ML20031F439
| ML20031F439 | |
| Person / Time | |
|---|---|
| Site: | Oyster Creek |
| Issue date: | 08/31/1981 |
| From: | Weber D EG&G, INC. |
| To: | Shemanski P Office of Nuclear Reactor Regulation |
| References | |
| CON-FIN-A-6429 EGG-EA-5475, NUDOCS 8110190839 | |
| Download: ML20031F439 (12) | |
Text
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EGG-EA-5475 i
AUGUST 1981 ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM 4, M ans VOLTAGES, 0YSTER CREEK NUCLEAR POWER STATION, ggf(
D9CKET NO. 50-219 M
h[illdlfb D. A. Weber 4
NRC Researc, anc Tec1nica
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Assistance Report s "%d,.gg n
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Idaho Operations Office
- Idaho National Engineering Laboratory
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This is an informal report intended for use as a preliminary or working document 2
Prepared for the U.S. Nuclear Regulatory Comraission g
Under DOE Contract No. DE-AC07-76ID01570 E S E 6 :daho Yk FIN No. A6429 8110190839 810831 l
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INTERIM REPORT Accession No.
Report No.
EGG-EA-5475 Contract Program or Project
Title:
Selected Operating Reactor Issues Program (III)
Subject of this Document:
Adequacy of Station Electric Distribution System Voltages, Oyster Creek Nuclear Power Station, Docket No. 50-219 rype of Document:
Technical Evaluation Report Author (s):
NRC Researc1 anc "ecanical D. A. Weber Assis:ance Report D:te of Document:
August 1981 Responsible NRC Individual and NRC Office or Division:
P. C. Shemanski, Division of Licensing This document was prepared primarily for preliminary or internal use. it has not received full review and approval. Since there may oe substantive changes, this document should not be considered final.
EG&G Idaho, Inc.
Idaho Falls, Idaho 83415 Prepared for the U.S. Nuclear Regulatory Commission Washington, D.C.
Under DOE Contract No. DE AC07 761D01570 NRC FIN No. A6429 INTERIM REPORT
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0431J ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES OYSTER CREEK NUCLEAR POWER STATION Docket No. 50-219 4
August 1981 r
D. A. Weber Reliability and Statistics Branch I
Engineering Analysis Divisien
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EG&G Idaho, Inc.
i NRC Researc1 and k'inica Assistance Repor:
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ABSTRACT The Nuclear Regulatory Commission has required all licensees to analyze the electric power system at each. nuclear station.
This review is to deter-mine if the onsite distribution system, in conjunction with the offsite l
power sturres, has sufficient capacity and capability to automatically start and optrace all required safety loads within the equipment voltage ratings.
This Technical Evaluation Report reviews the submittals for the.0yster Creek Nuclear Power Station.
t The onsite distribution system in conjunction with the offsite power sources has, with voltage regulation, sufficient capacity and capability to continuously operate all required safety-related loads within the equipment-l rated voltage limits in the event of either an anticipated transient or an accident condition. Certain 460 V motor starters and 480 V safety-related motors could operate below their minimum allowable voltage and some 440 V motors could be operated in excess of their maximum allowable rating with-out voltage regulation.
FOREWORD 2
This report is supplied as part of the " Selected Operating Reactor Issues Program (III)" being conducted for the U.S. Nuclear Regulatory Commission, Office of Nuclear Reactor Regulation, Division of Licensing, by EG&G Idaho, Inc., Reliability and Statistics Branch.
The U.S. Nuclear Regulatory Commission funded the work under the authorization, B&R 20 19 01 06, FIN No. A6429.
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CONTENTS
1.0 INTRODUCTION
1 2.0 DESIGN BASIS CRITERIA...........................................
1 3.0 SYSTEM DESCRIPTION..............................................
2 4.0 ANALYSIS DESCRIPTION............................................
2 4.1 Analysis Conditions.......................................
2.
4.2 Analysis Results..........................................
4 4.3 Analysis Verification.....................................
4 5.0 EVALUATION......................................................
4
6.0 CONCLUSION
S.....................................................
6
7.0 REFERENCES
7 FIGURE 1.
Oyster Creek electrical single-line diagram.....................
3 TABLES 1.
Class IE Equipment Voltage Ratings and Analyzed Worst-Case Load Terminal Voltages......................
5 i
2.
Comparison of Analyzed Voltages and Undervoltage Relay Setpoints....................................
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ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES OYSTER CREEK NUCLEAR POWER STATION
1.0 INTRODUCTION
An event at the Arkansas Nuclear One station on September 16, 1978 is described in NRC IE Information Notice No. 79-04. As a result of this event, station conformance to General Design Criteria (GDC) 17 is being questioned at all nuclear power stations. The NRC, in the generic letter ofAugugt8,1979,"AdequacyofStationElectricDistributionSystemsVolt-ages,"
required each licensee to confirm, by analysis, the adequacy of the voltage at the class IE loads. This letter included 13 specific guide-lines to be followed in determining if the load terminal voltage is adequate to start and continuously operate the class lE loads.
TheJerseyCentralPowgrandLightCompany(JCP&L)respondedtothis letter on November 1, 41979.
This submittal, submittals of November 5, 1976,3 April 18, 1977, September 25 1979,5 November 1, 1979,6 August 11, 1980,7 April 30, 1981,8, a,nd the Final Safety Analysis Report (FSAR) complete the information reviewed for the report.
Based on the information supplied by JCP&L, this report addresses the capacity and capability of the onsite distribution system of the Oyster Creek Nuclear Power Station, in conjunction with the offsite power system, to maintain the voltage for the required class lE equipment within accep-table limits for the worst-case starting and load conditions.
2.0 DESIGN BASIS CRITERIA The positions applied in determining the acceptability of the off site voltage conditions in supplying power to the class 1E equipment are derived from the following:
1.
General Design Criterion 17 (GDC 17), " Electrical Power Systems,"
of Appendix A, " General Design Criteria for Nuclear Power Plants,"
of 10 CFR 50, 2.
General Design Criterion 5 (GDC 5), " Sharing of Structures, Sys-tems, and Components," of Appendix A, " General Design Criteria for Nuclear Power Plants," of 10 CFR 50.
3.
General Design Criterion 13 (GDC 13), " Instrumentation and Con-trol," of Appendix A, " General Design Criteria for Nuclear Power Plants," of 10 CFR 50.
4.
IEEE Standard 308-1974, " Class lE Power Systems for Nuclear Power Generating Stations."
5.
Staff positions as detailed in a letter sent to the licensee, dated August 8, 1979.1 1
6.
ANSI C84.1-1977, " Voltage Ratings for Electric Power Systems and Equipment (60 Hz)."
Six review positions have been established from the NRC analysis guide-linesl and the above-listed documents. These positions are stated in Section 5.0.
3.0 SYSTEM DESCRIPTION Figure 1 is a sketch of the Oyster Creek single line diagram of the unit electrical distribution system.
During normal full-power plant operations, the Oyster Creek main gener-ator supplies all onsite loads through the single 24/4.16kV Station Auxil-4 iary Transformer (SAT) which supplies four 4160 V buses lA, 1B, 1C, and ID (lC and 10 are safety-related). Should this source of power become unavail-able the loads on these buses will automatically fast transfer to the Start-up Transformers (ST) A and B (buses lA and 1C will transfer to ST-A and buses 18 and ID to ST-8).
Each 34.5/4.16kV ST can be supplied from the 34.5kV offsite distribution system or from the 230kV grid via a 230/24.5kV j
transformer. Voltage regulators installed on the 34.5kV system will main-tain the 4160V bus voltage between 4100V and 4210V when the 230kV grid is between 214.82kV and 242kV.
The emergency 4160V buses 1C and 10 supply power to station loads important to plant safety and vital to safe shutdown under accident conditions. Each bus supplies three 480V unit substations which in turn supply: medium sized electrical loads; 460V motor control centers (MCC's) i including the vital MCCs and stepdown transformers (460/120-208) for light-ing, instrumentation and plant service loads.
During normal plant opera-tion the tie breakers between the 4160V switchgear.lC and 10 are normally open and the breakers between the unit substations are racked out.
Tnere are three 125V DC systems (DC-A, 8, and C) which supply redun-dant DC control power to the switchgear and unit substations in addition to other DC loads. Each 125V DC system is supported from its own single 60 cell battery system, and solid state battery chargers or M-G sets.
d.0 ANALYSIS DESCRIPTION I
4.1 Analysis Conditions. JCP&L has determined by stability analysis that the maximum expected offsite grid voltage is 242kV and the minimum is 214.82.8 JCP&L has analyzed each offsite source to the onsite distribution sys-tem under extremes of loao and offsite voltage conditions, with and without-the 34.5kV voltage regulators, to determine the terminal voltages to lE equipment. This report considers the distribution system with and without~
the voltage regulators. The worst-case class lE equipment terminal voltages occur under the following conditions:
Maximum voltage occurs when the offsite gria is at the highest analyzed value and the plant is shutdown and operating only minimum loads.
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d ;ii Figure 1.
Oyster Creek Nuclear Po.wer Station eletrical distribution ao h
system single-line diagram.
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The minimum steady-state voltage occurs when the offsite grid is at its minimum analyzed value and all normal and LOCA loads are running as well as the reactor feed pumps.
The minimum transient voltage occurs as in the minimum voltage condi-tions above accept for the start of a reactor feed pump. The longest time required for any large motor to accelerate voltageatitsterminals,issevenseconds.gorunningspeed,withrated 4.2 Analysis Result. Table 1 shows the projected worst case class lE equipment terminal voltages without voltage regulation. Table 2 shows a comparison of the undervoltage relay setpoints with the analyzed voltages.
4.3 Analysis Verification.
In order to verify their computer analysis, CP&L conducted a test on July 23, 19808 at.the Oyster Creek Plant. Using the existing grid voltage at the time of the test, a computer run was made to predict voltage levels at the 4160, 480, and 120V levels.
These predicted values were then compared to actual readings taken at the Oyster Creek Station. Bus and transformer loading conditions during the test ranged from 39% to 100%.8 5.0 EVALUATION guidelinesyview positions have been established from the NRC analysis Six r end the documents listed in Section 2.0 of this report. Each review position is stated below followed by an evaluation of the licensee.
submittals.
Position 1--With the minimum expected offsite grid voltage and maximum load condition, each offsite source and distribution system connection combination must be capable of starting and of continuously operating all class lE equipment within the equipment voltage ratings.
This position is not satisfied without voltage regulation, as certain 460'l motor ' starters and the 480V motors would be required to operate at a voltage below the minimum ratings (Table 1).
Position 2--With the maximum expected offsite grid voltage and minimum load condition, each offsite source and distribution system connection combination must be capable of continuously operating the required class lE equipment without exceeding the equipment voltage ratings.
This position is not satisfied without voltage regulation, as some of the 440V motors would have voltage in excess of maximum rating. Maximum voltages on equipment with ll5V nominal rating not provided.
Position 3--Loss of offsite power to either of the redundant class lE distribution synems, due to operation of voltage protection relays, must not occur when the offsite power source is within expected voltage limits.
This position is not satisfied as the second-level undervoltage relays could operate if the grid is 'at or slightly above its minimum analayzed value (Table 2).
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TABLE 1.
CLASS lE EQUIPMENT VOLTAGE RATINGS AND ANALYZED WORST-CASE TERMINAL VOLTAGES WITHOUT VOLTAGE REGULATION
(% of r.ominal voltage) a b
Maximum Minimum Analyzed Equipment Condition Rated Analyzed Rated Steady State Transient 4000V Motors Start 80 89 Operate 110 110 90 91.6 480V Motors Start 85 78 Operate 110 105' 86.6c 85 460V Motors Pickup 85 83 Operate 110 110 86.6c 87.5 440V Motors Start 85 77 Operate 110 115 86.6c 90.5 460V Starters Pickup 85 85.7 Oropout 60 85.7 Operate 110
.110 90 88.5
' 90 Other Equipment Rated 110
<i10 90 100.8 ll5V a.
Maximum values based on Table 1 and 2 of the November 1,1979 submit-tal,6 adjusted for a' maximum grid value of 242kV and no allowance for voltage drop between load centers and motor control centers or the motor feeder cables.
b.
Minimum values based on Table 2 and 3 of the August 11, 1980 submittal 7 adjusted for the minimum analyzed grid voltage of 214.82kV (3671V at the 4160V 1E buses),
Worst-case safety-related motors have a'1.15 service factor.9 c.
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TABLE 2.
COMPARISON OF ANALYZED VOLTAGES AND UNDERVOLTAGE RELAY SETPOINTS (without voltage regulation) a Minimum Analyzed Relay Setpoint
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Location / Relays Voltage Time Voltage (Tolerance)
Time 4160V busa Degraded grid 3671V cont.
3671V + 1%
10 sec + 0.1%
Loss of grid 3594 7 sec 2864V -
3 sec _T 0.5%
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a.
Licensee has determined by analysis the minimum bus voltages with the offsite grid at the minimum expected voltage and the worst-case plant and
- . lass lE loads.
Position 4--The NRC letterl requires that test results verify the accuracy of the voltage analyses supplied.
4 A review of JCP&L test procedure and results indicate that the analysis is satisfactory. The test result shows that the largest difference between the measured and computed values is +1%.
Fosition 5--No event or condition should result in the simultaneous or consequential loss of both required circuits from the offsite power network to the onsite distribution system (GDC 17).
JCP&L has analyzed the Oyster Creek Nuclear Power Station connections to the offsite power grid, and have determined that no potential exists for simultaneous or consequential loss of both circuits from the offsite grid.
Position 6--As required by GDC 5, each offsite source shared between units in a multi-unit station must be capable of supplyin? adequate start-ing and operating voltage for all required class lE loads with an accident
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in one unit and an orderly shutdown and cooldown in the remaining units.
This applies to multi-unit plcnts.
It does not apply to the Oyster Creek single-unit station.
6.0 CONCLUSION
S The voltage analyses submitted by JCP&L for the Oyster Creek Nuclear Power Station were evaluated in Section 5.0 of this report.
It was found i
that:
l.
With voltage regulation, voltages within the operating limits of the class lE equipment are supplied for all projecte,d combinations of plant load and offsite power grid conditions. Without regula-l tion, voltages to certain class lE loads are unsatisfactory.
l 2.
The test used to verify the analysis shows the analyses to be an accurate representation of the worst case conditions analyzed.
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T 3.
JCP&L has determined that no potential for either a simultanous or consequential loss of both offsite power sources exists.
4.
Loss of offsite power to class lE bus'es, due to spurious operation of voltage protection relays, should not occur with the offsite i
grid voltage within its expected limits and the 34.5 voltage regulators in operation. Without the cegulators, spurious trip-ping could occur.
As a result of their original analysis JCP&L has installed voltage regulators on the 34.5kV grid, which maintain the 4160V bus between 4100V and 4210V for extremes of normal offsite grid voltages. These voltage regu-lators will maintain all safety-related equipment within their operating limits and prevent spurious separation of class 1E buses from the offsite power sources. However, credit for these regulators is dependent upon inclusion of limiting condition of operation requirements in the plant technical specifications.
7.0 REFERENCES
1.
NRC letter, William Gammill, to All Power Reactor Licensees (Except Humboldt Bay), " Adequacy of Station Electric Distribution Systems Voltage," August 8, 1979.
2.
JCP&L letter, I. R. Finfrock, Jr. to Director of Nuclear Reactor Regulation November 1, 1979.
3.
JCP&L letter, I. R. Finfrock to George Lear, Chief, Division of
)
Operating Reactors, branch No. 3, Nuclear Regulatory Commission, November 5, 1976.
4.
JCP&L letter, I. R. Finfrock to George Lear, Chief, Division of Operat-ing Reactors, Branch No. 3, Nuclear Regulatory Commission, April 18, 1977.
5.
JCP&L letter, I. R. Finfrock to Director of Nuclear Reactor Regulation, September 25, 1979.
6.
JCF&L letter, I. R. Finfrock to Director of Nuclear Reactor Regulation, i
November 1, 1979.
7.
JCP&L letter, I. R. Finfrock to Director of Nuclear Reactor Regulation, August 11, 1980.
8.
JCP&L letter, I. R. Finfrock to Director of Nuclear Reactor Regulation, April 30, 1981.
9.
Telcon, P. Wells, JCP&L, O. Weber, EG&G Idaho, Inc., May 29, 1981.
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