IR 05000482/1980018
| ML18046B402 | |
| Person / Time | |
|---|---|
| Site: | Wolf Creek  |
| Issue date: | 12/04/1980 |
| From: | Crossman W, Vandel T NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML18046B403 | List: |
| References | |
| 50-482-80-18, NUDOCS 8101280530 | |
| Download: ML18046B402 (10) | |
Text
consumers Power company General Offices: 212 West Michigan Avenue, Jackson, Michigan 49201 * Area Code 517 788-0550 January 16, 1981 Mr James G Keppler Office of Inspection & Enforcement Region III U S Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 DOCKET 50-255 - LICENSE DPR-20 -
PALISADES PLANT -
LICENSEE EVENT REPORT 81-01 - STATION BATTERIES Attached is Licensee Event Report 81-01 - Station Batteries - which is report-able under Technical Specification 6.9.2.A(2).
David P Hoffman (Signed)
David P Hoffman Nuclear Licensing Administrator CC Director, Office of Nuclear Reactor Regulation Director, Office of Inspection & Enforcement NRC Resident Inspector - Palisades Plant Attachment -
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EVENT DESCRIPTION AND PROBABLE CONSEQUENCES@
!During charging of station batteries, the output breakers of both batteries
[§]]] 1were inadvertently opened for approximately one hou Because of recent modj
[[ID lifications to the DC distribution system, diesel generator starting capabilij
[III] lty was maintaine In addition, all four battery chargers were in operation I
[]]]] land were capable of supplying remaining essential DC load Upon discovery, fIITI !proper breaker alignment was restore Probable conseq_uences under antici-I I]]]] lpa+/-ed transients w011ld have posed no threat to the p11bljc
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!Personnel error (failure to follow procedure) resulted in the misalignmen OJJ] !Corrective actions include:
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Attachment to Licensee Event Report 81-01 Consumers Power Company Palisades Plant Description of Event On January 6, 1981, two plant electricians were in the process of terminating a battery charge which had been started the previous da The procedure required shifting the battery chargers on each bus by opening the breakers associated with the chargers in service and closing the breakers of the idle charger Instead, both battery breakers were opened and the breakers for the idle chargers were close As a result, the station batteries were not connected to their respective buses; however, all four battery chargers were in service, and no interruption of DC power occurre Coincident with the shifting of battery chargers, the procedure required adjusting the battery bus voltage; because of the improper alignment, the voltage could not be adjusted to the specified valu Investigation by a supervisor led to discovery of the improper lineup, and proper breaker alignment was immediately restore The breaker misalignment existed for approximately one hou Probable Consequences During the one hour period that the breakers were mispositioned, the plant suffer-ed no detrimental consequence DC and preferred AC power for instruments and controls were supplied via the charger In addition, 2400 volt buses lC and lD control power, and diesel generator 1-1 and 1-2 field flashing and control power (for starting) are supplied by a panel powered directly from the station batteries (eg, power available whether battery breakers open or close).
Three transients which could result in a challenge to the station batteries have been analyzed to determine if plant safety would be maintained throughou While the scenarios chosen do not represent all those which could result in a challenge to the station batteries, they represent those considered to have a reasonable probability of occurring during the one hour time period in questio The sequence presented in the following discussion was constructed based on manufacturer's data regarding relay timing, plant electrical prints, and selected outputs from the plant data logge Main Generator Trip The first plant transient considered is one in which the main generator trip The sequence of events following such an occurrence is presented on Attachment At time zero, one of the main turbine generator protection relays 386B, P or C is energize The fast transfer relay 383-11 is energized 65 milliseconds (msec)
later and following this the 2400 V bus lC startup power breaker 152-106 closes and station power breaker 152-105 open Bus lC breakers and associated relays have been referred to in this scenario but it should be noted that the events are mirrored on bus l With the fast transfer having been executed, power to the DC buses is maintained and the sequence of events continues as normal with the diesel start relays being energized at 310 msec and the control rod drive clutch relays de-energized shortly thereafte..
Licensee Event Report 81-01 Palisades Plant January 16, 1981 Reactor Trip
Attachment 2 presents the sequence of events for a reactor trip. It can be seen that as with the previous transient analyzed, the fast transfer maintains power to the DC buses and the sequence of events progresses as norma As in any reactor trip, voltage is maintained on.the 2400 volt bus lC through the station power breaker 152-105 until the fast transfer relay 383-11 is energize Since DC power to the station power breaker and startup power breaker 152-106 is supplied from panel D-llA which is connected directly to the battery, the fast transfer is execute Similar breakers and relays are associated with bus l The diesels are started during this transient as can be seen at the 310 msec time on Attachment R Bus Trip R bus trip represents a loss of offsite power event in which the plant is simultaneously trippe It has occurred only three times during the history of Palisades; therefore, it is not considered high probability even Attach-ment 3 presents*the initial sequence of events during such a transien Follow-ing the trip of the R bus, startup transformer 1-2 low voltage relay 127-5 is energized and the cooling tower fans and pumps are tripped since they receive power from startup transformers 1-1 and 1-3 which, in turn, receive power from the R bu At 575 msec into the transient, the auxiliary undervoltage relay 127X-5 is energized and 30 msec later the diesel start relays are energize The lack of cooling water to the condenser would produce a mechanical vacuum trip at about 30 second However, normal operating procedure is to trip the reactor as presented in the Emergency Operating Procedure EOP This time has been arbitrarily chosen on Attachment The sequence of events after the reactor trip is similar to that presented on Attachment 2 with the following exceptions: The load shed relays are energized at time 695 mse energized, both the preload shed relay 144D-l and the voltage auxiliary relay must be energize For these relays to be startup transformer lov The 2400 V loads on bus lC and load control center 11 are she.
Startup breaker 152-106 is not close Following the above events and with the opening of station power breaker 152-105, the plant is without power except for the DC loads connected to the batteries for a short period of tim This time is less than 10 seconds since this is the maximum time required for the diesels to start and acquire proper voltag At this time, the operator would manually close the diesel generator breaker 152-107 since the load shed relay 194-108 de-energizes during the short period of time without power and, as displayed on the logic diagram of Attachment 4, automatic closure is not possibl As can be seen from the same attachment, manual closure
Licensee Event Report 81-01 Palisades Plant January 16, 1981 of the breaker is possible after positioning the control switch to the "on" positio It should be. noted that DC power for breaker 152-107 is supplied from panel D-llA which is connected directly to the batter With the diesel connected to the 2400V bus lC, manual start of the normal shutdown sequencer is necessary to return the sequence of events to norma Similar breakers and relays to those described in this scenario for bus lC are associated with 24oov bus l Eighty-five (85) amperes are required during normal power operation to meet the demand of a DC bus and the two preferred AC buses connected to it via the inverter A reasonable expected maximum load on the two chargers connected to the DC bus when the diesel generator breaker is closed in the above trans-ient would be 85 amps plus the locked rotor current of two DC oil lift pump The locked rotor current would be twice the full load current which is 70 amps per moto The total maximum current thus equals 365 amp Each charger is rated at 200 amp Therefore, the two chargers combined would have sufficient capacity to handle the loa One further point to be mentioned about the above transient is that during the period of time the diesel is starting and the plant is without power, all valves and controls will be in their safe mod Based on the above analysis, it is concluded that no significant threat to public health or safety existed during the period of time the battery breakers were mis-positione Cause of Occurrence As evidenced by the sequence of events described in the "description of event",
personnel error (eg, failure to follow a written procedure) resulted in the breaker misalignmen Investigation has revealed the following:
The procedure addressed the minimum skill levels required of personnel performing the activit Both individuals conducting the evolution met the minimum skill level requiremen Both individuals had been briefed regarding the evolution prior to its commencemen Both had previously participated in this evolutio The procedure was present at the scene of the activit Corrective Actions The following short term corrective actions are being implemente.
Daily audits of plant operations are being conducted by a corporate manage-ment representativ Licensee Event Report 81-01 Palisades Plant January 16, 1981 A committee consisting of a member of corporate manangement (in addition to the corporate representative referenced in item 1 above), a Senior Reactor Operator, and another qualified engineer will review all safety-related surveillance and maintenance procedures and other maintenance procedures which cover work to be conducted in vital areas before they are used again, to assure that: Each procedure is specifically identified as being safety related, or as having the potential to affect safety-related equipment; Authorization to perform work is required from plant management; Special notification of work performed is made to the Shift Supervisor; System conditions to perform work are defined; Minimum personnel skill-level is defined; and Return-to-normal verification requirements are specifie.
All personnel who perform safety-related work or other work in vital areas will be reinstructed on the importance of strict adherence to procedures, and the necessity for performance of all assigned duties in a disciplined and professional manne.
Immediately upon their completion, all activities involving the manipula-tion of safety-related circuits or systems will be verified by a second qualified individua Qualified individuals will be designated by the Plant Manager for the specific task.
The specific circuitry involved in the January 6, 1981, event will be reviewed to determine if control room indications are required to show when an abnormal lineup exist Long term corrective actions are being develope !Energized 386 B,P,C Energized
0 ATTACHMENT 1 GENERATOR TRIP 152-106 Closed 152-105 Tripped 305-1/ AST
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E_n_e_r_gcS~ 306D-l, 2 Energized 305-1,R Energized r---------,()>-----Qi-----O---O Reactor Turbine 63/AST-2 Tripped Mechanical Energized Trip l. _______
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ATTACHMENT 2 REACTOR TRIP
..-----0 152-106 Reactor 63/AST-2 386-C l Closed Tripped Energized Energized 0-------0-*----o-----Oo*----- -----o 152-105 Turbine 305-L,R 383-11 Tripped Mechanical Energized Energized Trip 305-L/AST Energized-0 306D-l,2 Energized I. _______
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Cooling Tower Fans and Pumps Trip 100 200 ATTACHMENT 3 R BUS TRIP 127X-5 Energized
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Load Shed Load Shed l
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0 2400, 48ov Relays Energized 386-C_
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-00.------*****o-------*-o Reactor Turbine 305-L,R 383-11 152-105 Tripped I..
400
...... l 500 Tripped Mechanical Energized Energized Trip i
600 TIME (MSEC)
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Voltage 194-108 ATTACHMENT 4 DIESEL BREAKER 152-107 106-Dl Energized 152-105 Open 152-106 152-107
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162-107X l I De-energized 186-107 De-energized AUTOMATIC Control Switch On position 152-105
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152-107 Open r===-~--Cl_o_s_e_d _______ _
162-107X T De-energized 186-107 De-energized MANUAL
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