NL-07-1532, Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems
| ML080590108 | |
| Person / Time | |
|---|---|
| Site: | Hatch  |
| Issue date: | 02/27/2008 |
| From: | Stinson L Southern Nuclear Operating Co |
| To: | Document Control Desk, Office of Nuclear Reactor Regulation |
| References | |
| NL-07-1532 | |
| Download: ML080590108 (19) | |
Text
L. M. Stinson (Mike) Southern Nuclear Vice President Operating Company, Inc.
Fleet Operations Support 40 Inverness Center Parkway Post Office Box 1295 Birmingham. Alabama 35201 Tel 205.992.5181 SOUTHE~A Fax 205.992.0341 COMPANY February 27,2008 Energy to Serve YtJur World'"
Docket Nos.: 50-321 NL-07-1532 50-366 U. S. Nuclear Regulatory Commission AnN: Document Control Desk Washington, D. C. 20555-0001 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems Ladies and Gentlemen:
On August 29, 2006 Southern Nuclear Operating Company (SNC) submitted a request to revise the Edwin I. Hatch Nuclear Plant (HNP) licensing/design basis with a full scope implementation of an alternative source term (AST). By letters dated November 6,2006, November 27,2006, January 30,2007, June 22, 2007, July 16, 2007, August 13, 2007, October 18, 2007, December 11, 2007, January 24,2008, February 4,2008, and February 25,2008 SNC has submitted further information to support the NRC review of the HNP AST submittal.
By letter dated April 26, 2007 the NRC requested additional information concerning the crediting in the AST analyses of: 1) the Units 1 and 2 turbine building ventilation exhaust systems with purging the area around the main control room following three of the four design basis accidents, and 2) the standby liquid control system to buffer the suppression pool, preventing iodine re evolution following a loss-of-coolant accident. The enclosure to this letter contains the SNC response to the referenced NRC request for additional information (RAI).
The 10 CFR 50.92 evaluation and the justification for the categorical exclusion from performing an environmental assessment that were included in the August 29, 2006 submittal continue to remain valid.
(Affirmation and signature are provided on the following page.)
U. S. Nuclear Regulatory Commission NL-07-1532 Page 2 Mr. L. M. Stinson states he is a Vice President of Southern Nuclear Operating Company, is authorized to execute this oath on behalf of Southern Nuclear Operating Company and to the best of his knowledge and belief, the facts set forth in this letter are true.
This letter contains no NRC commitments. If you have any questions, please advise.
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Respectfully submitted, SOUTHERN NUCLEAR OPERATING COMPANY xtM~
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Enclosure:
- 1. Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems cc: Southern Nuclear Operating Company Mr. J. T. Gasser, Executive Vice President Mr. D. R. Madison, Vice President - Hatch Mr. D. H. Jones, Vice President - Engineering RType: CHA02.004 U. S. Nuclear Regulatory Commission Mr. V. M. McCree, Acting Regional Administrator Mr. R. E. Martin, NRR Project Manager - Hatch Mr. J. A. Hickey, Senior Resident Inspector - Hatch State of Georgia Mr. N. Holcomb, Commissioner - Department of Natural Resources
Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Enclosure 1 Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems
Enclosure 1 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems TURBINE BUILDING VENTILATION (TB HVAC) QUESTIONS HNP has proposed to credit the TB HVAC system for dose mitigation by purging the area around the main control room beginning 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> following design basis accidents (DBAs). The TB HVAC system design was not previously reviewed for this safety function. Please respond to the following questions concerning the use of the TB HVAC system for dose mitigation:
NRC Question 1 Since the TB HVAC system is not classified as safety-related, please provide the information requested below to show that the TB HVAC system is comparable to a system classified as safety-related. If any item is answered in the negative, please explain why the TB HVAC system should be found acceptable for dose mitigation.
a) Are inservice inspection and inservice testing programs performed on the TB HVAC system in accordance with the American Society of Mechanical Engineers Boiler Pressure Vessel Code (ASME Code)?
b) Have you considered adding a Limiting Condition for Operation to the Technical Specifications for this system including surveillance requirements? What kind of testing and surveillance do you propose?
c) Is the TB HVAC system incorporated into the plants Maintenance Rule program consistent with Title 10 of the Code of Federal Regulations (10 CFR), Section 50.65, Requirements for monitoring the effectiveness of maintenance at nuclear power plants?
d) Does the TB HVAC system meet 10 CFR 50.49, Environmental qualification of electrical equipment important to safety for nuclear power plants, and General Design Criterion (GDC) 4, Environmental and dynamic effects design bases?
SNC Response a) Component classifications which dictate the scope of inservice testing (IST) requirements and inservice inspection (ISI) requirements, per 10 CFR 50.55a(f) and 10 CFR 50.55a(g) requirements respectively, were established for HNP consistent with regulatory guidance applicable at the time, such as Regulatory Guide (RG) 1.26 Revision 1, titled Quality Group Classifications and Standards for Water-, Steam-, and Radioactive-Waste-Containing Components of Nuclear Power Plants, for HNP Unit 2.
Consistent with the title of RG 1.26, and as illustrated in HNP Unit 2 FSAR table 3.9-10, titled Safety-Related Mechanical Components not covered by ASME Code, and the HNP Units 1 and 2 IST Program and ISI Program, NL-07-1532 E1-1 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems_____________
HVAC systems, such as the safety related standby gas treatment system, are not within the scope of IST and ISI since the process fluid is air, not water or steam.
The function of IST and ISI is to provide periodic continued assurance that a system continues to be able to perform its credited safety function by identifying any system degradation due to various wear mechanisms through the testing/inspection process. Given that the TB HVAC exhaust systems are credited to purge the area around the main control room (MCR) following three of the four HNP DBAs, specifically the loss-of-coolant accident (LOCA), main steam line break accident (MSLB), and control rod drop accident (CRDA), SNC has evaluated what monitoring, if any, is warranted for TB HVAC exhaust systems to demonstrate that they continue to be able to perform their credited purge function.
SNC intends to add the TB HVAC exhaust systems to the scope of the HNP Maintenance Rule program, in accordance with 10 CFR 50.65, and to the scope of license renewal, in accordance with 10 CFR 54.37(b). The crediting in the AST analyses of the TB HVAC exhaust systems post-accident to purge the area around the main control room brings these systems into the scope of both of these regulations. Inclusion in the scope of license renewal will result in periodic monitoring of the condition of the TB HVAC exhaust systems ductwork supports.
Beyond inclusion in the scope of the Maintenance Rule program and license renewal, SNCs evaluation indicates that minimal testing/inspection is warranted. This conclusion is based on the existence of minimal wear mechanisms and the TB HVAC exhaust systems required continuous operation during normal plant operation. Contrary to a system with water or steam as a process fluid, TB HVAC exhaust systems ductwork is subject to minimal wear. Adequacy of fan flow can be monitored from the MCR and is demonstrated by daily performance of TB HVAC exhaust systems design functions, such as removal of heat dissipated from plant equipment and air movement and filtering to control potential airborne radioactivity, by two of the available four fans on the two HNP units. Current TB HVAC exhaust fan flow rates provide sufficient margin to the AST credited flow rate for a single fan of 15,000 cfm beginning 9 hours1.041667e-4 days <br />0.0025 hours <br />1.488095e-5 weeks <br />3.4245e-6 months <br /> after the start of a DBA. Finally, since the TB HVAC filter units are not credited in the AST analyses, no filter testing is necessary to demonstrate filtration capabilities in support of AST DBA analyses. To assure there is no adverse impact on TB HVAC exhaust flow, filter train dP is monitored from the MCR.
Based on inclusion of the TB HVAC exhaust systems in the scope of the Maintenance Rule program and license renewal, SNC has concluded that sufficient assurance is provided that the TB HVAC exhaust systems will continue to be able to perform their credited purge function.
NL-07-1532 E1-2 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems_____________
b) After due consideration, SNC has concluded that the addition to HNP Technical Specifications (TS) of a Limiting Condition for Operation (LCO),
including surveillance requirements, to assure the lowest functional capability or performance levels, as stated in 10 CFR 50.36 titled Technical Specifications, is not warranted for the new credited function of the TB HVAC exhaust systems. Contrary to the vast majority of safety functions in the TS, the capability to perform the AST credited function of purging the turbine building is demonstrated continuously during HNP operation.
As described in section 2.7.3 of enclosure 1 to the AST submittal, the TB HVAC exhaust systems are important to operations and already designed for high reliability. Performance of TB HVAC exhaust system design functions, such as removal of heat dissipated from plant equipment, and air movement and filtering to control potential airborne radioactivity, are required on a continuous basis for normal plant operation. Consequently maintenance of the high reliability of the system is required for reliable plant operation.
In addition, as stated elsewhere in this response, SNC intends to add the TB HVAC exhaust systems to the scope of the HNP Maintenance Rule program, in accordance with 10 CFR 50.65, and to the scope of license renewal, in accordance with 10 CFR 54.37(b). The crediting in the AST analyses of the TB HVAC exhaust systems post-accident to purge the area around the main control room brings this system into the scope of both of these regulations. Based on such inclusion, further assurance is provided that the TB HVAC exhaust systems will remain capable of performing their credited accident function.
c) The TB HVAC exhaust systems are currently not incorporated into the HNP Maintenance Rule program. The TB HVAC exhaust systems will be added to and evaluated in the HNP Maintenance Rule program consistent with 10 CFR 50.65 to provide reasonable assurance that the systems will reliably perform their AST credited function of purging the area around the main control room following a LOCA, MSLB, and CRDA. The inclusion of TB HVAC exhaust systems in the HNP Maintenance Rule program will be complete in sufficient time to support final AST implementation once NRC approval is obtained.
d) With respect to the potential compliance of the TB HVAC exhaust systems with 10 CFR 50.49 and GDC 4, the environmental conditions for TB HVAC, with exception of the power supply, have been evaluated with respect to its AST credited safety function of purging the area around the MCR following a LOCA, MSLB, and CRDA. Regarding the MSLB, it should be noted that the credited purge function is only required for a main steam line break in the turbine building. Separate evaluations of a NL-07-1532 E1-3 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems_____________
MSLB in the reactor building steam chase, evaluated as a high energy line break, demonstrate that the TB HVAC purge function is not required to maintain MCR radiological doses within applicable regulatory limits.
With the exception of cable associated with the TB HVAC exhaust systems, those TB HVAC components located more than two feet from the TB HVAC charcoal filter beds are not subject to a harsh environment and therefore the requirements of 10 CFR 50.49 do not apply. More specific description of the subject environmental conditions follows on an HNP unit specific basis, as the TB HVAC system arrangements are somewhat different.
With respect to HNP Unit 1 TB HVAC environmental conditions, the electrical components associated with the TB HVAC exhaust system, with the exception of the power supply, are located outside the Unit 1 reactor building on a lower portion of the reactor building roof at elevation 185.
The ambient temperature, pressure and humidity for this location are not affected by a LOCA, MSLB or CRDA. Also, no steam is released in this area by any of these DBAs. The limiting radiation dose post-LOCA, comes from the TB HVAC charcoal filter beds. This dose drops to less than 1.0E+04 R at two feet from the face of the charcoal. Therefore, components located more than two feet from the TB HVAC charcoal filter beds are not subject to a harsh environment and the requirements of 10 CFR 50.49 do not apply.
With respect to HNP Unit 2 TB HVAC environmental conditions, the electrical components associated with the TB HVAC exhaust system, with the exception of the power supply, are located in the ventilation room on elevation 203 of the Unit 2 reactor building. The ambient pressure and humidity in the Unit 2 HVAC room are not affected by a LOCA, MSLB, or CRDA, nor is any steam released in this area by these DBAs. The temperature in the Unit 2 HVAC room can be expected to be below 150°F for LOCA, the limiting DBA for impact on temperature in this area. The limiting radiation dose post-LOCA is the same as that for Unit 1.
Therefore, components located more than two feet from the TB charcoal filter beds are not subject to a harsh environment and the requirements of 10 CFR 50.49 do not apply.
For both Units 1 and 2, the only TB HVAC components within two feet of the charcoal filter beds and subject to a radiation harsh environment are temperature switches which monitor charcoal bed temperature. SNC will take the necessary actions to assure these temperature switches meet the requirements of 10 CFR 50.49 in sufficient time to support final AST implementation once NRC approval is obtained With respect to cable, SNC has proposed a design modification for both units to provide the capability of supplying electrical power to the TB NL-07-1532 E1-4 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems_____________
HVAC exhaust systems from an emergency power source, reference SNC letter to the NRC dated October 18, 2007. Specifically, the modification will allow HNP Units 1 and 2 TB HVAC exhaust systems to be powered from a safety-related source via a manual switchover. Based on the availability of this alternate power source, SNC has not applied the requirements of 10 CFR 50.49 to the existing highly reliable normal power supply for the TB HVAC exhaust systems.
The TB HVAC exhaust systems power supply cable, extending from the interface between the safety-related essential power supply and the TB HVAC exhaust systems, specifically the electrical isolation circuit breaker, has been reviewed with respect to 10 CFR 50.49. Portions of the TB HVAC exhaust systems power supply cable will be replaced with cable that meets 10 CFR 50.49 requirements as part of the referenced modification committed to in the SNC letter to the NRC dated October 18, 2007. The routing of remaining cable, that will not be replaced, has been reviewed. Based on the cable routing review, that cable has been determined to not be subject to a harsh environment. Therefore, the requirements of 10 CFR 50.49 do not apply.
NL-07-1532 E1-5 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems_____________
NRC Question 2 Describe any changes to plant procedures that implement the dose mitigation function for the TB HVAC system and whether any training is necessary for plant personnel to implement the function.
SNC Response The planned changes to plant procedures that implement the dose mitigation function for the TB HVAC system and associated training for plant personnel are described in the responses to NRC Question 5 in the SNC letter to the NRC dated February 25, 2008 regarding human factors aspects of the AST submittal.
NL-07-1532 E1-6 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems_____________
NRC Question 3 The air for all TB HVAC dampers is supplied by interruptible service instrument air and failure of the air systems of both Units 1 and 2 would render both HVAC systems incapable of performing their required exhaust functions. In the event that pneumatic systems fail, have manual actions or overrides been developed to change the damper position?
SNC Response A system modification is being proposed, in accordance with AST submittal , Section 2.7.3.2. Specifically, the air supply for both units turbine building HVAC exhaust system dampers will be changed from interruptible instrument air to non-interruptible instrument air. This will ensure that a loss of air event will not prevent the turbine building HVAC exhaust systems from performing their credited function of purging the turbine buildings post-accident.
No manual actions or overrides will be required.
For more detail refer to the response to NRC Question 5.7 in the SNC letter to the NRC dated February 25, 2008 regarding human factors aspects of the AST submittal.
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STANDBY LIQUID CONTROL SYSTEM QUESTIONS Please respond to the following questions concerning the use of the SLC system for pH control of the suppression pool:
HNP has proposed to credit control of the pH in the suppression pool following a loss-of-coolant accident (LOCA) by means of injecting sodium pentaborate into the reactor core with the SLC system. The SLC system design was not previously reviewed for this safety function (pH control post-LOCA). Licensees proposing such credit need to demonstrate that the SLC system is capable of performing the pH control safety function assumed in the alternate source term (AST) LOCA dose analysis. The following questions are from a set of generic questions developed by the staff and are being provided to all boiling water reactor licensees with pending AST license amendment requests. In responding to questions regarding the SLC system, please focus on the proposed pH control safety function. The reactivity control safety function is not in question here. For example, the SLC system may be redundant with regard to the reactivity control safety function, but lack redundancy for the proposed pH control safety function.
If HNP believes that the information was previously submitted to support the license amendment request to implement AST, please refer to where that information may be found in the documentation.
NRC Question 1 Please identify whether the SLC system is classified as a safety-related system as defined in 10 CFR 50.2, Definitions, and whether the system satisfies the regulatory requirements for such systems. If the SLC system is not classified as safety-related, please provide the information requested in Items 1.1 to 1.5 below to show that the SLC system is comparable to a system classified as safety-related. If any item is answered in the negative, please explain why the SLC system should be found acceptable for pH control agent injection.
1.1 Is the SLC system provided with standby AC power supplemented by the emergency diesel generators?
1.2 Is the SLC system seismically qualified in accordance with Regulatory Guide (RG) 1.29, Seismic Design Classification and Appendix A to 10 CFR Part 100 (or equivalent used for original licensing)?
1.3 Is the SLC system incorporated into the plants ASME Code inservice inspection and inservice testing programs based upon the plants code of record (10 CFR 50.55a)?
1.4 Is the SLC system incorporated into the plants Maintenance Rule program consistent with 10 CFR 50.65?
NL-07-1532 E1-8 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems_____________
1.5 Does the SLC system meet 10 CFR 50.49 and Appendix A to 10 CFR Part 50 (GDC-4, or equivalent used for original licensing)?
SNC Response As stated in Enclosure 1 to the AST submittal, Section 2.7.2, the SLC system is considered a special safety system or safe shutdown system, and not an engineered safety feature (ESF) system. Therefore, the NRC review guideline, Guidance on the Assessment of a BWR SLC System for pH Control was used to evaluate the SLC system for its ability to perform its AST function of post-LOCA suppression pool pH control. The SLC system at HNP meets the following criteria:
1.1 The SLC system is required to be operable in the event of an offsite power failure. Therefore, the pumps, valves and controls are powered from the standby ac power supply. The pumps and valves are powered and controlled from separate buses and circuits so that a single active failure does not prevent system operation.
1.2 The SLC system process equipment, instrumentation, and controls essential for post-LOCA injection of sodium pentaborate (SPB) solution into the reactor is designed as Seismic Category I in accordance with Appendix A to 10 CFR 100 and Regulatory Guide 1.29 (August 1973).
1.3 The applicable components of the SLC system are inspected and tested in accordance with the HNP Unit 1 and Unit 2 Inservice Inspection Program and Inservice Testing Program as required by 10 CFR 50.55a.
1.4 The functions of the SLC system are evaluated in the HNP Maintenance Rule program consistent with 10 CFR 50.65 to provide reasonable assurance that the system will perform reliably.
1.5 This question is addressed in the AST submittal Enclosure 1, Section 2.7.2. The post-LOCA environment in which the SLC system would be required to operate has been determined to be a mild environment.
Cables associated with the SLC system were evaluated and determined to be environmentally qualified for the SLC post-LOCA mission.
Therefore, the SLC system meets the requirements of 10 CFR 50.49 and Appendix A to 10 CFR Part 50.
NL-07-1532 E1-9 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems_____________
NRC Question 2 Please describe proposed changes to plant procedures that implement SLC sodium pentaborate injection as a pH control additive. In addition, please address Items 2.1 to 2.5 below in your response. If any item is answered in the negative, please explain why the SLC system should be found acceptable for pH control additive injection.
2.1 Are the SLC injection steps part of a safety-related plant procedure?
2.2 Are the entry conditions for the SLC injection procedure steps symptoms of imminent or actual core damage?
2.3 Does the instrumentation cited in the procedure entry conditions meet the quality requirements for a Type E variable as defined in Tables 1 and 2 of RG 1.97 on accident monitoring instrumentation?
2.4 Have plant personnel received initial and periodic refresher training in the SLC injection procedure?
2.5 Have other plant procedures, (e.g., Emergency Response Guidelines) that call for termination of SLC as a reactivity control measure been appropriately revised to prevent blocking of SLC injection as a pH control measure? (For example, the override before Step RC/Q-1, If while executing the following steps: ....it has been determined that the reactor will remain shutdown under all conditions without boron, terminate boron injection and....)
SNC Response The proposed changes to plant procedures that implement SLC injection of SPB are described in the response to NRC Question 2 in the SNC letter to the NRC dated February 25, 2008 regarding human factors aspects of the AST submittal.
Sub-questions 2.1 through 2.5 are answered below.
2.1 Applicable procedures for the initiation of SLC injection post-LOCA will be revised and implemented during the AST implementation phase. The impacted procedures include the severe accident guidelines (SAGs),
abnormal operating procedures, system operating procedures, and annunciator response procedures. These procedures are considered safety related procedures in the context that they cover activities involving safety related structures, systems, and components. Plant programs are in place, such as procedures implementing 10 CFR 50.59 and the guidance of RG 1.33 revision 2, Quality Assurance Program Requirements (Operation), which assure safety related procedures remain consistent with the current licensing basis, including HNP design bases and applicable regulatory requirements.
NL-07-1532 E1-10 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems_____________
2.2 The entry conditions for SLC injection procedure steps are described in the response to NRC Question 2.2 in the SNC letter to the NRC dated February 25, 2008 regarding human factors aspects of the AST submittal.
Drywell radiation levels of 200,000 R/hr are indicative of actual core damage.
2.3 The quality requirements of instrumentation cited in the post-LOCA SLC injection procedure entry conditions are described in the response to NRC Question 1.1.3 in the SNC letter to the NRC dated February 25, 2008 regarding human factors aspects of the AST submittal.
2.4 Training of plant personnel in post-LOCA SLC injection is described in the response to NRC Question 2.3 in the SNC letter to the NRC dated February 25, 2008 regarding human factors aspects of the AST submittal.
2.5 The revision of other plant procedures that call for termination of SLC is described in the response to NRC Question 2.2 in the SNC letter to the NRC dated February 25, 2008 regarding human factors aspects of the AST submittal.
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NRC Question 3 Please show that the SLC system has suitable redundancy in components and features to assure that for onsite or offsite electric power operation its safety function of injecting sodium pentaborate for the purpose of suppression pool pH control can be accomplished assuming a single failure. For this purpose, the check valve is considered an active device since the check valve must open to inject sodium pentaborate. If the SLC system cannot be considered redundant with respect to its active components, the licensee should implement one of the three options described below, providing the information specified for that option for staff review.
3.1 Option 1 Show acceptable quality and reliability of the non-redundant active components and/or compensatory actions in the event of failure of the non-redundant active components. If you choose this option, please provide the following information to justify the lack of redundancy of active components in the SLC system:
3.1.1 Identify the non-redundant active components in the SLC system and provide their make, manufacturer, and model number.
3.1.2 Provide the design-basis conditions for the component and the environmental and seismic conditions under which the component may be required to operate during a design-basis accident. Environmental conditions include design-basis pressure, temperature, relative humidity and radiation fields.
3.1.3 Indicate whether the component was purchased in accordance with Appendix B to 10 CFR Part 50. If the component was not purchased in accordance with Appendix B, provide information on the quality standards under which it was purchased.
3.1.4 Provide the performance history of the component both at the licensees facility and in industry databases such as Equipment Performance and Information and Exchange System and Nuclear Plant Reliability Data System.
3.1.5 Provide a description of the components inspection and testing program, including standards, frequency, and acceptance criteria.
3.1.6 Indicate potential compensating actions that could be taken within an acceptable time period to address the failure of the component. An example of a compensating action might be the ability to jumper a switch in the control room to overcome its failure. In your response, please consider the availability of compensating actions and the likelihood of successful injection of the sodium pentaborate when non-redundant active components fail to perform their intended functions.
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3.2 Option 2 Provide for an alternative success path for injecting chemicals into the suppression pool. If you chose this option, please provide the following information:
4.2.1 Provide a description of the alternative injection path, its capabilities for performing the pH control function, and its quality characteristics.
42.2 Do the components which make up the alternative path meet the same quality characteristics required of the SLC system as described in Items 1.1 to 1.5, 2, and 3 above?
4.2.3 Does the alternate injection path require actions to be taken in areas outside the control room? How accessible will these areas be? What additional personnel would be required?
3.3 Option 3 Show that 10 CFR 50.67 dose criteria are met even if the pH is not controlled. If you chose this option, demonstrate through analyses that the projected accident doses will continue to meet the criteria of 10 CFR 50.67 assuming that the suppression pool pH is not controlled. The dissolution of cesium iodide (CsI) and its re-evolution from the suppression pool as elemental iodine must be evaluated by a suitably conservative methodology. The analysis of iodine speciation should be provided for staff review. The analysis documentation should include a detailed description and justification of the analysis assumptions, inputs, methods, and results. The resulting iodine speciation should be incorporated into the dose analyses. The calculation may take credit for the mitigating capabilities of other equipment, for example the standby gas treatment system, if such equipment would be available. A description of the dose analysis assumptions, inputs, methods, and results should be provided. Licensees proposing this approach should recognize that this option may incur longer staff review times and will likely involve fee-billable support from NRC staff contractor support.
SNC Response The redundancy of SLC components and features was discussed in Section 2.7.2 of Enclosure 1 of the AST submittal. The potential failure of two active components was discussed, namely the SLC initiation control switch and the check valves on the injection line. With the following response, SNC is supplementing the discussion in the AST submittal to demonstrate acceptable quality and reliability of the non-redundant active components and/or compensatory actions in the event of failure of the non-redundant active components (Option 1 of the question).
3.1.1 The non-redundant active components in the SLC system are (1) the two check valves located in series in the injection line for each unit and (2) the NL-07-1532 E1-13 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems_____________
SLC initiation control switch located on Unit 1 and Unit 2 panels 1H11-P603 and 2H11-P603, respectively, in the MCR. The make, manufacturer and model number for the check valves and the control switch are as follows:
Unit 1 Check Valves 1C41-F006 and 1C41-F007:
The Unit 1 injection line check valves are stainless steel Rockwell Edward 1-1/2 inch Piston Lift Check Valves, Figure No. 36274F316T1, mounted horizontally in the injection line.
Unit 2 Check Valves 2C41-F006 and 2C41-F007:
The Unit 2 injection line check valves are stainless steel Rockwell Edward 1-1/2 inch Piston Lift Check Valves, Figure No. 3674F316T, mounted horizontally in the injection line.
Unit 1 and Unit 2 SLC Initiation Control Switch:
The SLC system is actuated by a key-locked, three position switch. The switch is a General Electric (GE) Type SB-1 five-stage rotary cam-operated switch. The five individual stages are nested into each other on a common operating shaft with a common fixed contact support and front and rear support. The stack is tied together with two tie bolts threaded into the front support. Each stage has two contacts. The entire assembly is enclosed in a metal cover that provides protection for the contacts.
3.1.2 Environmental conditions under which the components may be required to operate during a design basis LOCA are described in the SNC response to NRC Question 1.5 (SLC Questions) in this letter. Note that the SNC response to NRC Question 1.5 (SLC Questions) also refers to the AST submittal Enclosure 1, Section 2.7.2.
Seismic design basis conditions for SLC components are described in the SNC response to NRC Question 1.2 (SLC Questions) in this letter.
The injection line check valves are designed to open against full reactor pressure. For the AST function, the system operating requirements are reduced since the reactor pressure associated with the AST function is much lower.
The SLC initiation control switch is located in the MCR which is an environmentally controlled facility and is continuously manned.
3.1.3 The HNP QA program provides control over activities affecting the quality of structures, systems, and components consistent with their importance to safety. As a control system providing an independent method of NL-07-1532 E1-14 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems_____________
reactivity control and for postulated ATWS events, the system is maintained within the requirements of the HNP 10 CFR 50, Appendix B program.
The SLC initiation control switch was procured as Class 1E and the injection line check valves were procured as Class 1.
3.1.4 A review of the HNP maintenance history for the SLC system did not discover any failures of the check valves to open or close or for the initiation control switch to fail to initiate a SLC subsystem.
A search of the Equipment Performance and Information Exchange System (EPIX) and Nuclear Plant Reliability Data System (NPRDS) databases found six failures for Rockwell Edward piston lift check valves.
Five were attributed to leak-by, normal wear, and deposits on the seat.
One failure was a failure to close. The one failure to close was on a different model from those used at HNP and was attributed to raised metal inside the valve body. It was determined to be a maintenance preventable functional failure and the incorrect valve for the application.
There were no fail-to-open failures found. The active function for the injection check valves for the AST mission is to open.
A search of the EPIX and NPRDS databases for GE SB-1 switches found 24 failures of various modes for that type switch. There were failures involving dirty or corroded contacts, loose parts, sticking and binding, interferences holding contacts open and normal age and wear.
Three of the 24 failures found were at HNP. The failures at HNP were attributed to (1) dirty contacts, (2) contacts out of adjustment, and (3) a loose cam shaft. None of the failures were with the SLC initiation switch.
As described in the SNC response to NRC Question 3.1.2 (SLC Questions) in this letter, the SLC initiation switch is located in the MCR, an environmentally controlled facility, which should reduce or eliminate the occurrence of contact corrosion.
3.1.5 As described in the SNC response to NRC Question 1.3 (SLC Questions) in this letter, the components of the SLC system are inspected and tested in accordance with the HNP Unit 1 and Unit 2 Inservice Inspection Program and Inservice Testing Program as required by 10 CFR 50.55a.
Means are provided by which the functional performance capability of the SLC system components can be verified periodically under conditions approaching actual use requirements. Demineralized water, rather than actual SPB solution, can be injected into the reactor to test the operation of all components of the SLC system.
NL-07-1532 E1-15 Edwin I. Hatch Nuclear Plant Request to Implement an Alternative Source Term Response to Request for Additional Information Regarding the Turbine Building Ventilation and Standby Liquid Control Systems_____________
SLC system functional testing is performed once per operating cycle, to verify flow through one SLC subsystem from pump to reactor pressure vessel. The functional test is on a staggered test basis and alternates each subsystem tested. During the functional test, operation of the control circuits, indicators, and the alarm annunciator are verified.
Flow rate and discharge pressure of the SLC pumps is verified once per quarter in accordance with the Inservice Testing Program. Leak rate testing to verify the integrity of the injection check valves is performed once per operating cycle per the Inservice Inspection Program. Continuity of the SLC explosive valves is verified monthly.
3.1.6 The check valves are considered highly reliable with regard to their required post-LOCA mission to open during SLC injection. No compensatory actions are considered necessary.
Compensating actions that could be taken within an acceptable time period to address the failure of the SLC initiation control switch are described in the response to NRC Question 2.1 of the SNC letter to the NRC dated February 25, 2008 regarding human factors aspects of the AST submittal.
NL-07-1532 E1-16