United States Nuclear Regulatory Commission - Protecting People and the Environment

LICENSEE: COMMONWEALTH EDISON CO.
SITE: DRESDEN 2 EN NUMBER: 34963
DOCKET: EVENT DATE: 10-27-98
RX TYPE: BWR EVENT TIME: 13:45
VENDORS: GE-3 NOTIFY DATE: 10-27-98
EMERGENCY CLASS: N/A REGION: 3 STATE: IL TIME: 14:45
OPS OFFICER: JOHN MacKINNON
10 CFR SECTION: CCCC 21.21 UNSPECIFIED PARAGRAPH
UNIT CODE SCRAM RX CRIT INIT PWR INITIAL MODE CURR PWR CURRENT MODE
2 N Y 99 Power Operation 99 Power Operation

HIGH PRESSURE COOLANT INJECTION (HPCI) GLAND SEAL LEAK OFF (GSLO) LEVEL SWITCHES FAILURE.

THIS PART 21 WAS FACSIMILED TO THE NRC HEADQUARTERS OPERATION CENTER

"ON MAY 4, 1998, AT 0433 HOURS, WHILE PERFORMING DRESDEN OPERATING SURVEILLANCE (DOS) 2300-09, HPCI GSLO DRAIN PUMP AND CONDENSER HOTWELL LEVEL CONTROL FUNCTIONAL TEST, THE HOTWELL DRAIN PUMP EXHIBITED ERRATIC OPERATION AND RESULTED IN A HOTWELL LOW LEVEL. "

CAUSE OF THE EVENT

"THE ROOT CAUSE OF THIS EVENT WAS A MANUFACTURER DESIGN DEFICIENCY OF THE INSTALLED HPCI GSLO CONDENSER HOTWELL LEVEL CONTROL SWITCHES (NRC CAUSE CODE B). THE SWITCHES FAILED DUE TO A COMBINATION OF INSUFFICIENT MAGNET STRENGTH AND TOO MUCH TRAVEL IN THE FLOAT MECHANISM TO CONSISTENTLY ACTUATE THE FLOAT MICROSWITCH."

CORRECTIVE ACTIONS:

"THE UNIT 2 HPCI GSLO HOTWELL PUMP START/STOP LEVEL SWITCHES WERE REPLACED WITH OEM MODIFIED DESIGN SWITCHES, AND SATISFACTORILY TESTED.
"THE UNIT 3 HPCI GSLO HOTWELL PUMP START/STOP LEVEL SWITCHES WERE REPLACED WITH OEM MODIFIED DESIGN SWITCHES, AND SATISFACTORILY TESTED.
"THE PARTS REQUISITION SYSTEM (SI SYSTEM) WAS UPDATED TO SPECIFY THE MODIFIED OEM SWITCHES ENHANCED WITH STRONGER MAGNETS AND FLOAT STOPS."
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