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#REDIRECT [[NL-08-054, Request for Extension of Completion Dates for Indian Point, Units 2 & 3, Corrective Actions Required by Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Wat]]
| number = ML080990085
| issue date = 03/28/2008
| title = Request for Extension of Completion Dates for Indian Point, Units 2 & 3, Corrective Actions Required by Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Wate
| author name = Pollock J E
| author affiliation = Entergy Nuclear Indian Point 2, LLC, Entergy Nuclear Indian Point 3, LLC
| addressee name =
| addressee affiliation = NRC/Document Control Desk, NRC/NRR
| docket = 05000247, 05000286
| license number =
| contact person =
| case reference number = GL-04-002, NL-08-054, TAC MC4689, TAC MC4690
| document type = Letter
| page count = 14
| project = TAC:MC4689, TAC:MC4690
| stage = Request
}}
 
=Text=
{{#Wiki_filter:Indian Point Energy Center 450 Broadway, GSB P.O. Box 249 Buchanan, N.Y. 10511-0249 Tel (914) 734-6700 J.E. Pollock Site Vice President Administration March 28, 2008 Indian Point Nuclear Generating Unit Nos. 2 and 3 Docket No. 50-247 and 50-286 NL-08-054 U.S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555-0001
 
==SUBJECT:==
Request for Extension of Completion Dates for Indian Point Units 2 and 3 Corrective Actions Required by Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors"
 
==REFERENCES:==
: 1) NRC Generic Letter 2004-02, 09/13/04, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" 2) Entergy letter NL-07-074, 09/17/07, "Request for Extension of Completion Date for Indian Point Unit 2 Corrective Actions and Modifications Required by Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" 3) Entergy letter NL-07-129, 11/30/07, "Revised Request for Extension of Completion Date for Indian Point Unit 3 Corrective Actions and Modifications Required by Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" 4) NRC letter to M.A. Balduzzi, 11/20/07, "Indian Point Nuclear Generating Unit No. 2 -Approval of Extension Request for Corrective Actions Required by Generic Letter 2004-02 (TAC No. MC4689)" 5) NRC letter to M.A. Balduzzi, 12/20/07, "Indian Point Nuclear Generating Unit No. 3-Approval of Revised Extension Request for Corrective Actions Required by Generic Letter 2004-02 (TAC No. MC4690)"
NL-08-054 Page 2 of 3
 
==Dear Sir or Madam:==
In Generic Letter (GL) 2004-02 (Reference 1), the NRC requested licensees to perform a mechanistic evaluation of the potential for the adverse effects of post-accident debris blockage and operation with debris-laden fluids to impede or prevent the recirculation functions of the Emergency Core Cooling System (ECCS) and Containment Spray System (CSS) following all postulated accidents for which these systems are required.
The GL requested that all licensees complete the GL related actions by December 31, 2007. The extension requests and NRC granted approvals (References 2 through 5) extended the completion dates to restart following the spring 2008 refueling outage (Unit 2) and June 30, 2008 (Unit 3). The intent of these extensions was to allow Entergy additional time to perform the final corrective actions, facility modifications, and all licensing activities to achieve compliance with GL 2004-02.This letter requests additional extensions to the completion dates for corrective actions required by GL 2004-02 for Indian Point Units 2 and 3. Entergy is requesting additional extensions owing to developments in test and analysis areas that include debris and chemical testing (including the failure of a test loop), debris erosion and capture, downstream effects, and head loss correlation use. The failure of a test loop resulted in a partial repeat of the 30 day chemical effects test and the other developments will result in the reanalysis of debris transport, strainer qualification and associated evaluations.
The facility modifications described in the earlier extension requests will be installed as scheduled during the currently in progress refueling outage (Unit 2) and by June 30, 2008 (Unit 3). The latter date is contingent on prior NRC approval of the associated license amendment.
There are no additional hardware modifications required for GL 2004-02 compliance identified at this time.This letter requests Units 2 and 3 extensions until October 31, 2008, to complete analysis and licensing activities determined to be needed to achieve compliance with the regulatory requirements of GL 2004-02. The basis for the proposed extensions is provided in Attachment 1.Entergy respectf ully requests approval of this extension request by April 9, 2008.There are no new commitments being made in this submittal.
Should you have any questions or require additional information, please contact Mr. R. Walpole, Manager, Licensing at (914) 734-6710.I declare under the penalty of perjury that the foregoing is true and correct. Executed on March 2? ,2008.Sincerely, J. E. Pollock Site Vice President Indian Point Energy Center NL-08-054 Page 3 of 3 Attachments:
: 1. Request for Extension of Completion Dates for Indian Point Units 2 and 3 Corrective Actions Required by Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" cc: Mr. John P. Boska, Senior Project Manager, NRC NRR DORL Mr. Samuel J. Collins, Regional Administrator, NRC Region 1 NRC Resident Inspector, IP2 NRC Resident Inspector, IP3 Mr. Paul D. Tonko, President, NYSERDA Mr. Paul Eddy, New York State Dept. of Public Service ATTACHMENT 1 TO NL-08-054 Request for Extension of Completion Dates for Indian Point Units 2 and 3 Corrective Actions Required by Generic Letter 2004-02, "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" ENTERGY NUCLEAR OPERATIONS, INC.INDIAN POINT NUCLEAR GENERATING UNIT NOs. 2 and 3 DOCKET NO. 50-247 and 50-286 NL-08-054 Attachment 1 Page 1 of 10 Request for Extension of Completion Dates for Indian Point Units 2 and 3 Corrective Actions Required by Generic Letter 2004-02 1.0 Background In Generic Letter (GL) 2004-02 (Reference 1), the NRC requested licensees to perform a mechanistic evaluation of the potential for the adverse effects of post-accident debris blockage and operation with debris-laden fluids to impede or prevent the recirculation functions of the Emergency Core Cooling System (ECCS) and Containment Spray System (CSS) following all postulated accidents for which these systems are required.
The GL requested that all licensees complete the GL related actions by December 31, 2007. By letters dated September 1, 2005 (Reference 2)December 15, 2005 (Reference 3), and February 28, 2008 (Reference 4), Entergy provided responses to GL 2004-02 for Indian Point Units 2 and 3.The extension requests and NRC granted approvals (References 5 through 8) extended the completion dates to restart following the spring 2008 refueling outage (Unit 2) and June 30, 2008 (Unit 3). The intent of these extensions was to allow Entergy additional time to perform the final corrective actions, facility modifications, and all licensing activities to achieve compliance with GL 2004-02.This letter requests additional extensions to the completion dates for corrective actions required by GL 2004-02 for Indian Point Units 2 and 3. Entergy is requesting additional extensions owing to developments in test and analysis areas that include debris and chemical testing (including the failure of a test loop), debris erosion and capture, debris transport including pool turnovers, downstream effects, and head loss correlation use. The failure of a test loop resulted in a partial repeat of the 30 day chemical effects test and the other developments will result in the reanalysis of debris transport, strainer qualification and associated evaluations.
The facility modifications described in the earlier extension requests will be installed as scheduled during the currently in progress refueling outage (Unit 2) and by June 30, 2008 (Unit 3). The latter date is contingent on NRC approval of the associated license amendment.
There are no additional hardware modifications required for GL 2004-02 compliance identified at this time.During the spring 2006 (Unit 2) and spring 2007 (Unit 3) refueling outages, the original.
internal recirculation and containment sump screens were replaced by strainers.
Other significant attendant modifications were also made including flow channeling.
These modifications represent a significant improvement over the original design by providing greatly increased strainer surface areas, reduced debris transport and reduced downstream effects. The evaluations of the adequacy of the strainer design to handle the predicted post LOCA debris and chemical loads have continued.
These evaluations showed that in order to ensure compliance with the regulatory requirements of GL 2004-02, additional modifications and License Amendments are required as described in 2. 1 Additional Modifications and 2.2 License Amendments.
 
===2.0 Reason===
for the Request for Extension In response to GL 2004-02, Entergy is assessingthe impact that chemical effects may have on the debris head loss predicted on the ECCS recirculation sump screen. ALION Science & Technology performed the chemical effects evaluation associated with the Unit 2 and Unit 3 plant specific environment and assessed the impact on debris head loss. A significant part of this evaluation is the small scale combined integrated chemical effects head loss experiment performed at the VUEZ NL-08-054 Attachment 1 Page 2 of 10 test facility over a 30 day period. The results of this test are being used to develop chemical effects increase (bump-up) factors to apply to prototype screen debris head loss testing results.During the VUEZ testing that commenced in November 2007, one of the four test loops failed due to a problem associated with the test apparatus that necessitated a 30 day retest of that loop. This retest impacted the resolution schedule by approximately 2 months due to the unavailability of the VUEZ test facility.
The NRC witnessed the test setup and conduct of the initial Indian Point test at VUEZ and has developed a list of questions and issues on the 30 day test program. In addition, during December 2007, the NRC conducted an audit of corrective actions Entergy has taken to address GL 2004-02. The audit included a review of the new sump designs and associated analyses, evaluations, testing and modifications for Units 2 and 3. The NRC has documented a number of draft audit items (Reference
: 9) that include VUEZ testing issues, debris head loss testing, debris capture and erosion assumptions, debris transport including pool turnovers, and downstream effects (including in-vessel) evaluations that are under development.
Entergy's resolution of these issues is ongoing and may involve reanalysis and the need to credit conservatisms in other areas to balance chemical effects and other issues. Should this approach not be viable for resolution of the chemical effects issues, then a retest may be necessary.
Limited retesting can be accommodated within the planned schedule, however, this extension request does not include time for a full repeat of the VUEZ 30 day test, should it be required.Entergy described in References 5 and 6 a licensing approach to the resolution of GL 2004-02 that involved utilization of the Alternate Break Methodology which would have required an exemption to the single failure requirements of 10CFR 50.46(d).
As Entergy's resolution activities have developed and performance capabilities of the internal and containment sumps assessed, Entergy has determined that use of the Alternate Break Methodology and the exemption will not be required.
Entergy now plans with prior NRC approval, to revise the single passive failure analysis and recirculation phase backup capability as documented in Reference 10.The results from the VUEZ testing, including the failed loop retest results, indicate chemical bump-up factors higher than originally anticipated and represent a challenge to strainer qualification.
Entergy has developed an action plan to address these bump-up factors and the above described issues. Planned activities include limited testing, license amendments (already submitted) and re-analysis.
Certain of these activities will not be completed by startup from the spring 2008 refueling outage (Unit 2) and by June 30, 2008 (Unit 3), therefore, additional extensions are required.
There are no additional hardware modifications required for GL 2004-02 compliance identified at this time.2.1 Additional Modifications The following outstanding modifications were identified in the earlier extension requests and remain considered necessary to bring the installation into compliance with GL 2004-02: Unit 2 (1) Containment Sump Buffering Agent Replacement A measure expected to significantly reduce the magnitude of chemical effects is the replacement of the TSP buffer with Sodium Tetraborate.
The NRC has issued the associated license amendment (Reference 11).(2) Installation of screens on certain crane wall penetrations NL-08-054 Attachment 1 Page 3 of 10 (3) Installation of grating on the containment sump trench (4) Screen modification to sump level instrument LT-938 housing (5) Installation of containment sump extension strainers in the annulus outside the crane wall that completes the strainer installation Unit 3 (1) Containment Sump Buffering Agent Replacement A measure expected to significantly reduce the magnitude of chemical effects is the replacement of the Sodium Hydroxide buffer with Sodium Tetraborate.
The NRC is currently reviewing the associated license amendment request (Reference 12)2.2 License Amendments and Licensing Basis Changes The following outstanding license amendments and licensing basis changes are considered necessary to bring the installation into compliance with GL 2004-02: Units 2 and 3 (1) Proposed Change to the Updated Final Safety Analysis Report Regarding the Emergency Core Cooling System and Component Cooling Water System (Unit 2 only)Single Passive Failure Analysis and Recirculation Phase Backup Capability (Reference 10). There are no hardware changes associated with this proposed amendment.
The proposed changes to the current licensing basis establish a licensing basis that supports resolution of GL 2004-02 by changing the performance requirements of the containment sump.Unit 3 (1) Buffer replacement See 2.1 (1) above. The Technical Specifications specify the type and quantity of the buffering agent. A License Amendment is required to implement the change from Sodium Hydroxide to Sodium Tetraborate (Reference 12).3.0 Technical Basis for Proposed Extension Entergy considers that the conditions at Indian Point Units 2 and 3 meet the criteria identified in SECY-06-0078 (Reference
: 13) for extension beyond the completion date of December 31, 2007 specified in GL 2004-02. The SECY criteria are, Proposed extensions to permit changes at the next outage of opportunity after December 2007 may be acceptable if, based on the licensee's request, the staff determines that:
NL-08-054 Attachment 1 Page 4 of 10" The licensee has a plant-specific technical/experimental plan with milestones and schedule to address outstanding technical issues with enough margin to account for uncertainties.
* The licensee identifies mitigative measures to be put in place prior to December 31, 2007, and adequately describes how these mitigative measures will minimize the risk of degraded ECCS [emergency core cooling system] and CSS [containment spray system] functions during the extension period.For proposed extensions beyond several months, a licensee's request will more likely be accepted if the proposed Mitigative measures include temporary physical improvements to the ECCS sump or materials inside containment to better ensure a high level of ECCS sump performance.
Indian Point Units 2 and 3 meet these criteria as described below.3.1 Plant Specific TechnicallExperimental Plan In Reference 2, Entergy submitted a description of the actions it is taking to address GL 2004-02, and updated that response in References 3 and 4. The key actions of the plan are summarized below.The following corrective action activities in association with the resolution of GL 2004-02 have been completed:
Miscellaneous o Containment walkdowns to identify and quantify the types and locations of potential debris sources 0 Programmatic and procedural enhancements Hardware o Installation of replacement IR and VC sump passive strainers o Installation of flow channeling barriers to enhance debris settlement o Installation of a debris trash rack on the fuel transfer canal drain to preclude blockage and consequential water holdup Testing o Dissolution/erosion measurements of plant specific calcium silicate (Unit 2)o Strainer head loss testing -debris only o Chemical effects testing at Vuez Analysis o Debris generation analyses o Initial debris transport analyses o Strainer head loss qualification
-debris only (Unit 2 and Unit 3 (preliminary))
o Clean screen head loss evaluation" Post-accident containment water level calculations (subject to revision)o Evaluation of ECCS pumps to the requirements of WCAP-1 6406-P Rev. 0" Initial available net positive suction head (NPSHA) analysis NL-08-054 Attachment 1 Page 5 of 10 o Component (excluding pumps and in-vessel) downstream effects evaluations o Fuel blockage downstream effects evaluations Licensing o Submittal of buffer replacement license amendment request (Units 2 and 3).o Preparation and submittal of a passive failure and backup capability related licensing basis change request (Units 2 and 3)In order to meet the regulatory requirements, Entergy has scheduled the following activities.
Hardware o Installation of buffer replacement modification packages (Units 2 and 3).It is planned to replace the Unit 2 buffer during the spring 2008 refueling outage It is planned to replace the Unit 3 buffer by June 30, 2008. However, the replacement is contingent on prior NRC approval of the associated license amendment request with sufficient time to implement the change. Therefore, the buffer change will be implemented within 60 days of the approval of the amendment or by June 30, 2008, whichever is later.o Installation of a VC sump strainer extension outside the crane wall and miscellaneous other modifications (Unit 2)It is planned to install these modifications during the spring 2008 refueling outage Analysis o Resolution of NRC audit open items and supporting activities (Units 2 and 3)The December 2007 NRC audit (Reference
: 9) identified a number of draft open items. These open items potentially impact debris and chemical testing, debris erosion and capture assumptions, debris transport including pool turnovers, downstream effects, and head loss correlation use, amongst others. While Entergy is confident that these open items can be resolved without impacting ultimate strainer qualification, a number of reports, evaluations and analyses have to be either generated or revised prior to strainer qualification.
o Revision to debris transport analyses (Units 2 and 3)The debris transport analyses need to be revised to incorporate the latest debris generation results, and NRC open items in the areas of fiber and calcium silicate erosion, and pool turnover issues. These analyses are currently scheduled for completion by May 28, 2008 (Unit 2) and July 9, 2008 (Unit 3).o Strainer head loss qualification including debris and chemical effects (Units 2 and 3)
NL-08-054 Attachment 1 Page 6 of 10 Strainer qualification is dependent on the results of the debris transport analyses, resolution of the NRC open items, and bump-up factors derived from the chemical effects testing. The strainer qualification is currently scheduled for completion by July 17, 2008 (Unit 2) and-Aug 27, 2008 (Unit 3)o Downstream effects evaluations of ECCS pumps and in-vessel (Units 2 and 3)The ECCS pumps were originally evaluated to the requirements of WCAP-1 6406-P Rev. 0 and found to be acceptable.
A re-evaluation of the ECCS pumps is in progress to the requirements of WCAP-1 6406-P Rev. 1. These evaluations are scheduled for completion by July 8, 2008 for both units. These evaluations include abrasive wear evaluations of pump seals and bearings.
The WCAP does not include the internal recirculation pump bearing material.
Entergy plans to conduct tests of this bearing material (nickel-carbon) to provide material properties for determining bearing wear. This extension request does not provide time for pump bearing replacement should the evaluation determine unfavorable bearing wear.The in-vessel evaluation is in progress to the requirements of WCAP-1 6793 and is scheduled for completion May 14, 2008 for both units.o Revision to NPSHA analyses (Units 2 and 3)It is planned to revise the NPSHA analyses of record concurrent with the strainer certifications.
Licensing It is planned to implement the passive failure related licensing basis changes discussed above prior to October 31, 2008. However, implementation is contingent on prior NRC approval with sufficient time to implement the change. In order to support the October 31, 2008 date it is assumed that the NRC will approve the submittal by August 31, 2008.The extent of the modifications and analyses already performed and those in progress and planned demonstrate that Entergy has developed a plant-specific technical/experimental plan, with milestones and schedule to address outstanding technical issues including sufficient margin to account for uncertainties.
 
===3.2 Mitigative===
 
Measures The mitigative measures described in References 5 and 6.are already in place and minimize the risk of degraded ECCS and CSS functions.
These measures include installation of replacement internal recirculation and containment sump strainers, replacement of the internal recirculation pumps, installation of flow channeling modifications, implementation of mitigative measures in response to NRC Bulletin 2003-01 (References 14 through 17), and procedural enhancements in the areas of containment cleanliness, foreign material exclusion and insulation control.In addition, the following mitigative measures will be in place during the additional extension period.
NL-08-054 Attachment 1 Page 7 of 10 Unit 2 (1) Containment Sump Buffering Agent Replacement (2) Installation of screens on certain crane wall penetrations (3) Installation of grating on the containment sump trench (4) Screen modification to sump level instrument LT-938 housing (5) Installation of containment sump extension strainers in the annulus outside the crane wall that completes the strainer installation Unit 3 (1) Containment Sump Buffering Agent Replacement (contingent on prior NRC approval)3.3 Generic Letter 2004-02 Basis for Continued Operation In addition to the mitigative measures identified above the basis for continued operation provided by GL 2004-02 include a number of factors that remain applicable to Indian Point Units 2 and 3 during the period of the proposed extension.
The NRC staff provided a justification for continued operation (JCO) (as discussed in Reference 1), that justifies continued operation of pressurized water reactors through December 31, 2007.Elements of the JCO applicable to Units 2 and 3 include: (1) The containment is compartmentalized making transport of debris to the sump difficult.
(2) Switchover to recirculation from the sump during a LBLOCA would not occur until 20 to 30 minutes after accident initiation, allowing time for much of the debris to settle in other places within containment.
(3) The probability of the initiating event (i.e., large and intermediate-break LOCAs) is extremely low.(4) Leak-before-break (LBB) has been approved by the NRC in relation to breaks in the reactor coolant loop primary piping. Qualified piping is of sufficient toughness that it will most likely leak rather than rupture.(5) The NPSH analyses for the IR and the RHR pumps do not credit containment overpressure.
3.4 Risk Analysis With the installation of the new strainers, flow channeling and other associated modifications there has been a significant reduction in the vulnerability to debris blockage and downstream effects as compared to the original physical configuration.
There will be a further significant reduction in vulnerability following buffer replacement (Units 2 and 3) and the installation of the Unit 2 containment sump strainers outside the crane wall.
NL-08-054 Attachment 1 Page 8 of 10 The period of extension from the original compliance date to the requested compliance date (from December 31, 2007 through October 31, 2008) represents a very small increase in incremental risk for the following reasons: 1) During a LBLOCA the flowrates through the strainers would be at maximum because the internal recirculation pumps would be supplying both cold leg recirculation and recirculation spray flow requirements with minimal system backpressure.
The LBLOCA Zones of Influence (ZOls) are larger than the ZOIs for intermediate and small beak LOCAs. The LBLOCAs therefore generate significantly more debris resulting in more debris transport to the sump strainers and higher sump strainer head loss. However, a LBLOCA has a very low probability of occurrence.
: 2) The more probable intermediate and small break LOCAs have significantly less potential for debris generation and transport due to the lower ZOls and reduced flowrates.
: 3) There are two sumps in containment
-the internal recirculation sump and the smaller containment sump. The internal recirculation sump is the primary sump used for accident mitigation and the containment sump provides backup capability should the recirculation sump fail due to blockage.4) There are four low head pumps available for accident mitigation
-two internal recirculation pumps that draw from the internal recirculation sump and two residual heat removal pumps that draw from the containment sump. Should an internal recirculation pump fail then the second recirculation pump would be available.
Should both internal recirculation pumps fail then the residual heat removal pumps would be available for accident mitigation.
: 5) The replacement strainers have 3/32" diameter holes versus the 1/8" original design. The downstream effects evaluation has shown that components are not subject to blockage.6) The replacement strainers consist of hollow concentric cylinders fitted with a bypass eliminator mesh. The bypass eliminator significantly reduces the total quantity of fiber that could bypass through strainer and therefore aids in mitigating downstream effects.7) Following the buffer replacement modifications the'head loss across the strainers will be reduced due to a significant reduction in the amount of chemical precipitates generated.
: 8) Following the installation of the Unit 2 containment sump extension strainers outside the crane wall the sump will be able to accommodate additional debris and chemical loads.For these reasons there is reasonable assurance that for intermediate and small break LOCAs the ECCS would continue to provide adequate core cooling.Th'us the following quantitative risk evaluation addresses potential vulnerability for large break, LOCAs only. Even though there are two sumps in containment and four ECCS pumps available for accident mitigation it is assumed here that both sumps and all four pumps fail at the initiation of recirculation.
It is further assumed that no credit is taken for recovery actions that would be available to the operators.
Therefore, all LBLOCAs (equivalent to pipe diameter of 6" and greater)are assumed to impact sump performance and lead to core damage.The frequency of the LBLOCA event is very low at 5x10 6/yr. Therefore, based on the above assumption that a LBLOCA cannot be mitigated, the annual increase in Core Damage Frequency (CDF) for each unit is taken to be 5x10-6/yr. This change is considered small and falls into Region II of the Acceptance Guidelines for CDF in Regulatory Guide (RG) 1.174. From the current Probabilistic Risk Assessment models, the baseline CDFs for internal events are 1.79x1 0-5/yr for Unit 2 and 1.15 x 10 5/yr for Unit 3. Since the contribution of external events to total baseline CDF is 6.33 x 10 5/yr (Unit 2) and 5.20x1 0- (Unit 3), even considering the change in risk due to the assumed inability to mitigate a LBLOCA, total CDF for each unit would still remain below 10-4 per yr. The Regulatory Guide (RG) 1.174 guidelines state that when the increase in CDF is between NL-08-054 Attachment 1 Page 9 of 10 10-6 per year and 10-5 per year, an application will be considered only if it can be reasonably shown that the total CDF is less than 10.4 per year. Since the risk associated with this application meets those guidelines, the CDF results remain very low and this risk assessment is considered acceptable for this application.
There is no significant contribution to Large Early Release Frequency (LERF) for loss of recirculation following Large LOCAs. External event contributions can also be neglected since they do not result in large LOCAs.4.0 References
: 1. NRC Generic Letter 2004-02, 09/13/04 "Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" 2. Entergy letter NL-05-094, 09/01/05 "Response to NRC Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" 3. Entergy letter NL-05-133, 12/15/05 "Supplemental Response to NRC Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" 4. Entergy letter NL-08-025, 02/28/08, "Supplemental Response to NRC Generic Letter 2004-02, Potential Impact Of Debris Blockage On Emergency Recirculation During Design Basis Accidents At Pressurized-Water Reactors" 5. Entergy letter NL-07-074, 09/17/07, "Request for Extension of Completion Date for Indian Point Unit 2 Corrective Actions and Modifications Required by Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" 6. Entergy letter NL-07-129, 11/30/07, "Revised Request for Extension of Completion Date for Indian Point Unit 2 Corrective Actions and Modifications Required by Generic Letter 2004-02, Potential Impact of Debris Blockage on Emergency Recirculation During Design Basis Accidents at Pressurized-Water Reactors" 7. NRC letter to M.A. Balduzzi, 11/20/07, "Indian Point Nuclear Generating Unit No. 2 -Approval of Extension Request for Corrective Actions Required by Generic Letter 2004-02 (TAC No.MC4689)" 8. NRC letter to M.A. Balduzzi, 12/20/07, "Indian Point Nuclear Generating Unit No. 3 -Approval of Revised Extension Request for Corrective Actions Required by Generic Letter 2004-02 (TAC No. MC4690)" 9. NRC letter to M.A. Balduzzi, 01/31/08, "Indian Point Nuclear Generating Unit Nos. 2 and 3 -Draft Open Items from Staff Audit of Corrective Actions to Address Generic Letter 2004-02 (TAC Nos. MC4689 and MC4690)" 10. Entergy letter NL-08-015, 03/13/08, "Proposed Change to the Updated Final Safety Analysis Report Regarding the Emergency Core Cooling System and Component Cooling Water System Single Passive Failure Analysis and Recirculation Phase Backup Capability" NL-08-054 Attachment 1 Page 10 of 10 11. NRC letter to M. A. Balduzzi, 02/07/08 "Indian Point Nuclear Generating Unit No. 2 -Issuance of Amendment Re: Changes to Technical Specifications to Replace Trisodium Phosphate Buffer with Sodium Tetraborate (TAC No. MD7182)" 12. Entergy letter NL-08-041, 02/28/08, "Proposed Changes to the Technical Specifications Regarding Replacement of the Sodium Hydroxide Buffer with Sodium Tetraborate Decahydrate" 13. SECY-06-0078, from L. A. Reyes, NRC Executive Director for Operations, to NRC Commissioners, 03/31/06 "Status of Resolution of GSI-191, Assessment of [Effect of] Debris Accumulation on PWR [Pressurized Water Reactor] Sump Performance" 14. NRC Bulletin 2003-01, 06/09/03 "Potential Impact of Debris Blockage on Emergency Sump Recirculation at Pressurized-Water Reactors" 15. Entergy letter NL-03-128, 08/07/03 "60 Day Response to NRC Bulletin 2003-01 Regarding Potential Impact of Debris Blockage of Emergency Sumps" 16. Entergy letter NL-04-151, 12/08/04 "Reply to RAI Regarding Bulletin 2003-01, Potential Impact of Debris Blockage on Emergency Sump Recirculation at Pressurized-Water Reactors" 17. NRC letter, 08/22/05 "Indian Point Nuclear Generating Unit Nos. 2 and 3- Response to NRC Bulletin 2003-01, Potential Impact of Debris Blockage on Emergency Sump Recirculation at Pressurized-Water Reactors (TAC Nos. MB9582 and MB9583)"}}

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