United States Nuclear Regulatory Commission - Protecting People and the Environment


LICENSEE: ILLINOIS POWER CO.                 

SITE: CLINTON 1                             EN NUMBER:34548

DOCKET: 05000461                         EVENT DATE: 07-20-98

RX TYPE: BWR                             EVENT TIME: 00:00

VENDORS: GE-6                           NOTIFY DATE: 07-21-98

EMERGENCY CLASS: N/A  REGION: 3 STATE: IL      TIME: 09:19

OPS OFFICER: DICK JOLLIFFE            

10 CFR SECTION: CCCC  21.21               UNSPECIFIED PARAGRAPH

UNIT  SCRAM   RX   INIT  INITIAL MODE     CURR   CURRENT MODE

      CODE   CRIT  PWR                    PWR

 1    N       N      0   COLD SHUTDOWN      0   COLD SHUTDOWN  



10-CFR-PART-21 REPORT - SHRINKAGE AND CRACKING OF MEDIUM AND HIGH

DENSITY SILICONE PENETRATION SEALS DUE TO COEFFICIENT OF THERMAL 

EXPANSION                                                        

                                                                 

ON 02/20/98, WHILE PERFORMING A WALKDOWN TO QUALIFY PENETRATION  

SEALS IN ACCORDANCE WITH NUREG 1552, "FIRE PENETRATION SEALS IN  

NUCLEAR POWER PLANTS," ILLINOIS POWER (IP) IDENTIFIED CRACKS IN  

PENETRATION SEAL DG-762-01-5003.  THE CRACKS EXTENDED COMPLETELY 

THROUGH THE SEAL IN THE M-BOARD SEPARATOR MATERIAL AT THE        

INTERFACE BETWEEN THE M-BOARD AND THE SF-60 SEALANT AND BETWEEN  

THE SF-60 SEALANT AND A PIPE PASSING THROUGH THE SEAL.  THE      

M-BOARD IS A REFRACTORY FIBER BOARD MADE PREDOMINANTLY OF ALUMINA

SILICA USED WITHIN THE PENETRATION SEAL TO DIVIDE A PENETRATION  

INTO SECTIONS FOR WHICH A TESTED DESIGN CONFIGURATION CAN BE     

APPLIED.  THE SEAL WAS DESIGNED AND INSTALLED BY BISCO, A        

SUBSIDIARY OF THE BRAND COMPANIES, IN PARK RIDGE, ILLINOIS.  (THE

BISCO ORGANIZATION NO LONGER EXISTS.)  THE BISCO SF-60 SEALANT   

MATERIAL WAS MANUFACTURED BY DOW CORNING AS SYLGARD 170 (BISCO   

SF-60 AND BISCO SF-150NH) MATERIAL.                              

                                                                 

INSPECTIONS OF OTHER SIMILAR PENETRATION SEAL CONFIGURATIONS     

REVEALED THAT THE SHRINKAGE ISSUE IS A GENERIC CONCERN FOR MEDIUM

AND HIGH DENSITY PENETRATION SEALS THAT HAVE CONFIGURATIONS WITH 

DIMENSIONS GREATER THAN 12 INCHES.  THE CRACKS ARE ATTRIBUTED TO 

SHRINKAGE DUE TO THE VOLUME COEFFICIENT OF THERMAL EXPANSION OF  

THE CURED MATERIAL (APPROXIMATELY 8% FOR EACH 100�C OF           

TEMPERATURE DIFFERENTIAL).  CLINTON POWER STATION HAS            

APPROXIMATELY 800 SEALS THAT MAY BE SUSCEPTIBLE TO THIS          

SHRINKAGE.  AS OF 07/10/98, IP HAD INSPECTED 157 OF THE SUSPECTED

PENETRATION SEALS AND FOUND UNACCEPTABLE CRACKS/GAPS IN 32       

PENETRATIONS.                                                    

                                                                 

IP PLANS TO INSPECT AND REWORK/REPAIR THE SUSPECTED PENETRATION  

SEALS AS NECESSARY.  RESOLUTION OF THIS ISSUE IS CURRENTLY       

SCHEDULED TO BE COMPLETED BY MAY 1999.                           

                                                                 

THE LICENSEE HAS NOTIFIED THE NRC RESIDENT INSPECTOR.            



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