United States Nuclear Regulatory Commission - Protecting People and the Environment

Information Notice No. 92-58: Uranium Hexafluoride Cylinders – Deviations in Coupling Welds

                                 UNITED STATES
                         NUCLEAR REGULATORY COMMISSION
                            WASHINGTON, D.C.  20555

                                August 12, 1992

                               IN COUPLING WELDS


All Fuel Cycle Licensees


The U.S. Nuclear Regulatory Commission is issuing this information notice to
alert addressees to a potential defect in the fabrication of uranium
hexafluoride cylinders manufactured by Trinity Industries, Inc.  It is
expected that recipients will review the information for applicability to
their facilities and consider actions, as appropriate, to address similar
problems.  However, suggestions contained in this information notice are not
NRC requirements; therefore, no specific action or written response is

Description of Circumstances

An NRC licensee recently discovered that the valve and plug couplings of model
48Y uranium hexafluoride cylinders manufactured by Trinity Industries, Inc.,
are attached by welds that are not full penetration welds, as called for in
the purchase order specification.  Due to thread damage, the licensee was
replacing a coupling, and while cutting through the existing weld, noted the
lack of full penetration.  The licensee had expected a full penetration weld
as shown in American National Standard, Packaging of Uranium Hexafluoride for
Transport (ANSI N14.1 - 1971, figure 9.)  After informing the NRC regional
office, the licensee cut the valve and plug coupling welds from three other
48Y cylinders manufactured by Trinity.  All six welds were found to be less
than full penetration.

The licensee then had a contractor perform ultrasonic tests of the coupling
welds on 15 48Y cylinders manufactured by Trinity.  The couplings on four of
these cylinders were removed to visually examine the welds and verify the
results of the ultrasonic testing.  The results showed that 11 of the 
15 cylinders had coupling welds lacking full penetration, and a twelfth showed
a full penetration weld with several small inclusions.  The visual
examinations of the removed couplings verified the results of the ultrasonic

The licensee possesses cylinders that were manufactured by Trinity from 1972
to 1976, and has not tested cylinders manufactured in any other time frame. 
Six of the cylinders tested were obtained by the licensee from other NRC
licensees or from Department of Energy facilities.


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                                                            August 12, 1992
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The Department of Transportation (DOT) regulations governing the packaging of
uranium hexafluoride for transport (10 CFR 173.420) require compliance with
either the ANSI N14.1 edition in effect at the time of manufacture or the ASME
Code, Section VIII, Division I, in effect at the time of manufacture, provided
the cylinder was manufactured on or before June 30, 1987.  The ANSI N14.1
standard suggests, but does not require, full penetration welds for the
couplings of 48Y cylinders.  The standard also allows the use of any ASME
code-approved joint detail providing that the alternate method meets with the
purchaser's approval.

The ASME code, Section VIII, Division I, Subsection B, Part UW-16(g), allows
for several methods of connecting fittings with internal threads that do not
use full penetration welds.  Although full penetration welds are not actually
required, Trinity has applied for an exemption from the DOT to allow the use
of the cylinders for transport of uranium hexafluoride.  However, the
licensee's purchase order specified full penetration welds, and Trinity does
not appear to be able to explain how the vessels were manufactured "out of
spec" or to what standard the welds were made.  This calls into question the
controls that were present during manufacture of the cylinders and
specifically the minimum coupling weld sizes.

Uranium hexafluoride cylinders with less than adequate valve and plug coupling
weld sizes, or other weld defects, could result in a release of uranium
hexafluoride when the cylinders are placed under pressure or involved in a
transportation incident.  However, the NRC is not aware of any reported
failures or releases associated with these welds.

Licensees may want to identify those uranium hexafluoride cylinders in their
inventory that were manufactured by Trinity Industries.  Licensees may also
want to consider taking steps to determine if these cylinders have valve and
plug coupling welds that deviate from their purchase order specifications, and
whether the weld sizes are adequate.  

The licensee possessing the cylinders with suspect welds has taken the
cylinders out of service.  The NRC is continuing an investigation of this
matter to further assess the scope of the problem, its safety significance,
and possible corrective action.  .

                                                            IN 92-58
                                                            August 12, 1992
                                                            Page 3 of 3

This information notice requires no specific action or written response.  If
you have any questions about the information in this notice, please contact
the technical contact listed below or the appropriate regional office.

                                    Richard E. Cunningham, Director
                                    Division of Industrial and
                                      Medical Nuclear Safety
                                    Office of Nuclear Material Safety 
                                      and Safeguards

Technical contact:  Thomas Wenck, NMSS
                    (301) 504-2404

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