ML17289A411

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LER 92-025-01:on 910911,Train a of Containment Atmosphere Control Sys Rendered Inoperable.Caused by Less than Adequate Procedures for Reassembly of Blower.Lockwires Have Been Installed on Drain plugs.W/920318 Ltr
ML17289A411
Person / Time
Site: Columbia Energy Northwest icon.png
Issue date: 03/20/1992
From: John Baker, Fies C
WASHINGTON PUBLIC POWER SUPPLY SYSTEM
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
GO2-92-065, GO2-92-65, LER-92-025, LER-92-25, NUDOCS 9203250329
Download: ML17289A411 (7)
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Text

ACCELERATED DISTRIBUTION DEMONSTR TION SYSTEM REGULATORY INFORMATION DISTRIBUTION SYSTEM (RIDS)

ACCESSION NBR:9203250329 DOC.DATE: 92/03/20 NOTARIZED: NO DOCKET I FACIL:50-397 WPPSS Nuclear Project, Unit 2, Washington Public Powe 05000397 AUTH. NAME AUTHOR AFFILIATION FIES,C.L. Washington Public Power Supply System BAKERIJ.W. Washington Public Power Supply System RECIP.NAME RECIPIENT AFFILIATION

SUBJECT:

LER 92-025-01:on 910911,a train of containment atmosphere control sys rendered inoperable. Caused by less than adequate procedures for reassembly of blower.Lockwires have been installed on drain plugs.W/920318 ltr.

DISTRIBUTION CODE: ZE22T COPIES RECEIVED:LTR I ENCL ( SIZE:

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

NOTES:

RECIPIENT COPIES RECIPIENT COPIES ID CODE/NAME LTTR ENCL ID CODE/NAME LTTR ENCL PD5 LA 1 1 PD5 PD 1 1 ENGiP.L. 1 1 INTERNAL: ACNW 2 2 ACRS 2 2 AEOD/DOA 1 ( 1 AEOD/DSP/TPAB 1 1 AEOD/ROAB/DSP 2 2 NRR/DET/EMEB 7E 1 -

1 NRR/DLPQ/LHFB10 1 1 NRR/DLPQ/LPEB10 1 1 NRR/DOEA/OEAB 1 1 NRR/DREP/PRPB11 2 2 NRR/DST/SELB 8D 1 1 NRR/DST/SICB8H3 1 1 NR~~ LB8D1 1 1 NRR/DST/SRXB 8E 1 1 EG E 02 1 1 RES/DSIR/EIB 1 1 RGN5 FILE 01 1 1 EXTERNAL 'G&G BRYCE E J ~ H 3 3 L ST LOBBY WARD 1 1 NRC PDR 1 1 NSIC MURPHYEG.A 1 1 NSIC POORE,W. 1 1 NUDOCS FULL TXT 1 1 NOTE TO ALL "RIDS" RECIPIENTS:

PLEASE HELP US TO REDUCE WASTE! CONTACT THE DOCUMENT CONTROL DESK, ROOM Pl-37 (EXT. 20079) TO ELIMINATEYOUR NAME FROM DISTRIBUTION LISTS FOR DOCUMENTS YOU DON'T NEED!

FULL TEXT CONVERSION REQUIRED TOTAL NUMBER OF COPIES REQUIRED: LTTR 32 ENCL 32

WASHINGTON PUBLIC POWER SUPPLY SYSTEM P.O. Box 968 ~ 3000 George Washington Way ~ Richland, Washington 99352 March 18, 1992 G02-92-065 Docket No. 50-397 Document Control Desk U. S. Nuclear Regulatory Commission Washington, D. C. 20555

SUBJECT:

NUCLEAR PLANT WNP-2, OPERATING LICENSE NPF-21 LICENSEE EVENT REPORT NO. 91-025-01 Transmitted herewith is Licensee Event Report No. 91-025-01 for the WNP-2 Plant. This report is submitted in response to the report requirements of 10CFR50.73 and updates information on further corrective action. Specifically, methods other than procedural control have been selected to implement further corrective action regarding the recombiner blower oil drain plugs Sincerely, J. W. Baker WNP-2 Plant Manager (Mail Drop 927M)

Enclosure cc: Mr. John B. Martin, NRC - Region V Mr. C. Sorensen, NRC Resident Inspector (Mail Drop 901A, 2 Copies)

INPO Records Center - Atlanta, GA Ms. Dottie Sherman, ANI Mr. D. L, Williams, BPA (Mail Drop 399) w 9203250329 920320 PDR ADOCK 0500039'7 S PDR

LICENSEE EVENT REPORT (LER)

ACILITY NAME (I) DOCKET NUMB R ( ) PAGE (3) ashington Nuclear Plant Unit 2 0 5 0 0 0 3 9 7 I OF 5 ITLE (4)

A TRAIN OF THE CONTAINMENTATMOSPHERE CONTROL SYSTEM RENDERED INOPERABLE LONGER THAN ALLOWED BY THE TECHNICAL SPECIFICATIONS DUE TO LOSS OF OIL IN HYDROGEN RECOMBINER BLOWER "

EVENT DATE 5 LER NUMBER 6) REPORT DATE (7) OTHER FACILITIES INVOLVED 8)

MONTH OAY YEAR YEAR Q SEQUENTIAL EVI SION MONTH DAY YEAR FACILITY NAMES CKET NUMB R (s)

NUMBER UMBER 5000 0 9 1 I 9 I 9 I 0 2 5 0 1 0 3 2 0 9 2 5000 PERATING HIS REPORT IS SUBMITTED PURSUANT TO THE REQUIREMENTS OF -10 CFR E: (Check one or more of the following) (11)

ODE (9) 4 ONER LEVEL 20.402(b) 20.405(C) 50.73(a)(2)(iv) 77.71(b) 20.405(a)(1)(i) 50.36(c)(1) 50.73(a)(2)(v) 73.73(c) 20.405(a)(1)(ii) 50.36(c)(2) 50.73(a)(2)(vii) THER (Specify in Abstract 0.405(a)(1)(iii) 50.73(a)(2)(i) 50.73(a)(2)(viii)(A) elow and in Text, NRC 0.405(a)(1)(iv) 50.73(a)(2)(ii) 50.73(a)(2)(viii)(B) orm 366A) 20.405(a)(1)(v) 50.73(a)(2)(iii) 50.73(a)(2)(x)

LICENSEE CONTACT FOR THIS LER 12 AME TELEPHOHE HUMBER C. L. Fies, Compliance Engineer REA CODE 5 0 9 7 7 - 4 1 4 7 COMPLETE ONE LIHE FOR EACH COMPONENT FAILURE DESCRIBED IH THIS REPORT (13)

CAUSE SYSTEM COMPONENT MANUFACTURER EPORTABLE .",4':;:,.'8 CAUSE SYSTEM COMPONENT MANUFACTURER REPORTABLE 0 HPRDS TO HPRDS 8 L 2 0 Y SUPPLEMENTAL REPORT EXPECTED (14) EXPECTED SUBMISSIOH MONTH DAY YEAR ATE ('15)

YES (If es, c tete EXPECTED SUBMISSIOH DATE) X NO ABSTRACT (16)

On September 11, 1991, a Plant Technical Engineer determined that Train A of the Containment Atmosphere Control (CAC) System, i.e., hydrogen recombiner, had been inoperable longer than the 30 days allowed by the Technical Specifications due to a loss of the oil from the recombiner blower caused by a drain plug vibrating free. Based on immediate failure of the recombiner blower during a surveillance test, it was concluded that the plug vibrated free during the previous surveillance test. This resulted in approximately four months of Plant operation with one train of the CAC System inoperable.

The immediate corrective action was to repair the inoperable CAC Train A and lockwire the drain plugs in the Train A recombiner blower.

The root cause for failure of the CAC train was less than adequate procedures for reassembly of the blower.

Corrective actions include: 1) lockwires have been installed on the drain plugs to the Train B hydrogen recombiner blower, 2) change the appropriate documentation to require the drain plugs in each recombiner blower to be properly installed and lockwired, and 3) a Maintenance and Operations Bulletin will be issued advising use of positive locking ability on critical pipe plugs of vibrating equipment.

The safety significance of this event is negligible because CAC Train B was operable and only one train is required to mitigate the consequences of a postulated design basis accident.

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION ACILITY'NAME (I) DOCKET NUMBER (2) LER NUMBER (B) AGE (3)

- Unit ear umber ev. No.

Washington Nuclear Plant 2 0 5 0 0 0 3 9 7 1 2 5 I 2 F 5 ITLE (4)

A TRAIN OF THE CONTAINMENT ATMOSPHERE CONTROL SYSTEM RENDERED INOPERABLE LONGER THAN ALLOWED BY THE TECHNICAL SPECIFICATIONS DUE TO LOSS OF OIL IN HYDROGEN RECOMBINER BLOWER Pln niin Power Level - 0%

PlantMode -4 On September 11, 1991, a Plant Technical Engineer determined that Train A of the Containment Atmosphere Control (CAC) System had been inoperable longer than the 30 days allowed by the Technical Specifications due to a loss of the oil caused by a loss of a drain plug in the recombiner blower during the previous surveillance test. This was based on a surveillance test performed on September 3, 1991, in which the hydrogen recombiner blower to Train A failed almost immediately after initiation. The previous surveillance test on December 8, 1990, was successful and provided no indication of any abnormalities in Train A. The Plant was shutdown for the Refueling outage on April 12, 1991, which resulted in Plant operation for approximately four months with one CAC train inoperable.

On September 3, 1991, the CAC hydrogen recombiner functional test for Train A was initiated. Following an approximate 30-minute preheat cycle, the hydrogen recombiner blower, CAC-FN-lA, received an auto-start signal. The System Engineer indicated that approximately six seconds later the blower motor tripped on a low flow signal. There is a six (6) second time delay for the low flow trip signal to allow the blower to establish an adequate flow rate. The blower motor drew excessive current, representative of a locked-rotor condition.

At 1435 hours0.0166 days <br />0.399 hours <br />0.00237 weeks <br />5.460175e-4 months <br /> on September 3, 1991, the CAC hydrogen recombiner Train A, CAC-HR-1A, was declared inoperable. CAC Train A inoperability was discovered while in Plant condition Mode 4, in which there is no Technical Specification requirement for the CAC System to be operable.

On September 4, 1991, the hydrogen recombiner blower, CAC-FN-1A, was removed from the CAC Train A skid (CAC-HR-1A). A bottom oil drain plug to the blower housing was found lying at the bottom of the blower-motor assembly container. Approximately 25 ounces of oil had drained out of the blower housing into the blower-motor assembly container. The container drains into the container drain piping that connects to the Residual Heat Removal (RHR) System via a loop seal, which ultimately drains to the Suppression Pool via RHR-V-134A. Some oil was removed from the loop seal by blowing pressurized air through the loop seal to an external drain. Some oil remains on the inside surface to the drain piping and some, very little, may have reached the Suppression Pool. However, the quantity of oil that remains is considered to have no effect on the performance of the CAC System or any other Plant safety related equipment or structures.

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION AGILITY'NAHE (1) DOCKET NUHBER (2) LER NUHBER (8) AGE (3) ear umber ev. No.

Washington Nuclear Plant - Unit 2 0 5 0 0 0 3 9 7 1 2 5 1 3 F 5 ITLE (4)

A TRAIN OF THE CONTAINMENT ATMOSPHERE CONTROL SYSTEM RENDERED INOPERABLE LONGER THAN ALLOWED BY THE TECHNICAL SPECIFICATIONS DUE TO LOSS OF OIL IN HYDROGEN RECOMBINER BLOWER After uncoupling the motor from the blower, the motor was found to turn freely, but the blower was seized.

Disassembly of the blower revealed the bearing surfaces were galled and had become overheated.

Evaluation by the Plant Technical Engineer determined that CAC-FN-1A had probably been in an inoperable condition following the last surveillance in December, 1990. The evaluation concluded that the drain plug vibrated free during the December 8, 1990 surveillance resulting in loss of oil and subsequent galling and overheating of the bearing surfaces, which caused bearing seizure on cool down from the surveillance. This conclusion was based on the fact that the Plant Technical Engineer witnessed the Train A blower motor receive a trip signal from the low Qow monitor several seconds after the motor start signal was initiated. This time delay is consistent with the six (6) second time delay for the low Qow trip signal discussed above. The apparent instantaneous motor trip following timing out of the time delay switch indicates that the motor reached locked-rotor current within th'e time delay period. Undamaged bearing surfaces, even with no oil film, would take much longer to cause complete seizure of the blower, which is powered by a 12-hp motor. This further indicates that the bearing surfaces of the blower were in a seized condition prior to the start of the surveillance.

Therefore, loss of oil from the blower occurred during the previous surveillance test as a'result of the drain plug vibrating free, rendering Train A of the CAC System incapable of performing its safety function since December 8, 1990, mm i rr iveAci n The immediate corrective action was to initiate repair of Train A of the CAC System and to lockwire all drain plugs in the blower housing to prevent recurrence.

F her Ev I i n nd rrective Ac i n A. hrEvl i n This event is reportable,per 10CFR50.73(a)(2)(i)(B) as a condition prohibited by the Plant's Technical Specifications. Based on the determination that Train A of the CAC system was inoperable from December 8, 1990 to September 3, 1991, and the Plant was in Mode 1 until April 12, 1991, the Plant exceeded the Technical Specification Action requirements to restore the inoperable train of the CAC System within 30 days, or be in at least Hot Shutdown within the next 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> by approximately 4 months.

2. There were no other structures, components, or systems inoperable prior to the event which contributed to the event.

3 ~ The root cause for failure of the CAC train was that the procedures for reassembly of the blower were less than adequate because torquing requirements and verification were not specified to ensure the drain plugs do not vibrate loose during operation.

LICENSEE EVENT REPORT (LER)

TEXT CONTINUATION AGILITY'NAHE (1) DOCKET NUHBER (2) LER NUHBER (8) AGE (3)

- Unit ear umber ev. No.

Mashington Nuclear Plant 2 0 5 0 0 0 3 9 7 I 2 5 I 4 F 5 ITLE (4)

A TRAIN OF THE CONTAINMENT ATMOSPHERE CONTROL SYSTEM RENDERED INOPERABLE-LONGER THAN ALLOWED BY THE TECHNICAL SPECIFICATIONS DUE TO LOSS OF OIL IN HYDROGEN RECOMBINER BLOWER 3.1 The hydrogen recombiner blower is a straight, two-lobe, rotary compressor (Roots Blower) that normally experiences significant vibration versus blade-type fans. The CAC skid was provided by Air Products and Chemical Company who obtained the recombiner blower, Model 3006/Series 30, Serial Number 147, from Schwitzer Division of Wallace Murry Corporation. Blower reassembly procedures did not provide. torque requirements for the drain plugs or independent verification. Consequently, the skill of the craft was relied upon to provide proper torquing and verification. The reassembly procedures were inadequate for this application because the container around the blower-motor assembly precludes post-operation visual inspection for loosening drain plugs, leaking oil, oil level, or freedom of rotation. Generally, all other Plant safety related equipment is accessible to periodic inspection for the conditions described above.

3.2 Water was introduced into the Train A recombiner blower during the R-5 outage when the CAC skid drain valve to the Suppression Pool, RHR-V-134A, was left open while the Residual Heat Removal (RHR) System was discharging into the Suppression Pool, Enough RHR discharge pressure was developed to force water back into the CAC skid drain lines and fill the CAC recombiner blower-motor container and blower-motor with water. The blower-motor was subsequently removed, cleaned, and reinstalled. Cleaning of the blower required draining the oil by removing one or more of the three drain plugs.

After reinstallation, the system was operated for a period of 8 hours9.259259e-5 days <br />0.00222 hours <br />1.322751e-5 weeks <br />3.044e-6 months <br /> to assure operability.

The as-found condition of the drain plugs in the Train A blower was not documented.

The maintenance procedure for the blower did not require a specific torque value, for the drain plugs, but instead relied on the skill of the craft to apply the appropriate torque.

Prior to R-5, there had been no operability problems with the CAC recombiner blower in either train. The blower-motor assembly in Train B of the CAC System was removed for the first time since both CAC skids were considered operable in December, 1983.

The drain plugs were inspected and lockwires installed on all of the drain 'plugs as was done for the Train A blower. The drain plugs in the Train B blower were found to be tight. Circumstantial evidence indicates that the drain plug that fell out of the Train A blower was reinstalled with less than adequate torque during reassembly in R-5.

B. F her Corrective Action 1, Lockwires have been installed on the drain plugs of the hydrogen recombiner blower to Train B of the CAC System.

LICENSEE EVENT REPORT (L R)

TEXT CONTINUATION AGILITY NANE (I) DOCKET NUMBER '(2) LER NUNBER (8) AGE (3)

- UnIt ear umber ev. No.

Mashington Nuclear Plant 2 0 5 0 0 0 3 9 7 1 2 5 1 5 F 5 ITLE (4)

A TRAIN OF THE CONTAINMENT ATMOSPHERE CONTROL SYSTEM RENDERED INOPERABLE LONGER THAN ALLOWED BY THE TECHNICAL SPECIFICATIONS DUE TO LOSS OF OIL IN HYDROGEN RECOMBINER BLOWER

2. The appropriate documentation has been changed to require the drain plugs in each recombiner blower to be properly installed and lockwired. Engineering has issued a Basic Design Change, BDC 55-,1760-OA, that will place the additional requirements on blower oil drain plug installation in the vendor manual for the Schwitzer Blower, CVI 01-71-00,178,2.
3. A Maintenance and Operation Bulletin was issued to appraise craft and System Engineers of the necessity to ensure positive locking ability for critical pipe plugs in vibrating equipment.

5kffiifi The safety significance of this event is negligible because CAC Train B was operable and only one train is required to mitigate the consequences of a design basis accident. Also, no event occurred during the period of CAC System inoperability that required the CAC System to perform its safety function.

imil r Event There were no similar events.

II In rm i Tex Reference EIIS Reference

~Sstem ~Com nen Wetwell NH Drywell NH Residual Heat Removal System BO Suppression Pool System BT Reactor Containment NH Containment Atmosphere Control System BB Hydrogen Recombiner Blower I (CAC-FN-1A, CAC-FN-1B) BB BLO Flow Monitor BB FI Residual Heat Removal Valve V (RHR-V-134A) BO

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