ML13330B123
| ML13330B123 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 10/14/1986 |
| From: | Medford M Southern California Edison Co |
| To: | Lear G Office of Nuclear Reactor Regulation |
| References | |
| TAC-54376, TAC-63297, TAC-63298 NUDOCS 8610270447 | |
| Download: ML13330B123 (7) | |
Text
Southern California Edison Company P. 0.
BOX 800 2244 WALNUT GROVE AVENUE ROSEMEAD, CALIFORNIA 91770 M. O. MEDFORD TELEPHONE MANAGER OF NUCLEAR ENGINEERING (818) 302-1749 AND LICENSING October 14, 1986 Director, Office of Nuclear Reactor Regulation Attention: G. E. Lear, Director PWR Project Directorate No. 1 U. S. Nuclear Regulatory Commission Washington, D.C.
20555 Gentlemen:
Subject:
Docket No. 50-206 Third Edition of the Integrated Living Schedule San Onofre Nuclear Generating Station Unit 1
References:
A. Letter, Kenneth P. Baskin, SCE, to H. R. Denton, NRC, dated May 23, 1984 B. Letter, M. 0. Medford, SCE, to J. A. Zwolinski, NRC, dated August 29, 1985 C. Letter, M. 0. Medford, SCE, to G. E. Lear, NRC, dated March 26, 1986 D. Letter, M. 0. Medford, SCE, to A. E. Chaffee, NRC, dated April 8, 1986 Reference A submitted an application for amendment to establish an Integrated Living Schedule (ILS) for San Onofre Unit 1. The amendment provides for a license condition which will require SCE to follow the ILS Program Plan (the "Plan") which specifies that periodic updates of schedules be submitted to the NRC. Our last edition of the ILS was submitted by Reference B which was subsequently modified in accordance with the Plan and submitted by Reference C.
Enclosed and submitted is the third edition of the ILS. The enclosure includes a summary of the progress since the last submittal, identifies changes to the schedule including reasons for Schedule B changes, and estimates the percentage allocation of resources for regulatory and betterment projects for the next refueling/backfit outage. The next refueling/backfit outage for San Onofre Unit 1 is currently scheduled for the first quarter of 1988.
8610270447 661014 PQR ADOCK 05000206O P
G.E. Lear
-2 The ILS provided in the enclosure does not include provisions for the installation of measures to enhance the availability of the second source of offsite power by providing an immediately available supply. This modification has been discussed in various previous correspondence and meetings with the NRC and resulted from the SCE investigations into the water hammer event of November 21, 1985. It has now been determined that installation of this modification cannot be justified based on the minimal improvements in safety which it provides.
A conceptual design and cost estimate for this modification have been completed. The design includes the addition of a second auxiliary transformer which would remain in standby and would replace auxiliary transformer C by automatic fast transfer upon failure of the power supply circuit from the switchyard to the 4KV buses via auxiliary transformer C. In addition, the design requires that the switchyard line configuration be changed in order to allow for the additional supply circuit.
The modifications necessary to implement the new power source are very extensive. The cost estimate, based on conceptual engineering for these additions is approximately $14 million. Based on this high cost, the benefits of the modifications were reviewed to determine if the resulting improvement in safety and availability would justify the installation. A review of past transient events was conducted to see if the second source of offsite power would have improved system response or supported continued operation by preventing unit or reactor trips.
The primary source of the information was the Draft Integrated Plant Safety Assessment resulting from the Systematic Evaluation Program (NUREG-0829) for San Onofre Unit 1 which contains a summary review of operational events of safety importance in Appendix F. The information for the time period after 1981 was compiled from SCE Operating Reports.
With the exception of the water hammer event, none of the events involved problems with the power supply circuit from the switchyard to the 4KV buses via auxiliary transformer C. The additional circuit would have therefore had no impact on any of the transients. Based on this 19 year history, the proposed design modifications would have a very minor impact on the ability of the San Onofre Unit 1 systems to respond to transient events in general.
With respect to the the water hammer event where the new transformer circuit would have been beneficial, considering all of the corrective actions already taken (see reference D), the modifications would yield only minimal safety improvements over and above those already obtained. This conclusion is based on the following major items:
- 1. The major contributors to the water hammer event were the five failed check valves. The significant improvements made in the area of enhanced system capabilities to isolate the feedwater lines provides the most important improvement for preventing water hammer in the future.
- 2. The modifications provided to assure the operability of the LOVATS system will enhance the operator capabilities in restoring the delayed source of offsite power or in reestablishing power from the onsite diesels.
G.E. Lear
-3
- 3. The material improvements resulting from the Material Condition Review Program and the continued assurance of acceptable material condition resulting from the Area Monitoring program will minimize the likelihood that equipment degradation will lead to the type of failure which initiated the event.
- 4. Specific event related repairs to the failed cables were made and in addition, all equivalent cable was replaced.
- 5. The improvements in plant procedures will provide a more effective response to system conditions similar to those which occurred on November 21, 1985.
- 6. Finally, the improvements made to plant programs will prevent the development of the conditions which lead to the water hammer event. These improvements apply to historical trending as part of the maintenance and inservice testing programs as well as the review of plant conditions associated with the safety review process. In addition, specific improvements were made within each of these programs to upgrade the effectiveness of the programs.
The plant improvements described above provide a much greater impact on plant safety and reliability than the additional improvement which would result from the installation of the second immediately available source of offsite power. It should additionally be noted that the offsite power supply design of the plant in its present condition meets all of the regulatory requirements of the NRC in that acceptable plant system response can be demonstrated for transients and accidents when the safety related systems function as designed. The water hammer event of course exceeded the design basis due to the coincident failure of the five check valves in the feedwater system; however, the appropriate corrective action is to ensure the ability to isolate the feedwater system, not the installation of another source of offsite power.
If there are any questions or you would like further information, please let me know.
Very truly yours, Enclosure cc: Mr. 3. B. Martin, NRC Region V
Enclosure INTEGRATED LIVING SCHEDULE SAN ONOFRE NUCLEAR GENERATING STATION, UNIT 1 Third Edition October, 1986 Introduction Proposed License Condition 3.3, "Integrated Living Schedule of Backfits,"
requires SCE to follow the ILS Program Plan (the "Plan").
This Plan specifies that periodic schedule updates be submitted to the NRC along with specific information regarding progress in implementing NRC requirements, changes since the previous report, reasons for schedule changes and the expected percentage allocation of resources on regulatory vs. betterment projects. This document is the third edition of the ILS which provides that information.
Progress in Implementing NRC Requirements SCE's previous schedule included four major projects on Schedule A (projects required by rule, regulation or order) and seventeen projects on Schedule B (other regulatory related projects). All four of the Schedule A projects, Long Term Seismic Reevaluation Program, Modifications Associated with 10 CFR 50 Appendix R, Environmental Qualification and Post Accident Sample System, were completed during the refueling/backfit outage that started on November 21, 1985. Also completed during that outage were eight Schedule B projects.
These projects include:
o Containment Airlock Operating Mechanism o
Safety Grade Upgrade of AFWS Equipment o
Health Physics Facility Upgrade o
Improvements to Operational Radiation Monitoring System o
Main Feedwater Low Flow Instrumentation o
Radiological Effluent Technical Specification Modifications o
Replacement of Cable to RHR Pumps o
Reactor Coolant Pump Lift Rigs Additionally, a third train of auxiliary feedwater was installed as a manually operated system. It is scheduled to be modified to be automatic during the next refueling/backfit outage as indicated on the attached schedules.
Further progress was made in the area of Schedule B evaluations. At this time, evaluations have been concluded regarding the following:
o Wide Range Gas Monitor Plate Out o
Condensate Storage Tank Flooding Potential o
Automatic Trip of Reactor Coolant Pumps o
Inadequate Core Cooling Instrumentation o
Regulatory Guide 1.97 Comparisons o
Revisions of System Descriptions
-2 Additional modifications identified by the above studies include an upgrade of the core exit thermocouples for detection of inadequate core cooling. This commitment now becomes a project on Schedule B, attached.
Changes Since Last Edition In addition to the above projects being completed, SCE letter from M. 0.
Medford to G. E. Lear, NRC, dated March 26, 1986, deferred implementation of three projects. These are:
o Regulated Instrument Buses o
CVCS Valves MOV-LCV-1100B, C, D o
Waste Gas Decay Tank Monitoring Instrumentation The Regulated Instrument Buses modification is now scheduled for implementation in Cycle X. The other two projects are scheduled for completion during Cycle XI due to their relative low rank. These projects were deferred due to the extensive effort required during the outage to implement the other, higher priority projects. Compensatory measures remain in effect for each of these projects as indicated in the above letter.
Since the last edition of the ILS, we have committed to a number of regulatory related projects. These include the previously identified upgrade of the core exit thermocouples for inadequate core cooling, Control Room HVAC Duct Heaters, In-Service Testing Differential Pressure Indicators, Reactor Cavity Ladder Safety Cage (OSHA Requirement), Vital Bus 4 Uninterruptible Power Supply, Control Room and Technical Support Center HVAC Upgrades, Automatic Termination of Main Feedwater/Safety Injection Pumps on Low RWST Level and the Addition of Synchrocheck Relays to the Emergency Diesel Generators. All of these projects except the Reactor Cavity Ladder Safety Cage have been the subject of correspondence between SCE and the NRC. The Reactor Cavity Ladder Safety Cage is being implemented in order to meet the requirements of OSHA.
The schedules attached also reflect the deletion of the Safety Injection System Modifications. SCE had previously planned to install new feedwater pumps which would allow the existing pumps to be dedicated to the safety injection function. Several studies on these systems and the positive results of SIS surveillance testing have convinced us that these modifications are not cost beneficial.
SCE plans to submit a comprehensive report in November, 1986 providing this information to the NRC staff.
Expected Allocation of Resources for Upcoming Outage The refueling/backfit outage for Cycle X of plant operation is expected to have resources allocated approximately 80% to regulatory projects and 20% to betterment projects. This allocation reflects a balancing of resource allocation following the last refueling backfit outage which was approximately 90% regulatory work.
Updated Schedules Schedules for Cycles X and XI are attached.
GEH:7301F
INTEGRATED LIVING SCHEDULE SAN ONOFRE UNIT 1 CYCLE X Schedule A (Rule, Regulation or Order)
Anticipated Transients Without Scram Diverse Turbine Trip Schedule B (NRC Commitments and Other Requirements)
Third Train of Auxiliary Feedwater Regulated Instrument Buses Indicating Lights On-Site Toxic Gas Sources Modifications In-Service Testing Differential Pressure Indicators Magnacraft Relays Replacement Automatic Vent System for Boric Acid System Reactor Cavity Ladder Safety Cage (OSHA)
Control Room HVAC Duct Heaters Vital Bus 4 Uninteruptible Power Supply Schedule C (Betterment Projects)
Nuclear Instrumentation System Replacement Turbine Vibration Detection Instrumentation Masonilian Isolation Valve Upgrades Radiation Monitor SV-99 Upgrade Evaluations Safety Parameter Display System January 1, 1987 Control Room Design Review May 1, 1987
INTEGRATED LIVING SCHEDULE SAN ONOFRE UNIT 1 CYCLE XI Schedule A (Rule, Regulation or Order)
None Schedule B (NRC Commitments and Other Requirements)
Upgrade of Core Exit Thermocouples for Detection of Inadequate Core Cooling Control Room and Technical Support Center HVAC Upgrades CVCS Valves MOV-LCV-1100 8, C, D Controls Modifications Waste Gas Decay Tank Monitoring Instrumentation Steel Decking Under Turbine Building North Extension Undervoltage Relays for Protection from Degraded Grid Voltage Automatic Termination of Safety Injection Pumps on Low RWST Level Removal of Automatic Reactor Coolant Pump Trip on Safety Injection Addition of Syncrocheck Relays to Emergency Diesel Generators Schedule C (Betterment Projects)
Control Room Instrument Racks Replacement Evaluations None