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
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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
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