ler 97-006-00:on 970428,rcp lube oil collection sys was outside … · 2017. 2. 28. · licensee...

CATEGORYREGUIAT Y INFORMATION DISTRIBUTION YSTEM (RIDS)

ACCESSION NBR:9706040327 DOC.DATE: 97/05/28 NOTARIZED: NOFACIE:,50-275 Diablo Canyon Nuclear Power Plant, Unit 1, Pacific Ga

0"'JgH. NAME AUTHOR AFFILIATIONBACKMAN,V.A. Pacific Gas & Electric Co.POWERS,R.P. Pacific Gas & Electric Co.

RECIP.NAME RECIPIENT AFFILIATION

DOCKET05000275

SUBJECT: LER 97-006=00:on 970428,RCP lube oil collection sys outsidedesign basis. Caused by personnel error.POA written wereshift orders issued to provide guidance for operators on RCPpump starts.W/970528 ltr.

DISTRIBUTION CODE: IE22T COPIES RECEIVED:LTR ENCL SIZE:TITLE: 50.73/50.9 Licensee Event Report (LER), Incident Rpt, etc.

NOTES:

RECIPIENTID CODE/NAME

PD4-2 PD

INTERNAL: ACRSAEOD/SPD/RRABNRR/DE/ECGBNRR/DE/EMEBNRR/DRCH/HICBNRR/DRCH/HQMBNRR/DSSA/SPLBRES/DET/EIB

EXTERNAL: L ST LOBBY WARDNOAC POOREgW.NRC PDR

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RECIPIENTID CODE/NAME

BLOOM,S

A ~DyQVtBPILE CENTE

RR DE/EELBNRR/DRCH/HHFBNRR/DRCH/HOLBNRR/DRPM/PECBNRR/DSSA/SRXBRGN4 FILE 01

LITCO BRYCE,J HNOAC QUEENERgDSNUDOCS FULL TXT

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FULL TEXT CONVERSION REQUIREDTOTAL NUMBER OF COPIES REQUIRED: LTTR 25 ENCL 25

Pacific Gas and Electric Company Diablo Canyon Power Plant

P.O, Box 56Avifa Beach, CA 93424

805/545-6000

Robert P. Powers

Vice President-Diablo Canyon

Operations and Plant Manager

lVlay 28, 1997

PG&E Letter DCL-97-097

U.S. Nuclear Regulatory CommissionATTN: Document Control DeskWashington, D.C. 20555

Docket No. 50-275, OL-DPR-80Docket No. 50-323, OL-DPR-82Diablo Canyon Units 1 and 2Licensee Event Re ort 1-97-006-00Reactor Coolant Pum Lube Oil Collection S stem 0'utside Desi n Bases Due toPersonnel Error

'Dear Commissioners and Staff:

Pursuant to 10 CFR 50.73(a)(2)(ii)(B), PG&E is submitting the enclosedLicensee Event Report regarding the reactor coolant pump lube oil collectionsystem being outside the design bases due to personnel error.

This event did not adversely affect the health and safety of the public.

Robert P. Powers

cc: Steven D. BloomEllis W. MerschoffKenneth E. PerkinsMichael D. TschiltzDiablo DistributionINPO

Enclosure

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LICENSEE EVENT REPORT (LER) TEXT CONTINUAT(ON

FACILITYNAME (1)

Diablo Canyon Unit 1

TEXT

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Plant Conditions

Units 1 and 2 have been in various modes and at various power levels with theconditions described below.

ll. Descri tion of Problem

A. Summary

On April 28, 1997, at 1627 PDT, with Unit 1 in, Mode 6 (Refueling with thereactor vessel defueled) for a refueling outage, and Unit 2 in Mode 1

(Power Operation) at 100 percent power, PG8 E determined that Units 1

and 2 reactor coolant pump (RCP) lube oil collection systems do not meetthe requirements of 10 CFR 50.48 and 10 CFR 50, Appendix R. A 1-hour,non-emergency report was made to the NRC in accordance with 10 CFR50.72(b)(1)(ii)(B) on April 28, 1997, at 1634 PDT. The 1-hour, non-emergency report identified liftoil pump tubing that was unshielded onUnits 1 and 2. lt was also determined that some drip pans of the RCPlube oil collection system were missing or damaged on Unit 1. Based ona review of'inspections, photographs, and video tapes, the drip pans inUnit 2 were evaluated to be acceptable.

B. Background

PG8 E is committed to provide a RCP lube oil collection system consistentwith the requirements of 10 CFR 50, Appendix R, Section III.O as follows:

"Such collection systems shall be capable ofcollectinglube oil from all potential pressurized and unpressurizedleakage sitesin the reactor coolant pump lube oil systems.Leakage shall be collected and drained to a vented closedcontainer that can hold the entire lube oil system inventory.A flame arresteris requiredin the ventif the flash pointcharacteristics of the oilpresent the hazard of fireflashback. Leakage points to be protected shallinclude liftpump and piping, overflow lines, lube oil cooler, oil fillanddrain lines and plugs, flanged connections on oil lines, andlube oil reservoirs where such features exist on the reactorcoolant pumps. The drain line shall be large enough toaccommodate the largest potential oil leak."

LICENSEE EVENT REPORT (LER) TEXT CONTINUATION

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The function of the RCP lube oil collection system is to collect oil leakagefrom the RCP lube oil system and route the collected oil to a holding tankto prevent the oil from contacting hot piping or other hot surfaces, whichcould cause the oil to ignite. A fire caused by the leaked oil couldpotentially involve safety-related equipment located in the vicinity.

The RCP lube oil collection system consists of shielding around potentialleakage sources and drip pans to collect and direct any oil leakage to thecollection tank. The system configuration is described in SupplementalSafety Evaluation Report (SSER) 23 for Unit 1, and SSER 31 for Unit 2.

The RCP liftoil pump supplies high pressure oil to the RCP motor thrustbearing shoes during startup. The lift pump is only energized uponstartup of the RCP. This typically consists of starting the lift pump 2minutes before starting the RCP and securing the lift pump approximately1 minute after the RCP is started. The liftpump may also be used duringrestart of a RCP following a reactor trip.

C. Event Description

The RCP lube oil collection system for Units 1 and 2 was installed duringthe period of 1977 - 1978.

On July 27, 1977, the Appendix A Fire Protection review was submitted.

Based on a review of available information, it appears that the liftoil pumptubing was routed outside the shield in 1977 - 1979.

On February 19, 1981, 10 CFR 50, Appendix R, became effective.

On July 15, 1983, PG8 E submitted the Appendix R review, stating thatthe RCP lube oil collection system was in compliance.

On August 16, 1994, NRC Information Notice (IN) 94-58 was issued. TheIN described a fire that occurred at one plant due to oil leaking from acrack in a polyvinyl chloride fitting located between the RCP and the liftoilpump. The IN also described a plant where portions of the lube oilsystem were outside the oil collection system.

During May and June of 1996, PG8 E Quality Assurance performed anassessment of the RCP lube oil collection system to Appendix R. Unit 2


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was walked down during the Unit 2 seventh refueling outage and wasfound to be acceptable.

On November 11, 1996, engineering performed a walkdown of Unit 2during a forced outage because of reports of oil found on the trays inUnit 2. The amount of oil was found to be normal for the operation of theRCP motor, and the collection system was working as designed. Videoswere taken of the RCP lube oil collection system during the walkdown.

On March 19, 1997, engineering performed another walkdown of Unit 2during a forced outage and took additional pictures of the RCP lube oilcollection system. Again, the collection system was working as designed.

On April 19, 1997, during Mode 3 (Hot Standby) of the Unit 1 eighthrefueling outage (1R8), engineering performed a limited walkdown toinspect RCP oil collection system effectiveness. Some deficiencies withthe pans were identified and documented by engineering.

On April 24, 1997, during 1R8, engineering performed a detailedwalkdown of the Unit 1 RCP lube oil collection system and identifiedportions of the tubing associated with the oil lift pump for each RCP thatwere not enclosed by the sheet metal enclosures as described in SSER23.

On April 28, 1997, at 1634 PDT, a 1-hour non-emergency report wasmade in accordance with 10 CFR 50.72 (b)(1)(ii)(B) due to thedetermination that the RCP lube oil collection system was outside of itsdesign basis. It was confirmed that the configuration of the Unit 2 oil liftpump enclosure and tubing is similar to that identified for Unit 1.

On April 30, 1997, a prompt operability assessment (POA) was approvedthat addressed the operation of Unit 2 with the RCP lube oil collectionsystem outside of its design basis. The POA concluded that it wasacceptable to continue operating Unit 2 with compensatory measures asoutlined in the POA.

On May 15, 1997, Operability Evaluation 97-04, Revision 0, was approvedby the Plant Staff Review Committee documenting acceptability of thecontinued operation of Unit 2 with the exposed instrument tubing on theliftoil pump.


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D. Inoperable Structures, Components, or Systems that Contributed to theEvent

None.

E. Dates and Approximate Times for Major Occurrences

1. April 28, 1997, 1627 PDT: Event/discovery date: . PG8 Edetermined that the RCP lube oilcollection systems do not meetthe requirements of 10 CFR50.48, and 10 CFR 50,Appendix R.

2. April 28, 1997, 1634 PDT: A 1-hour, non-emergency reportwas made in accordance with10 CFR 50.72 (b)(1)(ii)(B).

F. Other Systems or Secondary Functions Affected

None.

G. Method of Discovery

Fire protection engineers performing a walkdown of the Unit 1 RCP lubeoil collection system identified the collection system deficiencies.

H. Operator Actions

As an immediate corrective action for Unit 2, a shift order was issued toprovide. guidance to operators on starting RCPs, as well as what theindications would be of a potential liftpump oil leak.

Safety System Responses

None.


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III. Cause of the Problem

A. Immediate Cause

During the course of.routine maintenance and construction activities, pansections were damaged, altered, or removed. In addition, instrumenttubing on the liftoil pump was routed outside the pump shielding.

B. Root Cause

Due to the lack of documentation and the amount of time that has passedsince the instrument tubing was routed outside the shielding, a definitiveroot cause could not be established. The cause is presumed to bepersonnel error (non-cognitive), knowledge exceeded on the part of theindividuals who performed and approved the tubing modification.

IV. Anal sis of the Event

The unenclosed RCP liftoil system components include a pressure gauge, apressure switch, and an approximately 15-inch run (slightly different on eachRCP) af 3/8" diameter ASTM A-213 (or A-276) Type 316 stainless steelinstrument tubing, and associated Swagelock compression fittings. The tubewall is 0.065 inches thick and has a working pressure rating of over 7500 psi.The tubing is seamless, and therefore no welds exist that could crack andleak similar to the IN 94-58 event. The fittings are rated to at least 5300 psi.The maximum operating pressure of the system (1200 psi) is considerablybelow the design pressure of the tubing and fittings.

In order to ensure that the liftoil system is intact, the system is routinelyinspected for oil leakage prior to startup from a refueling outage.

A detailed review of the period from July 23, 1985, to present, was performedto determine the past leakage history of the lift oil system. The reviewidentified only one leak associated with the lift pump tubing addressed by thisLER. A lift pump pressure test connection had a small amount of observedoil residue, and the test connection fitting was suspected as the source of theleak. The magnitude of the leak was such that the source was almostundetectable. The fitting was replaced and the leak was stopped.

Based on the past performance of the Swagelock fittings and the tubing onthe liftoil system, the system operating pressure versus the tubing's rated

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pressure, and the absence of maintenance activities performed on the liftpumps other than during refueling outages, it is considered highly unlikelythat a spontaneous leak would have developed in the oil lift pump tubing.However, if a leak in the system had occurred, the resulting leakage couldhave potentially resulted in oil contacting hot piping. There are several hotpipes in the vicinity of the RCPs. The oil used as a lubricant in the RCPmotor is Mobil Synthetic Oil, SHC-824. The material safety data sheets forthis oil list a flash point of 425'F. During normal operation the temperature ofRCS hot leg piping is approximately 600'F and the cold leg is approximately540'F; therefore, the potential for oil ignition exists.

Although the potential exists for oil ignition, the following factors tend tominimize the possibility of a fire. The liftpump is energized only upon startupof the RCP. This is procedurally controlled and typically consists of startingthe liftpump 2 minutes before starting the RCP and securing the lift pumpapproximately 1 minute after the RCP is started. Once the RCP is operatingand the liftoil system turned off, the system pressure drops to zero.Significant leakage is; therefore, not considered credible at this point ifnoneoccurred during the startup. Any leakage that occurred while the system wasunpressurized would be droplets, which would be collected by the RCP lubeoil collection system.

If a break were to occur during the brief system pressurization period, it wouldresult in oil spraying from the tubing. However, even ifthe break were tooccur, it would not be expected to result in a fire because:

1. With few exceptions, all hot piping surfaces are covered with mirror typereflective insulation. This type of insulation prevents the oil from beingabsorbed into the insulating medium and shields the hot pipe surface. Allinsulating blankets are securely installed with all insulating sections firmlybutted to one another. As a result, it is unlikely that significant gapsbetween sections will exist to permit the intrusion of oil, which could makecontact with the hot pipes beneath. While small gaps may exist betweeninsulating sections, the total exposed area is extremely small and wouldrequire a concentrated amount of lube oil to be deposited in order to be afire hazard concern.

2. Operational guidance and system interlocks are in place to identifyserious RCP lube oil collection system leaks. In accordance withAnnunciator Response Procedure, AR PK05-01 through -04, a low-levelalarm for the upper reservoir oil level will initiate a containment entry by


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Operations personnel to verify upper reservoir oil level. In addition to theupper oil reservoir level alarm, the starting circuit associated with the RCPis provided with an interlock, which prevents the starting of the RCP with alow lube oil pressure condition. The liftpump is a low volume pump with acapacity of approximately 6 gpm at 1200 psi. Additionally, based on areview of RCP lube oil reservoir oil addition records, the low level alarmtypically annunciates with changes of less than 10 gallons. Consequently,the oil leakage would be identified before a significant quantity of oil couldbe sprayed from the tubing.

3. Because of the location of the liftpump and the uncovered tubing near thetop of the RCP motor, and the air currents that exist at this location, asmall oil leak would create a thin film rather than collecting on hot piping.An oil film will not support combustion because the cooler containmentsurfaces will act as a cooling medium. Any thin film deposited on a hotsurface would rapidly decompose.

4. The lube oil manufacturer (Mobil), estimates that the auto-ignitiontemperature of the lube oil is approximately 700'F. This is above thesurface temperature of the piping in the vicinity of the RCP. The ignitiontemperature for oil soaked insulation is lower; however, as noted above,the likelihood of a sufficient volume of oil being sprayed onto uncoveredbatting insulation is very low.

In the event a fire did occur due to lube oil leakage outside the RCP lube oilcollection system, the following fire protection systems would mitigate thepotential for spread or significant damage:

1. Each RCP is provided with an active fire suppression system with pendantstyle heads. Upon actuation, the heads provide a 360'F spray pattern.

2. Smoke detection is provided above each RCP. In the unlikely event that afire were to occur, the large quantities of smoke typically emitted from oilfires will provide early detection and permit prompt response by controlroom staff and the onsite fire brigade.

In summary, while the likelihood of an oil leak/break is very low, ifa leak didoccur, local conditions are such that the likelihood of causing a fire are verylow. In the unlikely event a fire were to occur, fire detection and delugesystems are in place to ensure it is promptly detected and extinguished.


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Based on the above analysis, the health and safety of the public were notadversely affected by this condition.

V. Corrective Actions

A. Immediate Corrective Actions

A POA was written for Unit 2 with compensatory measures. Thecompensatory measures were shift orders issued to provide guidance for,

operators on RCP pump starts as well as indications of a potential liftpump oil leak as discussed above in operator actions.

B. Corrective Actions to Prevent Recurrence

1. Design changes were issued and implemented during the currentrefueling outage for Unit 1 to bring the RCP lube oil collection systemin compliance with the requirements of 10 CFR 50, Appendix R,Section III.O.

2. The unshielded section of instrument tubing on the Unit 2 liftoil pumpswill be shielded during the next Unit 2 forced outa„~ or refuelingoutage, whichever occurs first.

3. An inspection of the RCP lube oil collection system will be requiredcoming out of each refueling outage to verify that properconfiguration is maintained.

Vl. Additional Information

A. Failed Components

None.

B. Previous LERs on Similar Problems

None.

ler 97-006-00:on 970428,rcp lube oil collection sys was outside … · 2017. 2. 28. · licensee...

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