ML20062D040
| ML20062D040 | |
| Person / Time | |
|---|---|
| Site: | Quad Cities  |
| Issue date: | 11/02/1990 |
| From: | Stols R COMMONWEALTH EDISON CO. |
| To: | NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM) |
| References | |
| NUDOCS 9011080105 | |
| Download: ML20062D040 (7) | |
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Common ssith Edison
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1400 Opus PI:ce Down:rs Grove. Illinois 60515 November 2,1990 U.S. Nuclear Regulatory Commission Atin: Document Control Desk l
Washington, D.C. 20555
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Subject:
Quad Cities Nuclear Power Station Unit 2 Preliminary Investigation Results of Unit 2 Reactor Scram NRC DocketRo. 50 265
Reference:
October 28,1990 Teleconference between J. Zwolinski E. Greenman (NRC), et. al.
and N.J. Kalvianakis, R.L. Bax (CECO), et. al.
t Gentlemen:
On October 28,1990 members of the Nh0's and Commonwealth Edison s staffs conducted a conference call to discuss the preliminary results of Company' Cities Unit 2 reactor sera n investigation. C!uad Cities Unit 2 tripped on the Q.uad October 27,1990 due to high neutron flux sensed by tse Intermediate Range.
Monitors (IRMs). During that conference call, the NRC staff requested that Commonwealth Edison provide a list of corrective actions that were discussed during the call.
Attached is the re prt of the preliminary investigation in response to the event. The re ort reflects the information which was gathered by the Station's initialinvest ation.
If there are any additional questions or comments please contact me at 708/515-7283.-
Sincerely, Rita Stols.
Muclear Licensing Administrator RS/Imw gg ZNLD605 CS cc:
A.B. Davis - Re 'onal Administrator, Region III R$
o J. Zwolinski - A sistant Director, NRR u
i,. E. Greenman - Division Director, Region III J. Wechselberge R. Barrett - Proj,r a OfEce of EDO ou c,
'58 ect Director, NRR W. Shafer - Branch Chief, Region III 84 i
M. Rin g - Branch Chief, Region III EE J. Hinc s Section Chief, NRR N
L. Olshan - Project Manager, NRR T. Taylor, Senior Resident Inspector, Quad Cities C. Gould AEOD-gp g/.-
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l QUAD CITIES IRICLEAR PONER STATION l
UNIT 2-
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PRELIMINAR1r INVESTIGATION of.
.INTEIDIEDIATE. RANGE DOlITOR HIGil llEUTROll FtuX SCRAM j
OCTOBER 27,-1990' l
BACKGROUND i
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. A turbine torsional L test was. scheduled to be performed on'.0ctober 27, 1990.
The purpose.of the turbine torsional test.is to verify the location of-the torsional-resonance vibrations on the' turbine' The test is. performed with 3
the reactor at power,but off the. system grid.- To' accomplish the test,
.i required.
In order to install these temporary altirations, reactor power and temporary alterations to the Electro-Hydraulic Control (EHC) system are.
l pressure are reduced.to close the turbine bypassivalves which allows the~EHC oil pumps to be secured.. Reactor power and pressure are increased after the temporary alterations are installed.
A special test procedure'was developed.to perform the torsional test.
The procedure was reviewed land approved by the. Station On-Site' Review-q Committee. Operating Engineers-were.tssigned to. perform the duties of the:
l Test Director.
The Test Director provided an overview function of the test to.
1 ensure the procedures were properly implemented..The test' team consisted of; t
Technical Staff, Operational: Analysis Department, and General. Electric _ Company representatives.
INill&LJDQlEllII0ll5 At 1500 hours0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br /> on October 27, 1990, the Unit 2 mode switch wasLin the Startup/ Hot Standby position.
Reactor pressure was: being maintained at i
approximately 920 psig by the turbine bypass valves..One.and,three-quarters bypass valves were open.
The Intermediate Range.Honitors '(IRMs)' were midscale -
on range 9 (approximately 7% of rated power).
IRM 12 was bypassed due-to-erratic behavior-(spiking) and IRN 17 was bypassed due to a depleted detector.
The drywell was deinerted.
4 EVERLDESCRIf1LON At approximately-1500 hours, the turbine. torsional test:was aborted.
The Nuclear. Station Operator (NS0) was instructed by the Shift Control. Room J
Engineer (SCRE) to decrease 1and maintain reactor: pressure at 800, psig., This-i order was given to accomodate the. removal;of the test instrumentation from:the Electro-Hydraulic Control (EHC)isystem'v51ch was installed to perform =the turbine torsional test.
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y 2-i il EYEMT DESCRIPTION (CORilM edl j
The NSO began inserting rods ('per the Control Rod _ Sequence: Package)-
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at 1500 hour0.0174 days <br />0.417 hours <br />0.00248 weeks <br />5.7075e-4 months <br />s-to reduce reactor power therebygreducing reactor pressure. <By_
l 1540 hours0.0178 days <br />0.428 hours <br />0.00255 weeks <br />5.8597e-4 months <br />, the NSO completed 14 steps of the control rod sequence which.
- l constiTdted 84 control, rod movements.
'A1.1 turbine b' pass valves were closed 1
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-by h53 hours-and reactor pressure was approximately 805'psig.
The EHC pumps-1 were subsequently secured.
The_NSO observed;that reactor 1 pressure wasy decreasing at,a higher rate than: desired.
At.1556 hours0.018 days <br />0.432 hours <br />0.00257 weeks <br />5.92058e-4 months <br />, reactor power?hadidecreasedLto.IRM1Rangelb.nALrod.-
block signal ~was present because the IRMs were on Range 11 and the Source Range) 1.
zMonttor (SRM) count, rate'was less than,100'countf per second.
TheLNSO then.-
Inserted the'SRMs. ~The insertionLof the-SRMs c N 'dctheLrod block atil557 hours. 'The.NSO(began.to withdraw controle rods at.J58' hours.
Reactore 1
i pressure was at 776 ystg and decreasing. lThe NSO withdrew four; control' rods:
by one, notch (04-00). LThe SCRE approached the:901 5: panel (reactor' control).
j just prior:to.when the NSO-withdrew control? rod G-7:from.positionLO61to;08.c Control rod G-9 (near.the center of!the-core): was Lthen selected.'
The reactor scrammed at 1559 hours0.018 days <br />0.433 hours <br />0.00258 weeks <br />5.931995e-4 months <br /> due' tch the high neutron'ffluxlsensedLby IRMs?l3:and 16 which are located close to control' rods G-7 and-G-9.~
The modeiswi?ti was j
subsequently.placed in shutdown'and procedure QGP'2-3 " Reactor Scr o" was' entered.
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IWESTIGATION 4
An investigation team was: formed to" review the' event.=lThe) Station.
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Regulatory' Assurance'SupervisorJwasiassigred the functionic*itheiteamileader.
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Members of the investigation team;lncluded two,(2); Regulatory Assurance--
h Engineers -(one who? holds a' valid =SRO;licinse), :the LeadLNuclearlEngineercthe y
Assistant Superintendent for?0perations andLthe'Ondsite/ Nuclear Safety l cEngineer'(whoreports-totheCorporateSafetytAssessment% Depart) ment)..YThe-team began their investigatten ofithe eventiat approximately?2230: hours on q
October 27, i990E ' Interviews;with'the Shift Engineer,itheLSCREJNSO-and.
Nucler Engineer weref conducted; L h4t' logs:andfprocedures(were alsoLreviewed S
as'p.rt of the investigation.
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.0nSunday; October l28,T1990Ythe_BNR'OperattbnstGensr'alManger?and!
l the Company!s:ChiefgNuclearLEngineer.reviewedjthe;resultsicf0thefStation;'s
,1 preliminary i_nvestigation.
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The17ollowing.information was bbtained by thejinvestigation team:
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.The NSO stated f. hat heidld notfrc sanize th' d h s reactor wasi L.
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subcriticaltfolloWing.the insertiontof,the i tPol rods.thQGP/2-4 " Shutdowns s
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.from P werj0peration to;a n.'ndby Hot 6Pressuritzeditoid +1on"?requiresLthat N
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<v0 contro'"rodsLshouldibeyinserted-untilithe.'eactorlis'subtritical'byUntT1 east H
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-three! control rods.
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The NSO stated-that he-was focused on controlling reactorLpressure.
3.
TheNSOstated.thathemonitoredtheIRMrecorders/metersandL1ooke'd_ati the SRM meters during the rod withdrawal..His attention was focused onithei 9
IRMs.
(During the approach to: criticality, the SRM. is the. appropriate instrus.ent to monitor.)
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- The NSO did not recognize thab he.could encounter control rods with highi notch worths.
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The NSO did not insert the SRMs perl procedure;QOPf700-1 " Source Range.
Monitoring-Operation".
Procedure QOP 700-1 directs'the:operatorJto insert, thel SRMs when the-IRMs'are on range 4, 6-The SCRE was notz involved'wlth the NS0'sl actions'after issuing the order l
to yet.uce. reactor power and pressuret 7.
We SCRE's' attention was focused on-reinerting the drywell.to avoid at vidd - of the Technical Specifications.
Thefdrywell was; required to be~
less %ai 4% oxygen by 0200 on:0ctober:28, 1990.
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'The Shitt Engineer was inithelprocess ofecompleting.hls turnover and conducting a shift-meeting with other; departments:to: discuss'the activities to:
be conducted during the shift.
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The Nuclear Engineer left the site after theitorsionaliteit was?
abor tr.d.
The Nuclear Engineer was not aware that: reactor pressureaand'powerz c
a wou19 be reduced.
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TheproceduresinvolvedintheeventwerereviewedLan'dideterminedto; j
'contain adequate'information to have prevented the; event ~
For example, the:
procedureprovidesinformationto'theoperatorthatthe'pointcofjadding' heat
~totthe. reactor lls-on IRH range 7fand that only. residual andtdecay heatcwill affect-reactor' temperature / pressure:below that' range.
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Maintainingsthe reactor. in a hot, standb,9 con'dttion ;is'part(of initial:
f license' operator' training,.hcwever, is not part of;the:Operatort Requalification Program.
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- 12.. The' Shift 11. crew reported;.expertencing:high, rod? notch porth?duringfa.
controlLrod manipulation"on October 27, 1990.- EThe.inforir..tlon"was not:
included th thefunit log' book. ~The' Shift ILN30!didl discuss the' occurrence e j
with'.the on-coming;NSO. During th'e' Shift 3 turnover,JtheiNS0'did~ rot?
J commu'nicate the information to the' on-coming NSO.-(who was. involved in; thel,
event).
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l 0011C12S10ll The investigation team'conclu6ed th'at the apparent cause of the eventL was personnel error.
The operator did'not-fully understand the condition of a
the reactor.
Additionally,othe NSO did not, fully assimilate the_information-contained in the procedure and oid_not utilize the reactor physics knowledge-which is expected of a licensed reactor operatore The operator's skill.in: maintaining the re ntor in a! hot standby.
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condition (which requires. careful-manipulation of control rods) has not been.
frequently exercised.
The NSO has:not been recentlyvinvolved in hot standby d
operation.
Furthermore, maintaining the reactor in hotJstandby.15 not, included in the Operator Requalification Program.'- Additionally, the 1
investigation team concluded thatiif the.19 formation regarding the previous shift's experienceIwlth the high notch; worth had been communicated to'the NSO'.
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-through shift turnover.or-the unit logs, tLe NSO mayLhave'been more aware'ofE potential conditions.
.i The SCRE did not provide effective oversight of the NSO',s activitt 1.
At the time of the NS0's manipulations of/the control rods, the' l
SCRE was pursuing closure of the turbine torsional' test. documentation and i
inerting of the drywell'.
The SCRE placed priority-on;the drywelliinerting to.
1 prevent.a violation of the-Technical l Specifications; =The' lack of effective:
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J communications between the NS0 ant the SCRE also contributed to the lack:of oversight.
Fct example,-the NS0's50uld have,Lat a minimum, communicated:that l
he was-inserting-the'SRMs, Improved communications between the. Nuclear 4 y
Engineer and the SCRE may have prevented the,' Nuclear Engineer from.. leaving.the j
site; thereby, additional oversight?would have:been:available to monitor the?
manipulatin of rods by the NSO.
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.RL8C10lLPIREONMCELS6FETY SIGNIFICANCE 1
The purpose of theLIRMs115'to montfor, neutron l flux:and to initiate a-reactor scram in the'eventrof h1'gh. neutron flux;.Duringithis: event,ithe IRMsi performed as' expected. LThe minimum. required operable IRMs1were 'availablei for the. Reactor Protection Systam.
'IRM 12 wasib' passedj on RPS; Channel A-'and-IRM-17 was bypassed on.RPS B.l
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An analysis Nas performed by the: Nuclear l Fuel Services Department on R
the reactivity:worthLof the control' rods:that resulted in'the power' increase.
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The-analysis demonstrated that: the ' worth of.theLcontrol Lrods.was;not-greater than expected andl sufficient to createJthe resulting' power?lncrease.
The l
onsite.nucleartengineering group; verified thathcorelreactivit9 was'wlthin the:
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. Technical Specification limitstbyTevaluationjof the, critical rod pattern +
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duringhtheLsubsequent criticallty.! LThese analyses"and~ verification d
demonstrate"thatL the core is not; behaving Janomlously.
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5-CORRECILYLACIl0NS Following the completion of the preliminary investigation, members of the team, Ctation-and Corporate Management developed the following corrective actions:
1.
An in-depth' discussion was. conducted with the members;ofithe crew invohd in the event.
The-discussion included members of upper Station-management, the Chief Nuclear Engineer; and the.BWR Operations General =
Hanagor. A presentation lof the event-sequence, the investigation,results and:
discussions with the-NRC was provided to the: crew-members. cThe: crew was requested to provide comments asito the accuracy of the' facts surrounding the event.
This was conducted'on:0ctober 28, 1990.
2.-
Prior to assuming their shift duties,,each operating crew was' briefed on-this event by upper-Station management. During these briefings, the-need for effective communication'and the SCRE oversight; function were stressed.
3.
Additional management oversight:(an Operating Engineer)-was: assigned to the crew involved in this event until remedial training'was' completed.
4.
The crew involved in this event received remedial 1 training on operating-the unit in hot standby mode.
The training consisted'of-~ classroom.andt simulator training.
The training included discussionsiof teamwork,c...
communications and procedural compliance.
Hednesday, October 31, 1990.
This training was completed on-5.
Specific training on maintaining the reactor in! hot standby will be-provided in the Licensed,Requalification Program.
The training willjinclude:
reactivity management specific to this mode of operation..-Training w1_111be.
conducted for all: license operators'duringcthe nextitraining-cycle.
6.
This-event will =be included liboth the :" Lessons : Learned" portion of the operator retraining class as~well as required reading.
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7.
Nuclear Engineers will be required,to attend 6the " Lessons l Learned
portion of the operator retraining class when'this event /is: discussed.- Also, d
Huclear Engineers lwill be required to attend the simulator portion'of.the' hot standby operation training.
the event that hot standby operation 11s, operatein the hot standby mode. 'In..
8.
The Station will not deliberately required due to plant conditions, augmented management oversight will be provided to'all _ crewsLuntil' training is'-
completed.
9.
The procedure for operating in'the Startup/ Hot' Standby mode will;be; enhanced'tased on the lessonsDiearned from:this event.
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t EQBRfCTIVE ACTLQQtS (contlDutdl "i
10.
. Nuclear. Fuel Services will conduct i, self assessment ofireactivity' management-training to' identify any potential weaknesses.c Appropriate; actions.
will be' implemented in; response to_this review.
11.
An. Independent and' :in-depth investigation-of: the: event is being ~.
conducted to augment-the preliminary investigation conducted by-the Station.-
The purpose of the. augmented review is;to ensureia' thorough investigation of.
the event. The investigation _ will-reviewL the event ~ andifocusi on.
procedures / procedural adherence, control and command of the Control Room,'
preparation for;special tests,1and-communications',: including operatingLlogsL
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and1 turnover. 1The conclusions: reached by the corporatetinvestigation;will;be' reviewed for.-potential', application lto other; CECO' sites..
12.
.The Company Directive'fo*.iuclear Eng'ineer. overview willLbe reviewed.- -
Enhancements to the-programi.,ii be implemented,Jas' appropriate.
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