United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 88-06: Foreign Objects in Steam Generators

                                  UNITED STATES
                          NUCLEAR REGULATORY COMMISSION
                      OFFICE OF NUCLEAR REACTOR REGULATION 
                             WASHINGTON, D.C.  20555

                                February 29, 1988


INFORMATION NOTICE NO. 88-06:  FOREIGN OBJECTS IN STEAM GENERATORS


Addressees:

All holders of operating licenses or construction permits for pressurized 
water reactors (PWRs).

Purpose:

This information notice is being provided to alert addressees to a potentially 
generic problem with foreign objects on the secondary side of steam generators 
in PWRs and the potential for failure of steam generator tubes as a result of 
fretting.  It is expected that recipients will review the information for ap-
plicability to their facilities and consider actions, as appropriate, to pre-
clude similar problems from occurring at their facilities.  However, 
suggestions contained in this information notice do not constitute NRC 
requirements; therefore, no specific action or written response is required.

Description of Circumstances:

On February 3, 1988, during the first refueling outage at Catawba 2, the 
licensee submitted a report to the NRC, as required under 10 CFR 50.72, 
indicating that foreign metal objects in two of four steam generators had 
caused loss of 50% of the wall thickness for one tube in each of these steam 
generators.  One of the objects was a steel block 1-1/2 inches x 2 inches x 3 
inches and the other was a steel sliver approximately 1/4 inch x 3/8 inch x 8 
inches.  Both objects were located on the tube sheet.  On the basis of a 
subsequent evaluation, the licensee concluded that it was unlikely that these 
objects had caused damage.  However, the licensee found three jacking studs 2 
to 3 inches long by 2-1/4 inches in diameter on the tube sheet in one of the 
other two steam generators.  One of these studs did cause significant damage 
to a tube in that steam generator.  The licensee also found small gauge wire, 
a nail, a 6 inch piece of welding rod, and welding slag in the steam 
generators.  The licensee was able to remove all of the foreign objects and 
debris except for the piece of welding rod.  The licensee did eddy current 
testing of 100% of the peripheral tubes in all of the steam generators for 
Catawba 2 and found that plugging of seven tubes was necessary.  Of the seven 
tubes plugged, two had visible damage to the exterior surface near the tube 
sheet.  The maximum defect indicated by eddy current testing was 77%.

The licensee's records indicate that all of the steam generators were 
carefully inspected for foreign objects after fabrication of the steam 
generators was completed and prior to operation of the reactor at power.  
Nothing of significance 



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                                                            February 29, 1988 
                                                            Page 2 of 2 

was found at that time.  The foreign objects and debris found recently in the 
steam generators may have accumulated in the top works of the steam generators 
and may have been washed down to the tube sheet after preservice inspections.

Discussion:

As described in NUREG/CR-0718, "Steam Generator Tube Integrity Program Phase I
Report," tests for certain steam generators indicate that tube failure can be 
expected during normal operation if the tube wall thickness is reduced by 85% 
to 90% and if the defect is 1-inch long or longer.  Likewise, during a steam 
line break accident, failure can be expected if wall thickness is reduced by 
75% to 80%.

Information Notice 83-24, "Loose Parts in the Secondary Side of Steam 
Generators at Pressurized Water Reactors," addressed events involving foreign 
objects and loose parts on the secondary side of steam generators at PWRs, 
including the events at Ginna and Prairie Island 1 where tube ruptures were 
related to the presence of loose parts.  

Generic Letter 85-02, "Staff Recommended Actions Stemming from NRC Integrated 
Program for Resolution of Unresolved Safety Issues Regarding Steam Generator 
Tube Integrity," requested that PWR licensees perform visual inspections on 
steam generator secondary sides in the vicinity of the tube sheet along the 
entire periphery of the tube bundle and the tube lane to identify any foreign 
objects and damage to the external surfaces of tubes.  For licensees with 
operating licenses, these inspections were to be performed during the next 
planned outage for eddy current testing and after any secondary side repairs 
or modifications to steam generator internals were completed.  For applicants 
for operating licenses, these inspections were to be performed as part of the 
preservice inspection program.  The licensee for Catawba 2 complied with this 
request as an applicant for an operating license.  The preservice inspections 
would not detect foreign objects in the top works of the steam generators that
could be washed down to the tube sheets during the first fuel cycle. 

No specific action or written response is required by this information notice.
If you have questions about this matter, please contact the technical contact 
listed below or the Regional Administrator of the appropriate regional office.




                             Charles E. Rossi, Director
                             Division of Operational Events Assessment
                             Office of Nuclear Reactor Regulation

Technical Contact:  Roger Woodruff, NRR
                     (301) 492-1180

Attachment: List of Recently Issued NRC Information Notices 

.                                                            Attachment
                                                            IN 88-06 
                                                            February 29, 1988 
                                                            Page 1 of 1

                             LIST OF RECENTLY ISSUED
                            NRC INFORMATION NOTICES 
_____________________________________________________________________________
Information                                  Date of 
Notice No._____Subject_______________________Issuance_______Issued to________

88-05          Fire in Annunciator Control   2/11/88        All holders of OLs
               Cabinets                                     or CPs for nuclear
                                                            power reactors. 

88-04          Inadequate Qualification      2/5/88         All holders of OLs
               and Documentation of Fire                    or CPs for nuclear
               Barrier Penetration Seals                    power reactors. 

88-03          Cracks in Shroud Support      2/2/88         All holders of OLs
               Access Hole Cover Welds                      or CPs for BWRs. 

88-02          Lost or Stolen Gauges         2/2/88         All NRC licensees 
                                                            authorized to 
                                                            possess gauges 
                                                            under a specific 
                                                            or general 
                                                            license. 

88-01          Safety Injection Pipe         1/27/88        All holders of OLs
               Failure                                      or CPs for nuclear
                                                            power reactors. 

86-81,         Broken External Closure       1/11/88        All holders of OLs
Supp. 1        Springs on Atwood & Morrill                  or CPs for nuclear
               Main Steam Isolation Valves                  power reactors. 

87-67          Lessons Learned from          12/31/87       All holders of OLs
               Regional Inspections of                      or CPs for nuclear
               Licensee Actions in Response                 power reactors. 
               to IE Bulletin 80-11 

87-66          Inappropriate Application     12/31/87       All holders of OLs
               of Commercial-Grade                          or CPs for nuclear
               Components                                   power reactors. 

87-28,         Air Systems Problems at       12/28/87       All holders of OLs
Supp. 1        U.S. Light Water Reactors                    or CPs for nuclear
                                                            power reactors. 

87-65          Plant Operation Beyond        12/23/87       All holders of OLs
               Analyzed Conditions                          or CPs for nuclear
                                                            power reactors. 
_____________________________________________________________________________
OL = Operating License
CP = Construction Permit 
Page Last Reviewed/Updated Tuesday, November 12, 2013