ML14142A016
| ML14142A016 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 05/12/2014 |
| From: | Powell G T South Texas |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NOC-AE-14003134, STI: 33874194, TAC MF2477, TAC MF2478 | |
| Download: ML14142A016 (13) | |
Text
Nuclear Operating CompanySouth Texas Propect Electric Generating Station P.. Box 289 Wdsworth. Txas 77483May 12, 2014NOC-AE-1 400313410 CFR 50.90U.S. Nuclear Regulatory CommissionAttention: Document Control DeskWashington, DC 20555-0001South Texas ProjectUnits 1 & 2Docket Nos. STN 50-498, STN 50-499STPNOC Response to Request for Additional InformationRegarding the License Amendment Request to the Fire Protection ProgramTAC Nos. MF2477 and MF2478References:1. Letter from D.W. Rencurrel, STP Nuclear Operating Company, to NRCDocument Control Desk, "License Amendment Request for Approval of aRevision to the South Texas Project Fire Protection Program Related to theAlternative Shutdown Capability," dated July 23, 2013. (NOC-AE-13002962)(ML13212A243)2. E-mail from B. Singal, NRC, to L. Sterling, STP Nuclear Operating Company,"Request for Additional Information License Amendment Request Revision tothe Fire Protection Program South Texas Project, Units 1 and 2", TACsMF2477 and MF2478, dated April 11, 2014. (AE-NOC-14002524)On July 23, 2013, STP Nuclear Operating Company (STPNOC) submitted a license amendmentrequest to revise the South Texas Project Units 1 and 2 Fire Protection Program related toalternate shutdown capability (Reference 1). In the event that a fire requires evacuation of thecontrol room, the proposed amendment requested crediting the performance of certain operatoractions, including one automatic operation, prior to evacuation.By e-mail dated April 11, 2014 (Reference 2), the NRC requested additional information relatedto the STPNOC amendment request. Attachment 1 provides the STPNOC response to theRequests for Additional Information (RAI). Supplemental information that supports the RAIresponses is provided in Attachment 2.STI: 33874194 NOC-AE-14003134Page 2 of 3There are no commitments in this letter.If there are any questions regarding this letter, please contact Rafael Gonzales at (361) 972-4779 or me at (361) 972-7566.I declare under penalty of perjury that the foregoing is true and correct.Executed on ___ 17, __t_G.T. PowellSite Vice PresidentrjgAttachments:1. Request for Additional Information License Amendment Request Revision to the FireProtection Program South Texas Project, Units 1 and 22. Request for Additional Information License Amendment Request Revision to the FireProtection Program South Texas Project, Units 1 and 2 Application Revisions NOC-AE-1 4003134Page 3 of 3cc:(paper copy)(electronic copy)Regional Administrator, Region IVU. S. Nuclear Regulatory Commission1600 East Lamar BoulevardArlington, TX 76011-4511Balwant K. SingalSenior Project ManagerU.S. Nuclear Regulatory CommissionOne White Flint North (MS 8 B1)11555 Rockville PikeRockville, MD 20852NRC Resident InspectorU. S. Nuclear Regulatory CommissionP. O. Box 289, Mail Code: MN116Wadsworth, TX 77483Jim CollinsCity of AustinElectric Utility Department721 Barton Springs RoadAustin, TX 78704A. H. Gutterman, EsquireMorgan, Lewis & Bockius LLPBalwant K. SingalU. S. Nuclear Regulatory CommissionJohn RaganChris O'HaraJim von SuskilNRG South Texas LPKevin PolioCris EugsterL. D. BlaylockCity Public ServicePeter NemethCrain Caton & James, P.C.C. MeleCity of AustinRichard A. RatliffRobert FreeTexas Department of State Health Services
Attachment
1NOC-AE-14003134ATTACHMENT 1Request for Additional Information License AmendmentRequest Revision to the Fire Protection Program SouthTexas Project, Units 1 and 2
Attachment
1NOC-AE-14003134Page 1 of 7REQUEST FOR ADDITIONAL INFORMATIONLICENSE AMENDMENT REQUESTREVISION TO THE FIRE PROTECTION PROGRAMSOUTH TEXAS PROJECT, UNITS 1 AND 2By letter dated July 23, 2013 (Agencywide Documents Access and Management System(ADAMS), Accession No. ML13212A243, STP Nuclear Operating Company, (the licensee)requested a license amendment for the South Texas Project (STP), Units 1 and 2, from theircommitment to certain technical requirements of Title 10 of the Code of Federal Regulations (10CFR) Part 50, Appendix R, Section Ill.L, as documented in the STP Fire Hazards AnalysisReport, for crediting the performance of certain operator actions in the control room in the eventthat a fire necessitates the evacuation of the control room.The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the information provided bythe licensee and determined that the following additional information is needed to complete thereview.Request for Additional Information (RAI)RAI-01 Physical SeparationSection 3.5 of Enclosure 1 to the request refers to physical and flame retardant barriers andthermal insulating material installed between redundant devices but does not specify whether aparticular assembly is utilized for this purpose and whether it carries any classification or ratingby a recognized testing laboratory.Please state what materials or assemblies are used to accomplish the physical separation notedin Section 3.5 and provide any applicable design or testing certifications for their use in thenoted applications.RAI-02 Transfer of ControlSection 3.7.4 of Enclosure 1 to the request states that the required actions are backed up fromoutside the control room within a short period of time but does not specify what that duration isand whether the operator manual actions that are performed outside the control room havebeen evaluated for feasibility and reliability, e.g., per NUREG-1 852 "Demonstrating theFeasibility and Reliability of Operator Manual Actions in Response to Fire (NUREG-1852),"October 2007 (ADAMS Accession No. ML073020676)Please state what the licensee has assumed for the time necessary to back up the control roomactions at the alternate location and provide a technical basis for the assumed time, including adiscussion of feasibility and reliability, to perform the operator manual actions.RAI-03 Typo in Description of Limiting EventThere appears to be a typo in the description of the Case lb results in Section 3.8.4 ofEnclosure 1. The licensee stated that "Core peak exit fluid temperature remains well belowapproaches 1200°F so that fuel integrity is not challenged," but it is not clear whether core peakexit fluid temperature remains well below 1200TF or approaches 12000F. Please clarify thestatement noted above.
Attachment
1NOC-AE-14003134Page 2 of 7RAI-04 Fire Model AnalysisSection A3.2.2 of Enclosure 1 states that smoke detectors are present in each cabinet adjacentto the exhaust ventilation duct but it is not clear whether these are the same fire detectors notedin Section 3.3. Section A3.2.2 also states that the automatic detection system does not isolateventilation upon actuation.RAI-04.1Please clarify what type of detectors are located in the control cabinets and provide atechnical justification for why receipt of a detection alarm signal does not promptisolation of the ventilation system as to not propagate products of combustion across fireareas or zone boundaries, e.g. from outside the control room fire area or the relay roomfire zone.Table A3.1 provides the cable acceptance criteria used in the fire modeling analysis but doesnot include any tenability criteria for operators.RAI-04.2Please clarify whether the licensee evaluated any tenability criteria to understandwhether the control room remains habitable during the postulated fire scenarios andprovide a technical justification for any assumptions related to main control roomhabitability made during the analysis. If tenability was evaluated, provide the criteriaused to do so and state whether an evacuation due to a loss of tenability would occur forthe postulated fire scenarios.Section A3.2.4 describes the ignition sources and fire size assumed for the analysis but doesnot state what material or fuel properties were used in the analysis.RAI-04.3Please describe the material properties of the combustibles that were modeled and thematerial properties used in the model. If there were differences between the installedand modeled material properties provide a technical basis that justifies how the modeledmaterial properties are bounding.Section A3.3 states that ignition of secondary combustibles around CP001 was assumed not tooccur but does not state why this was assumed or whether it was based on modeling results.
Attachment
1NOC-AE-14003134Page 3 of 7RAI-04.4Please provide a technical justification for the assumption that secondary combustiblesare assumed not to ignite.Section A3.4.1 makes reference to an ambient heat flux and depicts graphs of certain criteriaover time but does not explain what is intended by this term or where the measurements wererecorded within the model domain.RAI-04.5Please explain what is intended by the term ambient heat flux and why Figure A3.3appears to show it exceeding the acceptance criterion for cabinet CP001. In addition,describe the locations of the data collection nodes in the model that recorded the statedvalues for heat flux and temperature and provide a technical justification as to why thedata collection locations are considered bounding.
Attachment
1NOC-AE-14003134Page 4 of 7NRC Request for Additional Information (RAI)NRC Request -RAI-01 Physical SeparationSection 3.5 of Enclosure 1 to the request refers to physical and flame retardant barriers andthermal insulating material installed between redundant devices but does not specify whether aparticular assembly is utilized for this purpose and whether it carries any classification or ratingby a recognized testing laboratory.Please state what materials or assemblies are used to accomplish the physical separation notedin Section 3.5 and provide any applicable design or testing certifications for their use in thenoted applications.STPNOC Response:Section 3.5 discusses the separation criteria used at STP between the turbine trip circuit(non-class 1 E circuit) and the reactor trip circuitry. The thermal barrier discussed insection 3.5 is Siltemp and tested by Wyle Laboratories for faulted circuits conditions asdescribed in Section 5.6 of IEEE 384 and NRC Regulation Guide 1.75 and carries norated hourly classification. As described in section 3.5, once the reactor trip signal isactuated, an automatic turbine trip signal is generated in each of two solid stateprotection system (SSPS) logic and actuation trains located outside of the Main ControlRoom (MCR) as shown in Figure 4 in Enclosure 1. The manual turbine trip circuitry islocated in the MCR panel 07 and the reactor tip switch is located in MCR panel 05.Therefore, a fire in either MCR panel will not affect the other circuitry ensuring that areactor trip and turbine trip are generated simultaneously in the SSPS cabinets.NRC Request -RAI-02 Transfer of ControlSection 3.7.4 of Enclosure 1 to the request states that the required actions are backed up fromoutside the control room within a short period of time but does not specify what that duration isand whether the operator manual actions that are performed outside the control room havebeen evaluated for feasibility and reliability, e.g., per NUREG-1 852 "Demonstrating theFeasibility and Reliability of Operator Manual Actions in Response to Fire (NUREG-1852),"October 2007 (ADAMS Accession No. ML073020676)Please state what the licensee has assumed for the time necessary to back up the control roomactions at the alternate location and provide a technical basis for the assumed time, including adiscussion of feasibility and reliability, to perform the operator manual actions.STPNOC Response:STP has all Control Room actions backed up within 10 minutes, except the ReactorCoolant Pump 13.8 kV breakers which will be opened within 20 minutes. The 10 minutelimit was used in the original Westinghouse Safe Shutdown calculations and has beenverified in the STP thermal hydraulic calculation. The Control Room EvacuationProcedure has been walked down and verified that the time of 10 minutes or less isachievable. STP has a Timeline and Manual Action Feasibility Report "51-9094209-001", it is not only for all the back-up actions but all manual actions taken in any FireArea at STP. This evaluation also includes a manual action feasibility checklist for eachmanual action identified, taking into consideration the methodology detailed in the NRCNUREG-1852.
Attachment
1NOC-AE-14003134Page 5 of 7NRC Request -RAI-03 Typo in Description of Limiting EventThere appears to be a typo in the description of the Case lb results in Section 3.8.4 ofEnclosure 1. The licensee stated that "Core peak exit fluid temperature remains well belowapproaches 1200°F so that fuel integrity is not challenged," but it is not clear whether core peakexit fluid temperature remains well below 1200TF or approaches 12000F. Please clarify thestatement noted above.STPNOC Response:Operators are able to control SG level at approximately 50 percent with AFW flow until voidingin the RCS decreases to such a point that indicated pressurizer water level is restored. Corepeak exit fluid temperature remains well below 1200°F so that fuel integrity is not challenged.NRC Request -RAI-04. Fire Model AnalysisSection A3.2.2 of Enclosure 1 states that smoke detectors are present in each cabinet adjacentto the exhaust ventilation duct but it is not clear whether these are the same fire detectors notedin Section 3.3. Section A3.2.2 also states that the automatic detection system does not isolateventilation upon actuation.NRC Request -RAI-04.1Please clarify what type of detectors are located in the control cabinets and provide atechnical justification for why receipt of a detection alarm signal does not promptisolation of the ventilation system as to not propagate products of combustion across fireareas or zone boundaries, e.g. from outside the control room fire area or the relay roomfire zone.STPNOC Response:STP Main Control Room has ionization detectors below and above the suspendedceiling and in the MCR cabinets to provide early warning. These detectors alarm in thelocal panel and the room itself. The detectors are only specified as smoke detectors inthe report. Only a qualitative discussion of the detection is required because detection isnot credited in the fire model in any way. The discussion of the detection is only made topresent defense-in-depth. In addition, there is no automatic interlock between the MCRdetection system and the MCR cabinet exhaust ventilation. STP does have smokedetectors in the intake ductwork that auto actuate a smoke damper in the inlet ductworkand keeps smoke from entering the MCR. The outlet ductwork has smoke detectors forindication only. Procedures are in place so the control room staff can isolate the outletductwork and manually enter into a smoke purge mode of operation if necessary.
Attachment
1NOC-AE-14003134Page 6 of 7Table A3.1 provides the cable acceptance criteria used in the fire modeling analysis but doesnot include any tenability criteria for operators.NRC Request -RAI-04.2Please clarify whether the licensee evaluated any tenability criteria to understandwhether the control room remains habitable during the postulated fire scenarios andprovide a technical justification for any assumptions related to main control roomhabitability made during the analysis. If tenability was evaluated, provide the criteriaused to do so and state whether an evacuation due to a loss of tenability would occur forthe postulated fire scenarios.STPNOC Response:The conditions in the entire MCR are discussed in the last paragraph of Section A3.4.1.The Consolidated Model of Fire and Smoke Transport (CFAST) software results for thecompartment representing the MCR as a whole are extremely conservative because noventilation out of the compartment was modeled. Even with this conservatism no hotgas layer is formed. As discussed in the report the majority of the MCR is expected toremain at near ambient conditions.Section A3.2.4 describes the ignition sources and fire size assumed for the analysis but doesnot state what material or fuel properties were used in the analysis.NRC Request -RAI-04.3Please describe the material properties of the combustibles that were modeled and thematerial properties used in the model. If there were differences between the installedand modeled material properties provide a technical basis that justifies how the modeledmaterial properties are bounding.STPNOC Response:Based on the walkdown performed in the MCR, the bounding combustibles weredetermined to be cable insulation. Furthermore, the greatest concentration of the cableinsulation is in the MCR cabinets. As a result, the MCR cabinets were chosen as thebounding combustible material. Table G-1 of NUREG 6850 Vol. 2 providesrecommended Heat Release Rate (HRR) values for electrical fires. The mostconservative (98th percentile) HRR for the cabinet type that most closely fits the designof the MCR cabinets was used. A HRR curve was then generated from the peak valuein accordance with Section 3.1.1 of NUREG 1934. This HRR curve was the input intothe CFAST model. It represents the most conservative HRR curve expected based onthe combustible loading within the MCR.
Attachment
1NOC-AE-1 4003134Page 7 of 7Section A3.3 states that ignition of secondary combustibles around CP001 was assumed not tooccur but does not state why this was assumed or whether it was based on modeling results.NRC Request -RAI-04.4Please provide a technical justification for the assumption that secondary combustiblesare assumed not to ignite.STPNOC Response:Based on the walkdown performed in the MCR, there are no secondary combustiblesimmediately around the MCR cabinets. Transient combustibles in the MCR are strictlymanaged per station procedure (i.e. Control of Transient Fire Loads and Use ofCombustible and Flammable Liquids and Gases), so no transient combustibles wererequired to be considered. The MCR cabinets are constructed with double walls withoutan air gap with ventilation in each cabinet. Based on this configuration and inaccordance with the guidance in Appendix S of NUREG 6850 propagation betweencabinets is not required to be assumed.Section A3.4.1 makes reference to an ambient heat flux and depicts graphs of certain criteriaover time but does not explain what is intended by this term or where the measurements wererecorded within the model domain.NRC Request -RAI-04.5Please explain what is intended by the term ambient heat flux and why Figure A3.3appears to show it exceeding the acceptance criterion for cabinet CP001. In addition,describe the locations of the data collection nodes in the model that recorded the statedvalues for heat flux and temperature and provide a technical justification as to why thedata collection locations are considered bounding.STPNOC Response:The thermoset cable acceptance criteria in Table 8-2 of NUREG 6850 Vol. 2 are given inboth temperature and heat flux. Because CFAST calculates parameters on a percompartment basis, the ambient heat flux represents the heat flux that may be seenanywhere throughout the compartment. The fact that the acceptance criteria areexceeded in cabinet CP001 is expected due to the fire originating within that cabinet.Because the cable damage logic requires damage to cables within multiple cabinets, thisis acceptable.
Attachment
2NOC-AE-14003134ATTACHMENT 2Request for Additional Information License AmendmentRequest Revision to the Fire Protection Program SouthTexas Project, Units I and 2Application Revisions
Attachment
2NOC-AE-14003134Page 1 of 1Before:(Excerpt from Section 3.8.4 DID Thermal-Hydraulic Analysis)Operators are able to control SG level at approximately 50 percent with AFW flow until voidingin the RCS decreases to such a point that indicated pressurizer water level is restored. Corepeak exit fluid temperature remains well below approaches 1200°F so that fuel integrity is notchallenged.After:(Excerpt from Section 3.8.4 DID Thermal-Hydraulic Analysis)Operators are able to control SG level at approximately 50 percent with AFW flow until voidingin the RCS decreases to such a point that indicated pressurizer water level is restored. Corepeak exit fluid temperature remains well below 1200°F so that fuel integrity is not challenged.