2CAN121302, Response to Request for Additional Information Adoption of National Fire Protection Association Standard NFPA-805

Response to Request for Additional Information Adoption of National Fire Protection Association Standard NFPA-805

ML13338A432
Person / Time
Site:	Arkansas Nuclear
Issue date:	12/04/2013
From:	Jeremy G. Browning Entergy Operations
To:	Document Control Desk, Office of Nuclear Reactor Regulation
References
2CAN121302
Download: ML13338A432 (20)

Text

s Entergy Operations, Inc.

1448 S.R. 333 Russellville, AR 72802 Tel 479-858-3110 Jeremy G. Browning Vice President - Operations Arkansas Nuclear One 2CAN121302 December 4, 2013 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

SUBJECT:

Response to Request for Additional Information Adoption of National Fire Protection Association Standard NFPA-805 Arkansas Nuclear One, Unit 2 Docket No. 50-368 License No. NPF-6

REFERENCES:

1. Entergy letter dated December 17, 2012, License Amendment Request to Adopt NFPA-805 Performance-Based Standard for Fire Protection for Light Water Reactor Electric Generating Plants (2001 Edition) (2CAN121202)

(ML12353A041)

2. NRC letter dated September 11, 2013, Arkansas Nuclear One, Unit 2 -

Request for Additional Information Regarding Adoption of National Fire Protection Association Standard NFPA-805 (TAC No. MF0404)

(2CNA091301) (ML13235A005)

3. Entergy letter dated November 7, 2013, Response to Request for Additional Information - Adoption of National Fire Protection Association Standard NFPA-805 (2CAN111301) (ML13312A877)

Dear Sir or Madam:

By letter dated September 11, 2013 (Reference 2), the NRC requested additional information associated with the Entergy Operations, Inc. (Entergy) request to amend the Arkansas Nuclear One, Unit 2 (ANO-2) Technical Specifications (TS) and licensing bases to comply with the requirements in 10 CFR 50.48(a), 10 CFR 50.48(c), and the guidance in Regulatory Guide (RG) 1.205, Risk-Informed Performance-Based Fire Protection for Existing Light-Water Nuclear Power Plants. The amendment request followed Nuclear Energy Institute (NEI) 04-02, Guidance for Implementing a Risk-Informed, Performance-Based Fire Protection Program under 10 CFR 50.48(c). This submittal described the methodology used to demonstrate compliance with, and transition to, National Fire Protection Association (NFPA)-805, and included regulatory evaluations, probabilistic risk assessment (PRA), change evaluations, proposed modifications for non-compliances, and supporting attachments.

2CAN121302 Page 2 of 3 Based on the complexity of the questions included in the Reference 2 RAI, the NRC established response due-dates of 60, 90, or 120 days, from the date of the Reference 2 letter. Entergy letter dated November 7, 2013 (Reference 3), provided the 60-day RAI responses, one 90-day Fire Modeling RAI response, and four 90-day PRA RAI responses. Enclosed are responses to the remaining questions having a 90-day response requirement.

A change to Table 4-3 and Attachment C of the original Entergy letter (Reference 1) is also included in the attachment. Entergy requests this change be considered in conjunction with the NRCs review of the RAI responses.

Changes or additional information, as detailed in this letter, with respect to the original Entergy request (Reference 1) have been reviewed and Entergy has determined that the changes do not invalidate the no significant hazards consideration included in the Reference 1 letter.

In accordance with 10 CFR 50.91(b)(1), a copy of this application and the reasoned analysis about no significant hazards consideration is being provided to the designated Arkansas state official.

No new commitments have been identified in this letter.

If you have any questions or require additional information, please contact Stephenie Pyle at 479-858-4704.

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

Executed on December 4, 2013.

Sincerely, ORIGINAL SIGNED BY JEREMY G. BROWNING JGB/dbb

Attachment:

90-Day Responses to Request for Additional Information - ANO-2 Transition to NFPA-805

2CAN121302 Page 3 of 3 cc: Mr. Marc L. Dapas Regional Administrator U. S. Nuclear Regulatory Commission Region IV 1600 East Lamar Boulevard Arlington, TX 76011-4511 NRC Senior Resident Inspector Arkansas Nuclear One P. O. Box 310 London, AR 72847 U. S. Nuclear Regulatory Commission Attn: Mr. Kaly Kalyanam MS O-8B1 One White Flint North 11555 Rockville Pike Rockville, MD 20852 Mr. Bernard R. Bevill Arkansas Department of Health Radiation Control Section 4815 West Markham Street Slot #30 Little Rock, AR 72205

Attachment to 2CAN121302 90-Day Responses to Request for Additional Information ANO-2 Transition to NFPA-805

Attachment to 2CAN121302 Page 1 of 16 90-Day Responses to Request for Additional Information ANO-2 Transition to NFPA-805 By letter dated September 11, 2013 (Reference 2), the NRC requested additional information associated with the Entergy Operations, Inc. (Entergy) request (Reference 1) to transition the Arkansas Nuclear One, Unit 2 (ANO-2), fire protection licensing basis to National Fire Protection Association (NFPA) Standard NFPA-805, Performance-Based Standard for Fire Protection for Light Water Reactor Electric Generating Plants (2001 Edition). Entergy letter dated November 7, 2013 (Reference 3), provided the 60-day request for additional information (RAI) responses, one 90-day Fire Modeling RAI response, and four 90-day PRA RAI responses.

Included below are Entergy responses to the remaining questions requiring a 90-day response.

The respective question is included for convenience.

Note: All Fire Protection Engineering (FPE), Programmatic, and Radioactive Release responses associated with the aforementioned RAI were submitted in Entergys 60-day response letter (Reference 3).

Safe Shutdown Analysis (SSA)

Note: All SSA responses, except SSA RAI 01 and SSA RAI 05, were submitted in Entergys 60-day response letter (Reference 3).

SSA RAI 01 LAR Attachment B references the following documents relative to demonstrating alignment with NFPA-805, Section 2.4.2, Nuclear Safety Capability Assessment (NSCA):

a. CALC-85-E-0087-01, Safe Shutdown Capability Assessment (SSCA)

b. CALC-85-E-0087-23, Safe Shutdown Equipment List (SSEL) Methodology

c. CALC-85-E-0087-24, Safe Shutdown Cable Analysis

d. CALC-85-E-0086-02, Manual Action Feasibility Methodology and Common Results These calculations address current Appendix R compliance but contain little or no reference relative to compliance with NFPA-805. Provide additional discussion of how these documents support meeting NFPA-805, Section 2.4.2, what changes are necessary for transition, and the status of NFPA-805 nuclear safety capability analyses if different from the results presented in these documents.

Response

The methodology and the subsequent analyses used in the current Appendix R Safe Shutdown Capability Assessment (SSCA) meet NFPA 805, Section 2.4.2 for a Nuclear Safety Capability Assessment (NSCA).

The steps used at ANO-2 for the existing Appendix R SSCA follow the same methodology for performing a NSCA in accordance with NFPA 805. The acceptability for transition of the ANO-2 methodology to NFPA 805 is documented within both LAR Attachment B, NEI 04-02 Table B-2

Attachment to 2CAN121302 Page 2 of 16 Nuclear Safety Capability Assessment Methodology Review, and engineering report, CALC-ANO2-FP-09-00032, ANO-2 Transition NSCA Methodology. The conclusion of this engineering report is that the ANO-2 methodology aligns with the guidance in NEI 00-01 and, therefore, NFPA 805 Section 2.4.2. Editorial revisions to the existing Appendix R documents are needed to reflect terminology and definitions used for an NFPA 805 licensing basis.

The existing ANO-2 Appendix R analysis conservatively bounds a transition to an NFPA 805 NSCA as there are no new credited systems in the current as-built design of ANO-2 or expansions of these system boundaries. The systems and equipment in the ANO-2 SSCA selected to meet Appendix R criteria and time constraints to be in Cold Shutdown (CSD),

Mode 5, within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> bounds the NFPA 805 defined safe and stable condition of Hot Standby (Mode 3) for ANO-2. A detailed discussion of safe and stable for ANO-2 is provided in Section 4.2.1.2 of the ANO-2 LAR (Reference 1) for transition to NFPA 805.

The new Auxiliary Feedwater (AFW) system and equipment to be installed (Reference 1 LAR Attachment S, Item S1-11) will require revision of these documents during the design/modification process, but has no immediate impact that would preclude transition to NFPA 805. Low-pressure systems in the Appendix R analysis that interface to the RCS needed for CSD and in the current CALC-09-E-0008-02, ANO-2 NFPA 805 Non Power Operations Assessment, will be subject to removal from the subject documents, but are not required to be removed prior to transition.

SSA RAI 05 NFPA-805, Section 1.1, states, "This standard specifies the minimum fire protection requirements for existing light water nuclear power plants during all phases of plant operation, including shutdown, degraded conditions, and decommissioning." Please provide the following pertaining to non-power operations (NPO) discussions provided in Section 4.3 and Attachment D of the LAR:

a) Provide additional description of the six shutdown conditions used in the outage management process to define risk of operations.

Response

Procedure OP-1015.048, Shutdown Operations Protection Plan, defines six conditions based upon fuel location, Reactor Coolant System (RCS) integrity, and available inventory of the RCS and Fuel Transfer Canal (FTC). The six shutdown conditions from low to high risk are:

1. The reactor vessel defueled with all fuel in the spent fuel pool.

2. FTC is flooded greater than 23 above the core with fuel in the vessel and no refueling in progress.

3. FTC is flooded greater than 23 above the core with fuel in the vessel and refueling is in progress.

4. RCS is intact with fuel in the vessel and the RCS level is greater than 377 10.5 (reactor vessel flange).

Attachment to 2CAN121302 Page 3 of 16

5. RCS is open with fuel in the vessel, the RCS level is greater than 377 10.5, and FTC level is less than 23.

6. RCS is open, with fuel in the vessel, and the RCS level is in a lowered inventory condition less than 377 10.5.

b) Section 4.3.2 and Attachment D of the LAR states that for those components which had not previously been analyzed in support of the at-power analysis, the equipment was evaluated and added to the Plant Data Management System (PDMS). The LAR stated that all new circuit analyses were performed in accordance with existing methodologies established at ANO consistent with the guidance in NEI 00-01. Provide a list of the additional components and a list of those at-power components that have a different functional requirement for NPO. Describe the difference between the at-power safe shutdown function and the NPO function. Include with this list a general description by system indicating why components would be selected for NPO and not be included in the at-power analysis.

Response

Section 4.6 of CALC-09-E-0008-02, ANO-2 NFPA 805 Non-Power Operations Assessment, provides a listing of equipment that is not currently part of the safe shutdown program, but required to support NPO. A listing of this additional equipment is provided below with discussion of why each is included in NPO and not at-power. Attachment 8.38, included in CALC-09-E-0008-04, ANO-2 NFPA 805 Fault Tree and PID Attachments, is the compiled NPO Equipment List for ANO-2 and has nominally 167 pieces of equipment listed with functional requirements at power, Hot Shutdown (HSD), Cold Shutdown (CSD), and for NPO.

Support equipment (electrical, service water) that is in the NPO list has the same requirement for safe and stable. RCS interface valves to low pressure Shutdown Cooling (SDC) systems normally closed at power will have an open NPO position.

List of Additional Components for which Cable Selection was Performed Equipment ID Equipment Description Discussion This motor-operated valve (MOV) is in the recirculation line associated with Containment Spray Pump 2P-35B. Closure of this MOV is 2P-35B to Refueling required for NPO if 2P-35B is used for SDC 2CV-5672-1 Water Tank (RWT) when Low Pressure Safety Injection (LPSI)

Recirculation Isolation pump 2P-60B is out of service for maintenance.

2P-35B is secured post-fire following a reactor trip to prevent pumping down the RWT.

This MOV is in the recirculation line associated with Containment Spray Pump 2P-35A. Closure of this MOV is required for NPO if 2P-35A is 2P-35A to RWT 2CV-5673-1 used for SDC when LPSI pump 2P-60A is out of Recirculation Isolation service for maintenance. 2P-35A is secured post-fire following a reactor trip to prevent flow diversion.

Attachment to 2CAN121302 Page 4 of 16 Equipment ID Equipment Description Discussion This MOV is included in NPO due to a potential Safety Injection System drain path. High Pressure Safety Injection (SIS) HPSI Header 1 to 2CV-5105-1 (HPSI) is secured following a reactor trip due to Reactor Drain Tank fire and charging is the credited makeup path for (RDT)

ANO-2.

This MOV is included in NPO due to a potential SIS HPSI Header 2 to drain path. HPSI is secured following a reactor 2CV-5106-2 RDT trip due to fire and charging is the credited makeup path for ANO-2.

This MOV included in NPO due to a drain path back to the RWT when combined with a 2P-89A to RWT spurious start of the associated HPSI pump 2CV-5126-1 Recirculation Isolation 2P-89A. HPSI secured following a reactor trip due to fire and charging is the credited makeup path for ANO-2.

This MOV included in NPO due to a drain path back to the RWT when combined with a 2P-89B to RWT spurious start of the associated HPSI pump 2CV-5127-1 Recirculation Isolation 2P-89B. HPSI secured following a reactor trip due to fire and charging is the credited makeup path for ANO-2.

This MOV included in NPO due to a drain path back to the RWT when combined with a 2P-89C to RWT spurious start of the associated HPSI pump 2CV-5128-1 Recirculation Isolation 2P-89C. HPSI secured following a reactor trip due to fire and charging is the credited makeup path for ANO-2.

RCS Refueling Level - RCS level instruments used only for NPO and 2LI-4791 Channel 1 not required at power.

RCS Refueling Level - RCS level instruments used only for NPO and 2LT-4791 Channel 1 not required at power.

RCS Refueling Level - RCS level instruments used only for NPO and 2LI-4792 Channel 2 not required at power.

RCS Refueling Level - RCS level instruments used only for NPO and 2LT-4792 Channel 2 not required at power.

Pressurizer Surge Line Sample line drain path normally isolated at 2SV-4639 Sample Valve power.

RCS Hot Leg Sample Sample line drain path normally isolated at 2SV-4665 Valve power.

Sample from Shutdown Sample line drain path normally isolated at 2SV-5655 Heat Exchanger power.

Attachment to 2CAN121302 Page 5 of 16 Equipment ID Equipment Description Discussion Sample from RWT Sample line drain path normally isolated at 2SV-5666 Recirculation Line power.

RCS Sample Isolation Sample line drain path normally isolated at 2SV-5833-1 Valve power.

Local temperature indication only credited for Shutdown Heat 2TI-5617 NPO. SDC is a low-pressure system not Exchanger 2E-35A Inlet credited at power.

Local temperature indication only credited for Shutdown Heat 2TI-5619 NPO. SDC is a low-pressure system not Exchanger 2E-35B Inlet credited at power.

Provision to allow 2X02 to be used for offsite ANO-2 Unit Aux 2X02 power during refueling outage if startup Transformer transformer is out of service for maintenance.

c) LAR Attachment D states the licensee followed the guidance of frequently asked questions (FAQ) 07-0040, "Non-Power Operations Clarifications" (ADAMS Accession No. ML082200528). Provide a list of key safety functions (KSF) pinch points by fire area that were identified in the NPO fire area reviews using FAQ 07-0040 guidance including a summary level identification of unavailable paths in each fire area. Describe how these locations will be identified to the plant staff for implementation.

Response

Section 6.1 of CALC-09-E-0008-02 contains all fire area evaluations for ANO-2 and clearly identifies Key Safety Function (KSF) pinch points. A summary level listing of KSF paths for each fire area due to NPO pinch points is included below. ANO-2 NFPA 805 LAR transition implementation Item S2-5 addresses incorporation of these insights from the ANO-2 NPO calculation into operating procedures. The operating procedure changes will provide necessary input to the plant staff for KSF pinch point issues.

Key Safety Function (KSF) Paths by Fire Area due to NPO Pinch Points Area ANO-2 KSF Pinch Point / Path Impact(s) 2MH01E Service Water - Swing pump alignment 2MH01W None - Deterministically compliant 2MH02E Service Water - Swing pump alignment 2MH02W None - Deterministically compliant 2MH03E Service Water - Swing pump alignment 2MH03W None - Deterministically compliant

Attachment to 2CAN121302 Page 6 of 16 Key Safety Function (KSF) Paths by Fire Area due to NPO Pinch Points Area ANO-2 KSF Pinch Point / Path Impact(s)

AA Service Water - Suction source through sluice gate AAC Service water - Discharge path alignment ADMIN None - Deterministically compliant CC None - Deterministically compliant Service water - Discharge path alignment, flow diversion Inventory - Borated water source isolated DD Shutdown Cooling (Decay Heat Removal) - Suction from RCS Reactivity - Non-borated water source FF None - Deterministically compliant GG Service Water - Discharge path realignment, flow diversion Service Water - Discharge path and flow alignment Inventory - Borated water source HH Shutdown Cooling - Suction from RCS Reactivity - Non-borated water source Electrical - Isolation of fire impacted switchgear II Service Water - Flow diversion Electrical - System alignment Service Water - Flow diversion JJ Shutdown Cooling - Suction from RCS Inventory - Makeup diversion path K None - Deterministically compliant KK None - Deterministically compliant L None - Deterministically compliant MM None - Deterministically compliant OO Service Water - Suction source through sluice gates QQ None - Deterministically compliant SS Service Water - Suction source through sluice gates, flow diversion

Attachment to 2CAN121302 Page 7 of 16 Key Safety Function (KSF) Paths by Fire Area due to NPO Pinch Points Area ANO-2 KSF Pinch Point / Path Impact(s)

Service Water - Flow diversion, discharge path alignment Inventory - Borated water source isolated TT Reactivity - Non-borated water source Instrumentation - Safety Parameter Display System (SPDS) computer room cooling YD None - Deterministically compliant Service Water - Discharge path alignment B-2 Reactivity - Non-borated water source Shutdown Cooling - Suction from RCS B-3 Service Water - Flow diversion B-4 None - Deterministically compliant B-5 None - Deterministically compliant Service Water - Discharge path to lake, flow diversion, suction source B-6 through sluice gate Inventory - Borated water source EE-L Shutdown Cooling - Suction from RCS EE-U None - Deterministically compliant Control Room Shutdown Cooling Inventory G

Service Water Lake Electrical Reactivity NN Shutdown Cooling - Diversion/Drain path

Attachment to 2CAN121302 Page 8 of 16 d) During NPO modes, spurious actuation of valves can have a significant impact on the ability to maintain decay heat removal and inventory control. Provide a description of any actions being credited to minimize the impact of fire-induced spurious actuations on power operated valves (e.g., air-operated valves and motor-operated valves) during NPO (e.g., pre-fire rack-out, actuation of pinning valves, and isolation of air supplies).

Response

Reviews of plant operating procedures were conducted to identify equipment that would be secured during NPO. Secured equipment that could challenge KSFs was included in the NPO equipment list and incorporated into the fault trees. Impacts to secured or pre-positioned equipment were assigned strategies in the fire area compliance assessments (CALC-09-E-0008-02, Attachments 8.1 through 8.34) reflecting prevention of undesired actuations. These strategies include pre-throttling to prevent failure on loss of instrument air and the racking down or opening of breakers preventing spurious operation. Section 4.5 of CALC-09-E-0008-02 explicitly indicates equipment procedurally pre-positioned for NPO.

e) During normal outage evolutions certain NPO credited equipment will have to be removed from service. Describe the types of compensatory actions that will be used during such equipment down-time.

Response

OP-1015.048, Shutdown Operations Protection Plan, contains guidance concerning management of risk during evolutions where equipment may be taken out of service as allowed by Technical Specifications.

Maintain Defense-in-Depth by alternate means when pre-outage planning reveals that specified systems, structures, or components will be unavailable.

Planning and scheduling outage activities in a manner that optimizes safety system availability.

Protect key plant equipment/systems/train while redundant or related equipment is out of service. Limiting access to these sensitive areas prevents introduction of transients and performance of risk significant tasks.

f) The description of the NPO review for the LAR does not identify locations where KSFs are achieved via RAs or for which instrumentation not already included in the at-power analysis is needed to support RAs required to maintain safe and stable conditions.

Identify those RAs and instrumentation relied upon in NPO and describe how RA feasibility is evaluated. Include in the description whether these variables have been or will be factored into operator procedures supporting these actions.

Response

Each fire area evaluation contained in Section 6.1 of CALC-09-E-0008-02 is either classified as deterministically compliant with all KSFs maintained or as being a pinch point due to one or more KSFs being impacted. In those areas that are not in deterministic compliance, an

Attachment to 2CAN121302 Page 9 of 16 assessment is performed to identify a set of equipment that could require recovery based upon a total fire area burn up with worse case failures postulated and all redundant paths and equipment failed. These defense-in-depth recoveries for NPO are considered feasible as they are a smaller set of the same actions used and previously evaluated by the manual action feasibility study CALC-85-E-0086-02 for Appendix R. Available instrumentation needed to support NPO is identified in the summary portion of each fire area evaluation in Section 6.1 of CALC-09-E-0008-02. This instrumentation is RCS level indication (inventory),

Neutron Monitoring (reactivity), and RCS temperature. The NPO calculation concluded in Section 2.0 that fire areas not in deterministic compliance are demonstrated to be acceptable with no credited recovery actions based upon defense-in-depth and a risk informed process.

The NPO calculation identifies one commitment to perform a plant modification (LAR Attachment S, Table S-1, Item S1-6). This modification addresses a potential IN 92-18 failure of MOVs in the single line from the RCS to the SDC system. This modification, with procedural controls, eliminates this vulnerability by eliminating spurious actuations and thereby eliminating potential recovery actions.

Fire Modeling Note: Fire Modeling RAIs 02, 03, and 05 responses were submitted in Entergys 60-day response letter (Reference 3). Fire Modeling RAIs 01, 04, and 06 are expected to be addressed in the 120-day RAI response. Therefore, no Fire Modeling responses are included in this letter.

Probabilistic Risk Assessment (PRA)

Note: PRA RAIs 01 (except 01d and 01gi), 02, 03, 04, 05, 06, 07, 09, 10, 11, 12, 13, 15, 18, and 19 responses were submitted in Entergys 60-day response letter (Reference 3).

PRA RAIs 01gi, 14, 16, and 17 are expected to be addressed in the 120-day RAI response. PRA RAIs 03 (results), 05 (results), 06 (results), 09 (results - not part of original response plan), and 10 (results), will be provided following completion of the Fire PRA model update or in conjunction with the response to future RAIs, if any.

PRA RAI 01 - Fire PRA Facts and Observations (F&Os)

Section 2.4.3.3 of NFPA-805 states that the probabilistic safety assessment (PSA is also referred to as PRA) approach, methods, and data shall be acceptable to the authority having jurisdiction, which is the NRC. RG 1.205 identifies NUREG/CR-6850 as documenting a methodology for conducting a fire PRA and endorses, with exceptions and clarifications, NEI 04-02, Revision 2, as providing methods acceptable to the staff for adopting a fire protection program consistent with NFPA-805. RG 1.200, "An Approach For Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities,"

describes a peer review process utilizing an associated ASME/ANS standard (currently ASME/ANS-RA-Sa-2009) as one acceptable approach for determining the technical adequacy of the PRA once acceptable consensus approaches or models have been established for evaluations that could influence the regulatory decision. The primary results of a peer review are the F&Os recorded by the peer review and the subsequent resolution of these F&Os.

Attachment to 2CAN121302 Page 10 of 16 Please clarify the following dispositions to fire F&Os and Supporting Requirement (SR) assessment identified in Attachment V of the license amendment request that have the potential to impact the fire PRA results and do not appear to be fully resolved:

d) FSS-B1-02 (Finding, Met at CC-I/II/III)

Appendix A of the Fire PRA summary report (PRA-A2-05-004) presents separate risk estimates for specific fire scenarios occurring in the Unit 1 and 2 Main Control Rooms (MCRs). Fire Area G appears to be defined as including the control rooms of both units (i.e., Fire Zones 2199-G and 129-F). Table W-2 of the LAR presents the risk estimates (i.e., CDF, LERF, CDF, and LERF) for Fire Area G, which presumably includes the contribution from the Unit 1 MCR. Aside from this, it is not clear to what extent fire in one control room impacts the opposite unit's control room and whether this has been fully addressed in the fire PRA. An exception to this is that the cited reference (AN02-FP-09-00013) presents a sensitivity study of failure of the glass partition between the MCRs on abandonment time and concludes there is little impact. Please explain:

i. How the impact of heat and smoke from fire in the Unit 1 MCR was addressed in the fire PRA for the Unit 2 MCR.

ii. How the potential for fire propagation from the Unit 1 to Unit 2 MCR was addressed.

Include description of the extent to which the two MCRs are connected.

iii. How the heating, ventilation, and air conditioning (HVAC) for the two MCRs are connected and how HVAC operation was considered in the fire PRA for the MCR.

iv. How fire frequency was assigned to Fire Zones 2199-G and 129-F.

Response

i. A Consolidated Model of Fire and Smoke Transport (CFAST) model was developed to evaluate the smoke and heat buildup through varying ventilation configurations, while accounting for the actual room geometry and the interconnecting communication of air flow between the two Control Rooms. Abandonment times were calculated based on the limiting habitability condition of either smoke (visibility) or heat. The various configurations, the output from the CFAST runs, and the resultant abandonment times are documented in CALC-ANO2-FP-09-00013, ANO-2 Control Room Abandonment Times. This calculation includes an evaluation of impact of a fire initiating in the ANO-2 MCR, as well as a fire initiating in the ANO-1 MCR, and the transfer of heat and smoke to the ANO-2 MCR. The impact of the ANO-1 MCR fire on the ANO-2 abandonment times and abandonment frequency calculation is evaluated in the same manner as the ANO-2 MCR fire impact on ANO-2 Control Room abandonment. The total abandonment frequency is the sum of the abandonment frequency from a fire in the ANO-1 and ANO-2 Control Rooms.

ii. The potential for actual fire propagation, rather than smoke or heat spread, from the ANO-1 MCR to the ANO-2 MCR in a manner that would damage cables in panels in the ANO-2 MCR is implausible unless the glass window in the partition separating the two Control Rooms were to break. The Control Rooms are separated by a solid concrete wall and a glass wall. The glass wall includes louvers near the top of the wall which allow for air flow between the units. This communication of air volumes is included in the

Attachment to 2CAN121302 Page 11 of 16 Control Room abandonment calculation modeling. Damage to cables in the opposite unit Control Room is equivalent to damage to sensitive electronics in a panel, which is being addressed via a draft FAQ (FAQ 13-004). In the evaluation supporting this draft FAQ, a transient fire external to a panel does not cause the sensitive electronics within the panel to exceed the thermoset cable damage criteria. Therefore, a fire in the ANO-1 MCR separated from the ANO-2 MCR by a glass wall and a distance of over 2 from the glass wall (distance from the nearest panel to the glass wall in either Control Room) will not result in damage to cables or sensitive electronics in a panel in the ANO-2 MCR. A sensitivity study in CALC-ANO2-FP-09-00013, ANO-2 Control Room Abandonment Times, has evaluated the impact of the glass partition breaking as a result of the fire in the opposite Control Room.

iii. The ANO-1 and ANO-2 Control Rooms have separate HVAC systems. Ventilation louvers in the glass wall between the two Control Rooms allow air flow between the Control Rooms. Thus, the pressure differential caused by a fire in one Control Room would force air into the opposite Control Room. This configuration is included in the CFAST model in CALC-ANO2-FP-09-00013, ANO-2 Control Room Abandonment Times. This analysis also includes HVAC as a configuration parameter that is varied.

Each fire configuration case is evaluated with and without HVAC operational. The Control Room abandonment scenario partitions the loss of HVAC in a 90/10 split. This is a valid estimation given that HVAC will only be lost in fires in the HVAC control panel and panels which cause loss of associated power supplies. As such, HVAC is assumed to remain available in 90% of the fires.

An additional ventilation configuration exists called the Emergency Recirculation Mode which is designed to isolate the two Control Rooms from their normal ventilation systems in the event of an emergency outside of the MCR (smoke, chlorine, or radiation). In this configuration, emergency HVAC units are used to circulate and cool or heat the air within the combined Control Room envelope to permit a habitable atmosphere for MCR personnel. Since this configuration would only be used for events occurring outside the Control Rooms, it would not be in use during a fire in either Control Room. Therefore, it was not modeled in the MCR abandonment analysis.

iv. The fire ignition frequency for 2199-G and 129-F is calculated in the same manner as the fire ignition frequency for other fire compartments at ANO. The fire ignition frequencies were developed using the NUREG/CR-6850 Supplement 1 generic fire ignition frequencies for ignition sources located within the Control Room. The ignition sources located within the Control Room include, Bin 4 (Main Control Board), Bin 15 (Electrical panels), Bin 26 (Ventilation Subsystems), and the Control Room transient fire frequencies. The frequencies are evaluated per NUREG/CR-6850 based on source count walk-downs and transient weighting factors for both units and partitioned out based on the number of ignition sources located within the Control Room. A Bayesian update is performed to update the generic frequencies based on ANO operating and fire events data.

Attachment to 2CAN121302 Page 12 of 16 PRA RAI 08 - MCR Fire Modeling Section 2.4.3.3 of NFPA-805 states that the PRA approach, methods, and data shall be acceptable to the NRC. RG 1.205 identifies NUREG/CR-6850 as documenting a methodology for conducting a fire PRA and endorses, with exceptions and clarifications, NEI 04-02, Revision 2, as providing methods acceptable to the staff for adopting a fire protection program consistent with NFPA-805. In letter dated July 12, 2006, to NEI (ADAMS Accession No. ML061660105), the NRC established the ongoing FAQ process where official agency positions regarding acceptable methods can be documented until they can be included in revisions to RG 1.205 or NEI 04-02. Methods that have not been determined to be acceptable by the NRC Staff require additional justification to allow the NRC Staff to complete its review of the proposed method.

The Fire Scenario report (PRA-A2-05-003) appears to indicate that propagation of fires between adjacent cabinets in the Main Control Room was not evaluated. Section, 2.1, Assumption #4, of that report states that for electrical fire inside the control room, the fire is expected to be contained within the panel" and "f[F]or large, controllable fires, the frequency is captured in the control room abandonment scenario." Assumption #5 states that half the panels were assumed to involve a single cable bundle and half multiple bundles. Please:

a) Explain the extent to which propagation of fires between adjacent cabinets in the MCR was evaluated and provide justification for this level of treatment.

b) Include in the explanation, a discussion of the physical separation between Main Control Board and back panels, and indicate whether they consist of single or double walls.

c) Justify the assumption that half the fire frequency is assigned to multiple bindle fires, and half is assigned to single bundle fires.

Response

a) Propagation of an electrical cabinet fire to an adjacent electrical cabinet was modeled in the ANO-2 Fire PRA as follows:

i. For most of the non-abandonment Control Room scenarios, fire propagation was limited to the cabling within the enclosure boundaries of the source cabinet. The cabinet is considered an adjacent cabinet if the cabinet is separated from the source cabinet. Each cabinet was modeled as its own scenario without propagation to the adjacent cabinets since the cabinets are separated by double walls and an air gap.

The Control Room cabinets are not open and cannot expose an adjacent cabinet to the source heat flux without first penetrating through the source cabinet walls and the adjacent cabinet walls.

This treatment is consistent with the criteria specified in Appendix S of NUREG/CR-6850 which states, Fire spread to an adjacent cabinet was prevented if the cabinets were separated by a double wall with an air gap.

Therefore, the guidance provided in Chapter 11 of NUREG/CR-6850, Page 11-39 is applicable: For cabinets with a double wall separated by an air gap and back covers, as suggested in Appendix S, it can be assumed that the fire would not propagate between the cabinets.

Attachment to 2CAN121302 Page 13 of 16 In addition to the guidance listed in Appendix S and Chapter 11 of NUREG/CR-6850, the Control Room is constantly manned, resulting in a likelihood of early detection.

This allows quick and appropriate response to any fire scenario within the Control Room area and further limits the ability of a fire to propagate to an adjacent cabinet.

In limited cases, Control Room panel fires were conservatively assumed to spread to adjacent panels.

Two main control board (MCB) scenarios were evaluated: one in which the fire impacted the cabling and circuitry within Panels 2C01, 2C02, 2C03, 2C04, and 2C100, and one in which the fire impacted the cabling and circuitry within panel 2C09. The first MCB scenario conservatively assumed that the panels are not separated with double walls and an air gap, although each panel is an individual console, with its own outer walls. In the second MCB scenario, panel 2C09 (Chemical and Volume Control System panel, on the right-hand end of the MCB, beyond the Reactor Coolant System panel) was treated as a separate panel as described above.

Fires in Panels 2C10 (electrical auxiliary system panel) and 2C11 (turbine generator panel) were modeled as one because there is a six-inch opening between the panels.

Therefore, except in limited cases, the definitions for each single Control Room fire scenario include the cable targets within the cabinet outer boundaries. Using the guidance in Appendix S and Chapter 11 of NUREG/CR-6850, it was generally assumed that Control Room panel fires would not propagate to adjacent cabinets.

ii. For the Control Room abandonment scenario, fire propagation was considered to conservatively fail all cabling and circuitry within the Control Room.

b) The MCB panels have closed outer walls and are not open to the room. The back panels also have closed outer walls and are not open to the room. The back panels are separated from the MCB panels by an air gap of at least 3 ft. Thus, the MCB and back panels are separated from each other by double walls and an air gap.

c) As noted in the assumption, the calculation of the Control Room abandonment frequency assumes that half of the Control Room panel fires will be single cable bundle fires and the other half will be multiple cable bundle fires. The calculation of the Control Room abandonment frequency combines the probability of a large Control Room fire with the probability the fire brigade will be unable to suppress the fire before Control Room abandonment is necessary.

Multiple cable bundle fires have a higher heat release rate from the incipient phases through the entire duration of the fire than single bundle fires. It is highly implausible for a fire to start in multiple cable bundles (the frequency would be equivalent to the ignition frequency squared); rather, it will first start as a single cable bundle fire with the potential to grow to involve multiple cable bundles. Also, since the Control Room is continuously manned, the rapid response to the fire will suppress most fires during the initial, single cable bundle stage and the fire will not become a multiple cable bundle fire. Therefore, it is

Attachment to 2CAN121302 Page 14 of 16 overly conservative to assume that all of the fires are multiple cable bundle fires throughout the entire duration of the fire. On the other hand, it may be non-conservative to assume that all of the fires are single bundle fires throughout the duration of the fire. Therefore, the assumption that half of the fires are multiple cable bundle from time zero, until the fire is suppressed, with the other half single cable bundle fires is considered an appropriate assumption to provide a more realistic, yet conservative result.

As noted in item a) above, the Control Room abandonment scenario conservatively fails all cabling and circuitry within the control room. It is only in the calculation of the abandonment frequency that the cable bundle assumption is applied.

Additional Information/Changes The following additional change associated with the original ANO-2 NFPA-805 LAR (Reference 1) is included in this 90-day RAI response letter. Entergy requests this change be considered in conjunction with the NRCs review of the RAI responses.

Further evaluation has concluded that the partial fire suppression system in the ANO-2 Containment Building is not required in support of NFPA 805 transition. On July 9, 2013, CALC-ANOC-FP-09-00004, Rev. 1, was issued which removed the Existing Engineering Equivalency Evaluation (EEEE) credit for the partial suppression system in the ANO-2 Containment Building.

Therefore, this letter identifies that the NRC need not consider reference this partial suppression system in Table 4-3 and Attachment C of the original LAR (Reference 1). The specific items are excerpted from the Reference 1 LAR and provided below for NRC reference.

Attachment to 2CAN121302 Page 15 of 16 The following additional change associated with the original ANO-2 NFPA-805 LAR (Reference 1) is included in this 90-day RAI (Reference 2) response letter.

Further evaluation has concluded that the partial fire suppression system in the ANO-2 Containment Building is not required in support of NFPA 805 transition. On July 9, 2013, CALC-ANOC-FP-09-00004, Rev. 1, was issued which removed Existing Engineering Equivalency Evaluation (EEEE) credit for the partial suppression system in the ANO-2 Containment Building. Therefore, reference to the partial suppression system in Table 4-3 and Attachment C of the original LAR (Reference 1) for Fire Zones 2032-K and 2033-K is being deleted. The specific items are excerpted from the Reference 1 LAR and provided below for NRC reference.

Table 4-3, Page 78 of Enclosure 1 from original LAR:

NN Unit 2 Containment Building Partial Suppression and 2032-K Containment Building South Side 4.2.4.2 N/RE E, R, D N/A Detection Partial Suppression and 2033-K Containment Building North Side 4.2.4.2 N/RE E, R, D N/A Detection Attachment C, Page C-187 from the original LAR:

Required Fire Protection Systems and Features Required?

Installed Separation LA EEEE Risk DID Fire Zone Fire Zone ID SUP DET SUP DET SUP DET SUP DET SUP DET SUP DET 2032-K Containment Building, South Side P P No No No No YesNo Yes No Yes No Yes 2033-K Containment Building, North Side P P No No No No YesNo Yes No Yes No Yes

Attachment to 2CAN121302 Page 16 of 16 Summary This letter provides the requested 90-day responses to NRC RAIs (Reference 2) associated with the ANO-2 NFPA-805 LAR dated December 17, 2012 (Reference 1), minus one 90-day Fire Modeling RAI and four 90-day PRA RAI responses previously included in Entergy letter dated November 7, 2013 (Reference 3). In addition, Entergy requests the changes associated with Table 4-3 and Attachment C of the original LAR (Reference 1) illustrated above be considered in conjunction with the NRCs review of the RAI responses.

REFERENCES

1. Entergy letter dated December 17, 2012, License Amendment Request to Adopt NFPA-805 Performance-Based Standard for Fire Protection for Light Water Reactor Electric Generating Plants (2001 Edition) (2CAN121202) (ML12353A041)

2. NRC letter dated September 11, 2013, Arkansas Nuclear One, Unit 2 - Request for Additional Information Regarding Adoption of National Fire Protection Association Standard NFPA-805 (TAC No. MF0404) (2CNA091301) (ML13235A005)

3. Entergy letter dated November 7, 2013, Response to Request for Additional Information -

Adoption of National Fire Protection Association Standard NFPA-805 (2CAN111301)

(ML13312A877)