05000285/LER-1991-009, Corrected Ltr Forwarding LER 91-009-00.Memo Stationery Inadvertently Used Instead of Letterhead Stationery for Cover Ltr

Corrected Ltr Forwarding LER 91-009-00.Memo Stationery Inadvertently Used Instead of Letterhead Stationery for Cover Ltr

ML20079A925
Person / Time
Site:	Fort Calhoun
Issue date:	06/04/1991
From:	Gates W OMAHA PUBLIC POWER DISTRICT
To:	NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LIC-91-0021L, LIC-91-21L, NUDOCS 9106100357
Download: ML20079A925 (1)

LER-2091-009, Corrected Ltr Forwarding LER 91-009-00.Memo Stationery Inadvertently Used Instead of Letterhead Stationery for Cover Ltr

Event date:
Report date:
2852091009R00 - NRC Website

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Omaha Public Power District 444 South 16th Street Mall Omaha, Nebraska 68102 2247 402/636-2000 June 4, 1991 LIC-91-0021L U. S. Nuclear Regulatory Commission Attn: Document Control Desk Mail Station Pl-137 Washington, DC 20555

Reference:

1. Docket No. 50-285

2. Letter from OPPD (W. G. Gates) to NRC (Document Control Desk) dated May 30, 1991 (LIC-91-0020L)

Gentlemen:

Subject:

Licensee Event Report 91-09 for the Fort Calhoun Station Please find attached Licensee Event Report 91-09 dated May 30, 1991. This report was reviously submitted pursuant to the requirements of 10 CFR 50.73(a)(2) iv) via Reference 2. However, memorandum stationery was inadvertant y used insteed of letterhead stationery for the cover letter. We apologize for any confusion this may have caused. Please note that the report itself is unchanged from the previous submittal.

If you should have any questions, please contact me.

Sincerely,

&.N. h W. G. Gates Division Manager Nuclear Operations WGG/tcm Attachment c: R. D. Martin, NRC Regional Administrator W. C. Walker, NRC Project Manager R. P. Mullikin, NRC Senior Resident Inspector INP0 Records Center 57 og3 r

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On April 30,1991, at 0937 hours0.0108 days <br />0.26 hours <br />0.00155 weeks <br />3.565285e-4 months <br />, an electrician was removing a label from inside a Control Room breaker cabinet and inadvertently tripped a normally closed breaker. Realizing what he had done, the electrician immediately reclosed the breaker, causing the Ventilation Isolation ActuationThe Signal VIAS(d anVIAS) to actuate due to a resultant spike of radiation monitors. cause unplanned actuation of some Engineered Safety Features.

This event resulted from inappropriate action by the electrician af ter realizing that he had accidentally tri> ped the breaker. Corrective actions include policy revisions to clearly state tlat all personnel are required to contact the Shif t Supervisor or Control Room operators prior to correcting any unplanned situation.

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0l 0 0 12 OLO l4 textin . t m cs .mmawim At (VIAS) Fort Calhoun is designed Station Unit No.1, to mitigate a release of significant radioiodine orthe Ventilation Isolation A radioactive gas froni the containment to the atmosphere from such source.; as reactor coolant leaks. VIAS is initiated by a Safety injection Actuation Signal (SlAS) a Containment Spray Actuation Signal (CSAS), or a Containment Radiation HighSignal(CRHS). The CRHS feature employs five radiation monitors taking samples from the containment and/or ventilation stacks. Those monitors are RM-050, RM-051, RM-060 RM 061, and RM-062. Activity detected above the 1

setpoint of any one of these moniters can initiate a CRHS. The ratemeters for nach of the five monitors are located in the control room on panels Al-33A and AI-33B (RM 060, 061, 062) to provide operators with remote (RM-050, 051)The ratemeters are equipped with a four position (Off, Operate, indication.

High Voltage, and Calibrate) selector switch that is normally left in the Operate position. Restoring power to these ratemeters without first placing the selector switch in the Calibrate or Off position will cause the ratemeters to spike high and also possibly initiate a CRHS. ,

The VIAS performs the following functions:

1. Closes the containment purge valves (if open),

2. Closes the containment pressure relief valves (if open),

3. Stops the containment purge fans (if running),

4. Closes the containment air sampling valves,

5. Bypasses the safety injection pump rooms and the spent regenerate tank room's filters,

6. Places the control room ventilation system in a filtered mode, and

7. Isolates the Waste Gas Decay Tanks.

On April 30 1991, Fort Calhoun Station was in Mode 1 at 75% power. At 0937 hours0.0108 days <br />0.26 hours <br />0.00155 weeks <br />3.565285e-4 months <br />, an electrician was removing a label from inside a Control Room 120VAC breaker cabinet and inadvertently tripped a normally closed breaker which supplied power to radiation monitors on Al 33A. Realizing what he had done, the electrician immediately reclosed the breaker. The Control Room operators were alet ted to the incident when the VIAS lockout relays tripped and associated alarms annunciated. The Shift Supervisor immediately suspected that the VIAS had been caused by the electrician working in the 120 VAC cabinet. Upon confirming the cause with the electrician, the operators verified that all equipment required to function following a VIAS had operated as designed. Both RM-050 (containment air particulate monitor) and RM-051 (containment gaseous monitor) had spiked above their high alarm setpoints as a result of losing power and subsequently being re-energized, causing a CRHS. These monitors had to be reset to clear the CRfiS before the VIAS relays could be returned to normal. At 0939 hours0.0109 days <br />0.261 hours <br />0.00155 weeks <br />3.572895e-4 months <br />, just two minutes after the VIAS, RM-050 and RM-051 were indicating normal levels of activity inside containment which assured the operators that the CRHS did not result from an actual high activity condition inside containment. In addition to RM-050 and RM-051, the steam gencrator blowdown monitor RM-054A had spiked high and isolated blowdown from both steam generators as designed. The monitor was reset and steam generator blowdown was reestablished.

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0 l0 0 l3 Of 0 l4 nn ~ .m . , .-c , . .nm Conversations with the electrician confirmed that he was removing' old labels, cleanirg the breaker panels, and installing newly designed labels as part of a Control Room labeling project that has been in progress since the 1990 Refueling Outage. While cleaning the area for a new label he occidentally bumped the adjacent breaker and tripped it open, then manually reclosed the breaker.

An investigation into the event revealed that the tripped breaker #17 on 120VAC vital instrument Bus C is actually a bus tie breaker within the cabinet and f'eds two other circuits on Bus Cl. The other two circuits are breaker #19 which feeds panel Al-33A Process Radiation Monitars and tweaker #21 which feeds panel AI-43 Auxiliary Coolant components. When breaker #17 was opened, all power was lost to the components fed by breakers #19 and #21.

As stated earlier, ratemeters for RM-050, RM-051, RM-054A are located on Al 33A and receive instrument power from Bus Cl. When the electrician reclosed breaker

1. 17, the resultant power surge to panel Al-33A caused the radiation monitors to spike high and indicate ahnve the high alarm setpoints. The potential for this ratemeter spike is inherent in the design of the alarm circuit boards when the selector switch is in the Operate position and is avoided during normal operation of the monitors by following the established operating procedure.

The VIAS is defined as part of the Engineered Safeguards Controls and Instrumentation in USAR Fection 6.1.2.3. During this event, the normally open containment air sampling isolation valves had closed upon receipt of the valid VIAS. These valves are part of the Containment Isolation System, which is an Engineered Safety feature (ESF) as defined in Section 6.1.2.1 of the USAR.

Because of this unplanned inadvertent ESF actuation, an Emergency Notification System (ENS) telephone report was made to the NRC on April 3D, 1991 at 1128 hours0.0131 days <br />0.313 hours <br />0.00187 weeks <br />4.29204e-4 months <br /> pursuant to 10 CFR 50.72 (t-)(2)(ii). This event is also reportable pursuant to 10 CFR 50.73(a)(2)(iv).

This event has been evaluated as having minimal safety significance. All VIAS equipment operated as designed. The subject breaker was only open for a couple

! of seconds and power was immediately restored to all affected components. Upon l

restoration of power to the process radiation monitors, an artificial high alarm l was generated due to the characteristics of the ratemeter and all automatic I features associated with the monitors functioned as designed. This incident had i no adverse affect on any components related to Al-45, Auxiliary Coolant Panel.

A Human Performance Evaluation System investigation was performed for this event to identify the root cause and any contributing factors. The VIAS was caused by the electrician reclosing the breaker. The root cause was an inappropriate instinctive action by the electrician after realizing that he had accidentally l tripped the breaker. The initia' tripping of the breaker by the electrician was i accidental and not due to his q':alifications or experience level. No behavioral factors affected the electrician during the performance of his task. The electrician involved in this incident is very conscientious about his work and had been working on this project for over a year.

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0 l0 Ol 4 0' Ol4 ru w ~ . - .. , - c % ,...On The generic implication of this event is that non-operations personnel at the station may try to correct mistakes through inappropriate corrective actions, without fully realizing the consequences of these actions.

Corrective actions associated with this event are:

1. Standing Orders b < , Modification Control, and M 100, Conduct of Maintenance, will be revised to require that personnel contact the Control Room when their actions have resulted in unexpected plant or system conditions. Th;se revisions will clearly state the policy that all personnel are required to contact the Shift Supervisor or Control Room operators prior to correcting any unplanned situation. These procedures will be revised by July 15, 1991.

2. Maintenance personnel are required to complete a self study training course and pass an examination prior to each refueling outage. This training course includes the policies of the standing ordm ; and ensures all appropriate personnel are fully aware of their responsibilities when working at the station. In addition, two similar training courses will be administered to modification craft personnel but will be specific to modificationrequirements,whilestillcontainingthepoliciesofthe standing orders. This course will be revised by December 31, 1991 to require that personnel contact the Control Room when their actions have resulted in unexpected plant or system conditions.

Other inadvertent actuations of VIAS as a result of human error were reported in LERs 87-06, 87-24, 88-29, 88-38 and 90-02. LER 91-02 reported a VIAS actuation resulting from equipment problems.

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