Text

Response to Request for Additional Information for Overall Integrated Plan in Response to 03/12/2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design Basis.
	ML13206A006
Person / Time
Site:	Palo Verde
Issue date:	07/18/2013
From:	Mims D; Arizona Public Service Co
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	102-06733-DCM/DFH, EA-12-049
	Download: ML13206A006 (92)
	v • d • e

T _ -

EA-12-049 DWIGHT C. MIMS t+aps Senior Vice President, Nuclear Regulatory & Oversight Palo Verde Nuclear Generating Station P.O. Box 52034 Phoenix, AZ 85072 Mail Station 7605 102-06733-DCM/DFH Tel 623 393 5403 July 18, 2013 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk 11555 Rockville Pike Rockville, MD 20852

References:

1. NRC Order Number EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events, dated March 12, 2012

2. APS Letter 102-06670, APS Overall Integrated Plan in Response to March 12, 2012 Commission OrderModifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049), dated February 28, 2013

3. NRC to APS Letter (ML13131A259, Palo Verde Nuclear Generating Station, Units 1, 2, and 3 - Request for Additional Information Regarding Overall Integrated Plan in Response to Commission Order EA-12-049 Modifying License with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (TAC NOS. MF0829. MF0830. and MF0831), dated June 20, 2013

Dear Sirs:

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Units 1, 2, and 3, Docket Nos. STN 50-528, 50-529, and 50-530, Response to Request for Additional Information for the PVNGS Overall Integrated Plan in Response to the March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049)

On March 12, 2012, the Nuclear Regulatory Commission (NRC) issued an order (Reference 1) to Arizona Public Service Company (APS). Reference 1 was immediately effective and directed APS to develop, implement, and maintain guidance and strategies to maintain or restore core cooling, containment, and spent fuel pool cooling capabilities in the event of a beyond-design-basis external event.

A member of the STARS (Strategic Teaming and Resource Sharing) Alliance Callaway-Comanche Peak-Diablo Canyon-Palo Verde-San OnofreSouth Texas-Wolf Creek

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ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ATTN: Document Control Desk U.S. Nuclear Regulatory Commission, Region IV Response to Request for Additional Information Page 2 Per Section IV, Condition C.1 of Reference 1, on February 28, 2013, APS submitted the PVNGS overall integrated plan (OIP) for mitigating strategies to the NRC (Reference 2).

By email dated May 17, 2013, the NRC provided a draft request for additional information (RAI) to APS regarding the integrated plan associated with Order Number EA-12-049. The NRC requested a response to the RAI within 30 days of receipt of the email in order to support their review schedule for the integrated plans. On May 30 and June 6, 2013, APS participated in publically available conference calls with the NRC to ensure there was a common understanding of the RAI. On June 20, 2013, in a letter to APS, the NRC submitted the RAI (Reference 3) and in a subsequent conversation with the NRC project manager for PVNGS, the NRC agreed to extend the due date for the response to the RAI to July 18, 2013.

The responses developed by APS were reviewed by the Nuclear Energy Institute (NEI) FLEX Task Force Industry Group. Eleven responses were identified as generic industry topics regarding Order Number EA-12-049. The nuclear industry will work on these responses generically through NEI and the applicable industry groups. NEI will coordinate the schedule for resolution with the NRC.

The responses to the NRC questions are provided in the enclosure to this letter.

Responses containing proprietary or security-related information are provided in separate attachments to the enclosure.

No commitments are being made to the NRC by this letter.

Should you have any questions concerning the content of this letter, please contact PVNGS Operations Support Manager, Regulatory Affairs, Mark McGhee, at (623) 393-4972.

I declare under penalty of perjury that the foregoing is true and correct.

Executed on q11_/_/ _

(Date)

Sincerely, Enclosure - APS RESPONSE TO THE RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, "MITIGATING STRATEGIES FOR BEYOND DESIGN BASIS EXTERNAL EVENTS" ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ATTN: Document Control Desk U.S. Nuclear Regulatory Commission, Region IV Response to Request for Additional Information Page 3 DCM/DFH/hsc cc: E. J. Leeds, NRC Director Office of Nuclear Reactor Regulation A. T. Howell III NRC Region IV Regional Administrator J. K. Rankin NRC NRR Project Manager J. P. Reynoso NRC Acting Senior Resident Inspector for PVNGS J. A. Kratchman NRR/JLD/PMB, NRC E. E. Bowman NRR/DPR/PGCB, NRC ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO REQUEST FOR ADDITIONAL INFORMATION (RAI)

REGARDING THE PVNGS OVERALL INTEGRATED PLAN (OIP) FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BEYOND DESIGN BASIS EXTERNAL EVENTS (BDBEE)

This Enclosure includes the following attachments:

ATTACHMENT 1 - ACRONYMS ATTACHMENT 2 - REFERENCES ATTACHMENT 3 - ESSENTIAL LOAD LIST WITH CRITICAL SAFETY FUNCTION (FROM ENGINEERING STUDY 13-NS-A108, APPENDIX E)

ATTACHMENT 4 - SECURITY-RELATED RESPONSES TO RAI ATTACHMENT 5 - PROPRIETARY-RELATED RESPONSES TO RAI ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE Request for Additional Information Regarding Palo Verde Generating Station Overall Integrated Plan in Response to Order EA-12-049 049-RAI-Palo Verde-1 Please identify any license amendment requests that are necessary for modifications proposed in the integratedplan.

APS Response:

Currently, no required license amendment requests (LAR) have been identified. LARs meeting the criterion of the RAI may be identified later in the design development process.

APS anticipates submitting this information as a part of a periodic six-month update to the OIP.

1 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-2 Attachment 1A of the APS Integrated Plan dated February28, 2013, lists the operator actions and associatedcompletion times to mitigate the consequences of an extended loss of AC [alternatingcurrent] power (ELAP).

Discuss how the plant-specific guidance and strategies and the associatedadministrative controls and training program will be developed and implemented to assure that the requiredoperator actions are consistent with that assumed in the CENTS [Combustion Engineering Nuclear Transient Simulator] analysis and can be reasonablyachievable within the required completion times.

APS Response:

APS is developing a FLEX Support Guideline (FSG): 791S-9ZZ02, PVNGS Extended Loss of AC Power (Reference 6). The operator actions identified in the FSG are based on the results of the CENTS analysis (Reference 5 of the PVNGS Overall Integrated Plan (OIP) February 28, 2013, submittal). APS will develop administrative control programs and training plans consistent with the guidance in NEI 12-06, Section 2.4, to implement and maintain the FSG.

Implementation of these programs will be consistent with existing PVNGS programmatic controls. Verification of output documents is an integral part of these processes. APS will provide to the NRC a description of the beyond-design-bases program, administrative controls, and training program as a part of a periodic six-month update to the OIP.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-3 Pages 18 and 19 of the APS Integrated Plan dated February28, 2013, state, in part, that:

Table Item 9 - Open Control Room Doors: Block open doors to provide ventilation to maintain control room temperature. Reference 7,Section IX.3 provides a list of rooms reviewed (including the control room) and predicted temperatures. Because load shed is to be completed within 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months , heat loads in the control room are minimal (only essential identified instrumentationis powered). It is predicted that long term control room temperature would approach outside air temperature, per design. The PVNGS FSG [FLEX Support Guideline] (Reference 13) will also include steps to open control room doors.

Section 9.2 of Nuclear Energy Institute (NEI) 12-06, Revision 0, "Diverse and Flexible Coping Strategies (FLEX) Implementation Guide" August 2012 (ADAMS Accession No. ML12242A378), states, in part, that Virtually every state in the lower 48 contiguous United States has experienced temperaturesin excess of 110 0 F [degrees Fahrenheit].

Many states have experienced temperaturesin excess of 120 0 F.

Pages 51 and 52 of the APS Integrated Plan dated February28, 2013, state that ventilation is not required in Phase 1 and it will not be recovered until Phase 2 (approximately28 hours after the ELAP).

a. Has a plant-specific, thermal hydraulic calculation been performed to determine what the maximum control room temperature would be based on the NEI 12-06 conditions? If so, please provide a summary of the calculation and its results concluding that control room habitabilitylimits will be maintainedin all Phases of the ELAP event. If not, please provide the basis andjustification for concluding that main control room ventilation will not be required to maintain habitability limits until Phase 2 (28 hour3.240741e-4 days 0.00778 hours 4.62963e-5 weeks 1.0654e-5 months mark) of the ELAP event.

APS Response:

No analysis has been performed for the control room envelope (CRE) since an engineered solution could not be implemented early in this event. The statement on pages 50 and 52 should have indicated that ventilation is "not available" rather than "not required." The statements made on pages 18 and 19 of our submittal are based on the Palo Verde Nuclear Generating Station (PVNGS) Station-Blackout (SBO) analysis and conservative engineering judgment. Control room temperature during normal operation, with outside temperature at 113 0 F and full operator and staff complement, is maintained less than 75 0 F by design (American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE)

Weather Station Data, Luke AFB/Phoenix, AZ, USA, WMO#722785, 2009 ASHRAE Handbook

- Fundamentals - Reference 1). The environmental condition inside the control room during an ELAP is similar to that for an SBO for the first hour of the event. During this time period, the control room SBO analysis assumes a full complement of staff and actuation of most 3

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE indicators and alarms in the control room with no functional essential ventilation. The predicted temperature at one hour has been calculated to remain below 110 0 F. The prediction of ELAP control room temperature after entry into the FSG was based on three assumptions:

1. If the CRE is maintained, room temperature will increase due to heat loads from emergency lighting, plant instrumentation, and the control room staff.

2. The heat load in the room is reduced after the first hour of the event since the amount of energized instrumentation is reduced to one channel, and one train of emergency lighting will be turned off.

3. Notwithstanding items 1 and 2, room temperature will increase at a constant rate as result of fixed heat load and limited heat losses through the walls and floor.

Therefore, sometime after the event, control room temperature could possibly exceed the outside environmental condition. Any time sensitive action will depend on the outside air temperature (OSA). The cooler the OSA, the sooner the control room doors could be opened. If the OSA temperature is hotter than the control room, the control room should be kept isolated. In either case, the CRE will approach and possibly exceed the outside temperature if doors are not opened.

Therefore, because of the conditions experienced during an ELAP event, no control room ventilation is available. The two hour action statement to open the control room doors, as identified in Attachment A of the OIP, is reasonable based on engineering judgment and NEI 12-06, section 3.2.1.7(1). In conclusion, a course of action will be established in the FSG for responding to a beyond design-basis event. The FSGs will contain directions for operating crews to open the CRE prudently for the best possible outcome.

b. NEI 12-06 relies on the guidance from NUMARC 87-00, Revision 1, "Guidelines and Technical Basis for NUMARC Initiatives AddreSSing station Blackout at Light Water Reactors,"August 1991 (ADAMS Legacy Accession No. 9209020287), for a 110OF limit for efficient human performance. NUMARC 87-00 provides the technical basis for this habitability standardas MIL-STD-1472C, which concludes that 110OF is tolerable for light work for a 4 hour4.62963e-5 days 0.00111 hours 6.613757e-6 weeks 1.522e-6 months period while dressed in conventional clothing with a relative humidity of ,30%. In light of this technical basis, please provide justification for the long term habitabilityof the main control room and/or please indicate what additionalrelief efforts for the main control room staff will be provided (e.g., short stay time cycles, use of ice vests/packs, supplies of bottled water, etc.).

APS Response:

Long term habitability will be assured by monitoring control room conditions, heat stress countermeasures, and rotation of personnel to the extent feasible. PVNGS procedure 01DP-0IS17, "Heat Stress Prevention Program," outlines the issues and the actions to take when working in a higher temperature environment and provides various measures to mitigate the effects of working in elevated temperatures for extended periods.

4 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE Control room staff will be trained on the expected conditions, the need for self and team monitoring, and the countermeasures available. The staffing analysis will address availability of replacement personnel, both long term and in the event of medical emergency.

Additionally, the FSG provides guidance for control room staff to evaluate the control room temperature and take actions as necessary. The initial action would be to open doors to the outside to obtain the benefit of the external weather conditions in limiting the control room temperature. Additional measures to manage the effects of high temperature on personnel include personnel rotation, use of cooling blankets, and the availability of drinking water.

c. Please clarify the number of plant personnel assumed to be present in the control room for this analysis relative to the number of personnel that may be present during an ELAP event.

APS Response:

As stated in the APS response to 049-RAI-Palo Verde-3a, no specific analysis for ELAP was performed.

d. Please discuss the postulated outside air temperature.

APS Response:

As stated in the APS response to 049-RAI-Palo Verde-3a, no specific analysis for ELAP was performed. However, the temperature profile based from the American Society of Heating, Refrigerating, and Air-Conditioning Engineers (ASHRAE) June weather station data for Phoenix, Arizona, shows a daily adjusted maximum temperature of 113°F and is consistent with the plant design bases. Although higher temperatures have been observed for short durations, it is concluded that higher peak temperatures would only occur for short durations.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-4 Page 24 of the APS IntegratedPlan dated February28, 2013, states that one train of atmospheric dump valves (ADV) solenoids will be de-energized during load shed. Please explain the necessity or prudence of this action and clarify the time requiredto restore power to the de-energized train if it becomes necessary.

APS Response:

The Atmospheric Dump Valves (ADV) are described in Section 10.1 of the PVNGS UFSAR.

One train of ADV solenoids is deenergized to reduce battery load and extend the availability of the Class 1E Batteries. Deenergizing one train of ADV solenoids is acceptable because only one ADV is required to remove the expected decay heat and perform a plant cooldown as directed by the FSG. Each ADV is sized to hold the plant at hot standby while dissipating core decay heat or to allow a sufficient flow of steam to maintain a controlled reactor cooldown rate. Palo Verde's strategy is to use one ADV per Steam Generator (SG) to perform a symmetrical natural circulation cooldown of the Reactor Coolant System (RCS).

If it should become necessary to restore power to the deenergized ADV train, the power supply breakers that were opened during the DC load-shed activities can be closed in less than twenty minutes. However, based on NEI 12-06, Section 3.2.1.3, "Initial Conditions" guidance, this should not be necessary as no additional failures are assumed.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-5 Page 15 of the APS Integrated Plan dated February28, 2013, states Instrumentation on FLEX equipment will be used to confirm adequate performance of equipment functions.

Please describe the instrumentation that will be used to monitor portable/FLEXelectrical power equipment including their associated measurement tolerances/accuracyto ensure the electrical equipment remains protected (from an electrical power standpoint,e.g.,

power fluctuations) and the operatoris provided with accurate information to maintain core cooling, containment, and spent fuel cooling.

APS Response:

APS will address instrumentation to monitor portable FLEX electrical power equipment and provide a response to this RAI during the design and procedure development phase. Safety functions such as core, containment, and spent fuel cooling and inventory control will be monitored from the unit's control room using seismically qualified, class instrumentation.

Each control room will have the capability of communicating with temporary equipment operators to operate FLEX equipment within the needed range of the safety parameter of interest. APS anticipates providing this information and FLEX portable instrumentation capabilities as a part of a periodic six-month update to the OIP.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-6 Page 18 of the APS Integrated Plan dated February28, 2013, states the following:

Table Item 7 - Complete DC [direct current] Load Shed: DC load shed must be completed within 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months in order to achieve a battery coping time of 47 hours5.439815e-4 days 0.0131 hours 7.771164e-5 weeks 1.78835e-5 months on battery bank B (Reference 16, Section 8.6). For Phase 1, PVNGS can cope on the installed DC batteries for up to 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months with no load shedding. If load shedding, as described in PVNGS Study 13-NS-A108 (Reference 7), is completed, the battery coping period is extended to 47 hours5.439815e-4 days 0.0131 hours 7.771164e-5 weeks 1.78835e-5 months . This load shed strategy will preserve station batteries and provide additionaltime prior to needing to re-energize battery chargers.

a. Provide the DC load profile for the mitigating strategies to maintain core cooling.

APS Response:

The referenced battery study is an engineering best estimate based on the published capacity rate of the GNB NCN-33 batteries, which is 12 hours1.388889e-4 days 0.00333 hours 1.984127e-5 weeks 4.566e-6 months to 1.78 VDC. APS plans to revise this analysis as this effort evolves and is updating the battery analysis to include more specific information as requested in this RAI. The revised analysis will be completed by February 28, 2014.

The load profile for the Train B Battery, which has the most limiting load profile, was used for the OIP and is summarized below:

181 amps for the first 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months

61.3 amps from 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months to 39 hours4.513889e-4 days 0.0108 hours 6.448413e-5 weeks 1.48395e-5 months , as identified in Attachment 1A of the OIP

From 39 hours4.513889e-4 days 0.0108 hours 6.448413e-5 weeks 1.48395e-5 months to the end of the event, batteries will be charged by 480V FLEX protable generators during Phase 2 Operations.

b. Provide a detailed discussion on the loads that will be shed from the DC bus, the equipment location (or location where the requiredaction needs to be taken),

and the required operatoractions needed to be performed and the time to complete each action. In your response, explain which functions are lost as a result of shedding each load and discuss any impact on defense in depth and redundancy.

APS Response:

Included as Attachment 3 are tables of the "Essential Load List with Critical Safety Function." The DC loads section of this list shows the loads that will be shed, the loads that will remain energized, and the critical safety function of each load that remains energized.

Equipment location where action is taken o 100 foot elevation of the Control Building 8

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE o 100 foot elevation of the Auxiliary Building o 120 foot elevation of the Auxiliary Building Required operator actions o verify breakers closed o open breakers

The time to complete each action 0 During a walkdown performed by auxiliary operators in June 2013, actions associated with the complete DC load shed were completed within 60 minutes The tables in Attachment 3 identify loads that remain energized and their safety functions. No credited safety functions are lost as a result of the DC load shed.

To meet the objectives of the FLEX strategies, it is necessary to reduce energized DC loads to one train of equipment. This approach is consistent with the guidance of NEI 12-06 which does not require defense in depth and redundancy. With the selected loads of one train energized, necessary instrumentation and equipment needed to monitor the plant and mitigate the event is available.

i. Are there any plant components that will change state if vital alternating current (AC) or DC is lost, de-energized, during this evolution of DC load shed? When the operators manipulate DC breakers to load shed, will plant components actuate, de-energize pumps, etc. ? The staff is particularlyinterested that a safety hazard is not created, such as de-energizing the DC powered seal oil pump for the main generator, which would allow the hydrogen to escape to the atmosphere. This may cause an explosion or fire, and may be compounded by high heat from the main turbine bearingsif not cooled.

APS Response:

During the DC load shed evolution, the components and circuits which are deenergized will not change state in a manner which results in a plant transient or safety hazard.

The main generator emergency seal oil pump is powered from nonclass/nonseismic normal DC distribution equipment and any effects on this equipment that may occur during the postulated ELAP event are not the result of the DC load shed evolution directed in the FSG.

If the nonclass DC battery and distribution system remain functional during the event, the main generator will be vented using the Station Blackout (SBO) emergency operations procedure, 40EP-9EO08.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE ii. Which breakers will operators open as part of the load shed evolutions?

APS Response: provides tables from "Essential Load List with Critical Safety Function," which list the breakers that plant operators will open. The FSG will provide specific guidance to the operators to implement load shed activities.

iii. How will the DC breakers be physically identified to assist operators in manipulating the correct breakers?

APS Response:

Breakers are labeled with an equipment identification tag. APS will rely on the proper use of human performance tools, such as procedure use and self checking, by operators to ensure the correct breakers are opened.

c. The integratedplan states that the batteries can last up to 10 hours1.157407e-4 days 0.00278 hours 1.653439e-5 weeks 3.805e-6 months with no load shedding and up to 47 hours5.439815e-4 days 0.0131 hours 7.771164e-5 weeks 1.78835e-5 months with load shedding. The Institute of Electrical and Electronics Engineers (IEEE) Standard535-1986, "IEEE Standard for Qualification of Class 1E Lead Storage Batteries for Nuclear Power Generating Stations," as endorsed by Regulatory Guide 1.158, "Qualificationof Safety-Related Lead Storage Batteries for Nuclear Power Plants," February 1989 (ADAMS Accession No. ML003740047), provides guidance for qualifying nuclear-gradebatteriesand describes a method acceptable to the NRC staff for complying with Commission regulations with regard to qualification of safety-related lead storage batteries for nuclearpower plants. Provide documentation that shows that your battery cells fully comply with the qualification principles in clause 5 and meet the requirements in clause 8.2 of IEEE Standard 535, for the duration you are crediting the station batteries in your mitigating strategies integratedplan (See ADAMS Accession No. ML13094A397 for additionalinformation).

APS Response:

This RAI was identified as a generic concern or question during the NRC public meeting on April 18, 2013, regarding the NRC order on mitigating strategies (Order EA-12-049). The nuclear industry will resolve this concern generically through the Nuclear Energy Institute (NEI) and the applicable industry groups (e.g., PWROG, EPRI, etc.). Once this concern is resolved, APS will provide an update to this RAI response in a periodic six-month update to the OIP. NEI will be coordinating with the NRC on the schedule for resolution.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-7 Page 51 of the APS Integrated Plan dated February28, 2013, states, in part, that DC bus voltage is requiredto be monitored in order to ensure that the DC bus voltage remains above the minimum voltage.

Provide the minimum voltage that must be maintained and the basis for the minimum voltage on the DC bus.

APS Response:

Based on engineering analysis, the minimum estimated voltage on the battery is 106.8 volts and is delineated in the FSG. The minimum voltage was determined in a best estimate study for DC bus voltage requirements.

The study for the DC strategy was a best estimate analysis based on an end voltage of 1.78 volts per battery cell. APS will validate the minimum voltage value in the revised analysis described in the response to 049-RAI-Palo Verde-6 to ensure it is based on the most limiting energized component.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-8 NRC Regulatory Guide (RG) 1.128, Revision 2, "InstallationDesign and Installation of Vented Lead-Acid Storage Batteries for Nuclear Power Plants," February2007 (ADAMS Accession No. ML070080013) states, in part, that Conformance with the IEEE Std. 484-2002 requirements (indicatedby the verb "shall") for installation design and installationof vented lead-acidstorage batteries for nuclearpower plants provides an adequate basis for complying with the design, fabrication, erection, and testing requirements set forth in GDCs 1, 17, and 18 of Appendix A to 10 CFR Part 50, as well as Criterion III of Appendix B to 10 CFR Part 50, subject to the following stipulation...

In Subsection 5.4, "Ventilation, " revise the second sentence to be consistent with Regulatory Guide 1.189, as follows:

"The ventilation system shall limit hydrogen accumulation to one percent of the total volume of the battery area."

Please provide a discussion on how hydrogen concentration in the battery rooms will be maintained below the limits established by national standardsand codes (i.e., less than 1% according to the National Fire Code and Regulatory Guide 1.128, Revision 2, which endorses IEEE Standard484, "IEEE Recommended Practice for Installation Design and Installation of Vented Lead-Acid Batteries for StationaryApplications," with exceptions) when the batteries are being rechargedduring Phase 2 and 3.

APS Response:

PVNGS is not committed to Regulatory Guide 1.128, Regulatory Guide 1.189, or IEEE Standard 484-2002. APS's strategy will meet the plant's design basis calculation (13-EC-PK-0204), which calculates 2% hydrogen accumulation in 130 hours0.0015 days 0.0361 hours 2.149471e-4 weeks 4.9465e-5 months with a complete loss of ventilation.

During normal and essential plant operations, exhaust fans maintain the hydrogen concentration of the battery rooms at an acceptable level while the batteries are being charged. If the exhaust fans are not available, battery room doors can be opened.

Battery room exhaust fans are listed in Table 1: Installed Loads Credited in Phase 2, page 53, of the OIP. According to this submittal, when the FLEX 480 VAC generators are running, the loads identified in Table 1 can be systematically energized. Guidance for aligning the system will be included in the FSG. Per Attachment 1A, "Sequence of Events Timeline Modes 1-4," of the OIP, these FLEX generators will be installed and functional by 39 hours4.513889e-4 days 0.0108 hours 6.448413e-5 weeks 1.48395e-5 months into the event. The FSG will ensure the battery room essential exhaust fans are in service prior to placing the battery charger into service. This strategy is consistent with the station essential HVAC design basis and eliminates any hydrogen concerns.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-9 Page 21 of the APS Integrated Plan dated February28, 2013, states, in part, that PVNGS will use the standardEPRI [Electric Power Research Institute] industry preventative maintenance template for establishingthe maintenance and testing actions for FLEX components and that the administrativeprogram will include maintenance guidance, testing procedures and frequencies established based on type of equipment and considerationsmade within the EPRI templates.

Please provide details of the maintenance and testing plan for electrical equipment that is credited for events that require mitigating strategies. The staff is trying to understand how Regulatory Guidance documents, IEEE Standards, manufacturerrecommendations, etc. will be utilized to establish the maintenance and testing programs for the portable/FLEX electrical equipment, especially for batteries and diesel generators.

APS Response:

This RAI was identified as a generic concern or question during the NRC public meeting on April 18, 2013, regarding the NRC order on mitigating strategies (Order EA-12-049). The nuclear industry will resolve this concern generically through the Nuclear Energy Institute (NEI) and the applicable industry groups (e.g., PWROG, EPRI, etc.). Once this concern is resolved, APS will provide an update to this RAI response in a periodic six-month update to the OIP. NEI will be coordinating with the NRC on the schedule for resolution.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-10 Page 59 of the APS Integrated Plan dated February28, 2013, states, in part, that The MV [medium voltage] FLEX generatorwill be connected to the Class 1E 4.16kV [kilovolt] switchgear via an installed FLEX junction box mounted outside on either the west or east wall of the diesel building as shown in Figure 3-39 and Figure 3-41.

Describe how the MV FLEX generatorand the Class 1E diesel generators are isolated to prevent simultaneously supplying power to the same Class 1E bus in order to conform to NEI 12-06, Section 3.2.2, guideline (13), which specifies that appropriateelectrical isolations and interactions should be addressed in procedures and guidance.

APS Response:

The Medium Voltage (MV) FLEX generator will be used only when the Class 1E Diesel Generators are isolated. The FSG (Reference 6) provides guidance for energizing a Class 1E bus using portable generators consistent with NEI 12-06, Section 3.2.2, guideline. The FSG will provide instructions for aligning the MV FLEX generator(s) to either Train A or Train B Class 4.16 KV switchgear. Prior to connecting the MV FLEX generators to a switchgear, the respective Class 1E Diesel Generator output breaker will be racked out to prevent potential for cross connection of the two generators.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-11 Attachment 1B lists as item 3, a deviation from the WCAP-17601-P, "ReactorCoolant System Response to the Extended Loss of AC Power Event for Westinghouse, Combustion Engineering and Babcock & Wilcox NSSS Designs (Proprietary),"January 2013, value for time initiatingcool down from 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months to 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months for the site-specific analysis. The APS integratedplan shows the operatorsare performing numerous tasks during this first hour. Station blackout (SBO) procedures require the operator to start the station blackout generator(SBOG) within one hour, plus the licensee credits performing a load shed on the DC bus within 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months , and opening doors within 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months .

In addition, the licensee identified two actions with time constraints have been identified, observing the condition of the condensate storage tank (CST) and selecting valves that must be closed. In such a critical time operators will be stationed at critical components such as the steam driven AFW pump. The licensee states that they will perform simulator validations to confirm recognizing ELAP entry conditions. Provide a description of tasks to be performed and the personnel available to perform these tasks to allow the staff to evaluate the basis for concluding that these tasks can be reasonably accomplished in the time allotted.

APS Response:

APS does not plan to station Operations personnel at critical components during the initial portions of the Phase 1 FLEX response. In the current plans, the Auxiliary Feedwater (AFW) pump and ADVs are operated from the control room; therefore, no operators are required to be stationed locally at the components. Auxiliary operators will, as part of the FSG actions, be dispatched to verify proper operation locally.

APS will perform a staffing study to demonstrate that sufficient action time margin is available. This effort will include comparison of the available analytical timing and margin with the staffing study results of the NEI 12-01 Phase 2 staffing analysis. APS expects to submit the results of the staffing study by June 2014.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-12 In its integratedplan dated February28, 2013, APS has identified that there is a time constraintof 34 hours3.935185e-4 days 0.00944 hours 5.621693e-5 weeks 1.2937e-5 months to install portable 500 kiloWatt (kW) 480 Volt (V) generators in order to recharge batteries. APS has not identified a means to move the generators along with the concomitant method for reasonableprotection of that means from the identified hazards applicable to PVNGS as would be required to conform to the guidance of NEI 12-06, Section 5.3.2, consideration 5 and Section 9.3.2. APS has listed transportationequipment as equipment to be delivered in the final phase, but has identified an open item for the actual sequence and timing of delivery of the equipment.

Please discuss the basis for concluding that the time constraint of 34 hours3.935185e-4 days 0.00944 hours 5.621693e-5 weeks 1.2937e-5 months can reasonablybe met for the installation of the portable generators as specified in NEI 12-06, Section 3.2.1.7, Principle 6, taking into consideration the specifications of NEI 12-06, Section 5.3.2, Consideration5 and Section 9.3.2.

APS Response:

As of this time, APS has not purchased the 500 kW, 480 V generators nor has the storage location for the 500 kW generators been determined. APS will provide this information in a periodic six-month update.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-13 In its integratedplan dated February28, 2013, APS provided insufficient information to support a conclusion that considerations2 through 4 of NEI 12-06, Section 5.3.3, will be taken into account in the development of the mitigating strategiespursuantto Order EA-12-049. These considerationsaddress the potential impacts of large internal flooding sources that are not seismically robust and do not require ac power, the potential reliance on ac power to mitigate ground water, and the potential impacts of non-seismically robust downstream dams. Please discuss the applicability of these considerationsat PVNGS.

APS Response:

NEI 12-06 section 5.3.3, "Procedural Interfaces," considerations 2 through 4 are discussed below:

2. Consideration should be given to the impacts from large internal flooding sources that are not seismically robust and do not require ac power (e.g., gravity drainage from lake or cooling basins for non-safety-relatedcooling water systems).

PVNGS does not have any lake or cooling basin for nonsafety related cooling water systems that are capable of draining into the safety-related portions of the power block. The circulating water basin is at an elevation lower than the unit elevations. PVNGS does not have significant internal flooding concerns as a result of nonseismic system failures or from flooding as a result of gravity drainage of external bodies of water, and there is no possibility for significant groundwater intrusion into the safety related systems, structures and components (SSC) at the station. A review of design basis internal station flooding calculations for the failure of nonseismic cooling water systems confirms that the safety structures have sufficient capacity to mitigate the consequences of flooding without any AC power. APS has verified ingress and egress are available at the times needed to locations requiring access for operator action.

Flex modifications and portable equipment staging locations supporting the mitigation strategies will consider accessibility, habitability, and two-over-one (2/1) issues as required by NEI 12-06, section 5.3.3. APS will revise FSGs, if required, to ensure appropriate directions are provided for possible hazards and limitations.

3. For sites that use ac power to mitigate ground water in critical locations, a strategy to remove this water will be required.

PVNGS does not have an issue requiring continuous removal of groundwater in critical locations.

4. Additional guidance may be required to address the deployment of FLEX for those plants that could be impacted by failure of a not seismically robust downstream dam.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE PVNGS has no operational concerns or impacts to the deployment of FLEX related to the failure of a downstream dam. Additionally, as stated in the OIP, external flooding concerns do not apply to PVNGS.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-14 In its integratedplan dated February28, 2013, APS did not present information on the potential effects of high ambient temperaturesat the locations where portable equipment would operate in the event it is necessary to use the strategiesin order to allow the staff to evaluate conformance with NEI 12-06, Section 9.3.2. Please discuss the potential effects of high ambient temperatures on portable equipment in the locations such equipment would operate.

APS Response:

NEI 12-06, Sections 9.3.2 and 9.3.3, state that functionality of FLEX equipment during movement in the extreme conditions applicable to the site should be a procurement consideration.

APS will determine the specifications for FLEX equipment, including environmental requirements, during the design development and procedure development phase.

Equipment specifications will meet the requirements of NEI 12-06. APS will provide this information in a periodic six-month update.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-15 In its integratedplan dated February28, 2013, APS did not present information on the identification in plant procedures and guidance of portable lighting such as flashlights or headlamps necessary for ingress and egress to plant areas requiredfor deployment of the strategiesin order to allow the staff to evaluate conformance with NEI 12-06, Section 3.2.2, paragraph(8). Please discuss arrangementsfor the use of portable lighting.

APS Response:

The standard gear/equipment for operators with duties outside the control room includes flashlights. This requirement is currently described in a station procedure and will be added to the FSG. The DC powered, control room emergency lighting system will be available for a duration of up to 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months as indicated in OIP page 50.

Although not credited, Appendix R lighting provides for emergency lighting in select areas of the plant where operators or maintenance personnel may need to perform actions during loss of power conditions. The Appendix R lights have batteries that last a minimum of 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months .

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-16 In its integratedplan dated February28, 2013, APS did not present information on access to the ProtectedArea and internal locked areas in order to allow the staff to evaluate conformance with NEI 12-06, Section 3.2.2, paragraph(9). Please discuss the effects of ac power loss on area access and the need to gain entry to areas where remote equipment operation is necessary.

APS Response: Security-Related Information See Attachment 4 for response.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-17 Page 17, Item 2 of the February 28, 2013, APS Integrated Plan submittal states, in part, that "CENTS is approved by the NRC for modeling naturalcirculation heat removal for single phase flow with vapor is present in the reactor vessel head and pressurizer."

Item 16 on page 72 indicates that within 49 hours5.671296e-4 days 0.0136 hours 8.101852e-5 weeks 1.86445e-5 months of the event initiation, the RCS makeup pump should be installed for use to maintain sub-cooling natural circulation (NC) and to prevent two-phase NC.

Discuss the ELAP coping analysis using CENTS and show that two-phase NC will not begin prior to initiating the required RCS makeup pump within 49 hours5.671296e-4 days 0.0136 hours 8.101852e-5 weeks 1.86445e-5 months . Discuss the specific CENTS-predicted RCS conditions that are used to define the initiation of two-phase NC and address adequacy of the use of the specific RCS conditions for determinationof the time when two-phase NC begins.

APS Response: Westinghouse Proprietary See Attachment 5 for response.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-18 Item 13 on page 19 of the APS Integrated Plan dated February28, 2013, indicates that the ADV backup nitrogen supply is sized for 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months , and item 13 on page 71 requires that the operatormanually operate the ADVs once the nitrogen supply is depleted in 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months .

Please discuss the analysis determining the size of the subject nitrogen supply to show that the nitrogen source is available and adequate, lasting for 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months for use as motive force to operate the ADV.

Please discuss the electricalpower supply that is requiredfor operators to throttle steam flow through the ADVs within 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months and show that the power is available and adequate for the intended use before the operatortakes actions to manually operate the ADVs. Also, discuss the operator actions that are required to operate ADVs manually and show that the required actions can be completed within the required times.

APS Response:

The current PVNGS licensing basis for SBO is a 16 hour1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months coping plant. As part of an earlier licensing basis change, the SBO analyses were updated from 4 to 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months , including the backup gas supply to the ADVs, (Reference 11, "Response to NRC Request for Additional Information (RAI) Regarding Revised Station Blackout Evaluation").

Each ADV is a pneumatically modulated control valve supplied by instrument air or by four dedicated, seismically qualified nitrogen (N 2) accumulators. These accumulators are sized to allow cooldown of the plant during a natural circulation cooldown from full power to shutdown cooling initiation. The cooldown is performed using only safety related equipment concurrent with a loss of offsite power and an assumed single active failure. The PVNGS SBO licensing basis calculation (Reference 3) verifies that the N2 accumulator contains adequate nitrogen mass to perform eleven strokes of ADV function over a 16 hour1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months SBO coping period. Based on allowable leakage from the N2 subsystem, the minimum pressure for the accumulators has been determined to be 615 psig.

In addition, high-pressure nitrogen cylinders are installed on a manifold assembly as a backup to the accumulators. The SBO procedure includes direction to the operators to connect the supplemental nitrogen system if needed. The procedure provides the steps necessary for the operators to connect the supplemental nitrogen system, as needed, to back up the nitrogen accumulators for extended operation of the ADVs (References 4 and 5).

Please discuss the electricalpower supply that is required for operators to throttle steam flow through the ADVs within 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months and show that the power is available and adequate for the intended use before the operatortakes actions to manually operate the ADVs.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE APS Response:

PVNGS load shedding study 13-NS-A108 demonstrates sufficient power is available for two ADVs to remain available for greater than 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months after load shed along with the associated control, indication and power to four DC solenoid valves for the nitrogen supply to the ADVs.

Also, discuss the operatoractions that are requiredto operate ADVs manually and show that the requiredactions can be completed within the required times.

APS Response:

Manual operation of the ADVs is accomplished using Appendix 18, "Local ADV Operation," of procedure 40EP-9EO10, StandardAppendices. This appendix has four attachments, one for each ADV, which describe the actions required to take local/manual control of the ADVs. To take local control of the ADV the operator must perform the following actions:

Verify instrument air is isolated to the ADV (time - about 2 minutes)

Isolate the ADV nitrogen accumulator supply (time - about 1 minute)

Open the ADV actuator equalizing valve (time - about 1 minute)

Align the ADV manual override actuator shaft and install the locking clevis (time -

about 5 minutes)

Operate the ADV as directed by the control room The time required to align the ADV for local/manual operation is less than 15 minutes once the Auxiliary Operator (AO) is at the ADV location. When the ADV is aligned for local/manual operation, the AO may open or close the ADV as directed. The ADV requires 19 complete turns of the handwheel for each 10% change in valve position.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-19 Please clarify the accuracy with which steam generatorpressure can be controlled by manual operation of ADVs after the nitrogen supply is depleted. For example, should steam generatorpressure drop too low, turbine-driven auxiliary feedwater flow could be interrupted or accumulators could rapidly empty. Please provide adequate basis to confirm that manual operation of the ADVs under ELAP conditions would be conducive to maintaining a reasonably constant steam generatorpressure. Please further describe how manual ADV control will be accomplished (e.g., communication between the control room and a local operatorstationed at the ADV), and, as applicable, whether environmental factors such as the potential for ambient noise and heat due to exiting steam have been considered.

APS Response:

The coping strategy for a SBO event requires 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months (Reference 4) of ADV operation using the nitrogen accumulators. Local/manual operation of the ADVs would not be required until 16 hours1.851852e-4 days 0.00444 hours 2.645503e-5 weeks 6.088e-6 months after the initiation of the ELAP event. At that time, the RCS cooldown will be completed, and the rate of change in decay heat will be small and decreasing. As a result, the expectation is that the ADVs will need to be closed to ensure adequate steam pressure to operate the Steam Driven Auxiliary Feedwater Pump. Additionally, the FSG contains a caution to make changes slowly during natural circulation because it takes about 10 minutes to observe the effects of any adjustment in heat removal.

The AO will manually control the ADVs by taking local/manual control of the ADV as described in the response to 049-RAI-Palo Verde-18. The AOs will establish communication with the control room by using radios, satellite phones, or sound powered phones. A sound powered phone jack is located at each ADV operating platform and in the control room.

PVNGS has previous experience in local operation of the ADVs. There is some impact due to noise; however, in the past, PVNGS operators were able to communicate using radios while manually operating the ADVs. The AOs operating the ADVs could use hearing protection or a headset to minimize the noise impact. The ADVs are operated from inside the main steam support structure (MSSS) and the steam exiting the ADVs exhausts outside the MSSS at the roof area.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-20 Item 18 on page 19 of the integratedplan dated February28, 2013, indicates that when the CST depletes, the turbine driven auxiliary feed water pump (TDAFWP) suction path is required to realign to the Reactor Makeup Water Tank (RMWT) within 45 hours5.208333e-4 days 0.0125 hours 7.440476e-5 weeks 1.71225e-5 months . Item 21 of Attachment 1A requires the operator to supply water from the water reclamation facility (WRF) to the CST within 116 hours0.00134 days 0.0322 hours 1.917989e-4 weeks 4.4138e-5 months when the available water in the CST and RMWT is depleted.

a. Please discuss the analysis to show that the required CST - RMWT switchover time is no greater than 45 hours5.208333e-4 days 0.0125 hours 7.440476e-5 weeks 1.71225e-5 months , and realignment time of the WRF to the CST is within 116 hours0.00134 days 0.0322 hours 1.917989e-4 weeks 4.4138e-5 months .

APS Response:

Switching AFW suction from the CST to the RMWT requires opening one manual valve, AFA-V058, followed by closing one manual valve, AFA-V006. These instructions are included in the FSG (Reference 6, Step 3.21). Valves AFA-V058 and AFA-VO06 are located in the AFW turbine-driven pump room. The inventory in the CST is sufficient to last 45 hours5.208333e-4 days 0.0125 hours 7.440476e-5 weeks 1.71225e-5 months (Reference 7, Attachment 1A) before realignment to the RMWT becomes necessary.

Reference 27 analyzes the planned cooldown of the plant, determining the required condensate volume necessary to remove the heat within the water and metal mass of the RCS in addition to decay heat. The results of this analysis along with the water volume of the CST were used to determine the required switchover time in Reference 28 and are presented in Reference 7, Attachment 1A. Reference 6 instructs the operator to take this action based on a specified CST level indication, which will be available during this event, and not event time. Assuming a 30 minute operator action time to manipulate the valves, the realignment can be completed well ahead of the required time.

The inventory in the CST and RMWT is sufficient to last 116 hours0.00134 days 0.0322 hours 1.917989e-4 weeks 4.4138e-5 months (Reference 7, Attachment 1A) after shutdown. Similar to the CST/RMWT switchover required time, the analysis in Reference 22 was used in Reference 28 to determine the time when makeup from the Water Reclamation Facility (WRF) would be required. That time is presented in Reference 7, A. Makeup from the WRF to the CST will be established by running temporary piping from one of the WRF reservoirs to the CST at each unit. The start time for installation of the temporary piping will be based on the estimated time for construction with sufficient margin to the 116 hours0.00134 days 0.0322 hours 1.917989e-4 weeks 4.4138e-5 months .

b. The licensee stated in Table Item 18 on page 19, "CondensateStorage Tank (CST) Empties- Switchover to Reactor Makeup Water Tank (RMWT) (Refueling Water Tank (RWT) (for high Seismic Event)): When the CST depletes, the TDAFW pump suction path is realignedto RMWT. " Please explain how core cooling will be maintained during this transitionperiod.

APS Response:

As the CST inventory depletes, the RMWT can be aligned to the AFW suction. Reference 6, Step 3.21, instructs the operator to open AFA-V058, which opens the suction path to the 26 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE Turbine Driven Auxiliary Feedwater (TDAFW) pump from the RMWT. After AFA-V058 is open, AFA-V006 is closed, isolating the suction path to the CST. There is always a suction source available to the TDAFW pump, which will allow the pump to continue operating during the suction swap to maintain core cooling.

The Refueling Water Tank (RWT) is considered a defense-in-depth water source. If the RMWT is not available, the RWT may be used as a makeup source to the CST, not as a direct suction source to the TDAFW pump. The transfer process will use flexible hoses and a portable pump with sufficient flow capacity to match or exceed TDAFW pump flow to refill the CST. The TDAFW pump will have an uninterrupted suction supply from the CST, which will allow the pump to continue to operate to maintain core cooling.

In either case, if AFW delivery is temporarily lost during the realignment of another source, decay heat levels are lower at this point in the event compared to shortly after shutdown.

Also, the applicable FSG instructs operators to maintain the Steam Generators (SG) 85%

full (wide-range level) (Reference 6). As a result, operators would have time to reestablish makeup to the SGs before inventory in the SGs has depleted.

c. Figure 3-3 on page 81 shows valve "V058" from the RMWT to the AFW suction piping. Please describe the location of this valve and the probable accessibility following an ELAP event, and describe how the RMWT can provide water to the AFW pump.

APS Response:

The RMWT is designed with a dedicated piping connection from the RMWT to the TDAFW pump suction. This connection is normally isolated by valve AFA-V058 located in the TDAFW pump room. This room is on the 80 ft. elevation of the MSSS. There are two ways to access this location. The first is a stairwell near the Turbine Building. At the bottom of the stairwell is a door into the TDAFW pump room.

The second access is from the 100 ft. level (ground level) of the MSSS. On this level, there is a hatch and ladder leading to the moter driven auxiliary feedwater (MDAFW) pump room.

There is a doorway from the MDAFW pump room to the TDAFW pump room. This access path does not require the operator to enter any nonseismically qualified structures to reach the valve.

These areas are also part of the secondary-side walkdown in the FSG (Reference 6, Appendix C). Any accessibility issues would be identified early in the event, before AFA-V058 would need to be operated.

d. The description of Table Item 18 on page 19 indicates that for high seismic events, the operators will switch over to the RWT, but this is not reflected in Table Item 18 on page 72 or Figure 3-3 on page 81. Please describe how the RWT can provide AFW to the TDAFW pump.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE APS Response:

As described above, the RWT cannot directly provide suction to the TDAFW pump. This strategy uses portable pump(s) to refill the CST with RWT inventory, as discussed in Reference 6, Appendix J. The TDAFW pump would then continue to take suction from the CST. This strategy is only included for defense in depth, as the CST and RMWT are both seismically robust sources of sufficient volume.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-21 Page 23 of the APS integratedplan dated February28, 2013, indicates that the emergency operating procedures (EOPs) direct the operators to take action to confirm the closure of the main steam isolation valves (MSIVs). Simultaneous closure of MSIVs for all three units will result in loss of auxiliary steam to the air ejectors and loss of gland seal steam. Provide a description of the affects of losing auxiliary steam to all three units, especially on the turbine if vacuum is lost rapidly.

APS Response:

As stated in the OIP, the SBO EOP directs operators to ensure a Main Steam Isolation Signal (MSIS) has actuated to close all MSIVs. After the MSIVs are closed, the Main Steam system will eventually depressurize, resulting in depressurization of the Auxiliary Steam system.

Auxiliary Steam system loads which lose pressure include the Gland Seal system and various nonclass radioactive waste processing systems. PVNGS does not use steam jet air ejectors to maintain main condenser vacuum. Instead, PVNGS uses air removal vacuum pumps that will be deenergized at the onset of the ELAP event. The impact on the main turbine from loss of vacuum is a shorter stop time than if vacuum had been maintained.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-22 Page 24 of the APS integratedplan dated February28, 2013, states Without ventilation, the TDAFWP room temperature will exceed 130OF within four (4) hours. PVNGS has determined that opening the access doors to the room within 2 hours2.314815e-5 days 5.555556e-4 hours 3.306878e-6 weeks 7.61e-7 months will limit the temperature to a maximum of 130°F, thereby maintaining pump availability.

a. This description implies that there is no margin to the maximum temperature.

Please discuss if conservatisms exist in the analysis and/or the identification of additionaloperationalmargin with respect to the TDAFWP room temperature and the continued operation of the TDAFWP.

APS Response:

The statement referenced above contains an error. It should read, "Without ventilation, the TDAFWP room temperature will not exceed 130OF within four (4) hours." A mitigating strategy has been developed that credits opening doors at the 80 ft and 100 ft elevation at two hours when the room temperature is near 120 0 F. This mitigating action will limit the maximum temperature to less than 130OF for the remainder of the event.

The analysis is performed with an initial TDAFWP room temperature of 95 0 F. This value was selected to envelop all measured TDAFWP room temperature data collected during the months of August and September 2012 in all three units without pump testing in progress.

An outside diurnal temperature profile was applied based on American Society of Heating, Refrigerating and Air Conditioning Engineers (ASHRAE) weather station data for June in Phoenix, AZ with a daily maximum temperature of 1131F. Since the TDAFWP room is below plant grade, the room temperature response is relatively insensitive to the outside temperature while the access door is closed. With the door open, exchange of air between the TDAFWP room, stairwell, and turbine building breezeway does occur, and the timing of the peak room temperatures coincides with the outside daily maximum.

Several conservative assumptions are applied in the analysis of the TDAFWP room temperature response:

Heat conduction into the ground from the north wall and the floor are ignored.

" A minimal heat transfer coefficient of 1.0 Btu/hr-ft 2.OF is used for the heat transfer to the gap between the MSSS and Containment Building on the west side of the room.

The temperature of the outside wall on the east side of the room adjacent to the pipe tunnel is set to a constant value of 128.5 0 F.

The initial temperature of the MSSS rooms located above the TDAFWP room is set to the building design temperature of 120 0 F.

The heat addition rate into the MSSS rooms located above the TDAFWP room from the feedwater piping does not credit decreasing feedwater temperature in the isolated lines.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE

" Steam leakage into the TDAFWP room from the gland seals and casing drain is assumed to remain constant throughout the event and does not decrease as the SG pressure is lowered.

The surface temperatures of the condensate drain lines and turbine steam exhaust piping are increased to the maximum expected values immediately following AFW actuation and are held constant for the duration of the event.

b. Please clarify whether the initial temperature condition assumed the worst-case outside temperature with the plant operating at full power. Provide the list of electrical components that are located in the TDAFWP room and are necessary to ensure successful operation of the TDAFWP. Also, please provide the qualification level for temperature and pressure for these electrical components for the duration that the TDAFWP is assumed to perform its mitigating strategies function.

APS Response:

Table 1 below provides a list of equipment located in the TDAFWP compartment (room C-09). NUMARC 87-00, Guidelines and Technical Bases for NUMARC Initiatives Addressing Station Blackout at Light Water Reactors, section 2.7.1 (2) (Reference 9) was used to determine the functionality of these components. Based on the analysis described in the response to 049-RAI-Palo Verde-22a above, the TDAFWP compartment meets condition 2 of NUMARC 87-00 and equipment within the compartment remains functional and continues to perform its intended function during an ELAP.

049-Palo Verde RAI Table 1 List of Equipment in Auxiliary Feedwater Turbine Driven Pump Room Item Equipment Short Component Description Manufacturer DCID Description 1 JAFAE01**INSTRU AFW Control AUX.FDWTR.CONTROL Terry Turbine Panel PANEL 2 JAFAE01*CON1*RELAYX Motor Starter RELAY MTR STARTER FOR Allen Bradley Relay VALVE J-AFA-HV-54 3 JAFAE01*CRI*RELAYX Auto Reset RELAY AUTO RESET FOR Amerace Relay VALVE 1J-AFA-HV-54 4 JAFAE01*CR2*RELAYX Alarm Relay RELAY CONTROL POWER Amerace LOSS ALARM FOR VALVE J-AFA-HV-54 5 JAFAE01*CR4*RELAYX Ramp Starter RELAY RAMP START AUX Potter Relay FEEDWATER TURB Brumfield 6 JAFAE01*CR5*RELAYX Overspeed RELAY TURBINE Potter Trip Relay OVERSPEED TRIP FOR Brumfield VALVE J-AFA-HV-54 31 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE Item Equipment Short Component Description Manufacturer DCID Description 7 JAFAE01*R17*INSTRU Dropping DROPPING RESISTOR Vishay Resistor R17, (EG-M POWER Intertech SUPPLY-48 VDC)[ AFW CTRL PANEL]

8 JAFAFT0040A**IXMITR Flow AUX FEEDWATER FLOW Rosemount Transmitter TO SG 1 9 JAFAPT0018**IXMITR Pressure AUX FEEDWATER PUMP Rosemount Transmitter AFA-P01 DISCH PRESSURE INDICATION 10 JAFBFT0041A**IXMITR Flow AUX FEEDWATER FLOW Rosemount Transmitter TO SG 1 11 JSGAPT0313**IXMITR Pressure ADV-179 AND ADV-184 Rosemount Transmitter TRANSMITTER PRESSURE FOR ATM DUMP VALVE CONTROL 12 JAFAHV0032**MOTORX AFW Pump AUX FEEDPUMP AFA-P01 Peerless Elec.

Motor FLOW CONTROL VALVE Operator TO SG 1 13 JAFAHV0032**VALVOP AFW Motor AUX FEEDPUMP AFA-P01 Limitorque Operator FLOW CONTROL VALVE TO SG 1 14 JAFAHV0054**MOTORX Turbine Trip AUX FEEDPUMP AFA-P01 Peerless Elec.

Motor TRIP & THROTTLE VALVE Operator 15 JAFAHV0054**VALVOP Turbine Trip AUX FEEDPUMP AFA-P01 Limitorque Operator TRIP & THROTTLE VALVE 16 JAFAUV0037**MOTORX AFP Isolation AUX FEEDPUMP AFA-P01 Peerless Elec.

Valve Motor FEED ISOLATION VALVE Operator TO SG 2 17 JAFAUV0037**VALVOP Isolation AUX FEEDPUMP AFA-P01 Limitorque Valve Motor FEED ISOLATION VALVE Operator TO SG 2 18 JAFCHV0033**MOTORX AFW Motor AUX FEEDPUMP AFA-P01 Peerless Elec.

Operator FLOW CONTROL VALVE TO SG 2 19 JAFCHV0033**VALVOP AFW Motor AUX FEEDPUMP AFA-P01 Limitorque Operator FLOW CONTROL VALVE TO SG 2 20 JAFCUV0036**MOTORX AFP Isolation AUX FEEDPUMP AFA-P01 Peerless Elec.

Valve Motor FEED ISOLATION VALVE Operator TO SG 1 21 JAFCUV0036**VALVOP Isolation AUX FEEDPUMP AFA-P01 Limitorque Valve Motor FEED ISOLATION VALVE Operator TO SG 1 32 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE Item Equipment Short Component Description Manufacturer DCID Description 22 JSGAHY0184C**INTCPM Converter I/P ADV-184 I/P CONVERTER Masoneilan CONVERTER I/P SG 1 LINE 1 ATM DUMP VALVE 23 JSGBHY0178C**INTCPM Converter I/P ADV-178 I/P CONVERTER Masoneilan CONVERTER I/P SG 1 LINE 2 ATM DUMP VALVE 24 JSGAZT0184**IXMITR Position ADV-184 POSITION Schaevitz Transmitter TRANSMITTER 25 JSGBZT0178**IXMITR Position ADV-178 POSITION Schaevitz Transmitter TRANSMITTER 26 JAFAHS0052B**CKTBRK Hand Switch AF TURB O.S. TEST J.B.T.

SWITCH HAND AF TURBINE OVERSPEED TEST,LOCAL PANEL 27 JAFAHS0052C**CKTBRK Hand Switch AF TURB SPEED Micro Switch CONTROLXFER SWITCH HAND AF TURB SPEED CONTROL TRANSFER,LOCAL PANEL 28 JAFAHS0054C**CKTBRK Hand Switch AF TURB TRIP LP Allen Bradley SWITCH HAND AF TURBINE TRIP LOCAL PANEL 29 JAFAHS0054E**CKTBRK Hand Switch LOCAL HS FOR "A" AFW Micro Switch PUMPTURB TRIP/THROTTLE VALVE SWITCH HAND AF TURBINE TRIP VALVE JOG,LOCAL PANEL 30 JAFASI0052C**INDREC Speed AUX FDWTR TURBINE Beede Elect.

Indicator SPEED INDICATOR-LOCAL PNL INDICATOR SPEED AUXILIARY FEEDWATER TURBINE,LOCAL PANEL 31 JAFASK0052C**ICNTRL Speed AUX FDWTR PUMP Beckman Instr.

Controller ATURBINE SPD CNTRL-LCL PNL CONTROLLER SPEED AUX FEEDWTR PUMP A TURB,LOCAL PANEL 32 JAFAST0052**IXMITR Speed AUX FEEDWTR TURBINE Woodward Gov Transmitter SPEED TRANSMITTER AUXILIARY FEEDWTR TURBINE 33 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE Item Equipment Short Component Description Manufacturer DCID Description 33 JAFAHY0054**VALVOP Solenoid OPERATOR SOLENOID Trombetta Operator AUX FEEDWTR TURBINE TRIP VALVE 34 MAFAK01**ICNTRL Governor GOVERNOR AUXILIARY Woodward Gov Control Unit FEEDWATER PUMP TURBINE ELECTRONIC GOVERNOR AUXILIARY FEEDWATER PUMP TURBINE ELECTRONIC CONTROL UNIT 35 MAFAK01**MECFUN Governor GOVERNOR AUXILIARY Woodward Gov FEEDWATER PUMP TURBINE 36 JSGBPT0301**IXMITR Pressure ADV-178 ACCUMULATOR Rosemount Transmitter NITROGEN PRESS TRANSMITTER 37 JSGAPT0315**IXMITR Pressure ADV-184 ACCUMULATOR Rosemount Transmitter NITROGEN PRESS TRANSMITTER 34 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-23

a. Please list the safety and non-safety-relatedsystems or equipment that are credited in the ELAP analysis. For the non-safety-relatedsystems or equipment, please discuss the safety functions that are intended to maintain andjustify how the non-safety-related systems or equipment are available and reliable for their intended use.

APS Response:

Equipment, systems, and structures credited for the OIP strategies are safety related except for the upper portion of the CST and the RMWT and its associated piping. Both the RMWT and the upper portions of the CST are designed to 10 CFR 50 Appendix B augmented quality (i.e., seismic 2 over 1) and to withstand an operating basis earthquake (OBE). As described on page 26, Notes: Item 1, of the OIP, the seismic fragility evaluations were performed using the guidance contained in EPRI NP-6041-SL Revision 1, "A Methodology for Assessment of Nuclear Plant Seismic Margin," August 1991 (Reference 10). The CST upper portions and the RMWT and associated systems were found to be robust with a calculated acceptable high-confidence-of-low-probability-of-failure (HCLPF) capacity compared with the station Safe Shutdown Eartquake (SSE) seismic level. As a contingency for these water sources, the FSG also provide guidance for the transfer of water from the RWT, which is a seismic category 1, quality-related structure. Equipment needed to transfer water from the RWT to the CST is currently on site and would be deployed as a mitigating strategy.

b. Pleasejustify that the instrumentation listed on pages 25 - 26 and pages 33 - 34 of the APS integratedplan dated February28, 2013, and the associated setpoints credited in the ELAP analysis for automatic actuations and indicationsrequired for the operatorto take appropriateactions are reliable and accurate in the containment harsh conditions with high moisture levels, temperature, and pressure during the ELAP event.

APS Response:

As described in the OIP, pages 25 and 26, a minimum set of instrumentation has been selected to provide control room operators with key safety-function information.

Instruments identified are safety related, seismically qualified, meet the environmental qualification requirements of 10 CFR 50.49, and are verified qualified consistent with the criteria in NEI 12-06, Section 3.2.1.12. The PVNGS ELAP analysis does not credit automatic actuation beyond the SBO scenarios, and such actions would occur within the first hour of the event. The SBO response strategies were reviewed and approved by the NRC in Reference 5. Operator actions directed by the FSG are manual actions after the first hour.

Instrumentation and components credited are qualified to 10 CFR 50.49 for loss of coolant accident (LOCA) and steam line break; therefore, they will remain accurate and reliable for the duration of the beyond-design-bases event. Additionally, the maximum temperature expected within containment during an ELAP remains below the threshold of the equipment qualification harsh limit of 230 0 F.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-24 The last paragraphon page 32 and item 2 on page 74 of the APS integratedplan dated February 28, 2013, indicate that PVNGS RCP seals are assumed to have a maximum leakage of 17 gallons per minute (gpm) per pump at normal operating pressure.

Please discuss an analysis or RCP seal leakage testing data to show adequacy of the RCP seal leakage rate of 17 gpm per pump assumed in the ELAP analysis. The RCP seal leakage testing data used to support the assumed leakage rate should be applicable to the PVNGS RCP seals (with respect to the seal material, design and seal cooling systems) and ELAP conditions (in terms of the temperature and pressure, and seal failure mechanisms discussed in Section 6.4 of WCAP-17601 -P) for an extended period consistent with the ELAP coping time. Also, please address applicability of the information In Section 4.4.2 of WCAP-17601, Rev. 0, which states "It has been shown that the probability of seal failure greatly increases when there is less than 50OF of subcooling in the Cold Legs."

APS Response: Westinghouse - Proprietary See Attachment 5 for response.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-25 Item 36 on page 15 of the APS integratedplan dated February28, 2013, states, in part, that Operatoractions are credited for cooling and depressurizing the RCS.... RCP seal leakage rates are dependent on RCS pressure and will decrease with deceasing pressure."

Please discuss how CENTS calculates the pressure-dependentRCP seal leakage rates. If CENTS uses the equivalent size of the break area based on the initial leakage rate of 17 gpm per pump to calculate the pressure-dependentRCP seal leakage rates during the ELAP, please discuss whether the size of the break area is changed or not in the analysis for the ELAP event. If the size is changed, discuss the changed sizes of the break area and address the adequacy of the sizes. If the break size remains unchanged, address the adequacy of the unchanged break size throughout the ELAP event in conditions with various pressure, temperature (considering that the seal material may fail due to an increased stress induced by cooldown) and flow conditions that may involve two-phase flow which is different from the single phase flow modeled for the RCP seal tests that are used to determine the initialseal leakage rate of 17 gpm.

APS Response: Westinghouse - Proprietary The proprietary portion of this response is provided in Attachment 5.

This RAI was identified as a generic concern or question during the NRC public meeting on April 18, 2013, regarding the NRC order on mitigating strategies (Order EA-12-049). The nuclear industry will resolve this concern generically through the Nuclear Energy Institute (NEI) and the applicable industry groups (e.g., PWROG, EPRI, etc.). Once this concern is resolved, APS will provide an update to this RAI response in a periodic six-month update to the OIP. NEI will be coordinating with the NRC on the schedule for resolution.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-26 The third paragraphon page 35 of the APS integrated plan dated February 28, 2013, states, in part, that PVNGS control rod shutdown margin and borated water inventory in the RCS and SITs [safety injection tanks] are sufficient to prevent re-criticalityof the core. "

Please discuss the boron mixing model used for the re-criticalityanalysis in support of the plant FLEX mitigation strategies, and address the adequacy of the boron mixing model for the intended purpose with support of an analysis and/or boron mixing test data applicable to the ELAP conditions.

APS Response: Westinghouse - Proprietary The proprietary portion of this response is provided in Attachment 5.

This RAI was identified as a generic concern or question during the NRC public meeting on April 18, 2013, regarding the NRC order on mitigating strategies (Order EA-12-049). The nuclear industry will resolve this concern generically through the Nuclear Energy Institute (NEI) and the applicable industry groups (e.g., PWROG, EPRI, etc.). Once this concern is resolved, APS will provide an update to this RAI response in a periodic six-month update to the OIP. NEI will be coordinating with the NRC on the schedule for resolution.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-27 Tables A and B of the February28, 2013, submittal list the phases 2 and 3 portable equipment required for the ELAP mitigation. Table A lists four self priming pumps and four high pressure RCS makeup pumps that are required during the phase 2 of ELAP.

The required capacities of the pumps are 370 gpm (at 500 psi) and 30 gpm (at 1525 psi) for the priming pumps and high RCS makeup pumps, respectively. Table B lists high pressure RCS makeup pumps and pumps to makeup to the CST from reservoirs that are requiredduring the phase 3 of ELAP. The requiredcapacities of the respective pumps are 30 gpm (at 1525 psi) and 1200 gpm (at 130 psi).

Specify the required times for the operatorto realign each of the above discussed pumps and confirm that the required times are consistent with the results of the ELAP analysis.

Discuss how the operator actions are modeled in the ELAP to determine the required flow rates of the portable pumps, and justify that the capacities of each of the above discussed pumps are adequate to maintain core cooling during phases 2 and 3 of ELAP.

APS Response: Westinghouse - Proprietary See Attachment 5 for response.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-28 Attachment 1A lists the sequence of events timeline for Mode 1-4. On page 70, item 11 indicates that the analysis assumes cooldown initiation time of 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months and that the RCS cooldown to 3501F is expected to complete within 4.11 hours1.273148e-4 days 0.00306 hours 1.818783e-5 weeks 4.1855e-6 months of initiation of the event.

List the operatoractions credited in the analysis to complete the cooldown from 1 hour1.157407e-5 days 2.777778e-4 hours 1.653439e-6 weeks 3.805e-7 months to in 4.11 hours1.273148e-4 days 0.00306 hours 1.818783e-5 weeks 4.1855e-6 months , and discuss how the operatoractions are modeled in the cooldown analysis for the 4.11 -hour period using CENTS.

APS Response:

APS performed the CENTS studies first and then determined the operator actions and time frames necessary to comply with the study. The CENTS computer code is an interactive, faster-than-real-time computer code for the simulation of Nuclear Steam Supply Systems and related systems. The CENTS code allows the user to run the code using preselected dynamic conditions or by inputting parameters into the code manually to make changes, take manual actions, or initiate malfunctions. This provides a means to evaluate transient conditions.

Although additional actions will be taken by the operators to perform the plant cooldown, the actions which are credited in the analysis to complete the cooldown are described below. All of the credited actions are performed from the control room.

Initiate a cooldown by adjusting the B Train ADV position on each SG to increase steam flow and establish a cooldown rate of approximately 70°F per hour

Feed the SGs with the TDAFWP to achieve and maintain SG water levels at 85%

narrow range (NR). This approach increases the available volume of secondary water

" Stop the cooldown and stabilize the plant by adjusting the B Train ADV position on each SG to decrease steam flow. The plant is stabilized at an analytical limit of:

o 350WF (primary) o 135 psia (secondary) 40 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-29 Item 2 on page 68 of the February28, 2013, submittal indicates that at 0.017 hours1.967593e-4 days 0.00472 hours 2.810847e-5 weeks 6.4685e-6 months (60 seconds), the TDAFWP begins.

The above information appearsinconsistent with that listed in Table 5.1-1 of DAR-TDA12-2 (Reference 5 to the integratedplan), "Sequence of Events" for the case with the RCP leakage rate of 17 gpm/pump. Table 5.1-1 indicates that at 0.203 hours0.00235 days 0.0564 hours 3.356481e-4 weeks 7.72415e-5 months , the auxiliary feedwater (AFW) actuation signal actuates for steam generator(SG) 1.

With a 60-second delay, the AFW flow to both SGs begins from the TDAFW pump at 0.22 hours2.546296e-4 days 0.00611 hours 3.637566e-5 weeks 8.371e-6 months . Clarify and correct the inconsistency.

APS Response:

The time for the TDAFWP to supply flow to the SGs presented in Reference 27 is correct, and the time in the February 28, 2013, submittal (Reference 7), Page 68, Item 2 should be corrected to reflect 0.220 hours0.00255 days 0.0611 hours 3.637566e-4 weeks 8.371e-5 months .

The TDAFWP start time in the sequence of ELAP events was based on a 60 second (0.017 hour1.967593e-4 days 0.00472 hours 2.810847e-5 weeks 6.4685e-6 months ) delay in start of TDAFWP after the Auxiliary Feedwater Actuation Signal (AFAS) is initiated as a result of low level in the SGs. This time delay is conservative relative to the

_<46 second start time required in the Updated Final Safety Analysis Report (UFSAR)

(Reference 26), Table 7.3-1B, Engineered Safety Features Response Times.

An ELAP analysis was performed in Reference 27. During an ELAP event, the AFAS would not occur until SG level drops to the SG low level setpoint. In Reference 27, AFAS is conservatively initiated at a lower level than the PVNGS setpoint to accommodate uncertainty. In Case 1, which is representative of all 4 ELAP cases documented in Reference 27, the AFAS for SG 1 and SG 2 is generated and AFW flow to both SGs occurs at 0.220 hours0.00255 days 0.0611 hours 3.637566e-4 weeks 8.371e-5 months with acceptable results.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-30 Section 3.2 of WCAP-17601-P discusses the PWR Owners Group's recommendations that cover following subjects for consideration in developing FLEX mitigation strategies:

(1) RCP seal leakage rates; (2) adequate shutdown margin; (3) time initiating cooldown and depressurization;(4) prevention of the RCS overfill; (5) blind feeding an SG with a portable pump; (6) SIT performance; and (7) asymmetric naturalcirculation cooldown (NCC).

Discuss the licensee's position on each of the recommendations discussed above for developing the FLEX mitigation strategies. List the recommendations that are applicable to the plant, provide rationalefor the applicability, address how the applicable recommendations are considered in the ELAP coping analysis using CENTS, and discuss the plan to implement the recommendations. Also, provide rationale for each of the recommendations that are determined to be not applicable to the plant.

APS Response: Westinghouse - Proprietary See Attachment 5 for response.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-31 Item 1 on page 74 of the February28, 2013, submittal indicates that the licensee uses a plant specific best estimate (BE) decay heat curve in the thermal hydraulic analysis for the ELAP event. The licensee states that the use of the plant-specific BE decay heat curve is a deviation from WCAP-1 7601, but claims that the deviation is justified by CN-REA-12-36 (Reference 7 to the integratedplan).

Provide the justification for the NRC staff to review. Alternatively, if CN-REA-12-36 has documented the appropriatejustification, the licensee could provide the relevant pages for the NRC staff to review and approve.

APS Response: Westinghouse - Proprietary See Attachment 5 for response.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-32 Describe the electrical power requirements for Phase 3 of the mitigating strategies integrated plan and provide the capacity of the power sources.

APS Response:

The initial electrical loading for FLEX phase 3 is similar to the loading in phase 2 as described in Table 1: Installed Loads Credited in Phase 2, page 53 of the OIP submittal.

The alternative train equipment listed on this table may be powered to continue the station's coping strategies and provide down time or maintenance time for the primary train when the 4,160 VAC generators are delivered to the station from the Regional Response Centers (RRC). The power sources selected for phase 3 are two, 4,160 VAC generators, each rated for 2 megawatts. These generators will be available to power the 480 VAC distribution buses from the station 4,160 VAC class buses, powering the permanent, essential emergency systems. Additionally, when the 4,160 VAC generators are available, the opposite train from the initially energized 480 VAC load centers can be energized, increasing flexibility and defense in depth by providing power to an additional train of equipment used for coping.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-33 The last paragraphon page 24 of the February28, 2013, submittal indicates that "core cooling is maintained through once through heat removal from the RCS via coolant boil-off...During this event, a hot leg vent will have been established such that a release path is available to support once through via boil-off. "

Discuss the analysis (including methods, assumptions, and results) to show that core cooling with SG not available can be maintained through once through heat removal from the RCS via coolant boil-off. Include in the discussion:

a. Discussion of how gravity feed flow from the RWT will be monitored and throttled to match core boiloff under ELAP conditions.

b. Discussion of the timing for providing primary makeup flow via gravity feed from the R WT relative to the time of core uncovery under reduced reactor coolant system inventory conditions.

c. Discussion of what supporting equipment is implied to be operable when a steam generatoris consideredavailable to mitigate an ELAP (e.g., turbine-driven auxiliary feedwater pump, main steam relief valves, atmospheric dump valves (ADVs)).

d. Discussion of scenarios wherein there is neither a hot leg vent nor a steam generatoravailable, relative to the guidance of NEI 12-06. The staff understands that Generic Letter 88-17 recommended establishing a hot leg vent under conditions of reduced reactorcoolant system inventory (i.e., water level lower than three feet below the reactor vessel flange), ratherthan on the basis of steam generatoravailabilityunder ELAP conditions in shutdown and refueling modes. Furthermore,based on the requirementfor high-pressure makeup specified for shutdown modes without steam generators in Table 3-2 of NEI 12-06, it is not clear that scenarios without a hot leg vent are consideredbeyond scope.

APS Response:

This RAI was identified as a generic concern or question during the NRC public meeting on April 18, 2013, regarding the NRC order on mitigating strategies (Order EA-12-049). The nuclear industry will resolve this concern generically through the Nuclear Energy Institute (NEI) and the applicable industry groups (e.g., PWROG, EPRI, etc.). Once this concern is resolved, APS will provide an update to this RAI response in a periodic six-month update to the OIP. NEI will be coordinating with the NRC on the schedule for resolution.

It has been determined through discussion with NEI that the entry in Table 3-2 of NEI 12-06 that requires high pressure makeup to the RCS in shutdown modes without SGs is incorrect.

High pressure makeup is required in Modes 1 through 4, but is not required in Modes 5 or 6.

The RCS inventory requirement should have been separated into its own row in the table and not combined with the core cooling function in Modes 5 and 6 without SGs.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-34 On pages 27 and 30 of the response dated February28, 2013, please provide the following items regarding the discussion of core cooling with steam generatorsnot available in Phases 2 and 3:

a. The basis for concluding that setting makeup flow to the steaming rate plus ten percent is sufficient to prevent significantboric acid precipitationin the core.

APS Response:

The minimum portable pump Reactor Coolant system (RCS) make-up flow rate of 1.1 times the steaming rate is the plant specific value determined consistent with Reference 12, Table D-1 Core Cooling and Heat Removal (Modes 5 and 6 with steam generators not available) pump sizing and inventory requirement criteria. The basis for concluding that this flow rate is sufficient to prevent boric acid precipitation is established by performing a boron mass balance for the limiting condition assuming conservative decay heat and other inputs.

A boron concentration in the RCS of 50,000 ppm boron is used which is conservatively below the saturated solubility concentration at the reactor coolant boiling point. The limiting solubility concentration is derived from the boric acid solubility at the boiling point at atmospheric pressure which is equal to 29.3 wt % (Page 2 Reference 38). This value is converted to ppm boron (1 wt 0/b boric acid = 1748 ppm (Figure 4 Reference 2)) and is equal to a value of 51,216 ppm boron. It is assumed the liquid in the two phase mixture at the hot side opening will bound the bulk concentration in the core.

The make-up boron concentration from the RWT is equal to the maximum 4400 ppm (Surveillance Requirement 3.5.5.3 of, Appendix A of Reference 37). The mass balance for boron at this limiting condition is shown below.

mnq 1 x 4400 ppm = (minj - Mrstra) x 50,000 ppm 4400 ppm ((min - mstm) mstm 50,000 ppm mini Mini mstm 4400 ppm

__ =-1 raini 50,000 ppm mstm m =

-n 4400 ppm = mstm x 1.1 50,000 ppm Where:

mij= Injection mass flow rate mstm = Steaming mass flow rate m,,n - mstm = Mass flow exiting the RCS as liquid 46 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE The results show that if the injection mass flow rate is 1.1 times the steaming mass flow rate ( 1 0% or larger), the RCS boron concentration would not increase above the limiting concentration of 50,000 ppm boron.

b. The source of borated coolant once the inventory of the refueling water tank is depleted (e.g., reactorgrade water, raw water mixed with boric acid).

APS Response:

A functional requirement will be that the RCS makeup source is borated reactor grade water. The long term strategy by which this source of water is established is still under development. APS will provide an update to this RAI response in a periodic six-month update.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-35 Please provide justification that version 4.07 of the MAAP code has adequate capability for performing analysis to demonstrate the integrity of large-dry containments during ELAP conditions. The justification may include discussion of the adequacy of the code's relevant models and correlations,benchmarking of code calculations againstrelevant experimental data, and relevant comparisons to calculations with state-of-the-art containment analysis codes. The justification may further include the presence of significantmargin to acceptance criteria, if applicable, for scenarios at power as well as during shutdown and refueling.

APS Response:

This RAI was identified as a generic concern or question during the NRC public meeting on April 18, 2013, regarding the NRC order on mitigating strategies (Order EA-12-049). The nuclear industry will resolve this concern generically through the Nuclear Energy Institute (NEI) and the applicable industry groups (e.g., PWROG, EPRI, etc.). Once this concern is resolved, APS will provide an update to this RAI response in a periodic six-month update to the OIP. NEI will be coordinating with the NRC on the schedule for resolution.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-36 Please clarify whether the mass and energy leakage to containment determined in the containment integrity analysis using the MAAP code are consistent with the predictions of the CENTS code. To the extent that data is available from existing simulations, please include plots comparing integratedmass and energy effluents from the two codes with and without the availability of the steam generators and provide justification if significantdifferences exist.

APS Response:

This RAI was identified as a generic concern or question during the NRC public meeting on April 18, 2013, regarding the NRC order on mitigating strategies (Order EA-12-049). The nuclear industry will resolve this concern generically through the Nuclear Energy Institute (NEI) and the applicable industry groups (e.g., PWROG, EPRI, etc.). Once this concern is resolved, APS will provide an update to this RAI response in a periodic six-month update to the OIP. NEI will be coordinating with the NRC on the schedule for resolution.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-37 Please discuss how the MAAP containment analysis models heat losses from the primary system to containment and provide justification for its adequacy.

APS Response:

This RAI was identified as a generic concern or question during the NRC public meeting on April 18, 2013, regarding the NRC order on mitigating strategies (Order EA-12-049). The nuclear industry will resolve this concern generically through the Nuclear Energy Institute (NEI) and the applicable industry groups (e.g., PWROG, EPRI, etc.). Once this concern is resolved, APS will provide an update to this RAI response in a periodic six-month update to the OIP. NEI will be coordinating with the NRC on the schedule for resolution.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-38 Please discuss the quality assuranceprocess under which the MAAP calculations were performed.

APS Response:

The MAAP calculations performed in support of this effort were completed under the PVNGS Non-Process Software Quality Assurance Program procedure 80DP-OCCO2. The MAAP code is classified as a Category-C qualified code. The engineers performing the calculation have attended the EPRI/Fauske MAAP training program and are documented as qualified under the PVNGS qualification guidelines. The MAAP calculations were independently reviewed and the records of the calculations are retained as life-time plant records.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-39 Page 16 of the submittal dated February28, 2013, states, "The actions specified for Mode 1 to Mode 4 conditions are bounding when compared to the Mode 5, Mode 6, and full core offload scenarios because the upper mode scenarios require the most personnel, actions, and time constraints."

Please provide the basis for this conclusion (e.g., analyses, studies, benchmarking, etc.)

with particularemphasis on maintaining containment conditions as identified by Open Item #4.

APS Response:

This RAI was identified as a generic concern or question during the NRC public meeting on April 18, 2013, regarding the NRC order on mitigating strategies (Order EA-12-049). The nuclear industry will resolve this concern generically through the Nuclear Energy Institute (NEI) and the applicable industry groups (e.g., PWROG, EPRI, etc.). Once this concern is resolved, APS will provide an update to this RAI response in a periodic six-month update to the OIP. NEI will be coordinating with the NRC on the schedule for resolution.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-40 Please clarify whether the Open Item Table on page 67 should include pages 40, 41, (potentially) 42, and 43 under Affected Pages by 014 ratherthan pages 45, 46, and 48.

For Open Item #4, please describe the evaluation and/or analysis to be performed, the expected completion date, and the date the results will be made available to the NRC.

APS Response:

The OIP (Reference 7) Open Item Table on page 67, Affected Pages column, should include pages 40 through 43.

This RAI was identified as a generic concern or question during the NRC public meeting on April 18, 2013, regarding the NRC order on mitigating strategies (Order EA-12-049). The nuclear industry will resolve this concern generically through the Nuclear Energy Institute (NEI) and the applicable industry groups (e.g., PWROG, EPRI, etc.). Once this concern is resolved, APS will provide an update to this RAI response in a periodic six-month update to the OIP. NEI will be coordinating with the NRC on the schedule for resolution.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-41 Please clarify how the planned strategies for providing makeup to the spent fuel pool will be implemented while the pool is being cooled by boiling. For example, as noted on page 19 of the response dated February28, 2013, the fuel building rollup door is opened at 11.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months . On page 45, the response further notes that, with a full core offload, the most conservative time to boil is 3.3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months . Finally, pages 45-47 refer to alternate mitigation equipment staging areas and connection points located inside the rollup door to the fuel building and the need to maintain accessibility to this area. Therefore, please identify the predictedpeak temperature and humidity in the areas where accessibilityis requiredduring spent fuel pool boiling both prior and subsequent to the fuel building rollup door being opened, and confirm that conditions would be tolerable for operators over the expected exposure time for normal and core offload spent fuel heat loads.

Provide validation that for escalated SFP boil off or leakage scenarios, implementation strategies include analysis of personnel resource availability to complete actions within implementation strategy time limits. Analysis needs to include personnel resource availability in consideration for other concurrentactivities that also need to be performed site wide.

APS Response:

For SFP cooling, two scenarios were evaluated as listed on page 44 of the OIP. Page 45 of the OIP lists the time-to-boil values for each case. The SFP decay heat during Mode 1 to Mode 6 with the core not off loaded case causes SFP boiling to occur approximately 11.5 hours5.787037e-5 days 0.00139 hours 8.267196e-6 weeks 1.9025e-6 months after the initiating event. The SFP decay heat following full core offload case causes SFP boiling to occur approximately 3.3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months after the event. The sequence of events timeline (Page 16 of of the OIP) and associated mitigating strategy time constraints, including page 19 of the OIP, have been identified for the PVNGS Mode 1 to Mode 4 FLEX Plan. Resources for the lower Mode scenarios will be addressed in response to 049-RAI-Palo Verde-39 through NEI and the applicable industry groups.

Two connection points exist to provide SFP makeup. The primary location is outside the Fuel Building and the alternate location is within the Fuel Building near the rollup door.

Both connection points can provide makeup to the SFP while the pool is being cooled by boiling.

The location of the alternate connection point is in close proximity to the point of access to the Fuel Building as described on page 46 of the OIP. The distance from the rollup door to the connection point will be approximately 5 feet. Figures RAI-41-1 and RAI-41-2 show the relative location of the alternate connection point and the SFP roll-up door on the 100 ft.

elevation.

The peak temperature and humidity conditions in the area of the alternate connection point are expected to be close to outside ambient conditions and will not significantly impact operator actions. This is true for times before and subsequent to the Fuel Building rollup door opening action time constraints, which are identified as 11 hours1.273148e-4 days 0.00306 hours 1.818783e-5 weeks 4.1855e-6 months in Table Item 12a of A of the OIP for Modes 1-4 and 3.3 hours3.472222e-5 days 8.333333e-4 hours 4.960317e-6 weeks 1.1415e-6 months on Page 45 for full core offload scenarios.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE The physical arrangement of the Fuel Building has an influence on the accessibility of the alternate connection location. Because of the distance in elevation between the SFP level and alternate connection location, the SFP boiling phenomenon is not expected to cause significant temperature and humidity effects at the alternate connection point. Steam, due to boiling, will rise above the 140 ft. elevation and temperature and humidity in the upper portion of the Fuel Building will be higher than the rest of the building. The Fuel Building roof external low point is specified as elevation 194 ft. and the Fuel Building ceiling internal elevation is approximately 2 ft. below at elevation 192 ft. The SFP operating floor and roof elevations are shown in Figure RAI-41-3. At the location where the operator connects the portable pump to SFP makeup piping (on the 100 ft. elevation), the temperature and humidity are expected to be close to outside ambient conditions. Also, the large volume of the Fuel Building acts as a thermal reservoir and the large surface area allows for condensation to occur. Both of these features provide thermal benefits that limit the increase in temperature during time periods when actions within the building would occur.

Since only a brief time is required for operators to connect the hoses, operator exposure to any adverse temperature and humidity impacts at the alternate connection location will be minimal. A pump staging area is designated that is outside the Fuel Building as shown in Figure 3-2 of the OIP.

The primary connection point is located on the north side of the Fue Building as shown in Figure 3-11 of the OIP and does not require access to the Fuel Building to connect equipment. Both connection points will be designed to meet the postulated beyond-design-basis external event conditions described in NEI 12-06 (Reference 12) as applicable to PVNGS.

Appropriate staffing levels for listed actions are being coordinated with the site staffing study relating to the RAI on Recommendation 9.3, dated March 12, 2012 (Reference 8).

The Phase 2 Staffing Study required by Recommendation 9.3 is expected to be submitted in 2014 and will further address resources to implement FLEX strategies.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE FIGURES PLANi NORTH TRI'%

tORTH ROLL-UP DOOR-1FORMI EL.1 1OLOd' 400 UNIT I

-600 UNIT 2 800 UNIT3 CASK HEAD LAYDOWN.

FLOOR EL. 1134-0" LADDER-SPLASH CURTAIN-SPACE RESERVED FOR FUTURE HANDLING SLEEVE-(STORED)

L Figure RAI-41 Alternate Connection Point Location - Plan View Elevation 100'-0" (Markup of Reference 13) 56 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE SPLASH I CURTAIN, "XCAUST ESSENTIAL -----.

kIR FILTRATION UNIT F-HFA-JOt (0IM)

ýI.VA.C. MAINTENANCE lATCH ,. .... ,*

IAlternate Connection Point FL. EL99 1!- 6"._" .

HFL.C.

EL.

Figure RAI-41 Alternate Connection Point Location - Section View Facing Plant North (Markup of Reference 14) 57 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE N

Figure RAI-41 SFP Operating Floor and Roof Elevations (Markup of Reference 14) 58 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-42 Page 45 of the submittal dated February28, 2013, states that diesel driven pumps will be used to deliver the required flow rate through monitor type nozzles to provide water to the spent fuel pool. Provide a discussion on the diesel fuel oil supply (e.g., fuel oil storage tank volume, supply pathway, etc.) for the diesel driven pumps and how continued operation to ensure core and spent fuel pool cooling is maintainedindefinitely (i.e., Phase 2 and 3).

APS Response:

The initial strategy is to fill the phase 2 diesel driven SFP make-up pump from a selected day tank. Each day tank in the diesel building has a capacity of 1,100 gallons and a Technical Specification minimum volume of 550 gallons. The diesel driven pumps and smaller generators (120 VAC) will be filled using portable fuel containers. These fuel containers will be hand carried to the equipment deployment locations. These containers are filled from the diesel day tank using a hose attached to the day tank drain line.

Additionally, a modification is being planned to provide a connection point at the ground level in order to attach a hose, which will be used primarily to fill the MV FLEX (480 VAC) portable generators.

The diesel driven pumps for SFP makeup are not needed for 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months . At that time, additional personnel will be available to set up and fuel this equipment. Additionally, after 24 hours2.777778e-4 days 0.00667 hours 3.968254e-5 weeks 9.132e-6 months , fuel deliveries to the site, if needed, can be arranged to maintain on-site fuel supplies. Because the portable pumps do not have a recirculation feature they will be operated in a batch method to raise SFP and SG levels when needed. When they are stopped, at the top of the level band, the pumps may be refueled.

Per page 54 of the OIP, the phase 2 MV FLEX generators will be fueled with a gravity-fed hose from either of the two safety-related diesel day tanks located in the nearby diesel building. Each MV FLEX generator will be filled with 250 gallons using 550 gallons from one day tank and leave the other day tank full to allow recovery of the installed Class 1E generators. The MV FLEX generators will consume 36 gal/hr of fuel at 100% load; therefore, 250 gallons will last approximately 7 hours8.101852e-5 days 0.00194 hours 1.157407e-5 weeks 2.6635e-6 months before requiring refueling. Once the MV FLEX generators are running, the existing 480 V, 3 hp diesel fuel transfer pump will be available, allowing the day tanks to be refilled from the underground 84,000-gallon diesel fuel oil storage tanks. The 4,160 VAC diesel generators will be fueled in the same manner as the 480 VAC generators.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-43 Please provide further information, and identify the methods to be used which will provide the minimum flow rates necessary for the SFP sprays, and account for the rates requiredfor boil off due to the design basis heat load, and postulated losses due to leakage.

APS Response:

The make-up flow rate requirement for the SFP at maximum decay heat is 200 gpm. The make-up flow rate requirement for the SFP due to boil off rate at maximum decay heat is approximately 100 gpm. The maximum leakage rate from the SFP gate seals is assumed to be 56 gpm. In total, the minimum make-up pump flow rate should be approximately 160 gpm. A safety factor is added to this value so that the recommended make-up pump flow rate is 200 gpm. This is consistent with the minimum 200 gpm flow rate specified by NEI 12-06, Table D-3.

Redundant 4-inch pipe routings lead to two separate 3-inch sparger lines, which could provide make-up water to the SFP. Each 3-inch sparger line has 4 nozzles which discharge water into the SFP. One of the flow path connections is located near the Fuel Building roll-up door. The second flow path connection is located outside the Fuel Building. Only one flow path would be used, therefore each system is independent and sized to supply 200 gpm. This flow is supplied from either the CST or RWT via fire hose, which is connected to the suction side of the pump. The pump discharge is connected to the fixed piping at the 100 ft. elevation, eliminating the need to access the SFP operating floor (140 ft. elevation).

The discharge nozzles will be in a fixed position at an angle which is selected to ensure sprays do not overshoot the SFP. The ends of the nozzles will be approximately three feet.

from the near edge of the SFP and approximately 11 ft. above. Given a flow rate of approximately 50 gpm per nozzle and an orifice diameter of 1 inch, the stream will have ample velocity to cover the horizontal distance to reach the SFP.

Each flow path is designed for a 200 gpm flow rate and has a ball valve in the flow path to provide simple flow control (i.e., less flow) if required. It is not the intention of the design to provide precise flow control, only to provide simple reduction in flow if necessary. The pressure drop in each line is calculated at 200 gpm with the valve full open, and the pumps are sized appropriately to accommodate this design point. Procedural controls will be established to batch fill the SFP between level 2 (10 feet above the top of the fuel storage rack) and level 1 (23 feet 4.5 inches above the top of the fuel storage racks) as discussed in NEI 12-02, Industry Guidance for Compliance with NRC Order EA-12-051, 'To Modify Licenses with Regard to Reliable Spent Fuel Pool Instrumentation,' Revision 1, dated August 24, 2012.

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ENCLOSURE APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE 049-RAI-Palo Verde-44 Please provide further information that will clarify whether PVNGS uses heat tracing for freeze protection to conform to NEI 12-06, Section 3.2.2, guideline (12) as endorsed by JLD-ISG-2012-01.

APS Response:

As described in the OIP (page 11 of 119) PVNGS is exempt from extreme cold; therefore, freeze protection is not required.

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APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE ATTACHMENT 1 ACRONYMS 62 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE ATTACHMENT 1 ACRONYMS Acronym Definition AC alternating current ADV atmospheric dump valve AFW auxiliary feedwater AO Auxiliary Operator APS Arizona Public Service Company American Society of Heating, Refrigerating and Air Conditioning Engineers BDBEE beyond-design-basis external event CBO control bleed off CENTS Combustion Engineering Nuclear Transient Simulator CET core exit thermocouple CFR Code of Federal Regulations CRE control room envelope CST condensate storage tank CT condensate transfer system CVCS chemical and volume control system DC direct current ECW essential cooling water EFPD effective full power days EFPY effective full power year ELAP extended loss of all AC power EOP emergency operating procedure EPRI Electric Power Research Institute EQ environmentally qualified ERO emergency response organization ESP essential spray pond FLEX Diverse and Flexible Coping Strategies FSG FLEX support guideline Generation of Thermal-Hydraulic Information for Containments HDPE high density polyethylene HPSI high pressure safety injection HVAC heating, ventilation, and air conditioning IEEE Institute of Electrical and Electronics Engineers LPSI low pressure safety injection LUHS loss of ultimate heat sink MAAP modular accident analysis program MCC motor control center MSIS Main Steam Isolation Signal MSIV main steam isolation valve MSSS main steam support structure MSSV main steam safety valve MV medium voltage NEI Nuclear Energy Institute NRC Nuclear Regulatory Commission 63 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE ATTACHMENT 1 ACRONYMS Acronym Definition NSSS nuclear steam supply system OBE operating basis earthquake PC Spent fuel pool cooling system PD positive displacement PMP probable maximum precipitation PWROG Pressurized Water Reactor Owners Group PVNGS Palo Verde Nuclear Generating Station PWR pressurized water reactor RCP reactor coolant pump RCS reactor coolant system RRC Regional Response Center RVLMS reactor vessel level monitoring system RWMT reactor makeup water tank RWT refueling water tank SAFER Strategic Alliance for FLEX Emergency Response SBO station blackout SBOG station blackout generator SDC shutdown cooling SDR standard dimension ratio SFP spent fuel pool SG steam generator SHA seal housing assembly SIT safety injection tank SSC systems, structures and components SSE safe shutdown earthquake TDAFWP turbine driven auxiliary feedwater pump UFSAR Updated Final Safety Analysis Report UHS ultimate heat sink 64 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE ATTACHMENT 2 REFERENCES 65 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED

APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE ATTACHMENT 2 REFERENCES

1. American Society of Heating, Refrigeration, and Air Conditioning Engineers (ASHRAE) Weather Station Data, Luke AFB/Phoenix, AZ, USA, WMO#722785, 2009 ASHRAE Handbook - Fundamentals.

2. Palo Verde Nuclear Generating Station (PVNGS) Design Criteria Manual Part II, PlantDesign General Design CriteriaRev. 19.

3. Palo Verde calculation 13-MC-SG-0314, Nitrogen tank pressure requirement for ADVs.

4. Palo Verde administrative procedure 40EP-9EO08, "BLACKOUT."

5. Nuclear Regulatory Commission (NRC) Safety Evaluation Report (SER) letter, "Revised Station Blackout Coping Duration," October 31, 2006.

6. Arizona Public Service (APS) Document 791S-9ZZ07, Rev. 0, "PVNGS Extended Loss of All Site AC Guideline," DRAFT.

7. APS Letter to US NRC 102-06670-DCM/MAM, "Palo Verde Nuclear Generating Station (PVNGS) Units 1, 2, and 3 Docket Nos. STN 50-528, 50-529, and 50-530 APS Overall Integrated Plan in Response to March 12, 2012 Commission Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events (Order Number EA-12-049)," February 28, 2013, (ADAMS Accession Number ML13136A022).

8. NRC Letter, "Request for Information Pursuant to Title 10 of the Code of Federal Regulations 50.54(f), Regarding Recommendations 2.1, 2.3, and 9.3 of the Near-Term Task Force Review of Insights from the Fukushima Dai-ichi Accident," March 12, 2012, (ADAMS Accession Number ML12053A340).

9. Nuclear Management and Resources Council (NUMARC) 87-00, Rev 1, Guidelines and Technical Bases for NUMARC Initiatives Addressing Station Blackout at Light Water Reactors, August 1991.

10. Electric Power Research Institute (EPRI) Report NP-6041-SL Revision 1, "A Methodology for Assessment of Nuclear Plant Seismic Margin", August 1991.

11. Letter, PVNGS to US NRC, "Response to NRC Request for Additional Information (RAI) Regarding Revised Station Blackout Evaluation," PVNGS Letter No.

102-05513-CE/SAB/DJS, June 9, 2006.

12. Nuclear Energy Institute (NEI) 12-06, Revision 0, Diverse and Flexible Coping Strategies (FLEX) Implementation Guide, August 2012 (ADAMS Accession Number ML12242A378).

13. PVNGS Drawing 13-P-ZFL-501, Revision 14, "Fuel Building Equipment Locations Plans," September 8, 2010.

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APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE ATTACHMENT 2 REFERENCES

14. PVNGS Drawing 13-P-ZFL-502, Revision 12, "Fuel Building Equipment Locations Sections," September 20, 2006.

15. NRC Order Number EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-BasisExternal Events, March 12, 2012.

16. Non-Uniform Steam Generator U-Tube Flow Distribution During Natural Circulation Tests in ROSA-IV Large Scale Test Facility," Kukita et al, Nuclear Science and Engineering Vol 99, 1988 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML13136AO22).

17. Westinghouse Report WCAP-16175-P-A, Revision. 0, Model for Failureof RCP Seals Given Loss of Seal Cooling in CE NSSS Plants, April 2007.

18. Sulzer Bingham Pumps Inc. Document E12.5.387, Seal Flow and Leakage Report for Seal Retrofit for Reactor Coolant Pumps at the Palo Verde Nuclear Generating Station SBPI seal type RCR950B-3, July 1996.

19. Westinghouse Report WCAP-17601-P, Revision 1, Reactor Coolant System Response to the Extended Loss of AC Power Event for Westinghouse, Combustion Engineering and Babcock & Wilcox NSSS Designs, January 2013.

20. Brookhaven National Labs (BNL) Technical Report W6211-08/99, "Guidance Document for Modeling of RCP Seal Failures," August 1999.

21. Westinghouse Report CEN-152, Revision. 6.0, "Emergency Procedure Guidelines" December 2012.

22. Westinghouse Analysis Report DAR-TDA-12-2, Revision. 0, "Palo Verde Units 1, 2 &

F3 Beyond Design Bases Event - Extended Loss of AC Power," December 2012.

23. Westinghouse Letter LTR-PCSA-12-78, Rev. 0, "Transmittal of PA-PSC-0965 Core Team PWROG Core Cooling Management Interim Position Paper," November 9, 2012.

24. Westinghouse Calculation CN-FSE-12-10, Rev. 0, "Palo Verde Units 1, 2 and 3 Reactor Coolant System (RCS) Inventory, Shutdown Margin, and Mode 5/6 Boric Acid Precipitation Control (BAPC) Analyses to Support the Diverse and Flexible Coping Strategy (FLEX)," February 15, 2013.

25. Westinghouse Calculation CN-SEE-II-12-33, Rev. 1, "APS Palo Verde Nuclear Generation Station FLEX Conceptual Design AFT Fathom Models," April, 3, 2013.

26. Palo Verde Nuclear Generating Station Units 1, 2, and 3 "Updated Final Safety Analysis Report," Revision 16, June 2013.

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APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE ATTACHMENT 2 REFERENCES

27. NUREG/CR-1699, "Modes of Circulation in an Inverted U-Tube Array with Condensation," Griffith, Calia, October 1980

28. TR-FSE-13-6, Rev. 0, "Palo Verde Nuclear Generating Station FLEX Integrated Plan," February 2013.

29. EPRI NP-3471, "Experimental Data Report on Condensation in a Single Inverted U-tube," Banerjee, Nyguyen, May 1984.

30. APS Letter, 162-13357-PSH, Rev. 0, "Data Transmittal of Requested Physics Data for Palo Verde Unit 3, Cycle 16, End of Cycle to Support Station Blackout Coping Evaluations."

31. EGG-SEMI-5549, "Quick Look Report for SEMISCALE Mod-2A Test S-NC-4," D. J.

Shimeck et al, August 1981.

32. JLD-ISG-2012-01, Rev. 0, "Compliance with Order EA-12-049, Order Modifying Licenses with Regard to Requirements for Mitigation Strategies for Beyond-Design-Basis External Events," August 2012 (ADAMS Accession No. ML12229A174).

33. NRC Report NUREG-0578, "TMI-2 Lessons Learned Task Force Status Report and Short-Term Recommendations," July 1979 (ADAMS Acession No. ML090060030).

34. Oak Ridge National Laboratory Radiation Safety Computational Center Code Package CCC-750, "SCALE 6: Standardized Computer Analyses for Licensing Evaluation Modular Code System for Workstations and Personal Computers, Including ORIGEN-ARP," August 2009.

35. APS Letter 448-00774, "Transmittal of data to be used in ORIGEN-ARP SCALE package for best estimate decay heat model for the Palo Verde Nuclear,"

H. Mortazavi, July 11, 2012.

36. American Nuclear Society, ANSI/ANS-5.1-1979, "Decay Heat Power in Light Water Reactors," August 1979.

37. Palo Verde Nuclear Generating Station Units 1, 2, and 3 Renewed Operating License (Through Amendment Nos. 191), July 3, 2013.

38. Westinghouse Report LOCA-75-127-NP, Revision 0, "Post LOCA Boric Acid Mixing Equipment." [ADAMS Accession Number ML11167A116]

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APS RESPONSE TO RAI REGARDING THE PVNGS OIP FOR NRC ORDER EA-12-049, MITIGATING STRATEGIES FOR BDBEE ATTACHMENT 3 ESSENTIAL LOAD LIST WITH CRITICAL SAFETY FUNCTION (FROM ENGINEERING STUDY 13-NS-A108, APPENDIX E) 69 ATTACHMENTS 4 AND 5 OF THE ENCLOSURE CONTAIN Proprietary and Security-Related Information - Withhold under 10 CFR 2.390 UPON SEPARATION THIS PAGE IS DECONTROLLED