IR 05000298/1993013
| ML20044H278 | |
| Person / Time | |
|---|---|
| Site: | Cooper  |
| Issue date: | 05/27/1993 |
| From: | Gagliardo J NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION IV) |
| To: | |
| Shared Package | |
| ML20044H272 | List: |
| References | |
| 50-298-93-13, NUDOCS 9306080134 | |
| Download: ML20044H278 (11) | |
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f APPENDIX
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U.S. NUCLEAR REGULATORY COMMISSION
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?.EGION I':
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Inspection Report: 50-298/93-13 Operating License: DPR-46
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Licensee: Nebraska Public Power District P.O. Box 499 Columbus, Nebraska 68602-0499 Facility Name:
Cooper Nuclear Station Inspection At:
Brownville, Nebraska Inspection Conducted: March 7-11 and March 29 through April 2, 1993 Inspector:
R. A. Kopriva, Senior Resident Inspector r
L. T. Ricketson, Senior Radiation Specialist
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Approved:
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. Gagliardo, Chief, Proj Section C Date'
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- Inspection Summary t
Areas Inspected: Special, unannounced inspection concerning the activities associated with inadvertently deenergizing a 4160v electrical breaker, resulting in the less of the shutdown cooling (SDC) system and unauthorized entry into the drywell area.
Results:
The control room operators appeared to have responded well to the event.
- Their actions, in response to the activities at the time the breaker was tripped, were executed efficiently (Section 1.1.2).
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Control room operators were cognizant of reactor water temperature at
all times.
Reactor water temperature increased from 170 F to 190*F before SDC was reestablished (Section 1.1.1).
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The control room operaters consciously elected to reestablish normal,
dedicated power to the SDC system after power had been lost.
It took the operators approximately 34 minutes to reinitiate SDC system flow after it had been isolated (Section 1.1.2).
The operator involved with accidentally tripping the wrong 4160v breaker j
had not followed the established procedures (Section 1.1.3.1).
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The procedure for racking out the 4160v breaker was comprehensive and
adequate for its intended function (Section 1.1.3.2).
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9306000134 930601 l
PDR ALOCK 05000298 G
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The licensee's immediate corrective actions did not appear to give any
consideration to the subject of failure to follow procedures
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(Section 1.1.4).
The licensee did not adequately control access to the drywell area, and
two contract personnel entered the area without signing the special work permit (Section 1.2.1).
Summary of Inspection Findings:
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Unresolved item for failure to follow procedures was identified
(298/9313-01) (Section 1.1.3.2).
Unresclved item for failure to follow procedures was identified t
(298/9313-02) (Section 1.2.2).
Attachments:
Attachment 1 - Persons Contacted and Exit Meeting l
Attachment 2 - Chronological list of Events
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i-3-f DETAILS
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1 FOLLOWUP (92701)
l 1.1 Loss of 4160v Breaker 1.1.1 Background The licensee had completed a scheduled reactor shutdown on March 5,1993. The licensee needed to remove power from Core A spray pump in preparation for
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performing a locai leak rate test on the Core A spray valves. The control-room operators reviewed the request for taking the Core A spray pump out of
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service and authorized the deenergizing and racking out of the required
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breaker at 3:15 a.m. on March 6.
At this time, the operator assigned to.
t perform the task went to the critical switchgear room, identified the appropriate breaker, and retrieved the tool required for racking out the breaker.
Upon returning to the breaker, the operator actually selected the
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breaker immediately to the left of the one required to be racked out.. At
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3:27 a.m. the operator depressed the trip button on Breaker SS1F, which
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controlled power to the 480v Substation F bus. At this time, the operator
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recognized that he had tripped the wrong breaker and contacted the control The control room operators had immediate indication that they had lost room.
power to 480v Bus IF. They received partial Group I, II, VI, and VII isolation signals and a full Group III isolation of the reactor water cleanup
system. A Group II isolation includes the residual heat removal (RHR) SDC
system.
The inspector noted that, at the time of the SDC isolation, the reactor water
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temperature was at approximately 170 F.
The system was isolated for
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24 minutes, and flow was reestablished in the SDC system 36 minutes after the system had initially been isolated. When SDC was reestablished, the reactor
coolant had reached 190 F.
1.1.2 Immediate Plant and Control Room Response to Inadvertent Opening of
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4160V Breaker SS1F
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l Upon receiving the several different group isolations, the control room
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operators reviewed their instrumentation and verified that the-response to the
loss of 480v Bus IF was as expected. The operator that had tripped the wrong i
breaker contacted the control room and notified them of his actions. The control room shift supervisor, who was-out in the-reactor building at the time e
the breaker was accidently tripped, responded to the critical switchgear room.
The shift supervisor confirmed that there were no personnel injuries and that
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there were no concerns of equipment problems or damage.
He then returned-to
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the control room to oversee the activities of the event recovery. As part of-i the licensee's shutdown risk program, the control room operators had been
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provided calculations and temperature curves of the expected heatup rate if they were to lose shutdown cooling. As the control room operators were responding to the event, they remained cognizant of the reactor water
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temperature at all times. At 3:37 a.m., the operators reenergized
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480v Bus IF.
The control room operators had removed the electrical loads from
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Bus IF prior to restoring power to it, so as not to overload the bus when it was reenergized. At the time the bus had been tripped, the reactor water cleanup system was controlling reactor water level and was, therefore, one of the first systems reestablished when power had been restored. The shift supervisor elected to cautiously reestablish the loads to Bus IF, reset the group isolations, and realign the systems and equipment that had been affected. The control room operators had methodically restored power to all
of the components associated with the RHR and SDC systems. The control room operators then opened the SDC isolation valves and, at 4:03 a.m.,
reestablished shutdown cooling to the reactor. Upon reestablishing shutdown j
cooling, the licensee contacted the resident inspectors and completed the appropriate notification to the NRC for having experienced an unexpected
engineering safety-feature actuation.
t 1.1.3 Followup 1.1.3.1 The Inspector's Initial Review of the Event
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On March 7, 1993, the inspector reviewed the operators actions which had caused him to trip the wrong breaker. Several indicators, located on the breaker, should have prevented the operator from tripping the breaker.
It was
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not immediately apparent to the inspector how the operator had not recognized
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the indicators when performing his task.
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The inspector reviewed the log books, instrumentation, chart recorders, and alarm printouts in the control room.
Initial review of the control room i
equipment and available records indicated that the control room operators had
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responded well to the event and no personnel or plant equipment anomalies were
noted. While trying to fully comprehend the association between the loss of
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the 4160v Bus IF and the complete isolation of the SDC system, the ir.gector asked the control room operators which isolation signal or power loss isolated the SDC system, and which SDC system valves isolated. The operators were unable to completely answer the inspector's question at that time.
i 1.1.3.2 Followup to the Loss of Bus IF On March 8, 1993, the resident inspector and licensee management performed
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i walkthroughs of the operator's activities pertaining to the inadvertent
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tripping of the wrong breaker.
Several items were immediately identified and available to the operator to indicate that he was working on the wrong i
breaker. First, the inspector noted that the breakers were clearly marked at l
the top with a number designation and word identification. Second, just above
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the identification label is the control switch which had a " tripped" or green light, and a " closed" or red light. Third, toward the bottom of the breaker there are indication windows, or flags, on the breakers, red for closed or
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energized and green for open or deenergized.
Fourth, the access door, or
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shutter, for the tool to rack out a breaker is interlocked with the power to
the breaker.
If the breaker is energized, the door is not supposed to ope.
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During the initial reviews of the operator's actions, it was difficult to
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understand how the operator had tripped the wrong breaker.
The inspector reviewed Operating Procedure 2.2.18, "4160V Auxiliary Power Distribution," Revision 33, for racking out 4160v breakers, and found it sufficient to complete the assigned task.
On March 9, 1993, the inspector interviewed the operator that had actually performed the activities that had initiated the loss of the 4160v breaker.
During the interview, the operator indicated that, on March 6, when he was directed to rack out 4160v Breaker CSPIA, he did not have a. copy of the
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procedure with him, and the steps he had taken were not in accordance with the procedure. The operator was not required to have a copy of the procedure with him for this activity. Upon entering the critical switchgear room, the operator correctly identified the breaker to be worked on and then went to the other end of the room and retrieved the tool to rack out the breaker. When
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the operator returned to the breaker, he did not reconfirm that he was working
on the correct breaker. He had selected the breaker immediately to the left
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of Breaker CSPIA. The way this particular operator positioned himself to perform the task of racking out a breaker caused all of the breaker identification and indicators to be obscured from'the operator's view.' The operator then tried to open the shutter to insert the tool for racking out the
'i breaker. The door did not open as designed because the breaker was energized.
This should have been a significant indication to the operator that he should
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reverify that the breaker he was working on was the correct one. There-is also a caution at this point in the procedure stating that, if the shutter is hard to move, the breaker may be closed. The operator indicated that in their operator training, if an access door did not open as expected, action should be to depress the trip button. This action caused Breaker SS1F to open.
Thus, the operator did trip the breaker causing the loss ~ of power to Bus IF.
The operator's failure to verify, by the labels _ on the breaker, that he was in front of the breaker to be racked out, is an unresolved item (298/9313-01).
10 CFR Part 50, Appendix B, Criterion V, states, in part, " Activities affecting quality shall be prescribed by documented instructions, procedures, of drawings, of a type appropriate to the circumstances and shall be accomplished in accordance with these instruction, procedures, of drawings."
Step 8.1.4 of Cooper Nuclear Station System Operating Procedure 2.2.18, Revision 33 (a safety related procedure), states, " Verify by the labels on the breaker and on the relay cabinet door that you are in front of the breaker
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that is to be racked out."
This unresolved item will be reviewed with additional enforcement items in NRC Inspection Report 50-298/93-17.
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The inspector questioned the use of a second means of verification that the
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correct breaker was about to be tripped.
Licensee representatives indicated
that, for this type of activity, backup verification was not required. The l
operator's training records were reviewed and found to be acceptable. The operator had completed training on racking out 4160v breakers approximately
.l 12 months prior to the March 6 event, and the licensee did not require refresher training for racking out breakers.
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1.1.3.3 Shutdown Cooling Isolation Followup i
i During the inspectors' investigation on March 7, 1993 licensee representatives
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were unsure of why the SDC system had isolated. Drawing from past experience
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with partial Group II isolations, they indicated that an isolation of the SDC system was expected. The inspector continued to question the licensee
representatives on the specific signal that had caused the isolation.' The
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licensee representatives were initially unable to explain the instrument' and
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electrical logic which caused the SDC system to isolate, nor could they
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identify which valve had actually closed. The inspector and one of licensee's managers reviewed the process and instrument diagrams, and the station l
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electrical diagrams, to determine what had actually caused the SDC system to isolate. The loss of Breaker SSIF (Division I) caused the loss of the 480v Bus IF. This caused the loss of power to a relay (16A-K28) associated with
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the system interlock that will isolate the SDC system if the system pressure j
is 75 psig or greater and, thereby, protects the SDC system from becoming i
overpressurized. Relay 16A-K28 being deenergized caused a closure signal to j
Valve RH-MOV-17, which is the SDC system outboard isolation valve.
Since the i
motor operator for Valve RH-MOV-17 is powered from a 250v DC source, it was
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able to close and isolate the SDC system. All equipment and instrumentation l
responded as expected. The licensee reviewed their plant management j
information system (PMIS), which is a computer log of event activities, and confirmed that Valve RH-MOV-17 had closed.
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On March 8,1993, the inspector questioned the licensee about their review of
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the event. At that time, the licensee had not performed their review. The inspector also questioned the licensee on their review of the PMIS computer
records of the event. At that time, the licensee representatives had not yet
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initiated their own review of PMIS beyond confirming the closure of
Valve RH-MOV-17.
i On March 9, 1993, the inspector interviewed the shift supervisor that had
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responsibility for control room operations at the time of the event. The
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shift supervisor discussed the activities of the event, the methodology of reestablishing power to the SDC system, and the clearing of the SDC system isolation. With reactor water temperature indication available, and no
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apparent equipment problems, the shift supervisor had elected to proceed
i cautiously in reestablishing SDC flow to the reactor. The actions taken by the control room operators took approximately 36 minutes to complete with a reactor water temperature increase of 200F.
1.1.3.4 Conclusion i
i After having reviewed the operator's actions, the inspector recognized several
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items that could have led the operator to question his actions in trying to l
rack out Breaker SSlF, which had not been deenergized. The identified I
indicators (the shutter door that would not slide open and the breaker status j
lights) offered the operator the opportunity to question his actions.
The
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operator did not recognize these indicators as potential concerns, nor was there any evidence that the operator had considered reverifying that he was at
the correct breaker.
The licensee's short-term review of the event, as of March 8, 1993, had not
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verified plant response.
1.1.4 Corrective Actions The licensee's first corrective. action taken in response to the event was to write the breaker identification and description directly on the floor at.the base of the 4160v breakers. This identification was more in the line of sight of an operator racking out a breaker than the identification located at the top of the breakers. Additionally, there were other activities formulated
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that were to be tracked via the licensee's action and commitment tracking system. These items included:
Development of a presentation concerning the sequence of events and
circumstances where self-checking was and was not used for this event.
Placing emphasis on those points where self-checking would have
precluded this occurrence.
Note: These materials were to be completed by March 13, 1993, and all crew presentations completed by March 27, 1993. The documentation which would accompany the presentations would be routed through the plant managers office to the training department.
(The Operations Department was to be responsible for-this item.)
Evaluating and developing further label enhancements for the critical e
and noncritical switchgear breakers to replace temporary measures. Also
plant labeling was to be reviewed from a human factors standpoint concerning ease of recognition during normal operational work efforts, e.g., breaker operations, valve manipulations.
(The Operations Department was responsible for this item and was tasked with providing q
management with a status report by June 1, 1993.)
Evaluating through the Document Evaluation and Review Committee if
enhancements to the self-checking or Industry events lesson plans should l
be made.
(The Training Department was responsible for this item and was tasked with providing management with a status report by June 1, 1993.)
t The licensee had assigned a Corrective Action Review Board to investigate the actions taken, or planned, in response to the trip of Breaker 4160v SSlF.
The inspector reviewed all of the corrective actions the licensee had
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completed or had in progress.
Tb? inspectors found that the licensee had not i
addressed the problem of personnel failing to follow procedures.
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follow procedures appears to be the root cause of the event. The inspector
realized that, at the time the inspection ended, the licensee was still formulating future corrective actions.
1.2 Radiological Controls for Drywell Entry
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The inspectors reviewed the circumstances surrounding the entry on March 8, 1993, by two contract mechanics into the special work permit area surrounding the drywell.
1.2.1 Discussion Two contract mechanical maintenance workers were assigned to help licensee mechanics with work to be performed on the torus. Access to the work area was to be through the southeast quadrant of the reactor building. One of the contract personnel had been to the work area previously and indicated he knew the way and that he and the other contract mechanic would meet the licensee mechanics at the work site.
When they had completed donning anticontamination clothing, the contract
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mechanics entered the reactor building and noted that the entrance to the area
had been changed and was unfamiliar to the contract mechanic that had worked
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there before. Contanination control barriers had been erected and had altered the appearance of the area. The contract mechanics stated that they next asked a contract radiation protection technician where the lead licensee mechanic had gone. The contract radiation protection technician directed the contract mechanics into the drywell area without further question or
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instruction. The contract mechanics entered through an access control gate into the drywell area and tried unsuccessfully to find their way to their work area. During the time the contractors were trying to locate their work area, they did not enter into an area in which they would have been able to receive-i significant radiation doses. A radiation protection technician observed the two contractors and questioned them as to their purpose for being in the area.-
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During the discussion, one of the licensee mechanics _ returned, observed the contractors from outside the area, and identified them. The two contractor
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mechanics exited the area. The contract radiation protection technician.
terminated employment soon after the occurrence for unrelated reasons and was not interviewed by the NRC inspectors.
The licensee's immediate corrective actions included the counseling of the lead licensee mechanic with regard to the proper handling and instruction of persnnnal unfamiliar with work areas; physical rearrangement of the radiation protection control point desk; and retraining of the contract mechanics in radiation worker practices.
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1.2.2 Conclpsions The inspector concluded that the individuals did not follow Health Physics Procedure 9.1.1.4, Sections 8.4.3.1 and 8.4.3.5, which require individuals entering into a special work permit area to read the standing work permit and
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I affix their signatures. This item is unresolved and (298/9313-02) will be reviewed with additional enforcement items in NRC Inspection Report 50-298/93-17.
No significant radiation doses were received by the individuals.
Immediate corrective actions appeared adequate. According to the licensee, there were approximately 80,000 entries into the radiologically controlled area and over 500 entries into the drywell.
Similar occurrences have not been identified.
However, the event demonstrated that the arrangement of the drywell control point did not ensure optimum control of personnel.
It also demonstrated that it was poor practice to allow workers unfamiliar with the plant to go
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unescortr.
Finally, if the contract radiation protection technician was responsible for misdirecting the workers, it raises questions as to the
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knowledge, training, and preparation of such individuals for control point-duties.
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.l ATTACHMENT 1
1 PERSONS CONTACTED L. E. Bray, Regulatory Compliance Specialist R. Brungardt, Operations Manager M. A. Dean, Nuclear Licensing and Safety Supervisor C. M. Estes, Management Trainee i
J. R. Flaherty, Engineering Manager
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R. L. Gardner, Plant Manager J. M. Meacham, Site Manager C. R. Moeller, Technical Staff Manager J. R. Myers, Senior Technical Staff Engineer G. E. Smith, Quality Assurance Manager The licensee personnel listed above attended the exit meeting held on i
March 11, 1993.
In addition to the personnel listed above, the inspectors contacted other personnel during this inspection period.
2 EXIT MEETING
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An exit meeting was conducted on March 11, 1993. During this meeting, the inspector reviewed the scope and findings of this report. The licensee did-not identify as proprietary any information provided to, or reviewed.by, the
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inspectors.
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ATTACHMENT 2
Chronological Order of Events:
Date Time Event
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i 3/5/93 9:40 p.m.
issued C.0.93-166
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10 p.m.
started "A" RHR Service water booster Pump A to commence flush of the SDC system line 3/6/93 12:10 a.m.
completed flush of Loop A RHR SDC line 1:38 a.m.
secured reactor recirculation Pump A 1:40 a.m.
placed Loop A of RHR in SDC with RHR C pump running 2:40 a.m.
reactor less than 212 F - opened head vents 3:15 a.m.
declared core spray Pump A inoperable 3:27 a.m.
loss of 480v Bus IF due to Breaker SSIF being
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inadvertently racked out. Station operator
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tripped 4160 Breaker SS1F, loss.of 480v Bus IF.
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Received partial Group 1, 2, 6, and 7 isolations and a full Group 3 isolation.
j Group 1 MSIV isol Group 2-includes RHR SDC isol Group 3 reactor water cleanup
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Group 6 ventilation Group 7 sample lines
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3:37 a.m.
recovered 480v Bus IF and restored reactor water cleanup
4:03 a.m.
started SDC Loop A using RHR C pump.
Reactor l
coolant temperature increased from 170 F to 190oF.
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4:05 a.m.
contacted NRC resident inspector
4:12 a.m.
contacted NRC headquarters - ENS
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notification r
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