Letter Sequence Approval |
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MONTHYEARML13324A4801984-11-0303 November 1984
Forwards Justification for Continued Operation of Equipment Requiring Environ Qualification,As Part of Efforts to Return Unit 1 to Svc
Project stage: Other
ML13324A4981984-11-19019 November 1984
Documents Results of 831220 Meeting W/Nrc in Bethesda,Md Re Environ Qualification of safety-related Electrical Equipment.Addl Info Re Environ Qualification Program Encl, Per 840509 Request
Project stage: Meeting
ML13324A4991984-11-19019 November 1984
Informs of Completion of Environ Qualification of Listed Electrical Equipment,Including Reactor Coolant Temp Detectors & Containment Hydrogen Monitors.Qualification Packages for Equipment Will Be Completed by 850331
Project stage: Other
ML13324A5631985-02-26026 February 1985
Submits Certification of Compliance Re Environ Qualification of Electrical Equipment Per 10CFR50.49.Environ Qualification of All Equipment Will Be Completed by 850331
Project stage: Other
ML13324A5711985-03-11011 March 1985
SER Supporting Environ Qualification of Electric Equipment Important to Safety,Per Requirements of 10CFR50.49
Project stage: Other
ML13324A5681985-03-11011 March 1985
Forwards SER Re Environ Qualification of Electric Equipment Important to Safety.Equipment Qualification Program in Compliance w/10CFR50.49.Final Environ Qualification of Electric Equipment Will Be Completed by 850331
Project stage: Approval
ML20235Z4081987-10-16016 October 1987
Summary of Operating Reactors Events Meeting 87-35 on 871013.List of Attendees,Events Discussed,Significant Elements of Events & Summary of Reactor Scrams & Comparison of Wk Statistics W/Industry Averages Encl
Project stage: Meeting
ML13319A7911987-10-16016 October 1987
Forwards Description of ESF Single Failure Analysis,Per NRC 860923 Request,Resulting from 860730 Failure of PT-59 Which Identified Single Failure Susceptibility of Reactor Protection Sys.Final Rept Will Be Submitted by 871106
Project stage: Other
ML13336A0441987-10-20020 October 1987
Summary of 871009 Meeting W/Util in Bethesda,Md Re Licensee Identified Possible Failure in ESF Equipment.List of Attendees & Slides Used by Licensee Encl
Project stage: Meeting
ML13333A5941987-12-0101 December 1987
Forwards Revised Better Estimate Analysis for Cases 5 & 6 to Support Justification for Continued Operation for Remainder of Cycle.Better Estimate Analysis for Core Response During Main Steam Line Break (Cases 5 & 6) Also Encl
Project stage: Other
ML13333A6031987-12-0202 December 1987
Forwards Safety Evaluation Accepting Util 871016 Single Failures Analysis for Esf,Per 871009 Meeting.Justification for Interim Plant Operation Acceptable Until 871214,pending Further Analysis
Project stage: Approval
ML13333A6081987-12-0202 December 1987
Safety Evaluation Re Single Electrical Failures Affecting safety-related Function of Esfs.Util 871016 Justification for Continued Plant Operation Acceptable Until 871214. Operation Beyond 871214 Must Be Supported by Addl Analyses
Project stage: Approval
ML13333A6001987-12-0808 December 1987
Provides Addl Info Re ESF Single Failure Analysis,Including Discussion of Method Used to Determine Min Acceptable DNBR Applicable for Macbeth Correlation at Sys Pressures Established by Analysis,Per 871204 Request.Graph Also Encl
Project stage: Other
ML13333A6141987-12-0909 December 1987
Forwards Proprietary ESF Single Failure Analysis Re Min Value of Dnbr.Proprietary Calculation of DNBR & Supporting Affidavit Withheld (Ref 10CFR2.790)
Project stage: Other
ML13333A6321987-12-11011 December 1987
Safety Evaluation Supporting Util Justification for Interim Plant Operation Re ESF Single Failure Vulnerability
Project stage: Approval
ML13333A6271987-12-11011 December 1987
Forwards Safety Evaluation Re Util 871016 Submittal of ESFs Single Failure Analyses & 871201,08 & 09 Submittals of Analyses Justifying Operation of Plant for Remainder of Current Operating Cycle.Justification Acceptable
Project stage: Approval
ML13331B0101988-02-19019 February 1988
Forwards Fee for 871016 Application for Review of Justification for ESFs Single Failure Analysis,Per 880127 Request
Project stage: Request
ML13316B8971988-02-26026 February 1988
Summary of 880225 Mid Level Mgt Meeting W/Util Re Status of Licensee Root Cause Evaluation of Environ Qualification Problem W/Unit 1,control of Boron Concentration & Focus of NRC Programs Toward Insp of Utils in Future
Project stage: Meeting
ML13330B2671988-03-11011 March 1988
Informs of Action Planned to Correct Deficiencies in Environ Qualification Program.Work Being Performed Will Result in Equipment Being Qualified for Postulated Harsh Environ Before Restart from Current Maint Outage
Project stage: Other
ML13330B2801988-03-22022 March 1988
Notification of 880324 Meeting W/Licensee in Region V Ofc to Discuss Environ Qualification Concerns & Corrective Actions to Be Taken by Licensee Before Startup
Project stage: Meeting
ML13330B2751988-03-22022 March 1988
Confirms 880316 & 18 Telcons Between Ph Johnson & Ma Wharton Re 880324 Mgt Meeting in Region V Ofc to Discuss Facility Environ Qualification Deficiencies & Planned Corrective Actions Before Resuming Operation.Meeting Notice Encl
Project stage: Meeting
ML13330B2851988-03-30030 March 1988
Submits Info Re Environ Qualification of Electrical Equipment.Concludes That Risk Associated W/Any 10CFR50.49(b)(2) Equipment That Might Exists Considered Low & Discrepancies Identified Will Be Promptly Dispositioned
Project stage: Other
05000206/LER-1988-001-02, :on 880225,several Components Requiring Environ Qualification Found Omitted from Equipment Qualification Master List.Caused by Inadequate Methodology During List Generation.Installed Equipment Reviewed1988-03-30030 March 1988
- on 880225,several Components Requiring Environ Qualification Found Omitted from Equipment Qualification Master List.Caused by Inadequate Methodology During List Generation.Installed Equipment Reviewed
Project stage: Other
ML13330B2891988-04-0101 April 1988
Describes Util Compliance w/10CFR50.49.Util Believed All safety-related Equipment Was Included on Environ Qualification Master List (Eqml) & Fully Qualified After Returning to Svc from Cycle 9 Refueling Outage.Eqml Encl
Project stage: Other
ML13330B2981988-04-26026 April 1988
Discusses Plant Comprehensive Program Addressing 10CFR50.49(b)(2) Equipment Environ Qualification.Util Decided to Perform Program on Accelerated Schedule Prior to Unit Restart
Project stage: Other
ML13330B3091988-05-11011 May 1988
Confirms 880509 Telcon Re Environ Qualification (Eq). Licensee Made Commitment to Provide Ltr Describing Recent EQ Review Effort,Including Description of Program,Review Methods,Findings & Corrective Actions,By 880520
Project stage: Other
ML13330B3151988-05-27027 May 1988
Forwards Info to Resolve Discrepancies Identified During Review of Environ Qualification Master List,Including Results of Review of 10CFR50.49b(1) & (2) Equipment.Cables, Including Cables Traversed in Harsh Environs Also Reviewed
Project stage: Other
ML13316B9161988-06-10010 June 1988
Notice of Violation & Proposed Imposition of Civil Penalty in Amount of $150,000.Noncompliance Noted:Listed Electric Components,Required to Be Qualified Per 10CFR50.49(b) Not Included in Master List of Qualified Equipment
Project stage: Other
ML13330B3431988-06-16016 June 1988
Responds to 880527 near-final Results of Environ Qualification of Electrical Equipment Review.Subj to Successful Completion of Cable walk-downs & Actions Described in Ltr,Returning to Svc Acceptable
Project stage: Other
ML13330B3481988-07-0909 July 1988
Forwards Update of Progress Made Re Environ Qualification Program at Facility.List of 10CFR50.49 b(1) Equipment & Corrective Actions Encl
Project stage: Other
ML13316B9201988-07-11011 July 1988
Responds to NRC Re Violations Noted in Insp Rept 50-206/88-10 & Proposed Imposition of Civil Penalty. Corrective Actions:Task Force Established to Ensure Responsibility for Engineering & Technical Work.Fee Paid
Project stage: Other
ML13331B0581988-07-19019 July 1988
Advises That Calculation CAW-87-130 Will Be Withheld from Public Disclosure Per 10CFR2.790(b)(5) & Section 103(b) of Atomic Energy Act of 1954,per 871209 Request
Project stage: Other
ML13336A0991988-07-27027 July 1988
Confirms Discussions on Closeout of Event 10237 Re Newly Discovered ESF Single Failure Vulnerability Reported on 871007.Final Review of Longer Term Corrective Action Being Conducted Under Tac 66624
Project stage: Approval
ML13330B3661988-07-29029 July 1988
Advises That NRC Reviewed Util Two Justifications for Operation & Agrees W/Determination of Operability,Per Generic Ltr 88-07,per Updating Results of re-review of Environ Qualification of Electrical Equipment
Project stage: Approval
ML13316A0231988-08-0101 August 1988
Ack Receipt of & Payment of Civil Penalty in Amount of $150,000
Project stage: Other
1988-03-11
[Table View] |
Text
0-ttREG&4 0C UNITED STATES NUCLEAR REGULATORY COMMISSION 00
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WASHINGTON, D. C. 20555 ENCLOSURE 1 SAFETY EVALUATION BY THE OFFICE OF NUCLEAR REACTOR REGULATION RELATING TO JUSTIFICATION FOR INTERIM PLANT OPERATION REGARDING ESF SINGLE FAILURE VULNERABILITY SOUTHERN CALIFORNIA EDISON COMPANY SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 1 DOCKET NO. 50-206
1.0 INTRODUCTION
On October 16, 1987, the licensee submitted an ESF single failure analysis for the staff to review. The submittal included a description of the scenarios for which a single failure of an ESF function would result in consequences not bounded by the analyses of record. Each scenario includes a specific justification for continued operation which referenced a better estimated analysis case and additional operator actions. In these analyses, credit was taken for realistic plant behavior and existing conditions of Moderator Temperature Coefficient (MTC). The MTC used in the analysis was applicable for core burn-up until December 14, 1987. The submittal also provide a description of the operator actions which have been identified to correct equipment misoperations resulting from the postulated single failure.
Based on our review of the above stated licensee's submittal, the staff issued an SER which concluded that the licensee's justification for continual plant operation, until modifications to the affected systems are implemented during the upcoming refueling outage, is acceptable. However, since the better estimated analyses were performed with an MTC which is be valid only to December 14, 1987, additional analyses were required for staff evaluation and approval in order to justify continuous plant operation after December 14, 1987.
8712160264 871211 PDR ADOCK 05000206 P
PDR
-2 On December 1 and 8, 1987, the licensee submitted the updated main steam line break analysis using End of Life (EOL) MTC curve to support its justification of interim plant operation until the forthcoming refueling outage.
2.0 EVALUATION On December 1, 1987, the licensee submitted the results of an updated better estimated main steam line break analysis. MTC curve applicable to EOL was used in this analysis. In response to the staff request, the licensee in its letter dated December 8, 1987, provided additional information to support its better estimated analysis which demonstrated that the results of a postulated main steam line break accident at EOL meet the acceptance criteria of the event.
The licensee identified the better estimated assumptions which differ from the design basis San Onofre Unit 1 main/steam line break as follows:
- 1. Credit was taken for charging pump flow to deliver borated water to the Reactor Coolant System (RCS). The safety injection sequences realigns a charging pump to provide flow to the RCS from the refueling water storage tank (RWST).
- 2. The end of life shutdown margin value assuming all control rods in was used.
- 3. The Reactor Coolant Pumps (RCPs) were assumed to trip, consistent with actual plant behavior. The RCPs would trip on turbine/generator trip. Also, the RCPs get a trip signal from the safety injection sequences.
- 4. The addition of thick metal heat to RCS was assumed during system cooldown.
-3 The licensee stated that the resulting RCS cooldown for this transient was outside the applicability range of the W-3 DNB correlation. Therefore, the Machbeth DNB correlation was used in this main steam line break analysis. The Machbeth correlation generated a limit on DNBR of 1.37 at low RCS pressure conditions for San Onofre Unit 1. The Machbeth DNB correlation has been used in main steam line break analysis for other PWR plants. The staff considers the use of this DNB correlation in a better estimated analysis for San Onofre Unit 1 acceptable.
The limiting main steam line break analyzed is a double ended rupture of a steam line outside containment. This would cause all three steam generators to blowdown and rapidly cool the RCS. This rapid RCS cooldown would result in a safety injection signal (SIS). A main feedwater isolation valve is assumed to fail to close upon receipt of the SIS and the result is the diversion of the SI flow to the steam generators instead of feeding RCS. The redundant main feedwater isolation valves are assumed to fail to open due to the adverse conditions from the steam line break in the vicinity of the valves. The SI flow to the steam generators enhances the RCS cooldown. Upon receipt of the SIS, the charging pump realigns to the RWST and delivers borated water to the RCS. The rapid cooldown of the RCS causes reactivity insertion due to the MTC and doppler temperature parameters. The reactivity insertion eventually causes a return to power. Ten minutes after transient initiation, the operator actions terminate the SI flow to the steam generators. The reactivity is eventually turned around due to doppler power feedback and the boron injected into the RCS from the charging pump. Peak power of approximately 6%
of rated power is reached at about 680 seconds. DNBR remains above the limit of 1.37 during the entire transient.
The licensee also evaluated the previously identified single failure scenarios resulting in less severe cooldown transients which may have higher terminal pressures. The evaluation confirmed that these cases are bounded by the previous San Onofre Unit 1 analysis regarding pressurized thermal shock (PTS).
-4
3.0 CONCLUSION
The acceptance criteria for a postulated main steam line break accident permit some fuel failure with radiological consequences not exceeding 10 CFR 100 limits. The results of the licensee's better estimated analysis show that there will be no DNB following a main steam line break accident. Therefore, sufficient safety margin exists in the plant design. The realistic assumptions used in the better estimated analysis are reasonable. Also, the procedures provided for operator to mitigate the postulated single failure scenarios have been reviewed and accepted. Therefore, we conclude that the licensee's justification for continued plant operation, until modifications to the affected systems are implemented during the upcoming refuel outage, is acceptable.
