Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
LICENSEE: ILLINOIS POWER CO.
SITE: CLINTON 1 EN NUMBER:31477
DOCKET: 05000461 EVENT DATE: 12-17-96
RX TYPE: BWR EVENT TIME: 14:30
VENDORS: GE-6 NOTIFY DATE: 12-18-96
EMERGENCY CLASS: N/A REGION: 3 STATE: IL TIME: 15:15
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 REFUELING 0 REFUELING
-CRD SYSTEM INOP DUE TO INCORRECT TORQUE VALUE OF CRD HCU HOLD
DOWN BOLTS-
ON 11/19/96, WITH THE PLANT IN A REFUELING OUTAGE, THE LICENSEE
IDENTIFIED THAT THE TORQUE VALUES SPECIFIED BY GENERAL ELECTRIC
FOR THE 3/8-INCH HOLD DOWN BOLTS FOR THE CONTROL ROD DRIVE (CRD)
HYDRAULIC CONTROL UNITS (HCUs) EXCEEDED THE MINIMUM YIELD
STRENGTH OF THE BOLT MATERIAL. THIS CAUSED THE CRD HCUs TO BE
INOPERABLE BECAUSE THE TORQUE VALUE DID NOT MEET SEISMIC
QUALIFICATION REQUIREMENTS FOR RESTRAINING THE CRD HCUs DURING A
DESIGN BASIS EARTHQUAKE. THE CRD HCU OPERATION WOULD ONLY BE
AFFECTED IF A SEISMIC EVENT WERE TO OCCUR DURING PLANT OPERATION.
THERE ARE SEVEN 3/8-INCH BOLTS IN EACH OF THE 145 CRD HCUs FOR A
TOTAL OF 1015 BOLTS. THESE BOLTS ATTACH THE GENERAL ELECTRIC
SUPPLIED CRD HCUs TO STRUCTURAL STEEL SUPPORTS IN THE CONTAINMENT
BUILDING WHICH WERE DESIGNED BY SARGENT AND LUNDY ENGINEERING,
THE ARCHITECT ENGINEER FOR THE CONSTRUCTION OF THE POWER STATION.
THIS CONDITION HAS EXISTED SINCE INITIAL LICENSING OF THE PLANT
IN 1987.
ALL OF THE 3/8-INCH CRD HCU HOLD DOWN BOLTS HAVE BEEN REPLACED
WITH NEW BOLTS AND RETORQUED TO THE PROPER VALUE. A SAMPLE OF
THE 3/8-INCH BOLTS THAT WERE REMOVED FROM THE CRD HCUs WILL BE
TESTED TO DETERMINE WHETHER OR NOT THEY WOULD HAVE BEEN ABLE TO
WITHSTAND A DESIGN BASIS EARTHQUAKE WHILE INSTALLED ON THE CRD
HCUs.
THIS 10 CFR PART 21 REPORT ONLY APPLIES TO THE CLINTON POWER
STATION.
IN ADDITION, THE LICENSEE HAS SUBMITTED LER #96-018 AND HAS
INFORMED THE NRC RESIDENT INSPECTOR.
