ML13213A015

Millstone Power Station, Units 2 and 3, Response to Request for Additional Information to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Reliable Spent Fuel Pool Instrumentation (Order Number EA-12-051)

ML13213A015
Person / Time
Site:	Millstone
Issue date:	07/26/2013
From:	Stoddard D G Dominion Nuclear Connecticut, Dominion
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
EA-12-051
Download: ML13213A015 (24)

Text

~Dominioni Dominion Nuclear Connecticut, Inc.51000 Dominion Boulevard, Glen Allen, VA 23060Web Address:

www.dom.comn July 26, 201310 CFR 2.202EA-12-051 Attention:

Document Control DeskU.S. Nuclear Regulatory Commission Washington, D.C. 20555-0001 Serial No.:NL&OS/ETS:

Docket Nos.:License Nos.:13-385R350-336/423 DPR-65NPF-49DOMINION NUCLEAR CONNECTICUT, INC.MILLSTONE POWER STATION UNITS 2 AND 3MARCH 12, 2012 COMMISSION ORDER MODIFYING LICENSES WITH REGARD TOREQUIREMENTS FOR RELIABLE SPENT FUEL POOL INSTRUMENTATION (ORDER NUMBER EA-12-051)

RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION (RAI)

References:

1. NRC Order Number EA-12-051, Order Modifying Licenses with Regard toRequirements for Reliable Spent Fuel Pool Instrumentation, dated March 12,2012 (ML12073A202)

2. NRC Interim Staff Guidance JLD-ISG-2012-03, EA-12-051, Order Modifying Licenses with Regard toSpent Fuel Pool Instrumentation, Revision 0,(ML12221A339)

Compliance with OrderRequirements for Reliabledated August 29, 2012On March 12, 2012, the Nuclear Regulatory Commission (NRC) issuedOrder EA-12-051 (Reference

1) to Dominion Nuclear Connecticut, Inc. (DNC). DNCresponded to the Order by letter dated March 26, 2012 (Serial No.12-165) and providedan Initial Status Report on October 25, 2012 (Serial No. 12-165A),

consistent withReference

2. DNC also submitted an Overall Integrated Plan, as required by SectionIV, Condition C.l.a of the Order, in a letter dated February 28, 2013 (Serial No. 12-165B).The NRC issued an RAI to DNC on June 26, 2013. DNC's response to the RAI isprovided in the attachment to this letter.

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Page 2 of 3If you have any questions, please contact Margaret A. Earle at (804) 273-2768.

Sincerely, Daniel G. StoddardSenior Vice President

-Nuclear Operations Attachment Response to Request for Additional Information

-Reliable Spent Fuel PoolInstrumentation Commitments made in this letter: NoneCOMMONWEALTH OF VIRGINIA

))COUNTY OF HENRICO )The foregoing document was acknowledged before me today, in and for the County andCommonwealth aforesaid, by Daniel G. Stoddard who is Senior Vice President

-Nuclear Operations for Dominion Nuclear Connecticut, Inc. He has affirmed before methat he is duly authorized to execute and file the foregoing document in behalf of theCompany, and that the statements in the document are true to the best of hisknowledge and belief.Acknowledged before me this a2tfAday of J7 / ,2013.My Commission Expires:

jVQCOz 1r 31, ,1o/,/Notary PublicCommonwealth of VirginiaReg. # 7518653My Commission Expires December 31, N- e Notary 0006(SEAL)

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Page 3 of 3cc: Director of Office of Nuclear Reactor Regulation U. S. Nuclear Regulatory Commission One White Flint NorthMail Stop 13H16M11555 Rockville PikeRockville, MD 20852-2738 U. S. Nuclear Regulatory Commission, Region IRegional Administrator 2100 Renaissance Blvd.Suite 100King of Prussia, PA 19406-2713 David H. JaffeU. S. Nuclear Regulatory Commission Two White Flint NorthMail Stop T6 D2311545 Rockville PikeRockville, MD 20852-2738 James S. KimNRC Project Manager Millstone Units 2 and 3U. S. Nuclear Regulatory Commission One White Flint NorthMail Stop 08 C 2A11555 Rockville PikeRockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power Station Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos.: 50-336/423 ATTACHMENT Response to Request for Additional Information Reliable Spent Fuel Pool Instrumentation Millstone Power Station Units 2 & 3Dominion Nuclear Connecticut, Inc. (DNC)

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 1 of 20Response to Request for Additional Information Reliable Spent Fuel Pool Instrumentation

Background

By letter dated February 28, 2013 (Agencywide Documents Access and Management System (ADAMS) Accession No, ML13063A012),

Dominion Nuclear Connecticut, Inc.,(DNC) submitted an Overall Integrated Plan (OIP) in response to the March 12, 2012,U.S. Nuclear Regulatory Commission (NRC), Commission Order modifying licenseswith regard to requirements for Reliable Spent Fuel Pool (SFP) Instrumentation (OrderNumber EA-12-051; ADAMS Accession No. ML12054A679) for Millstone Power StationUnits 2 and 3. The NRC staff endorsed Nuclear Energy Institute (NEI) 12-02, "Industry Guidance for Compliance with NRC Order EA-12-051, to Modify Licenses with Regardto Reliable Spent Fuel Pool Instrumentation,"

Revision 1, dated August 2012 (ADAMSAccession No. ML12240A307),

with exceptions as documented in Interim StaffGuidance (ISG) 2012-03, "Compliance with Order EA-12-051, Reliable SFPInstrumentation,"

Revision 0, dated August 29, 2012 (ADAMS Accession No.ML12221A339).

The NRC staff has reviewed the February 28, 2013, response by the licensee anddetermined that the following Request for Additional Information (RAI) is needed tocomplete its Technical Review. If any part of this information is not available within 30days of this request, please provide the date this information will be submitted.

NRC RAI No.1The OIP states, in part, thata) Level 1 -This is indicated level on either the primary or back-upinstrument channel of greater than approximate elevation 36'-0" plusthe accuracy of the SFP level instrument

channel, which is to bedetermined.

This level is based on the elevation at which the top of theupper SFP cooling pump suction line penetrates the pool wall(Reference 4, Section 9.5.2.1).

b) Level 2 -This is indicated level on either the primary or back-upinstrument channel of greater than approximate elevation 22'-5" plusthe accuracy of the SFP level instrument

channel, which is to bedetermined.

This elevation is sufficient depth to provide radiation shielding for personnel to respond to Beyond-Design-Basis ExternalEvents and to initiate SFP makeup strategies.

c) Level 3 -This is indicated level on either the primary or back-upinstrument channel of greater than approximate elevation 12'-5" plus Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 2 of 20the accuracy of the SFP level instrument

channel, which is to bedetermined.

This monitoring level assures that the fuel remainscovered.Please provide the following:

a) The specific functional reasons for identification of the elevations withinthe SFP as levels 1, 2 and 3. For level 1, specify how the identified location represents the HIGHER of the two points described in the NEI12-02 guidance for this level.b) A clearly labeled sketch depicting the elevation view of the proposedtypical mounting arrangement for the portions of instrument channelconsisting of permanent measurement channel equipment (e.g., fixedlevel sensors and/or stilling wells, and mounting brackets).

Indicate onthis sketch the datum values representing Level 1, Level 2, and Level 3as well as the top of the fuel. Indicate on this sketch the portion of thelevel sensor measurement range that is sensitive to measurement ofthe fuel pool level, with respect to the Level 1, Level 2, and Level 3datum points.DNC Response:

(MPS2)a) The Level 2 OIP response for Millstone Power Station Unit 2 (MPS2) above isquoted in part. For completeness, the OIP Level 2 statement reads in itsentirety as follows:"Level 2 -This is indicated level on either the primary or back-upinstrument channel of greater than approximate elevation 22'-5" plus theaccuracy of the SFP level instrument

channel, which is to be determined.

This elevation is approximately 10' above the top of the fuel racks andensures a minimum level of 10' above the top of the fuel (Reference 4).This water level ensures there is sufficient depth to provide radiation shielding for personnel to respond to Beyond Design-Basis ExternalEvents and to initiate SFP makeup strategies."

As stated in the OIP, the specific functional reasons for identification of theelevations within the SFP as Levels 2 and 3 are: Level 2, elevation ofsufficient depth to provide radiation shielding for personnel to respond to BDBevents and initiate makeup strategies; and Level 3, elevation at which fuel isstill covered.

Level 1 is the elevation at which the top of the upper SFPcooling pump suction line penetrates the pool wall.A calculation is being performed to verify that adequate water level isavailable to support net positive suction head (NPSH). Results of the Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 3 of 20calculation, including justification for the Level 1 value specified in the OIP,will be provided in the February 2014 six month status update.b) The table below provides an elevation view of the MPS2 SFP showing theproposed Level 1, 2, and 3 values and elevations of the fuel racks and coolingsystem. The final determination of Level 3 will take into account the weightlocated on the bottom end of the probe (refer to RAI Response 3b). The finalmounting arrangement (e.g., fixed level sensors and mounting brackets) willbe available upon completion of the final design, scheduled for December2013, and will be forwarded to the NRC during the subsequent scheduled status update.

Serial No. 13-385RAI Response

-Order EA-1 2-051Docket Nos. 50-336/423 Attachment Page 4 of 20MPS2 SFP Elevations AbsoluteLocation Elevation aboveMSL (ft.)Top of SFP Wall 38.5Top of Instrument Span 37.0Nominal Level 36.5LEVEL 1* -Top of Cooling Suction Inlet 35.8PipeInstrument SpanLEVEL 2 22.5 24.5 feet.Top of Fuel Racks + 10 feet 22.5LEVEL 3- Bottom of Instrument Span 12.5 tLEVE -B tt , ,; ... r,, : ' '10 ft.Top of Fuel Racks 12.5 _Bottom of Pool -2.014.5 ft.Centerline of cooling pumps -3.3* Required level to provide adequate NPSH at saturated conditions will be verifiedby formal calculation and results provided in the February 2014 six month statusupdate.

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 5 of 20DNC Response:

(MPS3)Per email from James Kim (NRC) dated June 24, 2013, RAI-1 for Millstone PowerStation Unit 3 (MPS3) is similar to the Unit 2 RAI-1. The background information provided with RAI-1 addressed only the Unit 2 elevations;

however, the corresponding MPS3 elevations are used in this response.

a) The Level 2 QIP response for Unit 2 above is quoted in part. The complete Level 2OIP response is provided below with the only difference being that the Unit 3, Level2 OIP details are indicated in parenthesis:,

"Level 2 -This is indicated level on either the primary or back-up instrument channel of greater than approximate elevation 22'-5" (35'-4")

plus the accuracy ofthe SFP level instrument

channel, which is to be determined.

This elevation isapproximately 10' above the top of the fuel racks and ensures a minimum level of10' above the top of the fuel (Reference 4). This water level ensures there issufficient depth to provide radiation shielding for personnel to respond to BeyondDesign-Basis External Events and to initiate SFP makeup strategies."

As stated in the OIP, the specific functional reasons for identification of the elevations within the SFP as Levels 2 and 3 are: Level 2, elevation of sufficient depth to provideradiation shielding for personnel to respond to BDB events and initiate makeupstrategies; and Level 3, elevation at which fuel is still covered.

Level 1 is the elevation at which the top of the upper SFP cooling pump suction line penetrates the pool wall.A calculation is being performed to verify that adequate water level is available tosupport net positive suction head (NPSH). Results of the calculation, including justification for the Level 1 value specified in the OIP, will be provided in the February2014 six month status update.b) The table below provides an elevation view of the MPS3 SFP showing the proposedLevel 1, 2, and 3 values and elevations of the fuel racks and cooling system. Thefinal determination of Level 3 will take into account the weight located on the bottomend of the probe (refer to RAI Response 3b). The final mounting arrangement (e.g.,fixed level sensors and mounting brackets) will be available upon completion of thefinal design, scheduled for December 2013, and will be forwarded to the NRC duringthe subsequent scheduled status update.

Serial No. 13-385RAI Response

-Order EA-1 2-051Docket Nos. 50-336/423 Attachment Page 6 of 20MPS3 SFP Elevations AbsoluteElevation Locationabv aboveMSL (ft.)Top of SFP Wall 52.3Top of Instrument Span 50.3Nominal Level 49.8LEVEL I" -Top of Cooling Suction Inlet 46.8Pipe Instrument SpanLEVEL 2 35.3 25.0 feet.Top of Fuel Racks + 10 feet 35.1Centerline of cooling pumps 26.6lOft.LEVEL 3 -Bottom of Instrument Span 25.3Top of Fuel Racks 25.113.8 ft.Bottom of Pool 11.3 ....* Required level to provide adequate NPSH at saturated conditions will be verifiedby formal calculation and results provided in the February 2014 six month statusupdate.

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 7 of 20NRC RAI No. 2The OIP states, in part, thatThe MPS2 SFP Primary and Back-up instrument channels will use Guided WaveRadar (GWR) based level measurement technology.

GWR level measurement instruments work based on the Time Domain Reflectometry (TDR) principal.

Thedevice transmits low-intensity electromagnetic pulses along a rigid or flexibleconductor where pulses move at the speed of light. When the pulses reach thesurface of the medium to be measured, a portion of the signal is reflected back tothe electronics.

The instrument measures the time from when the pulse istransmitted to when it is received; half of the measured time will be equivalent tothe distance from the reference point of the device to the surface of the measuredprocess.

The time value will be representative of the measured level andconverted for use in displaying level information.

Attributes of a GWR/TDR system include:* A sensor probe that is submerged in the process medium.* Device performance that is not affected by dust, foam, agitated

surfaces, boiling surfaces, changes in pressure, changes in temperature, changesin dielectric

constant, or changes in density.* The requirement to locate sensitive electronic equipment outside of the SFParea.* Low power consumption.

• No mechanical moving parts which simplifies the installation andreduces maintenance.

• The ability to detect level with accuracy that meets the requirements of NEI12-02.The primary and back-up channels will use a fixed instrument providing continuous level measurement over the entire range. The measured range will befrom approximately elevation 37'-0" to elevation 12'-5" -for a total indicated rangeof approximately 24'-7" (295 inches).

SFP level is verified daily in accordance with existing procedures.

Primary instrument channel level sensing components will be located on the eastwall of the SFP. Back-up instrument channel level sensing components will belocated in the northwest corner of the SFP.Please provide a clearly labeled sketch or marked-up plant drawing of the plan view ofthe SFP area, depicting the SFP inside dimensions, the planned locations/

placement ofthe primary and back-up SFP level sensor, and the proposed routing of the cables thatwill extend from the sensors toward the location of the read-out/display device.

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 8 of 20DNC Response:

(MPS2 and MPS3)The final locations for the level sensors, electronics and display units have not yet beendetermined.

As discussed in the response to RAI No. 5, the conceptual design placesthe sensors in the Fuel Building, and the transmitters in the Auxiliary Building.

Per theresponse to RAI No. 9, the location of the read-out/displays are in the Auxiliary Buildingfor both MPS2 and MPS3.The final system component locations will be available upon completion of the finaldesign, scheduled for December 2013, and will be forwarded to the NRC during thesubsequent scheduled status update.NRC RAI No. 3The OIP states, in part, thatBoth the primary and backup systems will be installed as Seismic Category I tomeet the NRC ISG JLD-ISG-2012-03 and NEI 12-02 guidance requirements.

Please provide the following:

a) The design criteria that will be used to estimate the total loading on themounting device(s),

including static weight loads and dynamic loads. Describethe methodology that will be used to estimate the total loading, inclusive ofdesign basis maximum seismic loads and the hydrodynamic loads that couldresult from pool sloshing or other effects that could accompany such seismicforces.b) A description of the manner in which the level sensor (and stilling well, ifappropriate) will be attached to the refueling floor and/or other supportstructures for each planned point of attachment of the probe assembly.

Indicate in a schematic the portions of the level sensor that will serve as pointsof attachment for mechanical/mounting or electrical connections.

c) A description of the manner by which the mechanical connections will attachthe level instrument to permanent SFP structures so as to support the levelsensor assembly.

DNC Response:

(MPS2 and MPS3)a) The design criteria to be used to estimate the total loading on the mounting devicesis an item to be supplied by the vendor per the DNC procurement specification.

Thevendor has provided the following:

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 9 of 20"The flexible probe will have excursions that will result in some impacts to theliner. However, the flexible nature of the probe results in a self-relaxing responseto static and hydrodynamic loading that will dramatically limit the inertia andenergy that the probe can impart to the liner."Further details of the hydrodynamic/seismic evaluation will be provided by thevendor in accordance with the final procurement specification.

The full qualification will be available upon completion of the final design, scheduled for December 2013,and will be forwarded to the NRC during the subsequent scheduled status update.b) Because of the lightweight and flexible design of the Guided Wave Radar (GWR)probe, a stilling well is not required.

The lack of probe mass and the probe'sreaction to seismic loading permit the pool mount to be very simple, lightweight, andrequire little space for atta6hment.

It can be attached on the curb's horizontal surface or curb face in most pool situations.

Attachment on the curb face results inthe cable conduit from the mount to the transmitter enclosure being the onlyprotrusion above the curb. The transmitter enclosures will be located in the Auxiliary Building.

The space used on the SFP deck and over the pool is minimal.

Weight is minimal,and recognizing the self-damping characteristics of the flexible probe, seismic issuesare easily manageable conditions.

The probe is comprised of a flexible stainless steel cable secured at the top by a connector and flange. The bottom of the probehas a uniquely designed weight. The probe is designed to hang in close proximity tothe liner without touching it. During an event, preliminary analysis shows that theprobe will contact the liner, but the weight of the probe, the bumper material, theself-relaxing characteristics of the cable and the dampening effects of the poolinventory result in very little energy being imparted to the pool liner. Therefore, thereare no points of attachment on the SFP liner.The final mounting details will be available upon completion of the final design,scheduled for December 2013, and will be forwarded to the NRC during thesubsequent scheduled status update.c) As discussed above, the flexible GWR probe will be mounted either on the SFP curbhorizontal surface or the curb face. Because of the design, no attachment to thepool liner is required.

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 10 of 20NRC RAI No. 4The OIP states, in part, thatInstrument channel reliability will be demonstrated via a combination of design,analyses, operating experience, and/or testing of channel components for thefollowing sets of parameters:

" Conditions in the area of instrument channel components,

• Effects of shock and vibration on the instrument channel components, and" Seismic effects on instrument channel components used during andfollowing a potential seismic event.Augmented quality requirements consistent with NEI 12-02, Appendix A-1 will beapplied to this project.For seismic effects on the installed instrument channel components, 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 ofpostulated design basis event conditions at the location of the instrument channelcomponent using one or more of the following methods:* Substantial history of operational reliability in environments with significant vibration, such as for portable hand-held devices or transportation applications.

Such a vibration design envelope will be inclusive of the effectsof seismic motion imparted to the components proposed at the location ofthe proposed installation;

" Adequacy of seismic design and installation is demonstrated based on theguidance in Sections 7, 8, 9, and 10 of IEEE Standard 344-2004, IEEERecommended Practice for Seismic Qualification of Class 1 E Equipment forNuclear Power Generating

Stations, (Reference

7) or a substantially similarindustrial standard; or" Demonstration that proposed devices are substantially similar in design tomodels that have been previously tested for seismic effects in excess of theplant design basis at the location where the instrument is to be installed (glevels and frequency ranges).These requirements will be used as design input for the detailed design, vendorselection, and final implementation."

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 11 of 20Please provide the following:

a) A description of the specific method or combination of methods you intend toapply to demonstrate the reliability of the permanently installed equipment under BDB ambient temperature,

humidity, shock, vibration, and radiation conditions.

b) A description of the testing and/or analyses that will be conducted to provideassurance that the equipment will perform reliably under the worst-case credible design basis loading at the location where the equipment will bemounted.

Include a discussion of this seismic reliability demonstration as itapplies to (a) the level sensor mounted in the SFP area, and (b) any controlboxes, electronics, or read-out and retransmitting devices that will beemployed to convey the level information from the level sensor to the plantoperators or emergency responders.

c) A description of the specific method or combination of methods that will beused to confirm the reliability of the permanently installed equipment duringand following seismic conditions to maintain its required accuracy.

DNC Response:

(MPS2 and MPS3)a) Reliability of the permanently installed equipment under beyond-design-basis (BDB)ambient temperature,

humidity, shock, vibration, and radiation conditions will bedemonstrated through the equipment design, testing, or analysis.

The installed equipment will be tested and analyzed to meet the SeismicQualification Reporting

& Testing Standardization (SQURTS) seismic envelope forplants in the United States. The equipment mounts will be seismically configured forthe specific conditions and locations determined by the final design. Site specificanalysis will be performed to certify the mount's performance at the selectedlocation.

Equipment that will be located in the spent fuel pool will be certified for use in post-event conditions including temperatures in excess of 1000 Centigrade, 100 percentcondensing atmosphere, submerged operation at elevated chemical concentrations, and exposure to postulated radiation levels with the fuel storage rack uncovered foran extended period of time. The remaining equipment will be installed in theAuxiliary Building and qualified for use at temperatures up to 600 Centigrade, 100percent condensing atmosphere, and 1x104 rads integrated dose. The inherentshielding of the structures along the line of sight between the fuel and the equipment will result in negligible doses to the equipment, even for uncovered fuel.

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 12 of 20b) The new SFP level instrumentation system will be tested and analyzed to meet theSQURTS seismic envelope for plants in the United States. The equipment mountswill be seismically configured for the specific conditions and locations determined bythe final design. Site specific analysis will be performed to certify the mount'sperformance at the selected location.

The transmitter and display are currently planned to be located in the Auxiliary

Building, which is a Seismic Class I Structure.

c) The new SFP level instrumentation system will be tested and analyzed to meet theSQURTS seismic envelope for plants in the United States. Testing will confirm thatthe system maintains its design accuracy after a seismic event.Further details of the qualification and test program used to confirm the reliability ofthe permanently installed equipment during and following seismic conditions will beavailable upon completion of the final design, scheduled for December 2013, andwill be forwarded to the NRC during the subsequent scheduled status update.NRC RAI No. 5The OIP states, in part, thatThe primary instrument channel will be redundant to and independent of theback-up instrument channel.

Both the primary and back-up instrument channelswill be of the same technology, manufacturer, and model.Independence will be achieved through physical separation of the final installed instruments.

The two (2) permanently installed instrument sensors will beseparated by a distance comparable to the shortest length of a side of the pool,to the extent practical, based on the existing SFP geometry and construction.

The cables associated with each channel will follow separate and independent routes from the instruments to each electronics enclosure and from theenclosures to the displays.

The normal AC or DC power source for each channelwill be provided from independent and separate sources.Please provide the following:

a) A description of how the two channels of the proposed level measurement system meet this requirement so that the potential for a common causeevent to adversely affect both channels is precluded.

b) Further information on how each level measurement system, consisting oflevel sensor electronics,

cabling, and readout devices will be designed andinstalled to address independence through the application and selection ofindependent power sources, the use of physical and spatial separation, independence of signals sent to the location(s) of the readout devices, and the Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 13 of 20independence of the displays.

DNC Response:

(MPS2 and MPS3)The following response addresses both parts (a and b) of the requested information.

The MPS2 and MPS3 SFP level instrumentation systems are designed to be acomplete integrated solution that meets the requirements set forth in EA-12-051, NEI12-02 Rev. 1, and JLD-ISG-2012-03.

Each system provides two completely independent channels of level instrumentation.

Each channel is comprised of the GWRflexible probe, the probe mount, the transmitter, the instrument enclosure containing theDC power source and charger, sensor conditioning and communication circuitry, andlocal indication and is equipped with appropriate enclosure connections to remotedisplays and alternate power sources.The MPS2 sensors will be located on opposite sides of the SFP and the Unit 3 sensorswill be located on opposite ends of the longest side of the spent fuel pool. Thetransmitters and the instrument enclosures for both MPS2 and MPS3 (including display)will be located in the Auxiliary Building.

DNC's standard separation criteria for safetyrelated instrument cable at Millstone Power Station (MPS) will be applied.Each level channel is powered from its own dedicated 24-volt DC sealed batteries witha charging source connected to AC power. For MPS2, the AC charging source issupplied by two independent distribution panels. For MPS3, the AC charging source isfrom different breakers on the same distribution panel and each channel is protected from ground faults and surges from the common AC supply. In addition to the normalDC power supply to each channel, a back-up power source will also be provided toeach channel in the form of a portable back-up battery and connections to alternate power sources independent of the normal AC or DC power sources.NRC RAI No. 6The OIP states, in part, that"The normal power supply for each channel will be provided by different powersources such that loss of one power source will not result in the loss of bothchannels.

In addition to the normal plant AC and/or DC power supply to eachchannel, a back-up power source will also be provided to each channel in theform of a back-up battery independent of the normal AC or DC power sources."

Please provide the following:

If the level measurement channels are to be powered through a battery system Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 14 of 20(either directly or through an Uninterruptible Power Supply (UPS), please providethe design criteria that will be applied to size the battery in a manner thatensures, with margin, that the channel will be available to run reliably andcontinuously following the onset of the Beyond-Design-Basis (BDB) event for theminimum duration needed, consistent with the plant FLEX Program plans.DNC Response:

(MPS2 and MPS3)Each level channel is powered from its own dedicated 24-volt DC sealed batteries witha charging source connected to AC power. The seismically qualified batteries aredesigned to supply power for the entire level monitoring channel for at least seven daysafter a station black out (SBO). The enclosure and associated electronics are qualified for continuous operation in an operating environment of 0-500 Centigrade and 95percent humidity, non-condensing atmosphere without the need for cooling fans.Since the system is designed to support continuous operation over a seven-day orlonger SBO period, there is sufficient time to either restore or provide a back-up sourceof AC power to recharge the 24-volt batteries.

Deployment of an AC power source torecharge the level monitoring channel batteries will be included in the FLEXimplementing procedures.

As such, each channel will be available to run reliably andcontinuously following the onset of a BDB event for the minimum duration needed.NRC RAI No. 7The OIP states, in part, thatThe instrument channels will maintain their design accuracy following a powerinterruption or change in power source without requiring recalibration.

Since theinstrumentation is generally commercial off-the-shelf supplied components, thevendor published instrument accuracies will be verified as acceptable and will beused as a basis for final configuration and calibration procedures.

Accuracy requirements will consider SFP conditions, e.g., saturated water, steamenvironment, and concentrated borated water. Additionally, instrument accuracywill be sufficient to allow trained personnel to determine when the actual levelexceeds the specified lower level of each indicating range (levels 1, 2 and 3)without conflicting or ambiguous indication.

The GWR/TDR equipment selectedwill have accuracy within the resolution requirements of NEI 12-02, Figure 1.Specific details regarding accuracy will be obtained from the supplier during thedetailed design phase.

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 15 of 20Please provide the following:

a) An estimate of the expected instrument channel accuracy performance underboth (a) normal SFP level conditions (approximately Level 1 or higher) and (b)at the BDB conditions (i.e., radiation, temperature,

humidity, post-seismic andpost-shock conditions) that would be present if the SFP level were at theLevel 2 and Level 3 datum points.b) A description of the methodology that will be used for determining themaximum allowed deviation from the instrument channel design accuracy thatwill be employed under normal operating conditions as an acceptance criterion for a calibration procedure to flag to operators and to technicians thatthe channel requires adjustment to within the normal condition designaccuracy.

DNC Response:

(MPS2 and MPS3)a) The selected MPS2 and MPS3 SFP level instrumentation systems are expected tohave a design accuracy of +/- 2 inches and maintain this accuracy over the full rangeof operating conditions, including BDB conditions.

Design accuracy is also expectedto be maintained following a power interruption without the need for recalibration.

The final design accuracy will be available upon completion of the final design,scheduled for December 2013, and will be forwarded to the NRC during thesubsequent scheduled status update.b) Calibration of the SFP level system is performed in-situ.

Channel check andcalibration tolerances will be developed as part of the detailed design. The finalcalibration methodology will be available upon completion of the final design,scheduled for December 2013, and will be forwarded to the NRC during thesubsequent scheduled status update.NRC RAI No. 8OIP states, in part, thatInstrument channel design will provide for routine testing and calibration consistent with Order EA-12-051 and the guidance in NEI 12-02. The installed sensors will be designed to allow testing and/or calibration via in-situ methodswhile mounted in the pool. Removal of the sensor from the pool will not berequired for calibration or testing.Specific details regarding testing procedures and calibration requirements will bereviewed and determined with the supplier during the detailed design phase..

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 16 of 20Please provide the following:

a) A description of the capability and provisions the proposed level sensingequipment will have to enable periodic testing and calibration, including howthis capability enables the equipment to be tested in-situ.b) A description of how such testing and calibration will enable the conduct ofregular channel checks of each independent channel against the other, andagainst any other permanently-installed SFP level instrumentation.

c) A description of how functional checks will be performed, and the frequency atwhich they will be conducted.

Describe how calibration tests will be performed, and the frequency at which they will be conducted.

Provide a discussion as tohow these surveillances will be incorporated into the plant surveillance program.d) A description of what preventative maintenance tasks are required to beperformed during normal operation, and the planned maximum surveillance interval that is necessary to ensure that the channels are fully conditioned toaccurately and reliably perform their functions when needed.DNC Response:

(MPS2 and MPS3)a) The SFP level instrumentation system is capable of individual channel in-situcalibration and cross-calibration of the two independent level indications channels.

In-situ calibration is performed at the transmitter enclosure using internal displays.

The GWR determines pool depth by measuring the time of flight of a pulse from thetransmitter to the water interface and back to the transmitter's receiver.

A calibration device, provided by the manufacturer, incorporates time of flight delays equal tovarious pool levels. The device is connected to the transmitter and is exercised foreach level. Following calibration, the depth indications for both pool level sensorswill be compared as a final functional check of the level measurement.

b) The two independent channels of the SFP level instrumentation system will becross-checked against each other. Since the two wide range level channels areindependent, a channel check tolerance based on the design accuracy of eachchannel will be applied for cross comparison between the two channels.

Thetolerance is determined as the square root of the sum of the squares of the expecteddesign accuracy value, which is +/- 2 inches (reference the response to RAI-7).Therefore, the channel check tolerance would then be 2.8 inches.The wide range instruments may also be cross checked against the existing narrowrange pool level measurement channels where available (MPS3 only). If deemed Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 17 of 20necessary, tolerances for this cross check will be developed as part of the finaldesign.c) The responses to Items a) and b) above provide a description of the functional checks to ensure proper operation of the SFP level instrumentation system. Specificdetails of the functional and calibration test program, including frequencies, will bedeveloped in accordance with the vendor's recommendations as part of the finalinstrument design, scheduled for December 2013, and will be forwarded to the NRCduring the subsequent scheduled status update.d) Specific details of the preventive maintenance

program, including frequencies, willbe developed in accordance with the vendor's recommendations as part of the finalinstrument design, scheduled for December 2013, and will be forwarded to the NRCduring the subsequent scheduled status update.NRC RAI No. 9The OIP states, in part, thatThe conceptual design locates the electronic enclosure and primary display in theAuxiliary Building

[Main Control Room]. Specific details regarding the display anddisplay location(s) will be finalized during the detailed design phase.Please provide the following:

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

b) If location is other than the main control room, then provide justification forprompt accessibility to displays including primary and alternate routeevaluation, habitability at display location(s),

continual resource availability forpersonnel responsible to promptly read displays, and provisions forcommunications with decision makers for the various SFP drain downscenarios and external events.c) The reasons justifying why the locations selected enable the information fromthese instruments to be considered "promptly accessible" to various drain-down scenarios and external events.

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 18 of 20DNC Response:

(MPS2 and MPS3)The following response addresses each part of the requested information.

The current design places the instrument channel display units for both channels ofMPS2 and MPS3 in a Seismic Category 1 portion of the Auxiliary Building structure which will be accessible from the Main Control Room from primary and alternate routes.The final design will verify that the habitability of the access routes and locations in theAuxiliary Building structure where the instrument channel display units are planned willbe located outside of any very high radiation areas or locked high radiation area duringnormal operation or various drain-down conditions.

Communications with the MainControl Room and/or Technical Support Centers will be maintained via two-way radio.Staffing and communications capabilities for both units will be verified by the FLEXStrategy validation commitments made in response to Order EA-12-049.

Final design details for the instrument channel display units are scheduled to becompleted by December 2013. Upon completion of the final design, justification forprompt accessibility from the Main Control Room and habitability will be forwarded tothe NRC during the subsequent scheduled status update.NRC RAI No. 10The OIP states, in part, thatProcedures will be developed using guidelines and vendor instructions to addressthe maintenance, operation, and abnormal response issues associated with thenew SFP instrumentation.

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 andFlexible Coping Strategies (FLEX) Implementation Guide (Reference 8).Please provide a description of the standards, guidelines and/or criteria that will be usedto develop procedures for inspection, maintenance, repair, operation, abnormalresponse, and administrative controls associated with the SFP level instrumentation.

DNC Response:

(MPS2 and MPS3)Procedures for inspection, maintenance, repair, operation, abnormal

response, andadministrative controls associated with the SFP level instrumentation will be developed in accordance with existing controlled station administrative and technical procedures that govern procedure development.

These procedures ensure standardization of Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 19 of 20format and terminology and ease of use along with assurance of a consistent level ofquality.NRC RAI No. 11The OIP states, in part, thatProcesses will be established and maintained for scheduling and implementing necessary testing and calibration of the primary and back-up SFP levelinstrument channels to maintain the instrument channels at the design accuracy.

Testing and calibration of the instrumentation will be consistent with vendorrecommendations and any other documented basis. Calibration will be specific tothe mounted instrument and the monitor.Please provide the following:

a) Further information describing the maintenance and testing program thelicensee will establish and implement to ensure that regular testing andcalibration is performed and verified by inspection and audit to demonstrate conformance with design and system readiness requirements.

Include adescription of your plans for ensuring that necessary channel checks,functional tests, periodic calibration, and maintenance will be conducted forthe 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 beaddressed.

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

(MPS2 and MPS3)a) The maintenance and testing of the SFP level instrumentation systems will beincorporated into the normal station surveillance and work control processes basedon vendor recommendations for maintenance and periodic testing.

The calibration and maintenance program will include surveillances or testing to validate thefunctionality of each instrument channel within 60 days of a planned refueling outageconsidering normal testing scheduling allowances (e.g., 25%).

Serial No. 13-385RAI Response

-Order EA-12-051 Docket Nos. 50-336/423 Attachment Page 20 of 20The preventive maintenance, test and calibration program will be developed consistent with the vendor's recommendations.

This information will be available following completion of the final design, scheduled for December 2013, and will beforwarded to the NRC during the subsequent scheduled status update.b) The guidance in NEI 12-02, Rev. 1, states:The primary or back-up instrument channel can be out of service for testing,maintenance and/or calibration for up to 90 days provided the other channelis functional.

Additionally, compensatory actions must be taken if theinstrumentation channel is not expected to be restored or is not restoredwithin 90 days. If both channels become non-functioning then initiate actionswithin 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br /> to restore one of the channels of instrumentation andimplement compensatory actions (e.g., use of alternate suitable equipment orsupplemental personnel) within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />.In the event a channel of SPF level instrumentation is out of service for any reason,an administrative action statement will be entered to restore the channel to servicewithin 90 days. Functionality of the other channel associated with the same SFP asthe out of service channel will be confirmed via appropriate surveillance measuresuntil the non-functioning channel is returned to service.

As with item a) above, thefrequency of these actions will be developed consistent with vendorrecommendations.

c) In the event that a channel cannot be restored to service within the 90 day period,expedited actions to restore the channel would be initiated and tracked via DNC'sCorrective Action System. If both channels associated with the same SFP aredetermined to be non-functional, DNC will initiate appropriate compensatory actionswithin 24 hours2.777778e-4 days <br />0.00667 hours <br />3.968254e-5 weeks <br />9.132e-6 months <br />.The appropriate compensatory actions have not yet been specified.

Thedetermination of these actions is part of the overall effort to develop the BDBProgram administrative and implementation procedures.

The BDB Program willincorporate the guidance of NEI 12-02, including the requirements associated without of service time and is scheduled for completion in September 2014. Adescription of compensatory actions will be forwarded to the NRC during thesubsequent scheduled status update.