Similar Documents at Byron |
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Category:CORRESPONDENCE-LETTERS
MONTHYEARML20217P6171999-10-21021 October 1999 Forwards non-proprietary & Proprietary Versions of HI-982083, Licensing Rept for Byron & Braidwood Nuclear Stations. Proprietary Rept Withheld,Per 10CFR2.790(b)(4) ML20217M2871999-10-21021 October 1999 Refers to Rev 5 Submitted in May 1999 for Portions of Byron Nuclear Power Station Generating Stations Emergency Plan Site Annex.Informs That NRC Approval Not Required Based on Determination That Plan Effectiveness Not Decreased ML20217H4661999-10-18018 October 1999 Forwards Changes to EPIPs IAW 10CFR50.54(q) & 10CFR50,App E, Section V.Details of Changes Encl ML20217F7891999-10-0808 October 1999 Forwards Insp Repts 50-454/99-12 & 50-455/99-12 on 990803- 0916.One Violation Occurred Being Treated as NCV ML20217B6351999-10-0505 October 1999 Forwards for Info,Final Accident Sequence Precursor Analysis of Operational Event at Byron Station,Unit 1,reported in LER 454/98-018 & NRC Responses to Util Specific Comments Provided in ML20212L1791999-10-0505 October 1999 Informs That as Result of Staff Review of Util Responses to GL 92-01,rev 1,suppl 1 & Suppl 1 Rai,Staff Revised Info in Rvid & Is Releasing Rvid Version 2 ML20217B2991999-10-0101 October 1999 Forwards Insp Repts 50-454/99-16 & 50-455/99-16 on 990907-10.No Violations Noted.Water Chemisty Program Was Well Implemented,Resulted in Effective Control of Plant Water Chemistry ML20216J8241999-09-30030 September 1999 Notifies of Removal of NRC Headquarters & Region III Offices from Controlled Copy Distribution of Certain CE Documents. Specific Documents,Associated Controlled Copy Numbers & NRC Location Affected Are Shown on Attachment to Ltr ML20212J6751999-09-30030 September 1999 Forwards Replacement Pages Eight Through Eleven of Insp Repts 50-454/99-15 & 50-455/99-15.Several Inaccuracies with Docket Numbers & Tracking Numbers Occurred in Repts ML20217A5821999-09-29029 September 1999 Advises of NRC Plans for Future Insp Activities at Facility for Licensee to Have Opportunity to Prepare for Insps & to Provide NRC with Feedback on Any Planned Insps Which May Conflict with Plant Activities ML20216F8051999-09-17017 September 1999 Forwards Insp Rept 50-454/99-14 & 50-455/99-14 on 990823-27. Security Program Was Effectively Implemented in Areas Inspected.No Violations Were Identified ML20211P1841999-09-0808 September 1999 Forwards Insp Repts 50-454/99-15 & 50-455/99-15 on 990824- 26.No Violations Noted.Objective of Insp to Determine Whether Byron Nuclear Generating Station Emergency Plan Adequate & If Emergency Plan Properly Implemented ML20211Q6821999-09-0606 September 1999 Informs That NRC Tentatively Scheduled Initial Licensing Exam for Byron Operator Licesne Applicants During Wks of 000619 & 26.Validation of Exam Will Occur at Station During Wk of 000529 ML20211N5151999-09-0303 September 1999 Ack Receipt of Re Safety Culture & Overtime Practices at Byron Nuclear Power Station.Copy of Recent Ltr from NRC to Commonwealth Edison Re Overtime Practices & Safety Culture Being Provided ML20211K1081999-09-0202 September 1999 Responds to Request for Addl Info to GL 92-01,Rev 1,Suppl 1, Reactor Vessel Structural Integrity, for Braidwood,Units 1 & 2 & Byron,Unit 2 ML20211M1371999-09-0202 September 1999 Discusses 990527 Meeting with Ceco & Byron Station Mgt Re Overtime Practices & Conduciveness of Work Environ to Raising Safety Concerns at Byron Station.Insp Rept Assigned for NRC Tracking Purposes.No Insp Rept Encl ML20211G1221999-08-27027 August 1999 Forwards fitness-for-duty Program Performance Data for Each of Comm Ed Nuclear Power Stations & Corporate Support Employees within Scope of Rule for six-month Period Ending 990630,IAW 10CFR26.71(d) ML20211G4021999-08-25025 August 1999 Forwards Insp Repts 50-454/99-10 & 50-455/99-10 on 990622-0802.No Violations Noted ML20211B8691999-08-20020 August 1999 Forwards Insp Repts 50-254/99-10,50-265/99-10,50-454/99-09, 50-455/99-09,50-456/99-10 & 50-457/99-10 on 990628-0721. Action Plans Developed to Address Configuration Control Weaknesses Not Totally Effective as Listed 05000454/LER-1998-008, Informs That Licensee Determined That Suppl Rept to LER 98-008 Is Not Warranted.No Addl Info Was Generated Following Completion of Root Cause Investigation of Following Completion of Corrective Actions Stated in Original LER1999-08-12012 August 1999 Informs That Licensee Determined That Suppl Rept to LER 98-008 Is Not Warranted.No Addl Info Was Generated Following Completion of Root Cause Investigation of Following Completion of Corrective Actions Stated in Original LER ML20210N5651999-08-0606 August 1999 Forwards Rev 8 to Nuclear Generating Stations Emergency Plan, for Plants.With Summary of Changes ML20210M9131999-08-0202 August 1999 Forwards Response to NRC AL 99-02, Operating Reactor Licensing Action Estimates, for Fys 2000 & 2001 for Comed ML20210K0771999-07-30030 July 1999 Submits 30-day Rept Re Discovery of ECCS Evaluation Model Error for Byron & Braidwood Stations,As Required by 10CFR50.46 ML20210J8951999-07-29029 July 1999 Submits Other Actions,As Described,To Be Taken for Valves to Resolve Potential Pressure Locking Concerns,In Light of Extended Period for Valve Bonnet Natural Depressurization,In Response to GL 95-07, Pressure Locking & Thermal.. ML20210E2151999-07-23023 July 1999 Forwards Byron Unit 1 B1R09 ISI Summary Rept Spring 1999 Outage,980309-990424, in Compliance with Requirements of Article IWA-6000, Records & Repts of Section XI of ASME & P&PV,1989 Edition ML20209H2991999-07-16016 July 1999 Withdraws 980529 LAR to Credit Automatic PORV Operation for Mitigation of Inadvertent Safety Injection at Power Accident.Response to NRC 990513 RAI Re LAR Encl ML20210A3151999-07-16016 July 1999 Forwards Insp Repts 50-454/99-08 & 50-455/99-08 on 990511-0621.Three Violations Being Treated as Noncited Violations ML20210B7071999-07-16016 July 1999 Responds to Requesting Review & Approval of Three Proposed Changes to Ceco QA TR,CE-1A Per 10CFR50.54(a)(3) & 10CFR50.4(b)(7) ML20207H7501999-07-12012 July 1999 Forwards Revised Pressure Temp Limits Rept, for Byron Station,Units 1 & 2.Revised Pressurized Thermal Shock Evaluations,Surveillance Capsule Rept & Credibility Repts, Also Encl ML20209G1391999-07-0909 July 1999 Forwards Results of SG Tube Insps Performed During Byron Station,Unit 1,Cycle 9 Refueling Outage within 12 Months Following Completion of Insps ML20196J9131999-07-0101 July 1999 Submits Status of Nuclear Property Insurance Currently Maintained for Braidwood,Byron,Dresden,Lasalle County,Quad Cities & Zion Nuclear Power Stations,Per 10CFR50.54(w)(3) ML20196J9061999-07-0101 July 1999 Provides Evidence That Util Maintains Guarantee of Payment of Deferred Premiums in Amount of $10 Million for Each of Thirteen Reactors,Per 10CFR140.21 ML20209B8241999-06-30030 June 1999 Forwards Five 3.5 Inch Computer Diskettes Containing Revised Annual Dose Repts for 1994 Through 1998 for Individuals Receiving Neutron Dose Not Previously Included in Reported Total Effective Dose Equivalent Values.Without Diskettes ML20196K0161999-06-30030 June 1999 Discusses 990622 Meeting at Byron Nuclear Power Station in Byron,Il.Purpose of Visit Was to Meet with PRA Staff to Discuss Ceco Initiatives in Risk Area & to Establish Dialog Between SRAs & PRA Staff ML20196G2161999-06-25025 June 1999 Forwards for NRC Region III Emergency Preparedness Inspector,Two Copies of Comed Emergency Preparedness Exercise Manual for 1999 Byron Station Annual Exercise. Exercise Is Scheduled for 990825.Without Encls ML20212H8241999-06-24024 June 1999 Informs That Effective 990531 NRC Project Mgt Responsibility for Byron & Braidwood Stations Was Transferred to Gf Dick ML20209D4861999-06-17017 June 1999 Informs That R Heinen,License OP-30953-1 & a Snow,License SOP-30212-3,no Longer Require License at Byron Station 05000454/LER-1999-002, Forwards LER 99-002-00,IAW 10CFR50.73(a)(2)(i)(b).There Are Two Actions Remaining to Address Cause of Event.Both Actions Are Listed1999-06-0808 June 1999 Forwards LER 99-002-00,IAW 10CFR50.73(a)(2)(i)(b).There Are Two Actions Remaining to Address Cause of Event.Both Actions Are Listed ML20207G0601999-06-0707 June 1999 Provides Updated Info Re Number of Failures Associated with Initial Operator License Exam Administered from 980914-0918. NRC Will Review Progress Wrt Corrective Actions During Future Insps ML20207G0421999-06-0404 June 1999 Forwards Insp Repts 50-454/99-04 & 50-455/99-04 on 990330-0510.Violations Identified & Being Treated as non-cited Violations ML20195D6351999-06-0404 June 1999 Notifies NRC of Actions That Has Been Taken in Accordance with 10CFR26, Fitness for Duty Programs ML20207E5451999-05-28028 May 1999 Forwards Insp Repts 50-454/99-07 & 50-455/99-07 on 990517-20.No Violations Noted.Fire Protection Program Was Effective ML20211M1611999-05-28028 May 1999 Discusses 990527 Meeting with Comed Re Safety Culture & Overtime Control at Byron Nuclear Plant from Videoconference Location at NRC Headquarters.Requests That Aggressive Actions Be Taken to Ensure That Comed Meets Expectations ML20207D5261999-05-26026 May 1999 Forwards Response to NRC 990318 RAI Concerning Alleged Chilling Effect at Byron Station.Attachment Contains Responses to NRC 12 Questions ML20207B6361999-05-25025 May 1999 Forwards SE Accepting Revised SG Tube Rupture (SGTR) Analysis for Bryon & Braidwood Stations.Revised Analysis Was Submitted to Support SG Replacement at Unit 1 of Each Station ML20211M1781999-05-25025 May 1999 Summarizes Concerns with Chilling Effect & Overtime Abuses at Commonwealth Edison,Byron Station.Request That Ltr Be Made Part of Permanent Record of 990527 Meeting ML20195C7911999-05-25025 May 1999 Forwards Revised COLR for Byron Unit 2,IAW 10CFR50.59.Rev Accounts for Planned Increase of Reactor Coolant Full Power Average Operating Temp from 581 F to 583 F 05000454/LER-1999-001, Forwards LER 99-001-00,IAW 10CFR50.73(a)(2)(i)(B).Required Actions to Address Causes of Event Listed1999-05-21021 May 1999 Forwards LER 99-001-00,IAW 10CFR50.73(a)(2)(i)(B).Required Actions to Address Causes of Event Listed ML20206U3471999-05-20020 May 1999 Forwards Insp Rept 50-454/99-05 on 990401-22.No Violations Noted.Insp Reviewed Activities Associated with ISI Efforts Including Selective Exam of SG Maint & Exam Records, Calculations,Observation of Exam Performance & Interviews ML20207A2151999-05-19019 May 1999 Forwards Insp Repts 50-454/99-06 & 50-455/99-06 on 990419-23.No Violations Noted.Insp Consisted of Review of Liquid & Gaseous Effluent Program,Radiological Environmental Monitoring Program,Auditing Program & Outage Activities 1999-09-08
[Table view] Category:INCOMING CORRESPONDENCE
MONTHYEARML20217P6171999-10-21021 October 1999 Forwards non-proprietary & Proprietary Versions of HI-982083, Licensing Rept for Byron & Braidwood Nuclear Stations. Proprietary Rept Withheld,Per 10CFR2.790(b)(4) ML20217H4661999-10-18018 October 1999 Forwards Changes to EPIPs IAW 10CFR50.54(q) & 10CFR50,App E, Section V.Details of Changes Encl ML20216J8241999-09-30030 September 1999 Notifies of Removal of NRC Headquarters & Region III Offices from Controlled Copy Distribution of Certain CE Documents. Specific Documents,Associated Controlled Copy Numbers & NRC Location Affected Are Shown on Attachment to Ltr ML20211G1221999-08-27027 August 1999 Forwards fitness-for-duty Program Performance Data for Each of Comm Ed Nuclear Power Stations & Corporate Support Employees within Scope of Rule for six-month Period Ending 990630,IAW 10CFR26.71(d) 05000454/LER-1998-008, Informs That Licensee Determined That Suppl Rept to LER 98-008 Is Not Warranted.No Addl Info Was Generated Following Completion of Root Cause Investigation of Following Completion of Corrective Actions Stated in Original LER1999-08-12012 August 1999 Informs That Licensee Determined That Suppl Rept to LER 98-008 Is Not Warranted.No Addl Info Was Generated Following Completion of Root Cause Investigation of Following Completion of Corrective Actions Stated in Original LER ML20210N5651999-08-0606 August 1999 Forwards Rev 8 to Nuclear Generating Stations Emergency Plan, for Plants.With Summary of Changes ML20210M9131999-08-0202 August 1999 Forwards Response to NRC AL 99-02, Operating Reactor Licensing Action Estimates, for Fys 2000 & 2001 for Comed ML20210K0771999-07-30030 July 1999 Submits 30-day Rept Re Discovery of ECCS Evaluation Model Error for Byron & Braidwood Stations,As Required by 10CFR50.46 ML20210J8951999-07-29029 July 1999 Submits Other Actions,As Described,To Be Taken for Valves to Resolve Potential Pressure Locking Concerns,In Light of Extended Period for Valve Bonnet Natural Depressurization,In Response to GL 95-07, Pressure Locking & Thermal.. ML20210E2151999-07-23023 July 1999 Forwards Byron Unit 1 B1R09 ISI Summary Rept Spring 1999 Outage,980309-990424, in Compliance with Requirements of Article IWA-6000, Records & Repts of Section XI of ASME & P&PV,1989 Edition ML20209H2991999-07-16016 July 1999 Withdraws 980529 LAR to Credit Automatic PORV Operation for Mitigation of Inadvertent Safety Injection at Power Accident.Response to NRC 990513 RAI Re LAR Encl ML20207H7501999-07-12012 July 1999 Forwards Revised Pressure Temp Limits Rept, for Byron Station,Units 1 & 2.Revised Pressurized Thermal Shock Evaluations,Surveillance Capsule Rept & Credibility Repts, Also Encl ML20209G1391999-07-0909 July 1999 Forwards Results of SG Tube Insps Performed During Byron Station,Unit 1,Cycle 9 Refueling Outage within 12 Months Following Completion of Insps ML20196J9061999-07-0101 July 1999 Provides Evidence That Util Maintains Guarantee of Payment of Deferred Premiums in Amount of $10 Million for Each of Thirteen Reactors,Per 10CFR140.21 ML20196J9131999-07-0101 July 1999 Submits Status of Nuclear Property Insurance Currently Maintained for Braidwood,Byron,Dresden,Lasalle County,Quad Cities & Zion Nuclear Power Stations,Per 10CFR50.54(w)(3) ML20209B8241999-06-30030 June 1999 Forwards Five 3.5 Inch Computer Diskettes Containing Revised Annual Dose Repts for 1994 Through 1998 for Individuals Receiving Neutron Dose Not Previously Included in Reported Total Effective Dose Equivalent Values.Without Diskettes ML20196G2161999-06-25025 June 1999 Forwards for NRC Region III Emergency Preparedness Inspector,Two Copies of Comed Emergency Preparedness Exercise Manual for 1999 Byron Station Annual Exercise. Exercise Is Scheduled for 990825.Without Encls ML20209D4861999-06-17017 June 1999 Informs That R Heinen,License OP-30953-1 & a Snow,License SOP-30212-3,no Longer Require License at Byron Station 05000454/LER-1999-002, Forwards LER 99-002-00,IAW 10CFR50.73(a)(2)(i)(b).There Are Two Actions Remaining to Address Cause of Event.Both Actions Are Listed1999-06-0808 June 1999 Forwards LER 99-002-00,IAW 10CFR50.73(a)(2)(i)(b).There Are Two Actions Remaining to Address Cause of Event.Both Actions Are Listed ML20195D6351999-06-0404 June 1999 Notifies NRC of Actions That Has Been Taken in Accordance with 10CFR26, Fitness for Duty Programs ML20211M1611999-05-28028 May 1999 Discusses 990527 Meeting with Comed Re Safety Culture & Overtime Control at Byron Nuclear Plant from Videoconference Location at NRC Headquarters.Requests That Aggressive Actions Be Taken to Ensure That Comed Meets Expectations ML20207D5261999-05-26026 May 1999 Forwards Response to NRC 990318 RAI Concerning Alleged Chilling Effect at Byron Station.Attachment Contains Responses to NRC 12 Questions ML20211M1781999-05-25025 May 1999 Summarizes Concerns with Chilling Effect & Overtime Abuses at Commonwealth Edison,Byron Station.Request That Ltr Be Made Part of Permanent Record of 990527 Meeting ML20195C7911999-05-25025 May 1999 Forwards Revised COLR for Byron Unit 2,IAW 10CFR50.59.Rev Accounts for Planned Increase of Reactor Coolant Full Power Average Operating Temp from 581 F to 583 F 05000454/LER-1999-001, Forwards LER 99-001-00,IAW 10CFR50.73(a)(2)(i)(B).Required Actions to Address Causes of Event Listed1999-05-21021 May 1999 Forwards LER 99-001-00,IAW 10CFR50.73(a)(2)(i)(B).Required Actions to Address Causes of Event Listed ML20195B2301999-05-19019 May 1999 Requests Approval of Proposed Changes to QA Topical Rept CE-1-A,rev 66a.Attachment a Describes Changes,Reason for Change & Basis for Concluding That Revised QAP Incorporating Proposed Changes Continues to Satisfy 10CFR50AppB ML20207E9831999-05-18018 May 1999 Forwards Copy of Commonwealth Edison Co EP Exercise Evaluation Objectives for 1999 Byron Station Annual EP Exercise,Which Will Be Conducted on 990825.Without Encl ML20206N8551999-05-11011 May 1999 Forwards 1998 Annual Radioactive Environ Operating Rept for Byron Station. Rept Includes Summary of Radiological Liquid & Gaseous Effluents & Solid Waste Released from Site ML20206U3351999-04-30030 April 1999 Forwards Evaluation of Matter Described in Re Byron Station.Concludes That Use of Overtime at Byron Station Was Controlled IAW Administrative Requirements & Mgt Expectations Established to Meet Overtime Requirement of TS ML20206F5381999-04-30030 April 1999 Forwards Magnetic Tape Containing Annual Dose Repts for 1998 for Braidwood,Byron,Dresden,Lasalle County,Quad Cities & Zion Nuclear Power Stations,Per 10CFR20.2206(c).Without Magnetic Tape ML20206C7901999-04-23023 April 1999 Provides Suppl Info Re Use of W Dynamic Rod Worth Measurement Technique,As Requested During 990413 Telcon.Rev Bars in right-hand Margin Identify Changes from Info Submitted by ML20206E7521999-04-22022 April 1999 Submits Rept on Number of Tubes Plugged or Repaired During Inservice Insp Activities Conducted at Plant During Cycle 9 Refueling Outage,Per TS 5.6.9 ML20206A7431999-04-22022 April 1999 Forwards Comments Generated Based on Review of NRC Ltr Re Preliminary Accident Sequence Precursor Analysis for Byron Station,Unit 1 ML20206B3941999-04-21021 April 1999 Forwards Annual & 30-Day Rept of ECCS Evaluation Model Changes & Errors, for Byron & Braidwood Stations.Updated Info Re PCT for Limiting Small Break & Large Break LOCA Analysis Evaluations & Detailed Description of Errors ML20206B2471999-04-20020 April 1999 Informs That SE Kuczynski Has Been Transferred to Position No Longer Requiring SRO License.Cancel License SOP-31030-1, Effective 990412 ML20205S9621999-04-20020 April 1999 Responds to 981203 RAI Telcon Re SG Tube Rupture Analysis for Byron Station,Unit 2 & Braidwood Station,Unit 2.Addl Info & Subsequent Resolution of Issues Discussed During 990211 Telcon Are Documented in Encl ML20206A8141999-04-20020 April 1999 Advises NRC of Review of Cycle 10 Reload Under Provisions of 10CFR50.59 & to Transmit COLR for Upcoming Cycle ML20205T3901999-04-13013 April 1999 Forwards Byron Station 1998 Occupational Radiation Exposure Rept, Which Is Tabulation of Station,Utility & Other Personnel Receiving Annual Deep Dose Equivalent of Less than 100 Mrem ML20196K6661999-03-31031 March 1999 Forwards Byron Nuclear Power Station 10CFR50.59 Summary Rept, Consisting of Descriptions & SE Summaries of Changes, Tests & Experiments.Rept Includes Changes Made to Features Fire Protection Program,Not Previously Presented to NRC ML20205K5841999-03-31031 March 1999 Submits Rept on Status of Decommissioning Funding for Reactors Owned by Comm Ed.Attachment 1 Contains Amount of Decommissioning Funds Estimated to Be Required Pursuant to 10CFR50.75(b) & (C) ML20205B4241999-03-23023 March 1999 Provides Results of drive-in Drill Conducted on 990208,as Well as Augmentation Phone Drills Conducted Since 981015,as Committed to in Util ML20207K0351999-03-0404 March 1999 Forwards Util Which Transmitted Corrected Pages to SG Replacement Outage Startup Rept.Subject Ltr Was Inadvertently Not Sent to NRC Dcd,As Required by 10CFR50.4 ML20205C6861999-03-0404 March 1999 Provides Notification That Byron Station Implemented ITS on 990205 & Braidwood Station Implemented ITS on 990219 ML20207D6831999-03-0101 March 1999 Forwards fitness-for-duty Program Performance Data for Each Comed Nuclear Power Station & Corporate Support Employees for Six Month Period Ending 981231,per 10CFR26.71(d) ML20207D4301999-02-26026 February 1999 Informs NRC That Supplemental Info for Byron & Braidwood Stations Will Be Delayed.All Mod Work Described in Ltr Is on Schedule,Per GL 96-06 ML20207B8971999-02-25025 February 1999 Expresses Concern That Low Staffing Levels & Excessive Staff Overtime May Present Serious Safety Hazard at Some Commercial Nuclear Plants in Us ML20203C7001999-02-0202 February 1999 Informs That Mhb Technical Associates No Longer Wishes to Receive Us Region III Docket Info Re Comed Nuclear Facilities.Please Remove Following Listing from Service List ML20202F5911999-01-29029 January 1999 Forwards Byron Unit 1 Cycle 9 COLR in ITS Format & W(Z) Function & Byron Unit 2 Cycle 8 COLR in ITS Format & W(Z) Function. New COLR Format Has Addl Info Requirements ML20199E1611999-01-15015 January 1999 Forwards Response to 980902 RAI Re GL 97-01, Degradation of Crdm/Cedm Nozzle & Other Vessel Closure Head Penetrations. CE Endorses Industry Response to RAI as Submitted by NEI ML20199B7511999-01-0808 January 1999 Forwards Proprietary Versions of Epips,Including Rev 52 to Bzp 600-A1 & Rev 48 to Bzp 600-A4 & non-proprietary Version of Rev 52 to Bzp 600-A1 & Index.Proprietary Info Withheld 1999-09-30
[Table view] |
Text
r-Commonwealth Edison Company
.' Downers Grove,11. f41515-5701 April 22,1999 U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Washington, DC 20555 Byron Station, Units 1 and 2 Facility Operating License Nos. NPF-37 and NPF-66 NRC Docket Nos. STN 50-454 and STN 50-455
Subject:
Review Comments Regarding the Preliminary Accident Sequence Precursor Analysis for Byron Station, Unit 1
Reference:
NRC letter," Review of Preliminary Accident Sequence Precursor Analysis of Operational Condition at Byron Station, Unit 1," dated March 12,1999.
/
The reference letter provided the preliminary Accident Sequence Precursor (ASP) analysis of an operational condition that was discovered at Byron Station, Unit 1, on 4 September 12,1998. This condition was reported to the NRC in Licensee Event Report /Pd/
(LER) 50-454/98-018. The operational condition discussed in the LER was the trip of the 1 A Emergency Diesel Generator (EDG) on an engine low lube oil pressure signal during the first minute of a test run. In the reference letter, the NRC requested that the preliminary ASP analysis be reviewed and comments provided within 30 days of receipt of the letter (i.e., provide comments by April 21,1999). In a telephone conference between representatives of Commonwealth Edison (Comed) Company and the NRC, it was agreed that the comments could be submitted on April 22,1999. The review of the analysis has been completed and comments are attached. These comments were generated based on our review of the reference letter and information obtained during a telephone conference held on April 12,1999, between representatives of Comed, NRC, and Oak Ridge National Laboratory.
9904290013 990422 s PDR ADOCK 05000454*
P PDR
- ,O,f s3 U W A Unicom Company
.a April 22,1999 U. S. Nuclear Regulatory Commission Page 2 Should you have any questions concerning this letter, please contact Mr. J. A. Bauer at (630) 663-7287.
Respectfully,
/
R. M. Krich Vice President - Regulatory Services Attachment cc: Regional Administrator- NRC Region lli NRC Senior Resident inspector - Byron Station
Attachment Review Comments Regarding Preliminary Accident Sequence Precursor Analysis for Byron Station, Unit 1
r:
l l
We have reviewed the preliminary Accident Sequence Precursor (ASP) analysis of an operational condition that was discovered at Byron Station, Unit 1, on September 12, 1998. This condition was reported to the NRC in Licensee Event Report (LER) 50-454/98-018. The operational condition discussed in the LER was the trip of the 1 A Emergency Diesel Generator (EDG) on an engine low lube oil pressure signal during the first minute of a test run. The results of this review are as follows.
Event Description
. The " Event Description" section contained in the ASP analysis document is accurate. The ASP documentation appropriately characterized the sequence of events and the failure mechanism that was provided in LER 50-454/98-018.
Additional Event-Related Information
. The " Additional Event-Related Information" section contained in the ASP analysis document is accurate with respect to the configuration of the plant, the design of the Emergency Diesel Generators (EDGs) at Byron Station, and the continued ,
availability of the 1B EDG. l I
Modelina Assumptions
. In the "Modeling Assumptions" section of the ASP analysis document, the assumption that the 1 A EDG was unavailable for 18 days is overly conservative.
There is reasonable assurance that the 1 A EDG became unavailable on l September 3,1998, and was therefore, unavailable for 11 days instead of 18 days. LER 50-454/98-018 did indicate that although the actual failure point could not be determined, the EDG was considered unavailable for 11 days from September 3,1998, until September 14,1998. The basis 'or this consideration is that plant operators identified a lifting relief valve on the u EDG on September 3,1998. Prior to SeptemL9r 3,1998, there was no indication of this lifting relief i valve. Although the initial operability deterraination that was performed after identification of the lifting relief valve did not consider the potential for a plugged
)
lube oil strainer, there is a reasonable belief that the condition did not exist prior ;
to September 3,1998, since the lifting relief valve would have t'een noted by plant operators on daily rounds or other plant personnel during the routine course of activities.
I e in the ASP analysis document, it appears that the assumptions overly compensate for the potential for a common mode failure of the remaining EDGs. :
There is no indication that the remaining three EDGs were ever impacted by the )
particular event documented in LER 50-454/98-018. The Byron Station l
}
Technical Specifications required plant operators to immediately perform an l' assessment of the common mode failure potential for the 1B EDG In addition, temporary modifications were installed on all four of the EDGs following this event to allow plant operators to monitor the EDG lube oil strainer differential j l
l
e,
- e pressures to ensure that the condition was not common to more than the one generator. No evidence to date has been identified which supports the common mode failure assumptions contained in the ASP analysis document. This conclusion is supported by the fact that maintenance is not performed on multiple EDGs at one time and there is no single dedicated crew that is responsible for performing maintenance on all the EDGs. Lack of attention to detail by maintenance personnel is one of the significant contributors identified in the root cause analysis for this event. Therefore, given the objective evidence, including inspection activity during the condition, there is little reason to believe that the identified condition had significant common cause potential. Our preliminary calculations indicate that a re-characterization of the failed condition of the 1 A EDG as a non-common cause potential failuro results in a net increase in Core Damage Probability of less than 1.0E-6.
- The design basis for the Byron Station is such that any single EDG is capable of providing sufficient AC power
- provide the capability to safely shutdown both units in the event of a Station Blackout (SBO). This design basis is documented in Byron /Braidwood Updated Final Safety Analysis Report (UFSAR) section 8.3.1.1.2.2, " Emergency Onsite Power Sources (Diesel Generators). Credit does I not appear to be given to this design basis in the "Modeling Assumptions" section
, of the ASP analysis document. We would suggest that such credit is
! appropriately taken by multiplying each " MULTI-UNIT LOOP" cutset associated with a SBO sequence, none of which contain a common-cause EDG failure term, l by the value represented by basic event "EPS-XHE-XM-OU."
l l '. It appears that a value of 0.8 was used as the failure probability for offsite power
! recovery for all sequences. This value, in most cases, is overly conservative.
[ Furthermore, this value appears to be used in all sequences, regardless of the
! expected accident progresr. ion time to core damage.
For the Byron Station Updated Probabilistic Safety Assessment (PSA), there were essentially three different post-SBO scenarios postulated. The first post-SBO scenario, which best correlates to Sequence 18-2 in the ASP analysis document, has a successful diesel-driven Auxiliary Feedwater (AFW) pump combined with a Reactor Coolant Pump (RCP) Seal Loss of Coolant Accident (SEALLOCA) probability that results in the core being uncovered at eight hours.
The eight hour period is based on a reasonable assumption that battery depletion occurs 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> into the event and results in AFW failure. However, there is sufficient secondary invantory in the steam generators and primary inventory in the RCS to provide an additional four hours prior to core damage when considering the reduction in decay heat that has occurred in the first four hours following the initiating event. Thermal hydraulic analysis performed for the Byron Station Individual Plant Examination (IPE) has demonstrated the core will remain covered for at least two hours with this primary and secondary inventory available immediately following such an initiating event. In the analysis, decay heat was initially assumed to be at its maximum value and was reduced exponentially as a function of time. Therefore, use of ar AC powe. non-recovery
l i ,
l l probability corresponding to an eight hour period would be more appropriate for l this sequence.
4 The second post-SBO scenario in the Byron Station Updated PSA, which best correlates to Sequence 18-9 in the ASP analysis document, includes the same plant conditions discussed in the first scenario, except that the core does uncover (i.e. the SEALLOCA is sufficiently large) in less than eight hours, such that recovery of AC power at eight hours is of no value for avoiding core damage.
Sequence 18-9 does credit such recovery. But with a 0.8 AC power non- I recovery probability, there appears to be a presumption that very little time is available prior to core damage following the RCP seal failure. Given our offsite AC power non-recovery probability versus time after Loss of Offsite Power (LOOP)/ Dual Unit Loss of Offsite Power (DLOOP) events curve, the AC power non-recovery probability of 0.8 appears to be reasonable for this sequence.
The third post-SBO scenario in the Byron Station Updated PSA, which best correlates to Sequence 18-22 in the ASP analysis document, postulates the failure of the diesel-driven AFW pump. As demonstrated in the thermal hydraulic analysis performed for the Byron Station IPE, AC power recovery must occur within two hours in order to avoid core damage. Although there is a potential for a large enough SEALLOCA to uncover the core in less than two hours, rendering the recovery of AC power meaningless, accounting for this will have a second or ,
third order effect on overall Core Damage Frequency, as this is already in a low !
probability sequence. Therefore, use of an AC power non-recovery probability I corresponding to a two hour period would be more appropriate for this sequence.
In addition, the ASP analysis document event tree included Sequence 18-20.
This sequence postulates the cycling of a pressurizer Power Operated Relief Valve (PORV), presumably due to ar expected reactor coolant system pressure transient following the initial turbine trip and loss of the condenser and the steam dump valves. The scenario continues with the PORV failing to re-close, resulting in an effective small break Loss of Coolant Accident (LOCA). Again, a 0.8 AC power noa-recovery probability was assigned. Thermal hydraulic analyses from the Byron Station IPE indicate that such a scenario (i.e., the largest small break 1 LOCA) would progress for slightly more than two hours prior to core damage occurring. Therefore, use of an AC power non-recovery probability corresponding to a two hour period would be more appropriate for this sequence.
Given the previous discussion of Sequences 18-2,18-9,18-20, and 18-22, use of AC power non-recovery probability values that correlate to time durations of 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> or 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, respectively, after the LOOP /DLOOP event would be more appropriate for the sequences where the time to core damage is 2 hours2.314815e-5 days <br />5.555556e-4 hours <br />3.306878e-6 weeks <br />7.61e-7 months <br /> or 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br />, respectively. The AC power non-recovery probability values in the Byron Station Updated PSA database for these time durations are 0.316 and 0.032, respectively.
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- These AC power non-recovery probability values were derived from Electric Power Research Institute (EPRI) Report TR-106306, " Losses of Off-Site Power at U. S. Nuclear Power Plants - Through 1995," dated April 1996. This study covered approximately the same time period as NUREG/CR-5496, " Evaluation of Loss of Offsite Power Events at Nuclear Power Plants: 1980 - 1996," dated November 1998, which is referenced in the ASP analysis document. In addition, EPRI Report TR-106306 covered more industry events than NUREG/CR-5496 and was in a final published form, whereas NUREG/CR-5496 was only in draft form at the time we performed our AC power non-recovery probability calculations.
The determination of the AC power non-recovery probability values was accomplished via a thorough review of EPRI Repott TR-106306 and of the LOOP /DLOOP events in its database. Certain events that clearly did not apply were excluded. Primary examples of excluded events pertain to those caused by hurricanes and salt spray. Hurricanes were only partially excluded to give some representation of the recent Davis Besse tomado event. In addition, any single unit LOOP at a multi-unit site which was terminated by simply cross-connecting to another unit's power supply was also excluded, in order to obtain a more accurate picture of offsite AC power recovery. The remairiing events were re- f plotted on a chart and curve fit. The two hour duration value was determined from the curve fit. For the eight hour duration value, a value from the curve fit was interpolated to avoid non-conservative predictions by the curve fit equation in the region of curve corresponding to eight hours. The resulting AC power non-recovery probability values are considered reasonable and reflective of actual industry experience, as applied to Byron Station.
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