View source for 05000416/LER-1984-002, Final LER 84-002-02:on 840107,09,11,14,19 & 20 & 0223 & 24, Reactor Protective Sys Bus Breaker Trips Resulted in Loss of Shutdown Cooling.Trip on 840119 Caused by Circuit Board Failure.Remainder Caused by Voltage Transients

{{Adams
| number = ML20091H706
| issue date = 05/30/1984
| title = Final LER 84-002-02:on 840107,09,11,14,19 & 20 & 0223 & 24, Reactor Protective Sys Bus Breaker Trips Resulted in Loss of Shutdown Cooling.Trip on 840119 Caused by Circuit Board Failure.Remainder Caused by Voltage Transients
| author name = Byrd R, Dale L
| author affiliation = MISSISSIPPI POWER &amp; LIGHT CO.
| addressee name = 
| addressee affiliation = NRC OFFICE OF ADMINISTRATION (ADM)
| docket = 05000416
| license number = 
| contact person = 
| document report number = AECM-84-0292, AECM-84-292, LER-84-002, LER-84-2, NUDOCS 8406050257
| document type = LICENSEE EVENT REPORT (SEE ALSO AO RO), TEXT-SAFETY REPORT
| page count = 3
}}
{{LER
| Title = Final LER 84-002-02:on 840107,09,11,14,19 & 20 & 0223 & 24, Reactor Protective Sys Bus Breaker Trips Resulted in Loss of Shutdown Cooling.Trip on 840119 Caused by Circuit Board Failure.Remainder Caused by Voltage Transients
| Plant = 
| Reporting criterion = 
| Power level = 
| Mode = 
| Docket = 05000416
| LER year = 2084
| LER number = 2
| LER revision = 
| Event date = 
| Report date = 
| ENS = 
| abstract = 
}}

=text=
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Since January 7, 1984, several instances of RPS bus breaker trips have resulted in a loss of Shutdown Cooling. Dates of occurrences were January 7, 9, 11, 14, 19, and 20, and February 23 and 24.
Redundant trains of the shutdown cooling mode of RHR are supplied through a common inlet containing two motor-operated valves in series. The isolation logic for these valves receive power from the RPS bus. Loss of either RPS bus causes one or the other containment isolation valves to close, causing a total loss of shutdown cooling.
l l                      A trip on January 19 was due to a circuit board failure of an Electrical Protection Assembly (EPA). The remaining trips are attributed to voltage transients on the RPS buses. The time delay settings for the EPA breakers were increased to prevent trips on short transients. An increased tolerance range for the undervoltage EPA trip settings is being considered.
8406050257 840530 PDR ADOCK 05000416
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 .         ,                                                           Attachmtnt to AECM-84/0292 IIAC Pere 200A                                                                           U B. feUCLEA3 KEGULATOR7 COMMISSION LICENSEE EVENT REPORT (LER) TEXT CONTINUATION                         AP RovEO oMe aeo. mo-oio.
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0l2 0l 2     Gy 0 l 2 text in          .          ,anc r m w nn Since January 7, 1984, several instances of RPS bus breaker trips have resulted in a loss of Shutdown Cooling. Dates of occurrences were January 7, 9, 11, 14, 19, and 20, and February 23 and 24. The reactor was in Cold Shutdown during each event. In each case operators restored Shutdown Cooling within one hour in accordance with Technical Specification 3.4.9.2. The trips occurred on both bus A and B with power supplied by either the motor generator set or the alternate supply.
A trip on January 14 also resulted in a full scram signal, an isolation of the Reactor Water Cleanup System, a Division 2 Auxiliary Building isolation, an initiation of Standby Gas Treatment B, and the initiation of Control Room Fresh Air Unit B in the isolated mode. This was due to a planned Division 1 electrical outage concurrent with the trip of the RPS B bus.
A trip on January 19 was attributed to a circuit board failure of an Electrical Protection Assembly (EPA). The trip occurred as a half scram signal was reset. The faulty EPA logic circuit card was replaced.
The remaining trips have been attributed to voltage transients on the buses.
To preclude recurrence of these events, CGNS has completed three changes.
They are as follows:
: 1. The time delay settings for the EPA trip logic circuitry has been increased from 0.1 seconds to 3.5 seconds. This is in accordance with recently issued Revision 3 of General Electric's RPS Specification 22A3771AE.
: 2. The output setting of the power supplies has been increased from 120V to 125V.
: 3. The motor generator overvoltage relay setting has been increased to 140V to prevent trips while transferring power sources at the increased output.
GGNS will also request a Technical Specification change to increase the voltage setpoint tolerances for EPA breaker trips. This is a final report.
gagn M m.

E MISSISSIPPI POWER & LIGHT COMPANY Helping Build Mississippi P. O. B OX 164 0, J A C K S O N, MIS SIS SIP PI 3 9 2 05 May 30, 1984 NUCLEAR PRODUCTION DEPARTMEPIT Document Control Desk U. S. Nuclear Regulatory Commission Washington, D. C. 20555 Gentlemen:

==SUBJECT:==
Grand Gulf Nuclear Station Unit 1 Docket No. 50-416 License No. NPF-13 File:  0260/L-835.0 RPS Bus Breaker Trips Resulting in Loss of SDC LER 84-002-2 AECM-84/0292 Attached is Licensee Event Report (LER) 84-002-2 which is a final report.
Yours truly, L. F. Dale Director of Nuclear Licensing & Safety EBS/SHH:rg Attachment cc:   Mr. J. B. Richard (w/a)
Mr. R. B. McGehee (w/o)
Mr. N. S. Reynolds (w/o)
Mr. G. B. Taylor (w/o)
Mr. Richard C. DeYoung, Director (w/a)
Office of Inspection & Enforcement U. S. Nuclear Regulatory Commission Washington, D. C.       20555 Mr. J. P. O'Reilly, Regional Administrator (w/a)
U. S. Nuclear Regulatory Commission Region Il 101 Marietta St., N.W.,       Suite 2900 Atlanta, Georgia 30303
                                                                                     /
Member Middle South Utilities System
}}

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