Information Notice 1999-21, Recent Plant Events Caused by Human Performance Errors

Recent Plant Events Caused by Human Performance Errors

ML031040404
Person / Time
Site:	Beaver Valley, Millstone, Hatch, Monticello, Calvert Cliffs, Dresden, Davis Besse, Peach Bottom, Browns Ferry, Salem, Oconee, Mcguire, Nine Mile Point, Palisades, Palo Verde, Perry, Indian Point, Fermi, Kewaunee, Catawba, Harris, Wolf Creek, Saint Lucie, Point Beach, Oyster Creek, Watts Bar, Hope Creek, Grand Gulf, Cooper, Sequoyah, Byron, Pilgrim, Arkansas Nuclear, Three Mile Island, Braidwood, Susquehanna, Summer, Prairie Island, Columbia, Seabrook, Brunswick, Surry, Limerick, North Anna, Turkey Point, River Bend, Vermont Yankee, Crystal River, Haddam Neck, Ginna, Diablo Canyon, Callaway, Vogtle, Waterford, Duane Arnold, Farley, Robinson, Clinton, South Texas, San Onofre, Cook, Comanche Peak, Yankee Rowe, Maine Yankee, Quad Cities, Humboldt Bay, La Crosse, Big Rock Point, Rancho Seco, Zion, Midland, Bellefonte, Fort Calhoun, FitzPatrick, McGuire, LaSalle, Fort Saint Vrain, Shoreham, Satsop, Trojan, Atlantic Nuclear Power Plant
Issue date:	06/25/1999
From:	Marsh L Division of Regulatory Improvement Programs
To:
References
IN-99-021, NUDOCS 9906280086
Download: ML031040404 (9)

UNITED STATES

NUCLEAR REGULATORY COMMISSION

OFFICE OF NUCLEAR REACTOR REGULATION

WASHINGTON, D.C. 20555-0001 June 25, 1999 NRC INFORMATION NOTICE 99-21: RECENT PLANT EVENTS CAUSED BY HUMAN

PERFORMANCE ERRORS

Addressees

All holders of licenses for nuclear power, test, and research reactors.

Purpose

The U.S. Nuclear Regulatory Commission (NRC) is issuing this information notice to alert

addressees to a recently apparent increase in human performance weaknesses that have

resulted in plant transients. It is expected that recipients will review the information for

applicability to their facilities and consider actions, as appropriate, to prevent a similar

occurrence. However, suggestions contained in this information notice are not NRC

requirements; therefore, no specific action or written response to this notice is required.

Description of Circumstances

Salem Unit I

At 1:38 a.m. on February 28, 1999, the Salem Unit 1 reactor automatically shut down because

of a low bearing oil pressure turbine trip. The unit was operating at 60-percent power before

the shutdown and was being maintained at this power to allow troubleshooting to be performed

on a main feedwater pump. Preparations were also being made to allow maintenance to repair

a leaking main turbine lube oil cooler. One of the two oil coolers had developed a leak on the

previous shift, and the operators were adjusting the position of a cooler isolation valve in an

attempt to more tightly close the valve.

While adjusting the isolation valve, the operators Inadvertently positioned the valve off its closed

seat, allowing oil from the in-service cooler to enter the partially drained out-of-service cooler.

This diverted flow caused a momentary drop in the turbine bearing oil pressure and resulted in

the automatic main turbine trip and subsequent reactor trip.

The cause of the transient has been attributed to misoperation of the cooler isolation valve.

The valve used to swap the main turbine lube oil coolers is a Schutte & Koerting six-way

isolation valve. This type of valve is only used for the main turbine lube oil coolers at Salem

Units 1 and 2, and the valve is operated very Infrequently. The operators did not know that their

attempts to more tightly close the valve would result In moving the valve off its closed seat.

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IN 99-21 June 25, 1999 The operators responded to the automatic shutdown as directed by the plant's emergency

operating procedures and the unit was stabilized in a shutdown condition.

Diablo Canyon Unit I

At 5:06 p.m. on February 25, 1999, the Unit 1 annunciator alarmed in the control room for

'Spent Fuel Pool LevelTemperature.' Operators verified the alarm by checking the plant

computer, which indicated an elevated temperature of 125 degrees F in the spent fuel pool.

The shift foreman dispatched a nuclear operator to the spent fuel pool area. The nuclear

operator noted that the local spent fuel pool temperature gauge indicated 126 degrees F. The

nuclear operator subsequently found that spent fuel pool pump 1-2 was not operating as

expected and restarted the pump at the direction of the shift foreman.

The licensee's investigation into the event revealed that operator logs prepared earlier on

February 25, 1999, had verified that the spent fuel pool pump 1-2 was operating as required

and that spent fuel pool temperature was 100 degrees F. Further investigation revealed that

during the day, relay CIAX-H was replaced. This relay was associated with the containment

Phase A isolation signal. The control circuit associated with the CIAX relay trips the spent fuel

pool cooling pumps during an accident scenario to prevent overloading of the emergency diesel

generators. The relay had been replaced at approximately 1 p.m., and as a result, spent fuel

pool cooling had been lost for approximately 4 hours4.62963e-5 days <br />0.00111 hours <br />6.613757e-6 weeks <br />1.522e-6 months <br /> before the high level/temperature alarm

was received in the control room. Licensee engineers determined that the spent fuel pool

heatup rate was approximately 8 degrees F per hour and would have resulted in spent fuel pool

boiling after approximately 16 hours1.851852e-4 days <br />0.00444 hours <br />2.645503e-5 weeks <br />6.088e-6 months <br />.

A review of the work order associated with the relay replacement revealed that the clearance

associated with the procedure did not contain any precautions or limitations to notify the

operators of the trip of the spent fuel pool cooling pump as a result of removal of the relay.

The pre-job briefing apparently did not identify the condition, nor were the operators or

electricians who performed the relay replacement aware of the resultant condition of the

spent fuel pool cooling pumps.

A second factor that appears to have contributed to the duration of the event was a lack of

controls or indications in the control room of the status of the spent fuel pool cooling pumps, the

temperature of the spent fuel pool, or the level of the spent fuel pool, other than the

aforementioned level/temperature alarm. These indications and controls were available locally

in the spent fuel pool area but, as directed by plant procedures, were required to be reviewed

and logged only once every 12 hours1.388889e-4 days <br />0.00333 hours <br />1.984127e-5 weeks <br />4.566e-6 months <br /> during operator rounds.

Vogtle Unit 2

At 2:07 a.m. on March 2, 1999, operators manually shut down the Unit 2 reactor from

100-percent power because of an observed low water level in the #3 steam generator and a

IN 99-21 June 25, 1999 concurrent alarm of the "Steam Flow/Feed Flow Mismatch" annunciator. The cause of the level

decrease was due to the unexpected closing of the Unit 2 loop 3 main feedwater isolation valve.

The loop 3 main feedwater isolation valve closed because plant equipment operators

mistakenly pulled the control power fuses to the Unit 2 isolation valve while hanging an outage

clearance tag on the Unit I isolation valve.

Following the event, the licensee initiated a root cause analysis to determine the causes of the

operator performance errors and determined that multiple factors contributed to the event, such

as failure to implement self-checking using the dual concurrent verification (i.e., both operators

were present, performed the function, and verified the correctness of the actions); lack of verbal

feedback between the operators regarding the complete component identification tag number, including unit designation; and work schedule factors (one of the operators was working his

sixth 12-hour shift of nine scheduled consecutive twelve hour shifts).

San Onofre Unit 2

At 9:59 a.m. on February 1, 1999, a loss of shutdown cooling occurred at San Onofre Unit 2.

The unit was in mode 6 and refueling was in progress. Before the event occurred, the Train A

4.16-kV vital bus 2A04 was being fed from the offsite transmission system by the unit auxiliary

transformer. Train A bus 2A04 was the protected supply to the operating shutdown cooling

pump and to the containment spray pump which was providing spent fuel pool cooling.

At the time of the event, the licensee was implementing a clearance order to facilitate

maintenance on the reserve auxiliary transformer, which was an alternate power supply for the

Train A 4.1-kV bus 2A04. The clearance called for racking out the already opened Train A

4.16-kV breaker to the reserve auxiliary transformer. In preparation for the activities, the

reserve auxiliary transformer was disconnected from the switchyard and all three grounding

disconnect switches on the primary side of the transformer (220-kV side) were closed.

Subsequently, while attempting to rack out the breaker, electricians performing the work noted

that the breaker was stuck and would not disengage.

Licensee personnel involved with the evolution discussed the matter and incorrectly concluded

that discharging the closing springs would prevent the breaker from inadvertently closing, while

attempting to again rack out the breaker. The operators and electricians involved in the effort

believed that pushing a lever that discharges the closing springs would not cause the breaker to

close. They based this belief on previous experience with using this button while the breaker

was in the racked-out position and not having the breaker close as a result. However, when the

electricians performed the action on the racked-in breaker, the breaker did close. This resulted

in the grounded high side of the reserve auxiliary transformer becoming a near-infinite load on

the low side, which was being supplied by Bus 2A04 through the now closed breaker. This

created an undervoltage condition on Bus 2A04. All of the supply breakers for the affected bus

tripped open, except for the breaker to the reserve transformer which was in an off normal

configuration due to the actions of the electricians.

IN 99-21 June 25, 1999 The standby emergency diesel generator automatically started but did not close onto the

affected bus because of a protective relay lockout that prevented more than one feed to the bus

at any one time. The standby emergency diesel generator was not designed to be capable of

maintaining bus voltage under these circumstances. As a result, the affected bus deenergized, thereby causing a loss of the shutdown cooling and spent fuel pool cooling functions for

approximately 26 minutes.

Following the event, the licensee initiated an investigation and determined that the procedure

directing the grounding of the high side of the reserve auxiliary breaker before racking out the

4.16-kW breakers was inadequate in that the order of the activities should have been reversed.

Additionally, it was determined that although the plant personnel and management involved

recognized the potential for serious consequences If the breaker inadvertently closed, their

planning and control of the evolution did not adequately reflect the increase in risk associated

with these activities.

Discussion

The NRC has noticed an apparent increase in human performance related events that have

resulted in plant transients. The four examples described above represent a sample of those

recent events in which human performance played a key role, and each highlights the notable

challenges that human performance weaknesses may present to plant operation. The

importance of human error in determining risk from nuclear power plants is well known and is

discussed in NUREG/CR-5319, ORisk Sensitivity to Human Error, April 1989. NUREGICR-5527, ORisk Sensitivity to Human Error in the LaSalle PRA, March 1990, presents detailed risk

sensitivity studies involving human performance that had previously shown notable sensitivity of

risk to changes in human error probabilities. In light of these findings, there appears to be a

large risk incentive to ensuring that human performance does not degrade below the

performance level assumed in the plant-specific probabilistic risk assessments and remains

consistent with licensee management expectations.

a

IN 99-21 June 25, 1999 This information notice requires no specific action or written response. However, recipients are

reminded that they are required by 10 CFR 50.65 to take Industry-wide operating experience

(including information presented in NRC information notices) into consideration, when practical, when setting goals and performing periodic evaluations. If you have any questions about the

information in this notice, please contact one of the technical contacts listed below or the

appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

[Original signed by J.E. Lyons]

for Ledyard B. Marsh, Chief

Events Assessment, Generic Communications

and Non-Power Reactors Branch

Division of Regulatory Improvement Programs

Office of Nuclear Reactor Regulation

Technical contact: Greg S. Galletti, NRR

301-415-1831 E-mail: gsca(nrc.oov

Nick Fields, NRR

301-415-1173 E-mail: enf0nrc.aov

Attachments: List of Recently Issued NRC Information Notices

DOCUMENT NAME: S:ADRPM SEC\99-21-in

_OFFICE IOLB:DRIP l Tech Editor l IOLB:DRIP IOLB:DRIP l C:PECB:DRIP

NAME l GGallett* Callure/NF* DTrimble* RGalo* l Nfields*

DATE l 06/18199

. ,1 I

04123/99 l 06/07/99 1 06104/99 1 06/07/99 l

OFFICE C:PK6 {DRIP

NAME [LMS1 DATE l __9_ 9 OFFICIAL RECORD COPY

Attachment

IN 99-21 June 25, 1999 LIST OF RECENTLY ISSUED

NRC INFORMATION NOTICES

Information Date of

Notice No. Subject Issuance Issued to

99-20 Contingency Planning for the 6/25199 All material and fuel cycle

Year 200 Computer Problem licensees and certificate holders

99-19 Rupture of the Shell Side of a 6/23/99 All holders of operating licenses

Feedwater Heater at the Point or construction permits for nuclear

Beach Nuclear Plant power reactors

99-18 Update on NRC's Year 2000 6114/99 All material and fuel cycle

Activities for Materials Licensees licensees and certificate holders

and Fuel Cycle Licensees and

Certificate Holders

99-17 Problems Associated with Post-Fire 6/3/99 All holders of OL for nuclear

Safe-Shutdown Circuit Analyses power reactors, except those who

have permanently ceased

operations and have certified that

the fuel has been permanently

removed from the reactor

99-16- Federal Bureau of Investigation's 5/28/99 All U.S. Nuclear Regulatory

Nuclear Site Security Program Commission fuel cycle, power

reactor, and non-power reactor

licensees

99-15 Misapplication of 10 CFR Part 71 5127/99 All holders of operating licenses or

Transportation Shipping Cask construction permits for nuclear

Licensing Basis to 10 CFR Part 50 power reactors

Design Basis

99-14 Unanticipated Reactor Water 5/5199 All holders of licenses for nuclear

Draindown at Quad Cities Unit 2, power, test, and research reactors

Arkansas Nuclear One Unit 2 and Fitzpatrick

OL = Operating License

CP = Construction Permit

IN 99-21 June 25, 1999 This information notice requires no specific action or written response. However, recipients are

reminded that they are required by 10 CFR 50.65 to take industry-wide operating experience

(including information presented in NRC information notices) into consideration, when practical, when setting goals and performing periodic evaluations. If you have any questions about the

information in this notice, please contact one of the technical contacts listed below or the

appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

[Original signed by J.E. Lyons]

for Ledyard B. Marsh, Chief

Events Assessment, Generic Communications

and Non-Power Reactors Branch

Division of Regulatory Improvement Programs

Office of Nuclear Reactor Regulation

Technical contact: Greg S. Galletti, NRR

301-415-1831 E-mail: asa0nrc.aov

Nick Fields, NRR

301-415-1173 E-mail: enfinrc.aov

Attachments: List of Recently Issued NRC Information Notices

DOCUMENT NAME: S\DRPM SECX99-21.in

OFFICE IOLB:DRIP T Tech Editor IOLB:DRIP IOLB:DRIP C:PECB:DRIP

NAME GGallett* Callure/NF* DTrimble* RGallo* Nfields*

DATE l 06/18/99 j 04/23/99 1 06/07/99 l 06/04/99 l 06107/99 1 OFFICE C:Pa.DRIP

NAME 1LM/9 DATE '0 1XW99 OFFICIAL RECORD COPY

IN 99-xx

June xx, 1999 This information notice requires no specific action or written response. However, recipients are

reminded that they are required by 10 CFR 50.65 to take industry-wide operating experience

(including information presented in NRC information notices) into consideration, when practical, when setting goals and performing periodic evaluations. If you have any questions about the

information in this notice, please contact one of the technical contacts listed below or the

appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

Ledyard B. Marsh, Chief

Events Assessment, Generic Communications

and Non-Power Reactors Branch

Division of Regulatory Improvement Programs

Office of Nuclear Reactor Regulation

Technical contact: Greg S. Galletti, NRR

301-415-1831 E-mail: gsgenrc.gov

Nick Fields, NRR

301-415-1173 E-mail: enf@nrc.gov

Attachments: List of Recently Issued NRC Information Notices

DOCUMENT NAME: G:\REXB\enfXHF IN3.WPD

OFFICE IOLB:DRIP J Tech Editor IOLB:DRIP IOLB:DRIP C:PECB:DRIP

NAME GGalle CallureINF* DTrimble* RGallo* Nfields*

DATE Ii I/ /99 04/23/99 j 06/07/99 06/04199 06/07/99 OFFICE C:PECB:DRIP_ t

NAME LMarsh

DATE I /99 OFFICIAL RECORD COPY

IN 99-xx

May xx, 1999 This information notice requires no specific action or written response. However, recipients are

reminded that they are required by 10 CFR 50.65 to take industry-wide operating experience

(including information presented in NRC information notices) into consideration, when practical, when setting goals and performing periodic evaluations. If you have any questions about the

information in this notice, please contact one of the technical contacts listed below or the

appropriate Office of Nuclear Reactor Regulation (NRR) project manager.

Ledyard B. Marsh, Chief

Events Assessment, Generic Communications

and Non-Power Reactors Branch

Division of Regulatory Improvement Programs

Office of Nuclear Reactor Regulation

Technical contact: Greg S. Galletti, NRR

301-415-1831 E-mail: gsglnrc.gov

Nick Fields, NRR

301-415-1173 E-mail: enf@nrc.gov

Attachments: List of Recently Issued NRC Information Notices 41 kAJ

DOCUMENT NAME: G:\REXB\enf\HFJIN3.WPD

OFFICE IOLB:DRIP ecT itorh IOLB:DRIP IR DIP C:PECB:DRIP

NAME GGalletti ______ DTrimblw RGallo Nfields tip

DATE I / /99 X */ 299 I6 7 /99 G,& 99 I 7 /99 OFFICE C:PECB:DRIP

NAME l LMarsh

DATE l / /99 OFFICIAL RECORD COPY