Protecting People and the EnvironmentUNITED STATES NUCLEAR REGULATORY COMMISSION
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
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