ML13319A823
| ML13319A823 | |
| Person / Time | |
|---|---|
| Site: | San Onofre  |
| Issue date: | 06/07/1991 |
| From: | Nandy F SOUTHERN CALIFORNIA EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9106100331 | |
| Download: ML13319A823 (10) | |
Text
Southern California Edison Company 23 PARKER STREET IRVINE, CALIFORNIA 92718 F. R. NANDY TELEPHONE MANAGER. NUCLEAR LICENSING 714) 454-4504 U. S. Nuclear Regulatory Commission Attention:
Document Control Desk Washington, D. C. 20555 Gentlemen:
Subject:
Docket No. 50-206 Plant History Input for FTOL San Onofre Nuclear Generating Station, Unit 1 This letter provides historical information on San Onofre Unit 1. The information was requested by the NRC Project Manager, Mr. G. Kalman, as input for the San Onofre Unit 1 Full Term Operating License. In response to this request, we have provided the enclosed descriptions of San Onofre Unit 1 spent fuel accumulation and capacity, significant modifications, significant events, and operating history and outages.
If you have additional questions, please do not hesitate to contact me.
Very truly yours, Enclosure cc:
George Kalman, NRC Senior Project Manager, San Onofre Unit 1 J. 0. Bradfute, NRC Project Manager, San Onofre Unit 1 J. B. Martin, Regional Administrator, NRC Region V C. W. Caldwell, NRC Senior Resident Inspector, San Onofre Units 1, 2&3 910610C0331 910607 FR ADOCK 05000206 P
FDR
ENCLOSURE SAN ONOFRE UNIT 1 PLANT HISTORY Provided below are descriptions of various aspects of the San Onofre Unit 1 plant history. The descriptions cover spent fuel accumulation and capacity, significant modifications, significant events, and operating history and outages. The full period of commercial operation, from 1968 to the present, was considered in developing the descriptions. As used below, the term "significant" denotes those events or conditions that substantially affected plant availability or expenditures, or were of safety or regulatory interest.
Spent Fuel Accumulation and Capacity As of the completion of the Cycle 11 refueling outage, a total of 508 spent fuel assemblies have been removed from the San Onofre Unit 1 reactor. Of these, 270 have been shipped to the GE reprocessing facility in Morris, Illinois, 70 have been placed in the Unit 2 spent fuel pool, 69 have been placed in the Unit 3 spent fuel pool, and 99 are located in the Unit 1 spent fuel pool.
The shipment of assemblies to Morris, Illinois occurred during the period from 1972 to 1980.
The Unit 1 spent fuel pool has the capacity to store 216 spent fuel assemblies.
This capacity has remained unchanged since the plant was built. The Unit 1 spent fuel pool currently has the capacity for an additional 117 fuel assemblies. Without the transhipment of Unit 1 assemblies to the Unit 2 and 3 spent fuel pools during 1988-1989, the Unit 1 spent fuel pool would have been unable to accommodate the full core off-load required during the 1990-1991 refueling outage. Upon completion of re-racking of the Unit 2 and 3 spent fuel pools, there will be sufficient capacity to permit operation of all three units until approximately 2004. As this date approaches, SCE will evaluate other options for the disposition of spent fuel, such as rod consolidation, additional on-site storage space, or shipment to a D.O.E. approved facility.
Significant Modifications San Onofre Unit 1 was designed and built during the early to mid 1960s.
Recognizing the refinements in nuclear related design criteria, the NRC has required SCE to modify San Onofre Unit 1 to meet revised criteria in specific areas. Some of the more significant modifications were; the Sphere Enclosure Project (a concrete shield building erected around the existing containment sphere), and the Standby Power Addition (an installation of redundant standby diesel generators capable of powering the emergency core cooling systems (ECCS)).
Both of these modifications were performed during a 1976-1977 outage.
In 1977 the NRC initiated the Systematic Evaluation Program (SEP) to review the design of selected older nuclear plants. A group of eleven older plants, including San Onofre Unit 1, were the subject of a design review using modified Standard Review Plan criteria. The SEP review has resulted in plant upgrades to bring San Onofre Unit 1 into closer compliance with current NRC criteria. Some of the more significant of these upgrades are as follows:
Seismic Modifications - Extensive seismic modifications were performed to enable structures and equipment to withstand a 0.67g earthquake. This resulted in significant increases in design forces in many areas. These modifications included the strengthening of component supports, installation of a new auxiliary feedwater storage tank, and strengthening of the protective sea wall.
Fire Protection Modifications - An extensive reanalysis was performed comparing the existing fire protection provisions with the requirements of 10CFR50, Appendix R. As a result of this reanalysis, modifications were performed to upgrade the San Onofre Unit 1 design to be consistent with current fire protection criteria. The modifications included installation of a Dedicated Shutdown Diesel to assure the ability to safely shut down the plant if vital power supplies were lost as the result of a fire. Fire barriers, detection systems, and suppression systems were also upgraded.
Environmental Qualification Modifications - Modifications were performed to replace equipment that could not be shown to meet current environmental qualification criteria. Numerous components were replaced including; elements of the control circuitry for the recirculation flow control valves, aging or unqualified electrical penetrations, terminal blocks inside containment, coaxial cabling to radiation and neutron monitoring instruments, and certain resistance temperature detectors, limit switches, valve actuators, solenoids, and pressure and flow transmitters.
In addition to the upgrades described above, San Onofre Unit 1 has been significantly modified in response to post-TMI requirements. The significant TMI modifications consist of the automation of the Auxiliary Feedwater System, the installation of a Post-Accident Sampling System, the installation of additional accident monitoring instrumentation, the installation of containment hydrogen recombiners, the installation of additional post-accident shielding, and the installation of emergency response facilities.
As the result of an ECCS Single Failure Analysis conducted in 1990, a number of plant modifications were performed during the 1990-1991 refueling outage. These modifications included; addition of a redundant means to trip the reactor coolant pumps, separation of power supplies to the loop B and C recirculation flow instruments, control circuit modifications to provide redundant letdown isolation capability, mechanical modifications to prevent runout and loss of NPSH for the charging, recirculation, and refueling water pumps, control circuit modifications to prevent spurious opening of recirculation pump discharge valves, modifications to control circuits and mechanical components to prevent gas binding of the charging pumps, modifications to the Safeguards Load Sequencing System (SLSS) logic to eliminate the potential for a unacceptable delay in initiation of ECCS flow, and modifications to improve separation in the SLSS circuitry.
Significant Events During the first 2-3 years of operation the Unit experienced a number of rod-drop occurrences. These rod-drops resulted from various causes which were corrected following the specific occurrences.
In 1980, San Onofre Unit 1 was shutdown to assess the cause of a 270 gallon-per day primary-to-secondary steam generator tube leak. Subsequent eddy current inspections and laboratory examinations of pulled tube specimens revealed an extensive pattern of caustic-induced intergranular attack where sludge had accumulated on the steam generator tube sheet. As a corrective action, 6508 of the 11,382 (i.e., 57%) total tubes in all three steam generators were sleeved on the hot leg side in the vicinity of the tube sheet. The sleeves create a supplemental pressure boundary in the degraded areas. The tube sleeves, combined with the previously installed plugs, and additional plugs installed during the sleeving outage, resulted in a primary system flow rate reduction of approximately 3.3% due to an assumed 15% effective flow blockage from the plugs and sleeves. Technical Specification operating limits were revised to recognize the effects on plant operation with this configuration. Additionally, the operational reactor coolant average temperature was lowered to reduce the rate of intergranular attack.
A severe water hammer event occurred following a plant trip on November 21, 1985. The cause was determined to be the failure of five feedwater system check valves. Examination of the check valves revealed that the nut holding the disc to the hinge arm had loosened allowing the disc to tilt relative to the hinge arm. This prevented the disc from seating properly. In some cases, the disc had become completely detached from the hinge arm. Either condition allowed steam from the steam generators to backflow into the feedwater piping. When auxiliary feedwater flow was initiated, condensation induced slug flow in the partially voided feedwater piping resulted in the water hammer. A failure analysis determined that the nuts had become loosened by repeated hard impacts with the stop during normal feed system operation. The impacting of the nut against the stop was attributed to: (a) the proximity of some upstream flow disturbance sources such as control valves and elbows, (b) the nut-stud design of the check valves, (c) reduced power, reduced flow operation, and (d) marginal valve design for the application.
The five failed check valves were replaced with check valves utilizing a single piece disc and hinge arm. This design prevents loosening or detachment of the two parts. Also, the flow characteristics of the new valves greatly reduces the frequency and magnitude of disc-to-stop impacts during normal operation.
Additional check valves of the new design were installed in new locations in the feedwater piping as close as practical to the steam generators. The additional check valves provide further assurance that a water hammer will not occur.
Finally, modifications were made to the main feedwater flow control valve circuitry and the feedwater piping slope to further reduce the possibility of water hammer.
00 In 1986 the NRC issued a Notice of Violation for; failure to maintain the auxiliary feedwater system operable, inadequate testing to assure the check valves were functional, and inadequate corrective action for noises heard in the feed system five months prior to the event. The NRC imposed a Civil Penalty of
$180,000 for these violations.
Operating History and Outages Southern California Edison (SCE) Company was issued Provisional Operating License No. DPR-13 for SONGS-1 on March 27, 1967 and San Onofre Unit 1 began commercial operation on January 1, 1968. From commercial operation through the end of 1990 there have been 158 outages. Of these, 79 were forced outages and 79 were scheduled outages. The San Onofre Unit 1 Capacity Factor through fuel cycle 10 operations was approximately 51%. This Capacity Factor was significantly affected by extended outages to perform plant modifications, some of which are discussed above. For the same period, the Production Factor, which excludes outage time allocated to modifications, was approximately 81%.
Significant outages are summarized in the following table:
SAN ONOFRE UNIT 1 SIGNIFICANT OUTAGE HISTORY FORCED OR CAUSE DATES SCHEDULED HOURS The unit was manually tripped 02/07/68 -
Forced 287 following observation of a fire in 02/19/68 a cable tray leading to a sphere electrical penetration.
The unit was removed from the line 03/04/68 -
Forced 6
as a result of a control rod sub-03/04/68 group slipping into the core during cycler checkout after routine maintenance of the cycler.
The unit was brought to hot 03/09/68 -
Forced 43 shutdown when it was determined 03/10/68 that control rod F-10 was in the core.
The unit was manually tripped due 03/12/68 -
Forced 4433 to a fire in the cable trays of 09/12/68 the No. 2 480V switchgear room.
The reactor was manually tripped 09/26/68 -
Forced 87 when the control rods in subgroup 09/30/68 8 dropped into the core.
1 SAN ONOFRE UNIT 1 SIGNIFICANT OUTAGE HISTORY FORCED OR CAUSE DATES SCHEDULED HOURS The unit was removed from service 06/21/69 -
Scheduled 1193 for an inspection of the turbine 08/09/69 and generator and steam generator modification.
The reactor was manually tripped 08/14/69 -
Forced 98 when the control rods associated 08/18/69 with subgroup 7 dropped into the core.
CYCLE 2 REFUELING OUTAGE, 10/02/70 -
Scheduled 1156 in-service inspection, maintenance 11/20/70 and relocation of the existing 220 kV and 138 kV switchyards.
The unit tripped due to loss of 06/22/71 -
Forced 6
Chino and Santiago 220 kV lines.
06/22/71 CYCLE 3 REFUELING OUTAGE, 12/25/71 -
Scheduled 1457 in-service inspection, maintenance 02/24/72 and containment vessel integrated leak rate testing.
The unit was removed from service 07/19/72 -
Scheduled 210 to repair primary to secondary 07/28/72 leakage and to perform miscellaneous maintenance work.
The unit was removed from service 10/13/72 -
Scheduled 152 to repair primary to secondary 10/20/72 leakage.
The unit was removed from service 01/06/73 -
Scheduled 108 to repair primary to secondary 01/10/73 leakage.
CYCLE 4 REFUELING OUTAGE, and 06/01/73 -
Scheduled 1248 maintenance.
07/24/73 The unit was removed from service 10/21/73 -
Forced 2244 due to salt water leakage to the 01/22/74 condenser and turbine vibration.
Investigation revealed turbine blade failure.
SAN ONOFRE UNIT 1 SIGNIFICANT OUTAGE HISTORY FORCED OR CAUSE DATES SCHEDULED HOURS The unit was removed from service 04/27/74 -
Scheduled 546 to accomplish reheater repairs and 05/20/74 miscellaneous maintenance.
The reactor manually tripped when 10/01/74 -
Forced 7
subgroup 8 control rods dropped.
10/22/74 CYCLE 5 REFUELING OUTAGE, and 03/14/75 -
Scheduled 950 reheater steam dump test.
04/23/75 The unit tripped from turbine 01/21/76 -
Forced 7
overspeed when the Santiago-San 01/21/76 Onofre 220 Kv transmission lines were lost due to a brush fire beneath them.
The unit was taken off line to 07/30/76 -
Forced 101 repair primary to secondary 08/03/76 leakage.
CYCLE 6 REFUELING OUTAGE, turbine 09/30/76 -
Scheduled 4633 maintenance and plant 04/11/77 modifications.
The reactor was manually tripped 05/18/77 -
Forced 14 when a failed relay in Shutdown 05/18/77 Group 2 circuitry allowed four control rods to drop into the core.
The reactor was manually tripped 06/09/77 -
Forced 10 when a relay failed in Shutdown 06/10/77 Group 1 and allowed four control rods to drop into the core.
The unit was removed from the line 09/09/77 -
Scheduled 646 to inspect reactor coolant pump 10/06/77 "C" motor bearings, repair the turbine control oil system, plug tube leaks in the reheaters, inspect the steam generators, and for tube plugging in the steam generators.
SAN ONOFRE UNIT 1 SIGNIFICANT OUTAGE HISTORY FORCED OR CAUSE DATES SCHEDULED HOURS The reactor tripped from a loss of 03/08/78 -
Forced 4
coolant flow signal.
The low flow 03/08/78 condition occurred when a fault on the San Diego Gas and Electric Company power grid, which is intertied with Southern California Edison Company at San Onofre, resulted in low voltage at the reactor coolant pump motors.
The unit was removed from service 04/05/78 -
Scheduled 472 for steam generator inspection.
04/25/78 CYCLE 7 REFUELING OUTAGE 09/15/78 -
Scheduled 1211 11/05/78 The unit was removed from the line 06/01/79 -
Scheduled 394 for maintenance activities 06/18/79 including steam generator tube plugging and eddy current examination, turbine stop valve overhaul, condenser tube plugging and eddy current examination, and steam generator feedwater nozzle NDE and repair.
The unit was brought off line to 01/26/80 -
Scheduled 372 complete TMI plant modifications.
02/10/80 CYCLE 8 REFUELING OUTAGE (Outage 04/09/80 -
Scheduled 10417 was extended for steam generator 06/17/81 sleeving)
The unit was removed from service 07/17/81 -
Forced 741 in accordance with technical 08/10/81 specifications following a fire in No. 1 diesel generator.
The unit was taken off line to 02/27/82 -
Scheduled 24107 complete modifications related to 11/27/84 TMI and fire protection (10CFR50, Appendix R).
The outage was extended for seismic modifications.
SAN ONOFRE UNIT 1 SIGNIFICANT OUTAGE HISTORY FORCED OR CAUSE DATES SCHEDULED HOURS The unit was manually tripped when 11/21/85 -
Forced 199 Aux. Transformer "C" relayed, 11/29/85 causing loss of power to Vital Bus No. 4. During the recovery, a severe water hammer occurred in the feedwater system.
CYCLE 9 REFUELING OUTAGE, 11/29/85 -
Scheduled 5743 including EQ, fire protection, and 07/26/86 seismic modifications.
Main feedwater pump lube oil 09/05/86 -
Forced 638 shaft failure.
10/01/86 MID-CYCLE 9 MAINTENANCE OUTAGE 05/09/87 -
Scheduled 1295 07/02/87 SECOND MID-CYCLE 9 MAINTENANCE 02/14/88 -
Scheduled 4167 OUTAGE 08/05/88 CYCLE 10 REFUELING OUTAGE, 11/28/88 -
Scheduled 4270 including Nuclear Instrument 05/25/89 System, Aux Feedwater System, ESF, Diesel Generator, and Steam/Feed flow mismatch modifications.
Repair erroneous steam generator 05/26/89 -
Forced 773 level indicators.
06/28/89 Manual trip due to shutdown bank 09/18/89 -
Forced 51 Group 2 rods dropping to the 09/20/89 bottom of the core.
EQ modifications to Hot Leg 11/01/89 -
Scheduled 487 Recirculation System.
11/21/89 CYCLE 11 REFUELING OUTAGE AND 06/30/90 -
Scheduled 6381 THERMAL SHIELD SUPPORT REPL.,
03/23/91 including ATWS, 480v system, Charging System, EQ, Component Cooling Water System, and refueling water level indication modifications.
The unit was shut down to repair 04/21/91 -
Forced 720 primary to secondary leakage.
05/21/91 0
SAN ONOFRE UNIT 1 SIGNIFICANT OUTAGE HISTORY FORCED OR CAUSE DATES SCHEDULED HOURS Manual trip due to two rods 05-28 Forced 39 dropping to the bottom of the 05-30-91 core.