05000331/LER-1986-001, :on 860122,auto-isolation of Control Bldg Ventilation Sys & Initiation of Standby Filter Unit a Occurred.Caused by Low Inlet Air Temp & Personnel Error. Supervisor Counseled & Standby Filter Reset

:on 860122,auto-isolation of Control Bldg Ventilation Sys & Initiation of Standby Filter Unit a Occurred.Caused by Low Inlet Air Temp & Personnel Error. Supervisor Counseled & Standby Filter Reset

ML20153H200
Person / Time
Site:	Duane Arnold
Issue date:	02/21/1986
From:	Mineck D, Probst J IES UTILITIES INC., (FORMERLY IOWA ELECTRIC LIGHT
To:	NRC OFFICE OF ADMINISTRATION (ADM)
References
DAEC-86-0132, DAEC-86-132, LER-86-001, LER-86-1, NUDOCS 8602280697
Download: ML20153H200 (4)

LER-1986-001, on 860122,auto-isolation of Control Bldg Ventilation Sys & Initiation of Standby Filter Unit a Occurred.Caused by Low Inlet Air Temp & Personnel Error. Supervisor Counseled & Standby Filter Reset

Event date:
Report date:
Reporting criterion:	10 CFR 50.73(a)(2)(iv), System Actuation
3311986001R00 - NRC Website

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NAME TELEPHONE NUMGER AREA COCE James R. probst, Technical Support Engineer 31119 8i5111-17:31018 COMPLif t ONE LINE FOR EACM COMPONENT PAILURE DESCRISED IN TMIS REPORT 113)

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At 0603 hours0.00698 days <br />0.168 hours <br />9.970238e-4 weeks <br />2.294415e-4 months <br /> on January 22, 1986, witn the reactor in run mode, an auto-isolation of the Control Building ventilation system and initiation of the ' A' Standby Filter Unit (SFij) occurred as a result of low inlet air temperature in the normal main air intake plenum. This constitutes an unplanned actuation of an Engineering Safety Feature and is reportable per 10 CFR 50.73(a)(2)(iv).

The root cause of this event was personnel error. An inoperable inlet air preheat coil had been covered with plastic to prevent cold air flow into the plenum. The repair crew which had completed repairs on the coil the afternoon of 1/21/86 did not put the temporary plastic cover back in place and their irrmediate supervisor did not notify his supervisor or the control room personnel that the preheat coil was ready to be placed in service. Cold outside air therefore traveled by the coil without being heated, resulting in the SFU initiation. As a corrective action the immediate supervisor was counseled.

The SFU was reset and the preheat coil returned to service later the same day.

The SFU initiated and functioned as designed.

Low inlet air temperature is a nonsafety grade actuation.

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n-Duane Arnold Energy Center o !s !o Io Io i 313il 8I6 0101 010 Of 2 0F 0 13 At 0603 hours0.00698 days <br />0.168 hours <br />9.970238e-4 weeks <br />2.294415e-4 months <br /> on January 22, 1986, with the reactor in run mode at 66% power, an auto-isolation of the Control Building ventilation system and initiation of the 'A' Standby Filter Unit (SFU, EIIS System VI) occurred as a result of low inlet air temperature in the normal main air intake plenum. This auto-initiation of a Standby Filter Unit constitutes an unplanned actuation of an Engineered Safety Feature and, as such, is reportable per 10 CFR 50.73(a)(2)(iv). See LER's84-003, 84-004,84-011, 84-043 for similar evehts.

The Control Building ventilation systen will isolate the building from normal outside air intake and recirculate the ventilation air through the essential switchgear rooms, battery rooms, and the control room on inlet air high radiation or low temperature.

In addition, the system supplies treated make-up air through the Standby Filter Units to balance the exhaust of the battery rooms. The safety-related functions of the SFU's and Control Building isolation is to minimize operatcr radiation exposure by filtration of the make-up outside air being provided in place of full flow makeup.

The nonsafety related function of the SFU's is to auto-initiate on low inlet temperature in order to provide more heat for the comfort of the control room personnel and to protect equipment from eventual cold temperatures.

The Control Building air intake plenum has three hot water preheat coils, each l

approximately 3.5 feet square, piped in parallel and vertically stacked wit-hin the plenum so that intake air must pass through a coil under normal I

conditions. On 1/07/86, the lower heating coil was discovered to have a rupture in its tubing.

It was therefore isolated, and then covered with plastic to prevent outside air from passing through the coil unheated. When being repaired the coil it removed and a* baffle placed in its space to prevent air flow. On 1/22/86, control room personnel investigating immediately af ter the SFU initiation at 0603 hours0.00698 days <br />0.168 hours <br />9.970238e-4 weeks <br />2.294415e-4 months <br /> found the lower preheat coil in place without the temporary plastic cover.

Further investigation revealed the root cause of the SFU initiation to be personnel error.

Repairs to the coil had been completed and it had been reinstalled late on the day shift of 1/21/86 with the plastic cover left off. However, neither the supervisor or the control l

room personnel were informed that day by the immediate supervisor of the repair crew that the heater repair was now completed. Therefore, unheated air passed through the lower coil throughout the evening of 1/21/86 and early morning of 1/22/86, until the low inlet temperature switch (VI-TS-6124A),

whose clement is located immediately downstream of the heaters, tripped at its l

forty degree Fahrenheit setpoint resulting in the SFU initiation. The outside temperature at the time of the initiation was approximately 16 degrees Fahrenheit. The SFU was reset at 1425 hours0.0165 days <br />0.396 hours <br />0.00236 weeks <br />5.422125e-4 months <br /> on 1/22/86. The plastic over the heaters was replaced until the heaters were returned to service at 1625 hours0.0188 days <br />0.451 hours <br />0.00269 weeks <br />6.183125e-4 months <br /> on 1/22/86.

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.ir, As a corrective action the immediate supervisor was counseled by his supervisor. Plant personnel have been reminded of the importance of keeping Operations personnel informed of the progress of plant activities in the weekly plant newsletter and a weekly meeting. The Standby Filter Unit initiated and functioned as per design.

In addition, the SFU initiated on a nonsafety parameter and was not required for operator or plant safety.

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4 lowa Electric Light and Ibwer Company February 21, 1986 l

DAEC-86-0132.

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U. S. Nuclear Regulatory Commission Document Control Desk Washington, D. C.

20555 Subject: Duane Arnold Energy Center Docket No. 50-331 Op. License DPR-49 l

Licensee Event Report No.86-001 Gentlemen:

In accordance with 10 CFR 50.73 please find attached a copy of the subject Licensee Event Report.

Very truly yours, l

w Daniel L. Mineck Plant Superintendent - Nuclear Duane Arnold Energy Center DLM/JRP/kp Attachment - LER 86-001 l

cc: Mr. James G. Keppler Regional Administrator Region III U. S. Nuclear Regulatory Commission 799 Roosevelt Road Glen Ellyn, IL 60137 NRC Resident Inspector - DAEC File A-118a

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