Millstone Power Station Unit 2 - Supplemental Information For … · REGARDING REMOVAL OF A LICENSE CONDITION, PROPOSED TECHNICAL SPECIFICATIONS BASES CHANGE AND FSAR CHANGE FOR ULTIMATE

Dominion Nuclear Connecticut, Inc."<b2Dominion5000 Dominion Boulevard, Glen Allen, VA 23060

Web Address: www.dom.con August 9, 2012

U.S. Nuclear Regulatory Commission Serial No. 12-474AAttention: Document Control Desk NSSL/MAE ROWashington, DC 20555 Docket No. 50-336

License No. DPR-65

DOMINION NUCLEAR CONNECTICUT, INC.MILLSTONE POWER STATION UNIT 2SUPPLEMENTAL INFORMATION FOR LICENSE AMENDMENT REQUESTREGARDING REMOVAL OF A LICENSE CONDITION, PROPOSED TECHNICALSPECIFICATIONS BASES CHANGE AND FSAR CHANGE FOR ULTIMATE HEATSINK TEMPERATURE MEASUREMENT

By letter dated July 17, 2012, Dominion Nuclear Connecticut, Inc. (DNC) requestedamendment to Operating License DPR-65 for Millstone Power Station Unit 2 (MPS2)pursuant to 10 CFR 50.90. The proposed changes would revise Technical SpecificationBases (TSB) 3/4.7.11, "Ultimate Heat Sink," Final Safety Analysis Report (FSAR)Section 9.7.2.1.2, "Design Criteria, Service Water System," and Appendix B, "AdditionalConditions, Facility Operating License No. DPR-65." The proposed TSB and FSARchanges would provide additional operational margin for measurement of the UltimateHeat Sink (UHS) temperature. The proposed change to Appendix B is to remove alicense condition that is no longer needed.

The NRC staff has reviewed DNC's application and concluded that additionalinformation is needed to allow the NRC staff to complete its detailed technical review ofthe requested license amendment. The requested supplemental information is providedin Attachment 1.

If you have any questions regarding this submittal, please contact Wanda Craft at (804)273-4687.

Sincerely,

J. P rice_ . . .. ... . . .Vice President- Nuclear Engineering RAIG D SLY,] Notary Public

I Commonwealth of VirginiaCOMMONWEALTH OF VIRGINIA My Reg. # 7518653:53

My Commission Expires December 31, 20.kCOUNTY OF HENRICO

The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today by J. Alan Price,who is Vice President - Nuclear Engineering of Dominion Nuclear Connecticut, Inc. He has affirmed before me that he is dulyauthorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are trueto the best of his knowledge and belief.

Acknowledged before me this . day of 2012.

My Commission Expires: , 1 .

NotaK

Serial No. 12-474ADocket No. 50-336

Page 2 of 2

Commitments made in this letter: None

Attachments:

1. Supplemental Information2. Various Plant Drawings3. Engineering Calculation Supporting The Uncertainty Analysis4. Calculation No. 98-ENG-02045D2 Rev. 00, Attachment A, Pages A2 and A3

cc: U.S. Nuclear Regulatory CommissionRegion I2100 Renaissance Blvd, Suite 100King of Prussia, PA 19406-2713

J. S. KimProject ManagerMail Stop 08 C2AU.S. Nuclear Regulatory CommissionOne White Flint North11555 Rockville PikeRockville, MD 20852-2738

NRC Senior Resident InspectorMillstone Power Station

DirectorBureau of Air ManagementMonitoring and Radiation DivisionDepartment of Environmental Protection79 Elm StreetHartford, CT 06106-5127


Attachment I

Supplemental Information

DOMINION NUCLEAR CONNECTICUT, INC.MILLSTONE POWER STATION UNIT 2


Attachment 1, Page 1 of 7

Supplemental Information

1. Provide the current technical specification basis for the numbers now in theTechnical Specifications with respect to temperature measurementuncertainty allowance.

DNC Response:

The 750F and 770F numbers in Technical Specification (TS) 3/4.7.11 represent thecurrent licensing and design basis values for the ultimate heat sink (UHS) as discussedin Final Safety Analysis Report (FSAR) Section 9.7.2.1.2, "Service Water System,Design Criteria."

T/S 3/4.7.11, "Ultimate Heat Sink" has no numbers that include a temperaturemeasurement uncertainty allowance.

Surveillance Procedure SP 2619A (and associated Form SP 2619A-001) is the principalsurveillance procedure for satisfying the TS surveillance requirement 4.7.11. Thissurveillance procedure uses 74.50F and 76.50F as procedural limits to verify the < 750Flimiting condition of operation and to verify the action statement (a) < 770F maximumallowable operating temperature (when UHS temperature exceeds 70 0F).

The current procedural limits are based upon a ±0.50F temperature measurementuncertainty allowance. This uncertainty allowance is intended to envelope theuncertainty associated with a single temperature measurement from TI-6928, TI-6929,or TI-6930. The temperature measurement uncertainty is quantified in Calculation 98-ENG-02405D2, "Millstone Unit 2 Service Water Inlet Temperature - Indicator AccuracyTI-6928, TI-6929 & TI-6930".

When the UHS temperature is > 700F, applicable temperature measurement uncertaintyis accounted for in the surveillance procedures in accordance with Millstone PowerStation, Unit 2 (MPS2) License Amendment No. 213 and associated safety evaluationreport (SER).

2. Provide drawingslsketches/P&lDs depicting detailed design of the physicalinstallation of the three sensors the licensee wants to average so that thestaff can agree that the licensee is monitoring the same process value.

DNC Response:

FSAR Figure 9.7-1, Sheets 2 and 3 are the Service Water (SW) System P&IDs, withSheet 3 showing the T-6928, T-6929, and T-6930 instrument process locations. The



requested P&IDs are contained in Attachment 2.

The vital switchgear room cooler SW inlet line thermowells are located in relatively smalldiameter lines and the thermowell configurations are depicted in Dominion NuclearConnecticut (DNC) Drawing 25203-28408, Sheet 312 (also included in Attachment 2).TE-6929 & TE-6930 use the "thermowell in a 2 ½ inch tee" thermowell configurationwhile T-6928 uses the "thermowell in 3-inch diameter line pipe" thermowellconfiguration.

Attachment 2 also contains various plant drawings that show the physical locations ofthe thermowells within the plant and the SW System.

3. Provide a statement as to whether the licensee intends to use the entireas-installed channel equipment from sensor through readout, or whether thelicensee is proposing to use temporary higher precision instrumentation.

DNC Response:

DNC intends to use the entire T-6928, T-6929, and T-6930 as-installed instrumentchannel (i.e., from the resistance temperature detector (RTD) to the local digitalreadout), when these instruments are available.

If DNC subsequently decides to use portable, higher precision temperature instrumentsto perform the UHS temperature surveillance, DNC would continue to ensure anappropriate temperature measurement uncertainty allowance and would evaluate thefuture changes under 10 CFR 50.59.

4. Provide exact model numbers of the sensors and instrument channeldevices performing the monitoring to verify that they are equivalent channelsperforming the readings.

DNC Response:

The three instruments which are used to indicate UHS temperature are TI-6928, TI-6929 and TI-6930. The three instrumentation loops are indication only, with no controlfunction, are non-QA and measure the SW vital switch gear room cooler inlettemperature.

Each instrumentation loop consists of an RTD, a temperature transmitter and a digitalindicator. Presently, the RTD is a Minco Model XS7927PK, the temperature transmitteris an Accutech Model AI-2000, and the digital indicator is a Microtronics Model5630031.

Note that future maintenance activities may alter these devices. Any impacts tomeasurement uncertainties would be reviewed and updated as necessary.



5. Discuss the methodology the licensee intends to use to average the values

(e.g., will the licensee be applying any weighting factors?, and if so, why).

DNC Response:

When three valid vital switchgear room cooler SW inlet temperature instruments areavailable, DNC intends to sum the three vital switchgear room cooler SW inlettemperature measurements and then to divide the total by three. No weighting factorswill be applied.

To address potential temperature instrument unavailability, DNC intends to compute anaverage temperature based upon at least two valid local SW supply header/branchtemperature instruments, coupled with an appropriate temperature measurementuncertainty allowance.

6. Discuss the methodology that will be used to provide the plant operatorswith the averaged value-(e.g., delivery of a SORC-reviewed and approvedengineering calculation performed hourly over the period of alternate techspecs?).

DNC Response:

To perform the surveillance, plant operators will record the TI-6928, TI-6929, and TI-6930 valid temperature measurement readings and manually calculate the averagetemperature.

7. Provide the uncertainty analysis for each loop, in the event the threechannels are not precisely identical.

DNC Response:

Please refer to Attachment 3 which contains the engineering calculation supporting theuncertainty analysis. The following are additional clarifications of the contents of thisdocument.

a) Guidelines for calculating instrument uncertainties are governed by a MillstonePower Station - Unit 2 design specification. The specification encompasses theuncertainties used for determining technical specification -values. It applies to themeasurement portion of the instrument loops, up to and including, as in this case,the display device. The specification states that "the preferred source for errorsis manufacturer's published data. Unless stated otherwise, manufacturer's datafor random errors may be assumed to be the ± 2a values. In the absence ofmanufacturer's data, plant data may be used provided the sample of instruments



is large enough to be statistically significant". Accordingly, the confidence levelfor this calculation is assumed to be ± 2cy.

b) Sensor and transmitter failures can manifest in one of several ways. The sensorfailure modes are either a short or an open circuit in the RTD. The Accutech Al-2000 monitors for failure via self-diagnostics. The Accutech is configurable withboth sensor and transmitter failsafe modes. A failed sensor or transmitter willresult in a high or low signal output to the indicator, and would be indicated onthe LED display by a max (100 0F) or min (0°F) temperature reading.

The configuration for the instruments in question: TT-6928, TT-6929, and TT-6930, is presently set as sensor failsafe HIGH and transmitter failsafe LOW.

c) The Accutech Model No. AI-2000 is a programmable temperature transmitter.The manufacturer's standard programmable configurations for these transmittersare for the RTD sensors stated within the manufacturer's literature. Millstoneordered the Accutech transmitters for local IDs TT-6928, TT-6929 and TT-6930to be configured for a 200 ohm RTD.

d) The Accutech accuracy is included with the indicator within the "Digital IndicatorAccuracy Term" in the calculation.

e) Calculation assumption 9.3 states: "No systematic errors (treated as bias) havebeen identified for these temperature loops". Therefore, all uncertainty terms aretreated as independent and random within the calculation.

f) As requested, a higher quality copy of Pages A2 and A3 from Calculation No. 98-ENG-02045D2 Rev. 00, Attachment A is provided in Attachment 4. Please notethat the attached pages were taken from Rev. 00 of the calculation. However,these pages remained unchanged up to and including Revision 2.

8. Provide the tolerance interval and confidence level of each channeluncertainty result to verify that they are all equivalent (i.e., to enable anapples-to-apples comparison).

DNC Response:

The three instrumentation loops each consist of the same components. Each loopincludes an RTD, a temperature transmitter, and a digital indicator.

The temperature transmitter and the digital indicator for each loop are contained withinthe same enclosure.



The RTD is calibrated or replaced every 5 years and the temperature transmitter anddigital indicator are calibrated once a year.

Since all three instrumentation loops consist of the same components with the samesurveillance interval for calibration for each component type, the three loops areconsidered equivalent with respect to their uncertainty value.

9. In Section 2.0, page 3, when discussing non-homogenous operatingconditions, the proposed revisions to both the TS Bases and UFSAR states -"SWS supply temperature measurements shall be obtained for each operableSWS loop and the highest valid SWS loop temperature shall be used todetermine the UHS temperature."

In Section 3.3, "Justification of the Change," page 6, it is stated - "Underpotentially non-homogeneous operating conditions, the UHS temperaturedetermination method will continue to use the highest valid measurement,coupled with a temperature measurement uncertainty allowance."

Is there an intended wording change from SWS to UHS in the above twosections - or are we simply reading too much into this?

DNC Response:

No, there is no intended wording change from SWS to UHS. For non-homogeneousconditions, the UHS temperature surveillance method will use the highest valid servicewater system (SWS) supply header/branch temperature measurement in the operableSW loop(s), coupled with an appropriate temperature measurement uncertaintyallowance.

10. What is meant by the phrase "valid measurement?" The staff's concern isthat when backwashing is being performed, intake temperatures can quicklyincrease. Please provide assurance that backwashing will not effectivelychange the UHS limits.

DNC Response:

The adjective "valid' was introduced in License Amendment No. 213 SER and it iscurrently reflected in FSAR Section 9.7.2 and TS 3/4.7.11 bases section.

The word "valid' is intended to ensure compliance with the TS in the descriptionsprovided in the FSAR and TS bases for the current UHS temperature surveillancemethod. For example:



" The vital switchgear room cooler SW flow can be isolated during normaloperation to support cooler maintenance activities. If there is no SW flow in theline, then the associated temperature indicator is measuring stagnant watertemperature and the associated local temperature measurement would beclassified as "invalid'.

* If it is suspected that a temperature measurement has been obtained from afailed instrument or instrument that has gone out-of-calibration, the measurementwould not be valid. For example, if T-6928 reads 69.50 F; T-6929 reads 90.5°F;and T-6930 reads 69.20 F; it is most likely that there is something wrong with T-6929 and TS 3.7.11 Action Statement b will not be entered. Rather, the 90.50FT-6929 temperature reading would be classified as "invalid' and correctiveactions would be initiated to investigate the loop's calibration because aninstrument problem is suspected given the available information.

L

Station operating procedures have been developed to address the condition that whenbackwashing is performed, intake temperatures can quickly increase. The proposedchange to FSAR Section 9.7.2.1.2 and T/S 3/4.7.11 bases section relative to UHStemperature surveillances are intended to address the conditions that occur prior to,during, or following backwash evolutions. Two types of backwash evolutions occur atthe plant. "Thermal backwashes" are performed to control biological growth while"debris backwashes" are performed to flush debris from the condenser water box. Inthis response, "backwash evolution" is intended to include both types of backwashes.

The operating procedure requires realignment of the SW system prior to backwashingsuch that the SW pumps supporting operable SW loops do not take suction from theintake bay where the backwash evolution is occurring. The procedure also containsguidance for evolution timing so that tidal currents will minimize the potential that hotwater would adversely impact an operable SW loop.

Specifically, at least one valid local SW temperature measurement in each operable SWloop shall be available during the backwash evolution.

When backwashing, the averaging method would not be used for any UHS temperaturesurveillance procedure or for the operations procedure that controls the backwashevolution.

The existing backwash evolution operating procedure contains a prerequisite (when theturbine is online) that there is a < 65 0F vital switchgear room cooler SW inlettemperature condition. The procedure also contains a precaution if seawatertemperature is greater than 70 0F, SW must be verified to be less than < 74.5°F (75°Fless a 0.50F instrument uncertainty allowance) locally using TI-6929 (SW Loop A - vitalswitchgear room cooler SW inlet) or TI-6930 (SW Loop B - vital switchgear room cooler



SW inlet). The backwash evolution procedure requires an operator to be stationed atthe vital switchgear room cooler SW inlet lines (with communication to the control room)to monitor TI-6929 and TI-6930. The proposed change has no impact upon this limitbecause the highest temperature will continued to be used and the uncertaintyallowance remains that associated with a single temperature instrument channel.

Please note that when performing the surveillance procedure used to verify UHStemperature to be within TS 3/4.7.11 temperature limits, all three instruments (TI-6928,TI-6929 and TI-6930) are used. When performing backwash evolutions, only instrumentTI-6929 or TI-6930 are closely monitored for convenience.

The thermal backwash evolution termination criteria include:

Initial UHS Temperature Thermal Backwash Termination Criteria< 65°F a Turbine Building Closed Cooling Water

(TBCCW) heat exchanger SW inlettemperature approaching 650F

Please note that thermal backwash is not performed if UHS temperature is > 650F. Thiscriterion is intended to prevent the < 750F limit from being exceeded and the resultingneed for a T/S 3.4.11 action statement entry.

The debris backwash evolution termination criteria include:

Initial UHS Temperature Debris Backwash Termination Criteria< 60°F a TBCCW heat exchanger SW inlet

temperature approaching 60°F> 60°F and < 650F any rise in TBCCW heat exchanger SW

inlet temperature> 650F and < 720F 1.5 minute time limit to ensure SW loop

temperature remains < 75°F

These termination criteria are intended to prevent the < 750F limit from being exceededand the resulting need for a T/S 3.4.11 action statement entry.


Attachment 2

Various Plant Drawings

DOMINION NUCLEAR CONNECTICUT, INC.MILLSTONE POWER STATION UNIT 2

Documents

Millstone Power Station Unit 2 - Supplemental Information For … · REGARDING REMOVAL OF A LICENSE CONDITION, PROPOSED TECHNICAL SPECIFICATIONS BASES CHANGE AND FSAR CHANGE FOR ULTIMATE