ML20052C928
| ML20052C928 | |
| Person / Time | |
|---|---|
| Site: | Monticello  |
| Issue date: | 02/28/1982 |
| From: | Weber D EG&G, INC. |
| To: | Prevatte R Office of Nuclear Reactor Regulation |
| References | |
| CON-FIN-A-6429 EGG-EA-5783, EGG-EA-5783-01, EGG-EA-5783-1, NUDOCS 8205060112 | |
| Download: ML20052C928 (12) | |
Text
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VOLTAGES, MONTICELLO NUCLEAR GENERATING PLANT, UNIT 1 f)6/G A)TIG Of I =
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, This is an informal report intended for use as a preliminary or working document l l
Prepared for the U. S. Nuclear Regulatory Commission Under DOE Contract No. DE-AC07-761D01570 FIN No. A6429 :
8205060112 820228 PDR RES 8205060112 PDR
hEGsGo~...e FORM EG4G 396 (Rev ti e t)
INTERIM REPORT Accession No. :
Report No. EGG-EA-5783 Contract Program or Project
Title:
Selected Operating Reactors Issues Program (III)
Subject of this Document:
Adequacy of Station Electric Distribution System Voltages, Monticello Nuclear Generating Plant, Unit 1 ,
Type of Document:
Informal Report Author (s):
D. A. Weber Date of Document:
February 1982 J
Responsible NRCIDOE Individual and NRC/ DOE Office or Division:
R. L. Prevatte, Division of Systems Integration, NRC This document was prepared primarily for preliminary orinternal use. It has not received full review and approval. 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.
Under DOE Contract No. DE-AC07-761D01570 ,
s NRC FIN No. A6429 c
INTERIM REPORT
0387J ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES MONTICELLO NUCLEAR GENERATING PLANT, UNIT 1 Docket No. 50-263 February 1982 D. A. Weber Reliability and Statistics Branch Engineering Analysis Division EG&G idaho, Inc.
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l ABSTRACT
\
This report contains the EG&G Idaho, Inc. evaluation of the adequacy of the station IE electrical distribution system voltages for the -
Monticello Nuclear Generating Plant, Unit 1.
FOREWORD i
This report is supplied as part of the " Selected Operating Reactors Issues Program (III)" being conducted for the U.S. Nuclear Regulatory l 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.
ii
CONTENTS 1
1.0 INTRODUCTION
2.0 DESIGN BASIS CRITERIA ........................................... 1 3.0 SYSTEM DESCRIPTION .............................................. 2 4.0 ANALYSIS DESCRIPTION ............................................ 2 41 Design / Operation Changes .................................. 2 4.2 Analysis Conditions ....................................... 2 4
4.3 Analysis Results ..........................................
4 4.4 Analysis Verification .....................................
5
. 5.0 EVALUATION ......................................................
6.0 CONCLUSION
S ..................................................... 6
7.0 REFERENCES
...................................................... 6 FIGURE
- 1. Monticello electrical single-line diagram ....................... 3 4
1 TABLES
- 1. Class lE Equipment Voltage Ratings and Analyzed Worst Case Load Terminal Voltages ...................... 4
- 2. Comparison of Analyzed Voltages and Unde'. voltage Relay Setpoints .................................... 5 e
d t
- iii I
i t
ADEQUACY OF STATION ELECTRIC DISTRIBUTION SYSTEM VOLTAGES MONTICELLO NUCLEAR GENERATING PLANT, UNIT 1
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 V ol tages ," required each licensee to confirm, by analysis, the adequacy
- of the voltage at the Class lE loads. This letter in-luded 13 specific guidelines to be followed in determining if the load terminal voltage is adequate to start and continuously operate the Class lE loads.
In response to the generic letter and questions from the staff, NorthernStatesPgwerCompany(NSP)submittedinformationandanalysison January 30, 1981, June 25, 1981,3 and November 2, 1981.4 These sub-mi'tals, submittals of March 4, 1977,5, July 25, 1977,6 October 14 1977,7 April 21, 1978,8 O May 1980,10 August 4 '
December 16,1981,gober31,1979,922,1981,g, September February 5, 1982,15 the EG&
Idaho Inc., report on the Monticello degraded grid protection dated August 1980,f2 and the Monticello Final Safety Analysis Report completes the information reviewed for this report.
Based on the information supplied by NSP, this report addresses the capacity and capability of the onsite distribution system of the Monticello Nuclear Power Station, 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:
- 1. General Design Criterion 17 (GDC 17), " Electrical Power Systems,"
of Appendix A, " General Design Criteria for Nuclear Power Plcnts,"
of 10 CFR 50.
- 2. General Design Criterion 5 (GDC 5), " Sharing of Structures, Sys-tems, and Components," of Appendix A, "Geaeral Design Criteria fo- Nuclear Power Plants," of 10 CFR 50.
- 3. General Design Criterion 13 (GDC 13), " Instrumentation and Con-trol," of Appendix A, " Genera l Design Criteria for Nuclear Power Plants," of 10 CFR 50.
4 IEEE Standard 308-1974, " Class lE Power Systems for Nuclear Power Generating Stations."
1
- 5. Staff positions as detailed in a letter sent to the licensee, dated August 8, 1979.I
- 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 guidelinesl and the above-listed documents. These positions are stated in Section 5.0.
3.0 SYSTEM DESCRIPTION Figure 1 of this report is a simplified sketch of the Monticello elec- )
trical single-line diagram. , i During normal plant full-power operation, auxiliary power is supplied -
by the Unit Auxiliary Transformer (UAT) No.11 and, during startup and shutdown, by the Startup Auxiliary Transformer (SAT) No. IR. Provisions )
are made for automatic, fast transfer of the auxiliary loads from the UAT to the SAT upon unit trip. Inability of the SAT to supply power will cau an automatic transfer to the Reserve Auxiliary Transformer (RAT) No. lAR.pe Complete loss of all offsite power will result in the diesel generators supplying all the shutdown loads. The UAT and SAT each have the capacity to carry full plant loads. The RAT and the diesel generators have the capacity to supply all safety-related loads (all non-essential loads are automaticallyshed).
There are two essential 4.16kV buses; No.15 and 16. One division of safety-related equipment is powered from each of these buses. Each bus supplies 4.16kV loads, the 480V load centers and motor control centers (MCCs), and the 250V dc, 125V dc, and 24V dc systems.
The FSAR and Reference 2 provide a detailed description of operation of the Class lE AC and DC systems.
4.0 ANALYSIS DESCRIPTION 4.1 Design / Operation Cnanges. The voltages shown on Table I are based on the modifications,4 changes, and analysis described in the NSP letter of November 2, 1981.
4.2 Analysis Conditions. NSP has determined through review of his-torical data that the maximum offsite grid voltage of 354kV (1.026 pu) will result in the highest offsite voltages when the RAT is supplying the lE system. Load flow studies have determined that the minimum offsite grid voltage of Il9kV (1.038 pu) will result in the lowest onsite voltages when the SAT is supplying the lE system.
NSP has analyzed each offsite source to the onsite distribution system .
under extremes of load and offsite voltage conditions to determine the 2
To 345 KV Grid To 345/115 KV Grid To 115 KV Grid r !
Gen.
- Trans.
mm 22/345 KV j l)b W I' i
Main Trans. 11 Trans. lAR Trans. 1R Generator W W (UAT) w W (RAT) hv (SAT)
&m mm mm m mm
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.._.L_____l__. 1)_ _. 1 > - I 4160V Bus li 4160V Bus 12 '
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4160V Bus 13 _. 4160V Bus 14_. I l I
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1E 4160V Bus 15 i i ) i l lE 4160V !
Bus 16 i
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RHR O CPumps re Spray 0 (-
' ' " ' " (
RH'fi Loads Loads l
)
480V i Load Centers 480V I
Load Centers
.3 480V ,) MCC's 480V ) MCC's l
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i l Figure 1. Monticello Electrical Single-Line Diagram 3
l l
l
TABLE 1. CLASS lE EQUIPMENT VOLTAGE RATINGS AND ANALYZED WORST CASE TERMINAL VOLTAGES (% of nominal voltage)
Maximum Minimum Analyzed 4
_ Equipment Condition Rated Analyzed Rated Steady State Transient 80 -- 85 4000V Motors Start -- --
Operate 110 110 90 96.5 --
l Operate lib lib 9i -
Operate lkb lifl5 g gi' ,
i 80b 480V Starters 4 Pickup 85 --
60 -- 80 Dropout -- --
Operate 110 110 90 90 -
Other Equipmenta
- a. The rating and ef fects of voltage variations on other equipment is described in the NSP submittal June 25, 1981.3
- b. NSP indicates that there are no known problems with starting of 480 volt equipment during dips resulting from starting 4 16 kv equipment. This is verified annually during ECCS actuation tests.13 terminal voltages to Class lE equipment. The worst case Class lE equipment terminal voltages occur under the following conditions:
- 1. The maximum voltage occurs under station no-load conditions when the 345kV source is at its historical high of 354kV and the Class IE system is supplied via the RAT.
- 2. The worst case transient voltage occurs when the ll5kV source is at its minimum expected value supplying the maximum plant loads via the SAT with the sequenced starting of ECC equipment concur-rent with the starting of two core spray pumps
- 3. The minimum steady-state voltage occurs as in 2 above except all ECCS equipment is running.
4.3 Analysis Result. Table 1 shows the projectr-d worst case Class IE -
equipment terminal voltages. Table 2 shows a comparison of the analyzed voltages with the undervoltage relay setpoints. .
l 4.4 Analysis Verification. NSP states that tests were performed in accordance with NRC guidelines and resulted in measured voltages approxi-
! mately 2% higher than calculated voltages.4*l4 4
-- - . . .-_._ ~_. - -- __.
TABLE 2. COMPARIS0N OF ANALYZED V0LTAGES AND UNDERVOLTAGE RELAY SETPOINTS
(% of nominal voltage)
Minimum Analyzed a Relay Setpoint i
Location / Relays Voltage Time Voltage (Tolerance) Time 4
! 4160V busa 15 or 16 "
! Degraded grid 96.7 continuous 93.4 + 0.5% 10 + 1 sec
, Loss of grid 76.3b <8 sec 63 T 6.7% 1 sec 1
l ,
- 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 I
- Class lE loads.
c
- b. Licensee states that the 4kV motors will accelerate to normal speed
~
within 8 seconds and bus voltage will recover to 96.4% of nominal. ,
t I
P
- 5.0 EVALUATION l
! Six rpview positions have been established from the NRC analysis !
guidelines' and the documents listed in Section 2.0 of this report. Each review position is stated belov followed by an evaluation of the licensee '
submittals. The evaluations are based on completion of changes described i
in Section 4.1.
^
Position 1--With the uinimum expected offsite grid voltage and' maximum
. load condition, each offsite source and distribution system connection l combination must be capable of starting and of continuously operating all !
! Class lE equipment within the equipment voltage ratings, i NSP has shown, by analysis, that the offsite sources and the onsite i distribution system connections have sufficient capability and capacity for >
< starting and continuously operating the Class lE loads within the equipment i voltage ratings (Table 1). ,
l 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 l equipment without exceeding the equipment voltage ratings. ;
l NSP has shown, by analysis, that the voltage ratings of the Class lE ;
j equipment will not be exceeded. ;
j !
. Position 3--Loss of offsite power to either of the redundant Class lE !
i -distribution systems due to operation of voltage protection relays, must '
) =
not occur when the offsite power source is within expected voltage limits, i t i I
- i. As shown in Table 2, voltage relays will not cause loss of Class 1E l 1 distribution systems when the offsite grid voltage is within expected j 4 voltage limits. t; t
i i
! 5 i i
i l
i
.. - . . . , _ , , _ _ _ , . . _ . . _ _ . _ , , . , _ . . _ . . _ _ , . . .__,..,r ., .
Position 4--The NRC letterl requires that test results verify the accuracy of the voltage analyses supplied.
The test results provided by NSP in their submittal of November 2, 19814 verifies the accuracy of the voltage analysis.
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 17).
NSP has analyzed the onsite 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 start-
- ing and operating voltage for all required Class lE loads with an accident in one unit and an orderly shutdown and cooldown in the remaining units.
This applies to multi-unit plants. It does not apply to the Monticello single-unit station.
6.0 CONCLUSION
S The voltage analyses submitted by NSP for Monticello Nuclear Generat-ing Plant were evaluated in Section 5.0 of this report. Upon the comple-tion of changes described in Section 4.1, it was found that:
- 1. Voltages within the operating limits of the Class lE equipment are supplied for all projected combinations of plant load and offsite power grid conditions.
- 2. The tests performed by NSP verifies the accuracy of the analysis.
- 3. NSP 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 buses, due to spurious opera-tion of voltage protection relays, will not occur with the off-site grid voltage within its expected limits.
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. NSP letter, L. O. Mayer, to Director of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, dated January 30, 1981. .
- 3. NSP letter, L. O. Mayer, to Director of Nuclear Reactor Regulation, '
U.S. Nuclear Regulatory Commission, dated June 25, 1981.
6 l
- 4. NSP letter, L. O. Mayer, to Director of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, dated November 2,1981.
- 5. NSP letter, L. O. Mayer, to D. L. Ziemann, Chief, Operating Reactors Branch #2, U.S. Nuclear Regulatory Commission, dated March 4,1977.
- 6. NSP letter, L. O. Mayer, to D. K. Davis, Acting Chief, Operatinc Reac-tors Branch #2, U. S. Nuclear Regulatory Commission, dated July 25, 1977.
- 7. NSP letter, L. O. Mayer, to D. K. Davis, Acting Chief, Operating Reac-
- tors Branch #2, U. S. Nuclear Regulatory Commission, dated October 14, 1977.
- 8. NSP letter, L. O. Mayer, to Director of Nuclear Reactor Regulatiou, U.S. Nuclear Regulatory Commission, dated April 21, 1978.
- 9. NSP letter, L. O. Mayer, to Director of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, dated October 31, 1979.
- 10. NSP letter, L. O. Mayer, to Director of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, dated May 15, 1980.
- 11. NSP letter, L. O. Mayer, to Director of Nuclear Reactor Regulation, U.S. Nuclear Regulatory Commission, dated August 4,1981.
- 12. "EG&G Technical Evauation Report on the Degraded Grid Protection for Class lE Power Systems for the donticello Nuclear Generating Plant,"
Rev. 2, dated August 1980. -
- 14. Bechtel Power Corporation, C. B. Hogg to B. E. Tam, Supervising Electrical Engineer, Northern States Power, dated September 22, 1981.
l 7
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