ML20210E246
| ML20210E246 | |
| Person / Time | |
|---|---|
| Site: | Zion File:ZionSolutions icon.png |
| Issue date: | 03/24/1986 |
| From: | Muffett J, Westberg R NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III) |
| To: | |
| Shared Package | |
| ML20210E241 | List: |
| References | |
| 50-295-86-08, 50-295-86-8, NUDOCS 8603270289 | |
| Download: ML20210E246 (3) | |
See also: IR 05000295/1986008
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U.S. NUCLEAR REGULATORY. COMMISSION
REGION III
Report No. 50-295/86008(DRS)
-Docket No. 50-295
License No. DPR-39
Licensee: Commonwealth Edison Company
P.O. Box 767
Chicago, IL 60690
Facility Name: Zion Nuclear Power Station, Unit 1
Inspection At: Zion, IL
Inspection Conducted: March 12-13, 1986
Inspector:
R. A. Westberg
3/
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Date
Approved By:
J. W. Muffett, Chi
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Plant Systems Section
Date
Inspection Summary
Inspection on March 12-13, 1986 (Report No. 50-295/86008(ORS))
Areas Inspected: Routine, announced inspection by one regional inspector of
plant trips - safety system challenges.
It was conducted in accordance with
NRC Inspection Procedure No. 93702.
Results: No violations or deviations were' identified.
8603270299 e60324
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DETAILS
1.
Persons Contacted
Conro nweal th_E_d i s on Compa ny_( C Ecol
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- G. Plim1, Station Manager
- E. Fuerst, Superintendent Production
- W. Stone. Quality Assurance Supervisor
- A. Amoroso, Technical Staff Group Leader, Electrical
M. Bailey, Technical Staff Engineer
- J. Kish, Resident Inspector
- Indicates those attending the exit meeting on March 13, 1986.
2.
Review of Reactor Trip _ Caused _ by_1B_ Reac_ tor Trip Breaker
The purpose of this inspection was to review the facts relative to the
reactor trip on March 13, 1986. This review also included the excessive
response time incident of March 3,1986, procedure reviews, interviews
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with involved personnel, and inspection of the IB reactor trip breaker
(RTB).
a.
Documents Reviewed
(1) Maintenance Procedure No. E015-1, " Reactor Trip Breaker
Maintenance," Revision 6.
(2) Test Procedure No. PT-5, " Reactor Protection Logic,"
Revision 14
(3) Schematic Diagram No. 22E-1-4884, " Reactor Trip Switchgear
Breaker," Revision J.
b.
Inspection Results
The inspector's review of the procedures, the RTB schematic, and
interviews with involved personnel indicated that the reactor trip
was caused by the turbine trip which resulted when cell switch
No. 52h/RTB failed to open when the IB RTB was ir. properly racked
into place. When the bypass breaker was racked out to place the
IB RTB back in service, continuity through cell switch 52h enabled
the circuit logic which shut off the oil supply to the turbine
control valves causing a turbine trip. The reactor protection logic
then tripped the reactor 28 milliseconds later.
The inspector inspected the IB RTB and the switchgear cubicle.
At the inspector's request, an operator was able to duplicate the
condition that caused the turbine trip. With the breaker racked in
and electr:cally functional, it was possible for the breaker to be
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misaligned so that the cell switch 'ocated in the cubicle behind the
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breaker was not engaged. The function of this cell switch is to
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close when the breaker is racked out and to open when the breaker is
racked in place.
In this case, the cell switch remained closed even
thought the breaker was racked in place. Then when the bypass breaker
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was racked out, a simila. cell switch closed tripping the turbine.
Based on the review performed by the NRC inspector, this incident
appears to be an example of an isolated personnel error.
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TheinspectorreviewedtheMarch3,jl986excessiveresponse
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time incident on the IB RTB, the sub, sequent maintenance, and the
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maintenance procedure.
This maintenance did not appear to have
any relation to the turbine / reactor trip on March 13, 1986.
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No violations or deviations were identified ir. this area,
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3.
Exit Interview
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The inspector met with licensee representatives in a telephone conference
on March 13, 1986, and summarized the purpose, scope, and findings of the
inspection.
During the inspection, the inspector discussed with licensee
personnel the likely informational content of the inspection report with
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regard to documents or processes reviewed by the inspector during the
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inspection.
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