown on Attachment 1. Separation of the channels/probes reduces the potential for falling debris or missiles affecting both channels of instrumentation. This placement, coupled with
Attachment to GNRO-2013/00057 Page 4 of 21 separate routing paths for cables and use of rigid conduit, provides reasonable protection against falling debris and structural damage.
Instrument power is derived from the display/processors. The location of the display/processors is in the Computer Room in the control building as shown on Attachments 1 and 2. The Computer Room is expected to be a mild environment after a Beyond Design Basis External (BDBE) event and can be easily accessed from the MCR [Main Control Room]; therefore, personnel can promptly obtain readings from the display. This building provides adequate protection against the effects of temperature, flood, humidity, radiation, seismic events, and missile hazards.
RAI-2
Please modify the marked-up plant drawing of the plan view of the SFP area to depict 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.
Response to RAI-2:
Figure 2 shows the approximate locations of the SFPI probes along with the inside dimensions of the spent fuel pool. The conceptual routing of the cables in the refueling floor area is available in Attachment 1 to the GGNS OIP. Detailed design has not been completed at this time.
3.3 Mounting The OIP states, in part, that Both the primary and backup system will be installed as seismic category I to meet the NRC JLD-ISG-2012-03 and NEI 12-02 guidance requirements.
Other hardware stored in the SFP will be evaluated to ensure that it does not adversely interact with the SFP instrument probes during a seismic event.
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. Please 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. Please indicate in a schematic the portions of the
Attachment to GNRO-2013/00057 Page 5 of 21 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.
d) A description of how other material stored in the SFP will not create adverse interaction with the fixed instrument location(s).
Response to RAI-3a:
The loading on the probe mount and probe body includes both seismic and hydrodynamic loading using seismic response spectra that bound the GGNS 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 makes 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 con$ervative estimate of the combined seismic and hydrodynamic loading terms for the probe and probe mount, specific to the chosen installation location for the probe.
Response to RAI-3b:
The proximal portion of the level probe is designed to be attached near its upper end (refer to vendor schematic Figure 3) to a Seismic Category I mounting bracket configured to suit the requirements of a particular SFP. The bracket may be bolted and/or welded to the SFP deck and/or SFP liner/wall according to the requirements of the particular installation per Seismic Category I requirements.
Response to RAI-3c:
See RAI-3b response above.
Attachment to GNRO-2013/00057 Page 6 of 21 Response to RAt-3d:
An evaluation of non-nuclear material inventory located in the SFP will be performed during the SFPI modification process. Non-nuclear material access to the SFP is governed by 17-S 301, NNM Movement and Inventory Control. This procedure will be used to prevent any instrument interference from non-nuclear materials.
3.4 Qualification The OIP states, in part, that Design criteria will ensure instrument channel reliability during normal, event, and post-event conditions for no fewer than seven days or until off-site resources can be deployed.
Analyses, operating experience, and/or manufacturer testing of channel components will be used to validate design criteria ...
Components in the area of the SFP will be designed for the temperature, humidity, and radiation levels expected during normal, 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...
Equipment located in the SFP will be qualified to withstand a total accumulated dose of expected lifetime at normal conditions plus accident dose received at post event conditions with SFP water level within 1 foot of the top of the fuel rack seated in the spent fuel pool (Level 3).
Components of the instrument channels will be qualified for shock and vibration using one or more of the following methods...
Components will be 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 the licensee intends to apply to demonstrate the reliability of the permanently installed equipment under beyond-design-basis (BOB) ambient temperature, humidity, shock, vibration, and radiation conditions.
b) A description of the testing and/or analyses that will be conducted to provide assurance that the equipment will perform reliably under the worst-case credible design basis loading at the location where the equipment will be mounted. Include a discussion of this seismic reliability demonstration as it applies to a) the level sensor mounted in the SFP area, and b) any control boxes, electronics, or read-out and re-transmitting devices that
Attachment to GNRO-2013/00057 Page 7 of 21 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 to RAI-4a:
As stated in NEI 12-02, "Components in the area of the SFP will be designed for the temperature, humidity, and radiation levels expected during normal, event, and post-event conditions ...." Components in other areas are planned to be designed for their corresponding maximum conditions. The discussion below describes the testing and qualification intended to demonstrate equipment reliability as needed for the expected conditions associated with the SFP level channel active components (signal processor and probe assembly including vendor-supplied hard-line coaxial cable pigtail). Class 1E nuclear-qualified interconnecting coaxial cable is planned to be utilized between the vendor-supplied probe coaxial cable pigtail and the signal processor / display located in the Control Building.
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 humidity 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.
Probe assembly: Finite element analysis in conjunction with seismic modeling described above.
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
Attachment to GNRO-2013/00057 Page 8 of 21 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 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.
Response to RAI*4b:
Signal processor (electronics): Triaxial shake-table testing is planned to be performed by the vendor to envelope seismic category 1 safe shutdown earthquake (SSE) conditions or GGNS 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 GGNS design basis maximum seismic loads relative to the location where the equipment is mounted), as described in the RAI-4a response above.
Response to RAI-4c:
With respect to the probe assembly, combined seismic and hydrodynamic analysis will be used to demonstrate that the probe waveguide's 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.
The accuracy of system electronics will be demonstrated following seismic excitation as part of the seismic testing protocol.
3.5/ndependence The OIP states, in part, that The primary instrument channel will be independent of the backup instrument channel.
Independence is obtained by physical separation of components between channels and the use of normal power supplied from separate 120VAC (Volts Alternating Current) battery-backed instrument buses. Independence of power sources is described in Section 11. The two (2) permanently mounted instruments in the pool are physically separated as described in Sections 6 and 7.
Attachment to GNRO-2013/00057 Page 9 of 21
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 Response to RAI-5a:
The primary instrument (Channel A) will be located in the southeast corner of the SFP, while the backup instrument (Channel B) will be located in the northeast corner of the SFP. Locating the new instruments across the pool from each other takes advantage of the distance between the probes for missile and debris protection.
The conceptual design provides two level instruments in the Spent Fuel Pool (SFP) with cabling routed to two display/processors, both mounted in existing panels in the Computer & Control Panel Room located on the 148' elevation in the Control Building. Power for each channel is provided from independent 120VAC, 60 Hertz (Hz) power sources. Backup power is provided by a battery capable of providing continuous display operation for at least three days. The battery power will be provided to the display/processor. The design prevents failure of a single channel from causing the alternate channel to fail.
Response to RAI-5b:
The design provides two identical non-safety related wide-range level instruments which feed two independent trains of non-safety cable and indicators to provide a highly reliable remote display of SFP water level. Physical separation of the two channels will be accomplished by separately routing cable and conduit as much as practical. The use of raceways (I.e., conduit or covered trays where appropriate for existing hazards) will provide additional protection from damage due to debris during a BOB event.
Each display/processor will have a battery installed adjacent to the display enclosure which is capable of providing power for at least three days.
3.6 Power Supplies The OIP states, in part, that The power supplies for the instrument channels are shown on Attachment 2 and arranged as follows:
Attachment to GNRO-2013/00057 Page 10 of 21
- Each instrument channel is normally powered from 120VAC 60 Hz (Hertz) plant power to support continuous monitoring of SFP level. The primary channel receives power from a different 480V bus than the backup channel. Therefore, loss of anyone 480V bus does not result in loss of normal 120VAC power for both instrument channels.
- On loss of normal 120VAC power, each channel's UPS (uninterruptible power supply) automatically transfers to a dedicated backup battery. If normal power is restored, the channel will automatically transfers back to the normal AC power.
- The backup batteries are maintained in a charged state by commercial-grade uninterruptible power supplies. The batteries are sized to be capable of supporting intermittent monitoring for a minimum of 3 days of operation. This provides adequate time to allow the batteries to be replaced or until off-site resources can be deployed by the mitigating strategies resulting from Order EA-12-049 Revision O.
- An external connection permits powering the system from any portable DC (direct current) source.
- Instrument accuracy and performance are not affected by restoration of power or restarting the processor.
RAI-6
Please provide the following:
a) A description of the normal electrical AC power sources and capacities for the primary and backup channels. Please provide justification for using a common 480 VAC motor control center for the normal feed to both 120 VAC instrument buses, including the contingency plans that will be implemented in the event that power cannot be restored to that particular 480 VAC bus within the required mitigating strategies time frame following a BOB loss of all AC power.
b) 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 BOB event for the minimum duration needed, consistent with the plant mitigation strategies for BOB external events (Order EA-12-049).
Response .to RAI-6a:
The Channel A power supply is 120VAC UPS Power Distribution Pane11Y71. This UPS receives power from either 480 Volts (V) motor control center (MCC) 15B42 or 125V DC Bus 11 DO. The battery for 125V DC Bus 11 DO, 103, is charged by 480V load centers 15BA1 and 15BA2 through a load sharing device.
The Channel B power supply is 120V AC UPS Power Distribution Panel 1Y74. This UPS receives power from either 480V MCC 15B42 or 125V DC Bus 11 OK. The battery for 125V DC Bus 11 OK, 1K3, is charged by 480V LCCs 15BA1 and 15BA2 through a load sharing device.
Power is supplied to 480V MCC 15B42 via 480V LCC 15BA4.
NEI 12-02 states that the normal electrical power supply for each channel shall be provided by different sources such that the loss of one of the channels primary power supply will not result in
Attachment to GNRO-2013/00057 Page 11 of 21 a loss of power supply function to both channels of SFP level instrumentation. The channel power supplies are independent as specified in NEI 12-02. The loss of the common 480V MCC 15B42 does not result in the loss of 120V AC UPS Panels 1Y71 and 1Y74, because the UPS panels receive power from different 125V DC Buses via inverters as discussed above.
Therefore, no contingency plans are necessary in the event that power cannot be restored to the particular 480VAC bus following an extended loss of AC power.
Additionally, each channel has its own backup replaceable battery with a planned installed seven day capacity. Refer to the RAI-6.b response for more detail regarding the backup batteries.
Response to RAI-6b:
The sample rate estimates have been developed by the vendor using conservative instrument power requirements and measured battery capacity with draw-downs during and following exposure of the batteries to their maximum operating temperature for up to seven days. The instrument configuration is planned to be established for an automated sample rate when under battery power consistent with seven days continuous operation (three days minimum).
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 accuracy of the instrument. These measures ensure adequate power capacity and margin.
3.7 Accuracy The OIP states, in part, that Accuracy will be consistent with the guidelines of NRC JLD-ISG-2012-03 Revision 0 and NEI 12-02 Revision 1. Accuracy and indication features are as follows:
- Accuracy: The absolute system accuracy is better than +/- 3 inches. This accuracy is applicable for normal conditions and the temperature, humidity, chemistry, and radiation levels expected for BDBE event conditions.
- Trending: The display trends and retains data when powered from either normal or backup power.
- Restoration after Loss of Power: The system automatically swaps to available power (backup battery power or external DC source) when normal power is lost. Neither the source of power nor system restoration impact accuracy. Previously collected data is retained.
- Diagnostics: The system performs and displays the results of real-time information related to the integrity of the cable, probe, and instrument channel.
Attachment to GNRO-2013/00057 Page 12 of 21
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 BOB conditions (i.e., radiation, temperature, humidity, post-seismic, and post-shock conditions) that would be present if the SFP level were at the Level 2 and Level 3 datum points.
b) A description of the methodology that will be used for determining the maximum allowed deviation from the instrument channel design accuracy that will be employed under normal operating conditions as an acceptance criterion for a calibration procedure to flag to operators and to technicians that the channel requires adjustment to within the normal condition design accuracy.
Response to RAI-7a:
The instrument channel level accuracy will be specified as +/- 3.0 inches for all expected conditions. The expected instrument channel accuracy performance would be approximately
+/-1 % of span (based on the sensitive range of the detector).
Response to RAI-7b:
In general relative to normal operating conditions, any applicable calibration procedure tolerances (or acceptance criterion) are planned to be established based on manufacturer's stated/recommended reference accuracy (or design accuracy). The methodology used is planned to be captured in plant procedures and/or programs.
3.8 Testing The OIP states, in part, that Testing and calibration will be consistent with the guidelines of NRC JLO-ISG-2012-03 Revision 0 and NEI 12-02 Revision 1 and vendor recommendations.
The display/processor performs automatic in-situ calibration and automatically monitors for cable, connector, and probe faults using time domain reflectometry (TOR) technology.
Channel degradation due to age or corrosion is not expected but can be identified by monitoring trends.
Station procedures and preventive maintenance tasks will be developed to perform required surveillance testing, calibration, backup battery maintenance, functional checks, and visual inspections of the probes.
Attachment to GNRO-2013/00057 Page 13 of 21
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. Please 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 to RAI-8a:
The level 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 Institute of Standards and Technology (NIST)-traceable standards can be achieved through the use of standard measurement and test equipment.
The probe itself is a perforated tubular coaxial waveguide with defined geometry and is not calibrated. It is planned to be periodically inspected electromagnetically using time-domain reflectometry (TOR) at the probe hardline cable connector to demonstrate that the probe assembly meets manufactured specification and visually to demonstrate that there has been no mechanical deformation or fouling.
Periodic testing and calibration will be proceduralized as discussed in the response to RAI-Bc.
Response to RAI-8b:
Each instrument electronically logs a record of measurement values over time in non-volatile memory that is 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 (Le., regular cross-channel comparisons). The two displays are installed in close proximity to each other, thus simplifying
Attachment to GNRO-2013/00057 Page 14 of 21 cross channel checks. Direct measurements of SFP level may be used for diagnostic purposes if cross-channel comparisons are anomalous.
Channel checks will be proceduralized as discussed in the response to RAI-8c.
Response to RAI-8c:
Performance tests (functional checks) are automated and/or semi-automated (requiring limited operator interaction) and are performed through the instrument menu software and 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 which 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 only initiated manually by the operator. Performance checks are described in detail in the Vendor Operator's Manual, and the applicable information is planned to be contained in plant operating procedures.
Performance tests are planned to be performed periodically as recommended by the equipment vendor, for instance quarterly but no less often than the calibration interval of two years.
Channel functional tests per operations procedures with limits established in consideration of vendor equipment specifications are planned to be performed at appropriate frequencies established equivalent to or more frequently than existing spent fuel pool instrumentation.
Manual calibration tests are as described above in RAI-8a and b.
Manual calibration and operator performance checks are planned to be performed in a periodic scheduled fashion with additional maintenance on an as-needed basis when flagged by the system's automated diagnostic testing features.
Channel calibration tests per maintenance procedures with limits established in consideration of vendor equipment specifications are planned to be performed at frequencies established in consideration of vendor recommendations.
Response to RAI-8d:
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 NIST-traceable standards. Formal calibration check surveillance interval and timing would be established consistent with applicable guidance [Le.,
NEI 12-02 Section 4.3; on a refueling outage interval basis and within 60 days of a planned refueling outage]. Items such as system batteries are planned to be assessed under the Preventive Maintenance (PM) program for establishment of replacement frequency.
Surveillance/PM timing/performance are planned to be controlled via tasks in the PM program.
Attachment to GNRO-2013/00057 Page 15 of 21 3.9 Display The OIP states, in part, that The primary and backup instrument displays will be located in the Control Building as shown on Attach ments 1 and 2.
The display will be consistent with the guidelines of NRC JLD-ISG-2012-03 Revision 0 and NEI 12-02 Revision 1.
RAI-9
Please provide the following:
a) If both the primary and backup display locations are not located 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." Please include consideration of various drain-down scenarios.
Response to RAI-9a:
Both the primary and backup channel displays will be mounted in panels located in the Computer & Control Panel Room on the 148' elevation of the Control Building. The Control Building 148' elevation can be reached from the Main Control Room by descending one floor via Stair No. OC02 or Stair No. OC01. Once on the 148' elevation, the Computer & Control Panel Room can be accessed by traversing through doors OC408, OC405, or OC406.
A habitability evaluation is in progress. Information from the habitability evaluation will be included in a future six-month status report.
The FLEX staffing plan is in the process of being scheduled. The scheduled completion will be included in a future FLEX six-month status report.
If necessary, portable radios will be used to communicate with decision makers.
Response to RAI-9b:
The display panels are deemed promptly accessible due to the short distance between the Main Control Room and the location of the display panels. The panels are located one floor below the Main Control Room in the Control Building.
Attachment to GNRO-2013/00057 Page 16 of 21 4.0 PROGRAfvl FEATURES 4.2 Procedures The OIP states, in part, that Procedures for maintenance and testing will be developed using regulatory guidelines and vendor instructions.
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 to RAI-10a:
Vendor recommended inspection, maintenance, and repair procedures for the liquid level measurement system have been developed through the vendor's 30-year experience developing and manufacturing liquid level measurement and cable testing instrumentation.
These are for the most part specific to the system's proprietary electronics, subject to relevant industry standards for electronics fabrication and inspection and vendor's quality management system.
Where relevant, standards for naval shipboard liquid level indicating equipment have been used to develop procedures for operation, abnormal response, and administrative controls.
Portable instrumentation is not utilized. Both primary and backup SFPI channels incorporate permanent hard-wired installation.
The specific procedures to be used to capture the required activities described in this RAI response have not yet been developed but are planned to be developed in accordance with the vendor recommendations and Entergy processes and procedures.
Response to RAI-10b:
The specific procedures and their technical objectives to be used to capture the required activities described in the response to RAI 10a above have not yet been developed but are planned to be developed in accordance with the vendor recommendations and Entergy processes and procedures. These procedures will contain the technical objectives associated with the maintenance, inspection, testing, repair and utilization of the SFPI. Portable instrumentation is not utilized. Both primary and backup SFPI channels incorporate permanent hard-wired installation.
Attachment to GNRO-2013/00057 Page 17 of 21 4.3 Testing and Calibration The OIP did not provide any statement in this section.
RAI-11
Please provide the following:
a) A description of 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. Please 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.
Response to RAI-11a:
See RAI-7, 8, and 10 responses above for related descriptions of associated maintenance and testing program details. SFPI channel/equipment maintenance/preventative maintenance and testing program requirements to ensure design and system readiness are planned to be established in accordance with Entergy's 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 planned to be developed during the SFPI modification design process.
Response to RAI-11 b:
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 stocking of adequate spare parts reasonably diminishes the likelihood that a single channel (and greatly diminishes the likelihood that both channels) is (are) out-of-service for an extended period of time. Planned compensatory actions for unlikely extended out-of-service events are summarized as follows:
Attachment to GNRO-2013/00057 Page 18 of 21
- Compensatory Action Channel(s) if Required Restoration Required Restoration Action Out-of- Action not completed Service within Specified Time 1 Restore channel to Immediately initiate functional status within 90 action in accordance days (or if channel with Note below.
restoration not expected within 90 days, then proceed to Compensatory Action).
2 Initiate action within 24 Immediately initiate hours to restore one action in accordance channel to functional status, with Note below.
and restore one channel to functional status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.
Note: Present a report to the on-site safety review committee within the following 14 days. The report shall outline the planned alternate method of monitoring, the cause of the non-functionality, and the plans and schedule for restoring the instrumentation channel(s) to functional status.
Response to RAI-11 c:
The requested information is provided in the RAI-11 b response.
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