ML17311B199

LER 95-010-00:on 950727,equipment Qualification of Air Handling Unit Caused Essential Cw Pump to Be Inoperable. Used Work Orders to Drill Weep Holes in Motor Lead Connection boxes.W/950921 Ltr

ML17311B199
Person / Time
Site:	Palo Verde
Issue date:	09/21/1995
From:	Grabo B, James M. Levine ARIZONA PUBLIC SERVICE CO. (FORMERLY ARIZONA NUCLEAR
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
102-00948-JML-B, 102-948-JML-B, LER-95-010, LER-95-10, NUDOCS 9509260109
Download: ML17311B199 (18)

Text

PRXORXTX 1 (ACCELERATED RIDS PROCESSING) fv REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9509260109 DOC.DATE: 95/09/21 NOTARIZED: NO DOCKET' FACIL:STN-50-528 Palo Verde Nuclear Station, Unit 1, Arizona Publi 05000528

. AUTH. NAME'AUTHOR AFFILIATION GRABO,B.A. Arizona Public Service Co. (formerly Arizona Nuclear Power LEVINE,J.M. Arizona Public Service Co. (formerly Arizona Nuclear Power RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 95-010-00:on 950727,equipment .qualificati'on of air handling unit caused essential CW pump to be inoperable. 0 Used work orders to drill weep holes zn motor lead connection boxes.W/950921 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:

TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:STANDARDIZED PLANT 05000528 T

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD4-2 PD 1 1 HOLIAN, B 1 1 TRAN,L 1 1 INTERNAL: ACRS 1 1 OD/S RD/RAB '2 2 AEOD/SPD/RRAB 1 1 CONTE~ 1

'1 1

NRR/DE/ECGB 1 1 NRR/DE/EELB 1 NRR/DE/EMEB 1 1 NRR/DISP/PIPB 1 1 D' NRR/DRCH/HHFB 1 1 NRR/DRCH/HICB, 1 1 NRR/DRCH/HOLB 1 1 NRR/DRPM/PECB 1 1 NRR/DSSA/SPLB 1 1 NRR/DSSA/SPSB/B 1 1 NRR/DSSA/SRXB 1 '1 RES/DSIR/EIB 1 1 RGN4 FILE, 01 1 1 EXTERNAL: L ST LOBBY WARD 1 LITCO BRYCE,J H 2 2 NOAC MURPHY,G.A 1 1 NOAC POORE,W. 1 1 NRC PDR 1 1 NUDOCS FULL TXT 1 1 E.

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PLEASE HEL'P US TO REDUCE WASTE! CONTACT THE'OCUMENT CONTROL DESK, ROOM OWFN 5D8 (415-2083) TO ELIMINATE YOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DONeT NEED)

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Arizona Public Service Company PALO VERDE NUCLEAR GENERATING STATION P.O. BOX 52034 ~ PHOENIX, ARIZONA 85072-2034 192-00948-JML/BAG/BE JAMES M. LEVINE September 21, 1995 VICE PRESIDENT NUCLEAR PRODUCTION U. S. Nuclear Regulatory Commission ATTN: Document Control Desk Mail Station P1-37 Washington, DC 20555-0001

Subject:

Palo Verde Nuclear Generating Station (PVNGS)

Unit1 Docket No. STN 50-528 (License No. NPFQ1)

Licensee. Event Report'95-010-00 Attached please find Licensee Event Report (LER) 95-010-00 prepared and submitted pursuant to 10CFR50.73. This LER reports a condition where equipment qualification of an air handling unit (AHU) caused the Train A Essential Cooling Water pump to become inoperable. This resulted in the following Train A systems becoming inoperable: Essential Chilled Water, Emergency Core Cooling, Containment Spray, Control Room Essential Filtration, Shutdown Cooling, and the Train A Auxiliary Feedwater pump.

In accordance with 10CFR50.73(d), a copy of this LER is being, forwarded to the Regional Administrator, NRC Region IV. If you have any questions, please contact Burton A. Grabo, Section Leader, Nuclear Regulatory Affairs, at (602) 393-6492.

Sincerely,

/L(

JM L/BAG/BE/pv Attachment cc: L. J. Callan (all with attachment)

K. E. Perkins K. E. Johnston INPO Records Center CQ' 9509260109 'TI5092i PDR ADOCK 05000528 S PDR

')I LICENSEE EVENT REPORT (LER ACIUTYNAME (1) DOCKET NUMBER (2) PAGE (3)

Palo Verde Unit 1 p 5 p p 0 5 2 8 1 o" 0 7 TLE (4)

Equipment Qualification of air handling unit causes Essential Cooling Water pump to become inoperable EVENT DATE 6 LERNUMBER 6 REPORT DATE 7 OTHER FACIUTIES INVOLVED 6 MONfH DAY YEAR YEAR i'gb SEQUENTIAL I@ REVISION MONTH FACIUTYNAMES KET NUMBERS NUMBER N/A 0 7 2 7 9 5 9 5 0 1 0 0 0 0 9 2 1 9 5 N/A OPERATING HIS REPORT IS SUBMITTED PUR UANT TO THE REQUIREMENTS OF 10 CFR E: (Check one or more of the foaoweo) (11)

MODE (6) 20.402(b) 20.405(c) 50.73(s)(2)(rv) 73.71(b)

POWER 20.405(a)(1)(i) 50.36(c)(1) 50.73(s)(2)(v) 73.71(c) 20.405(s)(t)(S) 50.36(c)(2) 50.73(s)(2)(vs/ OTHER (Specify in Abstract LEvEL(to) 1 p p 20.405(a)(1)($ ) 50.73(s)(2)(i) 50.73(a)(2)(vE)(A) bekxw snd in Text, NRC Fom 20.405(s)(1)(iv) 50.73(s)(2)(ii) 50.73(s)(2)(vE)(B) 20.405(a)(1)(v) 50.73(a)(2)(is' 50.73(s)(2)(x)

LICENSEE CONTACT FOR THIS LER (12)

E ELEPHONE NUMBER EA CODE Burton A. Grabo, Section Leader, Nuclear Regulatory Affairs 6 0 2 3 9 3 - 6 4 9 2 COMPLETE ONE UNE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFAC- REPORTABLE CAUSE SYSTEM COMPONENT MANUFAC TURER TO NPRDS TURER

<,?4 's.,'.: ".

SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED MONTH DAY YEAR SUBMISSION YES (If yes, complete EXPECTED SUBMISSION DATE) NO DATE (15)

BsTRAOT (Lena to 1400 spaces, l.e.. epproxsnstely frlteen seoieepace typewntten lees) (16)

On July 27, 1995, at approximately 0830 MST, Palo Verde Unit 1 was in Mode 1 (POWER OPERATION), operating at approximately 100 percent power, when APS System Engineering personnel (utility, nonlicensed) identified that the air handling unit (AHU) motor for the Train A Essential Cooling Water (EW) pump room would not remain operable during a high energy line break (HELB) due to submergence of the Raychem splice in the motor lead connection box (MLCB).

The cause of the event was attributed to personnel error in the 1991 evaluation of IEN 89-63. The error was misinterpreting the definition of terminal box as applying to all enclosures and concluding that weep holes were in all enclosures including MLCBs.

On July 27, 1995, weep holes were drilled in the AHU's motor lead connection boxes, the Train A EW pump room AHU motors in all three units were now in a qualified condition, and the EW pumps were declared operable. By December 31, 1995, corrective maintenance will be completed on all sixty-six components (total, all three units) to prevent moisture accumulation in the end device.

There have been no previous similar events reported pursuant to 10CFR50.73.

0 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION AGILITY NAME DOCKETNUMBER LER NUMBER PAGE SEQUENTIAL ~~~/ EVISIO YEAR eI NUMBER NUMBER Palo Verde Unit 1 0 5 0 0 0 5 2 8 9 5 0 1 0 0 0 0 2 of 0 7

1. REPORTING REQUIREMENT:

This LER 528/95-010-00 is being written to report a condition where a single condition caused at least one independent train or channel to become inoperable in multiple systems as specified in 10 CFR 50. 73 (a) (2) (vii) .

Specifically, at approximately 0830 MST on July 27, 1995, Palo Verde Unit 1 was in Mode 1 (POWER OPERATION), operating at approximately 100 percent power when APS System Engineering personnel (utility, nonlicensed) identified that the air handling unit (AHU) motor for the Train A Essential Cooling Water (EW)(BZ) pump room would not remain operable (all three units) during a high energy line break (HELB) due to submergence of the Raychem splice in the motor lead connection box.

2. EVENT DESCRIPTION:

On May 17, 1991, APS Nuclear Assurance personnel (utility, nonlicensed) identified inconsistencies between the results of the original pressure-temperature calculations for a HELB and the environmental qualification (EQ) design requirements provided in the Updated Final Safety Analysis (UFSAR) .

Zn order to resolve the identified EQ concerns, APS'uclear Engineering (NED) personnel (utility, nonlicensed) performed calculations 13-NC-ZA-211, rev 0, 13-NC-ZA-212, rev 0, and 13-NC-ZA-213, rev 0. These calculations provide temperature-pressure-humidity versus time histories for the Auxiliary Building (AB)(NF) and adjacent compartments in the Main Steam Support Structure (MSSS)(NM) following a postulated auxiliary steam (SA) line break or reactor coolant system (RCS)(AB) letdown line break.

The calculations used the multi-compartment, time dependent, thermal hydraulics code PCFLUD version 3.1. Study 13-MS-A69 showed that critical safe-shutdown equipment would survive a postulated HELB in the AB. (The calculations and study were the basis for the environmental parameters in the AB during a HELB and were used for APS'Q Program Manual.)

During this time frame APS was evaluating IE Notice (1N) 89-63, "Possible Submergence Of Electrical Circuits Located Above The Flood Level Because Of Water Intrusion And Lack of Drainage," for applicability to APS. On June 28, 1991, APS Procurement Engineering (PED) personnel (utility, nonlicensed) determined that APS's design basis as specified provides

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LICENSEE EVENT REPORT (LER) TEXT CONTINUATION AGILITYNAME DOCKET NUMBER PAGE LER NUMBER YEAR: 4 SEQUENTIAL ~:, EVISIO NUMBER 'jap~

NUMBER Palo Verde Unit 1 0 5 0 0 0 5 2 8 9 5 0 1 0 0 0 0 3 of 0 7 EXT necessary provisions for drainage, sealing, and weep holes. As such, the submergence concerns identified by 1N 89-63 were addressed during the initial design and construction phase of Palo Verde. This evaluation misinterpreted the definition of terminal box as applying to all enclosures and concluding that weep holes were in all enclosures.

As a follow-up action to the 1991 EQ audit and as a part of the EQ Enhancement Project, walkdowns of all EQ electrical components in the AB and MSSS were performed. On September 3, 1993, EQ Engineering personnel (utility, nonlicensed) questioned the lack of "T" drains installed on Limitorque motor operated valves (MOVs) and if weep holes are required in all junction boxes regardless of location. On January 4, 1994, study 13-ES-A23 was completed and reviewed a total of 1470 EQ installations (all three units) . Of these installations 695 were recommended for modification to ensure proper condensate drainage. Study 13-ES-A23 identified that a 0.125 inch weep hole needed to be added to the motor lead connection box for the AHU in the Train A EW pump room (all three units) to ensure proper condensate drainage.

Study 13-ES-A23 defined the optimum configuration for conduit to ensure proper condensate drainage. The study did not determine if condensation would occur or quantify the amount of condensation that would develop as a result of a HELB. A new calculation was initiated to determine the amount of condensation and determine if the recommendations in Study 13-ES-A23 were warranted.

On June 9, 1995, a new analysis (13-MC-ZA-202, rev 0) was completed that provided a more realistic prediction of the environmental parameters in the AB as a result of the postulated HELB. Also, this calculation provided a quantitative analysis of condensation in conduits to be used in conjunction with study 13-ES-A23 and plant walkdowns. This calculation was performed using PCFLUD version 3.7. PCFLUD version 3.1 did not have the capability of modeling as many compartments as allowed in version 3.7.

Calculations 13-NC-ZA-211 and 212 over-predicted the amount of pressure that would be expected as a result of the RCS letdown and auxiliary steam line breaks. This was conservative for the purpose of qualifying equipment or for subcompartment structural design basis; however, it was not conservative for the assumption when the isolation of an auxiliary steam line break would occur.

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LICENSEE EVENT REPORT (LER) TEXT CONTINUATION AGILITYNAME DOCKET NUMBER PAGE LER NUMBER YEAR i::w";": SEQUENTIAL I~i'~I EVISIO NUMBER NUMBER Palo Verde Unit 1 0 5 0 0 0 5 2 8 9 5 0 1 0 0 0 0 4 of 0 7 EXT An evaluation of the impact of this new calculation and plant walkdowns were commenced. Study 13-QS-A03 documented the walkdown results and was able to reduce the 695 components identified in Study 13-ES-A23 as needing modification to sixty-six components (total all three units). On July 27, 1995, it was determined that the essential AHU motor for the Train A EW pump room would not remain operable during a HELB.

The essential AHU is required to ensure that the EW pump remains operable under accident condition heat loads. Therefore, with the essential AHU inoperable, the EW pump was declared inoperable on July 27, 1995. The EW pump provides cooling water to the essential chilled water (EC)(KM) and shutdown cooling (SDC)(BP) heat exchangers. With the Train A EW pump inoperable, the Train A EC and SDC heat exchangers were inoperable.

This resulted in the Train A high pressure safety injection (HPSI)(BQ),

low pressure safety injection (LPSI)(BP), containment spray (CS)(BE),

auxiliary feedwater (AF) (BA) pumps, and control room essential filtration becoming inoperable.

On August 21, 1995, this condition was reviewed by APS Nuclear Regulatory Affairs personnel (utility, nonlicensed) and was determined to be reportable.

3. ASSESSMENT OF THE SAFETY CONSEQUENCES AND THE IMPLICATIONS OF THIS EVENT:

The EW System is a closed-loop system which acts as a buffer between contaminated or potentially contaminated components and the Essential Spray Pond (SP)(BS) System. The EW system consists of two separate, independent, redundant, safety-related flow trains. One is designated Train A and serves Safety Train A equipment, and the other is designated Train B and serves Safety Train B equipment. Either flow train can supply sufficient cooling water to allow a safe plant shutdown independent of the other flow train.

The heat loads normally supplied by the EW System are the EC and SDC heat exchangers. The EC system supplies chilled water to the essential air cooling units (ACUs) and AHUs in the Control and Auxiliary Buildings during essential equipment operation. The EC System consists of two 100 percent capacity, redundant, safety-related flow trains (Train A and Train B) which cannot be cross-connected.

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION ACIMTYNAME DOCKET NUMBER LER NUMBER PAGE i'4?': SEQUENTIAI K~><< EVISIO Palo Verde Unit 1 0 5 0 0 0 5 2 8 9 5 0 1 0 0 0 0 5 of 0 7 EXT The loss of the AHU motor for the Train A EW pump room during a postulated HELB would not have significantly compromised plant safety. A second 100 percent capacity independent, redundant, safety-related flow train (Train B) would be operable during a postulated HELB for the safe operation of the plant.

A HELB accident has not occurred at PVNGS; therefore, this event did not result in any challenges to the fission product barriers or result in any releases of radioactive materials. This event did not adversely affect the safe operation of the plant or the health and safety of the public.

A probabilistic risk assessment (PRA) was performed to evaluate the pipe rupture frequency associated with a failure of the RCS letdown line and auxiliary steam line. The failure frequencies were 1.5 E-4/yr and 3.8 E-5/yr (RCS letdown and auxiliary steam line respectively). Based on the low frequency for occurrence of a pipe rupture, from a probabilistic perspective, there was a negligible safety risk associated with the Train A EW essential AHU being inoperable.

4. CAUSE OF THE EVENT:

An independent investigation of this event is being conducted in accordance with the APS Corrective Action Program. Based on the results of the independent investigation to date, the cause of the Train A AHU becoming inoperable during a postulated HELB was the inability to isolate an auxiliary steam line break within 60.78 seconds since the predicted pressures are lower than the current pressure sensors setpoint and the lack of weep holes to prevent excessive accumulation of moisture. The misinterpretation of the definition of terminal box as applying to all enclosures including MLCBs and the lack of plant walkdowns did not ensure that condensation would not collect in the end devise (SALP Cause Code A:

Personnel Error). The design drawing did not specify weep holes in MLCBs. Therefore, this assumption resulted in a missed opportunity to ensure that the original design was sufficient during a HELB.

No unusual characteristics of the work location (e.g., noise, heat, poor lighting) directly contributed to this event.

0 LICENSEE EVENT REPORT (LER) TEXT CONTINUATION AC IUTY NAME DOCKET NUMBER LER NUMBER PAGE YEAR SEOUENIIAI. EVISIO NUMBER NUMBER Palo Verde Unit 1 0 5 0 0 0 5 2 8 9 5 0 1 0 0 0 0 6 of 0 7 5 ~ STRUCTURE, SYSTEM, OR COMPONENT INFORMATION:

Although the Train A EW pump was declared inoperable because the EQ of the pump room's AHU motor could not be assured during a postulated HELB, there were no component or system failures involved in this event. No failures of components with multiple functions were involved. No failures that rendered a train of safety system inoperable were involved. There were no safety system responses and none were necessary.

6. CORRECTIVE ACTIONS TO PREVENT RECURRENCE:

On July 27, 1995, work orders were used to drill weep holes in the motor lead connection boxes and the Train A EW pump room AHU motors (all three units). The corrective maintenance on the AHUs qualified the AHUs, all equipment was declared operable and their associated TS LCOs were exited.

On August 3, 1995, a Justification for Continued Operation (JCO) was approved by the Plant Review Board (PRB). Twenty-nine components were identified by the JCO that needed corrective maintenance to prevent moisture in the AB conduit system following a postulated HELB. This JCO only addressed Unit 1 concerns until walkdowns could be completed in Units 2 and 3.

On August 18, 1995, a JCO was approved by the PRB. Sixty-six components were identified by the JCO that needed corrective maintenance to prevent moisture in the AB conduit system following a postulated HELB (29 Unit 1, 22 Unit 2, and 15 Unit 3).

By October 20, 1995, an action plan will be developed for completing the required work on all sixty-six components (total, all three units) to prevent moisture accumulation from submerging EQ components.

A design change evaluation for isolation of the auxiliary steam line break within 60.78 seconds is proposed to be completed by December 30, 1995.

Actions required from the above investigations will be tracked by Action Tracking System (CATS) . If the evaluation results APS'ommitment if differ from this determination or information is developed which would affect the readers understanding or perception of this event, a supplement to this report will be submitted.

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LICENSEE EVENT REPORT (LER) TEXT CONTINUATION ACILITYNAME DOCKET NUMBER LER NUMBER PAGE YEAR SEQUENTIAL j+gp, EVISI0 NUMBER g~+j NUMBER Palo Verde Unit 1 0 5 0 0 0 5 2 8 9 5 0 1 0 0 0 0 7of0 7 EXT PREVIOUS SIMILAR EVENTS:

There have been no previous similar events reported pursuant to 10CFR50.73 in the last three years attributed to personnel error resulting EQ problems. A voluntary LER 528/94-003 was written because the high voltage Raychem heat shri:nkable motor splice kit installation instructions did not ensure that the ribbon adhesive would thoroughly melt with each application, potentially impacting a uniform moisture seal. Corrective actions taken for the previous event would not have prevented this event.

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