View source for DCL-13-073, Response to Request for Additional Information Regarding Overall Integrated Plan in Response to March 12, 2012, Commission Order to Modify Licenses with Regard to Reliable Spent Fuel Pool Instrumentation (Order No. EA-12-051)

{{Adams
| number = ML13200A123
| issue date = 07/18/2013
| title = Response to Request for Additional Information Regarding Overall Integrated Plan in Response to March 12, 2012, Commission Order to Modify Licenses with Regard to Reliable Spent Fuel Pool Instrumentation (Order No. EA-12-051)
| author name = Allen B
| author affiliation = Pacific Gas &amp; Electric Co
| addressee name = 
| addressee affiliation = NRC/NRR, NRC/Document Control Desk
| docket = 05000275, 05000323
| license number = DPR-080, DPR-082
| contact person = 
| case reference number = DCL-13-073
| document type = Letter type:DCL
| page count = 22
| project = 
| stage = Response to RAI
}}

=Text=
{{#Wiki_filter:Pacific Gas and Electric Company Barry S. Allen                Diablo Canyon Power Plant Site Vice President           Mail Code 104/6 P. O. Box 56 Avila Beach, CA 93424 805.545.4888 July 18, 2013                                                                                             Internal: 691.4888 Fax: 805.545.6445 PG&E Letter DCL-13-073 u.s. Nuclear Regulatory Commission                                                10 CFR 50.4 ATTN: Docu ment Control Desk 11555 Rockville Pike Rockville, MD 20852 Docket No. 50-275, OL-DPR-80 Docket No. 50-323, OL-DPR-82 Diablo Canyon Units 1 a,nd 2 Response to Request for Additional Information Regarding Overall Integrated Plan in Response to 1'v1arch 12. 2012. Commission Order to Modify Licenses with Regard to Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051)

==References:==
: 1. NRC Order Number EA-12-051, "Issuance of Order to Modify Licenses with Regard to Reliable Spent Fuel Pool Instrumentation," dated March 12, 2012
: 2. PG&E Letter DCL-12-028, "Pacific Gas and Electric Company's Ansvver to March 12, 2012, Commission Order Modifying License with Regard to Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051 )," dated March 28, 2012
: 3. PG&E Letter DCL-13-011 , "Pacific Gas and Electric Company's Overall Integrated Plan in Response to March 12, 2012, Commission Order to Modify Licenses with Regard to Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051)," dated February 27,2013
: 4. NRC Letter, "Diablo Canyon Power Plant, Unit Nos. 1 and 2 - Request for Additional Information Regarding Overall Integrated Plan for Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051) (TAC Nos. MF0963 and MF0964 )," dated July 3, 2013

==Dear Commissioners and Staff:==

On March 12, 2012, the Nuclear Regulatory Commission (NRC) issued Reference 1 to Pacific Gas and Electric Company (PG&E). Reference 1 is immediately effective and directs PG&E to have a reliable indication of the water level in the Diablo Canyon Units 1 and 2 spent fuel pools. Specific requirements are outlined in Reference 1, Attachment 2.
A member   of   the  STARS   (Strategic   Teaming   and  Resource     Srraring)     Alliance Callaway
* Comanche Peak
* Diablo Canyon  .. Palo Verde
* San Onofre .. South Texas Proj ect       0 Wol f Cree k

Document Control Desk                                                       PG&E Letter DCL-13-073 July 18, 2013 Page 2 Reference 1 requires submission of an initial status report 60 days following issuance of the final Interim Staff Gu idance and an Overall Integrated Plan by February 27,2013. PG&E provided those responses in Reference 2 and Reference 3, respectively.                                 I Reference 4 requests PG&E's response to eleven requests for additional information (RAls) by July 22, 2013. Enclosure 1 of this letter provides PG&E's response to the RAls.                                                      '
PG&E is making a regulatory commitment (as pefined by NEI 99-04) in Enclosure 2 of this letter. This letter contains no revisions t,o existing commitments.
If you have any questions, or require additional information, please contact Mr. Patrick Nugent at (805) 781-9786.
I declare under penalty of perjury that the foregoing is true and correct.
Executed on July 18, 2013.
Sincerely, B!::zle: 4tt-Site Vice President r
crlb/SAPN 50572316 Enclosures cc:           Diablo Distribution cc:/enc: Thomas R. Hipschman, NRC, Senior Resident Inspector Arthur T. Howell, III, NRC Region IV:
Eric J. Leeds, NRR Director James T. Polickoski, NRR Project Manager A  member  of   the  STARS   (Strategic  Teaming   and  Resource  Sharing)  Alliance Callaway
* Comanche Peak
* Diablo Canyon
* Palo Verde    San Onofre
* South Texas Project
* Wolf Creek

Enclosure 1 PG&E Letter DCL-13-073 Page 1 of 19 Pacific Gas and Electric Company Response to Nuclear Regulatory Commission Letter dated July 3, 2013~ "Diablo Canyon Power Plant, Unit Nos. 1 and 2 -
for Additional Information Regarding Overall Integrated              for Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051)
(TAC Nos. MF0963 and MF0964)
The OIP states, in part, that Key SFP water levels:
: 1)    Level adequate to support operation of the normal SFP cooling system: Indicated level on either the primary or backup instrument channel of 23 feet (ft)-9 inches (in.) above the top of the spent fuel storage racks, plus the accuracy of the SFP level instrument channel, which is to be determined. This aligns with the normal SFP level as described in the DCPP Updated Final Safety Analysis Report (UFSAR)
(Reference 5), Section 9.1.2.3.2, and provides adequate margin to maintain SFP cooling pump suction.
: 2)   Level adequate to provide substantial radiation shielding for a person standing on the SFP operating deck: Indicated level on either the primary or backup instrument channel of greater than 10ft above the top of the spent fuel storage racks, plus the accuracy of the SFP level instrument channel, which is to be determined. This monitoring level ensures there is an adequate water level to provide substantial radiation shielding for a person standing on the SFP operating deck.
: 3)    Level where fuel remains covered: Indicated level on either the primary or backup instrument channel of greater than 1 ft above the top of the spent fuel storage racks plus the accuracy of the SFP level instrument channel, which is to be determined. This monitoring level assures that there is adequate water level above the spent fuel seated in the rack.
Please provide the following:
a)    The specific elevations within the plant SFP corresponding to the three levels described in the guidance provided in NEI 12-02 Revision 1. 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

Enclosure 1 PG&E Letter DCL-13-073 Page 2 of 19 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 porlion 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.                               .
PG&E Response to RAI-1 a)  Level sensing equipment will measure level in the spent fuel pools (SFPs), with the same accuracy over the entire water level range of the SFP, from the normal pool operating level to the top of the spent fuel racks.
Level 1: Elevation 134 feet (ft) 5 inches (in.)
As discussed in Pacific Gas and Electric Company (PG&E) Letter DCL-13-011, dated February 27,2013, the normal operating level of the SFP is 137 ft 8 in.,
which is 23 ft 9 in. above the top of the fuel storage racks. PG&E conservatively designated this elevation as Level 1. PG&E has determined that operation of the SFP cooling system can be maintained down to the elevation of the SFP cooling system inlet pipe, assuming saturation conditions. PG&E is revising its definition of Level 1 to the level at which reliable suction loss occurs due to uncovering of the coolant inlet pipe, 134 ft 5 in. This is consistent with the guidance in NEI 12-02.
Level 2: Elevation 123 ft 11 in.
PG&E designates Level 2 as elevation 123 ft 11 in., which is 10 ft above the top of the fuel storage racks. This monitoring level ensures there is an adequate water level to provide substantial radiation shielding for a person standing on the SFP operating deck. This is consistent with the guidance in NEI 12-02.
Level 3: Elevation 114 ft 11 in.
PG&E designates Level 3 as elevation 114 ft 11 in., which is 1 ft above the top of the fuel storage racks. This is consistent with the "nominal" "highest point of any fuel rack ... " characterization of NEI 12-02. Level 3 is defined in this manner to provide the maximum range of information to operators, decision makers and emergency response personnel.
b)  See Figure 1.

Enclosure 1 PG&E Letter DCL-1 3-073 Page 3 of 19 c
1
                                      ! 11 ~ lL..-----.-D~l --                                     Operating Deck (EI. 140')
                                      +I   E        ::-c;.r-Top of Measurement Range (Value above nonnal will be established in detailed design phase)
I\              i
_._--J-----:L.---r- - - -I* --4
                                                     -   +--- Nonnal Level (EI. 137' - 8")
                                                     -   +--- LeveI1 (EI. 134' - 5")
Sensor Active     A Measurement Range
                                                      -+--  ;..-- Level 2 (EI. 123' _ 11 U)
Bottom of Measurement , /                            -+--   4--    Level 3 (EI. 114' - 11 ")
Range (Approximately 6" Below Level 3)
                           ~-4-------
                                 \
r---. t- -., TIll+----                             Top of Fuel Rack (EI. 113' - 11")
Dimension  Description                                       Responsibility A          Curb to Top of Rack {First Obstruction]           Utility / AE B          Curb to Maximum Water level                       Utility / AE C          Clearance Curb to FHM Bridge                      Utility / AE D          Curb Height above Operating Deck                  Utility / AE E          Coupler Face to Water (Minimum)                   Sensor Manufacturer F          Bracket Offset                                    Bracket Designer
                  ~
Figure 1: SFP Elevations (Units 1 and 2)

Enclosure 1 PG&E Letter DCL-13-073 Page 4 of 19 The OIP states, in pari, that The primary and backup instrument sensing components will be separated consistent with the guidelines of Reference 2 and Reference
: 3. Design of the mounting bracket will allow the fuel-handling machine to pass over the bracket without interference.
A SFP walkdown identified preliminary locations for the primary and backup level sensing components. As shown in Figure 1, the preliminary location of the primary and backup instrument sensing components for Unit 1 is at the south and norih ends of the Unit 1 SFP, respectively. As shown in Figure 1, the preliminary location of the primary and backup instrument sensing components for Unit 2 is at the norih and south ends of the Unit 2 SFP, respectively. The design for installation will include physical separation of the two sensors, separate extension cables from the electronics to the sensors, routing all cables in separate conduit/trays, separate UPS power supplied from different ac sources, and seismically-qualified mounting with physical separation of both the level sensing electronics and indications.
The final location of the primary and backup system mounting brackets will be determined during the design phase with consideration of power availability and separation requirements to protect against missiles.
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.

Enclosure 1 PG&E Letter DCL-13-073 Page 5 of 19 PG&E Response to RAI-2 Figure 2 shows an area bounding the planned location of the two permanently mounted le\lel probes within the SFP area. The specific locations of the probes will be provided in the 6-month update following completion of detailed design.
                                                  *137'- 3"1- - - - - - - --- --/
N
                                                                                  ~
10'-0" 1_-   *~~h"l~.., ...
* 1
       .\ ,
                                                         \46'-3"1 - - -- -- - -- - ---1 Figure 2: Unit 1 SFP dimensions and planned instrument layout. Unit 2 SFP dimensions are the same, layout is opposite-hand.

Enclosure 1 PG&E Letter DCL-13-073 Page 6 of 19 Figure 3 shows the planned cable routing to the instrument display locations in the control room and near the auxiliary board.
Pm  ary e or
                                              .
* 1 O' 1
                                           . . . . _-+-1-- Bonduit
                                                             ~
from Unit E ctronic Figure 3:

Enclosure 1 PG&E Letter DCL-13-073 Page 7 of 19 The OIP states, in part, that The mounting of both the primary and backup system will be installed to maintain its integrity during and following a design-basis seismic event. All locations will be reviewed for seismic interactions.
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. Please indicate in a schematic the portions of the level sensor that will serve as points of attachment for mechanical/mounting or electrical connections.
c)   A description of the manner by which the mechanical connections will attach the level instrument to permanent SFP structures so as to support the level sensor assembly.
PG&E Response to RAI-3 a)   The bracket for the sensing probe will be seismically designed to the design basis earthquakes in the Diablo Canyon Power Plant (DCPP) Updated Final Safety Analysis Report, Section 2.5.3.9, "Design and Licensing Basis Earthquakes." Loads that will be considered in the evaluation of the bracket and its mounting are: (1) static loads including the dead weight of the mounting bracket in addition to the weight of the level sensing instruments and cabling; and (2) dynamic loads including the seismic load due to excitation of the dead weight of the system in addition to the hydrodynamic effects (if credible considering the geometry and the flexibility of the sensing probe and the water sloshing height) resulting from the excitation of the SFP water.
A response spectra analysis will be performed for the seismic evaluation of the mounting bracket using a finite element analysis software and using the floor response spectrum at the 140-ft elevation in the fuel handling building (Le.
mounting floor elevation). The material properties that will be used for the bracket and its mounting will take into consideration the environmental

Enclosure 1 PG&E Letter DCL-13-073 Page 8 of 19 conditions in the SFP area following a seismic event. Hydrodynamic effects on the mounting bracket will be evaluated using TID-7024, "Nuclear Reactors and Earthquakes," dated 1963. Plant acceptance criteria and applicable codes will be used for the design of the bracket and its anchorage.
b)   Figure 4 shows a top view of the pedestal (stainless steel tube welded to the base plate and the channel shown in the figure) that will attach to the pool deck.
The pedestal will be attached to the pool deck using installed anchors that will be designed according to the existing plant specifications for design of concrete anchors. The pedestal will be adjusted to the height of the deck curb to ensure the bracket extends over the pool horizontally level. Final dimensions of the pedestal and bracket will be provided in the 6-month update following completion of detailed design.
Pedestal I            I
                          -0              ~ I             I
                  ~          0         0 0
l I
I--t.
                        ~
1  Bracket    1&deg;              ~
                                                                          ~)
0 0 0      1
                                                                         '="'"
0                           I---"
0-
                                          -   I           t
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f/7 SFP Deck 1              1                                                         SFP 1 Deck Curb 1 /                      1          1 Figure 4: Top View of SFP Instrumentation pedestal and bracket.
The probe attaches to the bracket via a 1-1/2 inch national pipe thread threaded connection. Figure 5 details the vertical portion of the bracket where the probe will thread into the bracket. All non-movable connections of parts will be welded during manufacturing. Units 1 and 2 have similar configurations and components will have similar arrangements. Final dimensions of the bracket will be provided in the 6-month update following completion of detailed design.

Enclosure 1 PG&E Letter DCL-13-073 Page 9 of 19
                                          ..Q.
1        I   --,
Ll 0        0                         Ip =-
o 0 0        0 o   0      ~
                                                                                  ~-
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                                                           '"' I        L_
Top View of Pedestal and Bracket I                                                              I Horizonta l section of bracket; attaches to pedesta l or directly L---'--iwe lded con nection to ancho rs Vertica l dimension TSD based on norma l/high water level and bridge interference Threaded 1 1/2" NPT half coupling; Probe coupler between Side View of Probe Bracket                                                          interconnecting cable and probe w ire will fully engage thread into location Iwelded lconnections
                                                ,--.--I Figure 5: SFP Instrumentation System Bracket Mounting Details.

Enclosure 1 PG&E Letter DCL-13-073 Page 10 of 19 c)     The attachment of the seismically-qualified bracket and pedestal to the pool deck will be through anchors that will be designed according to existing plant specifications for design of concrete anchors.
The OIP states, in pari, that Reliability of both instrument channels will be demonstrated via an appropriate combination of design, analyses, operating experience, and/or testing of channel components for the following sets of parameters:
(1)   conditions in the area of instrument channel component used for all instrument components; (2)   effects of shock and vibration on instrument channel components used during and following any applicable event for installed components; and (3)   seismic effects on instrument channel components used during and following a potential seismic event for only installed components.
The instrument channel reliability will be demonstrated by an appropriate combination of design, analyses, operating experience, and/or testing of channel components for the effects of shock and vibration. Demonstration of shock and vibration adequacy will be consistent with the guidelines in Reference 2 and Reference 3.
Please provide the following:
a)     A description of the specific method or combination of methods you intend to apply to demonstrate the reliability of the permanently installed equipment under Beyond-Design-Basis (BOB) ambient temperature, humidity, shock, vibration, and radiation conditions.
b)     A description of the testing and/or analyses that will be conducted to provide assurance that the equipment will perform reliably under the worst-case credible design basis loading at the location where the equipment will be mounted. Include a discussion of this seismic reliability demonstration as it applies to 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.

Enclosure 1 PG&E Letter DCL-13-073 Page 11 of 19 PG&E Response to RAI-4 a)   Demonstration of the reliability of the permanently installed SFP instrumentation system equipment under the beyond-design-basis (BOB) conditions will be by design, analysis, operating experience and testing by the system vendor and the equipment manufacturer(s), as described below for each of the identified conditions.
Temperature and Humidity SFP instrumentation system materials and components located in the vicinity of the SFP will be selected and specified by design to meet or exceed the temperature and humidity requirements of 212&deg;F and 100 percent humidity.
Sensor and system electronics in other locations will be selected and specified by design to meet or exceed the design basis conditions for those locations.
Design will be supplemented by system component tests as shown below.
System Component                           Basis for Demonstration Sensor Probe               By design. Stainless steel cable probe is inherently tolerant of the effects of the specified temperature and humidity.
Sensor Bracket             By design and analysis. Stainless steel bracket is inherently tolerant of the effects of the specified temperature and humidity.
Sensor Coupler             By design. The coupler is primarily stainless steel, and is specifically designed by the manufacturer for high temperature and humidity applications.
Coaxial Cable              By design and testing. Selected by design for conditions; tested for performance at 212&deg;F, saturated steam.
Sensor Electronics         By design. Sensor electronics design temperature exceeds requirements for the sensor electronics mounting locations.
System Electronics and By design and testing. Component design temperature Display                    exceeds requirements for equipment mounting locations; tested for performance under conditions of temperature and humidity cycling.
Shock and Vibration All SFP instrumentation system components located within the SFP will be passive components, inherently resistant to shock and vibration loadings.
These include the stainless steel sensor cable probe, sensor bracket, coupler and interconnecting cable.

Enclosure 1 PG&E Letter OCL-13-073 Page 12 of 19 Active electronic components, located outside the SFP area will be permanently and rigidly attached to seismic racks or structural walls and are not subject to shock and vibration loadings. However, assurance of reliability under conditions of shock and vibration will be supported by manufacturer operating experience, which will include use of components in high vibration installations, such as compressed air systems and tran~portation industries.
Radiation Components subject to significant radiation under BOB conditions will be those in the SFP area. These include the sensor probe, bracket, coupler and interconnecting cable. The sensor probe and bracket will be stainless steel and will not be affected by the anticipated radiation. The coupler and interconnecting cable will be selected by design for the BOB radiation service.
Supplemental radiation testing of the interconnecting cable will be completed to demonstrate operation for more than 1 week with SFP water at Level 3.
b) The sensor cable probe and supporting bracket are functionally passive components. Analysis will be used to demonstrate they will maintain their structural integrity and design configuration and to establish their reliability.
The coupler and interconnecting cable are also passive components; however, they will be included in the seismic testing of the sensor electronics. All active system components, including sensor electronics, system electronics, batteries, display and enclosures will be seismically tested based on rigid mounting conditions. Testing will be tri-axial, using random multi-frequency inputs, in accordance with IEEE 344-2004. Analyses and testing will envelope the conditions at equipment mounting locations resulting from the design basis maximum ground motion.
c) All components except for the stainless steel sensor cable probe and the stainless steel bracket will be seismically tested in a rigidly-mounted condition equivalent to their as-installed condition. The cable probe and bracket are passive components for which maintenance of structural or physical integrity is the only requirement. The active components of the SFP instrumentation system will be functionally tested before and after seismic simulation to assure that the components will remain functional following a seismic event. Water level inputs to the system will be simulated by grounding the system probe at selected, repeatable positions. Comparison of system output will be made both to pre-test results and to the measured position of the cable probe input.

Enclosure 1 PG&E Letter DCL-13-073 Page 13 of 19 The OIP states, in part, that The backup instrument system will be redundant to and independent of the primary instrument system. Independence of the two systems includes location, mounting, power sources, power and signal wiring, and indications, to prevent any failure of one system from affecting the other system.
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.
PG&E Response to RAI-5 a)   Within the SFP area, the brackets will be mounted on the South (primary sensor) and North (back-up sensor) sides of the pool for Unit 1 and the North (primary sensor) and South (back-up sensor) sides of the pool for Unit 2, as permanent plant structures allow. Placing the brackets and probes on opposite sides allows for natural protection from a single event or missile from disabling both systems. The cabling within the SFP area will be routed in separate hard-pipe conduit. All conduit routing and location of system components will be designed such that there will be no adverse seismic interactions.
b)   Each system will be installed using completely independent cabling structures, including routing of the interconnecting cable within the SFP area in separate hard-pipe conduits. Power sources will be routed to the electronics enclosures from electrically separated sources ensuring the loss of one train or bus will not disable both channels. The system displays will be installed in separate qualified National Electrical Manufacturers Association 4X or better enclosures, with the primary and back-up display in the control room. Primary and backup systems will be completely independent of each other, having no shared components.

Enclosure 1 PG&E Letter DCL-13-073 Page 14 of 19 The alP states, in part, that An ac [AC, alternating current] source will be selected for each system's 24-Vdc [volts, DC, direct current] UPS [uninterruptible power supply],
with power cables routed separately through existing or new tray/conduit and penetrations.
Both channels will be powered by independent batteries following a loss-of-ac power. The minimum battery life will be 72 hours. The 72-hour battery life is a sufficient amount of time for an alternate source of power to be provided by the plant-specific procedures to address Reference 7. Each channel will include an externally accessible bulkhead connector and transfer switch for connection of an alternate power source.
Please provide the following:
a)   A description of the electrical A C power sources and capacities for the primary and backup channels.
b)   If the level measurement channels are to be powered through a battery system (either directly or through an 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 BOB event for the minimum duration needed, consistent with the plant mitigation strategies for BOB external events (Order EA-12-049).
PG&E Response to RAI-6 a)   Under normal operating conditions, the primary and backup channels will each be powered by a different, single, nonvital bus, 120 volt (V), 60 hertz feed. Current draw for each of the primary and backup channels will be a maximum of 5 amperes (A). There will be a 6 A, 2-pole, 240-V alternating current (ac) circuit breaker installed in each of the enclosures.
b)   Battery sizing will be in accordance with standard IEEE 485-2010. Design criterion applied is continuous system operation for 72 hours following loss of ac power. Calculation of system power consumption will be based on the specified values listed in component manufacturer specifications. A 10 percent capacity margin will be added to battery sizing calculations, following guidelines of IEEE 485-2010, Section 6.2.2. The 72-hour operating design basis is conservative, in that it exceeds the expected time for restoration of FLEX ac power.

Enclosure 1 PG&E Letter OCL-13-073 Page 15 of 19

===RAI-7===
The OIP states, in part, that Instrument channels will be designed such that they will maintain their specified accuracy without recalibration following a power interruption or change in power source. The accuracy will be within the resolution requirements of Reference 2, Figure 1.
The instrument accuracy will be sufficient to allow personnel using plant procedures to determine when the water level reaches levels 1, 2, and 3 without conflicting or ambiguous indication.
Please provide the following:
a)   An estimate of the expected instrument channel accuracy performance (e.g., in percentage of span) under both i) normal SFP level conditions (approximately Level 1 or higher) and ii) at the BOB conditions (i.e., radiation, temperature, humidity, post-seismic and post-shock conditions) that would be present if the SFP level were at the Level 2 and Level 3 datum points.
b)   A description of the methodology that will be used for determining the maximum allowed deviation from the instrument channel design accuracy that will be employed under normal operating conditions as an acceptance criterion for a calibration procedure to flag to operators and technicians that the channel requires adjustment to within the normal condition design accuracy.
PG&E Response to RAI-7 a)   The instrument channel accuracy will be established during the design verification phase. An estimate of the expected instrument channel accuracy under normal and BOB conditions will be provided in the 6-month update following completion of detailed design.
b)   The calibration procedure, and the methodology and basis for establishing both the criteria indicating the need for recalibration, and the acceptance criterion to be used with the procedure, will be established during the design verification phase. The methodology for defining these criteria will be provided in the 6-month update following completion of detailed design.

Enclosure 1 PG&E Letter DCL-13-073 Page 16 of 19 The OIP states, in part, that Instrument channel design will provide for routine testing and calibration consistent with Reference 2 and Reference 3.
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.
PG&E Response to RAI-8 a)   Details of the capabilities and provisions of the level instrumentation for periodic calibration and testing will be established during the detailed design phase. A description of these features and the way they will support in-situ testing will be provided in the 6-month update following completion of detailed design.
b)   A description of how the instrument channel design provides for routine in-situ testing and calibration will be provided in the 6-month update following completion of detailed design.
c)   Details of functional checks and instrument channel calibrations will be determined during the detailed design phase. A description of how functional checks and calibration tests will be performed, and the frequency at which they will be conducted, will be provided in the 6-month update following completion of detailed design. An explanation of how these surveillances will be incorporated into the plant surveillance program will be included.

Enclosure 1 PG&E Letter DCL-13-073 Page 17 of 19 d)   The preventative maintenance tasks required to be performed during normal operation, and the planned surveillance intervals will be determined during the detailed design phase. A description of these tasks and intervals will be provided in the 6-month update following completion of detailed design.
The OIP states, in part, that The primary system indicator will be located in the vicinity of the control room.
The backup system indicator will be located in an accessible location. The locations will allow for reading of the indicators following an event. The display will provide continuous indication of the SFP water level and will be consistent with the guidelines of Reference 2 and Reference 3.
Please provide the following:
a)   The specific location for the primary and backup instrument channel displays.
b)   Since both primary and backup display locations are not in the main control room, please provide justification for prompt accessibility to displays including primary and alternate route evaluation, habitability at display location(s),
continual resource availability for personnel responsible to promptly read displays, and provisions for communications with decision makers for the various SFP drain down scenarios and external events.
c)   The reasons justifying why the locations selected enable the information from these instruments to be considered "promptly accessible." Include consideration of various drain-down scenarios.
PG&E Response to RAI-9 a)   The primary instrument channel display for each Unit will be located in the main control room. The alternate channel instrument display for each Unit will be located on the 85-ft elevation in the auxiliary building, near the auxiliary board control room.
b)   The alternate instrument display, located near the auxiliary board control room on the 85-ft elevation in the auxiliary building, will be promptly accessible from the control room via stairway and hallway since this area is in a seismic structure. This location would be habitable during an extended loss of ac power event. Communications from this location will be made via portable radios.
c)   The primary instrument displays in the control room are promptly accessible since the control room is continuously manned and will be accessible following

Enclosure 1 PG&E Letter DCL-13-073 Page 18 of 19 a beyond-design-basis external event (BDBEE). The alternate instrument displays near the auxiliary board control room are promptly accessible following a BDBEE via stairway and hallway since this area is in a seismic structure.

===RAI-10===
The OIP states, in part, that:
Procedures will be developed using guidelines and vendor instructions to address the maintenance, operation, and abnormal response issues associated with the new SFP instrumentation.
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.
PG&E Response to RAI-10 a)   As stated in PG&E Letter DCL-13-011, dated February 27, 2013, site procedures will be developed using guidance in NEI 12-02 to address the maintenance, operation, and abnormal response issues associated with the new SFP instrumentation.
These procedures will meet the guidance described in NEI 12-02, Revision 1, Section 4.2, Procedures, and Section 4.3, Testing and Calibration, and will be developed in accordance with the DCPP procedure control process. A list of the operating (both normal and abnormal response) procedures, calibration/test procedures, maintenance procedures, and inspection procedures will be provided in the 6-month update following completion of detailed design.
b)   PG&E's design for SFP instrumentation does not use portable SFP monitoring components. Specific technical objectives to be achieved by procedures will be to maintain the instrument channel functionality, to maintain the instrument channels at the design accuracy, and to ensure compensatory actions are taken as required by NEI 12-02.

Enclosure 1 PG&E Letter DCL-13-073 Page 19 of 19

===RAI-11===
The DIP states, in part, that Processes will be established and maintained for scheduling and implementing necessary testing and calibration of the primary and backup SFP 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.
Please provide the following:
a)   Further information describing the maintenance and testing program the licensee will establish and implement to ensure that regular testing and calibration is performed and verified by inspection and audit to demonstrate conformance with design and system readiness requirements. Include a description of your plans for ensuring that necessary channel checks, functional tests, periodic calibration, and maintenance will be conducted for the level measurement system and its supporting equipment.
b)   Describe how the guidance in NE112-02 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.
PG&E Response to RAI-11 a)   PG&E will provide a description of the maintenance and testing program, and a description of the 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. The descriptions will be provided in the 6-month update following completion of detailed design.
b)   PG&E will implement measures to minimize the possibility of either the primary or backup channel being out of service for an extended period. Sufficient spares, components, and materials will be maintained to be able to repair or replace defective components in a short time. Descriptions of these measures will be provided in the 6-month update following completion of detailed design.
c)   PG&E will follow the NEI 12-02 guidance with regard to time during which one or more channels may be out of service, including compensatory actions. A description of the compensatory actions will be provided in the 6-month update following completion of detailed design.

Enclosure 2 PG&E Letter DCL-13-073 Regulatory Commitments PG&E is making the following regulatory commitment (as defined by NEI 99-04) in this submittal:
Commitment                                    Due Date A status update of the spent fuel pool     6-month intervals following submittal of the instrumentation will be included in the    overall integrated plan.
6-month status reports prepared pursuant to NRC Order EA-12-051, Section IV.C.2.}}