ML17279B118

LER 88-016-00:on 880518,reactor Protection Sys Actuation Ocurred.Caused by Error in Plant Design.Event Discussed in Mechanics Shop Meeting & Article Describing Event to Be Included in Prefuelling Outage bulletin.W/880617 Ltr

ML17279B118
Person / Time
Site:	Columbia
Issue date:	06/17/1988
From:	Powers C, Washington S WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:	NRC OFFICE OF ADMINISTRATION & RESOURCES MANAGEMENT (ARM)
References
LER-88-016, LER-88-16, NUDOCS 8806220301
Download: ML17279B118 (7)

Text

REGULA I INFORMATION DISTR IBUTIOI YSTEM { RIDS)

ACCESSION NBR: 8802>220301 DOC. DATE: 88/06/17 NOTARIZED: NO DOCKET FACIL: 50-397 1'PPSS Nuclear P" o Jecti Unit 2i Washington Public Powe 05000397 AUTH. NAME AUTHOR AFFILIATION WASHINGTON S. L. W- shington Pub li c Power Supply System POWERS'. M. Washington Public Power Supply System REC IP. NAME RECIPIENT AFFILIATION

SUBJECT:

LER 88-016-00: on 880511' eactor pr otection sos actuation ocurred, Caused b'g erro" in plant design. Event discussed in Mechanics shop meeting ic article describing "event to be included in pr efuel ling outage Bulletin. W/880617 ltr.

DISTRIBUTION CODE: IE22D COPIES RECEIVED: LTR i ENCL TITLE: 50. 73 Licensee Event Report <LER) i Incident Rpt j etc.

SIZE:

NOTES:

REC I P I ENl'D COPIES RECIPIENT COPIES CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 PD5 PD 1 1 SAMWORTH R 1 I NTERNAL: ACRS MI CHELSON 1 ACRS MOELLER AEOD/DOA. AEOD/DSP/N*S 1 1 AEOD/DSP/RQAB AEOD/DSP/TPAB 1 ARM/DCTS/DAB 1 DEDRO 1 NRR/DEST/ADS 7E 0 NRR/DEBT/CEB BH 1 1 NRR/DEST/ESB BD 1 NRR/DEST/ICSB 7 1 NRR/DEST/MEB 9H 1 NRR/DEBT/MTB 9H 1 1 NRR/DEST/PSB BD 1 NRR/DEST/RSB SE 1 1 NRR/DEST/SGB SD 1 NRR/DLPG/HFB 10 1 1 NRR/DLPG/G*B 10 1 NRR/DOEA/EAB 11 1 1 NRR/DREP/RAB 10 NRR/DREP/RPB 10 2 2 N

C'e~IS/SIB 9A RES/DE/EIB 1

1 1

NUDOCS-*BSTRACT RES TELFORDi.J RES/DRPS DEPY 1

1 1

1 1

1 RGN5 FILE. Qi 1 EXTERNAL: EGi(G WILLIAMS' 4 '4 FORD BLDG HOYLE A 1 H ST LOBBY WARD LPDR 1 NRC P DR 1 1 NSIC HARRIS' 1 NSIC MAYSr G 1 TOTAL NUMBER OF COPIES REQUIRED: " LTTR 45 ENCL 44

NRC Form 366 V.S. NUCLEAR REGULATORY COMMISSION (94)3)

APPROVED 0MB NO. 3150-OIOI LICENSEE EVENT REPORT (LER) EXPIRES', 8/31/88 A

FACILITY NAME (II DOCKET NUMBER (2) PAGE 3i 0 5 0 0 0 1 OF Reactor Protection System Actuation Caused By An Average Power Range D e To Plan Desi n EVENT DATE(5) LER NUMBER (6) REPORT DATE (7I OTHER FACILITIES INVOLVED (8)

MONTH DAY YEAR YEAR SEQUENTIAL DAY FACILITYNAMFS DOCKET NUMBERISI C+) NVMBFR NUMBER MONTH YEAR 0 5 0 0 0 06 17 8 8 0 5 0 0 0 OPERATING

'THIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF 10 CFR ('I: (Checir one or more of the foriowinPI lll)

MODE IB) 20,402(B) 20AOS(cl 50.73( ~ I(2)(iv) 73.7( IBI POWER 20.405(e) (1)(l) 50.36 (c) I I ) 50.73( ~ l(2((vl ,73.71(c)

LEVEL (IOI 20.405(e l(l) (ls) 50.36(c) 12) S0,73 (~ l(2) (vii) OTHER fSoecify in Ahstrecr Oeiow endin Test, NRC Form 20.405( ~ ) ll((sil I 50.73( ~ ) (2)(l) 60,73( ~ l(2)(viill(A) 36'SAI 20AOS(el(1)(lv) 60 73(el(2) Ilil 50.73 (~ I (2 I I viii I (8) 20.40S( ~ ) ll l(vl 50.73(e l(2) I iii) 60.73( ~ I(21(el LICENSEE CONTACT FOR THIS LER (12)

NAME TELEPHONE NUMBER AREA CODE COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS. REPORT (13)

SYS'EM MANVFAC REPORTABLE MANUFAC.

CAUSE COMPONENT cAUsi SYSTEM COMPONENT TURER TO NPROS

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ACNSE.: NA 'AS v1~@,'A'Ej'.PPQWP/g

>c': ipp~gQ, @ P~',,F SUPIELEMENTAL REPORT EXPECTED (14) MONTH DAY YEAR EXPECTED SU 8 M I SS ION DATE (15)

YES fifyes, compiete EXPECTED StfffetlSSION DATEI NO ABSTRACT (Limit to te(XI soecN, i,e., enorOvimeteiy fifrren sinpie soese tynewritren finni (IBI At 0835 hours0.00966 days <br />0.232 hours <br />0.00138 weeks <br />3.177175e-4 months <br /> on May 18, 1988 a full Reactor Protection System (RPS) actuation occurred.

At the time of the event the Plant was shut down for annual refueling and maintenance.

The cause of this event is the accidental movement of a Local Power Range Monitor (LPRM) ~

cable by Plant Mechanics while removing support (Ushoot-outH) steel from the Control Rod Drive (CRD) undervessel area. Movement of the high capacitance LPRM cable caused a signal noise spike of sufficient magnitude to cause a high power trip of Average Power Range Monitor (APRM) Channel UBH which in turn tripped RPS Channel HB". At the same time Plant Instrument Technicians in a pre-planned action tripped Main Steamline, Channel UA",

Radiation Indicating Switch which tripped RPS Channel "A". Tripping both RPS channels causes an RPS actuation; however, since the Plant was shut down no actual control rod movement occurred. The "root cause" of this event'is Plant design. One hundered and seventy two LPRM cables drop through the Hshoot-outH steel in the confined CRD undervessel area and it is impossible to totally prevent accidental movement of the cables while working in the ar ea. Working conditions in the CRD undervessel area are difficult since extensive radiological protective clothing and equipment is 'required and workers must crouch because there is insufficient clearance between the Ushoot-outU steel and the CRD work platform to stand. A Plant Control Room Operator (CRO) reset the RPS.

A Plant Instrument Technician was sent to the CRD undervessel area to investigate the cause of the RPS actuation. Corrective Actions to be taken include: Discussing this event in a Mechanics Shop Meeting, and preparation of an article describing this event to be included annually in the Pre-Refueling Outage Monthly Operating Bulletin. There is no safety significance associated with this event since no actual RPS initiating conditions existed and all actuations occurred as desioned.

880b220301 880b17 PDR ADOCK 05000397 NRC Form 366 Ef v I S PDR

NRC feI>> 3EEA U$ . NUCLEAR REOULATORY COMMISSION IE43 I LICENSEE EVENT REPORT {LER) TEXT CONTINUATION APPROVED OMS NO. 3150&104 EXPIRES: 3/SI/Sl fACILITYNAME Ill OOCXET NVMSER Il) LER NVMEER Idl PACE 131 YEAR y'N'EOUENTIAL '4" IIEV<<ION NUMEEII NUM EA Ilashinoton Nuclear Plant - Unit 2 0 5 0 0 0 9 1 600 02oF TEXT /SIN<<e <<>>ce /e IedvewL v>> e4&ane/H/IC feeIII ~'e/1171 Plant Conditions a) Power Level OX b) Plant Mode - 4 (Cold Shutdown)

Event Descri tion't 0835 hours0.00966 days <br />0.232 hours <br />0.00138 weeks <br />3.177175e-4 months <br /> on the morning of May 18, 1988 a full Reactor Protection System (RPS) actuation occurred. At the time of the event the Plant was shut down for annual refueling and maintenance. No actual control rod movement occurred.

Prior to the event, at 0716 hours0.00829 days <br />0.199 hours <br />0.00118 weeks <br />2.72438e-4 months <br />, Plant Instrument Technicians began a technical specification surveillance channel calibration of the Main Steamline NChannel A" Radiation Indicating Switch (MS-RIS-610A). Performance of this surveillance causes RPS Channel "AN trips.

At 0815 hours0.00943 days <br />0.226 hours <br />0.00135 weeks <br />3.101075e-4 months <br />, two Plant Mechanics and a Plant Laborer entered the Control Rod Drive (CRD) undervessel area to remove the support ("shoot-outN) steel in preparation for changing out control rod drives during the outage. The Nshoot-outN steel limits the distance a CRD could be ejected from the Reactor Pressure Vessel (RPV) and is part of the Control Rod Drive Housing Support Structure.

At 0835 hours0.00966 days <br />0.232 hours <br />0.00138 weeks <br />3.177175e-4 months <br /> RPS Channel UAN was purposely in a tripped condition as a result of the MS-RIS-610A surveillance. Also at this time Plant Mechanics inadvertently caused a high power trip of Average Power Range Monitor (APRM) Channel NBN by accidently moving a Local Power Range Monitor (LPRM) signal cable which caused RPS Channel NB to trip. Tripping both RPS Channels causes an RPS Actuation.

Immediate Corrective Action At 0837 hours0.00969 days <br />0.233 hours <br />0.00138 weeks <br />3.184785e-4 months <br />, the Control Room Operator (CRO) reset the half scram. At 0916 hours0.0106 days <br />0.254 hours <br />0.00151 weeks <br />3.48538e-4 months <br />, the Plant Mechanics exited the undervessel area. At-1100 hours, Plant Instrument Technicians entered the CRD undervessel area to investigate. the cause of the APRM Channel NBN trip.

Further Evaluation There were no systems or components inoperable at the start of this event. which contributed to the event.

The Plant Instrument Technicians did not record the results of their May 18, 1988 undervessel inspection. Two LPRN cables that feed a signal to APRN B were repaired during the outage, but there are no records that directly tie a specific damaged cable to this incident.

NRC PORM EEEA PU.S.OPO;IQSHHIEE d3d/Edd IE431

NAC Sorm 555A U.S. NUCLEAR AEOULATOAYCOMMIS5ION 15521 LICENSEE EVENT REPORT {LER) TEXT CONTINUATION APPROVED OMS NO. 5150&104 EXPIAES: 5/51/Nl SAC ILITY NAME Ill DOCKET NUMSER Ill LKR NUMSER ISI PACK ISI VKAR SEQUENTIAL ??I REVISION NVMSKII NVM KN Washington Nuclear Pl ant - Uni t 2 0 s o 0 o 1 6 00 03 OF 0 4 TEXT ////lure N>>ce 41 IPSvlNK MPP 4IRR>>A4/IV/ICFomI 5554'4/ l 171 Further Evaluation (continued)

The cause of the event was an inadvertent and unplanned APRM B high power trip. Each APRM Channel is feed by 21 or 22 LPRMS through high capacitance signal cables which drop through the Ushoot-outU steel. Due to the high capacitance of the LPRM signal cables they are very sensitive to movement. When the Reactor Mode Switch is NOT in URunU the APRM channel high power trip is setdown to 15% thermal power and a single LPRM signal spike of 330K is enough to trip an APRM channel. Based on previous Plant experience it is known that the movement of LPRM cables can produce a signal spike of sufficient magnitude to cause an APRM channel to trip.

The "root cause" of this event is Plant Design. One hundered and seventy two LPRM cables drop through the Ushoot-outU steel in very confined conditions and it is impossible to not occasionally move a cable or even worse catch a cable in tools or equipment and give it a tug. The working conditions in the CRD undervessel area are Workers must be in radiological protective clothing among the toughest in the Plant.

and respirators or bubble suits, and work must be performed while crouching since there is not enough clearance to between the CRD work platform and the Ushoot-outU steel to stand.

An RPS actuation causes the CRD scram valves to open and if control rods had been withdrawn from the core they would have inserted.

Corrective Actions to be taken:

o There are no corrective actions which will totally prevent this problem from reoccuring in the future.

o This LER will be discussed .in a Mechanics Shop meeting.

o . The sensitivity of the Neutron Monitoring System (NMS) (includes LPRM plus Intermediate Range Monitoring System ( IRM) and Source Range Monitoring System (SRM)) cables and the 'need for extra care and caution during CRD undervessel work will be included annually in the Pre-Refueling Outage Monthly Operating Bulletin.

This event is reportable per 10CFR50.73 (a) (2) (iv). An Engineered Safety Feature actuation.

Safety Si nificance There is no safety significance associated with this event. There were no actual RPS initiating conditions, and the RPS functioned as designed. This event posed no threat to the safety of the Public or Plant personnel.

NRC POIIM 5444 I5431 4 U.S.GIIO:10550524.555/455

NRC Form 3ddA U.S, NUCLEAR REGULATORY COMMISSION (94)3)

LICENSEE EVENT REPORT {LER) TEXT CONTINUATION APPROVEO OMB NO. 3(50&(04 EXPIRES: 8/31/88 FACII.I'TY NAME (11 DOCKET NUMBER l2( LER NUMBER (5) PAGE (3)

jR(I SEQUENTIAL RgX; REVISION NUMEE A NVMEER Washington Nuclear Plant - Unit 2 o s o o o 1 6 0 0 4 OF 0 4 TEXT /// more Epeoe /I eou/ie/L uee ////ooe//V/IC %%drrn 3(ISA'4/ l17)

Similiar Events LER 85-033, this is a similar event in that Plant Laborers were spraying water in the CRD undervessel area and caused an Intermediate Range Monitor (IRM) RPS actuation due to cable movement. The corrective actions taken in LER-85-033 have been effective in preventing a similar event. The cause identified in this LER is the same (NMS cable movement), but the corrective actions identified in LER 85-033 are not applicable to this situation; EIIS Information Text Reference EIIS Reference System Component Reactor Protection System (RPS) JC Local Power Range Monitor ( LPRM) (cable) IG CBL1 Support (Ushoot-out") Steel AA SPT Control Rod Drive (CRD) Undervessel Area AA Average Power Range Monitor(APRM) IG Main Steamline Radiation Indicating Switch (MS-RIS-610A) SB RIS Control Rod AA ROD CRD Work Platform AA CRN Reactor Pressure Vessel (RPV)

Control Rod Drive Housing Support Strcuture AA SPT CRD Scram Valves AA V Neutron Monitoring System (NMS) JC CBL1 Intermediate Range Monitoring System ( IRM) JC CBL1 Source Range Monitoring System SRM JC CBL1 NRC FORM SddA e U.S GPO.(988.0 824 538/455 (94)3)

WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968 ~ 3000 George l1'ashington Way ~ Richland, 11'ashinglon 99352 Docket No. 50-397 June 17, 1988 Document Control Desk U.S. Nuclear Regulatory Commission Washington, D.C. 20555

Subject:

NUCLEAR PLANT NO. 2 LICENSEE EVENT REPORT NO.88-016

Dear Sir:

Transmitted herewith is Licensee Event Report No.88-016 for the WP-2 Plant.

This report is submitted in response to the report requirements of 10CFR50.73 and discusses the items of reportabi lity, corrective action taken, and action taken to preclude recurrence.

Very truly yours, dk4.-

C.H. Powers (H/D 927H)

NNP-2 Plant Hanager CHP:lg

Enclosure:

Licensee Event Report No.88-016 cc: Hr. John B. Hartin, NRC Region V Hr. C.J. Bosted, NRC Site (H/D 901A)

INPO Records .Center Atlanta, GA Hs. Dottie Sherman, ANI Hr. D.L. Williams, BPA (H/D 399)