Text

Emergency License Amendment Request Extension of ANO-2 Emergency Diesel Generator Allowed Outage Time
	ML102320053
Person / Time
Site:	Arkansas Nuclear
Issue date:	08/19/2010
From:	Berryman B; Entergy Operations
To:	; Document Control Desk, Office of Nuclear Reactor Regulation
References
	2CAN081009
	Download: ML102320053 (49)
	v • d • e

Entergy Operations, Inc.

1448 S.R. 333 Russellville, AR 72802 Tel 479-858-3110 Brad L. Berryman Acting Vice President, Operations Arkansas Nuclear One 2CAN081009 August 19, 2010 U.S. Nuclear Regulatory Commission Attn: Document Control Desk Washington, DC 20555

SUBJECT:

Emergency License Amendment Request Extension of ANO-2 Emergency Diesel Generator Allowed Outage Time Arkansas Nuclear One, Unit 2 Docket No. 50-368 License No. NPF-6

Dear Sir or Madam:

Pursuant to 10 CFR 50.90 and 10 CFR 50.91(a)(5), Entergy Operations, Inc. (Entergy) hereby requests the following emergency amendment for Arkansas Nuclear One, Unit 2 (ANO-2).

Currently, Technical Specification (TS) 3.8.1.1, AC Sources, requires an inoperable Emergency Diesel Generator (EDG) to be restored to service within 14 days or actions to place the unit in a shutdown condition initiated. 2K-4B, the green-train EDG for ANO-2 was removed from service at 0330 CDT on August 9, 2010, to support preventative and corrective maintenance activities.

ANOs practice is that scheduled maintenance activities not exceed 50% of the TS allowable outage time (AOT). During post maintenance testing activities approximately mid-way through the current 14-day AOT, crankcase pressure (or vacuum) was found to be out-of-specification high. Prompt troubleshooting and adjustments, including evaluation by offsite experts brought to the site, have not succeeded in resolving the condition. Based on current information, the EDG will require extensive repair and testing to address the condition. However, the remaining AOT period is not sufficient to permit a significant repair of the engine in light of unforeseen circumstances that may arise; therefore, Entergy requests a one-time extension of the current 14-day AOT to not more than 18 days.

The current 14-day AOT expires at 0330 CDT, Monday, August 23, 2010. Absent approval of the requested AOT extension, ANO-2 will then be required to reach Mode 3 by 0930 CDT the same day and Mode 5 by 1530 CDT the following day. Approval of the AOT extension will permit ANO-2 to avoid unnecessary transition risks associated with a unit shutdown.

In accordance with 10 CFR 50.91(a)(5), where the Commission finds that an emergency situation exists, in that failure to act in a timely way would result in derating or shutdown of a nuclear power plant, or in prevention of either resumption of operation or of increase in power output up to the plant's licensed power level, it may issue a license amendment involving no

2CAN081009 Page 2 of 3 significant hazards consideration without prior notice and opportunity for a hearing or for public comment. Whenever an emergency situation exists, a licensee requesting an amendment must explain why this emergency situation occurred and why it could not avoid this situation.

Based on the above information, the degraded crankcase vacuum condition was unexpected and could not have been foreseen. Without knowledge of this condition, appropriate planning to complete repairs and restore the EDG to an operable status within the current AOT was not possible. Therefore, Entergy believes the requirements for seeking this emergency request is justified.

An explanation of the proposed change is provided in Attachment 1. A markup of the affected TS page is contained in Attachment 2 of this submittal. A revised (clean) TS page is provided in Attachment 3.

Although Entergy requests approval based on a deterministic evaluation of the proposed change, risk insights have also been provided in Attachment 1. Attachments 4, 5, and 6 include specific cutsets supporting the risk evaluation.

The proposed change has been evaluated in accordance with 10 CFR 50.91(a)(1) using criteria in 10 CFR 50.92(c) and it has been determined that the changes involve no significant hazards consideration. The bases for these determinations are included in the attached submittal.

The proposed change does not include any new commitments.

Entergy requests approval of the proposed amendment by August 22, 2010. Once approved, the amendment shall be implemented without delay.

If you have any questions or require additional information, please contact Mark Giles at 479-858-4710.

I declare under penalty of perjury that the foregoing is true and correct. Executed on August 19, 2010.

Sincerely, BLB/dbb Attachments:

1. Analysis of Proposed Technical Specification Change

2. Proposed Technical Specification Changes (mark-up)

3. Proposed Technical Specification Changes (revised)

4. Base Case Top 25 CDF Cutsets With Descriptions

5. EDG 2K-4B Out of Service - Top 25 CDF Cutsets With Descriptions (Normal Weather)

6. EDG 2K-4B Out of Service - Top 25 CDF Cutsets With Descriptions (Severe Weather)

2CAN081009 Page 3 of 3 cc: Mr. Elmo E. Collins Regional Administrator U. S. Nuclear Regulatory Commission Region IV 612 E. Lamar Blvd., Suite 400 Arlington, TX 76011-4125 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 1 2CAN081009 Analysis of Proposed Technical Specification Change to 2CAN081009 Page 1 of 14

1.0 DESCRIPTION

This letter is an emergency request to amend Operating License NPF-6 for Arkansas Nuclear One, Unit 2 (ANO-2).

The proposed change permits a one-time extension of the Technical Specification (TS) allowed outage time (AOT) of a single ANO-2 Emergency Diesel Generator (EDG) from 14 days to 18 days.

2.0 PROPOSED CHANGE

The proposed change will revise TS 3.8.1.1, AC Sources, to permit the green-train EDG (2K-4B) to remain inoperable for an additional 4 days beyond its current 14-day AOT. This extension will be applied only to the current in-progress 2K-4B maintenance window. In order to support this one-time extension, the following Note 2 will be added, applicable to TS 3.8.1.1 Action b:

The 14-day allowable outage time (AOT) may be extended to up to 18 days for 2K-4B only, applicable to the maintenance window beginning August 9, 2010.

This footnote expires at 0330 CDT, August 27, 2010, or when 2K-4B is returned to an OPERABLE status, whichever is shorter.

Entergy proposes to maintain the 72-hour limitation of TS 3.8.1.1 Action b, Note 1, requiring the availability of the Alternate AC Diesel Generator (AACDG) while 2K-4B remains inoperable (see Section 3.0 below for further information). However, the proposed Note 2 will be applicable to the 14 days denoted in Note 1 in addition to being applicable to TS 3.8.1.1 Action b. Therefore, if the AACDG becomes inoperable at anytime prior to restoration of 2K-4B, either 2K-4B or the AACDG must be restored within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months , not to exceed the proposed extended AOT period of 18 days.

A markup of the associated TS page is included in Attachment 2 of this submittal. A revised (clean) page is provided in Attachment 3.

3.0 BACKGROUND

ANO-2 is equipped with two seismically qualified, class 1E, EDGs which supply emergency electrical power to the 4160 V vital AC busses. Each engine is designed to automatically start and tie-on to its respective 4160 V engineered safety features (ESF) bus in the event of a bus under-voltage condition on either the 4160 V bus or its associated 480 V load center. The EDGs also receive an auto start command on an ESF signal, but will not load unless a bus under-voltage condition exists.

Each EDG is designed to start automatically upon receipt of a start demand, attain rated speed and voltage within 15 seconds, and sequentially accept ESF loads. Each ANO-2 EDG is sized to accommodate loads up to all anticipated ESF actuated equipment.

to 2CAN081009 Page 2 of 14 The EDGs are also designed for manual operation from either the local control panel or the control room operating panel. This provision allows operation for surveillance testing and manual start and load operations, as well as local operations in an event where the control room may be rendered inaccessible.

The EDGs are described in Chapter 8.3.1.1.9 of the ANO-2 Safety Analysis Report (SAR).

In addition to the EDGs, ANO has installed a diesel generator pursuant to the requirements of 10 CFR 50.63, Loss of All Alternating Current Power, paragraph (c)(2), Alternate AC Source.

The AACDG is a 16 cylinder, four stroke, turbocharged, diesel engine driven generator rated at 4400 KW continuous output and 5320 KW overload. Its size is based on the capability to supply the licensing basis loss of offsite power (LOOP) loads of any one of the four vital buses, well in excess of that required to support its Station Blackout mission of 3100 KW. The AACDG is capable of supplying 4160 V power to ANO-1 vital buses A3 or A4, or ANO-2 vital buses 2A3 or 2A4. It can also supply non-vital 4160V buses A1 for ANO-1 or 2A1 for ANO-2.

The buses can be supplied in any combination as long as the total load does not exceed the engine peak load rating. The design consideration for the AACDG assumed the engine would be started from the control room and available to power the safety buses within 10 minutes of the diagnosis of a station blackout condition. The 10-minute criterion is a bounding value from Section 3.2.5 of NRC Regulatory Guide (RG) 1.155, Station Blackout, and 10 CFR 50.63(c)(2) such that, if demonstrated, precludes the necessity for performing a specific coping analysis.

The AACDG output was tied to an ANO-1 vital bus (A3) during startup program testing on March 22, 1995 and to an ANO-2 vital bus on October 11, 1995. These tests loaded the engine and measured voltage dip. During these tests, an actual blackout event was simulated and the time to energize the buses was recorded. In each case the time was less than the 10-minute criterion.

The AACDG is completely independent from off-site power and the EDGs. The AACDG, all support systems, and attendant electrical buses are housed in a dedicated building located outside the power block, inside the protected area fence. The AACDG is discussed in Section 8.3.3 of the ANO-2 SAR.

The AACDG is a non-Q, manually started and loaded alternate source of AC power.

Operation and loading of the AACDG is possible from the ANO-2 control room or locally. All operations involving the AACDG are directed by procedure OP-2104.037. This procedure contains instructions for operating under various circumstances such as starting, loading, unloading, aligning to electrical buses, emergency starting/loading, and starting/loading with failure of both controlling computers. The procedure also contains instructions for the quarterly full load test and an 18-month test that verifies starting and loading in less than 10 minutes.

The ANO-2 EDG 2K-4B is currently inoperable. Prior to inoperability, the EDG's availability over the previous 12 months was 100%. The ongoing repair schedule of 2K-4B will result in a final availability of greater than 92% (rolling 12 months), even if the EDG remains inoperable for up to 29 days.

2K-4B was removed from service at 0330 CDT, August 9, 2010, in support of a 24-month outage to perform maintenance checks and correct known component deficiencies. During post maintenance testing (PMT) operations, engine crankcase vacuum was noted to be in the normal range, up to an engine load of approximately 2100 KW. When the engine approached to 2CAN081009 Page 3 of 14 full load (2850 KW), engine vacuum degraded from a normal value of approximately -2.0 H2O vacuum to 0 H2O vacuum. All other engine and generator parameters remained at or near normal full load values.

Portions of the maintenance activities performed on 2K-4B during the 24-month outage involved components that create vacuum in the engine compartment. In general, these components were disassembled, inspected and cleaned to verify no degradation had occurred and to ensure these components would maintain high reliability. No significant issues were found with these vacuum components during initial inspection. Substantial investigations and checks were conducted which have led to a conclusion that the primary contributor to this condition is the crankcase oil separator.

This conclusion was supported through dedicated interaction with fleet engineers and maintenance experts. Applicable operating experience was also revisited. Two Fairbanks &

Morse representatives are currently on site and have been assisting with failure mode evaluations, troubleshooting, and repair/restoration efforts. Currently, no evidence suggesting cylinder or piston damage (a repair activity that would take up to an additional two weeks) has been discovered.

Ongoing activities include replacing the oil separator that supplies crankcase gases to the eductor, which supports a minimal pressure environment in the crankcase. This is expected to require an additional 3 days of work. This activity, coupled with final restoration and testing activities, will leave little time before the end of the 14-day AOT is reached.

Based on the above and the remaining known activities, Entergy believes the EDG can be repaired and restored to an operable status with minimal need for additional time. Entergy requests a 4-day extension of the current AOT to affect repairs, perform PMT and operability testing, and to account for any unforeseen conditions that may occur during the repair and restoration process.

4.0 TECHNICAL ANALYSIS

As stated previously, correction of the 2K-4B crankcase vacuum-related condition involves a significant and complex maintenance procedure. Time is not only required to complete repair and restorative testing, but also to prepare for the unexpected maintenance activity. Based on the possible solutions, it is unlikely 2K-4B can be restored to an operable status prior to the expiration of the current 14-day AOT, which ends at 0330 CDT, August 23, 2010. Therefore, to avoid unnecessary transitional risks associated with a plant shutdown, Entergy requests a one-time extension of the current AOT of up to a total of 18 days. This period is expected to support 2K-4B restoration and accommodate any unforeseen circumstances that may arise during repair and restoration.

The current 14-day AOT associated with TS 3.8.1.1 Action b requires several compensatory measures to remain in place until the affected EDG is restored to an operable status.

Compensatory measures include the following:

to 2CAN081009 Page 4 of 14

1. The local area weather conditions were evaluated prior to entering the EDG AOT for voluntary planned maintenance. An extended EDG AOT (EDG outage lasting more than 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months ) is not entered for voluntary planned maintenance purposes if weather forecasts for the local area are predicting severe weather conditions that could affect the switchyard or offsite power supply during the AOT period.

2. The condition of the switchyard, offsite power supply, and the grid were evaluated prior to entering the extended AOT for elective maintenance. An extended EDG AOT is not entered to perform elective maintenance when grid stress conditions are high such as during extreme summer temperatures and/or high demand.

3. No discretionary switchyard maintenance is allowed. In addition, no discretionary maintenance is allowed on the main, auxiliary, or startup transformers associated with the unit.

4. No maintenance or testing that affects the reliability of the ANO-2 train associated with the operable EDG is scheduled during the extended AOT. If any testing and maintenance activities must be performed while the extended AOT is in effect, a 10 CFR 50.65(a)(4) evaluation will be performed.

5. The Alternate AC Diesel Generator (AACDG) will be available as a backup to the inoperable EDG and will not be used for non-safety functions such as power peaking to the grid. After entering the extended AOT, the AACDG will be verified available every 8 hours9.259259e-5 days 0.00222 hours 1.322751e-5 weeks 3.044e-6 months and treated as protected equipment.

6. ANO-1 personnel will be notified to ensure no elective maintenance activities will be scheduled on the ANO-1 EDGs and will be made aware of the importance of the AACDG to ANO-2.

7. The steam driven emergency feedwater (EFW) pump will not be taken out of service for planned maintenance activities and will be treated as protected equipment.

8. The system dispatcher will be contacted once per day and informed of the EDG status, along with the power needs of the facility.

9. Should a severe weather warning be issued for the local area that could affect the switchyard or offsite power supply during the AOT, an operator will be available locally at the AACDG should local operation of the AACDG be required as a result of on-site weather-related damage.

10. ANO-2 on-shift Operations crews will discuss and review appropriate normal and emergency operating procedures upon or prior to assuming the watch for the first time after having scheduled days off while the AOT is in effect.

11. ANO-2 on-shift Operations crews will be briefed concerning the ANO-2 EDG activities, including compensatory measures established and the importance of promptly starting and aligning the AACDG following instruction of the ANO-2 Shift Manager upon a loss of offsite power event. This briefing will be performed upon or prior to assuming the watch for the first time after having scheduled days off while the AOT is in effect.

to 2CAN081009 Page 5 of 14

12. During the EDG outage, welding and transient combustibles will be controlled and continuous fire watch(es) established in the vicinity of the Turbine Building Switchgear (2A1/2A2/2A9).

13. During the EDG outage, welding and transient combustibles in the following areas will be controlled: the transformer yard; the south Switchgear Room (SS/2100-Z); the Cable Spreading Room (G/2098-L); Intake Structure (OO/IS);

Diesel Corridor (JJ/2109-U); Lower South Electrical/Piping Penetration Room (EE/2055SC); and Electrical Equipment Room (TT/2108-S).

14. Prior to the EDG outage, the ANO-2 Operations personnel and ANO-1 fire brigade personnel are briefed on information related to fighting electrical fires and fires that may occur in the transformer yard. The briefing will include relevant industry operating experience related to fires in these areas and will also include a discussion of equipment restoration.

15. Prior to the EDG outage, the operability of the fire suppression in the transformer yard will be confirmed. This will be accomplished by verifying that surveillances are current and the system is not isolated. If the system is isolated, then fire hoses will be staged to the transformer yard area during the EDG maintenance outage.

The above compensatory measures were found acceptable by the NRC when ANO-2 adopted the current 14-day AOT. These compensatory measures are discussed in the TS Bases associated with TS 3.8.1.1 and in site implementing procedures. All of the above compensatory measures will remain in place during the requested AOT extension associated with this submittal.

Note 1 of TS 3.8.1.1 Action b requires availability of the AACDG when an EDG is removed from service. If the AACDG becomes unavailable (inoperable), then the allowable outage time is reduced to 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months from the time the AACDG becomes unavailable, not to exceed 14 days from the initial entry related to the inoperable EDG. Either the AACDG or the EDG may be restored within the 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months . If the EDG is restored, then TS 3.8.1.1, Action b is exited. If the AACDG is restored within the 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months , then restoration of the EDG must be accomplished within the initial 14 day AOT (i.e. 14 days from the time the EDG was initially declared inoperable and Action b was entered).

Entergy proposes to maintain the 72-hour limitation of Note 1 to TS 3.8.1.1 Action b.

However, the proposed Note 2 (described in Section 2 above) will be applicable to the 14 days denoted in Note 1 in addition to being applicable to TS 3.8.1.1 Action b. Therefore, if the AACDG becomes inoperable at anytime prior to restoration of 2K-4B, either 2K-4B or the AACDG must be restored within 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months , not to exceed the proposed extended AOT period of 18 days.

The preceding information provides a deterministic basis supporting the acceptability of the extended EDG AOT. Substantial administrative controls and equipment protection measures have been established to limit the impact of the extended AOT. For additional information, the following risk insights are also provided.

to 2CAN081009 Page 6 of 14 An assessment of the change in the ANO-2 core damage frequency (CDF) due to allowing ANO-2 to continue at power operation beyond the TS restoration period of 14 days has been performed. A 4-day extension was evaluated to adequately bound the time that may be necessary to restore the green-train EDG system to an operable status.

In order to comply with the requirements of Regulatory Guide (RG) 1.177, An Approach for Plant Specific, Risk-Informed Decisionmaking: Technical Specifications, for a risk- informed TS change, the following 3 tiers are considered.

Tier 1 is an evaluation of the impact on plant risk of the proposed TS change as expressed by the change in CDF, the incremental conditional core damage probability (ICCDP), and, when appropriate, the change in large early release frequency (LERF) and the incremental conditional large early release probability (ICLERP).

Tier 2 is an identification of potentially high-risk configurations that could exist if equipment in addition to that associated with the change were to be taken out of service simultaneously, or other risk-significant operational factors such as concurrent system or equipment testing were also involved.

Tier 3 is the establishment of an overall configuration risk management program to insure that other potentially lower probability, but nonetheless risk-significant, configurations resulting from maintenance and other operational activities are identified and compensated for.

The analysis of the risk impact of removing the green-train EDG from service for an additional 4 days is performed using the ANO-2 Equipment Out-of-Service (EOOS) Model 4p2. This model assumes zero test and maintenance (T&M) for the various systems modeled in the Probabilistic Risk Assessment (PRA). Since the issue affecting the green-train EDG was due to a Maintenance activity, it does not affect the red-train EDG and AACDG. However, common cause failures (CCF) for start failure were elevated to CCF values assuming failure of the remaining components. The ANO-2 LERF Model was used to calculate ICLERP. The duration of the extended green-train EDG maintenance was assumed to be 4 days.

Tier 1 Several ANO-2 EOOS calculations were performed:

The CDF values generated are provided in Table 1.

to 2CAN081009 Page 7 of 14 Table 1 Quantitative CDF Estimates ANO-2 Case CDF (/rx-yr)

Case 1 Baseline (zero maintenance) 6.94E-07 Case 1A Baseline (zero maintenance) with severe weather 1.67E-06 Case 2 2K-4B OOS with no severe weather 1.89E-06 Case 2A 2K-4B OOS with severe weather 7.71E-06 Delta CDF (Case 2) = 1.89E 6.94E-7 1.20E-06 Delta CDF (Case 2A) = 7.71E 1.67E-7 6.04E-06 Delta CDF, average assuming severe weather 25% of the time 2.41E-06

= ((1.2*3 + 6.0.4)/4)

1E-6 Using these results, the estimated change in the annual and the cycle average ANO-2 CDF for an additional 4 days of power operation while 2K-4B is OOS is provided in Table 2.

Table 2 ICCDP for Extension of 2K-4B OOS Period 4 Days RG 1.177 ICCDP Beyond AOT (with severe weather 25% of the time) Guidance 2.41E-06*4/365 = 2.64E-08 ICCDP less than 5E-7 After doubling for External Events: 2

2.64E-08 = 5.28E-08 ICCDP less than 5E-7 As noted in the table, the change in the ANO-2 ICCDP associated with allowing a one-time extension of the 2K-4B OOS time beyond its current 14-day AOT is below the RG 1.177 threshold.

LERF values corresponding to these CDF values could not be quantitatively calculated for severe weather. Prorating the above CDF results for LERF, the net impact on LERF results is below the RG 1.177 threshold for ICLERP because the ANO-2 baseline LERF is more than an order of magnitude lower than the ANO-2 baseline CDF.

External Events Risk - Fire ANO-2 has recently developed a fire PRA model for NFPA-805 transition. However, turnover of this model to the PSA staff is not completed yet and, therefore, it could not be exercised in support of this application. Also, the ANO-2 NFPA 805 team is currently working on refining this model using recent industry pilot experience. It is judged that this model is not appropriate for the risk evaluation of this issue. Therefore, the ICCDP and ICLERP results were effectively doubled to account for external events including fire. The doubled results are still much lower than the RG 1.177 acceptance guidelines.

to 2CAN081009 Page 8 of 14 2K-4B is credited in the fire risk assessment for fire areas involving a loss of offsite power or 4.16 KV breakers and transformers that would cause an undervoltage on the 2A-4 (green-train) bus. Therefore, the qualitative risk of a fire is limited to fires in Fire Areas denoted in the list of compensatory measures near the beginning of Section 4.0 above. As discussed previously, hot work in these areas is being controlled and/or fire watches have been established in these areas until 2K-4B can be restored to an operable status in order to limit the likelihood and severity of any potential fires in these areas. These actions will reduce the fire risk for the proposed AOT extension.

External Events Risk - Seismic ANO-2 has been designed to accommodate a safe-shutdown earthquake (SSE) with 0.2g peak ground acceleration (PGA). The seismic analysis performed in the IPEEE study for ANO-2 is based on the Seismic Margins Analysis (SMA) methodology as defined in NUREG-1407.

The seismic analysis methodology implemented for ANO-2 satisfied the NRC requirements for performing a seismic IPEEE as presented in Generic Letter (GL) 88-20, Supplement 4, Individual Plant Examination of External Events (IPEEE) for Severe Accident Vulnerabilities.

Seismic events were evaluated using the SMA method. The SMA methodology uses a deterministic approach to identify the weakest components in terms of High Confidence Low Probability of Failure (HCLPF) during peak ground acceleration. A seismic margin can be expressed in terms of the earthquake motion level that compromises plant safety. The seismic margin assessment determines whether there is high confidence that the plant can survive a given earthquake. No core damage frequency sequences were quantified as part of the IPEEE seismic risk analysis.

The seismic analysis concentrated on verifying the seismic adequacy of structures, equipment, large tanks, cable tray conduit raceway systems, and other distribution systems and relays.

The screening and verification walk downs verified that the equipment, tanks, distribution systems, structures, and relays are able to withstand the 0.3g Review Level Earthquake at the plant and still provide for its safe shutdown. The HCLPF of the Emergency Cooling Pond (Dam and Reservoir) based on this review was estimated to be at least 0.5g. The containment structure was also evaluated seismically and it was determined that it has adequate strength and can be screened out.

For the proposed AOT extension, seismic delta risk is not expected to be a significant contributor, as there were no specific seismic vulnerabilities that were identified in this area.

Other External Hazards The ANO-2 IPEEE submittal examined the below hazards in addition to seismic and fire risk.

High winds External floods Nearby industrial and military facilities Toxic chemicals Aircraft crashes to 2CAN081009 Page 9 of 14 No vulnerabilities were identified in these areas for ANO-2. No appreciable impact on the subject request is expected from these hazards.

Based on the above and for the purposes of this assessment, the external events risk is assumed to be equal to the value of the internal events risk, i.e. the internal events delta risk was conservatively doubled to account for external events.

Sensitivity Case Due to the high ambient temperatures present during recent days in the region, another sensitivity case was performed increasing the grid instability factor to twice that as normal.

The ICCDP value for this case was found to be 1.91E-08, which is also within the RG 1.177 acceptance guidelines.

Tier 2 ANO-2 is addressing the inoperable condition associated with the green-train EDG. As a result of this effort, no maintenance or testing that affects the reliability of the ANO-2 train associated with the operable EDG is scheduled during the extended AOT. If any testing and maintenance activities must be performed while the extended AOT is in effect, a 10 CFR 50.65(a)(4) evaluation will be performed.. No discretionary switchyard maintenance will be allowed during the period of the green-train EDG inoperable condition. The red-train EDG and its support systems are currently considered protected.

As previously stated, ANO has at its disposal an AACDG. ANO-2 is committed to ensuring the AACDG remains available and protected for the duration of the EDG out-of-service window in order to effectively reduce the associated risks involved. In addition, extra precautions in the form of compensatory measures have been identified to assure that sources of power are protected to the extent practical and that precautions are taken with regard to the steam-driven emergency feedwater pump. These precautions are discussed under the compensatory measures section of this document and should further reduce the risk of the AOT extension.

Tier 3 In 2008, ANO-2 performed a major revision (Rev. 4p2) of the ANO-2 PRA model in order to meet the RG 1.200, Rev. 1, An Approach for Determining the Technical Adequacy of Probabilistic Risk Assessment Results for Risk-Informed Activities, standard. Also in 2008, an ANO-2 PRA Peer Review was performed on Revision 4p2 of the PSA model. The 2008 ANO-2 PRA Peer Review was a full-scope review of the Technical Elements of the internal events, at-power PRA.

The results of the peer review identified gaps to be addressed in order to ensure that the model fully complies with all of the requirements of the RG 1.200, Rev. 1 standard. Although gaps were identified, these gaps do not affect the ANO-2 PRA model in a manner that would change the outcome of the risk assessment performed as part of this submittal. The PRA is of sufficient quality to be used in assessing the risk of the TS change for the green-train EDG.

to 2CAN081009 Page 10 of 14 The risk of extending the TS AOT for the 2K-4B green-train EDG an additional 4 days is not considered significant and is well within the acceptance criteria defined in RG 1.177. Given the proposed compensatory measures, the evaluated risk of the extended AOT (although not required), and the avoidance of unnecessary shutdown transient risk, Entergy believes the proposed change is acceptable.

Conclusion In accordance with 10 CFR 50.91(a)(5), where the Commission finds that an emergency situation exists, in that failure to act in a timely way would result in derating or shutdown of a nuclear power plant, or in prevention of either resumption of operation or of increase in power output up to the plant's licensed power level, it may issue a license amendment involving no significant hazards consideration without prior notice and opportunity for a hearing or for public comment. Whenever an emergency situation exists, a licensee requesting an amendment must explain why this emergency situation occurred and why it could not avoid this situation.

Based on the above information, the degraded crankcase vacuum condition was unexpected and could not have been foreseen. Without knowledge of this condition, appropriate planning to complete repairs and restore the EDG to an operable status within the current AOT was not possible. Therefore, Entergy believes the requirements for seeking this emergency request is justified.

5.0 REGULATORY ANALYSIS

5.1 No Significant Hazards Consideration A change is proposed to the Arkansas Nuclear One, Unit 2 (ANO-2) Technical Specifications (TSs) to permit a one-time extension of the allowable outage time (AOT) for a single Emergency Diesel Generator (EDG) from 14 days to a total of 18 days. The following compensatory measures will remain effective until the green-train EDG 2K-4B is restored to an operable status or until ANO-2 is shutdown to Mode 5.

1. The local area weather conditions were evaluated prior to entering the EDG AOT for voluntary planned maintenance. An extended EDG AOT (EDG outage lasting more than 72 hours8.333333e-4 days 0.02 hours 1.190476e-4 weeks 2.7396e-5 months ) is not entered for voluntary planned maintenance purposes if weather forecasts for the local area are predicting severe weather conditions that could affect the switchyard or offsite power supply during the AOT period.

2. The condition of the switchyard, offsite power supply, and the grid were evaluated prior to entering the extended AOT for elective maintenance. An extended EDG AOT is not entered to perform elective maintenance when grid stress conditions are high such as during extreme summer temperatures and/or high demand.

3. No discretionary switchyard maintenance is allowed. In addition, no discretionary maintenance is allowed on the main, auxiliary, or startup transformers associated with the unit.

to 2CAN081009 Page 11 of 14