United States Nuclear Regulatory Commission - Protecting People and the Environment


LICENSEE: NORTHEAST UTILITIES                

SITE: MILLSTONE 1                           EN NUMBER:34615

DOCKET: 05000245                         EVENT DATE: 08-07-98

RX TYPE: BWR                             EVENT TIME: 12:00

VENDORS: GE-3                           NOTIFY DATE: 08-07-98

EMERGENCY CLASS: N/A  REGION: 1 STATE: CT      TIME: 16:16

OPS OFFICER: DICK JOLLIFFE            

10 CFR SECTION: CDEG  21.21(c)(3)(i)      DEFECTS/NONCOMPLIANCE

UNIT  SCRAM   RX   INIT  INITIAL MODE     CURR   CURRENT MODE

      CODE   CRIT  PWR                    PWR

 1    N       N      0   REFUELING          0   REFUELING      



- 10CFR21 REPORT - DEFECTIVE GAS TURBINE GENERATOR TACHOMETER    

TRANSDUCER                                                       

                                                                 

MILLSTONE UNIT 1 USES ONE DIESEL GENERATOR AND ONE GAS TURBINE   

GENERATOR (GTG) FOR DEDICATED EMERGENCY POWER TO VITAL AC BUSES  

DURING AN EVENT.                                                 

                                                                 

THE GTG IS A GE LM-1500 GENERATOR THAT UTILIZES TACHOMETER       

TRANSDUCERS (TTs) TO PROVIDE THE GOVERNOR WITH THE SPEED SIGNALS 

FROM THE GTG AND THE DIESEL GENERATOR.  ONE OF THESE TTs THAT WAS

ACCEPTED FROM EITEL MANUFACTURING COMPANY, CAPISTRANO BEACH, CA, 

(BERKELEY MODEL #466-120)                                        

WAS LATER DETERMINED TO HAVE THE FINGER SPRING WASHER INSTALLED  

IN THE INCORRECT ORIENTATION IN THE TT RESULTING IN AN IMPROPER  

FIT OF THE BEARINGS.  BEARING FAILURE WOULD INCREASE VIBRATION IN

THE TT ASSEMBLY POSSIBLY RESULTING IN EARLY FAILURE OF THE       

WINDINGS, OR SEIZURE AND                                         

BREAKAGE OF THE SHAFT.  EITHER FAILURE WOULD RESULT IN A LOSS OF 

SPEED                                                            

SIGNAL TO THE GOVERNOR.                                          

                                                                 

THIS TT PROVIDES AN OVERSPEED SIGNAL TO THE GOVERNOR.  A TRIP IS 

INITIATED IF THE SIGNAL IS LOST.  IN THE EVENT THAT THE GTG IS   

OPERATING IN AN EMERGENCY, WITH AN ACCIDENT SIGNAL PRESENT, THE  

TRIP IS BYPASSED.                                                

                                                                 

THESE TTs ARE PRODUCED COMMERCIALLY AND ARE DEDICATED FOR THIS   

SAFETY RELATED APPLICATION BY MILLSTONE.  THE TT WITH THE DEFECT 

WAS ACCEPTED                                                     

AND INSTALLED IN ID LOCATION TG-25-5.                            

                                                                 

THE DEFECTIVE TT INSTALLED IN LOCATION TG-25-5 IS COUPLED        

TOGETHER ON THE SAME DRIVE MECHANISM WITH A TT OF THE SAME DESIGN

INSTALLED IN LOCATION TG-25-1.  THE SIGNAL FROM THE TT INSTALLED 

IN LOCATION TG-25-1 PROVIDES                                     

THE FEEDBACK TO THE GOVERNOR FOR SPEED CONTROL OF THE ELECTRIC   

GENERATOR. WITHOUT THIS SPEED SIGNAL, THE GOVERNOR CANNOT CONTROL

THE FREQUENCY OF                                                 

THE GENERATOR WHICH WOULD PREVENT SYNCHRONIZATION TO THE VITAL AC

BUSES. FAILURE OF THE TT INSTALLED IN LOCATION TG-25-5 COULD HAVE

CAUSED THE FAILURE OF THE TT INSTALLED IN LOCATION TG-25-1,      

RENDERING THE GTG UNAVAILABLE TO MITIGATE THE CONSEQUENCES OF AN 

ACCIDENT. IN THIS SITUATION, THE GTG WOULD NOT BE ABLE TO PERFORM

ITS SAFETY FUNCTION.                                             

                                                                 

THE LICENSEE IS CONTINUING TO INVESTIGATE THIS CONDITION AND IS  

DETERMINING CORRECTIVE ACTIONS.                                  

                                                                 

THE LICENSEE INFORMED THE NRC RESIDENT INSPECTOR.                



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