United States Nuclear Regulatory Commission - Protecting People and the Environment

LICENSEE: COMMONWEALTH EDISON CO.            
SITE: DRESDEN 2 3                           EN NUMBER:28285
DOCKET:  05000237 05000249               EVENT DATE: 01-26-95
RX TYPE:  BWR BWR                        EVENT TIME: 15:45
VENDORS:  GE-3 GE-3                     NOTIFY DATE: 01-26-95
EMERGENCY CLASS: N/A  REGION: 3 STATE: IL      TIME: 17:43
OPS OFFICER: TIM McGINTY              
10 CFR SECTION: ADEG  50.72(b)(1)(ii)     DEGRAD COND DURING OP
UNIT  SCRAM   RX   INIT  INITIAL MODE     CURR   CURRENT MODE
      CODE   CRIT  PWR                    PWR
 2    N       Y     99   POWER OPERATION   99   POWER OPERATION
 3    N       Y     99   POWER OPERATION   99   POWER OPERATION

TIP SYSTEM ISOLATION VALVES WOULD RE-OPEN IF THE CONTROL SWITCHES
WERE IN THE OPEN POSITION WHEN A GROUP 2 ISOLATION SIGNAL WAS    
RESET.                                                           
                                                                 
THE SYSTEM ENGINEERING DEPARTMENT REPORTED THAT A REVIEW OF THE  
TRAVERSING IN-CORE PROBE (TIP) SYSTEM ISOLATION LOGIC PRINTS     
INDICATED THAT DRESDEN STATION HAS THE SAME DESIGN DEFICIENCY    
EXPERIENCED AT QUAD CITIES AND COOPER (SEE RELATED EVENT REPORTS 
28281 & 28245, RESPECTIVELY).  THIS DEFICIENCY WOULD ALLOW THE   
TIP SYSTEM ISOLATION VALVES TO AUTO RE-OPEN UPON RESET OF A GROUP
2 PRIMARY CONTAINMENT ISOLATION IF THE CONTROL SWITCHES ARE NOT  
LEFT IN THE "CLOSED" POSITION.                                   
                                                                 
DRESDEN STATIONS UPDATED REVISED FSAR STATES THAT THE ISOLATION  
LOGIC HAS BEEN MODIFIED TO PREVENT THE VALVES FROM AUTOMATICALLY 
OPENING WHEN THE ISOLATION SIGNAL IS RESET. THE PRINT REVIEW     
INDICATES THAT THE TIP SYSTEM ISOLATION VALVES WERE NOT INCLUDED 
IN THIS MODIFICATION, AND ARE THEREFORE OUTSIDE THE DESIGN BASES.
 ADMINISTRATIVE CONTROLS HAVE BEEN PLACED IN EFFECT TO ENSURE    
THAT TIP SYSTEM ISOLATION VALVE CONTROL SWITCHES ARE IN THE      
CLOSED POSITION, AND VALVES ARE VERIFIED CLOSED PRIOR TO RESET OF
ANY GROUP 2 PRIMARY CONTAINMENT ISOLATION.  THE LICENSEE WILL BE 
INVESTIGATING LONG-TERM CORRECTIVE ACTIONS, AND WILL INFORM THE  
RESIDENT INSPECTOR.                                              

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