NOC-AE-14003134, Response to Request for Additional Information Regarding the License Amendment Request to the Fire Protection Program
| ML14142A016 | |
| Person / Time | |
|---|---|
| Site: | South Texas  |
| Issue date: | 05/12/2014 |
| From: | Gerry Powell 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 Company South Texas Propect Electric Generating Station P.. Box 289 Wdsworth. Txas 77483 May 12, 2014 NOC-AE-1 4003134 10 CFR 50.90 U.S. Nuclear Regulatory Commission Attention: Document Control Desk Washington, DC 20555-0001 South Texas Project Units 1 & 2 Docket Nos. STN 50-498, STN 50-499 STPNOC Response to Request for Additional Information Regarding the License Amendment Request to the Fire Protection Program TAC Nos. MF2477 and MF2478
References:
- 1. Letter from D.W. Rencurrel, STP Nuclear Operating Company, to NRC Document Control Desk, "License Amendment Request for Approval of a Revision to the South Texas Project Fire Protection Program Related to the Alternative Shutdown Capability," dated July 23, 2013. (NOC-AE-13002962)
- 2. E-mail from B. Singal, NRC, to L. Sterling, STP Nuclear Operating Company, "Request for Additional Information License Amendment Request Revision to the Fire Protection Program South Texas Project, Units 1 and 2", TACs MF2477 and MF2478, dated April 11, 2014. (AE-NOC-14002524)
On July 23, 2013, STP Nuclear Operating Company (STPNOC) submitted a license amendment request to revise the South Texas Project Units 1 and 2 Fire Protection Program related to alternate shutdown capability (Reference 1). In the event that a fire requires evacuation of the control room, the proposed amendment requested crediting the performance of certain operator actions, including one automatic operation, prior to evacuation.
By e-mail dated April 11, 2014 (Reference 2), the NRC requested additional information related to the STPNOC amendment request. Attachment 1 provides the STPNOC response to the Requests for Additional Information (RAI). Supplemental information that supports the RAI responses is provided in Attachment 2.
STI: 33874194
NOC-AE-14003134 Page 2 of 3 There 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 ___ __t_ 17, G.T. Powell Site Vice President rjg Attachments:
- 1. Request for Additional Information License Amendment Request Revision to the Fire Protection Program South Texas Project, Units 1 and 2
- 2. Request for Additional Information License Amendment Request Revision to the Fire Protection Program South Texas Project, Units 1 and 2 Application Revisions
NOC-AE-1 4003134 Page 3 of 3 cc:
(paper copy) (electronic copy)
Regional Administrator, Region IV A. H. Gutterman, Esquire U. S. Nuclear Regulatory Commission Morgan, Lewis & Bockius LLP 1600 East Lamar Boulevard Arlington, TX 76011-4511 Balwant K. Singal U. S. Nuclear Regulatory Commission Balwant K. Singal John Ragan Senior Project Manager Chris O'Hara U.S. Nuclear Regulatory Commission Jim von Suskil One White Flint North (MS 8 B1) NRG South Texas LP 11555 Rockville Pike Rockville, MD 20852 NRC Resident Inspector Kevin Polio U. S. Nuclear Regulatory Commission Cris Eugster P. O. Box 289, Mail Code: MN116 L. D. Blaylock Wadsworth, TX 77483 City Public Service Jim Collins Peter Nemeth City of Austin Crain Caton & James, P.C.
Electric Utility Department 721 Barton Springs Road C. Mele Austin, TX 78704 City of Austin Richard A. Ratliff Robert Free Texas Department of State Health Services
Attachment 1 NOC-AE-14003134 ATTACHMENT 1 Request for Additional Information License Amendment Request Revision to the Fire Protection Program South Texas Project, Units 1 and 2
Attachment 1 NOC-AE-14003134 Page 1 of 7 REQUEST FOR ADDITIONAL INFORMATION LICENSE AMENDMENT REQUEST REVISION TO THE FIRE PROTECTION PROGRAM SOUTH TEXAS PROJECT, UNITS 1 AND 2 By 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 their commitment to certain technical requirements of Title 10 of the Code of FederalRegulations (10 CFR) Part 50, Appendix R, Section Ill.L, as documented in the STP Fire Hazards Analysis Report, for crediting the performance of certain operator actions in the control room in the event that a fire necessitates the evacuation of the control room.
The U.S. Nuclear Regulatory Commission (NRC) staff has reviewed the information provided by the licensee and determined that the following additional information is needed to complete the review.
Request for Additional Information (RAI)
RAI-01 Physical Separation Section 3.5 of Enclosure 1 to the request refers to physical and flame retardant barriers and thermal insulating material installed between redundant devices but does not specify whether a particular assembly is utilized for this purpose and whether it carries any classification or rating by a recognized testing laboratory.
Please state what materials or assemblies are used to accomplish the physical separation noted in Section 3.5 and provide any applicable design or testing certifications for their use in the noted applications.
RAI-02 Transfer of Control Section 3.7.4 of Enclosure 1 to the request states that the required actions are backed up from outside the control room within a short period of time but does not specify what that duration is and whether the operator manual actions that are performed outside the control room have been evaluated for feasibility and reliability, e.g., per NUREG-1 852 "Demonstrating the Feasibility 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 room actions at the alternate location and provide a technical basis for the assumed time, including a discussion of feasibility and reliability, to perform the operator manual actions.
RAI-03 Typo in Description of Limiting Event There appears to be a typo in the description of the Case lb results in Section 3.8.4 of . The licensee stated that "Core peak exit fluid temperature remains well below approaches 1200°F so that fuel integrity is not challenged," but it is not clear whether core peak exit fluid temperature remains well below 1200TF or approaches 1200 0 F. Please clarify the statement noted above.
Attachment 1 NOC-AE-14003134 Page 2 of 7 RAI-04 Fire Model Analysis Section A3.2.2 of Enclosure 1 states that smoke detectors are present in each cabinet adjacent to the exhaust ventilation duct but it is not clear whether these are the same fire detectors noted in Section 3.3. Section A3.2.2 also states that the automatic detection system does not isolate ventilation upon actuation.
RAI-04.1 Please clarify what type of detectors are located in the control cabinets and provide a technical justification for why receipt of a detection alarm signal does not prompt isolation of the ventilation system as to not propagate products of combustion across fire areas or zone boundaries, e.g. from outside the control room fire area or the relay room fire zone.
Table A3.1 provides the cable acceptance criteria used in the fire modeling analysis but does not include any tenability criteria for operators.
RAI-04.2 Please clarify whether the licensee evaluated any tenability criteria to understand whether the control room remains habitable during the postulated fire scenarios and provide a technical justification for any assumptions related to main control room habitability made during the analysis. If tenability was evaluated, provide the criteria used to do so and state whether an evacuation due to a loss of tenability would occur for the postulated fire scenarios.
Section A3.2.4 describes the ignition sources and fire size assumed for the analysis but does not state what material or fuel properties were used in the analysis.
RAI-04.3 Please describe the material properties of the combustibles that were modeled and the material properties used in the model. If there were differences between the installed and modeled material properties provide a technical basis that justifies how the modeled material properties are bounding.
Section A3.3 states that ignition of secondary combustibles around CP001 was assumed not to occur but does not state why this was assumed or whether it was based on modeling results.
Attachment 1 NOC-AE-14003134 Page 3 of 7 RAI-04.4 Please provide a technical justification for the assumption that secondary combustibles are assumed not to ignite.
Section A3.4.1 makes reference to an ambient heat flux and depicts graphs of certain criteria over time but does not explain what is intended by this term or where the measurements were recorded within the model domain.
RAI-04.5 Please explain what is intended by the term ambient heat flux and why Figure A3.3 appears 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 stated values for heat flux and temperature and provide a technical justification as to why the data collection locations are considered bounding.
Attachment 1 NOC-AE-14003134 Page 4 of 7 NRC Request for Additional Information (RAI)
NRC Request - RAI-01 Physical Separation Section 3.5 of Enclosure 1 to the request refers to physical and flame retardant barriers and thermal insulating material installed between redundant devices but does not specify whether a particular assembly is utilized for this purpose and whether it carries any classification or rating by a recognized testing laboratory.
Please state what materials or assemblies are used to accomplish the physical separation noted in Section 3.5 and provide any applicable design or testing certifications for their use in the noted applications.
STPNOC Response:
Section 3.5 discusses the separation criteria used at STP between the turbine trip circuit (non-class 1E circuit) and the reactor trip circuitry. The thermal barrier discussed in section 3.5 is Siltemp and tested by Wyle Laboratories for faulted circuits conditions as described in Section 5.6 of IEEE 384 and NRC Regulation Guide 1.75 and carries no rated hourly classification. As described in section 3.5, once the reactor trip signal is actuated, an automatic turbine trip signal is generated in each of two solid state protection system (SSPS) logic and actuation trains located outside of the Main Control Room (MCR) as shown in Figure 4 in Enclosure 1. The manual turbine trip circuitry is located 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 a reactor trip and turbine trip are generated simultaneously in the SSPS cabinets.
NRC Request - RAI-02 Transfer of Control Section 3.7.4 of Enclosure 1 to the request states that the required actions are backed up from outside the control room within a short period of time but does not specify what that duration is and whether the operator manual actions that are performed outside the control room have been evaluated for feasibility and reliability, e.g., per NUREG-1 852 "Demonstrating the Feasibility 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 room actions at the alternate location and provide a technical basis for the assumed time, including a discussion 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 Reactor Coolant Pump 13.8 kV breakers which will be opened within 20 minutes. The 10 minute limit was used in the original Westinghouse Safe Shutdown calculations and has been verified in the STP thermal hydraulic calculation. The Control Room Evacuation Procedure has been walked down and verified that the time of 10 minutes or less is achievable. 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 Fire Area at STP. This evaluation also includes a manual action feasibility checklist for each manual action identified, taking into consideration the methodology detailed in the NRC NUREG-1852.
Attachment 1 NOC-AE-14003134 Page 5 of 7 NRC Request - RAI-03 Typo in Description of Limiting Event There appears to be a typo in the description of the Case lb results in Section 3.8.4 of . The licensee stated that "Core peak exit fluid temperature remains well below approaches 1200°F so that fuel integrity is not challenged," but it is not clear whether core peak exit fluid temperature remains well below 1200TF or approaches 12000 F. Please clarify the statement noted above.
STPNOC Response:
Operators are able to control SG level at approximately 50 percent with AFW flow until voiding in the RCS decreases to such a point that indicated pressurizer water level is restored. Core peak exit fluid temperature remains well below 1200°F so that fuel integrity is not challenged.
NRC Request - RAI-04. Fire Model Analysis Section A3.2.2 of Enclosure 1 states that smoke detectors are present in each cabinet adjacent to the exhaust ventilation duct but it is not clear whether these are the same fire detectors noted in Section 3.3. Section A3.2.2 also states that the automatic detection system does not isolate ventilation upon actuation.
NRC Request - RAI-04.1 Please clarify what type of detectors are located in the control cabinets and provide a technical justification for why receipt of a detection alarm signal does not prompt isolation of the ventilation system as to not propagate products of combustion across fire areas or zone boundaries, e.g. from outside the control room fire area or the relay room fire zone.
STPNOC Response:
STP Main Control Room has ionization detectors below and above the suspended ceiling and in the MCR cabinets to provide early warning. These detectors alarm in the local panel and the room itself. The detectors are only specified as smoke detectors in the report. Only a qualitative discussion of the detection is required because detection is not credited in the fire model in any way. The discussion of the detection is only made to present defense-in-depth. In addition, there is no automatic interlock between the MCR detection system and the MCR cabinet exhaust ventilation. STP does have smoke detectors in the intake ductwork that auto actuate a smoke damper in the inlet ductwork and keeps smoke from entering the MCR. The outlet ductwork has smoke detectors for indication only. Procedures are in place so the control room staff can isolate the outlet ductwork and manually enter into a smoke purge mode of operation if necessary.
Attachment 1 NOC-AE-14003134 Page 6 of 7 Table A3.1 provides the cable acceptance criteria used in the fire modeling analysis but does not include any tenability criteria for operators.
NRC Request - RAI-04.2 Please clarify whether the licensee evaluated any tenability criteria to understand whether the control room remains habitable during the postulated fire scenarios and provide a technical justification for any assumptions related to main control room habitability made during the analysis. If tenability was evaluated, provide the criteria used to do so and state whether an evacuation due to a loss of tenability would occur for the 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 the compartment representing the MCR as a whole are extremely conservative because no ventilation out of the compartment was modeled. Even with this conservatism no hot gas layer is formed. As discussed in the report the majority of the MCR is expected to remain at near ambient conditions.
Section A3.2.4 describes the ignition sources and fire size assumed for the analysis but does not state what material or fuel properties were used in the analysis.
NRC Request - RAI-04.3 Please describe the material properties of the combustibles that were modeled and the material properties used in the model. If there were differences between the installed and modeled material properties provide a technical basis that justifies how the modeled material properties are bounding.
STPNOC Response:
Based on the walkdown performed in the MCR, the bounding combustibles were determined to be cable insulation. Furthermore, the greatest concentration of the cable insulation is in the MCR cabinets. As a result, the MCR cabinets were chosen as the bounding combustible material. Table G-1 of NUREG 6850 Vol. 2 provides recommended Heat Release Rate (HRR) values for electrical fires. The most conservative (98th percentile) HRR for the cabinet type that most closely fits the design of the MCR cabinets was used. A HRR curve was then generated from the peak value in accordance with Section 3.1.1 of NUREG 1934. This HRR curve was the input into the CFAST model. It represents the most conservative HRR curve expected based on the combustible loading within the MCR.
Attachment 1 NOC-AE-1 4003134 Page 7 of 7 Section A3.3 states that ignition of secondary combustibles around CP001 was assumed not to occur but does not state why this was assumed or whether it was based on modeling results.
NRC Request - RAI-04.4 Please provide a technical justification for the assumption that secondary combustibles are assumed not to ignite.
STPNOC Response:
Based on the walkdown performed in the MCR, there are no secondary combustibles immediately around the MCR cabinets. Transient combustibles in the MCR are strictly managed per station procedure (i.e. Control of Transient Fire Loads and Use of Combustible and Flammable Liquids and Gases), so no transient combustibles were required to be considered. The MCR cabinets are constructed with double walls without an air gap with ventilation in each cabinet. Based on this configuration and in accordance with the guidance in Appendix S of NUREG 6850 propagation between cabinets is not required to be assumed.
Section A3.4.1 makes reference to an ambient heat flux and depicts graphs of certain criteria over time but does not explain what is intended by this term or where the measurements were recorded within the model domain.
NRC Request - RAI-04.5 Please explain what is intended by the term ambient heat flux and why Figure A3.3 appears 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 stated values for heat flux and temperature and provide a technical justification as to why the data collection locations are considered bounding.
STPNOC Response:
The thermoset cable acceptance criteria in Table 8-2 of NUREG 6850 Vol. 2 are given in both temperature and heat flux. Because CFAST calculates parameters on a per compartment basis, the ambient heat flux represents the heat flux that may be seen anywhere throughout the compartment. The fact that the acceptance criteria are exceeded 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, this is acceptable.
Attachment 2 NOC-AE-14003134 ATTACHMENT 2 Request for Additional Information License Amendment Request Revision to the Fire Protection Program South Texas Project, Units I and 2 Application Revisions
Attachment 2 NOC-AE-14003134 Page 1 of 1 Before:
(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 voiding in the RCS decreases to such a point that indicated pressurizer water level is restored. Core peak exit fluid temperature remains well below approaches 1200°F so that fuel integrity is not challenged.
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 voiding in the RCS decreases to such a point that indicated pressurizer water level is restored. Core peak exit fluid temperature remains well below 1200°F so that fuel integrity is not challenged.