ML062350598

Issuance of License Amendment 268 License Amendment Request for a One-Time Extension of the Containment Spray System, Allowable Outage Time (AOT)

ML062350598
Person / Time
Site:	Arkansas Nuclear
Issue date:	09/28/2006
From:	Holland D NRC/NRR/ADRO/DORL/LPLIV
To:	Forbes J Entergy Operations
Holland D, NRR/DORL/LP4, 415-1436
References
TAC MC8541
Download: ML062350598 (21)

Text

September 28, 2006 Mr. Jeffrey S. Forbes Site Vice President Arkansas Nuclear One Entergy Operations, Inc.

1448 S. R. 333 Russellville, AR 72801

SUBJECT:

ARKANSAS NUCLEAR ONE, UNIT NO. 2 (ANO-2)- ISSUANCE OF AMENDMENT RE: LICENSE AMENDMENT REQUEST FOR A ONE-TIME EXTENSION OF THE CONTAINMENT SPRAY SYSTEM (CSS) ALLOWABLE OUTAGE TIME (AOT) (TAC NO. MC8541)

Dear Mr. Forbes:

The Commission has issued the enclosed Amendment No. 268 to Facility Operating License No. NPF-6 for ANO-2. The amendment consists of changes to the Technical Specifications (TSs) in response to your application dated September 19, 2005, as supplemented by letters dated February 28, May 31, and September 26, 2006.

The amendment revises TS 3.6.2.1, Containment Spray System. Specifically, the proposed changes revise the AOT for TS 3.6.2.1 from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days during fuel cycles 19 and 20.

Per the license amendment request, the AOT extension may only be invoked twice (i.e., once for each train or twice for one train).

The requested changes are sought to provide needed flexibility in the performance of selected corrective and preventative maintenance activities during power operations. Currently, the licensees maintenance activities on CSS components are performed during the refueling outages; taking several days of around the clock effort.

A copy of our related Safety Evaluation is also enclosed. The Notice of Issuance will be included in the Commission's next biweekly Federal Register notice.

Sincerely,

/RA/

Drew G. Holland, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-368

Enclosures:

1. Amendment No. 268 to NPF-6

2. Safety Evaluation cc w/encls: See next page

September 28, 2006 Mr. Jeffrey S. Forbes Site Vice President Arkansas Nuclear One Entergy Operations, Inc.

1448 S. R. 333 Russellville, AR 72801

SUBJECT:

ARKANSAS NUCLEAR ONE, UNIT NO. 2 (ANO-2)- ISSUANCE OF AMENDMENT RE: LICENSE AMENDMENT REQUEST FOR A ONE-TIME EXTENSION OF THE CONTAINMENT SPRAY SYSTEM (CSS) ALLOWABLE OUTAGE TIME (AOT) (TAC NO. MC8541)

Dear Mr. Forbes:

The Commission has issued the enclosed Amendment No. 268 to Facility Operating License No. NPF-6 for ANO-2. The amendment consists of changes to the Technical Specifications (TSs) in response to your application dated September 19, 2005, as supplemented by letters dated February 28, May 31, and September 26, 2006.

The amendment revises TS 3.6.2.1, Containment Spray System. Specifically, the proposed changes revise the AOT for TS 3.6.2.1 from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days during fuel cycles 19 and 20.

Per the license amendment request, the AOT extension may only be invoked twice (i.e., once for each train or twice for one train).

The requested changes are sought to provide needed flexibility in the performance of selected corrective and preventative maintenance activities during power operations. Currently, the licensees maintenance activities on CSS components are performed during the refueling outages; taking several days of around the clock effort.

A copy of our related Safety Evaluation is also enclosed. The Notice of Issuance will be included in the Commission's next biweekly Federal Register notice.

Sincerely,

/RA/

Drew G. Holland, Project Manager Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation Docket No. 50-368

Enclosures:

1. Amendment No. 268 to NPF-6

2. Safety Evaluation cc w/encls: See next page DISTRIBUTION PUBLIC LPLIV R/F RidsNrrDorlLpl4 RidsNrrPMDHolland GHill RidsNrrLALFeizollahi RidsNrrDirsItsb RidsAcrsAcnwMailCenter RidsOgcRp RidsNrrDorlDpr DHarrison, DRA RidsRgn4MailCenter (DGraves) FForsaty, DSS RidsNrrDssSpwb Package: ML062580080 TSs: ML062720175 Accession No.: ML062350598 NRR-058 OFFICE NRR/LPL4/PM NRR/LPL4/LA NRR/SPWB/SC OGC NRR/LPL4/BC NAME DHolland:sp LFeizollahi JNakoski TCampbell DTerao DATE 9/27/06 9/27/06 8/29/06 9/27/06 9/28/06 OFFICIAL RECORD COPY

ENTERGY OPERATIONS, INC.

DOCKET NO. 50-368 ARKANSAS NUCLEAR ONE, UNIT NO. 2 AMENDMENT TO RENEWED FACILITY OPERATING LICENSE Amendment No. 268 Renewed License No. NPF-6

1. The Nuclear Regulatory Commission (the Commission) has found that:

A. The application for amendment by Entergy Operations, Inc. (the licensee), dated September 19, 2005, as supplemented by letters dated February 28, May 31, and September 26, 2006, complies with the standards and requirements of the Atomic Energy Act of 1954, as amended (the Act), and the Commission's rules and regulations set forth in 10 CFR Chapter I; B. The facility will operate in conformity with the application, the provisions of the Act, and the rules and regulations of the Commission; C. There is reasonable assurance (i) that the activities authorized by this amendment can be conducted without endangering the health and safety of the public, and (ii) that such activities will be conducted in compliance with the Commission's regulations; D. The issuance of this license amendment will not be inimical to the common defense and security or to the health and safety of the public; and E. The issuance of this amendment is in accordance with 10 CFR Part 51 of the Commission's regulations and all applicable requirements have been satisfied.

2. Accordingly, the license is amended by changes to the Technical Specifications as indicated in the attachment to this license amendment, and paragraph 2.C.(2) of Renewed Facility Operating License No. NPF-6.

3. The license amendment is effective as of its date of issuance and shall be implemented within 60 days from the date of issuance.

FOR THE NUCLEAR REGULATORY COMMISSION

/RA/

David Terao, Chief Plant Licensing Branch IV Division of Operating Reactor Licensing Office of Nuclear Reactor Regulation

Attachment:

Changes to the Facility Operating License and Technical Specifications Date of Issuance: September 28, 2006

ATTACHMENT TO LICENSE AMENDMENT NO. 268 RENEWED FACILITY OPERATING LICENSE NO. NPF-6 DOCKET NO. 50-368 Replace page 3 of the Renewed Facility Operating License No. NFP-6 with the attached revised page 3.

Remove Insert 3 3 Replace the following page of the Appendix A Technical Specifications with the attached revised page. The revised page is identified by an amendment number and contains marginal lines indicating the areas of change.

Remove Insert 3/4 6-10 3/4 6-10

SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATED TO AMENDMENT NO. 268 TO RENEWED FACILITY OPERATING LICENSE NO. NPF-6 ENTERGY OPERATIONS, INC.

ARKANSAS NUCLEAR ONE, UNIT NO. 2 DOCKET NO. 50-368

1.0 INTRODUCTION

By application dated September 19, 2005 (Agencywide Documents Access and Management System (ADAMS) Accession No. ML052760276), as supplemented by letters dated February 28 (ADAMS Accession No. ML060740624), May 31 (ADAMS Accession No. ML061590309), and September 26, 2006 (ADAMS Accession No. and ML062700604, respectively), Entergy Operations, Inc. (the licensee), requested changes to the Technical Specifications (TSs) for Arkansas Nuclear One, Unit No. 2 (ANO-2). The supplements dated February 28, May 31, and September 26, 2006, provided additional information that clarified the application, did not expand the scope of the application as originally noticed, and did not change the staff's original proposed no significant hazards consideration determination as published in the Federal Register on January 3, 2006 (71 FR 148).

The proposed changes would revise TS 3.6.2.1, Containment Spray System. Specifically, the proposed changes would revise the allowable outage time (AOT) for TS 3.6.2.1 from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days during fuel cycles 19 and 20. Per the license amendment request, the AOT extension may only be invoked twice (i.e., once for each train or twice for one train).

The requested changes are sought to provide needed flexibility in the performance of selected corrective and preventative maintenance activities during power operation. Currently, the licensees maintenance activities on containment spray system (CSS) components are performed during refueling outages. These activities take several days of around the clock effort. The licensee specifically stated that the requested changes would allow:

• An increased flexibility in the scheduling and performance of maintenance activities.

• A reduction in the number of individual entries into limiting conditions for operation action statements by providing sufficient time to perform related maintenance tasks within a single entry.

• Better control of resource allocation. During outage maintenance windows, plant personnel and resources are spread across a large number and wide variety of maintenance tasks. Allowing on-line maintenance gives the plant the flexibility to focus dedicated resources on the CSS maintenance.

• Improved availability of CSS components important to safety during shutdown modes.

2.0 REGULATORY EVALUATION

The CCS post-accident containment heat removal and radioactive iodine removal capabilities.

2.1 Description of System/Component and Current Requirements The CSS is designed to spray borated water into the containment building in the event of a loss-of-coolant accident (LOCA) or a main steam line break (MSLB). This action of the CSS suppresses any increase in containment temperature and pressure due to a LOCA or less severe high energy line break. The system spray absorbs post-accident radioactive iodine from the containment atmosphere following an accident.

2.2 Applicable Regulations General Design Criterion (GDC) 38, "Containment heat removal," Title 10 of the Code of Federal Regulations (10 CFR), provides the general design requirements for the CSS. The specific requirements for the CSS are contained in NUREG-0308, "Safety Evaluation Report

[SER] Related to Operation of Arkansas Nuclear One, Unit 2 Arkansas Power and Light Company."

2.3 Applicable Regulatory Criteria/Guidelines The regulatory guidelines on which the staff based its acceptance are:

• Regulatory Guide (RG) 1.174, "An Approach for Using Probabilistic Risk Assessment in Risk-Informed Decisions on Plant-Specific Changes to the Licensing Basis," describes a risk-informed approach, acceptable to the Nuclear Regulatory Commission (NRC), for assessing the nature and impact of proposed licensing-basis changes by considering engineering issues and applying risk insights. This RG also provides risk acceptance guidelines for evaluating the results of such evaluations.

• RG 1.177, "An Approach for Plant-Specific, Risk-Informed Decisionmaking: Technical Specifications," describes an acceptable risk-informed approach specifically for assessing proposed TS changes in AOTs. This RG also provides risk acceptance guidelines for evaluating the results of such evaluations.

One acceptable approach for making risk-informed decisions about proposed TS changes, including both permanent and temporary changes, is to show that the proposed changes meet the five key principles stated in RG 1.174, Section 2, and RG 1.177, Section B:

1. The proposed changes meet the current regulations unless they are explicitly related to a requested exemption or rule change.

2. The proposed changes are consistent with the defense-in-depth philosophy.

3. The proposed changes maintain sufficient safety margins.

4. When the proposed changes result in an increase in core-damage frequency or risk, the increase should be small and consistent with the intent of the Commissions Safety Goal Policy Statement.

5. The impact of the proposed changes should be monitored using performance measurement strategies.

For permanent TS changes, RG 1.174 and RG 1.177 provide numerical risk acceptance guidelines that are helpful in determining whether or not the fourth key principle has been satisfied. These guidelines are not to be applied in an overly prescriptive manner; rather, they provide an indication, in numerical terms, of what is considered acceptable. The intent in comparing risk results with the risk acceptance guidelines is to demonstrate, with reasonable assurance, that the fourth key principle has been satisfied.

For temporary TS changes, examination of the risk metrics identified in RG 1.174 and RG 1.177 provides insight into the potential risk impacts, even though neither of these RGs provide numerical risk acceptance guidelines for evaluating temporary TS changes against the fourth key principle. It can be demonstrated, with reasonable assurance, that a temporary TS change meets the fourth key principle if its associated risk metrics:

• Satisfy the risk acceptance guidelines in RG 1.174 and RG 1.177, or

• Are not substantially above the risk acceptance guidelines in RG 1.174 and RG 1.177 and effective, but unquantified, compensatory measures to lower risk are implemented while the temporary TS change is in effect.

3.0 TECHNICAL EVALUATION

The staff has reviewed the licensees regulatory and technical analyses in support of its proposed license amendment. The following sections provide a detailed description of the proposed changes, describe the staffs review methodology, identify the key information reviewed by the staff, compare the proposed changes to applicable regulatory guidelines, and present the staffs findings.

3.1 Detailed Description of the Proposed Change Currently, the TS Action statement for ANO-2 TS 3.6.2.1 requires restoration of an inoperable CSS to an operable status within 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br />. If restoration of the CSS cannot be accomplished in the allowable time, the unit shall be placed in HOT STANDBY within the next 6 hours6.944444e-5 days <br />0.00167 hours <br />9.920635e-6 weeks <br />2.283e-6 months <br /> and in COLD SHUTDOWN within the following 30 hours3.472222e-4 days <br />0.00833 hours <br />4.960317e-5 weeks <br />1.1415e-5 months <br />. The licensee proposes to modify the current Action with the following note:

Note 1: For fuel cycles 19 and 20, each train of the containment spray system may be removed from service for up to 7 days or one train may be removed from service two times. The 7-day allowance may be applied only twice.

3.2 Staff Review Methodology Per Standard Review Plan (SRP), Chapter 16.1, Risk-Informed Decisionmaking: Technical Specifications, the staff reviewed the submittal against the five key principles of the staffs standards for risk-informed decisionmaking, listed in RG 1.177, Section B.

3.3 Key Information Used in Staff Review The key information used in the NRC staff's review of the risk evaluation is contained in Sections 4.2 and 4.3 of Attachment 1 of the licensees original submittal (Reference 1), as supplemented by the licensee in response to the staffs request for additional information (RAI)

(Reference 2).

The licensee also stated in its original submittal that Combustion Engineering Owners Group (CEOG) Joint Application Report (JAR) CE-NPSD-1045-A, Joint Applications Report for Modifications to the Containment Spray System Technical Specifications, was also applicable to this license amendment. The JAR, which contains plant-specific risk results and insights for almost every Combustion Engineering plant, including ANO-2, was submitted in April of 1998 to allow an extension of the AOT to 7 days for one CSS train and approved by the staff in December 1999, with a number of conditions and exceptions that need to be addressed in plant-specific license applications. The approved JAR was issued in March 2000. Although the underlying methodology is appropriate for this license amendment request, the licensees plant-specific models and analyses have changed since the JAR was approved. Therefore, the staff has relied upon the information provided in the original submittal, as supplemented by the licensees responses to the staffs RAIs.

3.4 Comparison Against Regulatory Criteria/Guidelines The staffs comparison of the licensees proposed license amendment for a temporary extension of the CSS AOT to the five key principles is presented in the following sections.

3.4.1 Traditional Engineering Evaluation The traditional engineering evaluation presented below addresses the first three key principles of the staffs standards for risk-informed decisionmaking, which concern compliance with current regulations, evaluation of defense-in-depth, and evaluation of safety margins.

3.4.1.1 Compliance with Current Regulations The licensee has maintained operability of the CSS in accordance with the license, the TSs, the SAR, and the SER, as amended. The CSS conforms to the applicable sections of Title 10 of the Code of Federal Regulations.

3.4.1.2 Evaluation of Defense-in-Depth The Containment Heat Removal System (CHRS) consists of the CSS and the Containment Cooling System (CCS). The CHRS functions to rapidly reduce the containment pressure and temperature after a postulated loss of coolant accident (LOCA) or MSLB accident by removing thermal energy from the containment atmosphere. The CHRS also assists in limiting off-site radiation levels by reducing the pressure differential between the containment atmosphere and the outside atmosphere, thereby reducing the driving force for leakage of fission products from the containment.

The CHRS is designed so that the operation of either both trains of the CSS, or a combination of one train of CSS and one train of CCS, will provide adequate heat removal from the containment to attenuate the post-accident pressure and temperature conditions imposed upon the containment following a LOCA or MSLB.

The CSS also provides for iodine removal from the containment atmosphere by a combination of boric acid spray and a buffered pH solution. Therefore, at least one CSS must be in operation following a LOCA.

The changes proposed by the licensee for this amendment do not change the CSS design or its operability. The changes proposed do not change any aspect of the CSS design and licensing basis other than minor changes in accident risk. Accident risk impacts are discussed, in depth, further on in this safety evaluation.

3.4.1.3 Evaluation of Safety Margins CSS design safety margins, except for risk, are unaffected by these changes. Allowed outage time extensions will elevate risk slightly and correspondingly reduce system reliability slightly.

The Risk Evaluation will discuss the affect of extended allowed outage times on safety margins.

3.4.2 Risk Evaluation The risk evaluation presented below addresses the last two key principles of the staffs standards for risk-informed decisionmaking, which concern changes in risk and performance monitoring strategies. These key principles were evaluated using the three-tiered approach described in Chapter 16.1 of the SRP and RG 1.177:

• Tier 1 - The first tier evaluates the licensee's probabilistic risk/safety assessment (PRA/PSA) and the impact of the change on plant operational risk, as expressed by the change in core damage frequency (CDF) and change in large early release frequency (LERF). The change in risk is compared to the acceptance guidelines presented in RG 1.174. The first tier also aims to ensure that plant risk does not increase unacceptably during the period when equipment is taken out of service per the license amendment, as expressed by the incremental conditional core damage probability (ICCDP) and incremental conditional large early release probability (ICLERP). The incremental risk is also compared to the acceptance guidelines presented in RG 1.177.

• Tier 2 - The second tier addresses the need to preclude potentially high-risk plant configurations that could result if equipment, in addition to that associated with the proposed license amendment, are taken out of service simultaneously, or if other risk-significant operational factors, such as concurrent system or equipment testing, are also involved. The objective of this part of the review is to ensure that appropriate restrictions on dominant risk-significant plant configurations associated with the AOT extension are in place.

• Tier 3 - The third tier addresses the licensee's overall configuration risk management program (CRMP). The purpose of the CRMP is to ensure that equipment removed from service prior to or during the proposed extended AOT period will be appropriately assessed from a risk perspective.

This program ensures that adequate programs and procedures are in place to identify risk-significant plant configurations resulting from maintenance or other operational activities and to take appropriate compensatory measures to avoid such configurations.

3.4.2.1 Tier 1: PSA Capability and Insights The Tier 1 staff review evaluates two aspects of the AOT in the license amendment request:

(1) technical adequacy of the licensees PSA and its application to the proposed AOT extension, and (2) PSA results and insights stemming from its application.

3.4.2.1.1 Evaluation of PSA Technical Adequacy In order to determine whether the PSA used in support of the proposed AOT extension is of sufficient quality, scope, and level of detail, the staff evaluated the relevant information provided by the licensee in its submittal, as supplemented, and considered the findings of recent PSA reviews. The staff's review of the licensee's submittal focused on the ability of the licensee's PSA model to analyze the risks stemming from the proposed AOT extension and did not involve an in-depth review of the licensee's PSA.

The licensees assessment of the risk impact of extending the current CSS AOT from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days includes a quantitative assessment based on the ANO-2 PSA model, a qualitative assessment of other Level I risk contributors (e.g., from external events), and a qualitative assessment of the Level II risk impact.

The ANO-2 PSA model has been updated several times since the Individual Plant Examination to keep it consistent with the as-built/as-operated plant, to incorporate new and revised plant-specific thermal hydraulic results, and to incorporate new and revised PSA methodologies. The PSA model and results are maintained as controlled documents; for this evaluation, the licensee used the ANO-2 PSA model 4p00. This model is an at-power Level I internal events risk model which explicitly includes anticipated transients without scram and interfacing system loss-of-coolant accident (ISLOCA) scenarios. In February 2002, a CEOG PSA peer review was conducted on the ANO-2 PSA. The peer review report identified a number of A level and B level facts and observations (F&Os). Many of the F&Os have been resolved and the model updated, as appropriate. The licensee, in Attachment 4 of its original submittal, described the impact of each of the remaining A and B level F&Os and concluded that none of the remaining F&Os would have an impact on the conclusions of the risk

assessment. The staff notes that a number of the F&Os are related to PSA Level II analyses and one F&O is directly related to CSS operations (SY-07). The licensee performed a sensitivity calculation addressing the SY-07 F&O concern to show that the SY-07 F&O has no more than a small impact (about a 1 percent increase) on the results.

In addition, the staff has previously reviewed the technical adequacy of the ANO-2 PSA in support of a risk-informed emergency diesel generator TS AOT extension and in support of an extended power uprate. The staff also reviewed the results of the current ANO-2 PSA model as part of its benchmarking of the ANO-2 Significance Determination Process notebook in November 2001. None of these staff reviews have identified any issues that would directly impact the licensees CSS AOT extension submittal.

The ANO-2 PSA model does not address high and medium energy line breaks (high-energy line breaks and moderate-energy line breaks), PSA Level II aspects (e.g., release categories, and thus, LERF or ICLERP), the risk impact from external events, such as seismic events and internal fires, or the risk impact from low power/shutdown operations. The licensee performed a qualitative analysis to assess the risk impact of the CSS extended AOT for the line breaks and external events, which is included in the licensees original submittal. The licensee also included a commitment in its supplemental response to not commence maintenance activities on the CSS for an extended AOT if conditions exist or are expected that could exacerbate plant risks due to external events (see Section 4.0 of this safety evaluation for the licensees regulatory commitments).

The licensee explicitly excluded internal fires from its qualitative analyses. RG 1.177, Section 2.3.2, states that the scope of the risk evaluations made to assess changes to TS requirements should include internal fires. Ideally, quantitative evaluations should be made; however, qualitative arguments, bounding analyses, and compensatory measures may also be used. The licensee stated in its original submittal that the ANO-2 fire risk analysis is an update of the ANO-2 Individual Plant Examination of External Events (IPEEE), which used the NRC-approved Fire Induced Vulnerability Evaluation methodology. Since the purpose of this analysis approach was to identify plant-specific vulnerabilities, the licensee stated that it does not provide a realistic estimate of the fire CDF. Instead of evaluating the fire risk, the licensee relied upon its current procedures and training programs to provide assurance that transient combustibles and hot-work are controlled in such a manner that fire events will be minimized.

In response to a staff RAI regarding the lack of a fire analysis or specific compensatory actions to address fires, the licensee provided a qualitative discussion of the potential impacts from fires during the proposed CSS extended AOT. Specifically, the licensee stated that there were two ways in which the removal of a train of CSS from service could increase fire risk:

1. the maintenance could elevate the probability of a fire in the areas affected by the subject train of CSS maintenance, or

2. the maintenance could elevate the risk importance of equipment on the opposite emergency safeguards features train.

The licensee stated that it expects the risk of fires to be similar to the nominal plant conditions, given the small increase in the internal events analyses. The licensee also used the insights provided in its IPEEE to further reduce the fire-related risks and identified a new commitment.

This commitment, which is stated in Section 4.0 of this safety evaluation, is to ensure the ignition source probability is as low as possible in the turbine building to maintain the availability of off-site power. This commitment will be met by posting an hourly roving fire watch in that area. A roving fire watch will also be posted in other risk-significant areas, which include: the operable train of CSS, the containment cooling system (CCS), the high-pressure safety injection (HPSI) system, both emergency feedwater (EFW) trains, and the auxiliary feedwater (AFW) system. Through these measures, the risk impacts associated with fires during the CSS extended AOT will be minimized. The staff concludes that the licensees qualitative argument for the consideration of fire impacts, including the use of associated compensatory measures, is adequate only as a one-time application for the CSS extended AOT. The staffs conclusion is primarily based, for this one-time application, on the use of the fire-related compensatory measures. However, the staff emphasizes that a more comprehensive fire assessment would be necessary for any future risk-informed permanent changes.

The licensee also indicated that the current ANO-2 PSA model does not address the impact on the large early release metrics (i.e., Level II PSA aspects of LERF and ICLERP). Since CSS is relied upon for containment heat removal (a Level II PSA aspect not addressed by the ANO-2 PSA), as well as supporting emergency core cooling recirculation operations (the Level I PSA aspect addressed) and noting that there are a number of unresolved F&Os from the industry peer review of the ANO-2 PSA related to LERF modeling, the staff requested additional information regarding the acceptability of the application without explicitly addressing and quantifying the large early release impacts. In response to the staff RAI, the licensee stated that managing the core damage metrics within the guidance limits of RG 1.174 and RG 1.177 would also result in managing the large early release metrics within the guidance limits. The basis for this statement is that the LERF is less than 10 percent of the ANO-2 CDF for all accidents, except for steam generator tube rupture (SGTR) and ISLOCA. These two accident initiators bypass containment, and thus, the licensee concluded that the contribution of the CSS in risk calculations for these scenarios is negligible. Further, the licensee stated that SGTR and ISLOCA are small contributors to the overall internal events CDF (about 0.7 percent and 0.001 percent, respectively).

The staff recognizes that the type of containment at ANO-2 (large, dry containment) typically has a small conditional probability of early structural failure (less than 10 percent) and that the LERF is typically dominated by events that result in a release that bypasses the containment, such as SGTRs and ISLOCAs. However, the unavailability of a train of CSS can impact the probability of early containment failure since it supports the containment heat removal function, along with the CCS (fan coolers). The staff also considered the discussions on large early releases provided in the staff-approved CEOG JAR CE-NPSD-1045-A, (specifically Section 6.3.5 and responses to Questions 1 and 2 in Attachment B to the CEOG JAR), the licensees RAI responses related to the results cited in the JAR, and considered information from NUREG/CR-6595, Revision 1, An Approach for Estimating the Frequencies of Various Containment Failure Modes and Bypass Events, and NUREG-1560, Individual Plant Examination Program: Perspectives on Reactor Safety and Plant Performance. Based on these considerations, the staff concluded that it is not necessary for the licensee to explicitly address the large release metrics in this application. The staff notes that the application, as submitted, would not be acceptable as a permanent change and the licensee would need to explicitly and quantitatively address the large early release metrics for any future permanent

risk-informed license amendment request. The specific considerations of the staff regarding the large early release metrics are provided in Section 3.4.2.1.2 of this safety evaluation.

Based on the staff review of the above information, the staff finds that the scope of the ANO-2 PSA is deficient in a number of areas, and is particularly deficient in addressing and quantifying risk impacts associated with fires and in analyzing large early releases. However, based on the licensees actions stated as commitments and presented in Section 4.0 of this safety evaluation, the qualitative arguments supporting a minimal impact of this application on LER frequency, and the CSS AOT extension only being granted for limited application (i.e., once for each train or twice for one train over the next two cycles), the staff finds the licensee's submittal as satisfying the intent of RG 1.177 (Sections 2.3.1, 2.3.2, and 2.3.3), RG 1.174 (Sections 2.2.3 and 2.5), and SRP Chapter 19.1 for this limited application. For those aspects of the evaluation in which the licensee has used the ANO-2 PSA, the staff finds the PSA to be of sufficient quality.

3.4.2.1.2 Evaluation of PSA Results and Insights As previously discussed, satisfaction of the fourth key principle of risk-informed decisionmaking may be demonstrated with reasonable assurance by comparing risk metrics that reflect the proposed TS changes to the numerical risk acceptance guidelines in RG 1.174 and RG 1.177.

For the preventive maintenance case, because such maintenance is planned to minimize plant risk consistent with the maintenance rule, 10 CFR 50.65(a)(4), the licensee used the ANO-2 PSA model with the CSS common cause failure (CCF) basic events set to zero and with essentially no other systems in testing and maintenance (T&M). This is a zero maintenance PSA model, with no potential for CSS CCFs. The staff observes that, ideally, all risk metrics used in risk-informed license applications should be determined by adjusting an average maintenance PSA model (i.e., a PSA model that includes contributions from equipment maintenance unavailability). The use of a zero maintenance PSA model, which omits system maintenance unavailability contributions, in determining the RG 1.174 and RG 1.177 risk metrics introduces additional uncertainty into the analysis. However, the contribution from equipment maintenance unavailability to changes in risk depends on the likelihood of performing maintenance on other plant equipment in parallel with maintenance on the equipment whose AOT is being extended. The likelihood of simultaneous maintenance actions is judged to be small and will be controlled by the licensee by its risk-informed CRMP, which is discussed further in Section 3.4.2.3 below. Therefore, the magnitude of the additional uncertainty resulting from use of a zero maintenance PSA model is small. The staff concludes that the licensees use of a zero maintenance PSA model for the preventive maintenance case is acceptable.

For the corrective maintenance case, the licensee used the ANO-2 PSA model with elevated CSS CCF values and nominal values for T&M activities. This is an average maintenance PSA model, with an elevated potential for CSS CCFs. Since the corrective maintenance case is the more limiting condition (and only slightly worse than the zero maintenance PSA model results), the staff has relied upon the results for this configuration, as provided in the summary table below.

Corrective Maintenance Baseline Train A Train B Total CDF 6.4 x 10-6/reactor-year 6.6 x 10-6/reactor-year 9.0 x 10-6/reactor-year Total ICCDP 3.1 x 10-9 4.8 x 10-8 The above results include the impacts from internal events, internal floods, seismic and other external events, and high and medium energy line breaks. The results do not include impacts due to fires, which as stated previously are addressed by compensatory measures and identified as regulatory commitments in Section 4.0 of this safety evaluation.

Section 2.4 of RG 1.177 states that a permanent TS AOT change has only a small quantitative impact on plant risk if the ICCDP is less than 5 x 10-7 and the ICLERP is less than 5 x 10-8. The ICCDPs for Train A and B corrective maintenance meet the acceptance guidelines for ICCDP and ICLERP. Section 2.4 of RG 1.177 also requires the comparison of risk metrics to the risk acceptance guidelines contained in Section 2.2.4 (CDF [differential core damage frequency]

versus baseline CDF) and Section 2.2.5 (LERF [differential large early release frequency]

versus baseline LERF) of RG 1.174. The increase related to CSS Train A being out of service for corrective maintenance is representative of a very small increase (CDF of 2.0 x 10- 7/reactor-year), while the increase related to CSS Train B being out of service for corrective maintenance is representative of a small increase (CDF of 2.6 x 10-6/ reactor-year). The CDF results are acceptable for both trains. The CSS Train A increase in CDF would also be acceptable as a small increase when compared to the LERF acceptance guidelines of RG 1.174, but the CSS Train B increase in CDF would not be acceptable when compared directly against the LERF acceptance guidelines of RG 1.174.

As stated previously, the licensee did not calculate large early release metrics (i.e., LERF and ICLERP). The staff recognizes that the type of containment at ANO-2 (large, dry containment) typically has a small conditional probability of early structural failure (typically less than 10 percent) and that the LERF is typically dominated by events that result in a release that bypasses the containment, such as SGTRs and ISLOCAs. However, the unavailability of a train of CSS can increase the probability of early containment failure since it supports the containment heat removal function, along with the CCS (fan coolers). Therefore, the staff considered the discussions on large early releases provided in the staff-approved CEOG JAR CE-NPSD-1045-A (specifically Section 6.3.5 and Responses to Questions 1 and 2 in Attachment B to the CEOG JAR), the licensees RAI responses related to the results cited in the JAR, and information contained in NUREG/CR-6595, Revision 1, and NUREG-1560. All of these reports consider the same basic categories for causes of large early releases:

containment bypass events (e.g., SGTRs and ISLOCAs), containment isolation failures, and early containment failure. Each of these large early release categories are discussed below.

In relying on the core damage metrics to manage the large early release metrics, the licensees rationale is that the LERF is less than 10 percent of the ANO-2 CDF for all accidents, except for SGTR and ISLOCA. These two accident initiators bypass containment, and thus, the licensee concludes that the contribution of the CSS for these non-bypass scenarios is negligible.

Further, the licensee states that SGTR and ISLOCA are small contributors to the overall internal

events CDF (about 0.7 percent and 0.001 percent, respectively). To verify that the CSS has no impact on the risk contribution from bypass events, the staff reviewed the ANO-2 Standardized Plant Analysis Risk (SPAR) model (Revision 3, dated November 2000). In the ANO-2 SPAR model, the CSS is only addressed for SGTR sequences that also involve the failure of emergency and main feedwater and either the failure to successfully throttle high pressure injection to slowly depressurize the reactor coolant system, or the failure to achieve shutdown cooling. The SGTR contribution to total CDF in the SPAR model is approximately 16 percent; however, the SGTR sequences that involve the CSS are only about 0.002 percent of the total CDF from internal events. In addition, the SPAR model does not identify the CSS as an ISLOCA path and the identified ISLOCA contribution to total CDF from internal events is less than 1 percent. Therefore, the staff concludes that the CSS impact on bypass events is negligibly small and will meet the LERF acceptance guidelines.

For containment isolation failures, it is stated in CE-NPSD-1045-A that these types of events, in conjunction with a severe accident, typically represent a very small contribution (less than 1 percent) to the total containment failure probability. In CE-NPSD-1045-A it is estimated as being less than 1 x 10-9/year, which is considered negligibly small in comparison to the typical base LERF value of about 1 x 10-6/year. For the purposes of this application, the LERF and ICLERP could be estimated for containment isolation failure-related events by multiplying the CDF and ICCDP values by the probability of a loss of containment isolation, which typically has a value that is less than 1 x 10-2. The resulting LERF and ICLERP estimates, based on CSS Train B being in corrective maintenance, are 2.6 x 10-8/reactor-year and 4.8 x 10-10, respectively. Both of these estimates are considered acceptable as having a very small risk impact per the acceptance guidelines of RG 1.174 and RG 1.177.

Early containment failures were also addressed in CE-NPSD-1045-A and determined to be negligibly impacted by the proposed extension of the ANO-2 CSS TS. For large, dry containments, such as the ANO-2 containment, it is stated in NUREG-1560 that early containment failure is considered relatively unimportant for pressurized-water reactors (PWRs),

with an average conditional probability of failure of about 0.05, while bypass events are considered relatively important for most PWRs and isolation failures are considered relatively important for some PWRs. In Section 12.3.1.2 of NUREG-1560, ANO-2 is specifically identified as having an early containment failure probability of 0.1 and notes that this is primarily due to sequences in which core injection is successful in the injection mode, but fails in the recirculation mode and containment heat removal is not available. The loss of core injection in the recirculation mode due to a loss of containment heat removal is addressed in the ANO-2 PSA and addressed by the licensees evaluation of the core damage metrics. Using 0.1 as the early containment failure probability for these events would result in a LERF of about 2.6 x 10-7/reactor-year for CSS Train B in corrective maintenance, which would be considered an acceptably small increase in LERF. For the CSS extended AOT to have additional large early release impacts related to early containment failures (not already addressed by the licensees analyses), the analysis would require inclusion of scenarios that involve the independent failures of core injection in the recirculation mode and containment heat removal. These scenarios are considered to be considerably less likely than the previously described scenario and, thus, are expected to have a LERF value much less than 1 x 10-7/reactor year.

Therefore, the staff concludes, based on the staffs analyses above, that it is expected that the early containment failure related scenarios will also meet the LERF acceptance guidelines of RG 1.174.

Based upon the information provided by the licensee, considering the compensatory actions to minimize the fire risk impact, the above staff discussion regarding large early release expected impacts, and the fact that this is only a one-time application for extending the CSS AOT, the staff concludes that the proposed temporary change is acceptable and expected to result in no more than a small increase in risk that is consistent with the NRCs Safety Goal Policy Statement. Therefore, the staff finds that the licensees first tier risk evaluation, as described in Chapter 16.1 of the SRP and RG 1.177, is acceptable only as a one-time extension. The staff notes that the application, as submitted, would not be acceptable as a permanent change and the licensee would need to explicitly and quantitatively address the large early release metrics and fire-related risks for any future permanent risk-informed license amendment request.

3.4.2.2 Tier 2: Avoidance of Risk-Significant Plant Configurations The second tier evaluates the capability of the licensee to recognize and avoid risk-significant plant configurations that could result if equipment, in addition to that associated with the proposed license amendment, is taken out of service simultaneously or if other risk-significant operational factors, such as concurrent system or equipment testing, are also involved.

In the original submittal, the licensee stated that it used the CRMP per its commitment to complying with 10 CFR 50.65 to address the Tier 2 considerations. In the staff RAIs, the staff noted that this reliance on the licensees CRMP is more appropriate for the Tier 3 evaluation, which ensures that adequate programs and procedures are in place for identifying risk-significant plant configuration and taking appropriate actions to avoid such configurations.

Whereas the Tier 3 evaluation ensures the CRMP is adequate when maintenance is about to commence, the Tier 2 evaluation is meant to be an early evaluation (at the time of the license submittal requesting the action) to identify and preclude potentially high-risk plant configurations. In response to this RAI, the licensee stated that no unique high-risk plant configurations are expected during the CSS extended AOT. However, since there is a slight increase in the importance of the containment cooling function, which is provided by the other CSS train and the CCS, and in the steam generator heat removal function, which is provided by the EFW and AFW systems, during the CSS train extended AOT, the licensee made a commitment to perform no preventive maintenance or testing that would render the operable CSS train, CCS, HPSI, either EFW train, or the AFW system inoperable (See Section 4.0, Regulatory Commitments).

Based on the licensees supplemental response to the staff RAIs, the licensee has demonstrated the ability to recognize and avoid risk-significant plant configurations. Therefore, the staff finds that the licensees Tier 2 evaluation, as described in Chapter 16.1 of the SRP and RG 1.177, is acceptable.

3.4.2.3 Tier 3: Risk-Informed Configuration Risk Management The third tier assesses the licensees program to ensure that the risk impact of out-of-service equipment is appropriately evaluated prior to performing any maintenance activity. The need for this third tier stems from the difficulty of identifying all possible risk-significant configurations under the second tier.

Consistent with 10 CFR 50.65(a)(4), the licensee has a CRMP, which is described at a high level in Section 4.2.3 of Attachment 1 of the original submittal. The CRMP is a proceduralized risk-informed assessment process intended to manage the risk associated with planned and unplanned plant maintenance activities. The licensee stated, in its original submittal, that the program ensures that the risk impact of out-of-service equipment is appropriately evaluated prior to performing a planned maintenance activity and soon after entering into an emergent maintenance condition.

Therefore, the staff finds that the licensees third tier risk evaluation, as described in Chapter 16.1 of the SRP and RG 1.177, is acceptable.

3.5 Staff Evaluation Findings In summary, the NRC staff finds that the licensee's proposed changes to revise, on a temporary basis, the AOT for TS 3.6.2.1 from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days are acceptable because the five key principles of risk-informed decisionmaking identified in RG 1.174 and RG 1.177 have been satisfied only as a one-time extension. The staff notes that the application, as submitted, would not be acceptable as a permanent change and the licensee would need to explicitly and quantitatively address the large early release metrics and fire-related risks for any future permanent risk informed license amendment request.

4.0 REGULATORY COMMITMENTS The licensee agreed to the following regulatory commitments in its original submittal:

4. No test and maintenance that affects equipment reliability associated with the operable CSS train or CCS will be scheduled during the CSS out of service time.

Subsequent to the original submittal, in response to staff RAIs, the licensee supplemented the original commitment with the following commitments per Reference 2:

1. Section 6.4 of CE-NPSD-1045-A includes the following suggested compensatory measures, which Entergy commits to implement:

a. While performing maintenance on the CSS train components, do not disable other components that are used for containment heat removal.

b. Prior to performing maintenance on one CSS equipment train, assure that the backup train is properly aligned and would be expected to perform its function if required.

c. Conduct a briefing with appropriate plant personnel to ensure that they are aware of the impact associated with unavailable components and flowpaths.

d. If a maintenance action or repair is to be performed, pre-stage parts and tools to minimize outage time.

e. Consider actions that could be taken to return the affected train to functional use, if not full operability, if the need arises or plan for backup systems (e.g., containment fan coolers) to be available.

f. In repairing and/or testing components (particularly valves), define the appropriate valve position (open/closed) that provides the greater level of safety and if practical establish that position for the repair.

5. ANO-2 will not commence maintenance activities on the CSS for an extended AOT if any of the following conditions exist:

a. Seismic Event (earthquake) as indicated by the earthquake trigger or noticeable abnormal vibrations in major structures.

b. Tornado watch or warning for Pope, Yell, Logan, or Johnson counties is in effect.

c. Tornado is sighted locally.

d. Loss of Dardanelle Reservoir is forecast[ed].

e. Flooding or forecasted flooding of Lake Dardanelle.

6. When performing maintenance activities on either train of the CSS, the redundant CSS train and the CCS will be protected (i.e., no testing or maintenance activities will be allowed).

7. Ensuring the ignition source probability is as low as possible in the turbine building to maintain the availability of off-site power will be accomplished by posting an hourly roving fire watch in that area. A roving fire watch will also be posted in other risk significant areas which include: the operable CSS train, the CCS, the HPSI system, both EFW trains, and the AFW system.

Further, in its supplemental submission letter dated September 26, 2006, the licensee enclosed the marked-up pages for the changes to the TS Bases reflecting the commitment numbers 2 through 4 above.

The NRC staff finds that reasonable controls for the implementation and for subsequent evaluation of proposed changes pertaining to the above regulatory commitments are provided by the licensee's administrative processes, including its commitment management program. In addition, the licensee has revised the TS Bases section to discuss implementation of the above commitments as necessary on a temporary basis.

5.0 STATE CONSULTATION

In accordance with the Commission's regulations, the Arkansas State official was notified of the proposed issuance of the amendment. The State official had no comments.

6.0 ENVIRONMENTAL CONSIDERATION

The amendment changes a requirement with respect to installation or use of a facility component located within the restricted area as defined in 10 CFR Part 20. The NRC staff has determined that the amendment involves no significant increase in the amounts, and no significant change in the types, of any effluents that may be released offsite, and that there is no significant increase in individual or cumulative occupational radiation exposure. The Commission has previously issued a proposed finding that the amendment involves no significant hazards consideration, and there has been no public comment on such finding published January 3, 2006 (71 FR 148). Accordingly, the amendment meets the eligibility criteria for categorical exclusion set forth in 10 CFR 51.22(c)(9). Pursuant to 10 CFR 51.22(b) no environmental impact statement or environmental assessment need be prepared in connection with the issuance of the amendment.

7.0 CONCLUSION

The staff finds that the licensee's proposed changes to revise, on a temporary basis, the AOT for TS 3.6.2.1 from 72 hours8.333333e-4 days <br />0.02 hours <br />1.190476e-4 weeks <br />2.7396e-5 months <br /> to 7 days are acceptable because the five key principles of risk-informed decisionmaking, identified in RG 1.174 and RG 1.177, have been satisfied only as an one-time extension. The staff notes that the application, as submitted, would not be acceptable as a permanent change and the licensee would need to explicitly and quantitatively address the large early release metrics and fire-related risks for any future permanent risk-informed license amendment request.

The staff has concluded, based on the considerations discussed above, that: (1) there is reasonable assurance that the health and safety of the public will not be endangered by operation in the proposed manner, (2) such activities will be conducted in compliance with the Commission's regulations, and (3) the issuance of the amendments will not be inimical to the common defense and security or to the health and safety of the public.

8.0 REFERENCES

1. Letter from Jeffery S. Forbes, Entergy Operations, Inc., to U.S. Nuclear Regulatory Commission, License Amendment Request to Allow One-Time Extension of Containment Spray System Allowable Outage Time - Arkansas Nuclear One, Unit 2 - Docket No. 50-368 - License No. NPF-6, 2CAN090502, September 19, 2005.

2. Letter from Thomas A. Marlow, Entergy Operations, Inc., to U.S. Nuclear Regulatory Commission, Supplement to Amendment Request to Allow One-Time Extension of Containment Spray System Allowable Outage Time - Arkansas Nuclear One, Unit 2 - Docket No. 50-368 - License No. NPF-6, 2CAN020602, February 28, 2006.

3. Letter from Thomas A. Marlow, Entergy Operations, Inc., to U.S. Nuclear Regulatory Commission, Supplement to Amendment Request to Allow One-Time Extension of Containment Spray System Allowable Outage Time - Arkansas Nuclear One, Unit 2 - Docket No. 50-368 - License No. NPF-6, 2CAN090602, September 26, 2006.

Principal Contributor: D. Harrison Date: September 28, 2006

Arkansas Nuclear One, Unit No. 2 cc:

Senior Vice President Vice President, Operations Support

& Chief Operating Officer Entergy Operations, Inc.

Entergy Operations, Inc. P. O. Box 31995 P. O. Box 31995 Jackson, MS 39286-1995 Jackson, MS 39286-1995 Wise, Carter, Child & Caraway Director, Division of Radiation P. O. Box 651 Control and Emergency Management Jackson, MS 39205 Arkansas Department of Health 4815 West Markham Street, Slot 30 Little Rock, AR 72205-3867 Winston & Strawn 1700 K Street, N.W.

Washington, DC 20006-3817 Senior Resident Inspector U.S. Nuclear Regulatory Commission P. O. Box 310 London, AR 72847 Regional Administrator, Region IV U.S. Nuclear Regulatory Commission 611 Ryan Plaza Drive, Suite 400 Arlington, TX 76011-8064 County Judge of Pope County Pope County Courthouse Russellville, AR 72801 September 2005