05000255/LER-1994-001, :on 940121,both Trains of Control Room Emergency Heating,Ventilation & Air Conditioning Inoperable. Caused by Screen Plugged W/Ice & Snow.Surveillance Procedure Revised

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:on 940121,both Trains of Control Room Emergency Heating,Ventilation & Air Conditioning Inoperable. Caused by Screen Plugged W/Ice & Snow.Surveillance Procedure Revised
ML18059A700
Person / Time
Site: Palisades Entergy icon.png
Issue date: 02/18/1994
From: Hillman C, Slade G
CONSUMERS ENERGY CO. (FORMERLY CONSUMERS POWER CO.)
To:
NRC OFFICE OF INFORMATION RESOURCES MANAGEMENT (IRM)
References
LER-94-001, LER-94-1, NUDOCS 9403080272
Download: ML18059A700 (5)
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LER-1994-001, on 940121,both Trains of Control Room Emergency Heating,Ventilation & Air Conditioning Inoperable. Caused by Screen Plugged W/Ice & Snow.Surveillance Procedure Revised
Event date:
Report date:
Reporting criterion: 10 CFR 50.73(a)(2)(ii)(B), Unanalyzed Condition
2551994001R00 - NRC Website
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text

~. *il consumers Power

~Ed.,,, POWERINli MICHlliAN-S PROliRESS Palisades Nuclear Plant:

27780 Blue Star Memorial Highway, Covert, Ml 49043 Febru~ry 18, 1994 Nuclear Regulatory Commission Document Control Desk

  • Washington, DC 20555 DOCKET 50-255 - LICENSE DPR~20 - PALISADES PLANT -

GB Slade General Manager LICENSEE EVENT REPORT 94-001 - FAILURE TO MAINTAIN MINIMUM PRESSURE IN THE CONTROL ROOM WITH THE.HVAC SYSTEM IN THE EMERGENCY MODE BECAUSE THE INTAKE WAS PLUGGED WITH ICE AND SNOW Licensee Event Report (LER)94-001 is attached. This event is reportable in accordance with 10CFR50.73(a)(2)(ii)(B) as condition outside the design basis

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General Manager CC Administrator, Region III, USNRC NRC Resident Inspector - Palisades Attachment

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NRC Form 388 U.S. NUCLEAR REGULATORY COMMISSION 111-831 APPROVED OMB NO. 31~10.

EXPIRES: 8131 /86 LICENSEE EVENT REPORT (LERI FACILITY NAME t1 I DOCKET NUMBER 121 PAGE 131 Palisades Plant o I s I o ro Io I 21 s 1 5

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14 TITLE 141 FAILURE TO MAINTAIN MINIMUM PRESSURE IN THE CONTROL ROOM WITH THE HVAC SYSTEM IN THE EMERGENCY MODE BECAUSE THE INTAKE WAS PLUGGED WITH ICE AND SNOW EVENT DATE !61 LER NUMBER 181 REPORT DATE 181 OTHER FACILITIES INVOLVED CBI I<)

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REVISION FACILITY NAMES MONTH DAY YEAR YEAR NUMBER NUMBER MONTH DAY YEAR N/A ol61ololol I g 1 211 9

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20.4061all1lM 60.731all2lfliil 60.731all2llxl LICENSEE CONTACT FOR THIS LER 1121 NAME TELEPHONE NUMBER Cris T. Hillman, Staff Licensing Engineer sA7A1c1°~ I 7 I 6 I 4 I -I a I s I, I 3.

COMPLETE ONE LINE FOR EACH COMPONENT FAILURE DESCRIBED IN THIS REPORT 1131 MANUFAC-REPORTABLE ',:-*::*>.-,_ ***.

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I SUPPLEMENTAL REPORT EXPECTED 1141 MONTH DAY YEAR rx, NO EXPECTED 11 YES Vf y.., r:omt>Mr. ExPECTED SUBMISSl,ON aA TEI SUBMISSION I

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DATE 1161 ABSTRACT UJmir ID 1400-*** i.e., __

,_,,, fiftHn ling#--* rypew-l#Nal 1181 ABSTRACT On January 21, 1994, at 1017 hours0.0118 days <br />0.283 hours <br />0.00168 weeks <br />3.869685e-4 months <br />, with the plant operating at 100% power, both trains 'Of the control room emergency heating, ventilation, and air conditioning (HVAC) were unable to maintain the required 0.125 inches water gauge (WG) pressure, were declared inoperable and the action statement for Technical Specifica~ion 3.0.3 was entered.

This event was caused when the control room emergency HVAC fresh air intake bird screen became plugged with ice and snow.

Corrective action for this event includes modifying a surveillante procedure to record control room pressures from one reading in 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> to 10 hourly readings and modifying an alarm response procedure to instruct the operators to inspect the intake for blockage if control room pressure is low.

NRC Form 388A 19-831.

U.S. NUCLEAR REGULATORY COMMISSION APPROVED OMB NO. 3160-0104 EXPIRES: B/31 /86 LICENSEE EVENT REPORT (LERI TEXT CONTINUATION FACILITY NAME 111 DOCKET NUMBER 121 LER NUMBER 131 PAGE 141 SEQUENTIAL REVISION YEAR NUMBER NUMBER Palisades Plant 0 I 5 I 0 I 0 I 0 I 2 I 5 I 5 9 I 4 0 I 0 I 1 0 I 0 0 J 2 OF 0 I 4 EVENT DESCRIPTION*

On January 21, 1994, at 1017 hours0.0118 days <br />0.283 hours <br />0.00168 weeks <br />3.869685e-4 months <br />, with the plant operating at 100% power, technical speci fi cations survei 11 ance pro'cedure (TSSP) M0-33, "Control Room HVAC Emergency Operation," was in progress.

During the test, it was determined that both trains of the control room emergency heating, ventilation, and air conditioning (HVAC) [NA;AHU] were unable to maintain the required 0.125 inches water gauge (WG) pressure.

Both trains of the control

This event is reportable to the NRC in accordance with IOCFR50.73{a){2){ii)(B) as condition outside the design basis of the plant.

CAUSE OF THE EVENT

This event was caused when the control room emergency HVAC fresh air intake bird screen became plugged with ice and snow.

During the performance of the technical specifications surveillance test the combination of cold weather, snow, wind direction, and cooling tower plume caused the HVAC intake to become plugged with ice and snow.

ANALYSIS OF THE EVENT

The control room emergency *fresh air make-up enters a 14-irych diameter inlet pipe 95 meters from containment on the north end of the service building at rooftop level.

One thousand cubic feet per minute (cfm) of make-up air is drawn into this pipe to maintain a positive pressure greater than 0.125 inches WG in the control room in accordance with Palisades supplemental administrative technical specifications, Standing Order (SO) 54.

On January 21, 1994, during the performance of the technical specifications surveillance test (TSSP) M0-33, "Control Room HVAC Emergency Operation," the combination of cold weather, snow, wind direction, and cooling tower plume caused the control room emergency HVAC fresh air intake* bird screen to become plugged with snow and ice. At the time of the test, winds were from the southwest at approximately 13 mph.

This caused the plume from the cooling towers to envelop the plant site. The outside temperature varied between 5 and l0°F and it was snowing.

The combination of these environmental factors caused the formation of ice and the buildup of snow on the control room emergency HVAC fresh air i_ntake screen.

During the performance of TSSP M0-33, the Shift Supervisor (SS) and the HVAC system engineer noticed the loss of control room pressure.

The SS and the HVAC system engineer went to the mechanical equipment room to check control i

I

NRC Form 388A 19-831 FACILITY NAME 111 Palisades Plant.

LICENSEE EVENT REPORT (LERI TEXT CONTINUATION DOCKET NUMBER 121 YEAR LER NUMBER 131 SEQUENTIAL NUMBER U.S. NUCLEAR REGULATORY COMMISSION APPROVEO OMB NO. 3160-0104 EXPIRES: 8/31186 REVISION NUMBER PAGE 141 o I s I *o I o I o I 2 I s I s s 14 -. o I o I i o I o o J 3 oF o 14 room HVAC *system parameters (airflow rates, filter differential pressures, damper positions and evidence of any open penetrations, etc.). They requested the control room operators to place both systems in the emergency mode thus doubling the air make-up to 2000 cfm.

The fresh air flow make-up rate did not increase as expected.

The spare train of control room emergency HVAC was removed from service and left in the auto position. The SS and the HVAC system engineer then inspected the fresh air intake and confirmed that the control room emergency HVAC fresh air intake screen was plugged with snow and

- ice. System performance had degraded such that the lowest pressure reading in the control room was 0.07 inches WG.

As a result, both trains of the control room emergency HVAC were declared inoperable at 1017 hours0.0118 days <br />0.283 hours <br />0.00168 weeks <br />3.869685e-4 months <br /> on January 21, 1994.

The SS directed the actions for cleaning of fresh air intake *and secured control room access doors to prevent artificial drops in pressure in order to better assess control room envelope pressures.

Plant personnel were dispatched to remove the ice and snow buildup from the fresh air intake screen.

Following cleaning, the pressure in the control room returned to the normal reading of 0.26 inches WG, both trains of the control room emergency HVAC were declared operable at 1029 hours0.0119 days <br />0.286 hours <br />0.0017 weeks <br />3.915345e-4 months <br /> on January 21, 1994, and the action statement for Technical Specification 3.0.3 was exited. Subsequently, both trains of the control room emergency HVAC were operated in the emergency mode to verify that the system was able to maintain control room pressure at 0.26 inches WG.

Safety Significance

The Control Room HVAC System must be able to maintain a positive pressure in the control room envelope for certain accident conditions described in the Palisades FSAR, Chapter 14.

During this event, the reduction in positive pressure to approximately 0.07 inches WG pressure reduced the margin of safety; however, a positive pressure was still maintained in the control room envelope.

The significant contributing factor to this plugging event was the wind direction which caused the cooling tower plume to envelop the plant site.

This environmental condition coupled with cold temperatures during the emergency mode of operation of the control room HVAC was the primary vehicle for the formation of ice deposits on the intake screen. A review of previous corrective action documents revealed no similar occurrences of this kind.

NRC Form 388A 19-831 U.S. NUCLEAR REGULATORY COMMISSION APPROVEO OMB NO. 3160-0104 EXPIRES: 8/31 /86 FACILITY NAME 111 LICENSEE EVENT REPORT ILERI TEXT CONTINUATION OOCKET NUMBER 121 YEAR LER NUMBER 13)

SEQUENTIAL NUMBER REVISION NUMBER PAGE 141 Palisades Plant 0 I 5 I 0 I 0 I 0 I 2 I 5 I 5 9 14 -

0 I 0 11 -

0 I 0 0 ' I 4 OF 0 f CORRECTIVE ACTION-Corrective action for this event includes the following:

1.

Modify TSSP M0-33 to record control room pressures from one reading in 10 hours1.157407e-4 days <br />0.00278 hours <br />1.653439e-5 weeks <br />3.805e-6 months <br /> to 10 hourly readings. This will alert the operator of a possible decreasing trend in control room pressure and allow prompt

corrective action

2.

Modify the alarm response procedure (ARP) to instruct the operators to inspect the intake for bl-0ckage if control room pressure is low.

ADDITIONAL INFORMATION

None

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