United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 90-32: Supplement 1: Surface Crack and Subsurface Indications in the Weld of a Reactor Vessel Head

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

                                June 19, 1990


Information Notice No. 90-32, SUPPLEMENT 1:  SURFACE CRACK AND 
                                                 SUBSURFACE INDICATIONS IN 
                                                 THE WELD OF A REACTOR 
                                                 VESSEL HEAD


Addressees:

All holders of operating licenses or construction permits for nuclear power 
reactors.

Purpose:

This information notice supplement is intended to update the information 
previously provided in Information Notice No. 90-32.  It is expected 
that recipients will review this information for applicability to their 
facilities and consider actions, as appropriate, to avoid similar problems.  
However, suggestions contained in this information notice do not constitute 
NRC requirements; therefore, no specific action or written response is 
required.

Description of Circumstances:

In April 1990, during the refueling outage at the James A. FitzPatrick 
Nuclear Power Plant, the licensee found a group of four subsurface 
indications in the reactor vessel head as a result of performing an 
ultrasonic inservice inspection from the outside of the vessel head.  The 
preliminary sizing indicated that the subsurface indications have a total 
length of 12 inches, and a maximum depth of 2 inches (50 percent through 
wall).  The licensee also observed a surface indication measuring 1 inch in 
length on the inside surface of the head in the general area of the 
subsurface indications and confirmed this observation by liquid penetrant 
examination (PT).  The licensee reported the surface indication and 
subsurface indications to be located in the circular dollar plate weld at 
the top of the vessel head.  NRC issued Information Notice No. 90-32 on May 
3, 1990, to report this event.  Subsequently, the licensee performed the 
following additional examinations to further characterize the indications: 

1.   Ultrasonic examination (UT) from the outside surface using automatic 
     mode,

2.   Ultrasonic sizing of the indications from both inside and outside 
     surfaces including the use of refracted longitudinal waves,

3.   Radiographic examinations from the inside of the head,



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                                                  IN 90-32, Supplement 1
                                                  June 19, 1990
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4.   Examination of radiographic films with an enhanced technique, and

5.   Magnetic particle examination (MT) on the inside head surface.

The results of these additional examinations indicate that the subsurface 
indications are not cracks, but original fabrication flaws such as slag or 
inclusions, and are not connected to the surface.  The previously reported 
surface indication appears to be a very shallow surface scar that was 
removed during surface preparation for MT.

Discussion:

When performing nondestructive examinations and determining the real 
significance of reflector indications from within any metal, experience and 
knowledge in the various advanced inspection techniques used in performing 
surface and volumetric examinations and in flaw discrimination are 
important.  In performing its initial assessment, the licensee interpreted 
the combination of the surface indication and the multiple subsurface 
reflections as a very large flaw.  Subsequent additional examinations to 
better characterize the surface and subsurface indications have concluded 
that the multiple reflections were caused by a combination of inclusions in 
the material, a proximate surface scar and subsurface slag.  The licensee's 
reactor vessel vendor, the General Electric Company (GE), has confirmed this 
current assessment.  GE, using a test sample of equivalent material to the 
FitzPatrick reactor vessel head, duplicated ultrasonically the multiple 
reflections from inclusions in the material.  The licensee has concluded 
that the surface indication was not a crack, but a very shallow surface 
scar, and that the subsurface indications are not cracks, but original 
fabrication flaws, such as slag and inclusions, that are not connected to 
the surface.

This information notice requires no specific action or written response.  If 
you have any questions about the information in this notice, please contact 
one of the technical contacts listed below or the appropriate NRR project 
manager.




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

Technical Contacts:  William H. Koo, NRR
                     (301) 492-0706

                     Robert H. Hermann, NRR
                     (301) 492-0768

Attachment:  List of Recently Issued NRC Information Notices 
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