ML13275A240
| ML13275A240 | |
| Person / Time | |
|---|---|
| Site: | Millstone  |
| Issue date: | 09/19/2013 |
| From: | Stoddard D G Dominion, Dominion Nuclear Connecticut |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| 13-474 | |
| Download: ML13275A240 (6) | |
Text
I __--AirJFDominioW Dominion Nuclear Connecticut, Inc.5000 Dominion Boulevard, Glen Allen, VA 23060Web Address:
www.dom.com September 19, 2013U.S. Nuclear Regulatory Commission Attention:
Document Control DeskWashington, DC 20555Serial No.NSSL/MLCDocket No.License No.13-474RO50-423NPF-49DOMINION NUCLEAR CONNECTICUT, INC.MILLSTONE POWER STATION UNIT 3RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO REVISE TECHNICAL SPECIFICATION 6.8.4.FFOR PEAK CALCULATED CONTAINMENT INTERNAL PRESSUREBy letter dated April 25, 2013, Dominion Nuclear Connecticut, Inc. (DNC) submitted alicense amendment request (LAR) for Millstone Power Station Unit 3 (MPS3). Theproposed amendment would revise the peak calculated containment internal pressure forthe design basis loss of coolant accident described in Technical Specification (TS) 6.8.4.f,"Containment Leakage Rate Testing Program."
The peak calculated containment internalpressure, Pa, would increase from 41.4 psig to 41.9 psig. In a letter dated August 8, 2013,the Nuclear Regulatory Commission (NRC) transmitted a request for additional information (RAI) to DNC related to the LAR. DNC agreed to respond to the RAI by September 23,2013.The attachment to this letter provides DNC's response to the NRC's RAI.If you have any questions regarding this submittal, please contact Wanda Craft at (804)273-4687.
Sincerely, Q) 1%1Daniel G. StoddardSenior Vice President
-Nuclear Operations COMMONWEALTH OF VIRGINIACOUNTY OF HENRICO)))The foregoing document was acknowledged before me, in and for the County and Commonwealth aforesaid, today byDaniel G. Stoddard, who is Senior Vice President
-Nuclear Operations of Dominion Nuclear Connecticut, Inc. He hasaffirmed before me that he is duly authorized to execute and file the foregoing document in behalf of that Company, andthat the statements in the document are true to the best of his knowledge and belief.Acknowledged before me this J 9-A day of 5, 2013.My Commission Expires:
IA 3' (G:CRAIG D =SLYNotary PublicCommonwealth of VirginiaReg. # 7518653My Commission Expires December 31, 201..kNotayPbiAD,00'4'L Serial No. 13-474Docket No. 50-423Page 2 of 2Commitments made in this letter: None
Attachment:
Response to Request for Additional Information Regarding License Amendment Request to Revise Technical Specification 6.8.4.f for Peak Calculated Containment Internal Pressurecc: U.S. Nuclear Regulatory Commission Region I2100 Renaissance Blvd, Suite 100King of Prussia, PA 19406-2713 J. 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. 13-474Docket No. 50-423ATTACHMENT RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION REGARDING LICENSE AMENDMENT REQUEST TO REVISE TECHNICAL SPECIFICATION 6.8.4.F FOR PEAK CALCULATED CONTAINMENT INTERNAL PRESSUREDOMINION NUCLEAR CONNECTICUT, INC.MILLSTONE POWER STATION UNIT 3 Serial No. 13-474Docket No. 50-423Attachment 1, Page 1 of 3,By letter dated April 25, 2013, Dominion Nuclear Connecticut, Inc. (DNC) submitted alicense amendment request (LAR) for Millstone Power Station Unit 3 (MPS3). Theproposed amendment would revise the peak calculated containment internal pressurefor the design basis loss of coolant accident (LOCA) described in Technical Specification (TS) 6.8.4.f, "Containment Leakage Rate Testing Program."
The peakcalculated containment internal
- pressure, Pa, would increase from 41.4 psig to 41.9psig. In a letter dated August 8, 2013, the Nuclear Regulatory Commission (NRC)transmitted a request for additional information (RAI) to DNC related to the LAR. Thisattachment provides DNC's response to the NRC's RAI.Question 1Please verify that no change is needed in Technical Specification 3.6.1.4, "Containment Pressure,"
in order to maintain the calculated peak containment internal pressure (Pa)below the design limit. Please indicate the containment operating pressure used as theinitial condition for the Design-Basis Accident Loss-of-Coolant Accident analysisperformed.
DNC ResponseWhen Dominion first applied the approved DOM-NAF-3-0.0-P-A GOTHIC containment analysis methodology to MPS3, parametric studies were performed spanning the steadystate containment pressure requirements of TS 3.6.1.4 (10.6 psia to 14.0 psia). Themost adverse initial pressure for the peak containment pressure cases was an analytical value of 14.2 psia.The value of 14.2 psia was used as the initial condition in the reanalysis of the peakcontainment pressure for the design basis LOCA with the corrected Westinghouse mass and energy (M&E) data. No change was needed for TS 3.6.1.4 in order tomaintain Pa below the design limit.Question 2Please verify that this issue is not related to the recent EPITOME computer modelingerrors discovered by Westinghouse.
DNC ResponseMPS3 calculates containment response using Dominion's NRC-approved DOM-NAF 0.0-P-A GOTHIC methodology.
As part of that methodology, the vendor(Westinghouse) provides M&E inputs for the blowdown, refill and reflood phases of theLOCA transient.
For the post-reflood phase, the Dominion GOTHIC model contains an Serial No. 13-474Docket No. 50-423Attachment 1, Page 2 of 3internal reactor coolant system (RCS) model that is used to calculate the M&E releasesto the GOTHIC containment model.Westinghouse Nuclear Safety Advisory Letter (NSAL)-1 1-5 identified six issues thatcould potentially impact the MPS3 large break LOCA M&E calculations.
The six issues,which include generic errors, are as follows:1. The reactor vessel modeling did not include all the appropriate vessel metalmass available from the component drawings.
- 2. The reactor vessel modeling did not include all the appropriate vessel metalmass in the reactor vessel barrel/baffle region.3. The reactor coolant pump (RCP) homologous curve input incorrectly included anabsolute zero point coordinate.
- 4. The RCP homologous curve input incorrectly contained a sign error in acoordinate value.5. The LOCA M&E release analysis initializes at a non-conservative (low) steamgenerator (SG) secondary pressure condition.
- 6. An error was found in the EPITOME computer code that is used to determine theM&E release rate during the long-term (i.e., post-reflood)
SG depressurization phase of the LOCA transient.
Of these six identified issues, three were determined by Westinghouse in Table 1 ofNSAL-1 1-5 to affect the MPS3 large break LOCA containment M&E release analysis, specifically, Issues 1, 2 and 5 (above) regarding the reactor vessel metal mass error,vessel barrel/baffle metal mass modeling, and the SG secondary pressure.
Issues 1,2, and 5 were addressed in revised M&E inputs that were used in the GOTHIC-based containment reanalysis for MPS3 that generated the requested change in Pa.The EPITOME error listed as Issue 6 in NSAL-11-5 impacts the post-reflood M&Ereleases calculated by Westinghouse.
MPS3 does not use Westinghouse M&E dataduring the post-reflood phase, relying instead on the RCS model embedded in theDOM-NAF-3-0.0-P-A GOTHIC model. Therefore, MPS3 was not affected by theEPITOME computer code error.Question 3Please state if the Appendix J Type B and C test procedures do not require revisionupon approval of this proposed LAR. The American National Standards Institute (ANSI)56.8-1994, Section 3.3.2 requires that Type B and C testing be performed at a pressurenot less than Pa (except for airlock door seals, which may have a lower pressure Serial No. 13-474Docket No. 50-423Attachment 1, Page 3 of 3specified) and not more than 1.1 times Pa when a higher differential pressure results inincreased sealing.
Please discuss the site procedures for Type B and C testing, andprovide a discussion on the requirement that the testing be performed within a range ofpressures that, with the revised Pa, will continue to be within the range of pressures required by ANSI 56.8-1994.
DNC ResponseThe MPS3 Appendix J test procedures for Type B penetrations and Type Cpenetrations will require changes to identify the higher Pa value consistent with theproposed change to TS 6.8.4.f, "Containment Leakage Rate Testing Program."
The American National Standards Institute (ANSI) 56.8-1994, Section 3.3.2, requiresthat Type B and Type C testing be performed at a pressure not less than Pa and notmore than 1.1 times Pa when a higher differential pressure results in increased sealing.At MPS3, leakage rate testing is conducted using the "makeup flowrate" method asdescribed in Section 6.4.2 of ANSI 56.8-1994 which states: "the test volume shall bepressurized and maintained to at least Pa, using a pressure regulator to maintainpressure".
The makeup flowrate method is used to detect and measure local leakageacross pressure containing boundaries based on a constant pressure
- process, whilemeasuring discharge flow. In the makeup flow rate mode, the flow rate of the leak(discharge flow) can be read directly from the Volumetric Leak Rate Monitors (VLRM)digital flow rate readout.
Both procedures for Type B and Type C local leakage ratetesting identify the test pressure, Pa, as specified in TS 6.8.4.f and a maximum "not toexceed" design pressure, Pd (45 psig). Both specified pressures bound the range ofpressures required by ANSI 56.8-1994.
Question 4Please describe the steps that will be taken following approval of this amendment withregard to Appendix J Type A testing procedures.
DNC ResponseThe Type A integrated leakage rate test procedure used during the most recent Type Atesting at MPS3 is a vendor-controlled document that was approved by the Millstone technical subject matter experts and the facility safety review committee.
Thisprocedure is identified as a Category 1 (could affect containment isolation),
infrequently conducted or complex evolution.
As required by the procedure, the technical contentwill be validated prior to each use. The Type A test pressure is identified in the"Definitions" Section 2.2.9 of the vendor procedure and, as required, will be validated foraccuracy prior to the next scheduled test, currently planned for 2025. The value of Paidentified in the Type A test procedure is consistent with the Pa value identified in TS6.8.4.f.