United States Nuclear Regulatory Commission - Protecting People and the Environment


LICENSEE: WESTINGHOUSE ELECTRIC COMPANY      

SITE: WESTINGHOUSE ELECTRIC COMPANY         EN NUMBER:33542

DOCKET:                                  EVENT DATE: 01-15-98

RX TYPE:                                 EVENT TIME: 00:00

VENDORS:                                NOTIFY DATE: 01-15-98

EMERGENCY CLASS: N/A  REGION: 1 STATE: PA      TIME: 14:07

OPS OFFICER: BOB STRANSKY             

10 CFR SECTION: CCCC  21.21               UNSPECIFIED PARAGRAPH



10 CFR PART 21 REPORT REGARDING TESTING OF SOLID STATE PROTECTION

SYSTEM LOGIC                                                     

                                                                 

WESTINGHOUSE WAS RECENTLY NOTIFIED OF SOLID STATE PROTECTION     

SYSTEM (SSPS) CIRCUITS THAT WERE NOT FULLY TESTED DURING         

SEMI-AUTOMATIC TESTING OF THE SYSTEM. THE CIRCUITS NOT FULLY     

TESTED ARE THE FEEDWATER ISOLATION MEMORY CIRCUIT AND THE P-10   

SOURCE RANGE BLOCK MEMORY CIRCUIT. THESE CIRCUITS RELY ON        

PARALLELING EACH INPUT TO PROVIDE AN OUTPUT WITHOUT UTILIZING THE

RETENTIVE MEMORY. THE ORIGINAL TESTING ARRANGEMENT DID NOT VERIFY

THAT BOTH OF THE PARALLEL INPUTS ARE OPERATIONAL BECAUSE THE     

SIGNAL (E.G., P-4 FOR FEEDWATER ISOLATION) THAT INITIATES THE    

RETENTIVE MEMORY WAS PRESENT AT THE LOGIC GATE INPUT DURING      

TESTING. AN OPEN LOGIC INPUT ISOLATION DIODE MAY PREVENT THE     

DESIRED OUTPUT FROM THE LOGIC GATE.                              

                                                                 

FOR ALL PLANTS THAT UTILIZE THE SSPS, THIS LOGIC GATE INITIATES  

FEEDWATER ISOLATION ON A SAFETY INJECTION SIGNAL OR A HI-HI STEAM

GENERATOR WATER LEVEL SIGNAL. SAFETY INJECTION INITIATES A       

REACTOR TRIP AND, FOR MOST PLANTS, THE HI-HI STEAM GENERATOR     

WATER LEVEL INITIATES A TURBINE TRIP THROUGH SEPARATE LOGIC WHICH

LEADS TO A REACTOR TRIP. THESE FUNCTIONS PROVIDE A P-4 (REACTOR  

TRIP) SIGNAL SO FEEDWATER ISOLATION IS INITIATED WITH ONLY A     

SLIGHT DELAY (MILLISECONDS). FOR SEQUOYAH UNITS 1 AND 2 AND WATTS

BAR THE TURBINE TRIP SIGNAL FROM HI-HI STEAM GENERATOR WATER     

LEVEL IS NOT INITIATED SEPARATELY AND DEPENDS ON THE PROPER      

FUNCTIONING OF THE LOGIC GATE WITH PARALLEL INPUTS, AS DOES      

FEEDWATER ISOLATION. THE LACK OF FEEDWATER ISOLATION COULD LEAD  

TO WATER CARRYOVER INTO THE STEAM LINES FOR THESE PLANTS.        

                                                                 

THE SAME TYPE OF CIRCUIT IS USED FOR THE P-10 SOURCE RANGE BLOCK 

FUNCTION. THIS IS A BACK-UP FUNCTION TO P-6 AND IF BOTH OF THESE 

MALFUNCTIONED IT WOULD BE DETECTABLE BY OBSERVING THAT THE SOURCE

RANGE WAS NOT BLOCKED AS POWER INCREASED.                        

                                                                 

WESTINGHOUSE HAS DETERMINED THAT CIRCUIT MODIFICATIONS ARE NOT   

REQUIRED TO TEST BOTH PARALLEL INPUTS. BY PRESSING THE RESET     

SWITCH, THE RETENTIVE MEMORY SIGNAL (E.G., P-4 FOR FEEDWATER     

ISOLATION) IS DEFEATED AND THE ABILITY TO OBTAIN AN OUTPUT FROM  

THE LOGIC GATE CONFIRMS THAT BOTH INPUTS ARE FUNCTIONING.        

WESTINGHOUSE HAS COMMUNICATED THIS INFORMATION TO ALL PLANTS     

UTILIZING THE SSPS VIA TECHNICAL BULLETIN ESBU-TB-97-09, DATED   

DECEMBER 17, 1997.                                               





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