United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 90-32: 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

                                 May 3, 1990


Information Notice No. 90-32:  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 is intended to alert addressees to a potential 
problem related to cracks found in the weld of a reactor vessel head.  It is 
expected that recipients will review the 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, while the James A. Fitzpatrick Nuclear Power Plant was shut 
down for refueling, the licensee found a surface crack and some subsurface 
indications in the reactor vessel head while performing routine inservice 
inspections.  The crack and subsurface indications are circumferentially 
oriented and located in the weld that joins the circular upper head portion 
(dollar plate) to the curved trapezoidal portions (meridian plate) of the 
head.  The dollar plate is located at the top of the vessel head.  The 
licensee observed a crack measuring 1 inch long on the inside surface of the 
head and confirmed the observation by surface examination.  A group of 4 
subsurface indications in the general area of the surface crack has a length 
of 12 inches, and a maximum depth of 2 inches (50 percent through wall).  
The licensee found and measured subsurface indications using ultrasonic 
examination methods.  The licensee plans to take some metallurgical samples 
from the cracked area to determine the mode and mechanism of the defects.

Discussion:

This is the second recent incident in which cracks have been observed in a 
reactor vessel head.  The first incident occurred at Quad Cities Station, 
Unit 2.  As a result, on April 23, 1990, the General Electric Company issued 
RICSIL No. 050, "Reactor Pressure Vessel Head Clad Cracking."  On April 30, 
the NRC issued Information Notice No. 90-29, "Cracking of Cladding and Its 




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                                                                 IN 90-32 
                                                                 May 3, 1990
                                                                 Page 2 of 2


Heat-Affected Zone in the Base Metal of a Reactor Vessel Head."  These 
documents discussed the cracking of the stainless steel cladding and its 
heat-affected zone in the base metal of the reactor vessel head at the Quad 
Cities facility.  However, at Fitzpatrick, the reactor vessel head has no 
cladding, and the crack and subsurface indications are in the weld.

The information provided in this information notice is preliminary.  When 
more information becomes available, a supplement will be issued if 
appropriate.

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) 492-0928

                     T. Greene, NRR
                     (301) 492-1176

Attachment:  List of Recently Issued NRC Information Notices 
.ENDEND
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