ML19350E629
| ML19350E629 | |
| Person / Time | |
|---|---|
| Site: | Davis Besse  |
| Issue date: | 06/16/1981 |
| From: | Crouse R TOLEDO EDISON CO. |
| To: | Stolz J Office of Nuclear Reactor Regulation |
| References | |
| 722, NUDOCS 8106230373 | |
| Download: ML19350E629 (6) | |
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TOLEDO EDISON ACHAAo P. C AOUSE v
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W191259-5221 Docket No. 50-346 License No. NPF-3 Serial No. 722 June 16, 1981 Mr. John F. Stolz, Chief Operating Reactors Branch No. 4 Division of Licensing U. S. Nuclear Regulatory Commission Washington, D.C.
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Dear Mr. Stolz:
On October 9, 1979 (Serial No. 543) Toledo Edison responded to Robert Reid's letter dated August 8,1979 (Log No. 416) relating to the electrical di' ribution system at Davis-Besse Nuclear Power Station Unit No. 1.
On January 2, 1981 (Serial No. 673) Toledo Edison responded to questions raised in Robert Reid's letter dated November 14, 1980 (Log No. 630) related to the same subject.
On April 6,1980 (Log No. 690) you wrote requesting additior.a1 inform-ation required to complete your revieu. Toledo Edison's response to your request is attached.
Very truly yours,
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ADDENDUM 2 TO:
g ANALYSES OF THE ADEQUACY OF THE DAVIS-BESSE NUCLEAR POWER STATION-ONSITE ELECTRICAL AUXILIARY DISTRIBUTION POWER SYSTEM VOLTAGES Prepared in
Response
to the Nuclear Regulatory Conwnission i
Request for Additional Information
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of April 6, 1981 June 16, 1981 l
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Docket No.'50-346 License No. NPF-3 Serial No. 722 i
June 16, 1981 TABLE OF CONTENTS
' Responses Items la & lb & 2 Appendix A Case Numbering System (Revised 4-15-81)-
Figure 1 Davis-Besse Nuclear Power Station-Single Line Diagram Figure 2 Davis-Besse Nuclear Power Station Graph of Safety Related 4.16 KV. Bus Voltage Versus Case Numbers.
Figure 3 Davis-Besse Nuclear Power Station Graph of Safety Related 480 V Bus Voltage Versus Case Nu:abers.
Figure 4 Davis-Besse Nuclear Power Station Graph of Safety Related 240 V Bus Voltage Versus Case Numbers.
Figure 5 Davis-Besse Nuclear Power Station Graph of S4fety Related 120 V Bus Voltage Versus Case Numbers.
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l Docket No. 50-346 License No. NPF-3 Serial No. 722
-June 16, 1981 ITEM 1.a.
Reference 2 and Reference 4 provided the results of calculations for 4160 volt buses and 480 volt buses. Submit calculated voltages for all low voltage AC (less than 480 volts) Class IE buses. This should' include the voltage available for contactors or starters for Class IE equipment to ensure their capability to pickup, operate and prevent dropout for all-transient and steady state cases. Document that all low voltage AC Class IE equipment will operate within the required voltage ratings for each case analyzed.
RESPONSE TO ITEM-1.a.
The analysis sent in our letter dated October 9,1979 and January 2,1981 did not include the voltages available on 240 and 120 volt AC, Class IE buses. The calculated voltage for these buses under tran:ient conditions are now included in Figures 2 thru 5 of this addendum.
The onsite distribution conditions determined to result in the most severe voltage drop are presented on case numbers with a prefix of eleven (11). Appendix A to this submittal contains a complete summary of case numbering methodology.
The two values of transient voltage levels shown in Figures 2 thru 5 are based on the minimum and maximum values of 345 KV grid voltage available (as explained in the previously submitted analyses). Only minimum grid voltages, however, are addressed in this submittal.
Assumed conditions for the transient voltage calculations are:
All 13.8 KV and 4.16 KV loads are running under steady state conditions.
SFAS Incident Levels 1, 2 and 3 loads are started on all Class IE buses (4.16 KV, 480 V, 240 V and 120 V)' simultaneously.
The initiating event is a 14.1 square foot break in the Reactor Coolant System Hot Leg.
This transient is representad by Case 11621 on Figure Nos. 2, 3, 4 and 5.
The steady state voltage drop from 480 V to the 240 V and 120 V buses is negligible'as tne 240 V and 120 V loads are very small. Due to the negligible drop, the percentage voltage value on the 480 V buses remains the same as on the 240 V and 120 V buses.
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Docket No. 50-346 License No. NPF-3 Serial No. 722 June 16, 1981 The analyses show that the transient voltages on the 240 V and 120 V buses caused by the simultaneous starting of all SFAS Incident Level.1, 2 and 3 loads on all buses are 62.0% for the 240 V and 61.5% for the 20 V buses as illustrated by Case 11621 on Figures 4 and 5.
These voltages are below the minimum acceptable voltage for motor starting which is 67.1%. Failure of any safety components to start due to low voltage does
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not result, however. The following paragraphs provide an explanation:
On a simultaneous start on all SFAS Iccident Level 1, 2 and 3 loads the 4.16 KV and 480 V motors will accelerate to their rated speeds within 2 to 4 seconds, depending upon the perentage of voltage available to the 4.16 KV and 480 V buses. The voltage available to the 240 V and 120 "
buses will not be sufficient to start their respective motors, howes er, and the motors will remain stalled until the voltage reaches the 67.1%
required for motor starting. With the 4.16 KV and 480 V loads reaching their rated speeds within 4 seconds, the design limit for stalled condition of 5 seconds is not reached-and the 240 V and 120 V motors will be started and run undamaged.
To demonstrate the capability of motor starters, Toledo Edison has conducted tests which show that contactors will not drop out above 50% of the normal bus voltage, so a 4 second stall at approximately 61% bus voltage will not cause a loss of motor availability.
The cause of excessive voltage drop has been attributed to the 3 KVA, 480 volt, 240 volt transformers supplying power to 240 volt MCC YUE2 and YF2. ' These transformers will be replaced by 30 KVA transformers during the 1982 Refueling Outage. After the implementation of this change, the transient voltage available for the 240 and 120 vcit loads will be improved to 70.5% and 69.7%, respectively (Case 11521 T30).
SFAS incident Level 4 has not been considered in tr ansient voltage calculations since it occurs 5 to 6 ceconds after Level 1, 2 and 3 occurrence. At that time all the SFAS Level 1, 2 and 3 loads are running under steady state conditions. When SFAS Level 4 is actuated, the starting ~of the 480 V Containment Spray Pump will cause a voltage dip on the 240 V and 120 V buses.
In che opinion of Toledo Edison electrical engineers, the dip in voltage is not as severe as the simultaneous starting of SFAS Level 1, 2 and 3 loads and, therefore, will not affect motors running on steady state voltage.
In light of the preceding analysis, Toledo Ed son has concluded that the motors on the 240 V and 120 V buses will have sufficient voltage to close all SFAS-required valves within the time limits listed in Davis-Besse Technical Specification Table 3.3-5, Safety Features Systems Response times. rr
e Docket No. 50-346 License No. NPF-3 Serial No. 722 June 16, 1981 ITEM 1.b.
"Do these buses supply any instruments or control circuits required by GDC-13? If so, is all equipment capt.ble of sustaining the analyzed voltages without blowing fuses, overheating, etc., and without affecting the equipment's ability to perform the required function."
RESPONSE TO ITEM 1.b.
Instruments and control circuits required by GDC-13 are supplied through inverters, and are free from transients resulting from system disturbances of the type in question.
ITEM 2 Reference 3 states that the final report of tests are required in Reference 1 will be completed by August 1, 1980. What is the status of the tests and report?
RESPONSE TO ITEM 2 As a result of your letter, " Adequacy of Station Electric Distribution 4
yscr7s Voltages" (Log No. 416) dated August 8, 1979, the following test
'r-4 eas planned for Davis-Besse Unit No. 1:
iest Cases 12121, 12221 and 12021 were scheduled to be run prior to thc completion of the 1980 Refueling Outage.
In Toledo Edison's submittal to Robert Reid dated October 27, 1980 (Serial.No. 649), however, it was stated that test 12121 had to be postponed until the Toledo Edison requested Technical Specification change. dated March 23, 1979, allowing an undervoltage circuit bypass, was approved. Subsequently, it was determined that both test Case 12221 and 12021 would also be postponed pending the Technical Specification change. Toledo Edison's request is still undergoing staff review.
Therefore, the tests have not been performed. ---
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