IR 05000416/1990024
| ML20029B114 | |
| Person / Time | |
|---|---|
| Site: | Grand Gulf  |
| Issue date: | 02/19/1991 |
| From: | Hunt M, Shymlock M NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION II) |
| To: | |
| Shared Package | |
| ML20029B095 | List: |
| References | |
| 50-416-90-24, NUDOCS 9103050442 | |
| Download: ML20029B114 (31) | |
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[poQtog 'o NUCLEAR REGULATORY COMMISSION
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RtOlON 11 j
101 MARIETT A ST REE T, N.W.
ATL ANTA. GEOR0l A 30323
'44.... *,o Report flo.:
50-416/90-24 Licensee:
Entergy Operations, Inc.
Jackson, MS 39205 Docket No.:
50-416 License No.:
NPF-29 Facility Name:
Grand Gulf Inspection Conducted:
November 13-16, 26-30 and December 10-14, 1990 Inspector:
'7 6 A 6P/M2'
'ML
/9 Medmo<+ 9 /
M.D. Hunt (Team (Kader)
Date Signe F
Team Members-N. Merriweather C. Smith P. Fillion M. Miller NRC Consultants:
J. Arsenault A. Josefowicz H. Leuna Approved by: /bh ey;>vde2.>
42 k h m,I//
MrShymlock, Chi,ef Date Sign'ed Plant Systems Sec' tion Engineering Branch Division of Reactor Safety l
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9103050442 910219 PDR ADOCK 05000416 O
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EXECUTIVE SUMMARY
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A Nuclear Regulatory Commission (NRC) team conducted an electrical distribution system functional inspection (EDSFI) at Grand Gulf Nuclear Power Plant.
The inspection was performed by the staff and consultants of Ril November 13-16, 1990, November 26-30,_1990 and December 10-14, 1990, lhe objective of this inspection was to assess the performance capability of the Grand Gulf EDS by reviewing the design-parameters as they relate to onsite and offsite emergency power sources and support equipment relied on during and following design bases events.
To accomplish this, the team reviewed the design of electrical and mechanical systems and equipment affecting the EDS, examined installed EDS
_ equipment, reviewed test programs and procedures affecting the EDS.
Additionally, the performance of the licensee's engineering and technical support organizations and configuration control was examined by reviewing modification packages, root cause analysis, personnel training and organizational staffing.
As a result of the inspection, the team identified two violations (one cited
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and one non-cited).
Additionally, certain procedures in the operations and i -
maintenance areas were considered weak and need upgrading.
The cited viola-tion was the result of an inadequate engineering review of a modification which placed a fuse in series with each of the Division I and II,125 VOC battery to bus supply breakers resulting in lack of fuse and breaker coordination with branch circuits.
This could have caused a loss of a 125 VDC bus if a faulted conditicn occurred on a branch circuit.
The non-cited violation was the result of EDG control cabinets doors being lef t open and unattended.
The operating procedures for the valving control of the EDG fuel filters needed clarification.
The operating procedures for the 4.16kV circuit breakers did not indicate the proper storage position for spare breakers inside the swithgear cubicles.
The i
maintenance procedures for the 6.9 kV and 4.16 kV swithgear did not require periodic verification of the tightness of the bus bar connection bolts and-nuts.
The calibration procedures for voltage relays and Load Shedding and Sequencing (LSS) bistables did not require resetting to the desired values to avoid exceeding the Technical Specifications allowable limits.
The fuse control program identified only the fuse size and did not specify the types of fuses in use.
Furthermore, the fuse types were not listed in the controlled drawings and-procedures.
The items identified would not have prevented the EDS from performing its
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designed function.
However, improvements are recommended in the areas l
identified.
To maintain configuration _ control, the licensee is in the process of evaluating L
and replacing many of the original design voltage calculations, short circuit calculations and coordination studies.
Engineering control of nodifications
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L appeared to be effective with the exception of the cited violation. The team considered the engineering and technical support for the EDS equipment and the mechanical systems inspected to be a licensee strength.
The design engineers (NPE) are located at the plant site and are readily available to review any i
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changes to modification-packages ~ that are necessary, The staff was knowledgeable in their assigned fields and appeared devoted to doing their
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assignments properly.
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' It is the consensus of the team that the EDS at Grand Gulf will perform its intended function under normal and accident conditions as it is now designed
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l TABLE OF CONTENTS
'l PAGE EXECUTIVE SUMMARY......................................................
i 1.0 INTRODUCTION.....................................................
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2.0 ELECTRICAL SYSTEMS...............................................
3.0 ELECTRICAL SYSTEM DESIGN REVIEW..................................
3.1 Short-Circuit Calculations.................................
3.2 Voltage Calculations and the Degraded Grid Voltage Relay.......................................
3.3 4.16 kV and 480 V Electrical Loading......................
3.3.1 -Emergency Diesel Generator Loading (DIV I and 11)-.....
3.3.2 Emergency Diesel Generator loading (DIV 111)..........
3.4 Electrical Cable Sizing Calculation........................
3.5 Motor Specifications.......................................
3.6 Transformer Bil Rating and Voltage Protection..............
4.0 CLASS lE 125 VOLT DC AND 120 VOLT AC SYSTEMS.....................
4.1 125 VDC System.............................................
4.1.1 125 VDC Class lE Battery and Charger Sizing.........
4.1.2 Voltage Regulation and Cable Sizing.................
4.1.3 125 VDC'Switchgear Short Circuit Ratings............
4.2 120 VAC Class IE Urinterruptable Power Supply..............
4.2.1 120 VAC IE Inverter Modi fication....................
4.3 Conclusions...............................................
5.0 PROTECTION AND COORDINATION......................................
5.1 4.16 kV System Protect'on and Coordination.................
5.2
.480 V System Protection and Coordination...................
5.3 125 VDC IE Distribution System Protection and Coordination...............................................
5.4 120 VAC IE Distribution System Protection and C o o r d i n a t i o n.............................................., 10 6.0 MECHANI CAL SYSTEMS SUPPORTING EDS...............................
6.1 Di esel Generator Fuel Oil System..........................
6.1.1 Flame Arrestors.on Fuel Oil Storage Tank Vents.....
6.1.2 Fu el O i l S t ra i ne rs.................................
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6.1.3 L i ne-up of D;pl ex S trai ners........................
6.1.4 Fuel Oil St> rage and Day Tank Volumes and l
Level Setraints....................................
6.1.5 Fuel Storage and Trans fer System...................
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6.2 Heating, Ventila tion and Air Condi tioning Design..........
Calculations 6.3 Divi sion III Di esel Generator Cooling Wa ter...............
6.4 C o n c l u s i o n s...............................................
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7.0 EDS EQUIPMENT...................................................
7.1 Eq u i pme n t Wa l k d own s.......................................
7.2 Di esel Generator Control. Cabi ne ts.........................
7.3 Fu se Repl a cement Program..................................
14-7.4 Equipment-Installed Spare Swi tchgear......................
7.5 Equipment - Molded Case Circuit Breaker Testing...........
8.0 EQUIPMENT - MAINTENANCE, TESTING AND CAllBRATION................
9.0 E DS MO D I F I C AT I ON S...............................................
9.1 Tempora ry Sys tem Al tera ti ons..............................
9.2 Conclusions...............................................
10.0 ENGINEERING AND TECHNICAL SUPPORT...............................
10.1 O rg a n i z a t i on a nd Key S ta f f.................................
10.2. Root Cause Analysis and Corrective Actions................
10.3 Sel f-As sessmen t and Traini ng............................... - 20 10.4 Conclusions...............................................
11.0 GENERAL CONCLUSIONS.............................................
12.0 EXIT MEETING....................................................
Appendix A V i o l a t i o n s........................ >....................... A-1 Appendix B Acronyms and Abbreviations
..................................B-1-Appendix C-Persons Contacted.......................................... C-1
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INTRODUCTION Previous inspections of nuclear power plants by NRC teams, and various licensee event reports (LER) have identified conditions in the electrical distribution systems (EDS) at various operating plants that could compromise the design safety margins of the plants, These deficiencies are the result of unmonitored and uncontrolled load growth on safety related electrical buses, inadequate engineering modifications, faulted design calculations and inadequate testing of EDS equipment.
In addition, the NRC discovered deficiencies where the-actual configuration of the EDS equipment does not always adhere to the original design.
Consequently, the NRC initiated a special inspection program to evaluate the adequacy of the EDS at each operating plant to assess system capability to perform the intended safety function and to evaluate EDS configuration control, engineering and technical support capabilities.
The objective of this inspection was to assess the performance capability of the Grand Gul f EDS by-reviewing the design parameters as they relate to onsite and offsite emergency power sources and associated equipment relied on during and following design basis events to support the plants safety-related equipment.
Additionally, the performance of the licensee's engineering _and technical support and configuration control was examined.
The ED5 components reviewed included the emergency diesel generators, the of f site circuits from the 115 kV and 500 kV grids, distribution transformers, 416 VAC swithgear, 480 VAC motor control centers, 120 VAC and 125 VDC diftribution centers,125 VDC class lE batteries, and protective relays.
The review
'ncluded examination of short circuit analysis, breaker and fuse coordination, cirait loading calculations, drawings, procedures and test results for selected equipment and devices which are part of the plant EDS.
The team reviewed mechanical systems af fecting the EDS, including the EDG air start system, lube oil and jacket water cooling systems.
The fuel oil storage system as evaluated for operability as required by the technical specifications.
eerous walkdowns were performed to assess equipment configuration and ratings to verify and support the engineering design data examined.
NOTE:
For this inspection report and evaluation, the terms weakness and rtrenoth are defined as follows:
Weakness - those areas needing improvement to prevent the potential for violation of regulatory requirements.
Strength - those areas which exceed the normal standards and practices, 2.0 ELECTRICAL SYSTEMS The team reviewed the off site and on site EDS for the Grand Gulf facility as described in the FSAR.
This review included the 500 kV and 115 kV systems which supply off site power to the safety related 4.16 kV safety buses. The on site review included the EDGs, 480 V system, the 120 VAC and 125 VDC distribution system and related componets.
This review also includes a review of the licensee's engineering programs as related to the EDS.
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The team reviewed a sample of specific electrical design attributes at each AC
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and DC level of the EDS.
This included verifying the adequacy of plant load
- calculations for the evaluation of electrical loads needed for the safe shut-down of _the plant, overcurrent protection calculations for short-circuit and ground faults,-and the sizing and coordination of protective devices.
The team reviewed a number of design documents related to loads associated with the EDS.
The documents reviewed addressed design calculations for AC and DC-system loading.-- voltage regulation during normal and degraded conditions, diesel generators (EDGs)g sequencing of safety-related loads onto the emergency voltage regulation durin, degraded voltage relay setpoints, class IE battery selection, short-circuit and ground fault analysis, fault current system protection, protective device coordination, and the protection of the EDS from power surges._
The team also reviewed procedures and guidelines governing design calculations, design control and plant modifications.
The following sections contain the most significant observations of the team.
3.0 ELECTRICAL SYSTEM DESIGN REVIEW The team reviewed the overall station Engineered Safety features (ESF),
Class IE distribution systems.
The review included Division 1,11, and !!I of the 4,16 kV distribution systems; and the 480 V system, including the Load Centers (LC) and the Motor Control Centers (NCC).
3.1 SHORT-CIRCUIT CALCULATIONS The team reviewed the licensee's short-circuit calculations, and determined that they were performed in accordance with industry standards for the application of circuit breakers.
An adequate margin exists between the
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short-circuit ratings of the 34.5 kV, 4.16 kV and 480 V circuit breakers and the calculated short-circuit currents.
The licensee recently carried out the calculations with the aid of a computer program called A-FAULT.
The licensee is_ in the process of analyzing the various reports generated by A-FAULT, and preparing the summary of results and conclusions statements. These new short-
. circuit calculations will replace the original plant design calculations.
According to design control procedures, the licensee performed a verification and validation of A-FAULT.
The team noted that this verification and valida-tion effort omitted one of the subprograms of A-FAULT called the low-voltage calculation.-
The licensee agreed to perform a verification and validation of the low-voltage calculation which applies to circuit breakers in 480 V and
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120 V distribution-systems.
Due to margins that exist on the 480_V level and the fact -that A-FAULT results are consistent with the original plant design calculations, the adequacy of 480 V breaker ratings was not really questioned,
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but the verification and validation' of the A-FAULT low-voltage calculation
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subprogram should be accomplis _hed.
-The licensee is in the process of performing short-circuit calculations and coordination studies for the 120 V circui's.
Records of such studies (i.e.,
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t 120 V level) were not part of the original plant design documentation. There-
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- fore, the licensee -had recently begun to generate the necessary calculations and documentation to demonstrate that breaker and fuse ratings and coordination
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were proper.
Tnese studies will include 120 V vital AC distribution and safety-related 120 V power distribution circuits.
3.2 VOLTAGE CALCULATIONS AND THE DEGRADED GRID VOLTAGE REli(
Similar to the short-circuit calculations described in the previous section, the licensee, in the near future, will replace the original voltage calcula-tions with a new set cf calculations.
The team reviewed these new calculations which were done with the aid of a computer program called DAPPER.
In general, the voltage calculations employed methodologies consistent with good engineer-ing practice, with sufficient cases and scenarios to satisfy NRC requirements, and covered alignment to of fsite power and the diesel generator as power sources.
As compared to the original voltage calculations, the new calculations incorporate a more detailed model of the systen. Another difference in the two calculations is that the original modeled a two-unit plant, whereas the new calculations model a one-unit plant as Grand Gulf is built.
Due to these differences in modeling, the results of the two calculations could not be directly compared, although, they were qualitatively consistent.
The following agreements were reached be: ween the team and the licensee's engineers to resolve issues raised during ceview of the voltage calculations:
(a) The licensee agreed to compare the Brarch Technical Position PSB-1 voltage verification test (done during initial p' ant start-up) with the new DAPPER program results, and take any necessary actions based on this comparison, it will require running several new cases with DAPPER using input data from the start-up tests.
Of particular interest is the case where the safety-related loads are fed from the 115 kV source when the Port Gibson to South Vicksburg line is out of service.
A 115 kV transmission line runs basically north to south from South Vicksburg substation to Lorman Substation.
From the intermediate substation at Port Gibson near the Grand Gulf Plant, a short spur line runs into the plant providing one source of of fsite power.
If the Port Gibson to South Vicksburg line is out of service and the Grand Gulf to Lorman line is energized, the 115 kV power source is considered operable.
However, the source has substantially less capacity in that situation as compared to the entire line being energized.
Therefore, during initial plant startup the PSB-1 voltage verification test was done with the South Vicksbura to Port Gibson 115 kV line out to provide assurance that the capacity is adequate with only the southern portion of the transmission line energized.
(b) The licensee agreed to complete their ongoing study of voltages on the 120 VAC level ie, vital AC distribution, safety related power distribution and control circuits.
Objectives of the 120 VAC voltage study thould be to confirm the adequacy of normal voltages and the setpoints of the degraded grid voltage relays.
(c)
The licensee agreed to put in place cautions on the use of DAPPER for subprograms not covered by the verification and validation done by the licensee.
(d) UFSAR Section 8.2.3, Stability, should be reviewed in detail for accuracy, and revised as necessary.
In particular, the following two sentences on-3-
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pace 8.2-13 should be addresses.
"The 115 kV feed has a minimum capacity
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Computer and annunicator alarms are sounded if the capacity decreases below this limit."
The referenced alarms were never installed because the 115KV system was demonstrated to have sufficient capacity at initial plant startup even with the Port Gibson to South Vicksburg line out.
Af ter reviewing the calculated bus voltages and motor terminal voltages for the various scenarios, the team agreed that the system was capable of maintaining voltage at the proper levels for all design basis events.
The only weakness was the lack of a formal study on the 120 V level.
The team also agreed with the setpoint of the degraded grid voltage relays as well as the accuracy of the relays and devices used for the application.
3.3 4.16 kV VAC AND 480 V ELECThiCAL LOADING Each division of the tsree 4.16 kV Class IE buses has its own Diesel Generator (DG) set; Division I and 11 each has a 7000 kW (0.8 pf) DG, and Division III has a _3500 kW (0.8 p(f) DG.Division 111 is exclusively dedicated to the High Pressure Core Spray HPCS) system, and Divisions 1 and Il power the balance of the Class lE loads. The load shedding and sequencing logic for Division Ill is completely different from the load shedding and sequencing logic for Divisions I and 11.
.Se team separately reviewed Division I/II and Division 111 load and sequencing logic.
The results are discussed below.
3.3.1 EMERGENCY DIESEL GENERATOR LOADING (DIVISIONS I AND II)
Steady-State in reviewing the Calc. E-DCP82/5020-1 on the transient and steady-state loadings on 001 -and DG2 during load sequencing, the team found some minor errors in the calculations and equipment ratings, which -did not match-the latest load demands.
A (900 hp) 717 kW SSW pump-motor was used in the calcu-lation, instead of the 997 kW (1250 hp) SSW pump-motor and did not consider the load. center transformer magnetizing current at the initial step of the sequencing.
Consequently, the licensee revised the load shedding and sequencing calculations during the inspection period.
In the revised calculations, the total connected load on each bus is about 5500 kW.
The _ total running load under the worst postulated LOCA condition is about 5424 kVA at power factor 0.9 in Division I, and 4483 kVA at power factor 0.9 in Division II.
Depending on the initiating events, there are 5 or 6 steps in the sequencing logic, having a time interval of five seconds between.
The starting time of_the largest LPCS pump-motor (2000 hp) in Division I is less than 3 seconds under the worst voltage conditions.
The largest load in Division 11 is the SSW pump-motor of 1250 hp.
The starting time is less than 2 seconds under the worst voltage conditions.
The team found no starting or loading problems in either Division I or Division !! load sequencing logic and the total loads on Division I and Division !! buses, even under the worst postulated accide%
condition, are well within rating of each DG,
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Transient The voltage and current traces of the oscillogram in the 18 month surveillance test report were compared with the transient load demand during the load sequencing.
The test report indicated that the DG would experience less than 13 percent voltage drop in starting the largest motor load, and the voltage recovered back to nominal within 1.5 seconds.
The voltage dip and frequency drop are well within the limits as specified in the technical specifications.
The team concluded that the DG would maintain the voltage ano frequency regulations within the limits as specified in RG 1.9 and IEEE 387 3.3.2 EMERGENCY DIESEL GENERATOR LOADING (DIVISION 111)
Division 111 is dedicated to the HPCS pump-motor (3500 hp), and its required standby auxiliary equipment such as the HPCS Cooling Water Pump, heaters and battery charger.
The total auxiliary load is about 200 kW, which is less than 5 percent of the total Division 111 load on the bus.
There is no load shedding and sequencing logic as in Division I.
Except for the HPCS Cooling Water Pump, which is delayed 10 seconds, all the loads on this bus are energized when the DG3 generator breaker is closed to the bus, in reviewing the 18 month surveillance test report of DG 3, the team found that the DG terminal voltage dropped to 2625 V (63 percent of 4.16 kV nominal) and recovered back to 4200 V within 4 seconds.
The frequency dip is within 2 percent of the nominal 60 Hz.
The Division til bus voltage kept rising slowly from 63 percent of nominal voltage and did not experience any subsequent voltage dip.
The loads at the lower voltage level would not drop off due to undervoltage.
It has been demonstrated during routine surveillance load testing that the DG3 is capable of supplying power 'o all the designed loads on the bus.
It is stated in the IEEE 387, a larger decrease in voltage and frequency may be justified for a DG unit that carries only one large connected load.
The team considered such a design complied wit.h RG 1.9 and the IEEE 387 standard.
The team concluded that DG3 is properly designed and sized to perform both the steady-state and transient duties.
3.4 ELECTRICAL CABLE SIZING CALCULATION The adequacy of the 4.16 kV and 480V V cable systems to function under all postulated normal and abnormal operatir.g conditions was examined.
The team reviewed the Calc 3-Q (Minimum Cable Sizing Calculations), and Calc 15-Q (Cable Ampacity Calculations, Power); and found that all the cables were only sized to the temperature rating and the thermal stress of the cable insulation under normal running empecity at 90 degrees Celsius and under fault condition at 250 degrees Celsius.
The calculaticns does not consider the cable vc! Ne drop during starting or running conditions.
Several cases were found in the 480 V MCC system where the cable voltage drops are very close to the limits as specified in the Design Guide E2.ll.2.1, Section 4.1.6.
The team observed an error in Calculation No. 3-Q, in that the short circuit rating of the No.10 AWG wire should be 4300 Amps instead of 7500 Amps.
As a resul t, the MCC breaker would not properly protect the wire.
The licensee revised the calcula-tions; based on the resistance, and breaker contacts resistance.
The result indicated that the MCC breaker still would not properly protect the wire, if-5-
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the fault occurred within the first 30 feet from the MCC in Division I/II, or within the first 50 feet from the MCC in Division Ill.
Although the wire is not totally protected, the breaker is sized to protect the equipment -it supplies and a faulted cable would require replacement if damaged.
Therefore,
no modifications are required.
The licensee acknowledged the team's finding and agreed to prepare any necessary dtsign procedures to ensure that future MCC loads would be properly protected by th9 MCC breaker, and any newly installed wire would be sized to withstand the sho't circuit fault level at the MCC.
3.5 MOTOR SPECIFICATIONS The team reviewed two motor specifications for C00 hp and larger motors, and
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one motor specification for the integral and fractional motors, which included the requirements for motor temperature rises and insulation classes, radiation, and seismic requirements.
The team evaluated the motor terminal voltage requirements to ensure that the motor would successfully start and run under the worst postulated system conditions.
In -conjunction with the motor speed torque curves, and the load (pump) speed torque curves, the team reviewed the starting capabilities and starting times under 100 percent, 88 percent, 80 percent, and 75 percent system
nominal voltages for the High Pressure Core Spray (HPCS) pump-motor (3500 hp),
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and Low Pressure Core Spray (LPCS) pump-motor (2000 hp). The starting capabili-ties of the Standby Service Water (SSW) pump-motor (1250 hp), and Residual Heat Removal (RHR) pump-motor (1000 hp) were also examined and found acceptable.
3,6 TRANSFORMER BIL RATING AND VOLTAGE PROTECTION The team reviewed all the ESF (Class 1E) load center 4.16 kV/480 V transformer ratings, temperature rises, insulation classes, voltages, and Basic Impulse Levels (BILs). The dry type transformers in Divisions I and 11 are designed to o60 kV BIL; and the HPCS MCC dry type transformer in Division til is designed to 95 kV BIL.
There are voltage surge arresters installed on the secondary side of, ESF transformers Nos.11,12, and 21. The team considered that these load center transformers are properly sized and designed for their intended functions, _and the 4160V Class lE system is properly protected from voltage surges.
4.0 CLASS lE 125 VOLT DC AND 120 VOLT AC SYSTEMS The team reviewed several features and components of the ICL VCC and 120 VAC Class lE power-convers' ion and distribution systems. The designs were evaluated for system requirements and parameters; correctress and accuracy;- and standard
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engineering practices.
The-designs were compared against the applicable USNRC Regulatory Guides,-National Electrical Code and-IEEE/ ANSI standa ds.
Review of the DC system included:
the batteries; ground fault detection system; voltage drop studies; voltage level alarm settings; cable sizing calculations; and the associated battery chargers design.
The evaluation of the fault study calculations included the review of breaker / fuse coordination and sizing to determine if protection schemes used for the station design conformed to recognized industr, standards and practices.
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The review of the uninterruptable~ AC power supply system included the inverters-and constant voltage transformers siring and design criteria for their abiiity to meet applicable power input / output requirements; the breaker / fuse coordina-
tion and sizing to determine if protection schemes used for the station design-conformed to recognized industry standards and practices.
Fault study
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calculations; voltage drop studies; and cable sizing calculations were not available for the review.
4.1 125 VDC SYSTEM 4.1.1 125 VDC CLASS 1E BATTERY AND CHARGERS Sl/ING The team reviewed battery calculations:
EC-Q1L21-85001, EC-Q1L21-90032, l
EC-Q1L21-90020, EC-0lL62-89002.
Based on the review, the team concluded that the ratings of the batteries and chargers were compatible with the present-loading, for all analyzed conditions.
4.1.2 VOLTAGE REGULATION AND CABLE SIZING The team reviewed calculetions developcd as part of the licensee's electrical system design basis review of the Div III 125 VDC system.
These calculations did not indicate that all loads would be provided with adequate energy to meet the load manufacturer's recommended minimum voltages when the relatively large battery terminal voltage drops occur during a DBA with the charger lust due to
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A Minor change package No. 90/10/0 was developed which resulted in the use of e spare conductor in the original three conductor power cable in parallcl with the existing positive conductor for the cables frra the terminals of battery 100 to Distribution Centers 11DC and from 1100 to the loads.
In addition changes were made to eliminate the excessive cable-length in one instance.
Review of calculation EC-QIL21-90023, Rev.1, verified the adequacy of the corrective action and demonstrated that adequate battery terminal voltage will exist et the onset of a DBA.
The licensee established by testing, a minimum operating voltage at which various equipment will. operate.
Administrative procedures were developed that will require replacement of equipment should it fail to operate at the designated minimum voltage when tested periodically.
4.1.3 125 VDC SWITCHGEAR SHORT CIRCUlT RATD!GS The team reviewed the interrupting ratings of -secondary distribution CBs.
GE, the supplier of those - CBs (type THED), had submitted data sheets with
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conflicting information.
Originally, GE rated the CBs at 20 kA but indicated that they were UL listed as 10 kA. The latest GE catalog information indicated
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that the breakers were rated at 20 kA with a note that they were not listed with UL.
After review of all information available, the team accepted the CBs as rated-20 kA.
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4.2 120 VAC CLASS lE UNINTERRUPTABLE POWER SUPPLY (UPS)
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4.2.1 120 VAC 1E INVERTER MODIFjCATION
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The team reviewed the design features of the UPS systems (two channelized inverters per Divisions I and II).
Each system included a 120 VAC Class IE Inverter and an associated constant voltage transformer (CVT).
These have been added per DCP 88/0051 to upgrade the original UPS system whost design did not provide for sufficient flexibility to permit easy maintenance accessibility of the power conversion equipment.
The team observed that even though the two inverters per division were identical (with nominal input curre nt of 90 A), one inverter was fed directly from the main DC bus through a 600, '00 Anp "8, and the other inverter was supplied through a 300/50 Amp CB from a sub-di.tribution panel.
The panel was
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bolted directly to the main DC bus.
Reviei of TST! IL62-90-003-0-S Appendix 11.3, and E -Q1162,89002 indicat,ed tb t the load on 100/50 Amp breaker was approximately 38.4 Amp at 105 volts (or 75 percent of the CB nominal rating).
The team observed the new CVT' ratec at 15 kVA, nominal input current of 37A at 480 VAC, were protected with 30 An.p CBs.
These CBS supplied the 7.5 kVA rated l
rectifiers originally installed. With the CVTs presently loaded at 2.5 kVA and 4.5 xVA respectively, the input current to the CVTs will be approximately 23
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Amps at the minimum system input voltage of 432 volts.
If the CVT loads are-increased, the 30 Amp CB may not be large enough when the minimum input voltage is experienced.
The above conditions would severely limit future addition of loads.
The licensee agreed to perform additionai calculations to establish load limits to AC and DC input sides to ensure that breaker load limits are
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l not exceeded.
4.3 CONCLUSION 5 The team raviewed the designs of the Class lE 125 VOC and 120 VAC systems and concluded d ot the systems met all of the design requirements, except for the loss of coordination of protectiva devices on the main DC distribution panels in Divisions I and II, see Item 5.3.
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The team observed that :n the recent design calculations, which were generatet l
by the licensee (all calculations numbered with a prefix "EC-Q1"), the inputs l
were based on the actual component / system loading, not the nameplate reting or the ultimate loading.
This results in a more realistic calculation.
The results of the ana'ysis showed that only limited margins were present in the desians, therefore future load growth could be limited.
5.0 PROTECTION AND C0 ORDINATION
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5.1 4.16 kV AC SYSTEM PROTECTION AND COORDINATION The team reviewed the protection coordinations on all three diesel gene'ators,
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l incoming feeders to the 4.16 kV bus, 480 V MCC feeders, and 4 kV motor faeders.
The review included under voltage relay settings, ground fault protection settings, overcurrent relay settings, and differential relay sottings of the diesel generators.
The team did not observe any coordination problems, except a number of minor errors as noted below.
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A.
On page 24 of the Calc. 15-Q, Cabic Ampacity Calculation (Power), the full load current of the SSW pump-motor should be 160.8A instead of 104A.
The licensee agreed to revise the document accordingly, Such an increase from 104A to 160.8A would only reduce the safety margin of-the cable, and would neither affect the operability nor the safety of the system.
B.
In Calc. EC-0lP75-90002, Sizino of Grounding Resistors for ESF Buses 15AA and 16AB Standby Diesel Generators, sections on Assumptions and
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Methodology are missing, and the formula under Section 6.1 required some editorial corrections.
The licensee agreed to revise the document accordingly.
The team found that the results of the calculations rermined correct, and the calculations were not affected by the missina sections.
C.
In PR 29 (Protective P.elay), the Division 11 incoming breaker overcurrent protection calculations are based on the starting of the RHR pump-motor and the maximum running load is 4330 kW.
With the size increase of the standby service water pump to 1250 hp, the maximum running load in Division !! became 5000 kW and the starting of the SSW pump motor is the
worst case.
The margin between the incoming breaker overcurrent time delay curve and the SSW pump overcurrent time delay curve is very narrow, i.e., less than 1.5 seconds.
The licensee agreed to review the overall overcurrent pr:tection scheme of the Division 11 bus, and will revise the l
' settings as required.
The team considered the present protection coordination settings on Division fI bus acceptable.
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l 5.2 480 V SYSTEM PROTECTION AND COORDINATION The team reviewed the 480 V system equipment ratings, incoming feeders. MCC feeders, and motor feeder protection coordinations.
Protection coordinations included ground fault and overcurrent relay settings and coordinations.
The team reviewed the protection coordinations of the HPCS Cooling Water Pump,
.Orywell Purge Compressor, and SSW Cooling Tower Fan.
The team considered that the protection coordination has been properly specified.
L The team reviewed both the AE's original MCC overcurrent protection calcula-tions E-49, and the recent calculation EC-Qllll-90001, which was prepared by the licensee in October _1990.
The overcurrent time delay protection is set at about 1.25 pu'(per unit) of full load, the high-dropout protection is set at about 1.75 pu of full load, and the instantaneous trip is set at 2 pu of the starting current at 100 percent motor voltage.
The team found these criteria are comprehensive, technically sound, and generally well prepared.
However, the team also observed that the protection settings recommended in
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EC-Q1111-90001 varied slightly from the existing MCC breaker settings. The
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licensee agreed to review the subject matter in more detail, which may potentially result in resetting the MCC protection on a case by case basis. The team accepted the licensee's proposal; a future review is recommended,
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5.3 125 VDC 1E DISTRIBUTION SYSTEM PROTECTION AND C0 ORDINATION The team reviewed the 125 VDC lE Distribution System Protection Coordination calculations: PR148, PR151, PR160, PR61, EC-Q1L21-90026 and EC-Q1L21-86003.
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The team observed that there were some inconsistencies between calculations EC-0lL21-90026 EC-0lL21-88003 PR148 PR151, and PR162.
Even though these were
all related to the primary distribution system, some of the assumptions were
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different from calculation to csiculation.
The licensee agreed to revise the
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calculations as a part of an ongoirg progran.
l The design of t'ie primary distribution system in Divisions 1 and 11 had been
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J recently revised, as per DCP-87/0034 The revision involved addition of fuses
.i in-line with two of the CBs. The team found that addition of the fuses between the batteries and the battery to-bus CD resulted in loss of coordination of protective devices in the branch circuits.
This is identified as violation
90-24 01 Inadequate Evaluation of DCP 87/0034 For details see finding
90-24-01.
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5.4
,120 VAC IE DISTRIBUTION SYSTEM PROTECTION AND COORDINATION There were no calculations related t0 coordination of the protective devices
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and voltage drop for the station I?0 VAC system, including the Class IE system.
The licensee explained that these calculations would be available in 2nd quarter of 1991, as part of the ongoing effort to generate, update and unify c
all electrical system analysis.
Any observations related to this system at e based on the review of the original desfgn documentation, mostly AE drawings.
i The Division I and !!, UPS distribution systems wert: nrotected with fused
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disconnect switches in tFe main power distribution panei (e.g., panel lY89).
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Each distribution circuit had up to 3 in-line fuses from the main distribution panel to the individual circuits. Those fuses were arranged sequentially i.e.,
a a 20 A fuse fed a 10 A fused circuit that fed several 5 A fused circuits to the i
instruments.
The team reviewed sempics of the 120 Volt single phase distribu-tion system protection coordination from the distribution panels to the
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individual loads and determined that there was proper coordination for this
system.
6.0 MECHANICAL SY5 TEM; JPPORTING ED_S S
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j The inspection team reviewed and evaluated the adequacy of selected mechanical systems supporting the EDS. The systems reviewed included:
Diesel Generator (D/G) systems;
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HVAC (diesel generator rooms, switchgear rooms, battery rooms).
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Standby Service Water System;
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The review consisted primarily of a review of licensing, design, and operating documentation.
Several walkdowns of the systems were conducted.
The team
found no major errors in the design, construction, or operation of the reviewed
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systems.
Some concerns were raised by the team; all concerns were adequately l
_ addressed by plant staff.
6.1 DIESEL GENERATOR FUEL 011. SYSTEM 6.1.1 FLAME ARRESTORS ON FUEL Oil STORAGE TANK VENTS ANSI N195 requires that each fuel tank be provided with a vent and flame arrertor.
The vents on the 1/G main fuel oil storage tarks are not equipped
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with flame arrestors.
The inspection team questioned whether this incon-sistency with ANSI N195 had-been evaluated.
Plant staff presented documenta-tion demonstrating that the temperature of the fuel storage tanks, which are t
buried underground, does not exceed 68 degrees f, and that this temperature is low enough to prHude ti.e generation of fuel vapors in cuantities sufficient j
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to constitute a h ord.
The inspection team found this evaluation acceptable.
I 6.1.2 FUEL OIL STRAINERS
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in order to ensure long-term uninterrupted operation of the diesel generators, current standards recomniend that each of the diesels be provided with a dupler strainer in its fuel line, and that each strainer in turn be equipped with a differential pressure indicator and a control room alarm on high differential pressure.
The arrang. vent of the Grand Gulf diesel generators fuel oil strainers is as described below:
Divisions I ar,J 11 Erch of the Division I and !! systems has a single uninstrumented (i.e., no
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-differential pressure indication or alarm) Y-strainer located in the main fuel l
transfer line (i.e., between the fuel storage tank and the day tank).
Also, a single Y-strainer is provided upstream of each electric motor-driven fuel pump, and a duplex basket strainer is provided upstream of each engine-driven pump; these fuel pump strainers all have differential pressure indication and alarms.
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Division !!!-
The Division !!! fuel oil system also has a single uninstrumented Y-strainer located in the main fuel transfer line. Additional duplex basket strainers are
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provided upstream W each of the motor-driven fuel pumps, and single basket o
l strainers are pro m i upstream of each of the engine-driven pumps.
None of the strainers in the Division 111 system has differential pressure indication.
The. inspection team questioned the use of single, uninstrumented Y-strainers as the primary straining elements.
The licensee responded to the team's concern with the rationale -that, should' fuel flow to a day tank be restricted by a blocked Y-strainer, the day tank level would drop to the 55 minute level (i.e.,
the level of fuel required to maintain diesel operation for 55 minutes), at i
which point the day tank low level alarm would actuate.
The operator could, within the 55 minutes available before loss of the diesel, diagnose the problem. clear-the strainer, and reestablish fuel flow, lhe plant staff agreed to modify the Day Tank Alarm Response Instruction to assure that operators promptly verify strainer condition on day tank low level alarm. The inspection team fnund this action adequate.
6.1.3 LINE-UP Of DUPLEX STRAINERS i
As explained in 6.1.2, duplex strainers are used in some portions of the D/G fuel 011' systems.
Grand Gulf plant operating procedures contain no provision for the proper line-up of these duplex strainers.
This increases the probability that operators could keep both elements of a duplex strainer valved
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in, in response to the inspection team's concernt, Grand Gulf plant staff agreed to revise system operating instruction 501 04-1-01-P75-1 to speci fy proper line-up of duplex strainers, f>,1.4 FUf' 0!L STORAGE AND DAY TANK VOLUMES AND l f VEL SETPOINTS Fuel oil requirements and tank level setpoints have recently been recalculated by Grand Gulf engineering personnel, and fuel tan 6 level alarms have been reset accordingly.
The inspection team noted, however, that fuel tank volume and setpoint references in the FSAR, design specifications, and Operating and Surveillance pr0cedures have not yet been updated.
Given that some of the old values are incorrect, it is recommended that these documents be updated as soon as possible.
6.1.5 FUU 70 RAGE AND TRANSFER SYSTEM Contrary to Section 9.5.4.1.1.d of the Grand Gulf Unit 1 FSAR, the vent lines on the fuel oil storage tanks are neither seismically qualified nor protected from tornado-generated missiles.
The inspection team raised the concern that damage to the vents could result in loss of tank venting, and consequently impede fuel oil flow to the day tanks.
Grand Gulf staff responded that this issue had recently t>een identified by the plant staff, and a study of the situation has since been completed.
The study determined that, should a tank vent be blocked, the day tank overflow line leading to the storage tank oculd act as a vent.
The staff also presented a report demonstrating that the check valves on the overflow lines would not impair the venting function.
The inspection team found the staff evaluation adequate.
6.2 HEATING, VENTILATION AND AIR CONDITIONING D' SIGN CALCULATIONS HVAC calculations for Safeguards and ESF switchgear rooms and the diesel generator rooms were reviewed and generally found to be adequate; hewever, mechanical calculation 3.8.31, A Q. "Safeguarus Switchgear and Battery Rooms Ventilation System" should be reevaluated for the following reasons:
a.
Room temperature values used in calculating heat transmission between adjacent rooms are incorrect.
When evaluating a given room the calculation does not use minimum and maximum design temperatures for the adjacent roors, and consequently underestimates summertime cooling requirements and wintertime heating requirements,
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b.
Equipment loads used in the calculation of winter heating requirements do not represent the worst case.
The calculations assume maximum, rather than minimum, heat output from electrical equipment, c.
No margin is provided in the calculations for degraded system operation, for example, reduced air flow due to dirty air filters.
Plant engineering has connitted to fully review and revise this calculation.
It should be noted that the subject calculation is an older AE document that has not yet been addressed by Grand Gul f's ongoing program of review and revision of original plant design documentation.
The Grand Gulf staff calcula-tions that were reviewed proved to be of very good quality.
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6.3 DIVISION 111 D!fSEL GENERATOR COOLING WATER
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Cooling water for the Division 111 diesel generator and dim el generator room
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i is provided by loop C of the Standby Service Water System, the inspection term i
noted in the original plant design that Loop C, together with Loop A, is cooled i
by a mechanical draf t cooling tower powered f rom the Division I bus.
The
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concern was raised that, on loss of Division ! power, the Division 111 diesel
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and diesel room would no longer get the cooling required to maintain design
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performance of the equipment, thereby violating station design criteria requiring a minimum of two divisions in operation at all times, plant staff
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responded that this desion condition had already been recognized as potentially
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deficient and had recently (i.e., during the October-November 1990 outage) been
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corrected under DCP 90-551.
The design correction consisted of removing loop C from the Division I cooling tower and connecting it to an unused cooling tower that had originally been built for Unit 2.
No power is required for the new
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tower because loop C's flow is low enough (i.e., witnout loop A) that adequate cooling can be echieved with natural draf t only.
The inspection team found i
this response adequate.
6.4 CONCLUSIONS
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In general, the design and operation of the mechanical systems supporting the j
EDS at Grand Gu!f was found to be adequate.
A few minor discrepancies were i
found in design calculations and operating documentation, and all of these had either already been recently addressed by plant staff, or were responded to
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quickly by staff during the course of the review.
i The inspection team found that design and operating documentation was generally of very good quality.
Grand Gulf's ongoing program of review and revision of
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original plant design calculations and documentation is proving to be very effective in assuring design integrity and a solid document baseline.
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The mechanical engineering and operations steff with whom the inspect 1on team dealt proved to be very competent.
Their knowledge of system design, history, and operations was evident.
There also appeared to be a good relaticaship between engineering and operations personnel, with correspondingly complete
reviews of operating events and system modifications.
7.0 EDS EQUIPMENT The team performed walkdowns to confirm the configurations of the electrical system design, and the "as-installed" condition of selected electrical equipment in the plant.
The selected equipment and systems inspected included:
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34.5 kV Switchgear and transiarmers in the 115 kV/500 kV switchyard.
- Main 20.9 kV/500 kV transformers (one per phase)
Three engineered safety feature (ESF) transformers (one 115 kV/4.16 V and
two 34.4 kV/4.160 kV)
The switchgear, cables, and cable routing from the two 500 kV/34.4 kV
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i service transformers in the 115 kV/500 kV switchyard to the two ESF 34.4
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kV/4.16 kV transformers down to the 4.16 kV safety-related buses.
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The switchgear for all three 4.16 kV safety-related divisions.
- The three standby diesel generators and associated electrical cabinets.
- The 480 V safety-related motor control centers (MCC)
The batteries, battery chargers,120 VAC inverters and distribution
centers for the 125 VDC system.
Overcurrent and undervoltage protective relays for the 4.16 kV safety-
related buses.
ESF transformers for the non safety-related 4.16 kV switchgear.
- Standby service water (SSW) pump motors and switchgear.
- 7.1 EQUIPMENT WALKDOWNS Walkdown inspections were performed by the team to verify the EDS equipment conformed to design requirements.
Drawings used for the field inspection reflected the "as-installed" configuration.
The material condition of the electrical equipment was satisfactory.
The equipment appeared to be well maintained and very few deficiency tags were observed.
The equipment was labeled, easily identifiable, and accessible, adequate separation existed in the plant for all EDS equipment observed by the team. Although the EDS equipment was considered satisfactory, several walkdown items were identified and are discussed in the following paragraphs.
7.2 DIESEL GENERATOR CONTROL CABINETS The doors of the Division 11 standby diesel generator electrical panel H22p401 were found open and left unattended.
This was in violation of the licensee's System Operating procedures 041-01-P75-1, Revision 36, Standby Diesel Generator System.
This resulted in a non-cited violation further discussed in Appendix A.
In the electrical panels, the team observed uncontrolled fuse lists.
This is further discussed in the following paragraph.
The team also observed that spare 4.16 kV circuit breaker switchgear cou'd be placed in the wrong _ position for a seismic event.
This is further discussed in Paragraph 7.4 The team identified a minor item where the divisional label color for-panel lY85 was a nlow instead of green.
This was quickly corrected by the_ licensee.
Overall, the team consider the EDS equipment inspected met the design requirements of the drawings and to be in a very satisfactory material condition.
The system engineers and maintenance personnel supporting
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the walkdown - in(0:ctions were knowledgeable, competent, and acted in a professional man.ier.
7.3
?USE REPLACEMENT PROGRAM-l During the walkdown inspections of the electrical panels, the team observed L
that a neatly typed fuse list was in each electrical panel, These fuse lists l
identified each fuse, their size, fuse number, and drawing but did not specify type.
Upon _further investigation, the team learned these fuse lists were placed in the panels by the electrical maintenance department.
Although the
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L information on the fuse lists appeared to be correct, the fuse lists were not in a controlled program.
The team also identified that the fuse type (s) were not identified on design drawings.
This is considered a program weakness.
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7.4 EQUIPMENT INSTALLED SPARE SWITCHGEAR During the walkdown inspections of the ESF 4.16 kV ITL switchgear, the team
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expressed concern that spare circuit breakers may not be properly secured for a
seismic event.
The breaker could be racked out and not physically secured to the cabinet.
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This would allow the breaker (s) to be free to roll out of the cabinet during a
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seismic event.
The plant procedures did not adequately differentiate between the " disconnect" position and " racked out" position.
The " disconnect" position
is racked out but physically locked to the panel.
" Rocked out" position is i'
racked out and not locked to the pane?.
The licensee agreed to correct this potential problem by revising the following procedures to differentiate between the " disconnect" and " racked out" positions.
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01-5-06-1 Protective Tagging System 04-5-04-2 Operation of Electrical Circuit Breakers c
07-5-12-42 Inspection and Testing of ITE SkV Circuit Breakers
The team considered the revising of the procedure as acceptable corrective
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action to ensure the spare breakers are in the secured position.
The licensee surveyed all spare breakers in the Division 1. !! and Il switchgear rooms and breakers were verified to be in a disconnect position.
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7.5 EQUIPMENT -' MOLDED CASE circuli BREAKER TESTING lhe team determined the licensee does not verify operability of safety-related
molded case circuit breakers by periodic testing.
This apnlies only to breakers which have thermal trips that are not by-passed, The licensee only tests the instantaneous trip function of breakers that are listed in the
- Technical Specifications for containment penetration circuits.
The breakers used for the 480 V motor operated valves have their thermal trips by-passed.
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However, the breakers in the 125V DC system have thermal trips and these breakers are not tested.
This is a generic issue and is being evaluated by the NRC for industry wide action.
8.0 EQUIPMENT - MAINTENANCE, TESTING AND CALIBRATION The tear, reviewed the maintenance procedures, calibration procedures, and data sheets for the following EDS equipment:
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Standby diesel generators
480 V and 4'.16 kV switchgear safety-related
Load shedding and sequencer (LSS) controller
-0vercurrent relays - 4.16 kV ESF Buses
Undervoltage relays - 4.16 kV EST Buses
Division I and 11 degraded voltage bistables ESF transformers overcurrent relays (not safety-related)
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General maintenance ins' mctions for switchgear 15 -
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The team reviewed the TS Section 4.8.2.1 and the surveillance procedures:
06.LL-llll-Q 0001, 06.LL-llll-R 0003, 06-EL-lLll-0 0001, 06-El-llll-R-0001, which described performance requirements / acceptance criteria of the Class lE batteries and compared these uith the logs of the periodic tests (performed in 1987 and 1990).
The Division 1 and !! batteries met the TS requirements.
The team observed that for Division !!!, the battery surveillance test data as listed in the TS and Vf5AR Table 8.3-8 was not consistent with the load profile docun4ented in MNCR 83-90 The TS emergency load test requirement is 76 Amps for the first minute.
The MNCR 83-90 calculation reduces the emergency loading to 65 Amps in the first minute which indicates an increase in the margin of the Division til battery capacity.
The licensee is presently testing to the original TS requirements pending NRC approval of a 15 change.
The team observed that the Section 8.3.2.1.6 of Uf 5AR contained a statement that the Division I and 11 chargers could not operate without the battery connected to the bus.
This was contrary to the requirements 11.
d in the equipment specification 9646-E-019.2 Item -8.3.
The licensee agreed to revise
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the UFSAR.
According to UFSAR Section 8.3.2.1.6.2, the DC system used lead-acid calcium batteries that did not require periodic equalizing charge.
The tcom observed that the batteries were being equalized after each performance evaluation test.
The equalizing voltage Las still withir the equipment thoximum rated voltage of 140 volt.
The licensee agreed to revile the UfSAR.
The team made the following observation:
General Maintenance Instruction 07-S-12120, Inspection and Cleaning of
4.16 kV and 6.9 LV switchgear does not require verifying the tightness of bolts and nuts for bus bar connections.
The licensee agreed to revise this procedure to include verifying tightness of bus bar connections.
Three of the 18 type I AC 53A overcurrent relays used for the L5f
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transf ormer 4.16 kV breakers (nonsafety-related) were found out of calibration by 5 percent, 7 percent, and 10 percent. The team considered the three year calibration interval should be evaluated for acceptability.
The calibration procedures for both the 4.16 kV ESF degraded voltage LSS bistables and the undervoltage relays for M160 V ESF Division 111 bus are considered weak.
These procedures do not require that the setpoint be set
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to a desired value.
Instead the setpoint can be set within the allowable tolerances spe:ified in the Technical Specifications.
However, if the setpoint is not set or reset exactly at the desired value, instrument error and drif t could cause the setpoint -to exceed the Technical Specifications allowable limits.
The licensee ogreed the following calibration procedures would be revised:
06 EL-lR21-M-0001 4.16 kV Degraded Voltage f unctional ist and Calibration 06-EL-lp81-R-0001 f 5F Division 111 Bus Undervoltage and Time Delay Relay Calibration.
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The team reviewed the latest calibration data sheets and all relays w$re within
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i the Technical Specification allowable limits.
However, several setpoints had i-drifted from the desired value near the limits but none had drifted out of
specification.
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i The team reviewed the lube oil pressure switch calibration deta sheets for the
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Division I and 11 standby diesel generators.
Several of these switches were l
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slightly out of calibration on the high side.
The team recomended that these i
pressure switches be monitored and the data trended.
The licensee agreed, The team also neviewed the calibration records for the Division I, !! and 111 generator differential relays.
The relays were all found within the al10wable
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range.
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Overall the team found the maintenance and calibration procedures satisfactory.
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Except for the previnusly discussed items the equipment was found to be
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l calibrated, within tolerance, and well maintained.
9.0 EDS MODIFICATIONS
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The team reviewe'l the following modifications affecting the EDS:
a.
DCP No. 88/0051. Replacement of Cless IE Uninterruptable Power Supply System, Revision 0
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i Grand Gulf Nuclear Station has experienced four failures of static i
inverters associated with the above Class JE electrical distribution
l systems since the start of commercial operation.
These failures, in combination with an electrical system coafiguration that prevents i
performing preventive maintenance or TS surveillances without de-energizing the division losd, has resulted in an increased risk of reactor scram during these plant activities.
DCP No. 88/0051 was developed and installed to increase the reliability of the Class IE UPS system and decrease the potential of a_ reactor scram caused by an
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inverter failure.
The inspection team reviewed the DCP to verify that the hardware changes were (1) consistent with the design scope and (2) were
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bounded by safety evaluation number CFR 88/0051R10 performed in accordance with the requirements of 10 CFR 50.59.
No unreviewed safety question was identified during performance of the safety evaluation, Second Level Undervoltag(e Protection and Emergency b.
DCP No. 85/3040, Override of Test Mode for Division 111 HPCS) Diesel generator, Revision I was developed and installed to satisfy a license amendment incorporated in _ T.S._ Change Request No. 86/006, Revision 1.
The plant. modification provided a second level undervoltage protection for the Division Ill Diesel Generator.
The inspection team reviewed the DCP and verified that the hardware
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changes were consistent with the design scope.
Additionally. the control circuits shown on schematic diagram _ number E-Il88-017 was reviewed and verified to be technically correct for. implementing the logic required by the design objectives.
Design basis information
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I concernino relay setpoint values were reviewed to ensure agreement with existino calibration
'quirements; and post modification tests were verified to have been ccessfully completed.
Review of safety evaluation nun ber CF R 85/3D 1R10, Revision 1, revealed that the e'aluation adequately bounded +he activities specified the DCp.
c.
SLR No. 28 documents a f ailure modt of General Electric type AL circuit breabers that involves rnecFanical binding with resulting destruction of the trip coil caused by t;eing continuous energized.
Corrective actions recorrtna by Generel Liectric were increased maintenance and a change in the circuit breeker.abricant.
The licensee has circuit breobers of the type described in the SLR installed on I?5 VDC butses llDA and 11Dii.
The freder circuit breakers are directly mounted to the busses and raintenance cannot be performed without the loss of vital DC loed.
DCp No. 87/0034 was developed and installed to address the deficiency identified in SLR No. 28 The scope of the plant modification involved installing fuses on the load side of safety-related type AL f eeder breakers 72-11 A01 and 72-IIA 0b located in IPS VDC distrit ution center ilDA; and safety-related type AL feeder brealers 72-11l101 and 7P-11B05 located in 125 VDC distribution center 11BA.
The inspection team reviewed the DCp to verify the technical edequacy of plant modification.
Design t> a s i s calculation number EC-OlL21-88003, siring of fuses for 125 VDC feeders 72-11A01, 72-llA05, 72-llB01, and 72-11B05, kevision 0, was prepared to determine the appropriate size and type of fuses.
This calculation demonstrated that the fuses long and short melting t ir>e chardcteristics closely approximated the installed feeder breakers trip-time characteristics.
Adequate overcurrent protection was provided to the feeders based on plotted coordination curves.
The licensee failed, however, to ensure that proper coordination was maintained between the newly installed f uses and existing feeder breakers f or other vital DC loads.
This design deficiency is discussed in Section 3.3.6 of this report.
At the time of the inspection the automatic trip f eature of the type AL circuit breakers had not been disabled, licensee manaoement informed the team that the automatic trip feature of the circuit breakers would be disabled and the brea6ers would be removed f rom the calibration program.
9.1 TEMPORARY SYSTEM ALTERATIONS The inspection team revicwed plant operations r,anual Cl-5-06-3, Control of Temporary Alterations, Safety-related, kevision 23 and verified that administrative controls have been established for control of tempurvy plant modifications.
All temporary activities that inhibits or alter the intended operation of a plant components or system, are required to be entered in the Temporary Alteration Log BoM.
The status is monitored to provided positive control.
The use of temporary r4odifications at Grand Gulf appears to be limited based on review of the Log Book.
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9J CONCLUSIONS
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With the exception of the deficiency identified with DCP No. 87-0034, the team
found that activities related to preparing, reviewing, approving and installing i
plant modifications were performed in a planned and controlled manner, i
l Temporary modifications are used sparingly at Grand Gulf and are positively controlled.
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10.0 ENGINEERING AND TECHNICAL SUPPORT
10.1 ORGANIZATION AND VD STAFF i
The inspection team reviewed licensee's documents and verified that functional I
responsibilities, levels of authority, and lines of internal and external communication interfaces had been established for organizations and key staff.
l As the Design Authority, NPE has been assigned responsibility for control of
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design activities related to modifications or changes to plant safety related structures, systems, and components.
Review of NPE procedures revealed that
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I design-engineering controls are adequate for the preparation, review, and approval of plant modification.: Nuclear Safety Evaluations or screenings are performed fer both temporary system alterations and permanent plant
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modifications.
Additionally, design-basis calculations and/or information are prepared a r.d used to demonstrate the technical adequacy of the design-engineering products.
Interviews with respcnsible engineers showed them
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to be knowledgeable of the design-engineerin, process and qualified for their job responsibilities.
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The team reviewed the functional responsibilities of the PS&E System Engineers.-
They have responsibilities for plant systems design change implementation
including testing and closecut; system performance monitoring and trending;
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problem analysis and resolution; and project management.
Discussions with selected System Engineers showed them to be knowledgeable of their responsi-
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bilities and familiar with their assigned systems.
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System Engineers interviewed have completed a formal training program intended to qualify them for their assigned system responsibilities.
The licensee management plans to provide them training equivalent to that given certified SR0s, 10.2 ROOT CAUSE ANALYSIS AND CORRECTIVE ACTIONS The Corrective Action Program was evaluated by the disposition of the following MNCRs:
MNCR No. 0251-90 MNCR No. 0306-89
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MNCR No. 0304-89 These MNCRs were hardware related problems related to the operability of various parts of the EDS. The team reviewed the dispositioning activities used by the engineering staff to evaluate degraded or nonconforming conditions of safety-related equipment for operability. status.
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.'he activities performed by NPE and/or the System Engineer in support of cc recting the above deficiencies revealed that once a degraded or non confonning condition is identified, a reasonable assurance of safety is made concerning the deficiency.
This determination may be made either during the initial classification of the deficiency as either a hardware /sof tware problea; or during the operability determination.
Based on the sample reviewed the inspection team determined that MNCDs are adequately dispositioned as required by the corrective action program.
Two minor weaknesses were identified and one discussed below, a.
Review of NPE procedures and discussions with NPE staf f members revealed that specific guidance for performing root cause analysis has not been given to the staff.
Licensee Nanagement agreed to develop and issue a procedure to provide this guidance by July 15, 1991.
b.
Long-term corrective aciion related to MNCR No. 0251-90 involving
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testing of components specified b the disposition by NDE has not been incorporated in the P 41ntenance Program.
Licensee management agreed to have '
, January 31, 1991, 10.3 SELF. ASSESSMENT AND TRAld!Nd The inspection team determined that licensee management had performed numerous activities intended to provide critical self-assessment capabilities in various functional areas, included among these was performance of a Safety System Functional Assessment (SSFA) of the Standby Liquid Control System completed in 1988.
A SSFA is scheduled to be performed of the High Pressure Core Spray System.
Post-outa,e reviews of Change Notices have been performed to assign
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attributable causes for changes made to approved DCPs.
Quality Engineering Report No.89-428 documents the causes attributed to NPE and provide infor-mation to licensee management concerning these causes along with recommended corrective actions.
Analysis of data accumulated during the first six months of the licensee's Quality Engineering Review are documented in Quality Engineering Evaluation Report No.89-429.
Cause codes were assigned for identified deficiencies and recommended corrective actions were included in the report.
Additional information required by licensee management to provide self-assessment capabilities are contained in the quarterly Quality Programs Status and Trend Analysis Report to Management.
Graphical representation of selected performance indicators used to assess the effectiveness of licensee's actions in various functional areas are documented in this report.
Review of selected deficiencies contained in the above reports revealed that recommended corrective actions had been completed.
Personnel training required as part of the corrective actions were reviewed for adequacy and verified to have been implemented.
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10.4 CONCLUSIONS The inspection team determined that adequate engineering and technical support functions are provided to Grand Gulf Nuclear Station.
The primary organiza-tions having key responsibilities for ensuring the technical adequacy of the EDS, are staffed by trained and qualified personnel.
Discussions with selected
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a staff members revealed that they were knowledgeable of their job responsibili-ties and a strong commitment to doing the job right the first time was obvious
during the personal interviews.
Licensee management's involvement in assuring quality was demonstrated by the numerous self assessment activities initiated
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at management's own volition.
Finally, the capability of the self-assessment activities to identify and fix problems was demonstrated by the findings
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documented in the reports reviewed along with evaluation of the technical adequacy of *he developed corrective action plans.
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11.0 GENERAL CONCLUSIONS
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g Based on the inspection sample, the team did not identify any operability
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problems, and concluded that the design of the EDS system was generally
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adequate.
Emergency power sources were sired properly and adequate voltage was applied to essential Duses with regard to EDS loads.
The protection and
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coordinttion of the protective equipment ere adequate and the scope of testing
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the EDS equipment was appropriate.
Statf support for the EDS from the-corporate office and site was adequate.
12.0 EXIT MEETING An exit meeting was held on December 14, 1990, at the plant site.
The findings of the inspection team were-discussed at that time.
There were no dissenting a
comments received.
Proprietary information is not contained in this report.
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APPEND!X A I
VIOLATION 90-24-01
INADE00 ATE EVALUATION OF DCP B7/0034 i
flNDING:
Division I and !! 125 Volt DC Main Distribution System.
No
coordination of circuit breakers and the fuses in the battery-to-bus feeder (Section 5.3 of report).
DESCRIPTION:
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The following describes the Division ! distribution system, however the Jame applies to the Division 11.
In the original design of the 125 Volt DC System only CDs were used te protect the main distribution system from the effects of short circuits.
The CDs
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rating was as follows:
the main battery-to-bus CB 2000/1600 Amp, the i
charger-to-bus CDs (2 CDs per bus) 600/600 Amp, the bus-to-inverter 600/400 Amp, and the bus to-distribution panel 600/400 Amp.
All CBs are directly
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bolted to the bus.
This precludes periodic maintenance and calibration of the trip elements without shutting down a complete division of the DC system.
Before the modification, there was full coordination between those CBs in the DC systems.
A disclosure of_a generic problem with the typ.
CBsinuse(GEAKbreakers),
resulted in the licensee issuing the DCP 87/005,
This DCP added fuses in line with the main battery-to-bus CB (1200 Amp fuses) and the bus-to-distribution panel CB (400 Amp fuses).
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The 1200 A f uses in the battery-to-bus feeder was selected to duplicate the
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"long time" characteristics of the CB and to provide full protection for the feeder cable, However, the "short time" characteristics of these fuses was such that there was not proper coordination between the charger-to bus CB and j
these battery-to-bus fuses.
Coordination between the bus-to-inverter CB and the fuses was only marginal.
The clearina time of the 600/400 Amp CB for the bolted short circuit fault was
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only 25 to b0 milliseconds shorter than that of the fuses.
Such a short tie
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difference would not prevent the fuses from starting to melt.
Had this been recognized, an administrative procedure should have been instituted to ensure that the fuses would be replaced every time following a forced operation of the CB.
The licersee had no such procedure.
The system, as modified by the DCP 87/0034 was not acceptable because a single fault at one of the three critical points of the main-distribution system would
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-disable the complete system (DC and AC from the UPS) for that division,
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REQUIREMENT:
10 CFR.50, Appendix B, Criterion Ill, and the accepted QA Progran require establishing measures to assure that applicable regulatory requirements and the
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design bases are correctly translated into specifications, drawings, procedures, and instructions.
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NON-CITED VIOLATION 90-24 02
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l TITLE:
TAILURE 10 FOLLOW PROCEDURE FOR OPEN DIESEL GENERATOR ELECTRICAL
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CONTROL CABINET
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DESCRIPTION Of CONDITION:
i The NRC team performed walkdown inspections of the three standby diesel I
generators (D/G).
During the walldown the inspectors identified that the doors of panel H22-P401 for the Division 11 D/G were open and left unattended.
Panel
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H22-P401 is the electrical control cabinet for the D/G.
Step 3.33 in System Operating instruction 04-1-01-P75-1, Revision 36, Standby Diesel Generator i
System Safety-Related states that open panel doors should not be lef t
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unattended.
This is due to the increased probability of damage in a seismic event while the doors are open.
The licensee initiated Quality Deficiency Report (QDR) 0247-90 to address the violation of procedure 04-1-01-P75-1,
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Section 3.33, for the open doors of panel H22-p401.
The licensee stated in the
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QDR that the operator rounds of the DG were modified during the refueling outage from eight hours to 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> to match the outage working hours.
The corrective action taken by the licensee besides closing and locking the doors
was to have the operators rounds returned to every eight hours.
In addition.
a signs will be manufactured and placed on the panel door alerting all personnel
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of the door requirements to be " closed" when lett unattended.
The NRC team
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determined the licensee properly addressed this concern in the QDR and appropriate corrective action was being taken to prevent reoccurrence, This
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NRC identified. violation is not being cited because criteria specified in
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Section V.A of the NRC Enforcement Policy were satisfled.
REQUIREMENT:
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10 CTR Part 50, Appendix B, Criterion V, Instructions, Procedures, and
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Drawings, require activities affecting quality shall be accomplished in accordance with the instructions and procedures.
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APPENDIX B ACRONYMS AND ABBREVIATIONS A or Amp Amperes AC Alternating Current AE Architect Engineer ANSI American National Standards Institute BIL Basic Impulse Level CB Circuit Breaker
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CFR Code of Federal Regulations CVT Constant Voltage Transformer DAPPER Distribution Analysis For Power Planning, Evaluation and Reporting DBA Design Base Accident DC-Direct Current DCP Design Change Package D/G Diesel Generator EC-Engineerina Calculation EDG-Emergency 61esel Generators EDS Electrical Distribution System ESF Engineered Safety Features F
Fahrenheit FSAR Final Safety Analysis Report GE General Electric HP Horse Power HPCS High Pressure Core Spray HVAC Heating, Ventilation and Air Conditioning Hz Hertz IEEE Institute of Electrical and Electronics Engineers kA Kiloamperes kV Kilovolts kVA Kilovoltampere kW Kilowatts LC Load Centers a
LOCA Loss of Coolant Accident LOP Loss of Offsite Power LPCS Low Pressure Core Spray LSS Load Shedding and Sequencer MCC Motor Control Center-MNCR Material Non-Conformance Report NPE Nuclear Plant Engineering p.u.
per unit PR ProtectiveRelay(s)
P&SE Performance and System Engineering QDR Quality Deficiency Report RHR Residual Heat Removal SCRI System Energy Resources. Inc.
SSFA Safety System functional Assessment SSW Standby Service Water TS Technical Specifications TSTI Technical Special Test Instructions UFSAR Updated Final Safety Analysis Report B-1
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UL Underwriters Laboratories UPS Uninterruptible Power Supply USNRC United States Nuclear Regulatory Coninission V
Volt (s)
VtC Volts Alternating Current
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VDC Volts Direct Current
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APPENDlX C 1.
Persons Contacted Licensee Employees
- C. P. Angle - Operational Analysis Section (0AS)
- T. Barnett - Nucitar Plant Engineering (NEP) Electrical Systen:s
- W. T. Cottle - Vice President. Operations
- M. A. Dietrich - Director. Quality Progran's
- J. P. Dimmette, Jr., - Manager, Plant Maintenance
- W. C. Eiff - Quality Engineering
- R. Green - System Engineering
- M. Humphries - Supervisor System Engineering
- C. R. Hutchinson - General Manager, GGNS
- A. Khanifar - HPE
- H. Kook - Nuclear Licensing
- M. A Krupa - Superintendent, System Engineering
- M. J. Meisner - Director, Nuclear Licensing
- 0. Ogerly - Materials Technology
- J. V. Parrish - Manager, Operations
- 0. Pace - Manager, NPE
- B. Parman - Systems Engineer
- L. Patterson - NPE
- L. Phillips - NPE
- J. C. Roberts - Manager - Performance and System Engineering (PASE)
- R. P. Rose - PASE
- f. W. Titus - Director - NPE
- W. White - NPE
- G. A. Zin6e - Superintendent, Plant Licensing Other Organizations
- J. MacGregor, Winston and Strawn NRC Resident inspectors
- J. Mathis Attended exit interview.
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