Part 21 Report - 1998-060
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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