ML13213A024

Millstone, Unit 2, Response to Request for Additional Information Regarding License Amendment Request for Changes to Technical Specification 3/4.7.11, Ultimate Heat Sink.

ML13213A024
Person / Time
Site:	Millstone
Issue date:	07/30/2013
From:	Scace S E Dominion Nuclear Connecticut, Dominion
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
Download: ML13213A024 (7)

Text

Dominion Nuclear Connecticut, Inc. DominioMillstone Power StationRope Ferry Road, Waterford, CT 06385U. S. Nuclear Regulatory Commission Serial No. 13-438Attention:

Document Control Desk NSSL/MLC ROWashington, DC 20555 I ) Docket No. 50-336License No. DPR-65DOMINION NUCLEAR CONNECTICUT, INC.MILLSTONE POWER STATION UNIT 2RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST FOR CHANGES TO TECHNICAL SPECIFICATION 3/4.7.11, "ULTIMATE HEAT SINK"By letter dated May 3, 2013, Dominion Nuclear Connecticut, Inc. (DNC) submitted alicense amendment request (LAR) for Millstone Power Station Unit 2 (MPS2). Theproposed amendment would modify Technical Specification (TS) 3/4.7.11, "Ultimate Heat Sink," to increase the current ultimate heat sink (UHS) water temperature limitfrom 750F to 80OF and change the TS Action to state, "With the ultimate heat sink water '-temperature greater than 800F, be in HOT STANDBY within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLDSHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />."In a letter dated June 26, 2013, the Nuclear Regulatory Commission (NRC) providedDNC an opportunity to supplement the LAR identified above. Supplemental information was provided to the NRC in a letter dated June 27, 2013. In a letter dated July 18,2013, the NRC transmitted a request for additional information (RAI) related to the LAR.DNC responded to the RAI in a letter dated July 19, 2013. In an e-mail dated July 23,2013, the NRC transmitted a second RAI to DNC. Attachment 1 to this letter containsDNC's response.

Additionally, in a clarification call with the NRC on July 23, 2013, DNCagreed to provide supplemental information to DNC's response to RAI-1 from letterdated July 19, 2013. This information is also included in Attachment 1.If you have any questions or require additional information, please contact Wanda Craftat (804) 273-4687.

Sincerely, S..ScacEa~

Site Vice President

-Millstone Power StationSTATE OF CONNECTICUT COUNTY OF NEW LONDONThe foregoing document was acknowledged before me, in and for the County and State aforesaid, today by S. E. Scace, who is SiteVice President of Millstone Power Station.

He has affirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that Company, and that the statements in the document are true to the best of his knowledge and belief.Acknowledged before me this 3A day of 2013.My Commission Expires:WM. E. BROWN ot-ary PubNOTARYPUBLIC MY COMMISSION EXPIRES MAR. 31,.2016 Serial No. 13-438Docket No. 50-336Page 2 of 2Commitments made in this letter:NoneAttachments:

1. Response to Request for Additional Information Regarding License Amendment Request for Changes to Technical Specifications 3/4.7.11, "Ultimate Heat Sink"2. Proto-Power Calculation 98-119, Rev. B3. Excerpt from DNC Calculation 94-DES-i 111 -M2, Revision 00.4. Excerpt from DNC Calculation 94-DES-1111

-M2, Revision 00, Change 1.cc: U.S. Nuclear Regulatory Commission Region I2100 Renaissance Blvd, Suite 100King of Prussia, PA 19406-2713 James S. KimProject ManagerU.S. Nuclear Regulatory Commission One White Flint North, Mail Stop 08 C2A11555 Rockville PikeRockville, MD 20852-2738 NRC Senior Resident Inspector Millstone Power StationDirector, Radiation DivisionDepartment of Energy and Environmental Protection 79 Elm StreetHartford, CT 06106-5127 Serial No 13-438Docket No. 50-336Attachment 1Response to Request for Additional Information Regarding License Amendment Request for Changes to Technical Specifications 3/4.7.11, "Ultimate Heat Sink"Dominion Nuclear Connecticut, Inc.Millstone Power Station Unit 2 Serial No 13-438Docket No. 50-336Response to RAI for MPS2 Ultimate Heat SinkAttachment 1, Page 1 of 4Response to Request for Additional Information Regarding License Amendment Request for Changes to Technical Specifications 3/4.7.11, "Ultimate Heat Sink"By letter dated May 3, 2013, Dominion Nuclear Connecticut, Inc. (DNC) submitted alicense amendment request (LAR) for Millstone Power Station Unit 2 (MPS2). Theproposed amendment would modify Technical Specification (TS) 3/4.7.11, "Ultimate HeatSink," to increase the current ultimate heat sink (UHS) water temperature limit from 750Fto 80°F and change the TS Action to state, "With the ultimate heat sink water temperature greater than 800F, be in HOT STANDBY within 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN withinthe following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />."In a letter dated June 26, 2013, the Nuclear Regulatory Commission (NRC) provided DNCan opportunity to supplement the LAR identified above. Supplemental information wasprovided to the NRC in a letter dated June 27, 2013. In a letter dated July 18, 2013, theNRC transmitted a request for additional information (RAI) related to the LAR. DNCresponded to the RAI in a letter dated July 19, 2013. In an e-mail dated July 23, 2013, theNRC transmitted a second RAI to DNC related to the LAR. This attachment containsDNC's response.

Additionally, in a clarification call with the NRC on July 23, 2013, DNCagreed to provide supplemental information to DNC's response to RAI-1 from letter datedJuly 19, 2013. The supplemental is provided at the end of this attachment.

EMERGENCY DIESEL GENERA TOR RAIBackground The licensee has provided a response to RAI-3 of NRC letter dated July 18, 2013 in aletter dated July 19, 2013. RAI 3 was submitted regarding design operational limits of theemergency diesel generators (EDG).IssuesA) Each EDG is cooled by 3 heat exchangers in series on the Service Water (SW) side.The licensee has stated that the first cooler in series, i.e. the intercooler (X-83A or B)for each EDG, is the controlling component, meaning that if the cooling requirements ofthe intercooler is met then the cooling requirements of other heat exchangers, i.e. thelube oil cooler and the jacket water cooler, are met.B) The vendor data sheet for the intercooler specifies greater heat exchangerequirements and SW flow requirements than what the licensee has stated in theirresponse to RAI-3. For an EDG load of 2750 KW and seawater (SW) temperature of750F the differences are stated in the table below:Vendor Data Sheet RAI 3 ResponseIntercooler heat load at 2750KW 2,769,000 BTU/HR 2,067,000 BTU/HRSeawater flow rate 700 GPM 507 GPM Serial No 13-438Docket No. 50-336Response to RAI for MPS2 Ultimate Heat SinkAttachment 1, Page 2 of 4RAI-11) Please explain fully in detail and prove the statement that the intercooler (X-83A or B)for each EDG is the controlling component, meaning that if the cooling requirements ofthe intercooler is met then the cooling requirements of other heat exchangers, i.e. thelube oil cooler and the jacket water cooler, are met.DNC Response to RAI-1Calculation 98-119, Revision B (provided in Attachment

2) provides the thermalperformance analysis results for the MPS2 EDG heat exchangers.

The basis for DNC'sstatement specifying that the EDG intercooler heat exchanger is the limiting heatexchanger is provided on Page 35 of Calculation 98-119. The calculation was performed by first determining the required service water flow rate to the first heat exchanger (i.e., theintercooler) and then determining the resulting service water outlet temperature from thatheat exchanger.

That outlet temperature was then used as the inlet temperature for thenext heat exchanger (i.e., lube oil cooler) since they are arranged in series. If acceptable results for the lube oil cooler were obtained, then the process was repeated for the thirdheat exchanger (i.e., jacket water cooler).

Note that the increase in UHS temperature from75°F to 80'F requires an increase in service water flow to the EDGs. This increased flowpartially compensates for the increase in inlet temperature which mitigates the effect onthe downstream heat exchanger(s).

The 50F increase in UHS temperature and therequired increase in service water flow, results in an intercooler heat exchanger outlettemperature rise of 3.3°F. The increased service water flow that is now required for 80'FUHS temperature was available as margin between the required and delivered flow ratesfor the EDG heat exchangers.

RAI-22) Explain and justify the differences in vendor requirements and the response to RAI 3,as listed in the table above.DNC Response to RAI-2Flow RateAs shown in Calculation 12-328, "Equivalent Thermal Performance of the Unit 2 EDG HeatExchangers for UHS Temperature Increase" (see Pages 2 and 3 of Attachment 9 of DNCletter dated July 19, 2013), the 507 gpm value was used in calculations to support a UHStemperature of 770F, rather than 750F. The 507 gpm flow rate was used in DNCCalculation 94-DES-1111-M2, Revision 00, Change 1 (see Attachment 4). For a UHStemperature of 800F, a flow rate of 637 gpm is required.

Heat LoadDNC Calculation 94-DES-I 111 -M2, Revision 00 (also known as Proto-Power Calculation 94-053) (excerpt provided in Attachment

3) shows that the heat load in the vendor data Serial No 13-438Docket No. 50-336Response to RAI for MPS2 Ultimate Heat SinkAttachment 1, Page 3 of 4sheet is based on a 3250 KW, 30 minute rating, at 118% of design load. The calculation also provides a graph of EDG air cooler (or intercooler) heat load versus EDG loading.

Atthe design loading condition of 2750 KW, the air cooler heat load is 2.067x106 Btu/hr.Change 1 to this calculation (Attachment

4) slightly revised the heat load downward,

however, Calculation 12-328 (provided as Attachment 9 in DNC Letter dated July 19,2013) conservatively used the 2.067x106 Btu/hr heat load .Note that the MPS2 FSARstates that the continuous load rating of the MPS2 EDGs is 2750 KW and there are noscenarios where that load is exceeded.

Supplemental Information for Response to RAI-1 (from DNC Letter Dated July 19, 2013)The containment loss of coolant accident (LOCA) and main steam line break (MSLB)analyses modeled the reactor building closed cooling water (RBCCW) system and itsinterface with containment (via the containment air recirculation (CAR) fans in the injection mode and the CAR fans and shutdown cooling (SDC) heat exchangers in the sumprecirculation mode). The RBCCW spent fuel pool (SFP) heat load was included in theseanalyses.

For simplicity, other heat loads on the RBCCW system were included in theanalyses as a single heat load. These analyses were performed under two different assumed conditions:

1) to minimize heat transfer (for determining worst case containment conditions) and, 2) to maximize heat transfer (for determining highest RBCCWtemperature).

The latter condition, for which a RBCCW temperature profile wasdeveloped, was then used as input to subsequent calculations which evaluated the impactof the higher RBCCW temperature on critical components.

A summary of the results are as follows:Engineered Safety Features (ESF) Room CoolersThe analysis for the ESF room coolers used the RBCCW temperature

profile, as well asheat loads in the room (running equipment, hot piping, etc.), to determine a roomtemperature profile which was then used as input to evaluate equipment environmental qualification (EEQ) components in those rooms. The results of the analysis concluded that with an increase in UHS temperature to 800F, the ESF room equipment remainswithin its EEQ design limits.SFP CoolingFor SFP cooling, RBCCW flow is isolated at the start of the LOCA. RBCCW flow is thenrestored four hours post LOCA. The RBCCW temperature profile is then used todetermine the SFP temperature profile.

The SFP temperature is assumed to be at itsmaximum allowed temperature of 150°F at the start of the accident and to heat up due toloss of cooling for four hours. Based on these considerations, the maximum SFPtemperature is analytically determined to remain below the allowable temperature of2000F.

Serial No 13-438Docket No. 50-336Response to RAI for MPS2 Ultimate Heat SinkAttachment 1, Page 4 of 4Pumps with RBCCW Cooled SealsThe seals for the high pressure safety injection (HPSI) and low pressure safety injection (LPSI) pumps were previously evaluated based on an assumed RBCCW supplytemperature of 147°F and a pumped fluid temperature of 3000F. This evaluation determined a resultant HPSI and LPSI pump seal temperature of 1920F and 2320F,respectively.

For an increase in UHS temperature to 800F, the maximum RBCCW supplytemperature was increased to 1490F. This change increases the average temperature ofthe RBCCW through any heat exchanger by 20F. Conservatively assuming 300°F for thepumped fluid (actual maximum calculated temperature is 2340F), increasing the RBCCWcooling water temperature to 149°F will result in an expected HPSI and LPSI seal outlettemperature of 1940F and 2340F, respectively.

These temperatures are within the 250°Facceptance criteria for acceptable seal performance.

The containment spray (CS) pump seals were previously evaluated at an RBCCWtemperature of 1470F. Using vendor supplied information, it was concluded that, at anRBCCW temperature of 1490F, the CS pump seal temperature would be 2250F, which iswithin the design maximum seal temperature of 3000F.