Part 21 Report - 1998-540

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.

Page Last Reviewed/Updated Friday, January 31, 2020