IR 05000295/1986008: Difference between revisions

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{{Adams
{{Adams
| number = ML20212K962
| number = ML20210E246
| issue date = 08/18/1986
| issue date = 03/24/1986
| title = Forwards Safety Evaluation of Util Use of Negative Flux Rate Trip of -15% Power in 5 Vs -5% Power in 2 S,Per LER 50-295/86-008.Task Initiation Action 86-25HT Closed
| title = Insp Rept 50-295/86-08 on 860312-13.No Violation or Deviation Noted.Major Areas Inspected:Plant Trips
| author name = Novak T
| author name = Muffett J, Westberg R
| author affiliation = NRC OFFICE OF NUCLEAR REACTOR REGULATION (NRR)
| author affiliation = NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
| addressee name = Paperiello C
| addressee name =  
| addressee affiliation = NRC OFFICE OF INSPECTION & ENFORCEMENT (IE REGION III)
| addressee affiliation =  
| docket = 05000295, 05000304
| docket = 05000295
| license number =  
| license number =  
| contact person =  
| contact person =  
| document report number = NUDOCS 8608250148
| document report number = 50-295-86-08, 50-295-86-8, NUDOCS 8603270289
| document type = INTERNAL OR EXTERNAL MEMORANDUM, MEMORANDUMS-CORRESPONDENCE
| package number = ML20210E241
| document type = INSPECTION REPORT, NRC-GENERATED, INSPECTION REPORT, UTILITY, TEXT-INSPECTION & AUDIT & I&E CIRCULARS
| page count = 3
| page count = 3
}}
}}
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. J August 18, 1985 DISTRIBUTION MEMORANDUM FOR:  Carl J. Paperiello, Director  7~ Docket File f Division of Reactor Safety  "' NRC'PDR~ '
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Region III  Local PDR PD#3 Rd FROM:  Thomas M. Novak, Acting Director  C. Rossi Division of PWR Licensing-A  J. Norris C. Vogan SUBJECT:  REQUEST FOR ASSISTANCE - ZION NEGATIVE FLUX  Tech Branch RATE TRIP (AITS F03020686) (TIA No. 86-25HT)
U.S. NUCLEAR REGULATORY. COMMISSION
By memorandum dated May 6, 1986, Region III requested technical assistance to determine the safety significance of Zion's use of a negative flux rate trip of-15% power in five seconds versus the setpoint established by the dropped rods safety analysis of -5% power in two seccads. The issue relates to LER 295/86-008. The results of our analysis are contained in the enclosed Safety Evaluatio This memorandum closes AITS F03U20686 (TIA No. 86-25HT).


Original signed by:
==REGION III==
Thomas M. Novak, Acting Director Division of PWR Licensing-A Enclosure:
Report No. 50-295/86008(DRS)
As stated f   /
-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/ M Date
PD#3 ed l PD(3  3  -A:Ac CVogan s  a v 'ik (JNor 8/g4/86 8/q/86 /86 8 ' /8 k I40 G/> Oats  .
  % CL W Approved By: J. W. Muffett, Chi   b/z4 /gg Plant Systems Section Date Inspection Summary Inspection on March 12-13, 1986 (Report No. 50-295/86008(ORS))
s ;CK 05000295      .
Areas Inspected: Routine, announced inspection by one regional inspector of plant trips - safety system challenge It was conducted in accordance with NRC Inspection Procedure No. 9370 Results: No violations or deviations were' identifie e60324 PDR O ADOCK 05000295 PDR
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FDR
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. . . . . . . .
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DETAILS 1. Persons Contacted Conro nweal th_E_d i s on Compa ny_( C Ecol
'
  * Plim1, Station Manager
*E. Fuerst, Superintendent Production
  *W. Stone. Quality Assurance Supervisor
  *A. Amoroso, Technical Staff Group Leader, Electrical M. Bailey, Technical Staff Engineer USNRC
  *J. Kish, Resident Inspector
  * Indicates those attending the exit meeting on [[Exit meeting date::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 with involved personnel, and inspection of the IB reactor trip breaker (RTB). Documents Reviewed (1) Maintenance Procedure No. E015-1, " Reactor Trip Breaker Maintenance," Revision (2) Test Procedure No. PT-5, " Reactor Protection Logic,"
Revision 14 (3) Schematic Diagram No. 22E-1-4884, " Reactor Trip Switchgear Breaker," Revision 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 late The inspector inspected the IB RTB and the switchgear cubicl 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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  :   SAFETY EVALUATION OF OPERATION WITH A NONCONSERVATIVE NEGATIVE FLUX RATE TRIP SETPOINT
  ,
.
A misaligned so that the cell switch 'ocated in the cubicle behind the
,
breaker was not engaged. The function of this cell switch is to i  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
:
'
'
AITS F03020686
thought the breaker was racked in place. Then when the bypass breaker was racked out, a simila. cell switch closed tripping the turbin Based on the review performed by the NRC inspector, this incident appears to be an example of an isolated personnel error.
.
 
Introduction By letter dated May 6,1986 to H. L. Thompson from C. J. Paperiello Region III requested assistance on the Zion Negative Flux Rate Trip Issue (AITS F03020686). Both Zion Units operated with the Negative Flux Rate Trip (NFRT)
!
set nonconservatively, at a value of -15% power in 5 seconds rather than the correct value of -5% power in 2 seconds, from November 1979 to February 1986.
TheinspectorreviewedtheMarch3,jl986excessiveresponse
.
time incident on the IB RTB, the sub, sequent maintenance, and the
!  maintenance procedure. This maintenance did not appear to have i  any relation to the turbine / reactor trip on March 13, 1986.
 
i  No violations or deviations were identified ir. this area, i Exit Interview i
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 i  regard to documents or processes reviewed by the inspector during the j  inspection.


; This is delineated in LER 295/86-008 which was furnished with the referenced letter. Because of the complicated nature of the rod drop issue, we will d'scuss some of the ramifications of the event, as well as the central issue r the safety significance of the nonconservative NFRT setpoin Evaluation As a result of a meeting between Westinghouse and NRC on November 19, 1979, an interim solution was adopted to resolve deficiencies in the safety analysis of the rod drop transient. The interim solution required that manual control be used whenever rods were withdrawn less than 216 steps with the reactor power greater than 90% and that the NFRT be set for a -5% in 2 seconds rate tri The requirement for the trip was not made clear as a result of the meeting, although recent discussions with Westinghouse indicate the trip requirement was always in effec There were two concerns with the rod drop accident: The first is a return to i power if the reactor is in automatic control with a dropped rod. This can
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result in the Departure from Nucleate Boiling Ratio (DNBR) falling below the design limits. The scenario requires a failure in the nuclear instrumentation system auctioneering module such that the channel which monitors the quadrant of reduced flux is feeding the automatic rod controller rather than the highest signal. The interim methodology prevented this. The second concern is if the worth of the dropped control rod or rods is high. In that case, if the reactor does not trip there may be a DNBR proble The interim solution for rod drep acciderts was replaced May 13, 1983 when we accepted a new rod drop methodology presented by Westinghouse. The negative flux rate trip requirements remained the same. Since Zion Units 1 and 2 had adopted use of the interim solution in November 1979 and replaced it with the new methodology for Unit 2 on May 30, 1983, and for all subsequent reloads on both units, the reactors have been protected from the return to power concern for rod drop _ _ _ _ _ _ _ _ _ _ _ _ _ _
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The problem area lies with the concern for control rod drops with high wort The negative rate trips at Zion 1 & 2 were set nonconservatively from the time a concern with the rod drop analysis was identified in November 1979 until the nonconservative calibration was discovered and corrected in February 1986. The-15% in 5 second NFRT, according to LER 295/86-088, assures a reactor trip for
!
.uJ J...r. with a worth greater than approximately 800 pcm. The -5% in 2 seconds NFRT assumes a trip occurs for all rods with worths greater than 400 pcm. Therefore if a drop of control rods worth more than 400 pcm and less than 800 pcm had occurred in either Zion Unit during the period November 1979 to February 1986 the results would have tad unanalyzed consequences. We cannot define the extent of what would occur under these unanalyzed conditions, but must assume that a departure from nucleate boiling would occur, with some enne.nnent fuel failure. The rod drop event is considired an anticipated transient, and fuel failure is an unacceptabe consequence for such events.
:
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}}

Revision as of 09:25, 4 December 2021

Insp Rept 50-295/86-08 on 860312-13.No Violation or Deviation Noted.Major Areas Inspected:Plant Trips
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)
v • d • e


Text

.

.

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/ M Date

% CL W Approved By: J. W. Muffett, Chi b/z4 /gg 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 challenge It was conducted in accordance with NRC Inspection Procedure No. 9370 Results: No violations or deviations were' identifie e60324 PDR O ADOCK 05000295 PDR

.

.

DETAILS 1. Persons Contacted Conro nweal th_E_d i s on Compa ny_( C Ecol

'

  • Plim1, Station Manager
  • E. Fuerst, Superintendent Production
  • W. Stone. Quality Assurance Supervisor
  • A. Amoroso, Technical Staff Group Leader, Electrical M. Bailey, Technical Staff Engineer USNRC
  • J. Kish, Resident Inspector

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 with involved personnel, and inspection of the IB reactor trip breaker (RTB). Documents Reviewed (1) Maintenance Procedure No. E015-1, " Reactor Trip Breaker Maintenance," Revision (2) Test Procedure No. PT-5, " Reactor Protection Logic,"

Revision 14 (3) Schematic Diagram No. 22E-1-4884, " Reactor Trip Switchgear Breaker," Revision 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 late The inspector inspected the IB RTB and the switchgear cubicl 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

.. . - . - - _ . . . - -. . _- . . -

,

.

A misaligned so that the cell switch 'ocated in the cubicle behind the

,

breaker was not engaged. The function of this cell switch is to i 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 was racked out, a simila. cell switch closed tripping the turbin Based on the review performed by the NRC inspector, this incident appears to be an example of an isolated personnel error.

!

TheinspectorreviewedtheMarch3,jl986excessiveresponse

.

time incident on the IB RTB, the sub, sequent maintenance, and the

! maintenance procedure. This maintenance did not appear to have i any relation to the turbine / reactor trip on March 13, 1986.

i No violations or deviations were identified ir. this area, i Exit Interview i

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 i regard to documents or processes reviewed by the inspector during the j inspection.

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