ML20030C967
| ML20030C967 | |
| Person / Time | |
|---|---|
| Site: | Indian Point  |
| Issue date: | 07/31/1981 |
| From: | Weber D EG&G, INC. |
| To: | Shemanski P Office of Nuclear Reactor Regulation |
| References | |
| CON-FIN-A-6429 EGG-EA-5491, NUDOCS 8108280508 | |
| Download: ML20030C967 (13) | |
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ef 4/d EGG-EA-5491 JULY 1981 ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES, j-INDIAN POINT NUCLEAR POWER STATION--UNIT NO. 3,
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This is an informal report intended for use as a preliminary or working document i
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U.S. Nuclear Regulatory Comission b O E b idaho Under DOE Contract No. DE-AC07-76ID01570 Q
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7.7ds" INTERIM REPORT Accession No.
Report No. EGG-EA-5491 Contract Program or Project
Title:
Selected Operating Reactors Issues Program (III)
Subject of this Document:
Adequacy of Station Electric Distribution System Voltages, Indian Point Nuclear Power Station - Unit No. 3, Docket No. 50-286 Type of Document:
Technica Evaluation Report Author (s):
J E Resea d W h M d o ^ webar
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Date of Document:
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July 1981 Responsible NRC Individual and NRC Office or Division:
Paul C. Shemc.nski, Division of Licensing This document was prepared primarily for preliminary or internal use. it has r'ot received full review and approvel. Since there may be 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.
o Under DCI Contract No. DE-AC07 76tD015'70 NRC FIN No.
A6429 INTERIM REPORT I
0472J ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES INDIAN POINT NUCLEAR POWER STATION--UNIT NO. 3 Docket No. 50-286 July 1981 D. A. Weber Reliability and Statistics Branch Engineering Analysis Division EG&G Idaho, Inc.
i N;1C Research anc "echnical N Assistance. Report TAC No. 12993
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l 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 i' the onsite distribution system, in conjunction with the offsite power sources, has sufficient capacity and capability to automatically start and operate all required safety loads within the equipment voltage ratings.
This Tecnnical Evaluation Report reviews the submittals for the Indian Point Unit 3 Nuclear Power Station.
The onsite distribution system, in conjunction with the offsite power sources, has been shown to have sufficient capacity and capability to oper-ate all required safety related loads, within the equipment rated voltage limits, in the event of either an anticipated transient or an. accident condition for the analyzed offsite sources. However, analysis has not been provided for other possible offsite sources supplying the onsite distribu-tion system, or for any of the offsite sources supplying more than one unit tnrough unit tie breaker (s).
COREWORD 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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CONTINIS
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 E V AL U A T I O N......................................................
4
6.0 CONCLUSION
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7
7.0 REFERENCES
8 FIGURE-l.
Indian Point Unit 3 electrical single-line diagram..............
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TABLE 1.
Class lE equipment voltage ratings and analyzed worst case terminal voltages....................................
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{RC,7esearci anc Technica' l.
' Assistance lepori l
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ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES INDIAN POINT NUCLEAR STATION--UNIT NO. 3
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 of August 8, 1979, " Adequacy of Station Electric Distribution Systems volt-ages,"I required each licensee to confirm, by analysis, the adequacy of the voltage at the class lE 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.
In res-ponse to the NRC generic letter, the Power Authority of the State of New York (PASNY) submitted a voltage analysis on May 30, 1980.2 This review is based on this submittal, PASNY's submittals of February 11, 1980,3, June 12,1981,4 and the Final Safety Analysis Report (FSAR) for Unit 3.
Based on the information supplied by PASNY, this report addresses the capacity and capability of the onsite distribution system of the Indian Point Nuclear Power Station Unit 3, in conjunction with the offsite power system, to maintain the voltage for the required class lE equipment within acceptable limits for the worst-case starting and load conditions.
2.0 DESIGN BASIS CRITERIA The positions applied in determining the acceptability of the offsite voltage conditions in supplying power to the class lE equipment are derived from the following:
l.
General Design Criterion 17 (GDC 17), " Electrical Power Systems," of Appendir. A, " General Design Criteria for Nuclear Power Plants," of 10 CFR 50.
2.
General Design Criterion 5 (GDC 5), " Sharing of Struc-tures, Sys* ems, and Components," of Appendix A, " Gen-eral Design Criteria for Nuclear Power Plants," of 10 CFR 50.
3.
General Design Criterion 13 (GDC 13), " Instrumentation and Cor trol," of Appendix A, " General Design Criteria f or Nuclear Power Plants," of 10 CFR 50.
4.
IEEE Standard 308-1974, " Class lE Power Systems for Nuclear Power Generating Stations."
5.
Staffpositionsasdetailedinjlettersenttothe licensee, dated August 8, 1979.
I NRC Researc1 anc "ecmica x Assistance Report-1
6.
ANSI C84.1-1977, " Voltage Ratings for Electric Power Systems and Equipment (60 Hz)."
jixreviewpositionshavebeenestablishedfromtheNRCanalysisguide-lines and the above-listed documents.
These positions are stated in
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Section 5.0.
3.0 SYSTEM DESCRIPTION A single-line diagram of the'AC electrical system at Indian Point 3 is shown in' Figure 1.
During normal operation, the 6.9 kV buses 1, 2, 3, and 4 and the 480V IE buses 2A and 3A are supplied from the 22kV Unit Auxiliary Transformer (UAT).
The 6.9kV buses 5 and 6 and the 480V buses 5A and 6A are supplied from the 138kV normal offsite source via the Station Auxiliary Transformer (SAT). The 6.9kV and 480V buses normally supplied from the UAT will auto-matically f ast transfer to the SAT should the reactor or turbine trip.
In addition to the 138kV normal offsite source, the loads on the 6.9kV buses 5 and 6 and IE buses SA and 6A can be supplied from the 138/13.8kV Bucnanan tie via the 13.8/6.9kV transformer.
These buses can also be sup-plied from a 13.8kV gas turbine generator via the 13.8/6.9kV transformer.
This transformer can also supply the Unit 2 loads via a Unit 2/ Unit 3 tie breaker. This also holds true for the Unit 2-13.8/6.9kV transformer.
The Technical Specifications require that the lE 480V bus inter-ties must be open when Unit 3 is operating.
The IE 480V buses supply two 120V AC battery chargers and four instru-mentation buses in addition to their normal load.
The two battery chargers maintain voltage on the two 125V DC battery systems in addition to supplying the normal DC loads. Two of the instrumentation buses are energized through constant voltage transformers and the other through station inter-ties.
I' 4.0 ANALYSIS DESCRIPTION 4.1 Analysis Conditions.
PASNY has determined by load flow analysis that the maximum expected offsite grid voltage is 145.7kV for the 138kV system and the minimum 13.7kV for the 13.8kV system.
PASNY has analyzed two offsite sources (the 138kV and the 13.8kV sources) to the onsite distribution system under extremer of load and off-site voltage conditions to determine the terminal voltages to IE equipment.
The worst case lE equipment terminal voltages occur under the following conditions:
1.
The maximum voltage occurs when the offsite 138kV grid is at its maximum expected value of 145.7kV and no load on the station' buses.
2.
The minimum voltage occurs when the offsite 13.8kV system is at its minimum. expected value of 13.7kV; the
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3.
The worst case transient voltages occur when starting the 900 hp Circulating Water Pump and the 13.8kV system is at its minimum value and supplying maximum loads.
4.2 Analysis Result.
Table 1 shows the projected worst case class lE equipment terminal voltages.
4.3 Analysis Verification. PASNY has stated that current and voltage measurements will be obtained from the 480V 1E buses 2A, 3A, 5A, and 6A or, a sample basis during normal plant operations. Measurements will'also include motor starting and running values. Motors which cannot be safely operated during normal plant operations will be operated on a sample basis during the 1981 refueling outage. The expected auxiliary plant load during the normal plant operation is estimated at 37 megawatts.
The test values will be used as computer input data and the computed values will be compared with the test values to verify the accuracy of the analysis.4 1
5.0 EVALUATION
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lines {ix review positions have been established from the NRC analysis guide-and the documents listed in Section 2.0 of this report. Each review position is stated below followed by an evaluation of the licensee submittals. The evaluations are based on completion of changes described in Section 4.1.
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 operatirg all class IE equipment within the equipment voltage ratings.
PASNY has shown, by analysis, that the 138kV and 13.8kV systems have sufficient capability and capacity for starting and continuously operating the class lE loads within the equipment voltage ratings (Table 1).
l Transient values for the 480V starters were not provided, but are expected l
to be above the minimum pick-up and drop-out values.
In addition, PASNY has not provided analysis showing the capability and capacity of the 13.8kV system to supply all Unit 3 and Unit 2 loads through a Unit 3/ Unit 2 tie breaker. There are no interlocks or limiting conditions of operation included in the plant Technical Specifications that prevent the use of the i
tie during operation of either plant.
Additionally, the Technical Specific'ations contain no limiting condi-tions to prevent the use of one or more gas turbine generators (GTs) from supplying all required lE 480V loads via the 13.8/6.9kV transformer. PASNY has not provided an analysis to demonstrate that the GTs are capable of starting and of continuously operating all required lE equipment within the i
equipment voltage rating to either Unit 3 or both units via the Unit 3/
Unit 2 tie breaker.
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TABLE 1.
CLASS 1E EQUIPMENT VOLTAGE RATINGS AND ANALYZED WORST CASE TERMINAL VOLTAGES (% of nominal voltage) a b
Maximum
- Minimum Analyzed e
Equipment Condition Rated Analyzed Rated Steady State Transient 440V Motors Start 80 82.27e Operate 110 ll2d 90 92.5 460V Motors Start 80 84.780 Operate 110 107 90 93.9 480V Startersf Pickup 85 Dropout 60 Operate 110 103 90 90 Other Equipment 9 a.
138kV source: maximum analyzed = 105.6%.
b.
13.8kV source: minimum analyzed = 99.27%
c.
Licensee did not provide transient values for the start of a large Non-1" load. However they analyzed the start of the 900 hp Circulating Water Pumps and stated that "the starting of one of these pumps would cause voltages to drop several percent for approximately two (2) seconds, during which time voltages at all equipment would remain above minimum levels required."4 d.
As load is applied, the voltage will decay to acceptable levels.
e.
These values are for individual 440V or 460V motors with the lowest starting voltage under conditions of minimum grid and bus voltage.2 j
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Transient voltages not supplied for the load centers and MCC buses.
g.
Analyzed voltages are within the operating range of the 480V battery chargers.
Instrument buses are supplied by inverters fr batteries and are unaffected by any offsite occurrences.gm 125V DC l
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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 IE equipment without exceeding the equipment voltage ratings.
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PASNY has shown, by analysis, that the voltage ratings of the IE equip-ment will not be exceeded.
Position 3--Loss of offsite power to either of the redundant class lE distribution systems, due to operation of voltage protection relays, must not occur when the offsite power source is within expected voltage limits.
EG&G Idaho, Inc., will verify, in a separate report, that the require-ments of this position are satisfied (TAC No.10029).
Position 4--The NRC letterI requires that test results verify the accuracy of the voltage analyses supplied.
PASNY has provided a test description 4 but did not state when the test results would be available. The proposed test is acceptable if the test values used are obtained when each of the lE buses are loaded to at least 30% of rated load. Measurements should also be obtained at the MLC buses 36A and 368. These buses were not included in their test description.
In addition, the test results should include an analysis of the capability of the 480V motor starters to pick up due to the start of a 460V or 440V motor with tne lowest starting motor terminal voltage, and not to drop out due to the start of a large IE load under conditions of minimum grid and maximum load. These transient values were not proviaed in the original analysis. See Table 1.
Position 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 I?).
PASNY has analyzed the 138kV and 13.8kV connections to the offsite power grid, and 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 supplying adequate starting and operating voltage for all required class IE loads with an accident in one unit and an orderly shutdown and cooldown in the remaining units.
Indian Point is the site of two operating nuclear units. The preferred (138kV) and alternate (13.8kV) offsite sources are independently connected to the onsite distribution system of each unit.
However, the alternate offsite source of each unit can simultaneously supply lE loads of the other unit through a tie breaker. PASNY has not provided an analysis for this connection. Additionally, the Indian Point Station has three gas turbine generators that could supply power to class lE loads individually or in combination to one unit or both units through the tie breaker. No voltage analysis fo.' this supply has been provided to the NRC.
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EG&G Idaho, Inc., is performing a separate review of the undervoltage relay protection at the Indian Point Nuclear Station Unit 3.
This will evaluate the relay setpoints and time delays to determine that spurious tripping of'the class lE buses will not occur with normal offsite source voltages.
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.
l l
2.
PASNY letter, P. J. Early, to Director of Nuclear Reactor Regulation, 4
May 30, 1980.
1 3.
PASNY letter, P. J. Early, to W. Gammill, U.S. Nuclear Regulatory Commission, February 11, 1980.
i 4.
PASNY letter, J. P. Bayne, to Director of Nuclear Reactor Regulation, June 12, 1981.
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